Release 26.3.0.1 with live Reborn views and random page policies

README.md

@@ -10,17 +10,19 @@ also lets you author modern terrain, biomes, structures, seasons, and celestial
 bodies. It is an independently developed project, not a byte-for-byte copy of
 the 1.12.2 mod.
 
-The gameplay guide below describes the **Minecraft 1.21.1 release**. A separate,
-incomplete **Minecraft 26.3 beta** is available: Java 25, NeoForge 26.3.0.99,
-and a first-party Age backend (no Dynamic Dimensions or Bad Packets). It now
-supports authored terrain/biomes, structure and vegetation pages, independent
-Age weather/lighting, seeded and colorable Overworld/Nether/End/Static skies,
-independent Sun/Moon controls, multiple bodies and eclipses, seeded biome and
-feature completion, and random structure selection. Nether/End noise-biome
-materials now follow their native rules. The beta does not yet provide full
-1.21.1 gameplay or optional-integration parity.
-See the [26.3 beta guide](ports/mc263/README.md) and
-[latest beta release notes](ports/mc263/RELEASE_NOTES_1.0.1.93-beta.1.md).
+The gameplay guide below describes the **Minecraft 1.21.1 release**. The separate
+**Minecraft 26.3 release, 26.3.0.1**, uses Java 25, NeoForge 26.3.0.99 and a
+first-party Age backend; it does not need Dynamic Dimensions or Bad Packets.
+It includes authored/seeded Ages, writing stations and collections, libraries,
+crystal portals, celestials/eclipses, instability and Link Modifier controls.
+JEI, TerraBlender/Biomes O' Plenty, Serene Seasons and Ruins remain optional.
+Immersive Portals Reborn 7.0.12 adds live book previews and crystal portal views;
+animated fallbacks work without it. Random-page eligibility and random-Age glyph
+descriptions are included. Full 1.21.1 parity and the final expanded-catalog
+two-client regression remain ongoing. Reborn's Static Sky rendering bug is tracked
+in [#116](https://git.paddedcell.org/dnorberg/rivencraft/issues/116).
+See the [26.3 guide](ports/mc263/README.md) and
+[release notes](ports/mc263/RELEASE_NOTES_26.3.0.1.md).
 Keep the builds and their saves separate, and back up worlds before updating.
 
 ## Getting started
@@ -123,8 +125,10 @@ checks from manual evidence and known limitations.
 
 The JAR is written to `build/libs/`. Development runs need the required mods;
 see [GameTest guidance](docs/GAMETESTS.md) for focused archived suites.
-Versions use `x.y.z.b`: major release, completed milestone, release slice,
-then fixes/additional work within that slice.
+New versions prefix the Minecraft version, followed by the milestone/release
+slice and fixes/additional-work iteration. For example, `26.3.0.1` produces
+`rivencraft-26.3.0.1.jar`. Existing 1.21.1 artifacts keep their published legacy
+numbers until that line's next code release. See the [release workflow](docs/DUAL_VERSION_RELEASE.md).
 
 Rivencraft is licensed under LGPL-3.0-or-later. Legacy-derived material is
 credited in [NOTICE](NOTICE) and [asset provenance](docs/ASSET_PROVENANCE.md).

docs/DUAL_VERSION_RELEASE.md

@@ -0,0 +1,53 @@
+# Dual-version release workflow
+
+Maintain Minecraft 1.21.1 and 26.3 independently. The 1.21.1 line retains Dynamic
+Dimensions AR Edition and Bad Packets. The 26.3 line uses its first-party backend.
+Do not widen either artifact's Minecraft dependency range or import saves between
+the tracks.
+
+## Version identity
+
+From 26.3.0.1 onward, prefix the Minecraft version and append the milestone/release
+slice and iteration: Minecraft.release-slice.iteration. Example:
+`26.3.0.1` -> `rivencraft-26.3.0.1.jar`, Gitea tag `V26.3.0.1`.
+An explicitly selected prerelease uses a suffix such as `-beta.1`.
+The existing 1.21.1 release keeps its published version until its next code update;
+then use the corresponding `1.21.1.<slice>.<iteration>` convention.
+
+The user authorized regular release status for 26.3.0.1. Release-channel status
+does not close unfinished parity or multiplayer issues automatically.
+
+## Build and publish
+
+For 26.3, update `ports/mc263/gradle.properties`, then run
+`./gradlew -p ports/mc263 build --console=plain` with Java 25 available.
+Use the exact built/player-validated artifact; naming/metadata-only changes do
+not change generation or save behavior.
+
+Write release notes, audit the guide/wiki/project description, commit and push
+the changes, then create and push the matching annotated tag. Preview the
+`scripts/publish_mod_sites.py release` command with the JAR, changelog, version,
+display name, Minecraft version, Java version and channel; add `--publish` to
+upload to Gitea, Modrinth and CurseForge. Tokens stay in the system keyring.
+Verify published metadata and downloaded artifact hashes. CurseForge approval
+may remain pending after a successful upload.
+
+The publisher accepts legacy Minecraft-prefixed archive filenames and beta tags
+for already numbered historical uploads; new releases use the identity above.
+
+## Validation gates and issue audit
+
+Run appropriate builds and targeted server checks for changed behavior. The user
+performs visual/gameplay validation. Keep temporary test fixtures out of shipped
+JARs; use new worlds and remove them regardless of pass/fail. Stop test processes.
+If generation stalls, hand the test to the user.
+
+Before closing a port umbrella issue, compare its acceptance criteria and comments
+to actual evidence. Current expanded-catalog two-client create/travel/reconnect/
+restart/stale-ack regression remains in #100. #103 retains dual-line release
+automation/regression completion and #104 retains the full parity gate.
+Shared issues need both versions resolved before closure.
+
+For each release, document tested optional versions and no-optional fallbacks,
+match client/server JARs, preserve the independent 1.21.1 support line, update wiki
+and platform descriptions, and keep known bugs linked in the release notes.

gradle.properties

@@ -35,7 +35,7 @@ mod_id=rivencraft
 mod_name=Rivencraft
 # The license of the mod. Review your options at https://choosealicense.com/. All Rights Reserved is the default.
 mod_license=LGPL-3.0-or-later
-# The mod version. Rivencraft uses the x.y.z.b policy documented in README.md.
+# Existing 1.21.1 release number. Adopt the Minecraft-prefixed policy in README.md on its next code release.
 mod_version=1.0.1.1
 immersive_portals_version=6.0.7
 terrablender_version=4.1.0.8

ports/mc263/RELEASE_NOTES_1.0.1.106-beta.1.md

@@ -0,0 +1,85 @@
+# Rivencraft 26.3 beta 1.0.1.106-beta.1
+
+Collects the player-validated port slices .99–.106 since 1.0.1.98-beta.1.
+This beta is not yet feature-complete with Minecraft 1.21.1.
+
+## Books and travel
+
+- Fallback Age platforms now use the dedicated non-collectible platform block
+  from 1.21.1: opaque crystal texture, glass-like breaking strength, no drops
+  or pick-block item. Existing ordinary Crystal Block platforms are unchanged.
+- Ported automatic Return Links for successful handheld Descriptive Book
+  travel. `descriptive_books.return_link_mode` in `config/rivencraft-local.toml`
+  defaults to **DISABLED**. `ON_CREATION` issues one on the first arrival per
+  Age/world with that mode enabled; `ALWAYS` issues one on each arrival.
+- Return Links preserve departure dimension, position and facing. They are
+  issued after Disarm and drop at the destination if inventory is full.
+  First-arrival records persist across reload, reseeding and restart.
+- Successful handheld Linking and Descriptive Book travel now leaves the
+  active book at departure as a recoverable open-book entity. Both hands are
+  supported. Failed travel or canceled entity spawning restores the book.
+- Dropped books reuse the existing textures and skyward-facing model. They
+  have a one-second pickup delay, no ordinary five-minute expiry, slow decay
+  and water/rain damage, matching 1.21.1. Their components and decay counter
+  persist through restart.
+
+## Page collections and binding
+
+- Ported Notebooks and Collation Folders with their existing editor and assets,
+  capacities of 252 and 27 positions, sparse page storage, search, scrolling,
+  page movement and inventory transfers. Link Panels are rejected by the editor.
+- Notebook crafting uses the existing leather/string pattern. The held
+  collection is locked against ordinary menu movement. Escape closes the menu
+  with search focused; search still consumes inventory/hotbar shortcuts.
+- Corrected the port's keyboard and mouse-button mappings, including arrow
+  movement, right-click handling and scrollbar dragging.
+- The Book Binder accepts collection imports: shift-click to append pages or
+  click a carried collection on the strip to insert them. Empty positions are
+  skipped and occupied page order is retained. Imports validate all inputs and
+  capacity before committing; successful imports return the empty collection.
+- Added category Symbol Portfolios to Creative, including registry-derived
+  biome, material and fluid pages. Large categories split into volumes of up
+  to 252 pages. Portfolios use the editor and Binder import flow.
+- Sealed Notebooks open into Folders containing 16 random pages using the
+  1.21.1 pool/exclusions. Survival consumes one; Creative retains the item.
+  Full inventories receive a dropped Folder. No new recipes are invented for
+  Folders, Portfolios or Sealed Notebooks; discovery/library loot is pending.
+
+## Writing Desk
+
+- Ported the two-block Writing Desk, its existing model/textures, selected-page
+  and white paper-stack display, and Legacy GUI atlases.
+- Ported 88 tabs cycled four at a time, category/search/sort/ALL views, collection
+  and loose-page storage, page movement/extraction, and server-owned catalog
+  synchronization. Link Panels cannot be stored or copied in the desk.
+- Copy previews are virtual. Taking a copy consumes one paper and one ink by
+  default while retaining the original page. `writing.symbol_ink_cost` is
+  configurable in `rivencraft-local.toml`.
+- Vials fill a 16-unit meter and return vanilla glass bottles. Refills are
+  event-driven and require bottle space. Full inventory prevents shift-copy
+  consumption. Unknown pages are retained but cannot be copied unresolved.
+- Ported crafting and adapted its recipe-unlock advancement to 26.3.
+  Removing either desk half removes its partner and drops contents once.
+- Further corrections to the desk model, focused on page/paper placement,
+  remain tracked for both versions in issue #113.
+
+## Compatibility and validation
+
+- Requires Minecraft **26.3**, NeoForge **26.3.0.99**, and **Java 25**. Dynamic
+  Dimensions and Bad Packets are not required. The 1.21.1 implementation is
+  unchanged. Use matching client/server builds; Age catalog protocol remains 10.
+- Player in-game checks passed. Both build targets passed. Targeted disposable
+  server fixtures covered ownership recovery, collection/copy transactions,
+  save/network codecs, block removal, reload/reseed and restart persistence.
+  Servers were stopped and test worlds removed. This was not a full GameTest run.
+- Full writing recovery, remaining discovery/stations, instability, crystal
+  portals, progression awards and optional integration parity remain unfinished.
+  JEI guides and discovery loot for the newly ported interactions are pending.
+  Unsupported effects remain marked red; Creative availability is not parity.
+- Back up saves. New Native Cave profiles from .97 onward cannot be read by
+  earlier betas, and newly ported items/entities also require the newer build.
+  Keep 1.21.1 and 26.3 saves separate. Machine acceleration (#112) and Native
+  Cave default biome-pool policy (#111) remain separate planned work.
+
+Report issues and help improve the wiki at
+[BlackSheep Git](https://git.paddedcell.org/dnorberg/rivencraft).

ports/mc263/RELEASE_NOTES_1.0.1.115-beta.1.md

@@ -0,0 +1,88 @@
+# Rivencraft 26.3 beta 1.0.1.115-beta.1
+
+Collects the player-validated port slices .107–.115 since 1.0.1.106-beta.1.
+Minecraft 26.3, NeoForge 26.3.0.99 and Java 25. This remains a beta with
+incomplete Minecraft 1.21.1 gameplay and optional-integration parity.
+
+## Book stands and dropped books
+
+- Place a Linking Book, Descriptive Book or Page on an empty vanilla lectern
+  to convert it into a Rivencraft book stand, preserving facing. Occupied
+  vanilla lecterns are left alone.
+- Books use the existing open-book model and textures and show their name
+  above the stand. Pages use their item artwork without a hover label,
+  retaining the 1.21.1 orientation corrections.
+- Open a bound book with an empty hand, then click its destination panel to
+  travel while leaving the book on its stand. Existing link modifiers,
+  same-dimension rules, Return Link configuration and Age-entry awards apply.
+- Shift-right-click with an empty hand retrieves the stored item and restores
+  a vanilla lectern. Breaking returns one lectern and its contents. Unwritten
+  books can be displayed; retrieve them to bind in hand in this beta.
+- Ordinary dropped Linking/Descriptive Books now become recoverable open-book
+  entities, including unwritten books, inventory/player drops, container and
+  stand drops, death/Disarm drops and ordinary book entities loaded from disk.
+- Conversion preserves the stack and components, position, motion, facing,
+  pickup delay and ownership/thrower metadata. It uses the existing open-book
+  lifetime, slow decay and water/rain behavior. Already-custom books and
+  non-book items are skipped.
+- Conversion runs after registration without world scans or force-loading.
+  The original is removed only after replacement succeeds; a canceled
+  replacement leaves the ordinary item intact and eligible on a later reload.
+- Stand travel validates source dimension, distance, loaded chunk and the exact
+  currently stored book, rejecting stale screens after removal/replacement.
+
+## Book GUIs and names
+
+- Descriptive Books reuse the Legacy gilded cover, name/author front spread,
+  and one authored symbol at a time on following right-hand pages. Saved page
+  order and repetitions are retained, with runtime glyphs and no extra item outline.
+- New Descriptive Books record their author server-side. Older books without
+  that metadata use the unknown-author label.
+- Linking Books use the plain Legacy cover, wrapped title, destination name
+  and block coordinates, plus the blank final spread. Return Links suppress
+  the redundant title. Bottom corners or arrow keys turn pages with sound.
+- Both GUIs share the Legacy artwork/text/counter/corner helpers. Naming
+  controls hide on later pages and remain correct after resizing. Escape closes
+  even with naming focused; normal text input does not trigger inventory keys.
+- Ported the existing 1.21.1 fallback's animated teal spiral panel to both GUIs,
+  including lecterns. Removed placeholder labels. The Legacy frame draws over
+  the animation; travel is active only on the front panel.
+- The animated fallback is not a live destination view. Destination tint,
+  snapshot renderer integrations and random-Age glyph descriptions remain pending.
+- New Ages save their entered display name independently of their ID, folder
+  and seed. Newly bound Linking Books and automatic Return Links capture their
+  destination/departure label for both GUI and tooltip. Older Ages/books retain
+  vanilla-name or dimension-ID fallbacks; existing labels are not rewritten.
+- Corrected negative tooltip coordinates to floor consistently with the GUI.
+
+## Progression and recipe discovery
+
+- Ported the Rivencraft advancement tree: root, obtaining a Page/Linking Book,
+  taking a Link Panel from the Ink Mixer, copying a Page, binding an Age and
+  successfully travelling into an Age. Action awards occur after committed
+  server actions, including normal and shift pickup; previews earn nothing.
+- The advancement background uses the existing blue Crystal Block texture,
+  with the corrected 26.3 resource-path format. The portal node waits for the
+  Receptacle/portal port.
+- Added recipe-book discovery for Ink Vials (Black Dye), Ink Mixers (Glass
+  Bottle), Book Binders (Iron Ingot) and Crystal Blocks (Crystal Shard), alongside
+  the Notebook and Writing Desk unlocks. Three-by-three recipes appear in a
+  Crafting Table's recipe book, not the inventory's two-by-two book.
+- Ingredients and costs are unchanged. Blank Pages remain uncraftable.
+
+## Validation and remaining work
+
+- Player in-game checks passed each slice and the final dropped-book changes.
+- The 26.3 and independent 1.21.1 builds passed. Gradle test tasks have no
+  standalone test sources; targeted disposable-server fixtures covered real
+  station actions, advancements/recipe unlocks, stand ownership/drops and
+  persistence, book author/page/name persistence, and drop conversion/state.
+- Temporary test servers were stopped and their worlds deleted. A no-player
+  entity fixture required one loaded fixture chunk for inspection; further
+  visual/restart validation was handed to the player.
+- 1.21.1 gameplay code is unchanged. Shared issue #114 remains open for its
+  matching universal dropped-book fix; Writing Desk model placement stays in #113.
+- Instability, full writing recovery, discovery/library loot, crystal portals,
+  remaining stations/progression and optional integrations still need port work.
+
+Keep 26.3 and 1.21.1 instances/saves separate and back up beta worlds before updating.

ports/mc263/RELEASE_NOTES_1.0.1.120-beta.1.md

@@ -0,0 +1,85 @@
+# Rivencraft 26.3 beta 1.0.1.120-beta.1
+
+Collects the player-validated .116–.120 port slices since 1.0.1.115-beta.1.
+For Minecraft 26.3, NeoForge 26.3.0.99 and Java 25. The independent 1.21.1
+release is unchanged; full gameplay and optional-integration parity remain incomplete.
+
+## Libraries and writing
+
+- Ported Legacy library generation, shared schematic, chest loot and five correctly
+  oriented book/page stands. Libraries generate after decoration in eligible new
+  non-Cave Age chunks, using the 1.21.1 spacing, terrain and clearance checks.
+- Library loot defaults to `LEGACY`; optional `AGE_ONLY` limits new library Pages
+  to known symbols originally written into that Age. Original writing is saved
+  separately and restored on reload. Older Ages without it have an empty Age-only
+  pool. Ordinary Books replace stand Pages when that pool is empty.
+- Added operator library placement, candidate/probe/loot diagnostics, session-only
+  test spacing and a locator limited to nearby already-loaded chunks.
+- Hand-prepared Link Panel ink cost is server-configurable (default two). The
+  Ink Mixer still consumes one ink unit and one paper per panel. Writing Desk
+  ink handling now uses the shared service.
+
+## Crystal portals
+
+- Ported craftable Book Receptacles with all six mounting orientations and the
+  existing 1.21.1 model/book transforms. A bound Linking or Descriptive Book
+  activates a valid connected crystal frame, including supported irregular frames.
+- Reused the bounded crystal flood/tension algorithm, placement protection events,
+  rollback, owner persistence, restart repair, frame cleanup and traversal cooldown.
+- Empty-hand removal closes the portal and returns the book. Breaking the holder
+  or its crystal support closes it and drops a recoverable open-book entity.
+- Player and non-player travel reuse book destinations, safe arrival, Intra-Linking,
+  Disarm and momentum rules. Descriptive Books share the same landing resolver
+  with portals; no separate portal exit offset is added. Player Return Link policy
+  and progression remain in force.
+- The animated fallback surface renders its facing sides and uses destination sky
+  tint. The Open Portal advancement and receptacle recipe unlock are restored.
+  Live destination views are still pending optional integration work.
+
+## Instability and colored decay
+
+- New Ages save operator-only creation-time score contributions and deterministic
+  provider selections using all five Legacy decks. Existing Ages remain neutral;
+  reloads/config changes do not reroll stored plans.
+- Initial scoring covers Bright Lighting, Accelerated, Corrupted Pages, ineffective
+  Cave sky/weather modifiers, excess and biome-forced structures, and extra suns.
+  Corrupted Pages now bind successfully and retain their animated redacted text.
+- Ported 18 potion providers: local/global Blindness, Fatigue, Hunger, Nausea,
+  Poison, Slowness, Weakness and Wither, plus hostile Regeneration/Resistance.
+  General effects affect eligible Survival/Adventure players and living entities;
+  Creative/Spectator remain exempt. Local variants require sky exposure.
+- Added a bounded occupied-Age scheduler, owned-effect cleanup, provider controls
+  and operator score/status, enable/disable, session test-score and pulse commands.
+  Effects supplied or extended by another source are preserved.
+- Ported Blue, Purple, Red and White decay with the existing 16x16 textures,
+  hardness/air conversion odds, saved per-color frontiers and attempt sequence.
+  White retains stepping-contact magic damage. Decay has no item form or drops.
+- Spread uses only already-loaded candidate chunks, bounded attempts and action
+  budgets. Fluids, block entities, critical/unbreakable blocks, infrastructure,
+  protected tags and claim events prevent conversion.
+- The first resolved book/portal arrival is saved for spawn protection. Re-enter
+  an older Age once to record it. Global/Age/provider and world-mutation controls
+  gate spread; existing decay blocks remain when spreading is disabled.
+- Test a color with `/rivencraft_port instability decay blue 32` (also `purple`,
+  `red`, `white`); output includes actual changes and nearby tracked coordinates.
+  Scores are not added to ordinary book or Binder displays.
+
+## Validation and remaining work
+
+Player in-game checks passed .116–.120. Both the 26.3 and 1.21.1 builds passed;
+Gradle has no standalone test sources. Targeted disposable dedicated-server checks
+covered library placement, portal entity travel and restart ownership/cleanup,
+potion application/cleanup and persistence, all four decay colors, saved spread
+continuation, and bedrock/fluid protection. Test servers were stopped and their
+worlds removed.
+
+Full writing recovery/penalties, live material-abundance profiling, other instability
+hazards, remaining discovery/stations and optional integrations still need port work.
+Unported hazard cards remain saved and are reported as unavailable, rather than
+being replaced with different cards. Book previews remain the animated fallback.
+Machine acceleration (#112), Writing Desk model placement (#113), and the matching
+1.21.1 universal dropped-book fix (#114) remain tracked separately.
+
+Use matching client/server beta builds (catalog protocol 10). Keep Minecraft tracks
+and saves separate, back up beta worlds, and do not downgrade saves containing new
+blocks or data to earlier betas.

ports/mc263/RELEASE_NOTES_1.0.1.129-beta.1.md

@@ -0,0 +1,68 @@
+# Rivencraft 26.3 beta 1.0.1.129-beta.1
+
+Collects the player-validated .121–.129 port slices since 1.0.1.120-beta.1.
+For Minecraft 26.3, NeoForge 26.3.0.99 and Java 25. The independent Minecraft
+1.21.1 release is unchanged. Full parity and optional integrations remain in progress.
+
+## Instability hazards and live profiling
+
+- Ported lightning, explosions, falling meteor effects, burning and erosion with
+  bounded loaded-chunk scans, spawn protection, claim events and configurable
+  world/entity damage. Meteor flight uses the existing sound and particle effects.
+- Natural hazards choose randomized locations; operator test commands provide
+  targeted checks with independent cooldowns. Erosion retains its requested testing
+  default of enabled above 10,000 effective instability, outside the Legacy deck.
+- Ported persistent live material profiling, including native ores, valuable blocks,
+  recognized installed-mod materials and configurable modded block weight overrides.
+  No content mod is required. Profiling starts scoring after 401 Age and 500
+  Overworld baseline samples, with bounded gradual background sampling while an
+  eligible Age is occupied. A chunk snapshot is counted once.
+- Effective instability and deterministic provider selection now update as material
+  abundance is measured; the original writing contribution remains frozen. Added
+  difficulty scaling and operator-only sampling/score diagnostics. Older neutral
+  Ages remain neutral. Normal book/Binder screens do not reveal scores.
+
+## Ordered writing recovery
+
+- Repeated singular terrain, distribution, weather, lighting and sky controllers
+  use the last choice, adding 500 instability per duplicate/conflict. Category-order
+  mistakes add 100. Native distribution ignores supplied biomes; Single retains the
+  first biome when too many are supplied, with conflict penalties.
+- Repeated celestial modifiers use the final pending value of each kind. Dangling
+  modifiers and misplaced/trailing numbers allow binding and add 100 instability.
+  Numbers only attach to the immediately following supported target.
+- Preserved original book/library pages, ordered color mixing and independent
+  celestial chains. A trailing modifier cannot change an earlier sun or moon.
+  Unported pages, unsupported combinations and body limits remain enforced.
+
+## Link Modifier station
+
+- Added the creative-only Link Modifier with its existing model, textures and
+  Legacy single-book GUI. There is no crafting recipe.
+- Books can be renamed and edited through all six controls: Disarm, Intra-Linking,
+  Intra-Linking Only, Maintain Momentum, Relative Link and Generate Platform.
+- Intra-Linking Only enables Intra-Linking and prevents cross-dimension Linking
+  Book travel. Both intra controls are unavailable for Descriptive Books.
+- Relative Link preserves the traveller's offset from the source dimension spawn
+  at the destination spawn. Linking Book platform generation defaults off;
+  Descriptive Book fallback platforms default on and can be disabled.
+- Player and non-player portal paths share the new properties. Book contents and
+  flags persist in the station. Removal releases its stored book.
+- Fixed the controls ignoring real clicks: 26.3 left-click is button 1, not 0.
+  Registered native button widgets now handle input, focus, sound and state tooltips.
+
+## Validation and remaining work
+
+The player passed every included slice, including the six controls and click fix.
+Both Minecraft builds pass (no standalone Gradle test sources). Targeted temporary
+checks covered grammar/celestial recovery, component serialization, station actions,
+platform rules and dedicated-server save/restart behavior. Live profiling was checked
+with real snapshots plus synthetic threshold records; natural gameplay was validated
+by the player. Temporary servers were stopped and their test worlds removed.
+
+Link Modifier seed editing/retirement, remaining discovery/config policy and optional
+integrations are not complete. Live previews remain unavailable; books and portals
+use the animated fallback. Crumble has no active 1.21.1 handler and is not invented
+in this port. The dual-version follow-up issues and full multiplayer/parity gate
+remain open. Use matching client/server beta builds and keep Minecraft version
+tracks and their saves separate.

ports/mc263/RELEASE_NOTES_1.0.1.136-beta.1.md

@@ -0,0 +1,60 @@
+# Rivencraft 26.3 beta 1.0.1.136-beta.1
+
+Collects the player-validated .130–.136 port slices since 1.0.1.129-beta.1.
+For Minecraft 26.3, NeoForge 26.3.0.99 and Java 25. The Minecraft 1.21.1
+release and its Dynamic Dimensions backend are unchanged. This remains an
+incomplete beta port; use matching client/server builds and separate saves.
+
+## Link Modifier and Age creation
+
+- Edit a Descriptive Book Age's full signed 64-bit seed. Existing chunks remain;
+  newly generated terrain uses the new seed. Occupied Ages and stale/remote menu
+  requests are refused. Seed input supports Enter or focus loss without game keys
+  taking over while typing.
+- Operators can retire an unoccupied Age through a separate confirmation action.
+  Its exact dimension directory is archived under `world-retired-ages`; the Age
+  is tombstoned and cannot reload after restart. Other Age data remains intact.
+- Failed Age creation now rolls back the new level, index, initial name, library
+  writing, instability and season policy before publishing the catalog. Cleanup
+  removes only the newly created directory; pre-existing storage is protected.
+  Persistent filesystem failures or process crashes are not transactional guarantees.
+
+## Optional integrations
+
+All integrations remain optional and are never bundled.
+
+- **JEI:** searchable symbol pages, Link Panel variants and portfolios, with Ink
+  Mixer/Writing Desk/Book Binder guidance. Internal Blank Pages and empty portfolios
+  remain hidden. Tested with JEI 31.17.0.109 and MezzConfig 0.7.1.
+- **TerraBlender:** recognizes registered Overworld and Nether region biomes from
+  installed biome mods, including Biomes O' Plenty. Nether-region biomes join the
+  Cave-compatible authoring pool and use Nether material rules. Tested with
+  TerraBlender 26.3.0.0.9 and Biomes O' Plenty 26.3.0.0.16. The requested Native Cave
+  pool changes and Native Nether/End pages remain separate work in #111.
+- **Serene Seasons:** No Seasons, Seasons and all four Eternal modes operate per
+  Age. Missing policies are seed-selected only when Serene is installed; Cave Ages
+  disable seasons. Dynamic whitelist updates synchronize without restarting, while
+  eternal policies leave the Overworld calendar unchanged. Tested with Serene
+  Seasons 26.1.2.0.7 and GlitchCore 26.3.0.0.5.
+- **Ruins:** exact-template pages appear in creative and JEI. Authored Ages permit
+  only their selected templates; Ruins' surface, biome and distance checks remain.
+  Duplicate pages increase selection weight and attempts (32-attempt cap, without
+  lowering higher Ruins settings). The first three copies are free; each later
+  copy adds 100 instability, even beyond the attempt cap. Tested with Ruins
+  26.3.2NF. Duplicate template basenames disable the bridge to prevent ambiguity.
+
+## Validation and remaining work
+
+Both Minecraft builds pass. Every included slice passed player in-game checks;
+the latest client log confirms JEI, TerraBlender/BOP, Serene/GlitchCore and Ruins
+loaded together. Disposable dedicated-server checks covered seed changes with
+unchanged old chunks, retirement/archive isolation, injected creation failures,
+optional-mod absence, region discovery, season policies, Ruins template placement
+and restart/unload/reload persistence. Test fixtures/worlds were removed and test
+servers stopped. No permanent game tests were added.
+
+Books and crystal portals still use animated fallback previews. Live destination
+renderers, remaining discovery/configuration parity and random-Age glyph descriptions
+remain unfinished. The current expanded-catalog dedicated two-client regression
+and full parity/release gates remain open. Shared 1.21.1/26.3 follow-up issues are
+not complete merely because one version's implementation works.

ports/mc263/RELEASE_NOTES_1.0.1.98-beta.1.md

@@ -0,0 +1,63 @@
+# Rivencraft 26.3 beta 1.0.1.98-beta.1
+
+Collects the player-validated port slices .94–.98 since 1.0.1.93-beta.1.
+This beta is not yet feature-complete with Minecraft 1.21.1.
+
+## Seeded terrain and biome completion
+
+- Books without a Terrain page now choose terrain using the 1.21.1 weighted
+  selector. Incompatible choices are replaced with a seeded compatible terrain;
+  explicit Terrain pages retain their authored behavior.
+- Omitted biome controllers now use the seeded weighted distribution selector.
+  Supplied biome pages are retained, with missing minimum slots completed.
+  Void without biome pages still uses The Void. Link-Panel-only random Ages
+  retain their existing selection path.
+- Missing nonnative biome pools account for authored structures. Single chooses
+  a terrain-compatible biome satisfying all structure requirements where one
+  exists. Multiple-biome distributions add compatible biomes for unmet structure
+  requirements before completing their ordinary minimum. Explicit Single
+  choices are never replaced.
+- New Native Cave Ages freeze the full recognized Cave/Nether biome pool and
+  distribute it using seeded Tiny regions, matching the 1.21.1 implementation.
+  This includes recognized modded cave biomes. Existing empty Native Cave
+  profiles retain their previous Lush Caves fallback; explicit Single is unchanged.
+- Removing Nether-style biomes from the default Native Cave pool is separate
+  planned work for both versions in issue #111, not part of this release.
+
+## Accelerated pages
+
+- Ported the Accelerated environment page. Repeated pages stack, each adding
+  three extra random positions per eligible block section per tick near players.
+- Defaults match 1.21.1: at most eight already-loaded candidate chunks and
+  16,384 extra random-tick attempts per Age tick, shared fairly across sections.
+  No extra chunks are force-loaded.
+- Limits are configurable in `config/rivencraft-local.toml`, under
+  `accelerated_age`. A zero attempt budget disables the extra ticks.
+- Page counts persist across unload/reload, reseeding and restart. Existing
+  Ages default to zero. Pageless random Ages do not gain Accelerated automatically.
+- This currently affects random-ticking blocks such as crops and saplings.
+  Machine/block-entity acceleration is deferred for both versions under issue
+  #112; entities and scheduled block ticks are also unaffected. Instability
+  scoring remains part of the unfinished instability port.
+- Operator command `/rivencraft_port age acceleration <name>` reports the
+  saved page count and current budgets.
+
+## Compatibility and validation
+
+- Requires Minecraft **26.3**, NeoForge **26.3.0.99**, and **Java 25**. Dynamic
+  Dimensions and Bad Packets are not required. Minecraft 1.21.1 is unchanged.
+- Catalog protocol remains **10**. Use matching client/server builds.
+- Player in-game checks passed. Builds and targeted disposable-server checks
+  covered seeded completion, Native Cave sampling, tick-budget arithmetic,
+  unload/reload, reseeding and restart. Test servers were stopped and their
+  worlds removed. This was not a full automated GameTest run.
+- Back up worlds before updating. New populated Native Cave profiles cannot
+  be read by earlier beta builds; do not downgrade those saves. Keep Minecraft
+  1.21.1 and 26.3 saves separate.
+- Full writing recovery, discovery/stations, instability, crystal portals and
+  optional integration parity remain unfinished. Random-page eligibility config
+  and modded biome surface-rule integration also remain pending. Creative page
+  availability does not imply full support.
+
+Report issues and help improve the wiki at
+[BlackSheep Git](https://git.paddedcell.org/dnorberg/rivencraft).

ports/mc263/RELEASE_NOTES_26.3.0.1.md

@@ -0,0 +1,81 @@
+# Rivencraft 26.3.0.1
+
+For **Minecraft 26.3**, **NeoForge 26.3.0.99** and **Java 25**.
+
+This regular release collects the player-validated .137–.142 development slices
+since 1.0.1.136-beta.1. Versions now use the Minecraft version followed by the
+release slice and its iteration: `26.3.0.1`. The JAR is
+`rivencraft-26.3.0.1.jar`. The existing Minecraft 1.21.1 release is unchanged.
+
+## Live destination views with Immersive Portals Reborn
+
+- Optional live rotating destination views in Linking and Descriptive Books,
+  including books on stands. Reborn streams the actual destination chunks.
+- Crystal portals show a continuous live view across each coplanar opening,
+  masked to its shape, with the crystal frame remaining in front.
+- Linking Book views use the written destination/facing; Descriptive Book
+  portals preserve the traveler's facing. Views anchor standing eye height to
+  the opening's floor, so taller frames do not shift arrival height.
+- Rivencraft retains control of portal travel, Disarm, momentum and arrival
+  safety. The native view cannot independently teleport or interact remotely.
+- Preview sessions release their chunk streams on close, logout, invalidation
+  or expiry. Remote book-preview audio is suppressed and the player camera
+  restored after rendering.
+- Portal maintenance restores views after restart and removes them when the
+  book is removed or the frame is shut down.
+- Tested with **[Immersive Portals Reborn 7.0.12 for NeoForge 26.3](https://www.curseforge.com/minecraft/mc-mods/immersive-portals-reborn-unofficial-fork/files/9435354)**.
+  Use one portal fork per instance. No optional mod is bundled or required.
+- The renamed Seamless fork also receives runtime Age dimension/metadata
+  synchronization; this release's live rendering is enabled for Reborn.
+
+## Random Ages, pages and book descriptions
+
+- New random-Age and library-page allowlists/blocklists accept short paths such
+  as `sky/static`, as well as full namespaced IDs.
+- Blocklists take precedence. An allowlist restricts only the categories it
+  mentions. Existing Ages and manually authored books remain usable.
+- Required empty categories use safe defaults; optional empty categories can be
+  omitted. Native preset biome pools and necessary biome minimum fallbacks can
+  bypass individual biome-page exclusions.
+- Random-Age Descriptive Books show Legacy glyph descriptions of their public
+  traits, beneath the readable Age name/author. Seed and instability scores
+  remain absent from these descriptions.
+- Optional portal-engine dimension IDs and native metadata synchronize before
+  the Rivencraft catalog acknowledgement permits travel.
+
+## Configuration
+
+In `config/rivencraft-local.toml`:
+
+- `random_pages.allowlist` and `random_pages.blocklist`: default empty.
+- `book_previews.reborn_live_views`: default `true`; disable locally for
+  animated book panels.
+- `book_previews.reborn_crystal_live_views`: default `true`; the server
+  controls live crystal surfaces. Disabling retains animated surfaces and travel.
+
+The built-in Legacy animation remains available without optional renderers.
+Dynamic Dimensions and Bad Packets are not required by the 26.3 line.
+
+## Validation and known limits
+
+The user passed the included slices in game. Disposable checks covered random
+policy resolution, description/catalog serialization and persistence, native
+dimension IDs and packet formats for both portal forks, preview rendering and
+chunk-lease cleanup, all three crystal portal plane axes, both sides, destination
+eye/facing transforms, fallback toggling and full restart restoration. A real
+dedicated server/client displayed the live crystal view and crossed into its Age.
+The no-optional-mod server also started successfully. Temporary fixtures/worlds
+were removed and the production JAR contains no test or optional-engine classes.
+
+**Known issue [#116](https://git.paddedcell.org/dnorberg/rivencraft/issues/116):**
+with Reborn active, a Static Sky Age can render its sky outside the book GUI.
+Use the animated book panel option if affected.
+
+26.3 is now published on the regular release channel at the user's request.
+This is not a claim that every 1.21.1 behavior or the final expanded-catalog
+two-client regression is complete. The remaining multiplayer, parity and shared
+follow-up issues stay open. Preview exploration controls and Create/Ponder scenes
+are not included in this release.
+
+Use matching client/server JARs. Back up worlds, keep the Minecraft tracks and
+saves separate, and do not downgrade worlds containing newer data.

ports/mc263/TESTING_1.0.1.137-beta.1.md

@@ -0,0 +1,35 @@
+# Random Page policy test — 1.0.1.137-beta.1
+
+Install the new JAR and launch once so the new entries appear in
+Minecraft's config/rivencraft-local.toml. Close the instance before editing.
+On a dedicated server edit its own config, not the client's.
+
+For a visible check, replace only the existing random_pages section with:
+
+```toml
+[random_pages]
+allowlist = ["terrain/flat", "biome/single", "biome/plains", "sky/static", "lighting/normal", "weather/off", "feature/not_present"]
+blocklist = ["sky/nether", "celestial/sun", "celestial/moon"]
+```
+
+The deliberately nonexistent feature entry restricts only optional features,
+leaving an empty feature pool for this test.
+
+1. Bind a Descriptive Book with only a Link Panel. Enter it: expect Flat terrain,
+   Plains, Static Sky, normal lighting, no rain and no suns/moons. Optional Page
+   features/structures should be absent; native biome decoration is independent.
+2. Bind an authored Flat/Plains/Single/Nether Sky book. Nether Sky remains usable
+   despite the blocklist; the setting controls random generation and direct
+   library loot, not manual authorship. The Page remains visible in Creative/JEI.
+3. Change sky/static to sky/end, restart and revisit the first Age. It must retain
+   Static Sky. A newly bound Link-Panel-only book should get End Sky.
+4. Optional library check: allowlist = ["sky/static"], blocklist = ["sky/nether"].
+   New library direct Pages may include Static Sky or other unrestricted
+   categories, but never another Sky Page. Test both library loot modes where
+   desired. Existing chests/stands remain untouched; AGE_ONLY may have no Pages
+   when the book's written Page set has no eligible entries.
+
+Restore both lists to [] afterward unless you want the restrictions to persist.
+No existing Age should change. Keep the full world backup customary for beta
+updates. Native biome presets and required minimum-biome fallbacks intentionally
+bypass biome-Page filters; Sealed Notebooks keep their separate 1.21.1 draw pool.

ports/mc263/TESTING_1.0.1.138-beta.1.md

@@ -0,0 +1,21 @@
+# Random-Age glyph description test — 1.0.1.138-beta.1
+
+Use the new build on both client and server (Age catalog protocol 11).
+
+1. Open an existing or new Link-Panel-only Descriptive Book. Its front spread
+   should retain the plain-text Age name and author on the left, with the generated
+   description below rendered as Legacy glyphs. The destination animation remains
+   on the right and clicking it still travels.
+2. Put the same book on a lectern and open it. The description and panel should
+   match handheld use.
+3. Open an authored book containing Symbol Pages. Its front spread should retain
+   just the name/author, and page turning should show one authored symbol at a time.
+4. Reconnect or restart, then reopen the random book. Glyph traits should remain
+   consistent with its saved Age. Test a longer name and GUI scale for clipping.
+5. Check Writing Desk tab numbers around 24/25 and 49/50. Their existing glyph
+   size/position and base-25 behavior should be unchanged.
+
+Descriptions are available only for loaded Ages; viewing a book does not force-load
+an unloaded/retired Age. No instability score or seed appears in the description.
+The desktop glyph display still needs your visual check; server/codec/layout
+validation does not substitute for a real client render check.

ports/mc263/TESTING_1.0.1.139-beta.1.md

@@ -0,0 +1,8 @@
+# Superseded by the 1.0.1.140-beta.1 portal-fork test
+
+Use TESTING_1.0.1.140-beta.1.md. It covers both supported fork candidates.
+
+Correction: the user's installed Seamless file exactly matches current published
+CurseForge file 9218525 (displayed 10.0.0, internal version/filename 1.0.0).
+The startup failure applies only to older file 8937394. The earlier recommendation
+to avoid the current download was incorrect.

ports/mc263/TESTING_1.0.1.140-beta.1.md

@@ -0,0 +1,29 @@
+# Portal fork runtime compatibility — 1.0.1.140-beta.1
+
+Candidate downloads for Minecraft 26.3 / NeoForge:
+- Immersive Portals Reborn 7.0.12:
+  https://www.curseforge.com/minecraft/mc-mods/immersive-portals-reborn-unofficial-fork/files/9435354
+  Version 7.0.18 is Fabric, so use the NeoForge 7.0.12 file for this test.
+- Seamless latest file 9218525:
+  https://www.curseforge.com/minecraft/mc-mods/immersive-portal/files/9218525
+  Display name is 10.0.0, but its downloaded filename/internal version remain 1.0.0.
+  This exactly matches the user's installed working JAR.
+
+Use ONE portal fork per instance: they share engine classes and mixins.
+Prism files were left unchanged. Install matching Rivencraft builds on both sides
+for dedicated testing. Current tested loader is NeoForge 26.3.0.99.
+
+1. Enable/install the chosen fork and Rivencraft .140.
+2. Create an authored Descriptive Book after joining, using a distinctive sky and
+   lighting. Travel into its newly created Age without reconnecting.
+3. Return using a bound Linking Book and test a second freshly created Age.
+4. Restart and revisit both Ages. Check for unknown/unloaded-dimension rejection,
+   disconnects or incorrect sky/lighting.
+5. Test existing crystal portals through the usual Rivencraft fallback path.
+
+This slice synchronizes runtime Ages and native metadata. Live book panels and
+live crystal portal surfaces are NOT ported yet; animated fallbacks are expected.
+Actual client travel/packet handling needs your check. Server lifecycle, packet
+serialization and restart checks passed with both Reborn and latest Seamless
+(32 lifecycle/packet plus 15 restart checks each). NeoForge .102 is a candidate for a later isolated upgrade
+check; the project target has not been changed yet.

ports/mc263/TESTING_1.0.1.141-beta.1.md

@@ -0,0 +1,26 @@
+# 1.0.1.141-beta.1 — Reborn live book previews
+
+Use NeoForge 26.3.0.99 and Immersive Portals Reborn 7.0.12, CurseForge file 9435354.
+Install one portal fork per instance and matching Rivencraft builds on a dedicated
+server/client. Reborn remains optional; nothing is bundled.
+
+The user reports live views working in both book types. Follow-up coverage:
+1. View a Linking Book and Descriptive Book pointing to different Ages. Check
+   orbiting terrain, upright orientation, destination lighting/sky and the panel
+   cutout. Click the live panel to travel using the existing book controls.
+2. Repeat from a book stand, including a destination whose chunks are not loaded.
+3. Close/reopen, switch books quickly and restart/revisit the Age. A stale view
+   must not replace the newly selected destination.
+4. During rain, confirm the source world's weather audio remains audible and the
+   remote world's sounds do not leak into the GUI.
+5. Set [book_previews] reborn_live_views = false in rivencraft-local.toml to
+   verify the animated fallback; restore true for live views.
+
+The live image streams actual destination chunks. It is not restricted to the
+old fixed block snapshot volume. Exploration controls and live crystal portal
+surfaces are not included in this slice.
+
+Build and isolated dedicated/client rendering check passed, with a live Linking
+Book screenshot inspected and zero remaining preview leases on logout. Temporary
+test worlds were removed regardless of result. Reborn's four deprecated logoFile
+startup warnings concern its metadata, not Rivencraft rendering.

ports/mc263/TESTING_1.0.1.142-beta.1.md

@@ -0,0 +1,30 @@
+# 1.0.1.142-beta.1 — Reborn live crystal portal surfaces
+
+Use Reborn 7.0.12 for NeoForge 26.3, CurseForge file 9435354, with NeoForge
+26.3.0.99. Use one portal fork and matching Rivencraft builds on a server/client.
+
+Implemented and validated:
+- One continuous view per opening on each side, masked to the portal cells.
+- Correct destination eye-height reference; Linking Book facing and Descriptive
+  Book inherited facing.
+- Native surfaces render only; Rivencraft's blocks retain transport and effects.
+- Fallback model hidden only for established live surfaces.
+- Maintenance restores views after restart and removes them on shutdown/removal.
+- Optional server setting [book_previews] reborn_crystal_live_views = false retains
+  animated surfaces and ordinary portal travel.
+
+68 server checks and five restart checks passed, plus a real dedicated/client
+live-view and walking-through check. Screenshots were inspected and the user
+reported success. Temporary worlds were deleted and fixture sources removed.
+
+Useful follow-up manual coverage:
+1. Try both book types, compare portal arrival to using the same book, and inspect
+   both sides of the frame.
+2. Try taller, horizontal and irregular frames; check that frame edges occlude the
+   scene and the view does not repeat per cell.
+3. Restart, revisit, remove/reinsert the book and break a frame block.
+4. Check a destination with different sky/lighting and an initially unloaded
+   destination area.
+
+The initial synthetic render fixture used a blocked Y=1 target; that was corrected
+to the resolved Y=4 surface. No global landing-height behavior was changed.

ports/mc263/build.gradle

@@ -3,11 +3,61 @@ plugins {
     id 'net.neoforged.moddev' version '2.0.148'
 }
 
+repositories {
+    maven { url = 'https://www.cursemaven.com'; content { includeGroup 'curse.maven' } }
+    maven { url = 'https://api.modrinth.com/maven'; content { includeGroup 'maven.modrinth' } }
+    maven {
+        name = 'TerraBlenderMaven'
+        url = 'https://maven.minecraftforge.net/releases/'
+        content { includeGroup 'com.github.glitchfiend' }
+    }
+    maven {
+        name = 'JaredsMaven'
+        url = 'https://maven.blamejared.com'
+        content { includeGroup 'mezz.jei'; includeGroup 'net.mezzdev.config' }
+    }
+}
+// Optional APIs stay out of published dependency metadata.
+configurations {
+    localRuntime
+    runtimeClasspath.extendsFrom localRuntime
+}
+
+dependencies {
+    // Both optional forks retain qouteall APIs, but must never be loaded together.
+    if (project.hasProperty('withSeamlessPortals') && project.hasProperty('withImmersivePortalsReborn'))
+        throw new GradleException('Choose one Immersive Portals fork for the development run')
+    def portalDependency = project.hasProperty('withImmersivePortalsReborn')
+            ? 'curse.maven:immersive-portals-reborn-unofficial-fork-1721833:9435354'
+            : project.hasProperty('seamlessPortalsJar') ? files(project.property('seamlessPortalsJar'))
+            : project.hasProperty('withSeamlessPortals') ? 'curse.maven:immersive-portal-1511174:9218525'
+            : 'curse.maven:immersive-portals-reborn-unofficial-fork-1721833:9435354'
+    compileOnly portalDependency
+    if (project.hasProperty('withSeamlessPortals') || project.hasProperty('withImmersivePortalsReborn'))
+        localRuntime portalDependency
+    // Compile against the 26.3 baseline API; a local current Ruins JAR can override it.
+    def ruinsDependency = project.hasProperty('ruinsJar') ? files(project.property('ruinsJar'))
+            : 'curse.maven:ruins-227873:8962119'
+    compileOnly ruinsDependency
+    if (project.hasProperty('withRuins')) localRuntime ruinsDependency
+    compileOnly "maven.modrinth:e0bNACJD:${serene_seasons_version_id}"
+    compileOnly "maven.modrinth:s3dmwKy5:${glitchcore_version_id}"
+    if (project.hasProperty('withSereneSeasons')) {
+        localRuntime "maven.modrinth:e0bNACJD:${serene_seasons_version_id}"
+        localRuntime "maven.modrinth:s3dmwKy5:${glitchcore_version_id}"
+    }
+    compileOnly "com.github.glitchfiend:TerraBlender-neoforge:${minecraft_version}-${terrablender_version}"
+    if (project.hasProperty('withTerraBlender')) localRuntime "com.github.glitchfiend:TerraBlender-neoforge:${minecraft_version}-${terrablender_version}"
+    // Plugin-only API dependency: JEI is never bundled or required at runtime.
+    compileOnly "mezz.jei:jei-${minecraft_version}-neoforge-api:${jei_version}"
+    if (project.hasProperty('withJei')) localRuntime "mezz.jei:jei-${minecraft_version}-neoforge:${jei_version}"
+}
+
 group = 'net.dnorberg.rivencraft'
 version = mod_version
 
 base {
-    archivesName = "rivencraft-${minecraft_version}"
+    archivesName = "rivencraft"
 }
 
 java.toolchain.languageVersion = JavaLanguageVersion.of(25)
@@ -193,6 +243,10 @@ tasks.named('processResources', ProcessResources).configure {
         include 'data/rivencraft/worldgen/structure_set/bastions.json'
         include 'assets/rivencraft/models/block/star_fissure.json'
         include 'assets/rivencraft/blockstates/star_fissure.json'
+        include 'assets/rivencraft/blockstates/decay.json'
+        include 'assets/rivencraft/models/block/decay_*.json'
+        include 'assets/rivencraft/textures/block/decay_*.png'
+        include 'data/rivencraft/tags/block/decay_protected.json'
         include 'assets/rivencraft/sounds.json'
         include 'assets/rivencraft/sounds/**/*.ogg'
         include 'assets/rivencraft/textures/item/crystal_shard.png'
@@ -203,6 +257,25 @@ tasks.named('processResources', ProcessResources).configure {
         include 'assets/rivencraft/textures/gui/symbolcomponents.png'
         include 'assets/rivencraft/models/item/page_link_panel.json'
         include 'assets/rivencraft/textures/item/ink_vial.png'
+        include 'assets/rivencraft/textures/item/notebook.png'
+        include 'assets/rivencraft/textures/item/collation_folder.png'
+        include 'assets/rivencraft/models/item/notebook.json'
+        include 'assets/rivencraft/models/item/collation_folder.json'
+        include 'assets/rivencraft/textures/item/sealed_notebook.png'
+        include 'assets/rivencraft/textures/item/symbol_portfolio.png'
+        include 'assets/rivencraft/models/item/sealed_notebook.json'
+        include 'assets/rivencraft/models/item/symbol_portfolio.json'
+        include 'assets/rivencraft/textures/item/writing_desk.png'
+        include 'assets/rivencraft/textures/block/writing_desk.png'
+        include 'assets/rivencraft/textures/gui/writing_desk_legacy.png'
+        include 'assets/rivencraft/textures/gui/scrollbar.png'
+        include 'assets/rivencraft/models/item/writing_desk.json'
+        include 'assets/rivencraft/models/block/writing_desk.json'
+        include 'assets/rivencraft/models/block/writing_desk_extension.json'
+        include 'assets/rivencraft/blockstates/writing_desk.json'
+        include 'data/rivencraft/loot_table/blocks/writing_desk.json'
+        include 'data/rivencraft/advancement/progression/*.json'
+        exclude 'data/rivencraft/advancement/progression/root.json'
         include 'assets/rivencraft/textures/item/ink_vial.png.mcmeta'
         include 'assets/rivencraft/models/item/ink_vial.json'
         include 'assets/rivencraft/models/item/crystal_shard.json'
@@ -214,10 +287,19 @@ tasks.named('processResources', ProcessResources).configure {
         include 'assets/rivencraft/textures/gui/bookui_cover.png'
         include 'assets/rivencraft/textures/gui/notebook_pages.png'
         include 'assets/rivencraft/textures/gui/bookui_pager.png'
+        include 'assets/rivencraft/textures/gui/bookui_rpage_full.png'
         include 'assets/rivencraft/textures/block/crystal_block.png'
+        include 'assets/rivencraft/textures/entity/linking_book.png'
+        include 'assets/rivencraft/textures/entity/descriptive_book.png'
         include 'assets/rivencraft/textures/block/book_binder.png'
         include 'assets/rivencraft/textures/block/book_binder_press.png'
         include 'assets/rivencraft/textures/gui/book_binder_legacy.png'
+        include 'assets/rivencraft/textures/gui/link_modifier_legacy.png'
+        include 'assets/rivencraft/textures/block/link_modifier_*.png'
+        include 'assets/rivencraft/models/block/link_modifier.json'
+        include 'assets/rivencraft/models/item/link_modifier.json'
+        include 'assets/rivencraft/blockstates/link_modifier.json'
+        include 'data/rivencraft/loot_table/blocks/link_modifier.json'
         include 'assets/rivencraft/textures/gui/ink_mixer_legacy.png'
         include 'assets/rivencraft/textures/block/inkwell_base.png'
         include 'assets/rivencraft/textures/block/inkwell_cup.png'
@@ -230,9 +312,24 @@ tasks.named('processResources', ProcessResources).configure {
         include 'assets/rivencraft/models/block/book_binder.json'
         include 'assets/rivencraft/models/item/book_binder.json'
         include 'assets/rivencraft/blockstates/book_binder.json'
+        include 'assets/rivencraft/blockstates/book_receptacle.json'
+        include 'assets/rivencraft/blockstates/crystal_portal.json'
+        include 'assets/rivencraft/models/block/book_receptacle.json'
+        include 'assets/rivencraft/models/block/crystal_portal.json'
+        include 'assets/rivencraft/models/item/book_receptacle.json'
+        include 'assets/rivencraft/textures/block/book_receptacle.png'
+        include 'assets/rivencraft/textures/block/crystal_portal.png'
+        include 'assets/rivencraft/textures/block/crystal_portal.png.mcmeta'
+        include 'data/rivencraft/loot_table/blocks/book_receptacle.json'
+        include 'assets/rivencraft/blockstates/book_stand.json'
+        include 'data/rivencraft/loot_table/blocks/book_stand.json'
+        include 'data/rivencraft/loot_table/chests/mystcraft_library.json'
+        include 'data/rivencraft/structure/mystcraft_library.nbt'
         include 'data/rivencraft/loot_table/blocks/book_binder.json'
         include 'assets/rivencraft/models/block/crystal_block.json'
         include 'assets/rivencraft/blockstates/crystal_block.json'
+        include 'assets/rivencraft/models/block/cloud_platform.json'
+        include 'assets/rivencraft/blockstates/cloud_platform.json'
         include 'assets/rivencraft/blockstates/budding_crystal.json'
         include 'assets/rivencraft/blockstates/small_crystal_bud.json'
         include 'assets/rivencraft/blockstates/medium_crystal_bud.json'

ports/mc263/gradle.properties

@@ -7,4 +7,11 @@ neo_version=26.3.0.99
 mod_id=rivencraft
 mod_name=Rivencraft
 mod_license=LGPL-3.0-or-later
-mod_version=1.0.1.93-beta.1
+mod_version=26.3.0.1
+
+jei_version=31.17.0.109
+
+terrablender_version=26.3.0.0.9
+
+serene_seasons_version_id=QnvW5HPm
+glitchcore_version_id=pQgy3bfh

ports/mc263/port_en_us.json

@@ -85,10 +85,11 @@
   "symbol.rivencraft.feature.abandoned_camps": "Abandoned Camps",
   "symbol.rivencraft.feature.abandoned_camps.description": "Allow abandoned camps on surface noise terrain, including outside their usual biomes.",
   "symbol.rivencraft.block.generated.description": "Modify the next compatible feature. Without a following feature, choose a compatible feature from the Age seed.",
-  "symbol.rivencraft.biome.native.description": "Use the terrain's native biome source; do not include Biome pages.",
+  "symbol.rivencraft.biome.native.description": "Use the terrain's default biome source. Cave uses Tiny regions from recognized Cave/Nether biomes. Do not include Biome pages.",
   "symbol.rivencraft.feature.dungeons.description": "Add monster-room dungeon attempts throughout surface noise or Cave terrain, including Nether cave biomes. Not Flat or Void.",
   "symbol.rivencraft.biome.single.description": "Use one biome across the Age. If omitted, choose an eligible biome from the Age seed.",
   "symbol.rivencraft.terrain.flat.description": "A level, biome-decorated landscape with its foundation at Y=0.",
+  "symbol.rivencraft.environment.accelerated.description": "Adds extra random block ticks near players in this Age. Repeated pages stack within server tick budgets; does not speed up entities or machines.",
   "symbol.rivencraft.feature.floating_islands.description": "Add high floating islands alongside noise, Flat, or Void terrain; not Cave terrain.",
   "symbol.rivencraft.feature.caves.description": "Add extra cave carving to noise terrain, including Cave; not Flat or Void.",
   "symbol.rivencraft.feature.ravines.description": "Add canyon carving to noise terrain; not Flat or Void. Skips Nether biomes.",
@@ -105,5 +106,9 @@
   "symbol.rivencraft.feature.ruined_portals.description": "Allow ruined portals in noise terrain, including Cave, regardless of normal biome eligibility.",
   "symbol.rivencraft.feature.nether_fossils.description": "Allow Nether fossils in Cave terrain; the authored page overrides biome eligibility.",
   "symbol.rivencraft.feature.ancient_cities.description": "Allow underground Ancient Cities in noise terrain, including Cave, regardless of biome eligibility.",
-  "symbol.rivencraft.feature.trail_ruins.description": "Allow Trail Ruins in surface noise terrain, including outside their usual biomes."
+  "symbol.rivencraft.feature.trail_ruins.description": "Allow Trail Ruins in surface noise terrain, including outside their usual biomes.",
+  "jei.rivencraft.ink_mixer.usage": "Paper + ink makes a Link Panel. Each panel uses one paper and one ink. A vial supplies 16 ink and returns a glass bottle; additives reset when a panel is taken.",
+  "jei.rivencraft.link_modifier": "Creative-only tool; no crafting recipe. Insert a book to rename it and edit link properties. Bound Descriptive Books also allow seed editing while their Age is empty. Age retirement requires OP permission and a separate confirmation; its data is archived.",
+  "symbol.rivencraft.ruins.description": "Generates this Ruins template. Repeated pages increase its selection weight and spawn attempts.",
+  "itemGroup.rivencraft.pages.ruins": "Rivencraft Ruins Pages"
 }

ports/mc263/src/main/java/net/dnorberg/rivencraft/PortConfig.java

@@ -0,0 +1,80 @@
+package net.dnorberg.rivencraft;
+
+import net.neoforged.neoforge.common.ModConfigSpec;
+
+/** Server-owned gameplay policies adapted from 1.21.1. */
+public final class PortConfig {
+    public enum LibraryLootMode { LEGACY, AGE_ONLY }
+    public static final ModConfigSpec.EnumValue<LibraryLootMode> LIBRARY_LOOT_MODE;
+    public enum ReturnLinkMode { ON_CREATION, ALWAYS, DISABLED }
+    public static final ModConfigSpec.ConfigValue<java.util.List<? extends String>> RANDOM_PAGE_ALLOWLIST;
+    public static final ModConfigSpec.ConfigValue<java.util.List<? extends String>> RANDOM_PAGE_BLOCKLIST;
+    public static final ModConfigSpec.BooleanValue LIVE_BOOK_PREVIEWS;
+    public static final ModConfigSpec.BooleanValue CRYSTAL_LIVE_VIEWS;
+    public static final ModConfigSpec SPEC;
+    public static final ModConfigSpec.BooleanValue AUTO_WHITELIST_SERENE_AGES;
+    public static final ModConfigSpec.IntValue SYMBOL_INK_COST;
+    public static final ModConfigSpec.IntValue LINK_PANEL_INK_COST;
+    public static final ModConfigSpec.EnumValue<ReturnLinkMode> RETURN_LINK_MODE;
+    public static final ModConfigSpec.IntValue ACCELERATED_MAX_CHUNKS;
+    public static final ModConfigSpec.IntValue ACCELERATED_MAX_ATTEMPTS;
+
+    static {
+        var builder = new ModConfigSpec.Builder();
+        builder.push("book_previews");
+        LIVE_BOOK_PREVIEWS = builder.comment("Show live rotating destination views when Immersive Portals Reborn is installed on client and server.",
+                "Disable locally to retain the animated Legacy link panels.")
+                .define("reborn_live_views", true);
+        CRYSTAL_LIVE_VIEWS = builder.comment("Server option: create native live crystal portal surfaces when Reborn is installed.",
+                "Disabling keeps crystal portal travel with the animated surface.")
+                .define("reborn_crystal_live_views", true);
+        builder.pop();
+        builder.push("random_pages");
+        RANDOM_PAGE_ALLOWLIST = builder.comment(
+                "Page paths allowed in new random Ages and newly generated library pages.",
+                "Restricts only categories it mentions; other categories remain unrestricted.",
+                "Example: [\"sky/static\"]; full namespaced IDs are accepted too.")
+                .defineList("allowlist", java.util.List.<String>of(), () -> "sky/static", PortConfig::validPageId);
+        RANDOM_PAGE_BLOCKLIST = builder.comment(
+                "Page paths excluded from new random Ages and newly generated library pages.",
+                "Blocklist wins. Existing Ages, Creative/JEI pages and manually authored books remain usable.",
+                "Required empty categories use safe defaults; Native biomes come from the preset, not biome pages.")
+                .defineList("blocklist", java.util.List.<String>of(), () -> "sky/static", PortConfig::validPageId);
+        builder.pop();
+        builder.push("serene_seasons");
+        AUTO_WHITELIST_SERENE_AGES = builder.comment("Automatically whitelist Ages with seed-selected/legacy cycling seasons. Explicit pages still apply; existing entries are preserved when disabled.")
+                .define("auto_whitelist_ages", true);
+        builder.pop();
+        builder.push("descriptive_books");
+        RETURN_LINK_MODE = builder.comment("Controls automatic Return Links for successful Descriptive Book travel.",
+                "ON_CREATION issues one on the first arrival per Age/world; ALWAYS issues one each arrival; DISABLED issues none.")
+                .defineEnum("return_link_mode", ReturnLinkMode.DISABLED);
+        builder.pop();
+        builder.push("libraries");
+        LIBRARY_LOOT_MODE = builder.comment("LEGACY uses writing supplies/Sealed Notebooks and random lectern pages; AGE_ONLY uses only pages written into this Age.")
+                .defineEnum("loot_mode", LibraryLootMode.LEGACY);
+        builder.pop();
+        builder.push("writing");
+        SYMBOL_INK_COST = builder.comment("Ink units consumed for one Writing Desk symbol copy.")
+                .defineInRange("symbol_ink_cost", 1, 1, 16);
+        LINK_PANEL_INK_COST = builder.comment("Ink units consumed when preparing one baseline Link Panel by hand with paper.",
+                "The Ink Mixer uses one ink unit per panel independently of this setting.")
+                .defineInRange("link_panel_ink_cost", 2, 1, 16);
+        builder.pop();
+        builder.push("accelerated_age");
+        ACCELERATED_MAX_CHUNKS = builder.comment("Maximum already-loaded player-nearby chunks given extra random ticks per Age tick.")
+                .defineInRange("max_loaded_chunks", 8, 1, 64);
+        ACCELERATED_MAX_ATTEMPTS = builder.comment("Maximum extra random-tick positions sampled per Age tick, shared fairly across loaded sections; zero disables Accelerated.")
+                .defineInRange("max_random_tick_attempts_per_tick", 16384, 0, 65536);
+        builder.pop();
+        net.dnorberg.rivencraft.age.PortInstabilityConfig.define(builder);
+        SPEC = builder.build();
+    }
+
+    private static boolean validPageId(Object value) {
+        if (!(value instanceof String id)) return false;
+        try { net.dnorberg.rivencraft.age.PortRandomPagePolicy.parsePageId(id); return true; }
+        catch (IllegalArgumentException exception) { return false; }
+    }
+    private PortConfig() {}
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/Rivencraft.java

@@ -57,6 +57,15 @@ public final class Rivencraft {
     public static final Logger LOGGER = LogUtils.getLogger();
     private static final DeferredRegister.Blocks BLOCKS = DeferredRegister.createBlocks(MOD_ID);
     private static final DeferredRegister.Items ITEMS = DeferredRegister.createItems(MOD_ID);
+    private static final DeferredRegister<net.minecraft.world.entity.EntityType<?>> ENTITIES =
+            DeferredRegister.create(Registries.ENTITY_TYPE, MOD_ID);
+    public static final Supplier<net.minecraft.world.entity.EntityType<net.dnorberg.rivencraft.entity.DroppedBookEntity>>
+            DROPPED_BOOK = ENTITIES.register("dropped_book", () -> net.minecraft.world.entity.EntityType.Builder
+                    .<net.dnorberg.rivencraft.entity.DroppedBookEntity>of(
+                            net.dnorberg.rivencraft.entity.DroppedBookEntity::new, net.minecraft.world.entity.MobCategory.MISC)
+                    .sized(0.65F, 0.4F).clientTrackingRange(10).updateInterval(20)
+                    .build(net.minecraft.resources.ResourceKey.create(Registries.ENTITY_TYPE,
+                            Identifier.fromNamespaceAndPath(MOD_ID, "dropped_book"))));
     private static final DeferredRegister<SoundEvent> SOUNDS =
             DeferredRegister.create(Registries.SOUND_EVENT, MOD_ID);
     public static final Supplier<SoundEvent> LINK = sound("linking.link");
@@ -82,6 +91,12 @@ public final class Rivencraft {
     public static final Supplier<DataComponentType<Identifier>> AGE_BOOK_ID = COMPONENTS.registerComponentType(
             "age_book_id", builder -> builder.persistent(Identifier.CODEC)
                     .networkSynchronized(Identifier.STREAM_CODEC));
+    public static final Supplier<DataComponentType<net.dnorberg.rivencraft.writing.NotebookContents>> NOTEBOOK_CONTENTS =
+            COMPONENTS.registerComponentType("notebook_contents", builder -> builder
+                    .persistent(net.dnorberg.rivencraft.writing.NotebookContents.CODEC)
+                    .networkSynchronized(net.dnorberg.rivencraft.writing.NotebookContents.STREAM_CODEC));
+    public static final Supplier<DataComponentType<String>> LINK_DESTINATION_NAME = COMPONENTS.registerComponentType(
+            "link_destination_name", builder -> builder.persistent(Codec.STRING).networkSynchronized(ByteBufCodecs.STRING_UTF8));
     public static final Supplier<DataComponentType<LinkBookTarget>> LINK_BOOK_TARGET = COMPONENTS.registerComponentType(
             "link_book_target", builder -> builder.persistent(LinkBookTarget.CODEC)
                     .networkSynchronized(LinkBookTarget.STREAM_CODEC));
@@ -93,6 +108,8 @@ public final class Rivencraft {
             "symbol_page_id", builder -> builder.persistent(Identifier.CODEC)
                     .networkSynchronized(Identifier.STREAM_CODEC));
     /** Ordered authored page IDs remain on the finished book for later port slices. */
+    public static final Supplier<DataComponentType<String>> BOOK_AUTHOR = COMPONENTS.registerComponentType(
+            "book_author", builder -> builder.persistent(Codec.STRING).networkSynchronized(ByteBufCodecs.STRING_UTF8));
     public static final Supplier<DataComponentType<java.util.List<Identifier>>> BOOK_SYMBOLS = COMPONENTS.registerComponentType(
             "book_symbols", builder -> builder.persistent(Identifier.CODEC.listOf())
                     .networkSynchronized(ByteBufCodecs.<io.netty.buffer.ByteBuf, Identifier>list(252)
@@ -110,16 +127,52 @@ public final class Rivencraft {
 
     public static final DeferredBlock<Block> CRYSTAL_BLOCK = BLOCKS.registerBlock("crystal_block",
             Block::new, () -> BlockBehaviour.Properties.ofFullCopy(Blocks.AMETHYST_BLOCK));
+    public static final DeferredBlock<net.dnorberg.rivencraft.block.CloudPlatformBlock> CLOUD_PLATFORM =
+            BLOCKS.registerBlock("cloud_platform", net.dnorberg.rivencraft.block.CloudPlatformBlock::new,
+                    () -> BlockBehaviour.Properties.ofFullCopy(Blocks.AMETHYST_BLOCK)
+                            .mapColor(MapColor.COLOR_BLUE).strength(0.3F).noLootTable());
+    public static final DeferredBlock<net.dnorberg.rivencraft.block.BookReceptacleBlock> BOOK_RECEPTACLE =
+            BLOCKS.registerBlock("book_receptacle", net.dnorberg.rivencraft.block.BookReceptacleBlock::new,
+                    () -> BlockBehaviour.Properties.ofFullCopy(Blocks.AMETHYST_BLOCK).noOcclusion().mapColor(MapColor.COLOR_BLUE));
+    public static final DeferredItem<BlockItem> BOOK_RECEPTACLE_ITEM = ITEMS.registerSimpleBlockItem(BOOK_RECEPTACLE);
+    public static final DeferredBlock<net.dnorberg.rivencraft.block.CrystalPortalBlock> CRYSTAL_PORTAL =
+            BLOCKS.registerBlock("crystal_portal", net.dnorberg.rivencraft.block.CrystalPortalBlock::new,
+                    () -> BlockBehaviour.Properties.ofFullCopy(Blocks.NETHER_PORTAL)
+                            .noCollision().noOcclusion().lightLevel(state -> 11).noLootTable());
+    public static final Supplier<BlockEntityType<net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity>> BOOK_RECEPTACLE_BLOCK_ENTITY =
+            BLOCK_ENTITY_TYPES.register("book_receptacle", () -> new BlockEntityType<>(
+                    net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity::new, BOOK_RECEPTACLE.get()));
+    public static final Supplier<BlockEntityType<net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity>> CRYSTAL_PORTAL_BLOCK_ENTITY =
+            BLOCK_ENTITY_TYPES.register("crystal_portal", () -> new BlockEntityType<>(
+                    net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity::new, CRYSTAL_PORTAL.get()));
+    public static final DeferredBlock<net.dnorberg.rivencraft.block.DecayBlock> DECAY =
+            BLOCKS.registerBlock("decay", net.dnorberg.rivencraft.block.DecayBlock::new,
+                    () -> BlockBehaviour.Properties.ofFullCopy(Blocks.STONE).strength(5.0F, 10.0F).noLootTable());
     public static final DeferredBlock<StarFissureBlock> STAR_FISSURE =
             BLOCKS.registerBlock("star_fissure", StarFissureBlock::new,
                     () -> BlockBehaviour.Properties.ofFullCopy(Blocks.END_PORTAL).lightLevel(state -> 6));
     public static final Supplier<BlockEntityType<StarFissureBlockEntity>>
             STAR_FISSURE_BLOCK_ENTITY = BLOCK_ENTITY_TYPES.register("star_fissure", () -> new BlockEntityType<>(
                     StarFissureBlockEntity::new, STAR_FISSURE.get()));
+    public static final DeferredBlock<net.dnorberg.rivencraft.block.BookStandBlock> BOOK_STAND =
+            BLOCKS.registerBlock("book_stand", net.dnorberg.rivencraft.block.BookStandBlock::new,
+                    () -> BlockBehaviour.Properties.ofFullCopy(Blocks.LECTERN));
+    public static final Supplier<BlockEntityType<net.dnorberg.rivencraft.block.entity.BookStandBlockEntity>> BOOK_STAND_BLOCK_ENTITY =
+            BLOCK_ENTITY_TYPES.register("book_stand", () -> new BlockEntityType<>(
+                    net.dnorberg.rivencraft.block.entity.BookStandBlockEntity::new, BOOK_STAND.get()));
     public static final DeferredBlock<PortBookBinderBlock> BOOK_BINDER = BLOCKS.registerBlock(
             "book_binder", PortBookBinderBlock::new,
             () -> BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion());
     public static final DeferredItem<BlockItem> BOOK_BINDER_ITEM = ITEMS.registerSimpleBlockItem(BOOK_BINDER);
+    public static final DeferredBlock<net.dnorberg.rivencraft.block.LinkModifierBlock> LINK_MODIFIER = BLOCKS.registerBlock(
+            "link_modifier", net.dnorberg.rivencraft.block.LinkModifierBlock::new,
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.STONE).noOcclusion());
+    public static final DeferredItem<BlockItem> LINK_MODIFIER_ITEM = ITEMS.registerSimpleBlockItem(LINK_MODIFIER);
+    public static final Supplier<BlockEntityType<net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity>> LINK_MODIFIER_BLOCK_ENTITY =
+            BLOCK_ENTITY_TYPES.register("link_modifier", () -> new BlockEntityType<>(
+                    net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity::new, LINK_MODIFIER.get()));
+    public static final Supplier<MenuType<net.dnorberg.rivencraft.menu.LinkModifierMenu>> LINK_MODIFIER_MENU =
+            MENUS.register("link_modifier", () -> IMenuTypeExtension.create(net.dnorberg.rivencraft.menu.LinkModifierMenu::new));
     public static final DeferredBlock<InkMixerBlock> INK_MIXER = BLOCKS.registerBlock(
             "ink_mixer", InkMixerBlock::new,
             () -> BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion());
@@ -134,6 +187,25 @@ public final class Rivencraft {
                     new BlockEntityType<>(InkMixerBlockEntity::new, INK_MIXER.get()));
     public static final Supplier<MenuType<InkMixerMenu>> INK_MIXER_MENU =
             MENUS.register("ink_mixer", () -> IMenuTypeExtension.create(InkMixerMenu::new));
+    public static final DeferredBlock<net.dnorberg.rivencraft.block.WritingDeskBlock> WRITING_DESK =
+            BLOCKS.registerBlock("writing_desk", net.dnorberg.rivencraft.block.WritingDeskBlock::new,
+                    () -> BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion());
+    public static final DeferredItem<BlockItem> WRITING_DESK_ITEM = ITEMS.registerSimpleBlockItem(WRITING_DESK);
+    public static final Supplier<BlockEntityType<net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity>> WRITING_DESK_BLOCK_ENTITY =
+            BLOCK_ENTITY_TYPES.register("writing_desk", () -> new BlockEntityType<>(
+                    net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity::new, WRITING_DESK.get()));
+    public static final Supplier<MenuType<net.dnorberg.rivencraft.menu.WritingDeskMenu>> WRITING_DESK_MENU =
+            MENUS.register("writing_desk", () -> IMenuTypeExtension.create(net.dnorberg.rivencraft.menu.WritingDeskMenu::new));
+    public static final Supplier<MenuType<net.dnorberg.rivencraft.menu.NotebookMenu>> NOTEBOOK_MENU =
+            MENUS.register("notebook", () -> IMenuTypeExtension.create(net.dnorberg.rivencraft.menu.NotebookMenu::new));
+    public static final DeferredItem<net.dnorberg.rivencraft.item.NotebookItem> NOTEBOOK =
+            ITEMS.registerItem("notebook", net.dnorberg.rivencraft.item.NotebookItem::new, properties -> properties.stacksTo(1));
+    public static final DeferredItem<net.dnorberg.rivencraft.item.CollationFolderItem> COLLATION_FOLDER =
+            ITEMS.registerItem("collation_folder", net.dnorberg.rivencraft.item.CollationFolderItem::new, properties -> properties.stacksTo(1));
+    public static final DeferredItem<net.dnorberg.rivencraft.item.SymbolPortfolioItem> SYMBOL_PORTFOLIO =
+            ITEMS.registerItem("symbol_portfolio", net.dnorberg.rivencraft.item.SymbolPortfolioItem::new, properties -> properties.stacksTo(1));
+    public static final DeferredItem<net.dnorberg.rivencraft.item.SealedNotebookItem> SEALED_NOTEBOOK =
+            ITEMS.registerItem("sealed_notebook", net.dnorberg.rivencraft.item.SealedNotebookItem::new, properties -> properties.stacksTo(16));
     public static final DeferredItem<BlockItem> CRYSTAL_BLOCK_ITEM = ITEMS.registerSimpleBlockItem(CRYSTAL_BLOCK);
     public static final DeferredBlock<BuddingCrystalBlock> BUDDING_CRYSTAL = BLOCKS.registerBlock(
             "budding_crystal", BuddingCrystalBlock::new,
@@ -166,25 +238,44 @@ public final class Rivencraft {
     public static final Supplier<RecipeSerializer<LinkingBookRecipe>> LINKING_BOOK_RECIPE =
             RECIPE_SERIALIZERS.register("linking_book", () -> LinkingBookRecipe.SERIALIZER);
 
-    public Rivencraft(IEventBus modEventBus) {
+    public Rivencraft(IEventBus modEventBus, net.neoforged.fml.ModContainer container) {
+        container.registerConfig(net.neoforged.fml.config.ModConfig.Type.LOCAL, PortConfig.SPEC);
         BLOCKS.register(modEventBus);
         SOUNDS.register(modEventBus);
         ITEMS.register(modEventBus);
+        ENTITIES.register(modEventBus);
         BLOCK_ENTITY_TYPES.register(modEventBus);
         MENUS.register(modEventBus);
         COMPONENTS.register(modEventBus);
         RECIPE_SERIALIZERS.register(modEventBus);
+        net.dnorberg.rivencraft.compat.RuinsCompatibility.register();
+        net.dnorberg.rivencraft.compat.RebornBookPreviews.register();
         ModCreativeTabs.register(modEventBus);
         PortBiomeSources.register(modEventBus);
         PortChunkGenerators.register(modEventBus);
         NeoForge.EVENT_BUS.addListener(RuntimeAgeBackend::onLevelLoad);
+        NeoForge.EVENT_BUS.addListener(net.neoforged.bus.api.EventPriority.LOWEST,
+                net.dnorberg.rivencraft.compat.ImmersivePortalsCompatibility::onServerStarted);
         NeoForge.EVENT_BUS.addListener(net.dnorberg.rivencraft.age.PortAgeWeather::onLevelTickPre);
+        NeoForge.EVENT_BUS.addListener(net.dnorberg.rivencraft.age.PortAcceleratedTicks::onLevelTickPost);
         NeoForge.EVENT_BUS.addListener(PortAgeCommands::register);
+        NeoForge.EVENT_BUS.addListener(net.dnorberg.rivencraft.compat.TerraBlenderBiomes::onTagsUpdated);
+        NeoForge.EVENT_BUS.addListener(net.neoforged.bus.api.EventPriority.LOWEST,
+                net.dnorberg.rivencraft.compat.TerraBlenderBiomes::onServerAboutToStart);
+        NeoForge.EVENT_BUS.addListener(net.dnorberg.rivencraft.event.BookStandConversionHandler::onRightClickBlock);
         NeoForge.EVENT_BUS.addListener(AgeCatalogSync::onLogin);
+        NeoForge.EVENT_BUS.addListener(net.dnorberg.rivencraft.compat.SereneSeasonsCompatibility::onLevelLoad);
+        NeoForge.EVENT_BUS.addListener(net.dnorberg.rivencraft.compat.SereneSeasonsCompatibility::onLogin);
+        NeoForge.EVENT_BUS.addListener(net.dnorberg.rivencraft.compat.SereneSeasonsCompatibility::onLevelTickPost);
         NeoForge.EVENT_BUS.addListener(AgeCatalogSync::onLogout);
         NeoForge.EVENT_BUS.addListener(AgeCatalogSync::onServerStopped);
         modEventBus.addListener(AgeCatalogSync::registerPayloads);
         modEventBus.addListener(PortBookNetworking::registerPayloads);
+        net.dnorberg.rivencraft.age.PortStatusEffectProviders.register();
+        net.dnorberg.rivencraft.age.PortDecayProviders.register();
+        net.dnorberg.rivencraft.age.PortHazardProviders.register();
+        net.dnorberg.rivencraft.age.PortMeteorProvider.register();
+        net.dnorberg.rivencraft.age.PortEnvironmentalProviders.register();
         LOGGER.info("Initializing Rivencraft 26.3 port slice (not release-ready)");
     }
 }

ports/mc263/src/main/java/net/dnorberg/rivencraft/advancement/ProgressionAdvancements.java

@@ -0,0 +1,28 @@
+package net.dnorberg.rivencraft.advancement;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.age.RuntimeAgeBackend;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerPlayer;
+
+/** Awards action-only progression after the server has committed the action. */
+public final class ProgressionAdvancements {
+    public static final String OPEN_PORTAL = "open_portal";
+    public static final String LINK_PANEL = "link_panel";
+    public static final String COPY_PAGE = "copy_page";
+    public static final String BIND_AGE = "bind_age";
+    public static final String ENTER_AGE = "enter_age";
+
+    private ProgressionAdvancements() {}
+
+    public static void award(ServerPlayer player, String path) {
+        var advancement = player.level().getServer().getAdvancements().get(
+                Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "progression/" + path));
+        if (advancement != null) player.getAdvancements().award(advancement, "completed");
+    }
+
+    public static void awardAgeTravel(ServerPlayer player) {
+        if (RuntimeAgeBackend.savedAges(player.level().getServer()).containsKey(player.level().dimension().identifier()))
+            award(player, ENTER_AGE);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/AgeCatalogPayload.java

@@ -13,7 +13,8 @@ import net.minecraft.resources.Identifier;
 /** Full server level catalog, sent on login and after a runtime Age is added. */
 public record AgeCatalogPayload(int version, List<Identifier> dimensions,
                                 Map<Identifier, PortAgeColors> colors,
-                                Map<Identifier, PortDayCycle> dayCycles) implements CustomPacketPayload {
+                                Map<Identifier, PortDayCycle> dayCycles,
+                                Map<Identifier, PortAgeDescription> descriptions) implements CustomPacketPayload {
     public static final Type<AgeCatalogPayload> TYPE = new Type<>(
             Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age_catalog"));
     public static final StreamCodec<RegistryFriendlyByteBuf, AgeCatalogPayload> STREAM_CODEC = StreamCodec.composite(
@@ -21,6 +22,7 @@ public record AgeCatalogPayload(int version, List<Identifier> dimensions,
             Identifier.STREAM_CODEC.apply(ByteBufCodecs.list()), AgeCatalogPayload::dimensions,
             ByteBufCodecs.map(HashMap::new, Identifier.STREAM_CODEC, PortAgeColors.STREAM_CODEC), AgeCatalogPayload::colors,
             ByteBufCodecs.map(HashMap::new, Identifier.STREAM_CODEC, PortDayCycle.STREAM_CODEC), AgeCatalogPayload::dayCycles,
+            ByteBufCodecs.map(HashMap::new, Identifier.STREAM_CODEC, PortAgeDescription.STREAM_CODEC), AgeCatalogPayload::descriptions,
             AgeCatalogPayload::new
     );
 
@@ -28,6 +30,7 @@ public record AgeCatalogPayload(int version, List<Identifier> dimensions,
         dimensions = List.copyOf(dimensions);
         colors = Map.copyOf(colors);
         dayCycles = Map.copyOf(dayCycles);
+        descriptions = Map.copyOf(descriptions);
     }
 
     @Override

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/AgeCatalogSync.java

@@ -21,7 +21,7 @@ public final class AgeCatalogSync {
     }
 
     public static void registerPayloads(RegisterPayloadHandlersEvent event) {
-        var registrar = event.registrar("10");
+        var registrar = event.registrar("11");
         registrar.playToClient(AgeCatalogPayload.TYPE, AgeCatalogPayload.STREAM_CODEC);
         registrar.playToServer(AgeCatalogAckPayload.TYPE, AgeCatalogAckPayload.STREAM_CODEC,
                 (payload, context) -> {
@@ -55,6 +55,9 @@ public final class AgeCatalogSync {
         State state = state(server);
         state.version++;
         state.acknowledged.clear();
+        // Optional synchronization failures must not turn a committed Age into a
+        // reported binding failure. Withhold acknowledgements, so travel stays safe.
+        if (!net.dnorberg.rivencraft.compat.ImmersivePortalsCompatibility.synchronize(server)) return;
         for (ServerPlayer player : server.getPlayerList().getPlayers()) {
             try {
                 send(player);
@@ -76,9 +79,11 @@ public final class AgeCatalogSync {
         MinecraftServer server = player.level().getServer();
         State state = state(server);
         state.acknowledged.remove(player.getUUID());
+        if (!net.dnorberg.rivencraft.compat.ImmersivePortalsCompatibility.beforeCatalog(player))
+            throw new IllegalStateException("Optional portal dimension catalog is unavailable");
         var dimensions = server.levelKeys().stream().map(key -> key.identifier()).sorted().toList();
         PacketDistributor.sendToPlayer(player, new AgeCatalogPayload(state.version, dimensions,
-                RuntimeAgeBackend.savedColors(server), RuntimeAgeBackend.savedDayCycles(server)));
+                RuntimeAgeBackend.savedColors(server), RuntimeAgeBackend.savedDayCycles(server), RuntimeAgeBackend.loadedDescriptions(server)));
     }
 
     private static void acknowledge(ServerPlayer player, int version) {

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/AgeLevelIndex.java

@@ -42,7 +42,9 @@ final class AgeLevelIndex extends SavedData {
             Codec.unboundedMap(Identifier.CODEC, PortAgeColors.CODEC)
                     .optionalFieldOf("colors", Map.of()).forGetter(index -> index.colors),
             Codec.unboundedMap(Identifier.CODEC, PortDayCycle.CODEC)
-                    .optionalFieldOf("day_cycles", Map.of()).forGetter(index -> index.dayCycles)
+                    .optionalFieldOf("day_cycles", Map.of()).forGetter(index -> index.dayCycles),
+            Codec.unboundedMap(Identifier.CODEC, Codec.STRING)
+                    .optionalFieldOf("display_names", Map.of()).forGetter(index -> index.displayNames)
     ).apply(instance, AgeLevelIndex::new));
 
     static final SavedDataType<AgeLevelIndex> TYPE = new SavedDataType<>(
@@ -65,6 +67,7 @@ final class AgeLevelIndex extends SavedData {
     private final Map<Identifier, PortSkyStyle> sky;
     private final Map<Identifier, PortAgeColors> colors;
     private final Map<Identifier, PortDayCycle> dayCycles;
+    private final Map<Identifier, String> displayNames;
 
     private AgeLevelIndex() {
         this.ages = new LinkedHashMap<>();
@@ -81,6 +84,7 @@ final class AgeLevelIndex extends SavedData {
         this.sky = new LinkedHashMap<>();
         this.colors = new LinkedHashMap<>();
         this.dayCycles = new LinkedHashMap<>();
+        this.displayNames = new LinkedHashMap<>();
     }
 
     private AgeLevelIndex(Map<Identifier, Long> ages, List<Identifier> retired,
@@ -94,7 +98,7 @@ final class AgeLevelIndex extends SavedData {
                           Map<Identifier, PortTerrainFeaturePlan> terrainFeatures,
                           Map<Identifier, PortLighting> lighting,
                           Map<Identifier, PortSkyStyle> sky, Map<Identifier, PortAgeColors> colors,
-                          Map<Identifier, PortDayCycle> dayCycles) {
+                          Map<Identifier, PortDayCycle> dayCycles, Map<Identifier, String> displayNames) {
         this.ages = new LinkedHashMap<>(ages);
         this.retired = new LinkedHashSet<>(retired);
         this.biomeOverrides = new LinkedHashMap<>(biomeOverrides);
@@ -109,6 +113,16 @@ final class AgeLevelIndex extends SavedData {
         this.sky = new LinkedHashMap<>(sky);
         this.colors = new LinkedHashMap<>(colors);
         this.dayCycles = new LinkedHashMap<>(dayCycles);
+        this.displayNames = new LinkedHashMap<>(displayNames);
+    }
+
+    String displayName(Identifier id) { return ages.containsKey(id) ? displayNames.get(id) : null; }
+
+    void setDisplayName(Identifier id, String name) {
+        if (!ages.containsKey(id)) throw new IllegalArgumentException("Age not indexed: " + id);
+        if (name == null || name.isBlank() || name.length() > 32) throw new IllegalArgumentException("Invalid Age display name");
+        displayNames.put(id, name.strip());
+        setDirty();
     }
 
     Map<Identifier, Long> entries() {
@@ -168,8 +182,15 @@ final class AgeLevelIndex extends SavedData {
         setDirty();
     }
 
-    void retire(Identifier id) {
-        if (ages.remove(id) == null) throw new IllegalArgumentException("Age not indexed: " + id);
+    /** Failed creation is not retirement: release the new identity for a clean retry. */
+    void discardCreation(Identifier id) {
+        if (retired.contains(id)) throw new IllegalArgumentException("Cannot discard a retired Age: " + id);
+        removeActive(id);
+        displayNames.remove(id);
+        setDirty();
+    }
+    private void removeActive(Identifier id) {
+        ages.remove(id);
         biomeOverrides.remove(id);
         biomePlans.remove(id);
         terrain.remove(id);
@@ -182,6 +203,10 @@ final class AgeLevelIndex extends SavedData {
         sky.remove(id);
         colors.remove(id);
         dayCycles.remove(id);
+    }
+    void retire(Identifier id) {
+        if (!ages.containsKey(id)) throw new IllegalArgumentException("Age not indexed: " + id);
+        removeActive(id);
         retired.add(id);
         setDirty();
     }

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/InstabilityProviderCatalog.java

@@ -0,0 +1,74 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+
+/** Frozen Legacy 0.13.7.06 deck cards and default activation costs, not effect implementations. */
+public final class InstabilityProviderCatalog {
+    public enum Deck {
+        BASIC(0), HARSH(2_500), DESTRUCTIVE(10_000), EATING(15_000), DEATH(20_000);
+
+        private final int entryCost;
+
+        Deck(int entryCost) { this.entryCost = entryCost; }
+        public int entryCost() { return entryCost; }
+    }
+
+    public record Card(Identifier id, int cost) {
+        public Card {
+            if (cost <= 0) throw new IllegalArgumentException("Provider cost must be positive");
+        }
+    }
+
+    private static final List<List<Card>> DECKS = createDecks();
+
+    private InstabilityProviderCatalog() {}
+
+    public static List<Card> cards(Deck deck) { return DECKS.get(deck.ordinal()); }
+
+    public static boolean contains(Identifier id) {
+        return DECKS.stream().flatMap(List::stream).anyMatch(card -> card.id().equals(id));
+    }
+
+    private static List<List<Card>> createDecks() {
+        List<List<Card>> decks = new ArrayList<>();
+        for (Deck ignored : Deck.values()) decks.add(new ArrayList<>());
+        add(decks, "blindness", 1000, 0, 0, 0, 1, 0);
+        add(decks, "blindness_global", 1500, 0, 0, 0, 0, 1);
+        add(decks, "enemyregen_global", 1000, 5, 2, 0, 0, 0);
+        add(decks, "enemyresist_global", 1000, 2, 1, 0, 0, 0);
+        add(decks, "fatigue", 500, 5, 0, 0, 0, 0);
+        add(decks, "fatigue_global", 1000, 0, 5, 0, 0, 0);
+        add(decks, "hunger", 500, 8, 2, 0, 0, 0);
+        add(decks, "hunger_global", 1000, 0, 5, 0, 0, 0);
+        add(decks, "nausea", 1000, 0, 0, 0, 1, 0);
+        add(decks, "nausea_global", 1500, 0, 0, 0, 0, 1);
+        add(decks, "poison", 500, 9, 3, 0, 0, 0);
+        add(decks, "poison_global", 1000, 0, 5, 0, 0, 0);
+        add(decks, "slow", 500, 6, 1, 0, 0, 0);
+        add(decks, "slow_global", 1000, 0, 5, 0, 0, 0);
+        add(decks, "weakness", 500, 8, 2, 0, 0, 0);
+        add(decks, "weakness_global", 1000, 0, 5, 0, 0, 0);
+        add(decks, "wither", 1000, 0, 1, 1, 2, 0);
+        add(decks, "wither_global", 2000, 0, 0, 1, 1, 1);
+        add(decks, "burning", 500, 0, 1, 0, 0, 0);
+        add(decks, "crumble", 2000, 0, 0, 6, 0, 0);
+        add(decks, "decayblue", 2000, 0, 0, 0, 2, 1);
+        add(decks, "decaypurple", 2000, 0, 0, 0, 2, 1);
+        add(decks, "decayred", 2000, 0, 0, 0, 2, 1);
+        add(decks, "decaywhite", 5000, 0, 0, 0, 1, 3);
+        add(decks, "explosions", 1000, 0, 0, 8, 0, 0);
+        add(decks, "lightning", 1000, 0, 4, 4, 0, 0);
+        add(decks, "meteors", 1000, 0, 0, 4, 0, 0);
+        return decks.stream().map(List::copyOf).toList();
+    }
+
+    private static void add(List<List<Card>> decks, String path, int cost, int... copies) {
+        Card card = new Card(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path), cost);
+        for (Deck deck : Deck.values()) {
+            for (int copy = 0; copy < copies[deck.ordinal()]; copy++) decks.get(deck.ordinal()).add(card);
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAcceleratedTicks.java

@@ -0,0 +1,119 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayList;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+import net.dnorberg.rivencraft.PortConfig;
+import net.minecraft.resources.Identifier;
+import net.neoforged.neoforge.event.tick.LevelTickEvent;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.SectionPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.LevelChunkSection;
+import net.minecraft.util.RandomSource;
+
+/** Extra random block ticks from authored Accelerated pages, bounded to loaded player chunks. */
+public final class PortAcceleratedTicks {
+    public static final Identifier PAGE = Identifier.fromNamespaceAndPath("rivencraft", "environment/accelerated");
+
+    private PortAcceleratedTicks() {}
+
+    public static int pageCount(List<Identifier> pages) {
+        return (int) pages.stream().filter(PAGE::equals).count();
+    }
+
+    public static void configure(ServerLevel level, int pages) {
+        if (!(level instanceof PortAgeLevel)) throw new IllegalArgumentException("Not a Rivencraft Age");
+        level.getDataStorage().computeIfAbsent(PortAccelerationSettings.TYPE).setPages(pages);
+        level.getDataStorage().saveAndJoin();
+    }
+
+    public static int pages(ServerLevel level) {
+        return level.getDataStorage().computeIfAbsent(PortAccelerationSettings.TYPE).pages();
+    }
+
+    public static void onLevelTickPost(LevelTickEvent.Post event) {
+        if (event.getLevel() instanceof PortAgeLevel level) tick(level);
+    }
+
+    static void tick(ServerLevel level) {
+        int maximumAttempts = PortConfig.ACCELERATED_MAX_ATTEMPTS.get();
+        if (maximumAttempts == 0) return;
+        int pages = pages(level);
+        if (pages == 0) return;
+
+        List<ChunkPos> chunks = loadedPlayerChunks(level);
+        if (chunks.isEmpty()) return;
+        int maximumChunks = Math.min(chunks.size(), PortConfig.ACCELERATED_MAX_CHUNKS.get());
+        int first = Math.floorMod(level.getServer().getTickCount(), chunks.size());
+        List<TickSection> eligible = new ArrayList<>();
+        for (int offset = 0; offset < maximumChunks; offset++) {
+            ChunkPos pos = chunks.get((first + offset) % chunks.size());
+            LevelChunk chunk = level.getChunkSource().getChunkNow(pos.x(), pos.z());
+            if (chunk == null) continue;
+            LevelChunkSection[] sections = chunk.getSections();
+            for (int sectionIndex = 0; sectionIndex < sections.length; sectionIndex++) {
+                LevelChunkSection section = sections[sectionIndex];
+                if (!section.isRandomlyTickingBlocks()) continue;
+                int baseY = SectionPos.sectionToBlockCoord(chunk.getSectionYFromSectionIndex(sectionIndex));
+                eligible.add(new TickSection(pos, baseY, section));
+            }
+        }
+        if (eligible.isEmpty()) return;
+
+        // Legacy attempts three positions per random-ticking section per page. Divide
+        // the bounded total between sections before ticking any one of them, so a
+        // lower section cannot exhaust the entire budget ahead of surface crops.
+        int total = attemptBudget(pages, eligible.size(), maximumAttempts);
+        int perSection = total / eligible.size();
+        int remainder = total % eligible.size();
+        int firstSection = Math.floorMod(level.getServer().getTickCount(), eligible.size());
+        RandomSource random = level.getRandom();
+        for (int offset = 0; offset < eligible.size(); offset++) {
+            TickSection candidate = eligible.get((firstSection + offset) % eligible.size());
+            int samples = perSection + (offset < remainder ? 1 : 0);
+            for (int sample = 0; sample < samples; sample++) {
+                int x = random.nextInt(16);
+                int y = random.nextInt(16);
+                int z = random.nextInt(16);
+                BlockState state = candidate.section().getBlockState(x, y, z);
+                if (state.isRandomlyTicking()) {
+                    state.randomTick(level, new BlockPos(candidate.chunk().getMinBlockX() + x,
+                            candidate.baseY() + y, candidate.chunk().getMinBlockZ() + z), random);
+                }
+            }
+        }
+    }
+
+    static int attemptBudget(int pages, int sections, int maximumAttempts) {
+        if (pages < 0 || sections < 0 || maximumAttempts < 0)
+            throw new IllegalArgumentException("Negative accelerated tick budget input");
+        if (sections == 0) return 0;
+        long perSection = 3L * pages;
+        return perSection > maximumAttempts / (long) sections
+                ? maximumAttempts : (int) (perSection * sections);
+    }
+
+    private static List<ChunkPos> loadedPlayerChunks(ServerLevel level) {
+        Set<ChunkPos> chunks = new LinkedHashSet<>();
+        for (var player : level.players()) {
+            ChunkPos center = player.chunkPosition();
+            for (int x = -1; x <= 1; x++) {
+                for (int z = -1; z <= 1; z++) {
+                    int chunkX = center.x() + x;
+                    int chunkZ = center.z() + z;
+                    if (level.getChunkSource().hasChunk(chunkX, chunkZ)) {
+                        chunks.add(new ChunkPos(chunkX, chunkZ));
+                    }
+                }
+            }
+        }
+        return new ArrayList<>(chunks);
+    }
+
+    private record TickSection(ChunkPos chunk, int baseY, LevelChunkSection section) {}
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAccelerationSettings.java

@@ -0,0 +1,24 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Age-local authored page count, retained across unload, restart and reseeding. */
+final class PortAccelerationSettings extends SavedData {
+    private static final Codec<PortAccelerationSettings> CODEC = Codec.intRange(0, Integer.MAX_VALUE)
+            .fieldOf("pages").codec().xmap(PortAccelerationSettings::new, settings -> settings.pages);
+    static final SavedDataType<PortAccelerationSettings> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "acceleration"),
+            () -> new PortAccelerationSettings(0), CODEC);
+    private int pages;
+
+    private PortAccelerationSettings(int pages) { this.pages = pages; }
+    int pages() { return pages; }
+    void setPages(int pages) {
+        if (pages < 0) throw new IllegalArgumentException("Negative Accelerated page count");
+        this.pages = pages;
+        setDirty();
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAgeColors.java

@@ -69,7 +69,8 @@ public record PortAgeColors(int sky, int ambient, int celestial) {
     }
 
     public static PortAgeColors compile(List<Identifier> pages, long seed) {
-        if (!validNumbers(pages)) throw new IllegalArgumentException("Number pages must precede a supported Color, Length, Phase, Angle, or Size modifier");
+        // Numbers only attach to the immediately following target. Misplaced
+        // numbers are diagnosed by PortWritingRecovery, never moved to a later color.
         int red = 0, green = 0, blue = 0, sky = -1, ambient = -1, celestial = -1;
         boolean written = false;
         for (int i = 0; i < pages.size(); i++) {

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAgeCommands.java

@@ -35,12 +35,18 @@ public final class PortAgeCommands {
     public static void register(RegisterCommandsEvent event) {
         event.getDispatcher().register(Commands.literal("rivencraft_port")
                 .requires(Commands.hasPermission(Commands.LEVEL_ADMINS))
+                .then(Commands.literal("recipe_discovery_probe")
+                        .executes(context -> {
+                            PortProgressionProbe.recipeDiscovery(context.getSource().getServer().overworld());
+                            context.getSource().sendSuccess(() -> Component.literal("Recipe discovery checks passed for all six crafting unlocks"), false);
+                            return 1;
+                        }))
                 .then(Commands.literal("compat")
                         .executes(context -> {
                             StringBuilder mods = new StringBuilder("Optional mods: ");
                             for (String id : new String[]{"jei", "terrablender", "biomesoplenty",
                                     "sereneseasons", "glitchcore", "ruins", "create",
-                                    "ponder", "immersive_portals_core"}) {
+                                    "ponder", "immersive_portals_core", "seamlessportals", "immersive_portals_reborn"}) {
                                 if (mods.length() > "Optional mods: ".length()) mods.append(", ");
                                 mods.append(id).append('=').append(ModList.get().isLoaded(id));
                             }
@@ -69,6 +75,177 @@ public final class PortAgeCommands {
                                     return 1;
                                 })))
                 .then(Commands.literal("age")
+                        .then(Commands.literal("create_drop_conversion_fixture")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    var level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                                                            LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+                                                    PortBookDropConversionProbe.create(level);
+                                                    context.getSource().sendSuccess(() -> Component.literal("Drop sources queued; run drop_conversion_probe after server tasks complete"), false);
+                                                    return 1;
+                                                }))))
+                        .then(Commands.literal("drop_conversion_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            var level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, ageId(context)));
+                                            if (level == null) throw new IllegalArgumentException("Age not loaded");
+                                            PortBookDropConversionProbe.verify(level);
+                                            context.getSource().sendSuccess(() -> Component.literal("Universal book drop conversion/ownership checks passed"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("create_book_stand_fixture")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    var level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                                                            LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+                                                    PortBookStandProbe.create(level);
+                                                    context.getSource().sendSuccess(() -> Component.literal("Book Stand conversion/ownership/source checks passed"), false);
+                                                    return 1;
+                                                }))))
+                        .then(Commands.literal("book_stand_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            var level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, ageId(context)));
+                                            if (level == null) throw new IllegalArgumentException("Age not loaded");
+                                            PortBookStandProbe.verify(level);
+                                            context.getSource().sendSuccess(() -> Component.literal("Book Stand persistence passed"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("create_writing_desk_fixture")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    var level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                                                            LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+                                                    PortWritingDeskProbe.create(level);
+                                                    context.getSource().sendSuccess(() -> Component.literal("Writing Desk transaction/removal checks passed"), false);
+                                                    return 1;
+                                                }))))
+                        .then(Commands.literal("progression_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            var level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, ageId(context)));
+                                            if (level == null) throw new IllegalArgumentException("Age not loaded");
+                                            PortProgressionProbe.run(level);
+                                            context.getSource().sendSuccess(() -> Component.literal("Progression data/action checks passed"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("writing_desk_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            var level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, ageId(context)));
+                                            if (level == null) throw new IllegalArgumentException("Age not loaded");
+                                            PortWritingDeskProbe.verify(level);
+                                            context.getSource().sendSuccess(() -> Component.literal("Writing Desk persistence passed"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("create_collection_extras_fixture")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    var level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                                                            LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+                                                    PortCollectionExtrasProbe.create(level);
+                                                    context.getSource().sendSuccess(() -> Component.literal("Portfolio/Sealed Notebook checks passed"), false);
+                                                    return 1;
+                                                }))))
+                        .then(Commands.literal("collection_extras_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            var level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, ageId(context)));
+                                            if (level == null) throw new IllegalArgumentException("Age not loaded");
+                                            PortCollectionExtrasProbe.verify(level);
+                                            context.getSource().sendSuccess(() -> Component.literal("Portfolio/Sealed Notebook persistence passed"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("create_binder_collection_fixture")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    var level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                                                            LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+                                                    PortBinderCollectionProbe.create(level);
+                                                    context.getSource().sendSuccess(() -> Component.literal("Binder collection transaction/assembly checks passed"), false);
+                                                    return 1;
+                                                }))))
+                        .then(Commands.literal("binder_collection_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            var level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, ageId(context)));
+                                            if (level == null) throw new IllegalArgumentException("Age not loaded");
+                                            PortBinderCollectionProbe.verify(level);
+                                            context.getSource().sendSuccess(() -> Component.literal("Binder collection persistence passed"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("create_notebook_fixture")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    var level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                                                            LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+                                                    PortNotebookProbe.create(level);
+                                                    context.getSource().sendSuccess(() -> Component.literal("Notebook menu/codec checks passed"), false);
+                                                    return 1;
+                                                }))))
+                        .then(Commands.literal("notebook_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            var level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, ageId(context)));
+                                            if (level == null) throw new IllegalArgumentException("Age not loaded");
+                                            PortNotebookProbe.verify(level);
+                                            context.getSource().sendSuccess(() -> Component.literal("Notebook chest persistence passed"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("create_dropped_fixture")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    var level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                                                            LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+                                                    PortDroppedBookProbe.create(level);
+                                                    context.getSource().sendSuccess(() -> Component.literal("Dropped book ownership/codec checks passed"), false);
+                                                    return 1;
+                                                }))))
+                        .then(Commands.literal("dropped_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            var level = context.getSource().getServer().getLevel(
+                                                    ResourceKey.create(Registries.DIMENSION, ageId(context)));
+                                            if (level == null) throw new IllegalArgumentException("Age not loaded");
+                                            level.getChunk(0, 0);
+                                            PortDroppedBookProbe.verify(level);
+                                            context.getSource().sendSuccess(() -> Component.literal("Dropped book persistence checks passed"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("create_return_fixture")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(PortAgeCommands::createReturnFixture))))
+                        .then(Commands.literal("return_link_status")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::returnLinkStatus)))
+                        .then(Commands.literal("create_platform")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(PortAgeCommands::createPlatform))))
+                        .then(Commands.literal("platform_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probePlatform)))
+                        .then(Commands.literal("create_accelerated")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .then(Commands.argument("pages", IntegerArgumentType.integer(0, 256))
+                                                        .executes(PortAgeCommands::createAccelerated)))))
+                        .then(Commands.literal("acceleration")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::acceleration)))
+                        .then(Commands.literal("create_auto_terrain")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .then(Commands.argument("page", IdentifierArgument.id())
+                                                        .executes(PortAgeCommands::createAutomaticTerrain)))))
                         .then(Commands.literal("create_biome_surface")
                                 .then(Commands.argument("name", StringArgumentType.word())
                                         .then(Commands.argument("seed", LongArgumentType.longArg())
@@ -108,7 +285,10 @@ public final class PortAgeCommands {
                                         .then(Commands.argument("seed", LongArgumentType.longArg())
                                                 .then(Commands.argument("terrain", StringArgumentType.word())
                                                         .then(Commands.argument("distribution", StringArgumentType.word())
-                                                                .executes(PortAgeCommands::createCompletedBiomes))))))
+                                                                .executes(context -> createCompletedBiomes(context, null))
+                                                                .then(Commands.argument("structure", IdentifierArgument.id())
+                                                                        .executes(context -> createCompletedBiomes(context,
+                                                                                IdentifierArgument.getId(context, "structure")))))))))
                         .then(Commands.literal("biome_pool")
                                 .then(Commands.argument("name", StringArgumentType.word())
                                         .executes(PortAgeCommands::probeBiomePool)))
@@ -639,8 +819,8 @@ public final class PortAgeCommands {
                     || new PortDayCycle(true, 2, 0).ticks(12000) != 6000
                     || new PortDayCycle(true, 0, 321).ticks(-123456) != 321
                     || new PortDayCycle(true, 0, 321).ticks(123456) != 321
-                    || PortDayCycle.validWriting(java.util.List.of(symbol.apply("period/half")))
-                    || PortDayCycle.validWriting(java.util.List.of(PortDayCycle.NORMAL_TIME, symbol.apply("period/half"))))
+                    || !PortDayCycle.validWriting(java.util.List.of(symbol.apply("period/half")))
+                    || !PortDayCycle.validWriting(java.util.List.of(PortDayCycle.NORMAL_TIME, symbol.apply("period/half"))))
                 throw new IllegalStateException("Day cycle fixture failed");
             var server = context.getSource().getServer();
             var biomes = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(pages, server.registryAccess());
@@ -692,6 +872,63 @@ public final class PortAgeCommands {
         return 1;
     }
 
+    private static int createAutomaticTerrain(CommandContext<CommandSourceStack> context) {
+        try {
+            var server = context.getSource().getServer();
+            verifyAutomaticTerrain(server);
+            long seed = LongArgumentType.getLong(context, "seed");
+            var source = java.util.List.of(IdentifierArgument.getId(context, "page"));
+            var selected = net.dnorberg.rivencraft.writing.PortAuthoredTerrainSelection.select(server, source, seed);
+            var pages = selected.generationPages();
+            int created = createAge(context, selected.terrain(), selected.biomes(),
+                    net.dnorberg.rivencraft.writing.PortAuthoredWriting.rockPlan(pages, seed),
+                    net.dnorberg.rivencraft.writing.PortAuthoredWriting.vegetationPlan(pages),
+                    net.dnorberg.rivencraft.writing.PortAuthoredWriting.dungeonCount(pages),
+                    net.dnorberg.rivencraft.writing.PortAuthoredWriting.lakePlan(pages, seed),
+                    net.dnorberg.rivencraft.writing.PortAuthoredWriting.terrainFeaturePlan(pages, seed));
+            if (created != 0) context.getSource().sendSuccess(() -> Component.literal("Automatic terrain: " + selected), false);
+            return created;
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            context.getSource().sendFailure(Component.literal(exception.getMessage()));
+            return 0;
+        }
+    }
+
+    private static void verifyAutomaticTerrain(net.minecraft.server.MinecraftServer server) {
+        java.util.function.Function<String, Identifier> symbol = path -> Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+        var sky = java.util.List.of(symbol.apply("sky/overworld"));
+        var water = net.dnorberg.rivencraft.writing.PortRegistryPages.blockPageId(Identifier.withDefaultNamespace("water"));
+        var plains = net.dnorberg.rivencraft.writing.PortRegistryPages.biomePageId(Identifier.withDefaultNamespace("plains"));
+        var seen = java.util.EnumSet.noneOf(PortAgeTerrain.class);
+        for (long seed = 0; seed < 64; seed++) {
+            var selected = net.dnorberg.rivencraft.writing.PortAuthoredTerrainSelection.select(server, sky, seed);
+            seen.add(selected.terrain());
+            if (selected.terrain() != PortRandomAgeSelection.terrain(seed)
+                    || !selected.generationPages().subList(0, sky.size()).equals(sky)
+                    || !selected.equals(net.dnorberg.rivencraft.writing.PortAuthoredTerrainSelection.select(server, sky, seed)))
+                throw new IllegalStateException("Automatic terrain seed/determinism/page-prefix check failed");
+            var fortress = net.dnorberg.rivencraft.writing.PortAuthoredTerrainSelection.select(server,
+                    java.util.List.of(symbol.apply("feature/nether_fortresses")), seed);
+            if (fortress.terrain() != PortAgeTerrain.CAVE)
+                throw new IllegalStateException("Omitted terrain cannot host a Cave-only structure");
+            var wet = net.dnorberg.rivencraft.writing.PortAuthoredTerrainSelection.select(server, java.util.List.of(water), seed);
+            if (wet.terrain() == PortAgeTerrain.FLAT || wet.terrain() == PortAgeTerrain.VOID || wet.terrain() == PortAgeTerrain.CAVE)
+                throw new IllegalStateException("Automatic terrain cannot host its implied lake");
+            var biome = net.dnorberg.rivencraft.writing.PortAuthoredTerrainSelection.select(server, java.util.List.of(plains), seed);
+            if (biome.terrain() == PortAgeTerrain.CAVE || !biome.biomes().biomes().contains(Identifier.withDefaultNamespace("plains")))
+                throw new IllegalStateException("Automatic terrain discarded a supplied surface biome");
+            var explicit = net.dnorberg.rivencraft.writing.PortAuthoredTerrainSelection.select(server,
+                    java.util.List.of(symbol.apply("terrain/flat"), sky.getFirst()), seed);
+            if (explicit.terrain() != PortAgeTerrain.FLAT || explicit.generationPages().size() != 2)
+                throw new IllegalStateException("Explicit terrain lost precedence");
+        }
+        if (seen.size() != PortAgeTerrain.values().length
+                || !net.dnorberg.rivencraft.writing.PortAuthoredWriting.supports(java.util.List.of(symbol.apply("feature/nether_fortresses")))
+                || net.dnorberg.rivencraft.writing.PortAuthoredWriting.supports(java.util.List.of(
+                        symbol.apply("terrain/flat"), symbol.apply("feature/dungeons"))))
+            throw new IllegalStateException("Automatic terrain availability/coverage failed");
+    }
+
     private static int createBiomeSurface(CommandContext<CommandSourceStack> context) {
         try {
             var terrain = PortAgeTerrain.valueOf(StringArgumentType.getString(context, "terrain").toUpperCase(Locale.ROOT));
@@ -946,16 +1183,24 @@ public final class PortAgeCommands {
         return 1;
     }
 
-    private static int createCompletedBiomes(CommandContext<CommandSourceStack> context) {
+    private static int createCompletedBiomes(CommandContext<CommandSourceStack> context, Identifier structure) {
         try {
             var server = context.getSource().getServer();
             long seed = LongArgumentType.getLong(context, "seed");
             var terrain = PortAgeTerrain.valueOf(StringArgumentType.getString(context, "terrain").toUpperCase(Locale.ROOT));
-            var distribution = PortBiomePlan.Distribution.valueOf(
-                    StringArgumentType.getString(context, "distribution").toUpperCase(Locale.ROOT));
+            String distributionName = StringArgumentType.getString(context, "distribution");
+            var distribution = distributionName.equalsIgnoreCase("auto") ? null
+                    : PortBiomePlan.Distribution.valueOf(distributionName.toUpperCase(Locale.ROOT));
             java.util.function.Function<String, Identifier> symbol = path -> Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
-            var pages = java.util.List.of(symbol.apply("terrain/" + terrain.name().toLowerCase(Locale.ROOT)),
-                    symbol.apply("biome/" + distribution.name().toLowerCase(Locale.ROOT)));
+            var pages = new java.util.ArrayList<Identifier>();
+            pages.add(symbol.apply("terrain/" + terrain.name().toLowerCase(Locale.ROOT)));
+            if (distribution != null) pages.add(symbol.apply("biome/" + distribution.name().toLowerCase(Locale.ROOT)));
+            else verifyAutomaticBiomes(server);
+            if (structure != null) {
+                if (!PortStructurePages.supports(structure)) throw new IllegalArgumentException("Unsupported structure page " + structure);
+                pages.add(structure);
+                verifyStructureBiomes(server);
+            }
             var plan = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(pages, server, seed);
             // Controller-only and partial pools complete; already-sufficient pools never gain extras.
             var plains = net.dnorberg.rivencraft.writing.PortRegistryPages.biomePageId(Identifier.withDefaultNamespace("plains"));
@@ -980,7 +1225,10 @@ public final class PortAgeCommands {
             var encoded = PortBiomePlan.CODEC.encodeStart(com.mojang.serialization.JsonOps.INSTANCE, plan).getOrThrow();
             if (!plan.equals(PortBiomePlan.CODEC.parse(com.mojang.serialization.JsonOps.INSTANCE, encoded).getOrThrow()))
                 throw new IllegalStateException("Completed biome plan codec mismatch");
-            int created = createAge(context, terrain, plan);
+            var features = net.dnorberg.rivencraft.writing.PortAuthoredWriting.terrainFeaturePlan(pages, seed);
+            int created = createAge(context, terrain, plan, null, null, 0, null, features);
+            if (created != 0 && terrain == PortAgeTerrain.CAVE && plan.distribution() == PortBiomePlan.Distribution.NATIVE)
+                verifyNativeCave(server, ageId(context), seed, plan);
             if (created != 0) context.getSource().sendSuccess(() -> Component.literal("Completed biome plan: " + plan), false);
             return created == 0 ? 0 : probeBiomePool(context);
         } catch (IllegalArgumentException | IllegalStateException exception) {
@@ -989,6 +1237,121 @@ public final class PortAgeCommands {
         }
     }
 
+    private static void verifyAutomaticBiomes(net.minecraft.server.MinecraftServer server) {
+        java.util.function.Function<String, Identifier> symbol = path -> Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+        var standard = symbol.apply("terrain/standard");
+        var end = net.dnorberg.rivencraft.writing.PortRegistryPages.biomePageId(Identifier.withDefaultNamespace("the_end"));
+        var forest = net.dnorberg.rivencraft.writing.PortRegistryPages.biomePageId(Identifier.withDefaultNamespace("forest"));
+        var seen = java.util.EnumSet.noneOf(PortBiomePlan.Distribution.class);
+        var caveIds = java.util.Set.copyOf(PortRandomAgeSelection.eligibleBiomes(server, PortAgeTerrain.CAVE));
+        for (long seed = 0; seed < 128; seed++) {
+            var expected = PortRandomAgeSelection.distribution(seed);
+            var selected = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(java.util.List.of(standard), server, seed);
+            seen.add(selected.distribution());
+            if (selected.distribution() != expected || !selected.equals(
+                    net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                            java.util.List.of(standard, symbol.apply("weather/off")), server, seed)))
+                throw new IllegalStateException("Missing biome controller is not seeded/independent");
+            var authored = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(java.util.List.of(standard, end, forest), server, seed);
+            if (authored.biomes().size() != 2 || !authored.biomes().equals(java.util.List.of(
+                    Identifier.withDefaultNamespace("the_end"), Identifier.withDefaultNamespace("forest")))
+                    || authored.distribution() != (expected == PortBiomePlan.Distribution.NATIVE
+                        || expected == PortBiomePlan.Distribution.SINGLE ? PortBiomePlan.Distribution.TILED : expected))
+                throw new IllegalStateException("Automatic controller discarded or extended authored biomes");
+            var one = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(java.util.List.of(standard, end), server, seed);
+            if (!one.biomes().getFirst().equals(Identifier.withDefaultNamespace("the_end"))
+                    || one.distribution() != (expected == PortBiomePlan.Distribution.NATIVE ? PortBiomePlan.Distribution.SINGLE : expected)
+                    || one.biomes().size() != (one.distribution() == PortBiomePlan.Distribution.SINGLE ? 1 : 2))
+                throw new IllegalStateException("Automatic controller lost a supplied biome");
+            var cave = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                    java.util.List.of(symbol.apply("terrain/cave")), server, seed);
+            if (cave.distribution() != expected || !caveIds.containsAll(cave.biomes())
+                    || expected == PortBiomePlan.Distribution.NATIVE && !java.util.Set.copyOf(cave.biomes()).equals(caveIds))
+                throw new IllegalStateException("Automatic Cave controller/biome pool is invalid");
+            var emptyVoid = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                    java.util.List.of(symbol.apply("terrain/void")), server, seed);
+            var authoredVoid = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                    java.util.List.of(symbol.apply("terrain/void"), end), server, seed);
+            if (emptyVoid.distribution() != PortBiomePlan.Distribution.SINGLE
+                    || !emptyVoid.biomes().equals(java.util.List.of(Identifier.withDefaultNamespace("the_void")))
+                    || !authoredVoid.biomes().equals(java.util.List.of(Identifier.withDefaultNamespace("the_end"))))
+                throw new IllegalStateException("Automatic Void controller changed biome fallback");
+            var village = symbol.apply("feature/villages");
+            var withStructure = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(java.util.List.of(standard, village), server, seed);
+            if (withStructure.distribution() != PortBiomePlan.Distribution.NATIVE
+                    && withStructure.biomes().stream().noneMatch(PortStructurePages.compatibleBiomes(village, server.registryAccess())::contains))
+                throw new IllegalStateException("Automatic controller skipped structure-aware completion");
+        }
+        if (seen.size() != PortBiomePlan.Distribution.values().length)
+            throw new IllegalStateException("Automatic biome controller fixture lacks distribution coverage");
+    }
+
+    private static void verifyNativeCave(net.minecraft.server.MinecraftServer server, Identifier age, long seed, PortBiomePlan plan) {
+        var expected = PortRandomAgeSelection.caveBiomes(server.registryAccess());
+        if (!plan.biomes().equals(expected)) throw new IllegalStateException("Native Cave did not freeze the recognized biome pool");
+        var old = PortBiomePlan.CODEC.parse(com.mojang.serialization.JsonOps.INSTANCE,
+                com.google.gson.JsonParser.parseString("{\"distribution\":\"NATIVE\",\"biomes\":[]}")).getOrThrow();
+        if (!old.biomes().isEmpty() || old.distribution() != PortBiomePlan.Distribution.NATIVE)
+            throw new IllegalStateException("Old Native Cave plan was rewritten");
+        var level = server.getLevel(ResourceKey.create(Registries.DIMENSION, age));
+        var source = level.getChunkSource().getGenerator().getBiomeSource();
+        if (expected.size() < 2) return;
+        if (!(source instanceof PortScaledBiomeSource scaled)) throw new IllegalStateException("Native Cave is not using region distribution");
+        var registry = server.registryAccess().lookupOrThrow(Registries.BIOME);
+        var holders = plan.biomes().stream().map(id -> (net.minecraft.core.Holder<net.minecraft.world.level.biome.Biome>)
+                registry.getOrThrow(ResourceKey.create(Registries.BIOME, id))).toList();
+        var tiny = new PortScaledBiomeSource(net.minecraft.core.HolderSet.direct(holders), seed, 0);
+        var sampled = new java.util.HashSet<Identifier>();
+        for (int x = -64; x <= 64; x += 4) for (int z = -64; z <= 64; z += 4) {
+            var biome = scaled.getNoiseBiome(x, 0, z);
+            if (!biome.equals(tiny.getNoiseBiome(x, 0, z)) || !biome.equals(scaled.getNoiseBiome(x, 16, z)))
+                throw new IllegalStateException("Native Cave does not match root's Tiny-region sampler");
+            sampled.add(biome.unwrapKey().orElseThrow().identifier());
+        }
+        if (!java.util.Set.copyOf(expected).containsAll(sampled) || sampled.size() < 2)
+            throw new IllegalStateException("Native Cave sampler did not distribute its recognized biome pool");
+    }
+
+    private static void verifyStructureBiomes(net.minecraft.server.MinecraftServer server) {
+        java.util.function.Function<String, Identifier> symbol = path -> Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+        java.util.function.Function<String, Identifier> biome = name ->
+                net.dnorberg.rivencraft.writing.PortRegistryPages.biomePageId(Identifier.withDefaultNamespace(name));
+        var village = symbol.apply("feature/villages");
+        var fortress = symbol.apply("feature/nether_fortresses");
+        for (long seed = 0; seed < 32; seed++) {
+            var singlePages = java.util.List.of(symbol.apply("biome/single"), village);
+            var single = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(singlePages, server, seed);
+            var cave = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                    java.util.List.of(symbol.apply("terrain/cave"), symbol.apply("biome/single"), fortress), server, seed);
+            if (!PortStructurePages.compatibleBiomes(village, server.registryAccess()).contains(single.biomes().getFirst())
+                    || !single.equals(net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(singlePages, server, seed))
+                    || !PortStructurePages.compatibleBiomes(fortress, server.registryAccess()).contains(cave.biomes().getFirst()))
+                throw new IllegalStateException("Structure-aware Single completion failed");
+            var stronghold = symbol.apply("feature/strongholds");
+            var shared = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(java.util.List.of(
+                    symbol.apply("biome/single"), village, stronghold), server, seed);
+            if (!PortStructurePages.compatibleBiomes(village, server.registryAccess()).contains(shared.biomes().getFirst())
+                    || !PortStructurePages.compatibleBiomes(stronghold, server.registryAccess()).contains(shared.biomes().getFirst()))
+                throw new IllegalStateException("Single completion did not satisfy common structure requirements");
+            var explicit = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                    java.util.List.of(symbol.apply("biome/single"), biome.apply("the_end"), village), server, seed);
+            var nativePlan = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                    java.util.List.of(symbol.apply("biome/native"), village), server, seed);
+            if (!explicit.biomes().equals(java.util.List.of(Identifier.withDefaultNamespace("the_end")))
+                    || nativePlan.distribution() != PortBiomePlan.Distribution.NATIVE || !nativePlan.biomes().isEmpty())
+                throw new IllegalStateException("Explicit Single/Native biome precedence changed");
+            var multiPages = java.util.List.of(symbol.apply("biome/tiny"), biome.apply("forest"), biome.apply("the_end"), village);
+            var multi = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(multiPages, server, seed);
+            if (multi.biomes().size() != 3 || !multi.biomes().subList(0, 2).equals(java.util.List.of(
+                    Identifier.withDefaultNamespace("forest"), Identifier.withDefaultNamespace("the_end")))
+                    || !PortStructurePages.compatibleBiomes(village, server.registryAccess()).contains(multi.biomes().get(2)))
+                throw new IllegalStateException("Structure biome completion discarded authored choices");
+            var full = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(java.util.List.of(
+                    symbol.apply("biome/tiny"), biome.apply("plains"), biome.apply("forest"), village, village), server, seed);
+            if (full.biomes().size() != 2) throw new IllegalStateException("Compatible/repeated structures added unnecessary biomes");
+        }
+    }
+
     private static int probeBiomePool(CommandContext<CommandSourceStack> context) {
         var level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, ageId(context)));
         if (level == null) {
@@ -1253,7 +1616,7 @@ public final class PortAgeCommands {
                         || Math.abs(moving.bodyAngle(origin + 100) + 3F) > 0.0001F
                         || !PortDayCycle.validWriting(java.util.List.of(target, PortDayCycle.NORMAL_TIME))
                         || !PortDayCycle.validWriting(java.util.List.of(target, target))
-                        || PortDayCycle.validWriting(java.util.List.of(target, symbol.apply("size/large"))))
+                        || !PortDayCycle.validWriting(java.util.List.of(target, symbol.apply("size/large"))))
                     throw new IllegalStateException("Single-body modifier/order invariant failed");
             }
             var older = PortDayCycle.CODEC.parse(com.mojang.serialization.JsonOps.INSTANCE,
@@ -1414,7 +1777,7 @@ public final class PortAgeCommands {
 
     private static void verifyCatalogRoundTrip(net.minecraft.server.MinecraftServer server) {
         var payload = new AgeCatalogPayload(1, server.levelKeys().stream().map(key -> key.identifier()).toList(),
-                RuntimeAgeBackend.savedColors(server), RuntimeAgeBackend.savedDayCycles(server));
+                RuntimeAgeBackend.savedColors(server), RuntimeAgeBackend.savedDayCycles(server), RuntimeAgeBackend.loadedDescriptions(server));
         var buffer = new net.minecraft.network.RegistryFriendlyByteBuf(io.netty.buffer.Unpooled.buffer(),
                 server.registryAccess(), net.neoforged.neoforge.network.connection.ConnectionType.NEOFORGE);
         try {
@@ -1947,6 +2310,119 @@ public final class PortAgeCommands {
         return 1;
     }
 
+    private static int createReturnFixture(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        var local = new PortAgeVisits(java.util.List.of());
+        var disabled = net.dnorberg.rivencraft.PortConfig.ReturnLinkMode.DISABLED;
+        var always = net.dnorberg.rivencraft.PortConfig.ReturnLinkMode.ALWAYS;
+        var once = net.dnorberg.rivencraft.PortConfig.ReturnLinkMode.ON_CREATION;
+        if (PortReturnLinks.shouldIssue(disabled, local, id) || local.hasVisited(id)
+                || !PortReturnLinks.shouldIssue(always, local, id)
+                || !PortReturnLinks.shouldIssue(always, local, id) || local.hasVisited(id)
+                || !PortReturnLinks.shouldIssue(once, local, id)
+                || PortReturnLinks.shouldIssue(once, local, id))
+            throw new IllegalStateException("Return Link mode regression");
+        var encoded = PortAgeVisits.CODEC.encodeStart(com.mojang.serialization.JsonOps.INSTANCE, local).getOrThrow();
+        var decoded = PortAgeVisits.CODEC.parse(com.mojang.serialization.JsonOps.INSTANCE, encoded).getOrThrow();
+        if (!decoded.hasVisited(id) || PortReturnLinks.shouldIssue(once, decoded, id))
+            throw new IllegalStateException("Return Link visit codec regression");
+        var target = new LinkBookTarget(Identifier.fromNamespaceAndPath("minecraft", "overworld"),
+                12.25, 80.5, -42.75, 135.0F, -20.0F);
+        var book = PortReturnLinks.createBook(target);
+        if (!book.is(Rivencraft.LINKING_BOOK.get())
+                || !target.equals(book.get(Rivencraft.LINK_BOOK_TARGET.get()))
+                || !book.getHoverName().getString().equals("Return Link")
+                || book.has(Rivencraft.LINK_PROPERTIES.get()))
+            throw new IllegalStateException("Return Link book component regression");
+        var server = context.getSource().getServer();
+        RuntimeAgeBackend.create(server, id, LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+        var visits = server.overworld().getDataStorage().computeIfAbsent(PortAgeVisits.TYPE);
+        if (!PortReturnLinks.shouldIssue(once, visits, id) || PortReturnLinks.shouldIssue(once, visits, id))
+            throw new IllegalStateException("Return Link world marker regression");
+        server.overworld().getDataStorage().saveAndJoin();
+        return returnLinkStatus(context);
+    }
+
+    private static int returnLinkStatus(CommandContext<CommandSourceStack> context) {
+        var visits = context.getSource().getServer().overworld().getDataStorage().computeIfAbsent(PortAgeVisits.TYPE);
+        context.getSource().sendSuccess(() -> Component.literal(ageId(context) + " Return Link mode="
+                + net.dnorberg.rivencraft.PortConfig.RETURN_LINK_MODE.get()
+                + "; ON_CREATION issued=" + visits.hasVisited(ageId(context))), false);
+        return 1;
+    }
+
+    private static int createPlatform(CommandContext<CommandSourceStack> context) {
+        ServerLevel level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.VOID);
+        var landing = PortAgeTravel.findLanding(level);
+        if (!new net.minecraft.core.BlockPos(0, 64, 0).equals(landing))
+            throw new IllegalStateException("Unexpected Void landing: " + landing);
+        return probePlatform(context);
+    }
+
+    /** Inspect the disposable Void fixture without regenerating or repairing its platform. */
+    private static int probePlatform(CommandContext<CommandSourceStack> context) {
+        ServerLevel level = context.getSource().getServer().getLevel(
+                ResourceKey.create(Registries.DIMENSION, ageId(context)));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + ageId(context)));
+            return 0;
+        }
+        for (int x = -1; x <= 1; x++) for (int z = -1; z <= 1; z++) {
+            var pos = new net.minecraft.core.BlockPos(x, 63, z);
+            var state = level.getBlockState(pos);
+            if (!state.is(Rivencraft.CLOUD_PLATFORM.get())
+                    || state.getDestroySpeed(level, pos) != 0.3F
+                    || !state.isSolidRender() || !state.isCollisionShapeFullBlock(level, pos)
+                    || !state.getCloneItemStack(level, pos, false).isEmpty()
+                    || !net.minecraft.world.level.block.Block.getDrops(state, level, pos, null).isEmpty())
+                throw new IllegalStateException("Platform properties mismatch at " + pos);
+        }
+        Identifier id = Identifier.fromNamespaceAndPath("rivencraft", "cloud_platform");
+        if (net.dnorberg.rivencraft.writing.PortRegistryPages.solidMaterialIds().contains(id)
+                || net.dnorberg.rivencraft.writing.PortRegistryPages.find(
+                        net.dnorberg.rivencraft.writing.PortRegistryPages.blockPageId(id)) != null
+                || !Rivencraft.CLOUD_PLATFORM.get().asItem().equals(net.minecraft.world.item.Items.AIR))
+            throw new IllegalStateException("Platform is obtainable as an item or material Page");
+        context.getSource().sendSuccess(() -> Component.literal(ageId(context)
+                + " platform passed: solid/opaque, strength 0.3, no loot/pick item/material Page"), false);
+        return 1;
+    }
+
+    private static int createAccelerated(CommandContext<CommandSourceStack> context) {
+        int count = IntegerArgumentType.getInteger(context, "pages");
+        var pages = new java.util.ArrayList<Identifier>();
+        pages.add(Identifier.fromNamespaceAndPath("rivencraft", "terrain/flat"));
+        for (int i = 0; i < count; i++) pages.add(PortAcceleratedTicks.PAGE);
+        if (!net.dnorberg.rivencraft.writing.PortAuthoredWriting.supports(pages)
+                || !net.dnorberg.rivencraft.writing.PortAuthoredWriting.isPageImplemented(PortAcceleratedTicks.PAGE)
+                || PortAcceleratedTicks.pageCount(pages) != count
+                || PortAcceleratedTicks.attemptBudget(1, 8, 16384) != 24
+                || PortAcceleratedTicks.attemptBudget(32, 8, 16384) != 768
+                || PortAcceleratedTicks.attemptBudget(Integer.MAX_VALUE, Integer.MAX_VALUE, 16384) != 16384
+                || PortAcceleratedTicks.attemptBudget(32, 8, 0) != 0)
+            throw new IllegalStateException("Accelerated writing/budget regression");
+        ServerLevel level = RuntimeAgeBackend.create(context.getSource().getServer(), ageId(context),
+                LongArgumentType.getLong(context, "seed"), null, PortAgeTerrain.FLAT);
+        PortAcceleratedTicks.configure(level, count);
+        return acceleration(context);
+    }
+
+    private static int acceleration(CommandContext<CommandSourceStack> context) {
+        ServerLevel level = context.getSource().getServer().getLevel(
+                ResourceKey.create(Registries.DIMENSION, ageId(context)));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + ageId(context)));
+            return 0;
+        }
+        context.getSource().sendSuccess(() -> Component.literal(ageId(context) + " Accelerated pages="
+                + PortAcceleratedTicks.pages(level) + "; extra attempts/eligible section="
+                + 3L * PortAcceleratedTicks.pages(level)
+                + "; max loaded chunks=" + net.dnorberg.rivencraft.PortConfig.ACCELERATED_MAX_CHUNKS.get()
+                + "; max attempts/tick=" + net.dnorberg.rivencraft.PortConfig.ACCELERATED_MAX_ATTEMPTS.get()), false);
+        return 1;
+    }
+
     private static int sampleBiome(CommandContext<CommandSourceStack> context) {
         Identifier id = ageId(context);
         ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAgeDescription.java

@@ -0,0 +1,24 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.Map;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.resources.Identifier;
+
+/** Public presentation only: no seed, instability score or provider information. */
+public record PortAgeDescription(PortAgeTerrain terrain, PortBiomePlan.Distribution distribution,
+                                 PortLighting lighting, PortWeatherMode weather) {
+    public static final StreamCodec<RegistryFriendlyByteBuf, PortAgeDescription> STREAM_CODEC = StreamCodec.composite(
+            ByteBufCodecs.STRING_UTF8.map(PortAgeTerrain::valueOf, PortAgeTerrain::name), PortAgeDescription::terrain,
+            ByteBufCodecs.STRING_UTF8.map(PortBiomePlan.Distribution::valueOf, PortBiomePlan.Distribution::name), PortAgeDescription::distribution,
+            ByteBufCodecs.STRING_UTF8.map(PortLighting::valueOf, PortLighting::name), PortAgeDescription::lighting,
+            ByteBufCodecs.STRING_UTF8.map(PortWeatherMode::valueOf, PortWeatherMode::name), PortAgeDescription::weather,
+            PortAgeDescription::new);
+    private static volatile Map<Identifier, PortAgeDescription> clientDescriptions = Map.of();
+
+    public static void updateClient(Map<Identifier, PortAgeDescription> descriptions) {
+        clientDescriptions = Map.copyOf(descriptions);
+    }
+    public static PortAgeDescription forClient(Identifier id) { return clientDescriptions.get(id); }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAgeLevel.java

@@ -51,6 +51,8 @@ final class PortAgeLevel extends ServerLevel {
         return ageWeather == null ? super.getWeatherData() : ageWeather;
     }
 
+    boolean caveTerrain() { return cave; }
+
     PortWeatherMode weatherMode() { return cave ? PortWeatherMode.OFF : weatherSettings.mode(); }
 
     void configureWeather(PortWeatherMode mode) {

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAgeTravel.java

@@ -18,26 +18,49 @@ public final class PortAgeTravel {
     }
 
     public static String enter(ServerPlayer player, Identifier id) {
+        return enter(player, id, net.dnorberg.rivencraft.item.LinkProperties.NONE);
+    }
+    public static String enter(ServerPlayer player, Identifier id, net.dnorberg.rivencraft.item.LinkProperties properties) {
         ServerLevel target = player.level().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
         if (target == null) return "Age not loaded: " + id;
         if (!AgeCatalogSync.ready(player, id)) {
             return "Age catalog not acknowledged by client; remaining in source dimension";
         }
+        BlockPos landing = resolveLanding(target, player, properties);
+        if (landing == null) return "No safe landing available; remaining in source dimension";
+        boolean moved = player.teleportTo(target, landing.getX() + 0.5, landing.getY(), landing.getZ() + 0.5,
+                Set.of(), player.getYRot(), player.getXRot(), true);
+        return moved ? null : "Teleportation failed; remaining in source dimension";
+    }
+
+    public static BlockPos resolveLanding(ServerLevel target) { return resolveLanding(target, true); }
+    public static BlockPos resolveLanding(ServerLevel target, net.minecraft.world.entity.Entity entity,
+                                          net.dnorberg.rivencraft.item.LinkProperties properties) {
+        return resolveLanding(target, (ServerLevel) entity.level(), entity.blockPosition(), properties);
+    }
+    public static BlockPos resolveLanding(ServerLevel target, ServerLevel source, BlockPos departure,
+                                          net.dnorberg.rivencraft.item.LinkProperties properties) {
+        BlockPos landing = resolveLanding(target, !properties.has(net.dnorberg.rivencraft.item.LinkProperties.DISABLE_PLATFORM));
+        if (landing == null || !properties.has(net.dnorberg.rivencraft.item.LinkProperties.RELATIVE_LINK)) return landing;
+        return findFootedDestination(target, net.dnorberg.rivencraft.item.PortLinkDestinations.relativeOrigin(
+                source, target, departure)).orElse(null);
+    }
+    public static BlockPos resolveLanding(ServerLevel target, boolean generatePlatform) {
         boolean fissure = target.getChunkSource().getGenerator() instanceof PortFeatureChunkGenerator features
                 && features.terrainFeatures() != null && features.terrainFeatures().starFissures();
         BlockPos landing = fissure ? PortStarFissureFeature.savedSpawn(target) : null;
         if (landing != null) landing = isCaveTerrain(target)
                 ? findFootedDestination(target, landing).orElse(null)
                 : findSurfaceLanding(target, landing.getX(), landing.getZ());
-        if (landing == null) landing = findLanding(target);
-        if (landing == null) return "No safe test landing available; remaining in source dimension";
+        if (landing == null) landing = findLanding(target, generatePlatform);
+        if (landing == null) return null;
         if (fissure) PortStarFissureFeature.generateOnce(target, landing, isCaveTerrain(target));
-        boolean moved = player.teleportTo(target, landing.getX() + 0.5, landing.getY(), landing.getZ() + 0.5,
-                Set.of(), player.getYRot(), player.getXRot(), true);
-        return moved ? null : "Teleportation failed; remaining in source dimension";
+        if (target instanceof PortAgeLevel) PortInstabilityData.get(target.getServer()).recordSpawn(target, landing);
+        return landing;
     }
 
-    private static BlockPos findLanding(ServerLevel target) {
+    static BlockPos findLanding(ServerLevel target) { return findLanding(target, true); }
+    static BlockPos findLanding(ServerLevel target, boolean generatePlatform) {
         if (isCaveTerrain(target)) {
             // The cave roof is not a valid arrival surface. Search down from
             // Legacy's Y=64 start, then construct the normal safety platform
@@ -53,7 +76,7 @@ public final class PortAgeTravel {
                     }
                 }
             }
-            return makePlatform(target, new BlockPos(0, 64, 0));
+            return generatePlatform ? makePlatform(target, new BlockPos(0, 64, 0)) : null;
         }
         BlockPos surface = findSurfaceLanding(target, 0, 0);
         if (surface != null) return surface;
@@ -61,7 +84,7 @@ public final class PortAgeTravel {
         // beneath it. Void Ages retain the usual platform floor at Y=63.
         BlockPos obstruction = highestObstruction(target, 0, 0);
         int y = obstruction == null ? 64 : Math.max(64, obstruction.getY() + 3);
-        return makePlatform(target, new BlockPos(0, y, 0));
+        return generatePlatform ? makePlatform(target, new BlockPos(0, y, 0)) : null;
     }
 
     static BlockPos findSurfaceLanding(ServerLevel target, int originX, int originZ) {
@@ -112,7 +135,7 @@ public final class PortAgeTravel {
         }
         for (int x = -1; x <= 1; x++) {
             for (int z = -1; z <= 1; z++) {
-                target.setBlock(foot.offset(x, -1, z), Rivencraft.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
+                target.setBlock(foot.offset(x, -1, z), Rivencraft.CLOUD_PLATFORM.get().defaultBlockState(), 3);
             }
         }
         target.setBlock(foot, Blocks.AIR.defaultBlockState(), 3);

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortAgeVisits.java

@@ -0,0 +1,27 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** World-wide record of Ages for which an ON_CREATION Return Link was issued. */
+final class PortAgeVisits extends SavedData {
+    static final Codec<PortAgeVisits> CODEC = Identifier.CODEC.listOf().fieldOf("ages").codec()
+            .xmap(PortAgeVisits::new, visits -> visits.ages.stream().sorted().toList());
+    static final SavedDataType<PortAgeVisits> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "age_visits"),
+            () -> new PortAgeVisits(List.of()), CODEC);
+    private final Set<Identifier> ages;
+
+    PortAgeVisits(List<Identifier> ages) { this.ages = new HashSet<>(ages); }
+    boolean hasVisited(Identifier age) { return ages.contains(age); }
+    boolean markFirstVisit(Identifier age) {
+        if (!ages.add(age)) return false;
+        setDirty();
+        return true;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortBinderCollectionProbe.java

@@ -0,0 +1,157 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.entity.PortBookBinderBlockEntity;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.menu.PortBookBinderMenu;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.core.BlockPos;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.Container;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.block.Blocks;
+
+/** Disposable fixture for atomic collection imports and real Binder assembly. */
+final class PortBinderCollectionProbe {
+    private static final BlockPos BINDER = new BlockPos(0, 64, 0);
+    private static final BlockPos CHEST = new BlockPos(1, 64, 0);
+    private static final List<Identifier> EXPECTED = List.of(id("weather/off"), id("lighting/bright"),
+            id("terrain/flat"), id("biome/single"));
+    private PortBinderCollectionProbe() {}
+    private static Identifier id(String path) { return Identifier.fromNamespaceAndPath("rivencraft", path); }
+    private static ItemStack page(String path) { return PageItem.createSymbolPage(id(path)); }
+    private static ItemStack collection(boolean folder, List<ItemStack> pages) {
+        ItemStack result = new ItemStack(folder ? Rivencraft.COLLATION_FOLDER.get() : Rivencraft.NOTEBOOK.get());
+        result.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(pages));
+        return result;
+    }
+
+    static void create(ServerLevel level) {
+        PortAgeTravel.findLanding(level);
+        level.setBlock(BINDER, Rivencraft.BOOK_BINDER.get().defaultBlockState(), 3);
+        level.setBlock(CHEST, Blocks.CHEST.defaultBlockState(), 3);
+        var binder = (PortBookBinderBlockEntity) level.getBlockEntity(BINDER);
+        var chest = (Container) level.getBlockEntity(CHEST);
+        ItemStack folder = collection(true, List.of(page("weather/off"), ItemStack.EMPTY, page("lighting/bright")));
+        ItemStack before = folder.copy();
+        for (int i = 0; i < PortBookBinderBlockEntity.PAGE_COUNT; i++)
+            binder.setItem(PortBookBinderBlockEntity.FIRST_PAGE + i, page("terrain/flat"));
+        if (!binder.importCollection(folder, 0).isEmpty() || binder.nextPageIndex() != 252
+                || !ItemStack.isSameItemSameComponents(before, folder)
+                || binder.symbolPages().stream().anyMatch(symbol -> !symbol.equals(id("terrain/flat"))))
+            throw new IllegalStateException("Full Binder import was not atomic");
+        binder.clearSymbolPages();
+        binder.setItem(PortBookBinderBlockEntity.PANEL, PageItem.createLinkPanelPage());
+        if (!binder.importCollection(collection(true, List.of(page("weather/off"), PageItem.createLinkPanelPage())), 0).isEmpty()
+                || binder.hasSymbolPages() || binder.getItem(PortBookBinderBlockEntity.PANEL).isEmpty())
+            throw new IllegalStateException("Conflicting Link Panel import was not atomic");
+        binder.setItem(PortBookBinderBlockEntity.PANEL, ItemStack.EMPTY);
+        if (!binder.importCollection(folder, -1).isEmpty() || !binder.importCollection(folder, 1).isEmpty())
+            throw new IllegalStateException("Invalid collection insertion point accepted");
+        binder.insertPage(0, page("terrain/flat"));
+        var player = new PortProgressionPlayer(level,
+                new com.mojang.authlib.GameProfile(java.util.UUID.fromString("5225a1ed-5ead-44b5-a63c-c78e7dca86f5"), "RivenBinderProbe"));
+        player.setPos(0.5, 64, 2.5);
+        var menu = new PortBookBinderMenu(1, player.getInventory(), binder);
+        try {
+            menu.setCarried(folder);
+            if (!menu.clickMenuButton(player, PortBookBinderMenu.STRIP_CLICK_BASE + 1)
+                    || menu.getCarried().get(Rivencraft.NOTEBOOK_CONTENTS.get()).pageCount() != 0
+                    || !binder.symbolPages().equals(EXPECTED.subList(0, 3)))
+                throw new IllegalStateException("Cursor collection order/empty-cover regression");
+            chest.setItem(0, menu.getCarried().copy());
+            menu.setCarried(ItemStack.EMPTY);
+            player.getInventory().setItem(9, collection(false, List.of(page("biome/single"))));
+            menu.quickMoveStack(player, PortBookBinderBlockEntity.SIZE);
+            ItemStack emptied = player.getInventory().getItem(9);
+            if (!emptied.is(Rivencraft.NOTEBOOK.get())
+                    || emptied.get(Rivencraft.NOTEBOOK_CONTENTS.get()).pageCount() != 0
+                    || !binder.symbolPages().equals(EXPECTED))
+                throw new IllegalStateException("Shift collection import regression");
+            chest.setItem(1, emptied.copy());
+            binder.setItem(PortBookBinderBlockEntity.COVER, new ItemStack(Items.LEATHER));
+            binder.setItem(PortBookBinderBlockEntity.PANEL, PageItem.createLinkPanelPage());
+            menu.assemble(player, "Collection Fixture104");
+            ItemStack book = menu.getCarried();
+            if (!book.is(Rivencraft.DESCRIPTIVE_BOOK.get()) || !EXPECTED.equals(book.get(Rivencraft.BOOK_SYMBOLS.get()))
+                    || !book.has(Rivencraft.AGE_BOOK_ID.get()) || binder.hasSymbolPages()
+                    || !binder.getItem(PortBookBinderBlockEntity.COVER).isEmpty()
+                    || !binder.getItem(PortBookBinderBlockEntity.PANEL).isEmpty())
+                throw new IllegalStateException("Collection-backed Binder assembly regression");
+            if (!PortProgressionProbe.isComplete(player, "bind_age"))
+                throw new IllegalStateException("Missing bind_age award");
+            if (!player.getGameProfile().name().equals(book.get(Rivencraft.BOOK_AUTHOR.get())))
+                throw new IllegalStateException("Binder author was not server assigned");
+            var pages = net.dnorberg.rivencraft.writing.DescriptiveBookPages.from(book);
+            if (pages.lastPage() != EXPECTED.size() || pages.symbolAt(0).isPresent()
+                    || !pages.symbolAt(1).orElseThrow().equals(EXPECTED.getFirst())
+                    || !pages.symbolAt(EXPECTED.size()).orElseThrow().equals(EXPECTED.getLast())
+                    || pages.symbolAt(EXPECTED.size() + 1).isPresent()
+                    || pages.turn(0, -1) != 0 || pages.turn(pages.lastPage(), 1) != pages.lastPage())
+                throw new IllegalStateException("Authored book page indexing failed");
+            var old = net.dnorberg.rivencraft.writing.DescriptiveBookPages.from(new ItemStack(Rivencraft.DESCRIPTIVE_BOOK.get()));
+            if (old.lastPage() != 1 || !old.author().isEmpty() || old.symbolAt(1).isPresent())
+                throw new IllegalStateException("Older panel-only book fallback failed");
+            var repeated = new net.dnorberg.rivencraft.writing.DescriptiveBookPages(
+                    List.of(EXPECTED.getFirst(), EXPECTED.getFirst()), "Test");
+            if (repeated.lastPage() != 2 || !repeated.symbolAt(1).equals(repeated.symbolAt(2)))
+                throw new IllegalStateException("Repeated symbol display was collapsed");
+            var ageId = book.get(Rivencraft.AGE_BOOK_ID.get());
+            var server = level.getServer();
+            if (!RuntimeAgeBackend.savedAgeName(server, ageId).orElseThrow().equals("Collection Fixture104"))
+                throw new IllegalStateException("Created Age lost its display name");
+            var namedLevel = server.getLevel(net.minecraft.resources.ResourceKey.create(
+                    net.minecraft.core.registries.Registries.DIMENSION, ageId));
+            if (!net.dnorberg.rivencraft.item.LinkingBookItem.destinationName(namedLevel).equals("Collection Fixture104"))
+                throw new IllegalStateException("Link binding name lookup did not use Age title");
+            RuntimeAgeBackend.setAgeDisplayName(server, ageId, "Crystal Garden's Dawn");
+            var target = new net.dnorberg.rivencraft.item.LinkBookTarget(ageId, -0.5, 64, -1.25, 90, 0);
+            var link = new ItemStack(Rivencraft.LINKING_BOOK.get());
+            link.set(Rivencraft.LINK_BOOK_TARGET.get(), target);
+            link.set(Rivencraft.LINK_DESTINATION_NAME.get(), net.dnorberg.rivencraft.item.LinkingBookItem.destinationName(namedLevel));
+            if (!net.dnorberg.rivencraft.item.LinkingBookItem.destinationName(link, target).getString().equals("Crystal Garden's Dawn"))
+                throw new IllegalStateException("Link destination label ignored saved name");
+            var mode = net.dnorberg.rivencraft.PortConfig.RETURN_LINK_MODE.get();
+            player.getInventory().clearContent();
+            try {
+                net.dnorberg.rivencraft.PortConfig.RETURN_LINK_MODE.set(net.dnorberg.rivencraft.PortConfig.ReturnLinkMode.ALWAYS);
+                PortReturnLinks.afterSuccessfulTravel(player, ageId, target);
+                var returned = java.util.stream.IntStream.range(0, player.getInventory().getContainerSize())
+                        .mapToObj(i -> player.getInventory().getItem(i)).filter(i -> i.is(Rivencraft.LINKING_BOOK.get()))
+                        .findFirst().orElseThrow();
+                if (!"Crystal Garden's Dawn".equals(returned.get(Rivencraft.LINK_DESTINATION_NAME.get())))
+                    throw new IllegalStateException("Automatic Return Link lost departure name");
+                chest.setItem(4, returned.copy());
+            } finally { net.dnorberg.rivencraft.PortConfig.RETURN_LINK_MODE.set(mode); }
+            chest.setItem(3, link);
+            chest.setItem(2, book.copy());
+            menu.setCarried(ItemStack.EMPTY);
+        } finally { player.getInventory().clearContent(); }
+        verify(level);
+    }
+
+    static void verify(ServerLevel level) {
+        if (!(level.getBlockEntity(CHEST) instanceof Container chest)) throw new IllegalStateException("Fixture chest missing");
+        if (!chest.getItem(0).is(Rivencraft.COLLATION_FOLDER.get()) || !chest.getItem(1).is(Rivencraft.NOTEBOOK.get()))
+            throw new IllegalStateException("Empty collection covers were not preserved");
+        for (int i = 0; i < 2; i++) if (chest.getItem(i).get(Rivencraft.NOTEBOOK_CONTENTS.get()).pageCount() != 0)
+            throw new IllegalStateException("Imported pages remained in a collection");
+        if (!"RivenBinderProbe".equals(chest.getItem(2).get(Rivencraft.BOOK_AUTHOR.get())))
+            throw new IllegalStateException("Authored book lost its author");
+        var ageId = chest.getItem(2).get(Rivencraft.AGE_BOOK_ID.get());
+        if (!RuntimeAgeBackend.savedAgeName(level.getServer(), ageId).orElseThrow().equals("Crystal Garden's Dawn")
+                || !"Crystal Garden's Dawn".equals(chest.getItem(3).get(Rivencraft.LINK_DESTINATION_NAME.get()))
+                || !"Crystal Garden's Dawn".equals(chest.getItem(4).get(Rivencraft.LINK_DESTINATION_NAME.get())))
+            throw new IllegalStateException("Age/Linking/Return destination names did not survive persistence");
+        var old = new ItemStack(Rivencraft.LINKING_BOOK.get());
+        var overworld = new net.dnorberg.rivencraft.item.LinkBookTarget(net.minecraft.world.level.Level.OVERWORLD.identifier(), 0, 64, 0, 0, 0);
+        if (!net.dnorberg.rivencraft.item.LinkingBookItem.destinationName(old, overworld).getString()
+                .equals(net.minecraft.network.chat.Component.translatable("dimension.minecraft.overworld").getString()))
+            throw new IllegalStateException("Older book vanilla name fallback changed");
+        if (!EXPECTED.equals(chest.getItem(2).get(Rivencraft.BOOK_SYMBOLS.get())))
+            throw new IllegalStateException("Authored book page order was not preserved");
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortBiomeMaterialRules.java

@@ -16,12 +16,18 @@ final class PortBiomeMaterialRules {
     static Holder<NoiseGeneratorSettings> apply(HolderLookup.Provider registries, NoiseGeneratorSettings base) {
         var biomes = registries.lookupOrThrow(Registries.BIOME);
         var rules = registries.lookupOrThrow(Registries.MATERIAL_RULE);
+        var nether = java.util.stream.Stream.concat(java.util.stream.Stream.of(Biomes.NETHER_WASTES,
+                        Biomes.SOUL_SAND_VALLEY, Biomes.CRIMSON_FOREST, Biomes.WARPED_FOREST, Biomes.BASALT_DELTAS),
+                net.dnorberg.rivencraft.compat.TerraBlenderBiomes.nether(registries).stream()
+                        .map(id -> net.minecraft.resources.ResourceKey.create(Registries.BIOME, id)))
+                .distinct().toList();
+        @SuppressWarnings("unchecked")
+        net.minecraft.resources.ResourceKey<net.minecraft.world.level.biome.Biome>[] netherKeys = nether.toArray(net.minecraft.resources.ResourceKey[]::new);
         var materials = MaterialRules.sequence(
                 MaterialRules.ifTrue(MaterialRules.isBiome(biomes, Biomes.THE_END, Biomes.END_HIGHLANDS,
                         Biomes.END_MIDLANDS, Biomes.SMALL_END_ISLANDS, Biomes.END_BARRENS),
                         MaterialRules.getRule(rules, EndMaterialRules.END)),
-                MaterialRules.ifTrue(MaterialRules.isBiome(biomes, Biomes.NETHER_WASTES, Biomes.SOUL_SAND_VALLEY,
-                        Biomes.CRIMSON_FOREST, Biomes.WARPED_FOREST, Biomes.BASALT_DELTAS),
+                MaterialRules.ifTrue(MaterialRules.isBiome(biomes, netherKeys),
                         MaterialRules.getRule(rules, NetherMaterialRules.NETHER)),
                 base.materialRule().value());
         return Holder.direct(new NoiseGeneratorSettings(base.noiseSettings(), base.defaultBlock(), base.defaultFluid(),

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortBiomePlan.java

@@ -5,7 +5,7 @@ import com.mojang.serialization.codecs.RecordCodecBuilder;
 import java.util.List;
 import net.minecraft.resources.Identifier;
 
-/** Frozen authored biome choice; repeated entries retain their selection weight. */
+/** Frozen biome choice; Native may carry an explicit Cave pool. Repeats retain weight. */
 public record PortBiomePlan(Distribution distribution, List<Identifier> biomes) {
     public enum Distribution { NATIVE, SINGLE, TILED, GRID, TINY, SMALL, MEDIUM, LARGE, HUGE }
 
@@ -17,8 +17,7 @@ public record PortBiomePlan(Distribution distribution, List<Identifier> biomes)
 
     public PortBiomePlan {
         biomes = List.copyOf(biomes);
-        if (distribution == Distribution.NATIVE && !biomes.isEmpty()
-                || distribution == Distribution.SINGLE && biomes.size() != 1
+        if (distribution == null || distribution == Distribution.SINGLE && biomes.size() != 1
                 || distribution != Distribution.NATIVE && distribution != Distribution.SINGLE && biomes.size() < 2)
             throw new IllegalArgumentException("Invalid authored biome distribution");
     }

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortBlockInstability.java

@@ -0,0 +1,314 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import net.dnorberg.rivencraft.Rivencraft;
+
+import net.dnorberg.rivencraft.writing.PortRegistryPages;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.chunk.status.ChunkStatus;
+import net.neoforged.neoforge.common.Tags;
+import net.neoforged.neoforge.event.level.ChunkEvent;
+import net.neoforged.neoforge.event.server.ServerStoppingEvent;
+import net.neoforged.neoforge.event.tick.ServerTickEvent;
+
+/** Legacy-style excess-block profiling with gradual spawn-area generation. */
+@net.neoforged.fml.common.EventBusSubscriber(modid = Rivencraft.MOD_ID)
+public final class PortBlockInstability {
+    // Legacy's watched blocks and factor-1 values; modern ore variants share their parent weight.
+    // Storage blocks are deliberate extensions, including the requested diamond-block case.
+    private static final Map<Identifier, Double> VANILLA_WEIGHTS = weights();
+    private static final Map<String, Double> COMMON_MINERAL_WEIGHTS = Map.ofEntries(
+            Map.entry("coal", 5.0), Map.entry("sulfur", 5.0), Map.entry("sulphur", 5.0),
+            Map.entry("salt", 5.0), Map.entry("tin", 60.0), Map.entry("lead", 60.0),
+            Map.entry("aluminum", 60.0), Map.entry("aluminium", 60.0),
+            Map.entry("zinc", 60.0), Map.entry("copper", 60.0),
+            Map.entry("iron", 60.0), Map.entry("nickel", 200.0),
+            Map.entry("osmium", 200.0), Map.entry("silver", 200.0),
+            Map.entry("emerald", 200.0), Map.entry("ruby", 200.0),
+            Map.entry("sapphire", 200.0), Map.entry("redstone", 250.0),
+            Map.entry("gold", 750.0), Map.entry("uranium", 750.0),
+            Map.entry("platinum", 750.0), Map.entry("diamond", 4000.0),
+            Map.entry("iridium", 4000.0), Map.entry("netherite", 8000.0));
+    private static final int MAX_PENDING = 2048;
+    private static final int SAMPLES_PER_TICK = 4;
+    private static final int GENERATION_INTERVAL_TICKS = 20;
+    private static final List<ChunkPos> SPAWN_OFFSETS = spawnOffsets();
+    private static final Map<MinecraftServer, ArrayDeque<Pending>> PENDING = new java.util.WeakHashMap<>();
+    private static final Map<MinecraftServer, Map<Identifier, Integer>> NEXT_SPAWN_SAMPLE =
+            new java.util.WeakHashMap<>();
+    private static final Map<MinecraftServer, Integer> NEXT_TARGET = new java.util.WeakHashMap<>();
+    private static final Map<MinecraftServer, Boolean> GENERATION_IN_FLIGHT =
+            new java.util.WeakHashMap<>();
+
+    private PortBlockInstability() {}
+
+    /** Track recognized materials from installed mods without requiring any mod-specific API. */
+    static boolean tracked(Identifier id) {
+        if (VANILLA_WEIGHTS.containsKey(id)) return true;
+        if (id.getNamespace().equals("minecraft") || id.getNamespace().equals("rivencraft")) return false;
+        if (!BuiltInRegistries.BLOCK.containsKey(id)) return false;
+        var block = BuiltInRegistries.BLOCK.getValue(id);
+        return eligibleMaterial(block) && (configuredOverride(id) != null || inferredModdedWeight(id, block) > 0);
+    }
+
+    static double weight(Identifier id) {
+        Double vanilla = VANILLA_WEIGHTS.get(id);
+        if (vanilla != null) return vanilla;
+        if (id.getNamespace().equals("minecraft") || id.getNamespace().equals("rivencraft")
+                || !BuiltInRegistries.BLOCK.containsKey(id)) return 0;
+        var block = BuiltInRegistries.BLOCK.getValue(id);
+        if (!eligibleMaterial(block)) return 0;
+        return moddedWeight(id, inferredModdedWeight(id, block),
+                PortInstabilityConfig.moddedMaterialOverrides());
+    }
+
+    private static boolean eligibleMaterial(net.minecraft.world.level.block.Block block) {
+        return PortRegistryPages.materialCategory(block) != null;
+    }
+
+    private static Double configuredOverride(Identifier id) {
+        return configuredOverride(id, PortInstabilityConfig.moddedMaterialOverrides());
+    }
+
+    private static Double configuredOverride(Identifier id, List<? extends String> overrides) {
+        for (String entry : overrides) {
+            int separator = entry.lastIndexOf('=');
+            if (separator > 0 && entry.substring(0, separator).equals(id.toString()))
+                return (double) Integer.parseInt(entry.substring(separator + 1));
+        }
+        return null;
+    }
+
+    static double moddedWeight(Identifier id, double inferred, List<? extends String> overrides) {
+        Double override = configuredOverride(id, overrides);
+        return override == null ? inferred : override;
+    }
+
+    private static double inferredModdedWeight(Identifier id, net.minecraft.world.level.block.Block block) {
+        if ("rivencraft:fluid".equals(PortRegistryPages.materialCategory(block))) return 1.25;
+        var state = block.defaultBlockState();
+        String path = id.getPath();
+        boolean ore = state.is(Tags.BlockItems.ORES.block()) || path.endsWith("_ore") || path.contains("_ore_");
+        boolean storage = state.is(Tags.BlockItems.STORAGE_BLOCKS.block())
+                || (path.endsWith("_block") || path.startsWith("block_of_"))
+                && namedMineralWeight(path) != null;
+        return inferredModdedWeight(id, ore, storage, false);
+    }
+
+    static double inferredModdedWeight(Identifier id, boolean ore, boolean storage, boolean fluid) {
+        if (fluid) return 1.25;
+        Double named = namedMineralWeight(id.getPath());
+        if (ore) return named == null ? 60.0 : named;
+        if (storage) return named == null ? 120.0 : named;
+        return 0;
+    }
+
+    private static Double namedMineralWeight(String path) {
+        for (String part : path.split("[/_]")) {
+            Double value = COMMON_MINERAL_WEIGHTS.get(part);
+            if (value != null) return value;
+        }
+        return null;
+    }
+
+    @net.neoforged.bus.api.SubscribeEvent
+    public static void onChunkLoad(ChunkEvent.Load event) {
+        if (!(event.getLevel() instanceof ServerLevel level)
+                || !(event.getChunk() instanceof LevelChunk chunk)) return;
+        boolean overworld = level.dimension() == net.minecraft.world.level.Level.OVERWORLD;
+        if (!overworld && !PortInstabilityRuntime.isAge(level)) return;
+        // Chunk-load callbacks can occur while chunk storage is updating. Defer saved-data
+        // access to a bounded server-tick lane to avoid reentering that storage path.
+        synchronized (PENDING) {
+            var queue = PENDING.computeIfAbsent(level.getServer(), ignored -> new ArrayDeque<>());
+            if (queue.size() < MAX_PENDING) queue.addLast(new Pending(level, chunk));
+        }
+    }
+
+    @net.neoforged.bus.api.SubscribeEvent
+    public static void onServerTickPost(ServerTickEvent.Post event) {
+        for (int index = 0; index < SAMPLES_PER_TICK; index++) {
+            Pending pending;
+            synchronized (PENDING) {
+                var queue = PENDING.get(event.getServer());
+                pending = queue == null ? null : queue.pollFirst();
+            }
+            if (pending == null) break;
+            var pos = pending.chunk().getPos();
+            if (pending.level().getServer().getLevel(pending.level().dimension()) == pending.level()
+                    && pending.level().getChunkSource().getChunkNow(pos.x(), pos.z()) == pending.chunk())
+                PortBlockProfileSavedData.get(pending.level()).sample(pending.chunk());
+        }
+        if (event.getServer().getTickCount() % GENERATION_INTERVAL_TICKS == 0) {
+            generateNextSpawnSample(event.getServer());
+        }
+    }
+
+    @net.neoforged.bus.api.SubscribeEvent
+    public static void onServerStopping(ServerStoppingEvent event) {
+        synchronized (PENDING) { PENDING.remove(event.getServer()); }
+        NEXT_SPAWN_SAMPLE.remove(event.getServer());
+        NEXT_TARGET.remove(event.getServer());
+        GENERATION_IN_FLIGHT.remove(event.getServer());
+    }
+
+    /** Generate at most one chunk per second across the active Age and its Overworld baseline. */
+    private static void generateNextSpawnSample(MinecraftServer server) {
+        if (GENERATION_IN_FLIGHT.containsKey(server)) return;
+        List<SampleTarget> targets = new ArrayList<>();
+        for (ServerLevel level : server.getAllLevels()) {
+            if (!PortInstabilityRuntime.isAge(level)
+                    || level.players().isEmpty()) continue;
+            var data = PortInstabilityData.get(server);
+            if (!data.supportsProfiling(level)) continue;
+            var age = data.age(level);
+            targets.add(new SampleTarget(level, age.spawn().orElseGet(() -> level.getRespawnData().pos()),
+                    PortBlockProfileSavedData.MIN_AGE_SAMPLES));
+        }
+        if (targets.isEmpty()) return;
+        ServerLevel overworld = server.overworld();
+        targets.add(0, new SampleTarget(overworld, overworld.getRespawnData().pos(),
+                PortBlockProfileSavedData.MIN_BASELINE_SAMPLES));
+        int first = Math.floorMod(NEXT_TARGET.getOrDefault(server, 0), targets.size());
+        for (int offset = 0; offset < targets.size(); offset++) {
+            int index = (first + offset) % targets.size();
+            SampleTarget target = targets.get(index);
+            if (generateNextSpawnSample(target.level(), target.origin(), target.minimum(), server)) {
+                NEXT_TARGET.put(server, index + 1);
+                return;
+            }
+        }
+    }
+
+    private static boolean generateNextSpawnSample(ServerLevel level, net.minecraft.core.BlockPos origin,
+                                                   int minimum, MinecraftServer server) {
+        PortBlockProfileSavedData profile = PortBlockProfileSavedData.get(level);
+        if (profile.count() >= minimum) return false;
+        Map<Identifier, Integer> cursors = NEXT_SPAWN_SAMPLE.computeIfAbsent(server,
+                ignored -> new HashMap<>());
+        Identifier dimension = level.dimension().identifier();
+        int index = cursors.getOrDefault(dimension, 0);
+        ChunkPos center = ChunkPos.containing(origin);
+        while (index < SPAWN_OFFSETS.size()) {
+            ChunkPos offset = SPAWN_OFFSETS.get(index++);
+            ChunkPos target = new ChunkPos(center.x() + offset.x(), center.z() + offset.z());
+            if (profile.contains(target)) continue;
+            cursors.put(dimension, index);
+            GENERATION_IN_FLIGHT.put(server, true);
+            // getChunkFuture blocks when called on the server thread. Its off-thread
+            // path schedules generation on Minecraft's chunk executor instead.
+            CompletableFuture.supplyAsync(() -> level.getChunkSource()
+                            .getChunkFuture(target.x(), target.z(), ChunkStatus.FULL, true))
+                    .thenCompose(future -> future)
+                    .whenComplete((result, error) -> {
+                        if (server.isStopped()) return;
+                        server.execute(() -> {
+                            if (GENERATION_IN_FLIGHT.remove(server) == null) return;
+                            if (error != null) {
+                                Rivencraft.LOGGER.warn("Could not profile chunk {} in {}", target, dimension, error);
+                            } else if (server.getLevel(level.dimension()) == level
+                                    && result.orElse(null) instanceof LevelChunk chunk) {
+                                profile.sample(chunk);
+                            }
+                        });
+                    });
+            return true;
+        }
+        return false;
+    }
+
+    private static List<ChunkPos> spawnOffsets() {
+        List<ChunkPos> offsets = new ArrayList<>(PortBlockProfileSavedData.MAX_SAMPLES);
+        offsets.add(new ChunkPos(0, 0));
+        for (int radius = 1; offsets.size() < PortBlockProfileSavedData.MAX_SAMPLES; radius++) {
+            for (int x = -radius; x <= radius; x++) {
+                offsets.add(new ChunkPos(x, -radius));
+                offsets.add(new ChunkPos(x, radius));
+            }
+            for (int z = -radius + 1; z < radius; z++) {
+                offsets.add(new ChunkPos(-radius, z));
+                offsets.add(new ChunkPos(radius, z));
+            }
+        }
+        return List.copyOf(offsets.subList(0, PortBlockProfileSavedData.MAX_SAMPLES));
+    }
+
+    /** Zero until the Age exceeds 400 samples and the baseline reaches 500. */
+    static int score(PortBlockProfileSavedData age, PortBlockProfileSavedData baseline) {
+        return score(age.totals(), age.count(), baseline.totals(), baseline.count());
+    }
+
+    static int score(Map<Identifier, Long> age, int ageChunks,
+                     Map<Identifier, Long> baseline, int baselineChunks) {
+        if (ageChunks < PortBlockProfileSavedData.MIN_AGE_SAMPLES
+                || baselineChunks < PortBlockProfileSavedData.MIN_BASELINE_SAMPLES) return 0;
+        double result = 0;
+        Set<Identifier> watched = new HashSet<>(age.keySet());
+        watched.addAll(baseline.keySet());
+        for (Identifier id : watched) {
+            double weight = weight(id);
+            if (weight <= 0) continue;
+            double excess = age.getOrDefault(id, 0L) / (double) ageChunks
+                    - 1.05 * baseline.getOrDefault(id, 0L) / (double) baselineChunks;
+            if (excess > 0) result += excess * weight;
+        }
+        return (int) Math.min(100_000, Math.round(result));
+    }
+
+    public static int score(ServerLevel level) {
+        if (!PortInstabilityRuntime.isAge(level) || !PortInstabilityData.get(level.getServer()).supportsProfiling(level)) return 0;
+        return score(PortBlockProfileSavedData.get(level), PortBlockProfileSavedData.get(level.getServer().overworld()));
+    }
+    public static int sampledChunks(ServerLevel level) { return PortBlockProfileSavedData.get(level).count(); }
+
+    public static int difficultyScore(long rawScore, int difficulty) {
+        double multiplier = switch (difficulty) {
+            case 0 -> 0.25;
+            case 1 -> 0.5;
+            case 2 -> 1.0;
+            case 3 -> 1.75;
+            default -> throw new IllegalArgumentException("Unknown instability difficulty " + difficulty);
+        };
+        return (int) Math.min(Integer.MAX_VALUE, Math.max(0, rawScore * multiplier));
+    }
+
+    private static Map<Identifier, Double> weights() {
+        Map<Identifier, Double> values = new HashMap<>();
+        add(values, 5, "coal_ore", "deepslate_coal_ore", "lapis_ore", "deepslate_lapis_ore");
+        add(values, 60, "iron_ore", "deepslate_iron_ore");
+        add(values, 200, "emerald_ore", "deepslate_emerald_ore");
+        add(values, 250, "redstone_ore", "deepslate_redstone_ore");
+        add(values, 750, "gold_ore", "deepslate_gold_ore");
+        add(values, 4000, "diamond_ore", "deepslate_diamond_ore", "diamond_block");
+        add(values, 20, "nether_quartz_ore");
+        add(values, 50, "glowstone");
+        values.put(Identifier.parse("rivencraft:crystal_block"), 20.0);
+        // Valuable blocks introduced after Legacy, and storage forms authorable in Rivencraft.
+        add(values, 200, "emerald_block");
+        add(values, 750, "gold_block", "raw_gold_block");
+        add(values, 4000, "ancient_debris");
+        add(values, 60, "iron_block", "raw_iron_block");
+        add(values, 8000, "netherite_block");
+        return Map.copyOf(values);
+    }
+
+    private static void add(Map<Identifier, Double> values, int weight, String... paths) {
+        for (String path : paths) values.put(Identifier.withDefaultNamespace(path), (double) weight);
+    }
+
+    private record Pending(ServerLevel level, LevelChunk chunk) {}
+
+    private record SampleTarget(ServerLevel level, net.minecraft.core.BlockPos origin, int minimum) {}
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortBlockProfileSavedData.java

@@ -0,0 +1,63 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Persistent generated-chunk snapshots. Each chunk is counted once, up to the 1.21.1 cap. */
+final class PortBlockProfileSavedData extends SavedData {
+    static final int MIN_AGE_SAMPLES = 401, MIN_BASELINE_SAMPLES = 500, MAX_SAMPLES = 1024;
+    private static final int VERSION = 2;
+    private record Sample(long chunk, Map<Identifier, Integer> counts) {
+        private static final Codec<Sample> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+                Codec.LONG.fieldOf("chunk").forGetter(Sample::chunk),
+                Codec.unboundedMap(Identifier.CODEC, Codec.intRange(1, Integer.MAX_VALUE))
+                        .fieldOf("blocks").forGetter(Sample::counts)
+        ).apply(instance, Sample::new));
+    }
+    private static final Codec<PortBlockProfileSavedData> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Codec.INT.fieldOf("version").forGetter(data -> VERSION),
+            Sample.CODEC.listOf(0, MAX_SAMPLES).fieldOf("samples").forGetter(data -> data.samples.entrySet().stream()
+                    .map(entry -> new Sample(entry.getKey(), entry.getValue())).toList())
+    ).apply(instance, PortBlockProfileSavedData::new));
+    private static final SavedDataType<PortBlockProfileSavedData> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "block_profile"),
+            () -> new PortBlockProfileSavedData(VERSION, List.of()), CODEC);
+    private final Map<Long, Map<Identifier, Integer>> samples = new HashMap<>();
+    private final Map<Identifier, Long> totals = new HashMap<>();
+    private PortBlockProfileSavedData(int version, List<Sample> values) {
+        if (version == VERSION) for (var value : values) put(value.chunk(), value.counts());
+    }
+    static PortBlockProfileSavedData get(ServerLevel level) { return level.getDataStorage().computeIfAbsent(TYPE); }
+    int count() { return samples.size(); }
+    boolean contains(ChunkPos pos) { return samples.containsKey(pos.pack()); }
+    Map<Identifier, Long> totals() { return Map.copyOf(totals); }
+    boolean sample(LevelChunk chunk) {
+        if (count() >= MAX_SAMPLES || contains(chunk.getPos())) return false;
+        Map<Identifier, Integer> counts = new HashMap<>();
+        for (var section : chunk.getSections()) {
+            if (section.hasOnlyAir()) continue;
+            section.getStates().count((state, amount) -> {
+                Identifier id = BuiltInRegistries.BLOCK.getKey(state.getBlock());
+                if (PortBlockInstability.tracked(id)) counts.merge(id, amount, Integer::sum);
+            });
+        }
+        put(chunk.getPos().pack(), counts);
+        setDirty();
+        return true;
+    }
+    private void put(long pos, Map<Identifier, Integer> counts) {
+        if (count() >= MAX_SAMPLES || samples.containsKey(pos)) return;
+        samples.put(pos, Map.copyOf(counts));
+        counts.forEach((id, amount) -> totals.merge(id, amount.longValue(), Long::sum));
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortBookDropConversionProbe.java

@@ -0,0 +1,110 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import java.util.UUID;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.entity.DroppedBookEntity;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.TickTask;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.ProblemReporter;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.storage.TagValueOutput;
+import net.minecraft.world.phys.AABB;
+import net.minecraft.world.phys.Vec3;
+
+/** Join conversion runs on queued server tasks: create and inspect on separate commands. */
+final class PortBookDropConversionProbe {
+    private static final UUID OWNER = UUID.fromString("cc5909e5-aafa-43d6-b841-a917ec9c0115");
+    private static final AABB AREA = new AABB(-16, -64, -16, 32, 320, 32);
+    private static ItemStack book(boolean descriptive, String label) {
+        var stack = new ItemStack(descriptive ? Rivencraft.DESCRIPTIVE_BOOK.get() : Rivencraft.LINKING_BOOK.get());
+        stack.set(DataComponents.CUSTOM_NAME, Component.literal(label));
+        return stack;
+    }
+    static void create(ServerLevel level) {
+        for (int x = 0; x < 16; x++) for (int z = 0; z < 16; z++) level.setBlock(new BlockPos(x, 63, z), Blocks.STONE.defaultBlockState(), 2);
+        var player = net.neoforged.neoforge.common.util.FakePlayerFactory.get(level,
+                new com.mojang.authlib.GameProfile(UUID.fromString("84f38604-48fe-48d3-a4fb-f858a7200115"), "RivenDropProbe"));
+        player.setPos(8.5, 64, 8.5);
+        // Test exact factory state before physics can advance position or pickup timers.
+        var sample = new ItemEntity(level, 8.5, 66, 8.5, book(false, "state_copy"));
+        sample.getItem().set(Rivencraft.LINK_BOOK_TARGET.get(), new net.dnorberg.rivencraft.item.LinkBookTarget(
+                level.dimension().identifier(), -0.5, 64, -1.25, 135, -20));
+        sample.getItem().set(Rivencraft.LINK_DESTINATION_NAME.get(), "Named destination");
+        sample.getItem().set(Rivencraft.LINK_PROPERTIES.get(), new net.dnorberg.rivencraft.item.LinkProperties(net.dnorberg.rivencraft.item.LinkProperties.DISARM
+                | net.dnorberg.rivencraft.item.LinkProperties.MAINTAIN_MOMENTUM));
+        sample.setTarget(OWNER);
+        sample.setThrower(player);
+        sample.setPickUpDelay(80);
+        sample.setDeltaMovement(new Vec3(0.2, 0.1, -0.3));
+        sample.setYRot(37);
+        sample.setXRot(12);
+        sample.setNoGravity(true);
+        var copy = DroppedBookEntity.fromDrop(sample);
+        if (!copy.position().equals(sample.position()) || !copy.getDeltaMovement().equals(sample.getDeltaMovement())
+                || copy.getYRot() != 37 || copy.getXRot() != 12 || !copy.isNoGravity()
+                || !ItemStack.matches(copy.getItem(), sample.getItem()) || !OWNER.equals(copy.getTarget())
+                || copy.getUUID().equals(sample.getUUID()) || copy.getAge() != -32768)
+            throw new IllegalStateException("Drop conversion lost placement, ownership or item components");
+        var originalTag = TagValueOutput.createWithContext(ProblemReporter.DISCARDING, level.registryAccess());
+        var copiedTag = TagValueOutput.createWithContext(ProblemReporter.DISCARDING, level.registryAccess());
+        sample.saveWithoutId(originalTag); copy.saveWithoutId(copiedTag);
+        for (String key : List.of("PickupDelay", "Owner", "Thrower", "Item"))
+            if (!java.util.Objects.equals(originalTag.buildResult().get(key), copiedTag.buildResult().get(key)))
+                throw new IllegalStateException("Drop conversion lost metadata: " + key);
+        // Four ordinary book variants must all convert through the actual event route.
+        for (String name : List.of("manual_link", "manual_description", "unwritten_link", "unwritten_description")) {
+            var stack = book(name.endsWith("description"), name);
+            if (name.equals("manual_link")) {
+                stack.set(Rivencraft.LINK_BOOK_TARGET.get(), sample.getItem().get(Rivencraft.LINK_BOOK_TARGET.get()));
+                stack.set(Rivencraft.LINK_DESTINATION_NAME.get(), "Named destination");
+            }
+            if (name.equals("manual_description")) stack.set(Rivencraft.AGE_BOOK_ID.get(), level.dimension().identifier());
+            var item = new ItemEntity(level, 8.5, 66, 8.5, stack);
+            item.setNoGravity(true); item.setDeltaMovement(Vec3.ZERO); item.setTarget(OWNER);
+            level.addFreshEntity(item);
+        }
+        player.drop(book(false, "player_toss"), false, net.minecraft.util.Prediction.SERVER_ONLY);
+        net.minecraft.world.Containers.dropItemStack(level, 8.5, 65, 8.5, book(true, "container"));
+        var standPos = new BlockPos(10, 64, 8);
+        level.setBlock(standPos, Rivencraft.BOOK_STAND.get().defaultBlockState(), 3);
+        ((net.dnorberg.rivencraft.block.entity.BookStandBlockEntity) level.getBlockEntity(standPos)).setBook(book(false, "stand"));
+        level.destroyBlock(standPos, true);
+        var custom = new DroppedBookEntity(level, new Vec3(8.5, 66, 8.5), book(false, "already_custom"));
+        custom.setNoGravity(true);
+        level.addFreshEntity(custom);
+        level.addFreshEntity(new ItemEntity(level, 8.5, 66, 8.5, net.dnorberg.rivencraft.item.PageItem.createLinkPanelPage()));
+        java.util.function.Consumer<net.neoforged.neoforge.event.entity.EntityJoinLevelEvent> cancel = event -> {
+            if (event.getLevel() == level && event.getEntity() instanceof DroppedBookEntity dropped
+                    && dropped.getItem().getHoverName().getString().equals("cancel_preserve")) event.setCanceled(true);
+        };
+        net.neoforged.neoforge.common.NeoForge.EVENT_BUS.addListener(cancel);
+        try {
+            var item = new ItemEntity(level, 8.5, 66, 8.5, book(false, "cancel_preserve"));
+            item.setNoGravity(true); item.setDeltaMovement(Vec3.ZERO);
+            level.addFreshEntity(item);
+        } finally {
+            // Queued after that source's conversion task; no fixture listener remains installed.
+            level.getServer().schedule(new TickTask(0, () -> net.neoforged.neoforge.common.NeoForge.EVENT_BUS.unregister(cancel)));
+        }
+    }
+    static void verify(ServerLevel level) {
+        var drops = level.getEntitiesOfClass(ItemEntity.class, AREA);
+        for (String name : List.of("manual_link", "manual_description", "unwritten_link", "unwritten_description",
+                "player_toss", "container", "stand", "already_custom", "cancel_preserve")) {
+            var found = drops.stream().filter(e -> e.getItem().getHoverName().getString().equals(name)).toList();
+            if (found.size() != 1 || !name.equals("cancel_preserve") && !(found.getFirst() instanceof DroppedBookEntity))
+                throw new IllegalStateException("Expected one open book for " + name + ", found " + found.size());
+        }
+        var named = drops.stream().filter(e -> e.getItem().getHoverName().getString().equals("manual_link")).findFirst().orElseThrow();
+        if (!OWNER.equals(named.getTarget()) || !"Named destination".equals(named.getItem().get(Rivencraft.LINK_DESTINATION_NAME.get())))
+            throw new IllegalStateException("Converted book lost owner or destination");
+        if (drops.stream().filter(e -> e.getItem().is(Rivencraft.PAGE.get())).anyMatch(e -> e instanceof DroppedBookEntity))
+            throw new IllegalStateException("Non-book item was converted");
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortBookStandProbe.java

@@ -0,0 +1,93 @@
+package net.dnorberg.rivencraft.age;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.BookStandBlock;
+import net.dnorberg.rivencraft.block.entity.BookStandBlockEntity;
+import net.dnorberg.rivencraft.event.BookStandConversionHandler;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.network.PortBookNetworking;
+import net.dnorberg.rivencraft.network.UseBookStandPayload;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.LecternBlock;
+import net.minecraft.world.phys.BlockHitResult;
+import net.minecraft.world.phys.Vec3;
+
+/** Isolated conversion, ownership, stale-screen and persistence checks. */
+final class PortBookStandProbe {
+    private static final BlockPos POS = new BlockPos(0, 64, 0);
+    static void create(ServerLevel level) {
+        var player = net.neoforged.neoforge.common.util.FakePlayerFactory.get(level,
+                new com.mojang.authlib.GameProfile(java.util.UUID.fromString("a5c323a1-3b58-4dd6-927f-e08000800110"), "RivenStandProbe"));
+        player.setPos(0.5, 64, 2.5);
+        try {
+            for (Direction facing : Direction.Plane.HORIZONTAL) for (InteractionHand hand : InteractionHand.values())
+                for (var sample : java.util.List.of(new ItemStack(Rivencraft.LINKING_BOOK.get()),
+                        new ItemStack(Rivencraft.DESCRIPTIVE_BOOK.get()), PageItem.createLinkPanelPage().copyWithCount(3))) {
+                    level.setBlock(POS, Blocks.LECTERN.defaultBlockState().setValue(LecternBlock.FACING, facing), 3);
+                    player.setItemInHand(hand, sample.copy());
+                    if (!BookStandConversionHandler.convert(player, hand, POS)) throw new IllegalStateException("Conversion failed");
+                    var stand = (BookStandBlockEntity) level.getBlockEntity(POS);
+                    var stored = sample.copyWithCount(1);
+                    if (!ItemStack.matches(stand.getBook(), stored) || player.getItemInHand(hand).getCount() != sample.getCount() - 1
+                            || stand.getBlockState().getValue(BookStandBlock.FACING) != facing)
+                        throw new IllegalStateException("Conversion lost ownership or facing");
+                    var packet = new UseBookStandPayload(level.dimension().identifier(), POS, stored.copy());
+                    if (PortBookNetworking.validatedStandBook(player, packet).isEmpty()) throw new IllegalStateException("Valid source rejected");
+                    player.setPos(100, 64, 100);
+                    if (!PortBookNetworking.validatedStandBook(player, packet).isEmpty()) throw new IllegalStateException("Distant source accepted");
+                    player.setPos(0.5, 64, 2.5);
+                    if (!PortBookNetworking.validatedStandBook(player, new UseBookStandPayload(
+                            net.minecraft.resources.Identifier.fromNamespaceAndPath("minecraft", "overworld"), POS, stored)).isEmpty())
+                        throw new IllegalStateException("Wrong dimension accepted");
+                    if (!PortBookNetworking.validatedStandBook(player, new UseBookStandPayload(packet.dimension(), POS, new ItemStack(Items.DIRT))).isEmpty())
+                        throw new IllegalStateException("Replaced book accepted");
+                    var loaded = net.minecraft.world.level.block.entity.BlockEntity.loadStatic(POS, stand.getBlockState(),
+                            stand.saveWithFullMetadata(level.registryAccess()), level.registryAccess());
+                    if (!(loaded instanceof BookStandBlockEntity copy) || !ItemStack.matches(copy.getBook(), stored))
+                        throw new IllegalStateException("Stand serialization lost content");
+                    player.getInventory().clearContent();
+                    player.setShiftKeyDown(true);
+                    stand.getBlockState().useWithoutItem(level, player, new BlockHitResult(Vec3.atCenterOf(POS), Direction.UP, POS, false));
+                    player.setShiftKeyDown(false);
+                    if (!level.getBlockState(POS).is(Blocks.LECTERN)
+                            || level.getBlockState(POS).getValue(LecternBlock.FACING) != facing
+                            || player.getInventory().countItem(stored.getItem()) != 1
+                            || !PortBookNetworking.validatedStandBook(player, packet).isEmpty())
+                        throw new IllegalStateException("Retrieval did not restore lectern or recover item exactly once");
+                    player.getInventory().clearContent();
+                    player.setItemInHand(hand, stored.copy());
+                    BookStandConversionHandler.convert(player, hand, POS);
+                    level.destroyBlock(POS, true);
+                    var drops = level.getEntitiesOfClass(net.minecraft.world.entity.item.ItemEntity.class,
+                            new net.minecraft.world.phys.AABB(-2, 62, -2, 3, 68, 3));
+                    int items = drops.stream().filter(e -> e.getItem().is(stored.getItem())).mapToInt(e -> e.getItem().getCount()).sum();
+                    int lecterns = drops.stream().filter(e -> e.getItem().is(Items.LECTERN)).mapToInt(e -> e.getItem().getCount()).sum();
+                    if (items != 1 || lecterns != 1) throw new IllegalStateException("Break drops duplicated/lost: " + items + "/" + lecterns);
+                    drops.forEach(net.minecraft.world.entity.Entity::discard);
+                }
+            level.setBlock(POS, Blocks.LECTERN.defaultBlockState().setValue(LecternBlock.HAS_BOOK, true), 3);
+            player.setItemInHand(InteractionHand.MAIN_HAND, PageItem.createLinkPanelPage());
+            if (BookStandConversionHandler.convert(player, InteractionHand.MAIN_HAND, POS)) throw new IllegalStateException("Occupied lectern converted");
+            level.setBlock(POS, Blocks.LECTERN.defaultBlockState(), 3);
+            player.setItemInHand(InteractionHand.MAIN_HAND, new ItemStack(Items.DIRT));
+            if (BookStandConversionHandler.convert(player, InteractionHand.MAIN_HAND, POS)) throw new IllegalStateException("Unrelated item accepted");
+            var named = new ItemStack(Rivencraft.LINKING_BOOK.get());
+            named.set(net.minecraft.core.component.DataComponents.CUSTOM_NAME, net.minecraft.network.chat.Component.literal("Stand persistence"));
+            player.setItemInHand(InteractionHand.MAIN_HAND, named);
+            if (!BookStandConversionHandler.convert(player, InteractionHand.MAIN_HAND, POS)) throw new IllegalStateException("Final stand missing");
+        } finally { player.setShiftKeyDown(false); player.getInventory().clearContent(); }
+        verify(level);
+    }
+    static void verify(ServerLevel level) {
+        if (!(level.getBlockEntity(POS) instanceof BookStandBlockEntity stand)
+                || !stand.getBook().is(Rivencraft.LINKING_BOOK.get())
+                || !stand.getBook().getHoverName().getString().equals("Stand persistence"))
+            throw new IllegalStateException("Stand restart persistence failed");
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortCollectionExtrasProbe.java

@@ -0,0 +1,109 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.item.SymbolPortfolioItem;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.writing.PortSymbolPages;
+import net.minecraft.core.BlockPos;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.Container;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.phys.AABB;
+
+/** Disposable-world boundary, booster-use and persistence checks. */
+final class PortCollectionExtrasProbe {
+    private static final BlockPos CHEST = new BlockPos(0, 64, 0);
+    private PortCollectionExtrasProbe() {}
+    private static Identifier id(String path) { return Identifier.fromNamespaceAndPath("rivencraft", path); }
+    private static NotebookContents contents(ItemStack stack) { return stack.get(Rivencraft.NOTEBOOK_CONTENTS.get()); }
+    private static List<Identifier> symbols(ItemStack collection) {
+        return contents(collection).pages().stream().map(page -> page.get(Rivencraft.SYMBOL_PAGE_ID.get())).toList();
+    }
+    private static void folder(ItemStack stack) {
+        if (!stack.is(Rivencraft.COLLATION_FOLDER.get()) || contents(stack).pageCount() != 16
+                || symbols(stack).stream().anyMatch(id -> !PortSymbolPages.sealedCandidateIds().contains(id)))
+            throw new IllegalStateException("Sealed Notebook page pool/count regression");
+    }
+
+    static void create(ServerLevel level) {
+        PortAgeTravel.findLanding(level);
+        level.setBlock(CHEST, Blocks.CHEST.defaultBlockState(), 3);
+        var chest = (Container) level.getBlockEntity(CHEST);
+        var pages = new java.util.ArrayList<ItemStack>();
+        for (int i = 0; i < 253; i++) pages.add(PageItem.createSymbolPage(id(i % 2 == 0 ? "terrain/flat" : "weather/off")));
+        var volumes = SymbolPortfolioItem.createVolumes(id("feature"), pages);
+        if (volumes.size() != 2 || contents(volumes.get(0)).pageCount() != 252
+                || contents(volumes.get(1)).pageCount() != 1
+                || !volumes.stream().flatMap(volume -> symbols(volume).stream()).toList()
+                        .equals(pages.stream().map(page -> page.get(Rivencraft.SYMBOL_PAGE_ID.get())).toList())
+                || !SymbolPortfolioItem.createVolumes(id("feature"), List.of()).isEmpty())
+            throw new IllegalStateException("Portfolio volume boundary/order regression");
+        chest.setItem(0, volumes.get(0));
+        chest.setItem(1, volumes.get(1));
+        var actual = net.dnorberg.rivencraft.registry.ModCreativeTabs.creativeSymbolPortfolios(level.registryAccess());
+        var allPages = PortSymbolPages.categories().stream().flatMap(category -> PortSymbolPages.pages(category, level.registryAccess()).stream())
+                .map(page -> page.get(Rivencraft.SYMBOL_PAGE_ID.get())).toList();
+        if (!actual.stream().flatMap(volume -> symbols(volume).stream()).toList().equals(allPages))
+            throw new IllegalStateException("Creative portfolios omit/duplicate/reorder pages");
+        var player = net.neoforged.neoforge.common.util.FakePlayerFactory.get(level,
+                new com.mojang.authlib.GameProfile(java.util.UUID.fromString("790b69dd-b62b-45be-9017-caf16515169a"), "RivenExtrasProbe"));
+        player.setPos(0.5, 64, 2.5);
+        try {
+            player.getAbilities().instabuild = false;
+            player.getRandom().setSeed(105);
+            var first = net.dnorberg.rivencraft.item.SealedNotebookItem.open(player);
+            player.getRandom().setSeed(105);
+            var repeat = net.dnorberg.rivencraft.item.SealedNotebookItem.open(player);
+            folder(first);
+            if (!symbols(first).equals(symbols(repeat))) throw new IllegalStateException("Booster seeded selection changed");
+            chest.setItem(2, first);
+            for (var hand : InteractionHand.values()) {
+                player.getInventory().clearContent();
+                player.setItemInHand(InteractionHand.OFF_HAND, ItemStack.EMPTY);
+                player.setItemInHand(hand, new ItemStack(Rivencraft.SEALED_NOTEBOOK.get()));
+                Rivencraft.SEALED_NOTEBOOK.get().use(level, player, hand);
+                folder(player.getItemInHand(hand));
+            }
+            player.getInventory().clearContent();
+            player.setItemInHand(InteractionHand.OFF_HAND, ItemStack.EMPTY);
+            player.setItemInHand(InteractionHand.MAIN_HAND, new ItemStack(Rivencraft.SEALED_NOTEBOOK.get(), 2));
+            Rivencraft.SEALED_NOTEBOOK.get().use(level, player, InteractionHand.MAIN_HAND);
+            if (player.getMainHandItem().getCount() != 1) throw new IllegalStateException("Booster stack consumption regression");
+            player.getAbilities().instabuild = true;
+            Rivencraft.SEALED_NOTEBOOK.get().use(level, player, InteractionHand.MAIN_HAND);
+            if (!player.getMainHandItem().is(Rivencraft.SEALED_NOTEBOOK.get()) || player.getMainHandItem().getCount() != 1)
+                throw new IllegalStateException("Creative booster consumed its input");
+            player.getAbilities().instabuild = false;
+            for (int slot = 0; slot < player.getInventory().getContainerSize(); slot++)
+                player.getInventory().setItem(slot, new ItemStack(Items.COBBLESTONE, 64));
+            player.setItemInHand(InteractionHand.MAIN_HAND, new ItemStack(Rivencraft.SEALED_NOTEBOOK.get(), 2));
+            Rivencraft.SEALED_NOTEBOOK.get().use(level, player, InteractionHand.MAIN_HAND);
+            var dropped = level.getEntitiesOfClass(ItemEntity.class, new AABB(-3, 60, -3, 4, 70, 6),
+                    entity -> entity.getItem().is(Rivencraft.COLLATION_FOLDER.get()));
+            if (dropped.size() != 1 || player.getMainHandItem().getCount() != 1)
+                throw new IllegalStateException("Full-inventory booster delivery regression");
+            folder(dropped.getFirst().getItem());
+            dropped.getFirst().discard();
+        } finally {
+            player.getAbilities().instabuild = false;
+            player.getInventory().clearContent();
+            player.setItemInHand(InteractionHand.OFF_HAND, ItemStack.EMPTY);
+        }
+        verify(level);
+    }
+
+    static void verify(ServerLevel level) {
+        if (!(level.getBlockEntity(CHEST) instanceof Container chest)) throw new IllegalStateException("Fixture chest missing");
+        if (!chest.getItem(0).is(Rivencraft.SYMBOL_PORTFOLIO.get()) || contents(chest.getItem(0)).pageCount() != 252
+                || !chest.getItem(1).is(Rivencraft.SYMBOL_PORTFOLIO.get()) || contents(chest.getItem(1)).pageCount() != 1)
+            throw new IllegalStateException("Portfolio persistence regression");
+        folder(chest.getItem(2));
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortDayCycle.java

@@ -127,19 +127,15 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
     }
 
     public static boolean validWriting(List<Identifier> pages) {
-        int periods = 0, phases = 0, directions = 0, angles = 0, sizes = 0, suns = 0, moons = 0;
-        for (Identifier page : pages) {
-            if (isPeriod(page) && ++periods > 1 || isPhase(page) && ++phases > 1
-                    || isDirection(page) && ++directions > 1 || isAngle(page) && ++angles > 1
-                    || isSize(page) && ++sizes > 1) return false;
-            if (isController(page)) {
-                if (!page.getPath().equals("celestial/moon")) suns++;
-                if (!page.getPath().equals("celestial/sun")) moons++;
-                if (suns > 10 || moons > 10) return false;
-                periods = phases = directions = angles = sizes = 0;
-            }
+        int suns = 0, moons = 0;
+        for (Identifier page : pages) if (isController(page)) {
+            if (!page.getPath().equals("celestial/moon")) suns++;
+            if (!page.getPath().equals("celestial/sun")) moons++;
+            if (suns > 10 || moons > 10) return false;
         }
-        return periods + phases + directions + angles + sizes == 0;
+        // Repeated modifiers overwrite the pending value. Unconsumed modifiers
+        // earn grammar instability, but never affect an earlier body.
+        return true;
     }
 
     public static PortDayCycle compile(List<Identifier> pages, long seed) {
@@ -148,15 +144,20 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
 
     /** Creation-only completion. Exact diagnostic fixtures can still use compile. */
     public static PortDayCycle resolve(List<Identifier> pages, long seed, long nativeTicks) {
-        if (!validWriting(pages) || !PortAgeColors.validNumbers(pages))
-            throw new IllegalArgumentException("Invalid celestial modifier order");
+        return resolve(pages, seed, nativeTicks, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static PortDayCycle resolve(List<Identifier> pages, long seed, long nativeTicks, PortRandomPagePolicy policy) {
+        if (!validWriting(pages))
+            throw new IllegalArgumentException("An Age may have at most ten suns and ten moons");
         if (pages.stream().anyMatch(PortDayCycle::isController)) return compile(pages, seed, nativeTicks);
         // Match root AgeSkyProfile.random's count draw positions: sky style,
         // mixed sky color, then independent 0..3 sun and moon counts.
         var random = new Random(seed ^ 0x534B5950524F464CL);
         random.nextInt(5);
         randomColor(random);
-        int suns = random.nextInt(4), moons = random.nextInt(4);
+        int suns = policy.allows(Identifier.parse("rivencraft:celestial/sun")) ? random.nextInt(4) : 0;
+        int moons = policy.allows(Identifier.parse("rivencraft:celestial/moon")) ? random.nextInt(4) : 0;
         var bodies = new java.util.ArrayList<PortCelestialBody>();
         for (int i = 0; i < suns + moons; i++)
             bodies.addAll(randomUnmodified(seed, i, nativeTicks, i < suns ? SUN : MOON).bodies);
@@ -167,7 +168,7 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
     }
 
     public static PortDayCycle compile(List<Identifier> pages, long seed, long nativeTicks) {
-        if (!validWriting(pages)) throw new IllegalArgumentException("Place at most one of each celestial modifier before its controller; limit ten suns and ten moons");
+        if (!validWriting(pages)) throw new IllegalArgumentException("An Age may have at most ten suns and ten moons");
         if (pages.stream().filter(PortDayCycle::isController).count() <= 1)
             return compileOne(pages, seed, nativeTicks, 0);
         var bodies = new java.util.ArrayList<PortCelestialBody>();
@@ -190,8 +191,13 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
     }
 
     private static PortDayCycle compileOne(List<Identifier> pages, long seed, long nativeTicks, int ordinal) {
-        var controller = pages.stream().filter(PortDayCycle::isController).findFirst().orElse(null);
-        if (controller == null) return NATIVE;
+        int controllerIndex = -1;
+        for (int i = 0; i < pages.size(); i++) if (isController(pages.get(i))) { controllerIndex = i; break; }
+        // Only preceding modifiers belong to this controller. In particular, a
+        // trailing dangling modifier must not rewrite the single-body fast path.
+        if (controllerIndex < 0) return NATIVE;
+        pages = pages.subList(0, controllerIndex + 1);
+        var controller = pages.getLast();
         int mode = controller.getPath().equals("celestial/sun") ? SUN
                 : controller.getPath().equals("celestial/moon") ? MOON : PAIRED;
         if (mode != PAIRED && !hasBodyModifiers(pages)) return randomUnmodified(seed, ordinal, nativeTicks, mode);
@@ -308,6 +314,8 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
                 net.minecraft.core.registries.Registries.WORLD_CLOCK).getOrThrow(WorldClocks.OVERWORLD)).totalTicks();
     }
 
+    public static PortDayCycle forClient(Identifier id) { return clientCycles.getOrDefault(id, NATIVE); }
+
     public static void updateClient(Map<Identifier, PortDayCycle> cycles) { clientCycles = Map.copyOf(cycles); }
     public static PortDayCycle forLevel(Level level) {
         if (level instanceof PortAgeLevel age) return age.dayCycle();

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortDecayProviders.java

@@ -0,0 +1,202 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.DecayBlock;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.tags.TagKey;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.neoforged.neoforge.common.NeoForge;
+import net.neoforged.neoforge.common.util.BlockSnapshot;
+import net.neoforged.neoforge.common.util.FakePlayerFactory;
+import net.neoforged.neoforge.event.level.BlockEvent;
+
+/** Bounded, per-Age decay seeding and six-direction Legacy-style spreading. */
+public final class PortDecayProviders {
+    public static final TagKey<Block> PROTECTED = TagKey.create(Registries.BLOCK,
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "decay_protected"));
+    private static final Map<Identifier, DecayBlock.Color> COLORS = Map.of(
+            id("decayblue"), DecayBlock.Color.BLUE,
+            id("decaypurple"), DecayBlock.Color.PURPLE,
+            id("decayred"), DecayBlock.Color.RED,
+            id("decaywhite"), DecayBlock.Color.WHITE);
+    private static final Direction[] DIRECTIONS = Direction.values();
+
+    private PortDecayProviders() {}
+
+    public static void register() {
+        COLORS.keySet().forEach(id -> PortInstabilityRuntime.register(id, true, PortDecayProviders::apply));
+    }
+
+    /** Operator test hook; never changes the Age's saved instability score or provider plan. */
+    public static int pulseForTesting(ServerPlayer player, DecayBlock.Color color, int count) {
+        ServerLevel level = player.level();
+        if (!PortInstabilityConfig.decayEnabled() || !PortInstabilityConfig.instabilityWorldMutation()
+                || !PortInstabilityRuntime.isAge(level)
+                || level.getChunkSource().getChunkNow(player.chunkPosition().x(), player.chunkPosition().z()) == null) return -1;
+        var age = PortInstabilityData.get(level.getServer()).age(level);
+        Identifier id = id("decay" + color.getSerializedName());
+        if (!PortInstabilityConfig.instabilityEnabled() || !age.enabled()
+                || !PortInstabilityConfig.instabilityProviderEnabled(id)) return -1;
+        int changed = 0;
+        for (int i = 0; i < Math.min(count, 32); i++) {
+            PortInstabilityRuntime.Budget budget = new PortInstabilityRuntime.Budget(1);
+            apply(new PortInstabilityRuntime.Context(level, age, List.of(player.chunkPosition()),
+                    level.getServer().getTickCount(), budget), id, 1);
+            changed += budget.applied();
+        }
+        return changed;
+    }
+
+    static void apply(PortInstabilityRuntime.Context context, Identifier id, int level) {
+        if (!PortInstabilityConfig.decayEnabled() || !PortInstabilityConfig.instabilityWorldMutation()
+                || !PortInstabilityRuntime.isAge(context.level())
+                || context.loadedChunks().isEmpty()) return;
+        DecayBlock.Color color = COLORS.get(id);
+        if (color == null) return;
+        PortDecaySavedData data = PortDecaySavedData.get(context.level());
+        Random random = new Random(context.age().seed() ^ data.nextAttempt() * 0x9E3779B97F4A7C15L
+                ^ id.hashCode());
+        List<BlockPos> frontier = data.frontier(color);
+        BlockPos source = selectLoadedSource(context.level(), context.loadedChunks(), frontier, random);
+        if (source == null) {
+            seed(context, color, data, random);
+            return;
+        }
+        BlockState sourceState = context.level().getBlockState(source);
+        if (!sourceState.is(Rivencraft.DECAY.get()) || sourceState.getValue(DecayBlock.COLOR) != color) {
+            data.remove(color, source);
+            return;
+        }
+        for (int attempt = 0; attempt < PortInstabilityConfig.decayMaxAttempts(); attempt++) {
+            BlockPos target = source.relative(DIRECTIONS[random.nextInt(DIRECTIONS.length)]);
+            if (!isLoadedTarget(context.level(), context.loadedChunks(), target)
+                    || isSpawnProtected(context.age(), target)) continue;
+            BlockState prior = context.level().getBlockState(target);
+            if (!canReplace(context.level(), target, prior, color)) continue;
+            int difficulty = conversionDifficulty(context.level(), target, prior, color);
+            if (random.nextInt(difficulty) != 0) continue;
+            if (replace(context, target, prior, color)) data.add(color, target);
+            return;
+        }
+    }
+
+    private static void seed(PortInstabilityRuntime.Context context, DecayBlock.Color color,
+                             PortDecaySavedData data, Random random) {
+        ChunkPos chunk = context.loadedChunks().get(random.nextInt(context.loadedChunks().size()));
+        int x = chunk.getMinBlockX() + random.nextInt(16);
+        int z = chunk.getMinBlockZ() + random.nextInt(16);
+        BlockPos pos = new BlockPos(x,
+                context.level().getHeight(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, x, z) - 1, z);
+        if (!isLoadedTarget(context.level(), context.loadedChunks(), pos)
+                || isSpawnProtected(context.age(), pos)) return;
+        BlockState prior = context.level().getBlockState(pos);
+        if (canReplace(context.level(), pos, prior, color) && replace(context, pos, prior, color)) {
+            data.add(color, pos);
+        }
+    }
+
+    private static BlockPos selectLoadedSource(ServerLevel level, List<ChunkPos> chunks,
+                                                List<BlockPos> frontier, Random random) {
+        if (frontier.isEmpty()) return null;
+        int start = random.nextInt(frontier.size());
+        for (int i = 0; i < Math.min(frontier.size(), 16); i++) {
+            BlockPos pos = frontier.get((start + i) % frontier.size());
+            if (isLoadedTarget(level, chunks, pos)) return pos;
+        }
+        return null;
+    }
+
+    static boolean isLoadedTarget(ServerLevel level, List<ChunkPos> chunks, BlockPos pos) {
+        return level.isInWorldBounds(pos) && level.getChunkSource().getChunkNow(pos.getX() >> 4, pos.getZ() >> 4) != null
+                && chunks.contains(ChunkPos.containing(pos));
+    }
+
+    static boolean isSpawnProtected(PortInstabilityData.Age age, BlockPos pos) {
+        BlockPos spawn = age.spawn().orElse(null);
+        return spawn != null && Math.abs(pos.getX() - spawn.getX()) <= 4
+                && Math.abs(pos.getZ() - spawn.getZ()) <= 4
+                && pos.getY() >= spawn.getY() - 2 && pos.getY() <= spawn.getY() + 4;
+    }
+
+    static boolean canReplace(ServerLevel level, BlockPos pos, BlockState prior, DecayBlock.Color color) {
+        if (!PortInstabilityRuntime.isAge(level)
+                || !level.isInWorldBounds(pos) || level.getChunkSource().getChunkNow(pos.getX() >> 4, pos.getZ() >> 4) == null
+                || prior.is(PROTECTED) || prior.is(BlockTags.PORTALS)
+                || prior.hasBlockEntity() || level.getBlockEntity(pos) != null
+                || prior.getDestroySpeed(level, pos) < 0 || !prior.getFluidState().isEmpty()
+                || isCritical(prior)) return false;
+        return !prior.is(Rivencraft.DECAY.get()) || prior.getValue(DecayBlock.COLOR) != color;
+    }
+
+    private static boolean isCritical(BlockState prior) {
+        return prior.is(Blocks.BEDROCK) || prior.is(Blocks.BARRIER)
+                || prior.is(Blocks.END_PORTAL) || prior.is(Blocks.END_PORTAL_FRAME)
+                || prior.is(Blocks.END_GATEWAY) || prior.is(Blocks.NETHER_PORTAL)
+                || prior.is(Blocks.COMMAND_BLOCK) || prior.is(Blocks.CHAIN_COMMAND_BLOCK)
+                || prior.is(Blocks.REPEATING_COMMAND_BLOCK) || prior.is(Blocks.STRUCTURE_BLOCK)
+                || prior.is(Blocks.JIGSAW) || prior.is(Blocks.LIGHT)
+                || prior.is(Blocks.REINFORCED_DEEPSLATE)
+                || prior.getBlock() != Rivencraft.DECAY.get()
+                && net.minecraft.core.registries.BuiltInRegistries.BLOCK.getKey(prior.getBlock())
+                        .getNamespace().equals(Rivencraft.MOD_ID);
+    }
+
+    static int conversionDifficulty(ServerLevel level, BlockPos pos, BlockState state, DecayBlock.Color color) {
+        if (state.isAir()) return switch (color) {
+            case BLUE, RED -> 20;
+            case PURPLE -> 8;
+            case WHITE -> 50;
+        };
+        if (state.is(Rivencraft.DECAY.get())) return color == DecayBlock.Color.WHITE ? 1 : 5;
+        float hardness = Math.min(1000.0F, Math.max(0.0F, state.getDestroySpeed(level, pos)));
+        return switch (color) {
+            case BLUE -> Math.max(1, (int) hardness * 2);
+            case RED -> Math.max(1, (int) hardness);
+            case PURPLE -> Math.max(1, ((int) hardness + 1) * 10);
+            case WHITE -> 1;
+        };
+    }
+
+    private static boolean replace(PortInstabilityRuntime.Context context, BlockPos pos, BlockState prior,
+                                   DecayBlock.Color color) {
+        ServerLevel level = context.level();
+        // A fake player gives claim/protection listeners the Age and exact block position.
+        var actor = FakePlayerFactory.getMinecraft(level);
+        actor.setPos(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
+        if (!prior.isAir()) {
+            var breakEvent = new net.neoforged.neoforge.event.level.block.BreakBlockEvent(level, pos, prior, actor);
+            NeoForge.EVENT_BUS.post(breakEvent);
+            if (breakEvent.isCanceled()) return false;
+        }
+        if (level.getBlockState(pos) != prior || !context.budget().claim()) return false;
+        var snapshot = BlockSnapshot.create(level.dimension(), level, pos);
+        BlockState decay = Rivencraft.DECAY.get().defaultBlockState().setValue(DecayBlock.COLOR, color);
+        if (!level.setBlock(pos, decay, 3)) return false;
+        var placeEvent = new BlockEvent.EntityPlaceEvent(snapshot, prior, actor);
+        NeoForge.EVENT_BUS.post(placeEvent);
+        if (placeEvent.isCanceled()) {
+            snapshot.restore();
+            return false;
+        }
+        context.budget().recordApplied();
+        return true;
+    }
+
+    private static Identifier id(String path) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortDecaySavedData.java

@@ -0,0 +1,44 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.ArrayList;
+import java.util.EnumMap;
+import java.util.List;
+import java.util.Map;
+import net.dnorberg.rivencraft.block.DecayBlock;
+import net.minecraft.core.BlockPos;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.StringRepresentable;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Persisted per-Age frontier and attempt sequence, bounded to 1,024 positions per color. */
+public final class PortDecaySavedData extends SavedData {
+    private static final int MAX_FRONTIER_PER_COLOR = 1024;
+    private static final Codec<PortDecaySavedData> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            net.minecraft.util.ExtraCodecs.NON_NEGATIVE_LONG.optionalFieldOf("attempts", 0L).forGetter(data -> data.attempts),
+            Codec.unboundedMap(StringRepresentable.fromEnum(DecayBlock.Color::values),
+                    BlockPos.CODEC.listOf(0, MAX_FRONTIER_PER_COLOR)).fieldOf("frontiers").forGetter(data -> data.frontiers)
+    ).apply(instance, PortDecaySavedData::new));
+    private static final SavedDataType<PortDecaySavedData> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "decay"), () -> new PortDecaySavedData(0, Map.of()), CODEC);
+    private final EnumMap<DecayBlock.Color, List<BlockPos>> frontiers = new EnumMap<>(DecayBlock.Color.class);
+    private long attempts;
+    private PortDecaySavedData(long attempts, Map<DecayBlock.Color, List<BlockPos>> positions) {
+        this.attempts = attempts;
+        for (var color : DecayBlock.Color.values()) frontiers.put(color,
+                new ArrayList<>(positions.getOrDefault(color, List.of()).stream().distinct().map(BlockPos::immutable).toList()));
+    }
+    public static PortDecaySavedData get(ServerLevel level) { return level.getDataStorage().computeIfAbsent(TYPE); }
+    public long nextAttempt() { setDirty(); return attempts++; }
+    public List<BlockPos> frontier(DecayBlock.Color color) { return frontiers.get(color); }
+    public void add(DecayBlock.Color color, BlockPos pos) {
+        var frontier = frontiers.get(color);
+        if (frontier.contains(pos)) return;
+        if (frontier.size() >= MAX_FRONTIER_PER_COLOR) frontier.removeFirst();
+        frontier.add(pos.immutable()); setDirty();
+    }
+    public void remove(DecayBlock.Color color, BlockPos pos) { if (frontiers.get(color).remove(pos)) setDirty(); }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortDroppedBookProbe.java

@@ -0,0 +1,81 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.UUID;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.entity.DroppedBookEntity;
+import net.dnorberg.rivencraft.item.LinkBookTarget;
+import net.dnorberg.rivencraft.item.PortHandheldTravel;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.storage.TagValueInput;
+import net.minecraft.world.level.storage.TagValueOutput;
+import net.minecraft.util.ProblemReporter;
+import net.minecraft.world.phys.AABB;
+import net.neoforged.neoforge.common.util.FakePlayerFactory;
+
+/** Disposable-world checks for book ownership and the new entity save format. */
+final class PortDroppedBookProbe {
+    private PortDroppedBookProbe() {}
+
+    static void create(ServerLevel level) {
+        PortAgeTravel.findLanding(level);
+        var player = FakePlayerFactory.get(level, new com.mojang.authlib.GameProfile(
+                UUID.fromString("4db5c544-0a0c-421d-a128-c520bda64642"), "RivenBookProbe"));
+        player.setPos(0.5, 64, 0.5);
+        try {
+            for (var hand : InteractionHand.values()) {
+                ItemStack book = new ItemStack(hand == InteractionHand.MAIN_HAND
+                        ? Rivencraft.LINKING_BOOK.get() : Rivencraft.DESCRIPTIVE_BOOK.get());
+                book.set(DataComponents.CUSTOM_NAME, Component.literal("Dropped fixture " + hand));
+                book.set(Rivencraft.LINK_BOOK_TARGET.get(), new LinkBookTarget(
+                        Identifier.fromNamespaceAndPath("minecraft", "overworld"), 12.25, 80.5, -42.75, 135, -20));
+                player.setItemInHand(hand, book);
+                String failure = PortHandheldTravel.travel(player, hand, book, () -> "expected failure");
+                if (!"expected failure".equals(failure) || player.getItemInHand(hand) != book)
+                    throw new IllegalStateException("Failed travel consumed the book");
+                try {
+                    PortHandheldTravel.travel(player, hand, book, () -> { throw new IllegalStateException("fixture"); });
+                    throw new AssertionError("Fixture exception was swallowed");
+                } catch (IllegalStateException expected) {
+                    if (!"fixture".equals(expected.getMessage()) || player.getItemInHand(hand) != book) throw expected;
+                }
+                java.util.function.Consumer<net.neoforged.neoforge.event.entity.EntityJoinLevelEvent> cancel = event -> {
+                    if (event.getLevel() == level && event.getEntity() instanceof DroppedBookEntity) event.setCanceled(true);
+                };
+                net.neoforged.neoforge.common.NeoForge.EVENT_BUS.addListener(cancel);
+                try {
+                    failure = PortHandheldTravel.travel(player, hand, book, () -> null);
+                    if (failure != null || player.getItemInHand(hand) != book)
+                        throw new IllegalStateException("Rejected dropped entity consumed the book");
+                } finally { net.neoforged.neoforge.common.NeoForge.EVENT_BUS.unregister(cancel); }
+                failure = PortHandheldTravel.travel(player, hand, book, () -> null);
+                if (failure != null || !player.getItemInHand(hand).isEmpty())
+                    throw new IllegalStateException("Successful travel retained the active book");
+            }
+        } finally { player.getInventory().clearContent(); }
+        verify(level);
+    }
+
+    static void verify(ServerLevel level) {
+        var books = level.getEntitiesOfClass(DroppedBookEntity.class, new AABB(-2, 60, -2, 3, 68, 3));
+        if (books.size() != 2) throw new IllegalStateException("Expected two dropped books, found " + books.size());
+        for (var entity : books) {
+            var output = TagValueOutput.createWithContext(ProblemReporter.DISCARDING, level.registryAccess());
+            entity.saveWithoutId(output);
+            var copy = new DroppedBookEntity(Rivencraft.DROPPED_BOOK.get(), level);
+            copy.load(TagValueInput.create(ProblemReporter.DISCARDING, level.registryAccess(), output.buildResult()));
+            if (!ItemStack.isSameItemSameComponents(copy.getItem(), entity.getItem())
+                    || copy.getAge() != -32768 || copy.getItem().getCount() != 1)
+                throw new IllegalStateException("Dropped book persistence regression");
+            var copied = TagValueOutput.createWithContext(ProblemReporter.DISCARDING, level.registryAccess());
+            copy.saveWithoutId(copied);
+            if (copied.buildResult().getIntOr("BookDecayTicks", -1)
+                    != output.buildResult().getIntOr("BookDecayTicks", -2))
+                throw new IllegalStateException("Dropped book decay counter was not preserved");
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortEnvironmentSelection.java

@@ -1,6 +1,5 @@
 package net.dnorberg.rivencraft.age;
 
-import java.util.Arrays;
 import java.util.List;
 import java.util.Random;
 import net.minecraft.resources.Identifier;
@@ -8,21 +7,28 @@ import net.minecraft.resources.Identifier;
 /** Seed-completes missing environment controllers once, before an Age is saved. */
 public record PortEnvironmentSelection(PortWeatherMode weather, PortLighting lighting, PortSkyStyle sky) {
     public static PortEnvironmentSelection resolve(List<Identifier> pages, long seed, PortAgeTerrain terrain) {
-        PortLighting lighting = pages.stream().map(PortLighting::forPage).filter(java.util.Objects::nonNull)
-                .findFirst().orElseGet(() -> rankedDefault(new Random(seed ^ 0x4C49474854494E47L), PortLighting.values()));
-        PortWeatherMode weather = terrain == PortAgeTerrain.CAVE ? PortWeatherMode.OFF
-                : pages.stream().map(PortWeatherMode::forPage).filter(java.util.Objects::nonNull)
-                        .findFirst().orElseGet(() -> rankedDefault(new Random(seed ^ 0x574541544845525FL), PortWeatherMode.values()));
-        return new PortEnvironmentSelection(weather, lighting, PortSkyStyle.resolve(pages, seed));
+        return resolve(pages, seed, terrain, PortRandomPagePolicy.UNRESTRICTED);
     }
 
-    private static <T> T rankedDefault(Random random, T[] choices) {
+    public static PortEnvironmentSelection resolve(List<Identifier> pages, long seed, PortAgeTerrain terrain,
+                                                    PortRandomPagePolicy policy) {
+        PortLighting lighting = pages.stream().map(PortLighting::forPage).filter(java.util.Objects::nonNull)
+                .findFirst().orElseGet(() -> rankedDefault(new Random(seed ^ 0x4C49474854494E47L), PortLighting.values(), "lighting", policy));
+        PortWeatherMode weather = terrain == PortAgeTerrain.CAVE ? PortWeatherMode.OFF
+                : pages.stream().map(PortWeatherMode::forPage).filter(java.util.Objects::nonNull)
+                        .findFirst().orElseGet(() -> rankedDefault(new Random(seed ^ 0x574541544845525FL), PortWeatherMode.values(), "weather", policy));
+        return new PortEnvironmentSelection(weather, lighting, PortSkyStyle.resolve(pages, seed, policy));
+    }
+
+    private static <T extends Enum<T>> T rankedDefault(Random random, T[] choices, String category, PortRandomPagePolicy policy) {
         // LegacyRankChoice: the first (Normal) option is rank 1, the rest rank 2.
         // Its rank-1 weight is the complete rare group plus one. Derive this
         // from the supported pool, rather than selecting unported weather.
-        int[] weights = new int[choices.length];
-        Arrays.fill(weights, 1);
-        weights[0] = choices.length;
-        return PortRandomAgeSelection.weighted(random, List.of(choices), weights);
+        var options = new java.util.ArrayList<PortRankedChoice.Option<T>>();
+        for (int i = 0; i < choices.length; i++)
+            options.add(new PortRankedChoice.Option<>(choices[i], i == 0 ? 1 : 2));
+        return PortRankedChoice.choose(random, policy.required(options,
+                option -> PortRandomPagePolicy.page(category, option.value()),
+                new PortRankedChoice.Option<>(choices[0], 1)));
     }
 }

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortEnvironmentalProviders.java

@@ -0,0 +1,178 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Random;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.DecayBlock;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.LivingEntity;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.entity.EntityTypeTest;
+import net.minecraft.world.phys.BlockHitResult;
+import net.minecraft.world.phys.AABB;
+import net.neoforged.neoforge.common.NeoForge;
+import net.neoforged.neoforge.common.util.BlockSnapshot;
+import net.neoforged.neoforge.common.util.FakePlayerFactory;
+import net.neoforged.neoforge.event.level.BlockEvent;
+
+/** Active Legacy burning and the 1.21.1 test-enabled erosion policy. */
+public final class PortEnvironmentalProviders {
+    public static final Identifier BURNING = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "burning");
+    public static final Identifier EROSION = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "erosion");
+    private static final Direction[] FLUID_SIDES = {
+            Direction.UP, Direction.NORTH, Direction.SOUTH, Direction.EAST, Direction.WEST
+    };
+    private PortEnvironmentalProviders() {}
+    public static void register() {
+        PortInstabilityRuntime.register(BURNING, false, (context, id, level) -> {
+            if (PortInstabilityRuntime.isAge(context.level()) && !context.loadedChunks().isEmpty()) scorch(context, level);
+        });
+        PortInstabilityRuntime.register(EROSION, true, (context, id, level) -> {
+            if (PortInstabilityRuntime.isAge(context.level()) && !context.loadedChunks().isEmpty()) erode(context);
+        });
+    }
+    public static boolean isEnvironmental(Identifier id) { return id.equals(BURNING) || id.equals(EROSION); }
+    static void tickPlanned(ServerLevel level, PortInstabilityData.Age age, long tick,
+                            List<PortInstabilityPlan.ProviderLevel> providers) {
+        var cards = providers.stream().filter(card -> isEnvironmental(card.id())).toList();
+        boolean erosion = PortInstabilityConfig.erosionEnabled() && PortInstabilityRuntime.effectiveScore(level)
+                >= InstabilityProviderCatalog.Deck.DESTRUCTIVE.entryCost();
+        if (cards.isEmpty() && !erosion) return;
+        var chunks = PortHazardProviders.loadedChunksNearPlayers(level, PortInstabilityConfig.hazardsMaxChunks());
+        if (chunks.isEmpty()) return;
+        for (var card : cards) {
+            int budget = card.id().equals(BURNING) ? PortInstabilityConfig.scorchMaxTargets() : 1;
+            PortInstabilityRuntime.invoke(new PortInstabilityRuntime.Context(level, age, chunks, tick,
+                    new PortInstabilityRuntime.Budget(budget)), card.id(), card.level());
+        }
+        if (erosion && cards.stream().noneMatch(card -> card.id().equals(EROSION)))
+            PortInstabilityRuntime.invoke(new PortInstabilityRuntime.Context(level, age, chunks, tick,
+                    new PortInstabilityRuntime.Budget(1)), EROSION, 1);
+    }
+    /** Skips random burning selection or looks at one erosion target, preserving policy. */
+    public static int pulseForTesting(ServerPlayer player, String effect) {
+        ServerLevel level = player.level();
+        if (!PortInstabilityRuntime.isAge(level)) return -1;
+        var age = PortInstabilityData.get(level.getServer()).age(level);
+        Identifier id = effect.equals("burning") ? BURNING : EROSION;
+        if (!PortInstabilityConfig.instabilityEnabled() || !age.enabled()
+                || !PortInstabilityConfig.instabilityProviderEnabled(id)) return 0;
+        var chunks = PortHazardProviders.loadedChunksNearPlayers(level, 16);
+        if (chunks.isEmpty()) return 0;
+        var context = new PortInstabilityRuntime.Context(level, age, chunks,
+                level.getServer().getTickCount(), new PortInstabilityRuntime.Budget(1));
+        if (effect.equals("burning")) {
+            if (!PortInstabilityConfig.scorchEnabled() || !PortInstabilityConfig.scorchPlayers()
+                    || !eligibleScorch(context, player)) return 0;
+            if (player.isInWaterOrRain()) return -2;
+            player.igniteForSeconds(4);
+            return 1;
+        }
+        if (!effect.equals("erosion") || !PortInstabilityConfig.erosionEnabled() || !PortHazardProviders.canMutate(level)
+                || PortInstabilityRuntime.effectiveScore(level) < InstabilityProviderCatalog.Deck.DESTRUCTIVE.entryCost()
+                || !(player.pick(6.0, 0.0F, false) instanceof BlockHitResult hit)
+                || hit.getType() != net.minecraft.world.phys.HitResult.Type.BLOCK) return 0;
+        return erodeAt(context, hit.getBlockPos()) ? 1 : 0;
+    }
+
+    private static void scorch(PortInstabilityRuntime.Context context, int effectiveLevel) {
+        if (!PortInstabilityConfig.scorchEnabled() || PortInstabilityConfig.scorchMaxTargets() == 0) return;
+        ServerLevel level = context.level();
+        Random random = new Random(context.age().seed() ^ PortHazardSavedData.get(level).nextAttempt()
+                * 0x9E3779B97F4A7C15L ^ BURNING.hashCode());
+        int start = random.nextInt(context.loadedChunks().size());
+        int affected = 0;
+        for (int offset = 0; offset < Math.min(8, context.loadedChunks().size()); offset++) {
+            ChunkPos chunk = context.loadedChunks().get((start + offset) % context.loadedChunks().size());
+            AABB bounds = new AABB(chunk.getMinBlockX(), level.getMinY(), chunk.getMinBlockZ(),
+                    chunk.getMaxBlockX() + 1, level.getMaxY(), chunk.getMaxBlockZ() + 1);
+            List<LivingEntity> candidates = new ArrayList<>();
+            level.getEntities(EntityTypeTest.forClass(LivingEntity.class), bounds,
+                    entity -> eligibleScorch(context, entity), candidates, 8);
+            candidates.sort(Comparator.comparing(Entity::getUUID));
+            for (LivingEntity entity : candidates) {
+                if (affected >= PortInstabilityConfig.scorchMaxTargets() || context.budget().remaining() == 0) return;
+                // Legacy sampled each chunk each tick with a 1/10 gate. With 20 ticks/pass this
+                // gives at least one opportunity for nearly every inspected loaded chunk.
+                if (random.nextDouble() >= PortHazardProviders.legacyChance(1,
+                        PortInstabilityConfig.instabilityCooldown(), 1, 10)) continue;
+                if (!context.budget().claim()) return;
+                entity.igniteForSeconds(Math.min(12, 4 * effectiveLevel));
+                context.budget().recordApplied();
+                affected++;
+                break;
+            }
+        }
+    }
+
+    private static boolean eligibleScorch(PortInstabilityRuntime.Context context, LivingEntity entity) {
+        if (!entity.isAlive() || entity.isRemoved() || entity.level() != context.level()
+                || !context.level().canSeeSky(entity.blockPosition())
+                || PortDecayProviders.isSpawnProtected(context.age(), entity.blockPosition())) return false;
+        if (entity instanceof Player player) return PortInstabilityConfig.scorchPlayers()
+                && !player.isCreative() && !player.isSpectator();
+        return true;
+    }
+
+    private static void erode(PortInstabilityRuntime.Context context) {
+        if (!PortInstabilityConfig.erosionEnabled() || !PortHazardProviders.canMutate(context.level())) return;
+        ServerLevel level = context.level();
+        Random random = new Random(context.age().seed() ^ PortHazardSavedData.get(level).nextAttempt()
+                * 0xC2B2AE3D27D4EB4FL ^ EROSION.hashCode());
+        for (int attempt = 0; attempt < 8; attempt++) {
+            ChunkPos chunk = context.loadedChunks().get(random.nextInt(context.loadedChunks().size()));
+            int x = chunk.getMinBlockX() + random.nextInt(16);
+            int z = chunk.getMinBlockZ() + random.nextInt(16);
+            int y = level.getMinY() + 1 + random.nextInt(level.getHeight() - 2);
+            if (erodeAt(context, new BlockPos(x, y, z))) return;
+        }
+    }
+
+    static boolean erodeAt(PortInstabilityRuntime.Context context, BlockPos pos) {
+        ServerLevel level = context.level();
+        if (!PortDecayProviders.isLoadedTarget(level, context.loadedChunks(), pos)
+                || PortDecayProviders.isSpawnProtected(context.age(), pos)) return false;
+        BlockState prior = level.getBlockState(pos);
+        if (!PortDecayProviders.canReplace(level, pos, prior, DecayBlock.Color.BLUE)) return false;
+        for (Direction direction : FLUID_SIDES) {
+            BlockPos neighbor = pos.relative(direction);
+            if (!PortDecayProviders.isLoadedTarget(level, context.loadedChunks(), neighbor)) continue;
+            var fluid = level.getFluidState(neighbor);
+            if (fluid.isSource() && replaceFluid(context, pos, prior, fluid.createLegacyBlock())) return true;
+        }
+        return false;
+    }
+
+    private static boolean replaceFluid(PortInstabilityRuntime.Context context, BlockPos pos,
+            BlockState prior, BlockState fluidBlock) {
+        ServerLevel level = context.level();
+        var actor = FakePlayerFactory.getMinecraft(level);
+        actor.setPos(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
+        if (!prior.isAir()) {
+            var breaking = new net.neoforged.neoforge.event.level.block.BreakBlockEvent(level, pos, prior, actor);
+            NeoForge.EVENT_BUS.post(breaking);
+            if (breaking.isCanceled()) return false;
+        }
+        if (level.getBlockState(pos) != prior || !context.budget().claim()) return false;
+        var snapshot = BlockSnapshot.create(level.dimension(), level, pos);
+        if (!level.setBlock(pos, fluidBlock, 3)) return false;
+        var placing = new BlockEvent.EntityPlaceEvent(snapshot, prior, actor);
+        NeoForge.EVENT_BUS.post(placing);
+        if (placing.isCanceled()) {
+            snapshot.restore();
+            return false;
+        }
+        context.budget().recordApplied();
+        return true;
+    }
+
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortFeatureChunkGenerator.java

@@ -70,10 +70,12 @@ public final class PortFeatureChunkGenerator extends ChunkGenerator {
                     .forGetter(generator -> Optional.ofNullable(generator.lakes)),
             PortTerrainFeaturePlan.CODEC.optionalFieldOf("terrain_features")
                     .forGetter(generator -> Optional.ofNullable(generator.terrainFeatures)),
-            com.mojang.serialization.Codec.LONG.fieldOf("age_seed").forGetter(generator -> generator.ageSeed)
-    ).apply(instance, (base, rocks, vegetation, dungeons, lakes, terrainFeatures, seed) ->
+            com.mojang.serialization.Codec.LONG.fieldOf("age_seed").forGetter(generator -> generator.ageSeed),
+            com.mojang.serialization.Codec.BOOL.optionalFieldOf("libraries", false).forGetter(generator -> generator.libraries),
+            Identifier.CODEC.listOf().optionalFieldOf("library_symbols", List.of()).forGetter(generator -> generator.librarySymbols)
+    ).apply(instance, (base, rocks, vegetation, dungeons, lakes, terrainFeatures, seed, libraries, symbols) ->
             new PortFeatureChunkGenerator(base, rocks.orElse(null), vegetation.orElse(null),
-                    dungeons, lakes.orElse(null), terrainFeatures.orElse(null), seed)));
+                    dungeons, lakes.orElse(null), terrainFeatures.orElse(null), seed, libraries, symbols)));
 
     private final ChunkGenerator base;
     private final PortRockPlan rocks;
@@ -82,10 +84,19 @@ public final class PortFeatureChunkGenerator extends ChunkGenerator {
     private final PortLakePlan lakes;
     private final PortTerrainFeaturePlan terrainFeatures;
     private final long ageSeed;
+    private final boolean libraries;
+    private final List<Identifier> librarySymbols;
 
     public PortFeatureChunkGenerator(ChunkGenerator base, PortRockPlan rocks,
                                      PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
                                      PortTerrainFeaturePlan terrainFeatures, long ageSeed) {
+        this(base, rocks, vegetation, dungeons, lakes, terrainFeatures, ageSeed, false, List.of());
+    }
+
+    public PortFeatureChunkGenerator(ChunkGenerator base, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures, long ageSeed,
+                                     boolean libraries, List<Identifier> librarySymbols) {
         super(base.getBiomeSource(), base::getBiomeGenerationSettings);
         this.base = base;
         this.rocks = rocks;
@@ -94,6 +105,8 @@ public final class PortFeatureChunkGenerator extends ChunkGenerator {
         this.lakes = lakes;
         this.terrainFeatures = terrainFeatures;
         this.ageSeed = ageSeed;
+        this.libraries = libraries;
+        this.librarySymbols = List.copyOf(librarySymbols);
     }
 
     public ChunkGenerator base() { return base; }
@@ -286,5 +299,6 @@ public final class PortFeatureChunkGenerator extends ChunkGenerator {
                 if (PortVegetationPlan.addsLogs(page)) mushroomHosts = null;
             }
         }
+        if (libraries) PortLibraryFeature.generate(level, chunk, ageSeed, librarySymbols);
     }
 }

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortHazardProviders.java

@@ -0,0 +1,356 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Optional;
+import java.util.Random;
+import java.util.Set;
+import java.util.UUID;
+import java.util.function.Predicate;
+import net.dnorberg.rivencraft.Rivencraft;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.EntityTypes;
+import net.minecraft.world.entity.LightningBolt;
+import net.minecraft.world.entity.LivingEntity;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.Explosion;
+import net.minecraft.world.level.ExplosionDamageCalculator;
+import net.minecraft.world.level.gamerules.GameRules;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.material.FluidState;
+import net.minecraft.world.phys.AABB;
+import net.neoforged.neoforge.common.NeoForge;
+import net.neoforged.neoforge.common.util.FakePlayerFactory;
+import net.neoforged.neoforge.event.level.BlockEvent;
+
+/** Legacy hazard cards, with one loaded-chunk event and explicit damage budgets. */
+public final class PortHazardProviders {
+    private static final Identifier LIGHTNING = id("lightning");
+    private static final Identifier EXPLOSIONS = id("explosions");
+
+    private PortHazardProviders() {}
+
+    public static void register() {
+        // Visuals and entity damage remain available when block mutation is disabled.
+        PortInstabilityRuntime.register(LIGHTNING, false, PortHazardProviders::apply);
+        PortInstabilityRuntime.register(EXPLOSIONS, false, PortHazardProviders::apply);
+    }
+
+    static boolean isHazard(Identifier id) {
+        return LIGHTNING.equals(id) || EXPLOSIONS.equals(id);
+    }
+
+    /** Roll every selected hazard card each scheduler pass, independently of other providers. */
+    static void tickPlanned(ServerLevel level, PortInstabilityData.Age age, long tick,
+                            List<PortInstabilityPlan.ProviderLevel> providers) {
+        if (!PortInstabilityConfig.hazardsEnabled()) return;
+        List<PortInstabilityPlan.ProviderLevel> hazards = providers.stream()
+                .filter(provider -> isHazard(provider.id())).toList();
+        if (hazards.isEmpty()) return;
+        List<ChunkPos> chunks = loadedChunksNearPlayers(level, PortInstabilityConfig.hazardsMaxChunks());
+        if (chunks.isEmpty()) return;
+        for (PortInstabilityPlan.ProviderLevel hazard : hazards) {
+            var context = new PortInstabilityRuntime.Context(level, age, chunks, tick,
+                    new PortInstabilityRuntime.Budget(1));
+            PortInstabilityRuntime.invoke(context, hazard.id(), hazard.level());
+        }
+    }
+
+    static List<ChunkPos> loadedChunksNearPlayers(ServerLevel level, int maximum) {
+        List<ChunkPos> players = level.players().stream()
+                .sorted(Comparator.comparing(Entity::getUUID))
+                .map(ServerPlayer::chunkPosition).toList();
+        return candidateChunks(players, maximum,
+                chunk -> level.getChunkSource().getChunkNow(chunk.x(), chunk.z()) != null);
+    }
+
+    /** Pure candidate selection; the caller's predicate must only report already-loaded chunks. */
+    static List<ChunkPos> candidateChunks(List<ChunkPos> players, int maximum,
+                                           Predicate<ChunkPos> loaded) {
+        if (maximum <= 0) return List.of();
+        Set<ChunkPos> chunks = new LinkedHashSet<>();
+        for (int radius = 0; radius <= 4; radius++) {
+            for (int dx = -radius; dx <= radius; dx++) {
+                for (int dz = -radius; dz <= radius; dz++) {
+                    if (Math.max(Math.abs(dx), Math.abs(dz)) != radius) continue;
+                    for (ChunkPos center : players) {
+                        int x = center.x() + dx;
+                        int z = center.z() + dz;
+                        ChunkPos candidate = new ChunkPos(x, z);
+                        if (loaded.test(candidate)) chunks.add(candidate);
+                        if (chunks.size() >= maximum) return List.copyOf(chunks);
+                    }
+                }
+            }
+        }
+        return List.copyOf(chunks);
+    }
+
+    /** Operator-only test pulse; skips the random roll, not Age, cooldown, or safety checks. */
+    public static int pulseForTesting(ServerPlayer player, boolean lightning) {
+        return pulseForTesting(player.level(), player.blockPosition(), lightning);
+    }
+
+    public static int pulseForTesting(ServerLevel level, BlockPos origin, boolean lightning) {
+        if (!PortInstabilityConfig.hazardsEnabled()
+                || !PortInstabilityRuntime.isAge(level)) return -1;
+        var age = PortInstabilityData.get(level.getServer()).age(level);
+        if (!PortInstabilityConfig.instabilityEnabled() || !age.enabled()
+                || !PortInstabilityConfig.instabilityProviderEnabled(lightning ? LIGHTNING : EXPLOSIONS)) return -1;
+        PortHazardSavedData data = PortHazardSavedData.get(level);
+        if (!data.ready(lightning, level.getGameTime(), PortInstabilityConfig.hazardsMinInterval())) return 0;
+        ChunkPos center = ChunkPos.containing(origin);
+        for (int dx = -1; dx <= 1; dx++) {
+            for (int dz = -1; dz <= 1; dz++) {
+                ChunkPos chunk = new ChunkPos(center.x() + dx, center.z() + dz);
+                if (level.getChunkSource().getChunkNow(chunk.x(), chunk.z()) == null) continue;
+                int x = chunk.getMinBlockX() + 8;
+                int z = chunk.getMinBlockZ() + 8;
+                int y = lightning ? level.getHeight(Heightmap.Types.MOTION_BLOCKING, x, z)
+                        : origin.getY();
+                BlockPos pos = new BlockPos(x, y, z);
+                var context = new PortInstabilityRuntime.Context(level, age, List.of(chunk),
+                        level.getServer().getTickCount(), new PortInstabilityRuntime.Budget(1));
+                if (!safeTarget(context, pos, 8)) continue;
+                data.nextAttempt();
+                data.record(lightning, level.getGameTime());
+                return (lightning ? strike(level, age, chunk, pos) : explode(level, age, chunk, pos)) ? 1 : 0;
+            }
+        }
+        return 0;
+    }
+
+    static void apply(PortInstabilityRuntime.Context context, Identifier id, int effectiveLevel) {
+        ServerLevel level = context.level();
+        if (!PortInstabilityConfig.hazardsEnabled() || context.loadedChunks().isEmpty()
+                || !PortInstabilityRuntime.isAge(level)) return;
+        boolean lightning = id.equals(LIGHTNING);
+        if (!lightning && !id.equals(EXPLOSIONS)) return;
+        PortHazardSavedData data = PortHazardSavedData.get(level);
+        long gameTime = level.getGameTime();
+        if (!data.ready(lightning, gameTime, PortInstabilityConfig.hazardsMinInterval())) return;
+        Random random = new Random(context.age().seed() ^ data.nextAttempt() * 0x9E3779B97F4A7C15L
+                ^ id.hashCode());
+        int legacyDenominator = lightning ? level.isRaining() && level.isThundering() ? 5000 : 100000 : 1000;
+        // Legacy rolled once per chunk per tick; the shared scheduler visits this Age every >=20 ticks.
+        double chance = legacyChance(context.loadedChunks().size(), PortInstabilityConfig.instabilityCooldown(),
+                effectiveLevel, legacyDenominator);
+        if (random.nextDouble() >= chance) return;
+        ChunkPos chunk = context.loadedChunks().get(random.nextInt(context.loadedChunks().size()));
+        int margin = lightning ? 2 : 6;
+        int x = chunk.getMinBlockX() + margin + random.nextInt(16 - margin * 2);
+        int z = chunk.getMinBlockZ() + margin + random.nextInt(16 - margin * 2);
+        int y = lightning ? level.getHeight(Heightmap.Types.MOTION_BLOCKING, x, z)
+                : level.getMinY() + 1 + random.nextInt(level.getHeight() - 2);
+        BlockPos pos = new BlockPos(x, y, z);
+        if (!safeTarget(context, pos, 8) || !context.budget().claim()) return;
+        data.record(lightning, gameTime); // persist before dispatch so a restart cannot replay the event
+        if (lightning ? strike(level, context.age(), chunk, pos) : explode(level, context.age(), chunk, pos))
+            context.budget().recordApplied();
+    }
+
+    static double legacyChance(int loadedChunks, int intervalTicks, int copies, int denominator) {
+        if (loadedChunks <= 0 || intervalTicks <= 0 || copies <= 0 || denominator <= 0) return 0;
+        return 1.0 - Math.pow(1.0 - 1.0 / denominator, (double) loadedChunks * intervalTicks * copies);
+    }
+
+    static boolean safeTarget(PortInstabilityRuntime.Context context, BlockPos pos, int spawnMargin) {
+        if (!PortDecayProviders.isLoadedTarget(context.level(), context.loadedChunks(), pos)) return false;
+        BlockPos spawn = context.age().spawn().orElse(null);
+        return spawn == null || Math.abs(pos.getX() - spawn.getX()) > spawnMargin
+                || Math.abs(pos.getZ() - spawn.getZ()) > spawnMargin;
+    }
+
+    private static boolean strike(ServerLevel level, PortInstabilityData.Age age, ChunkPos chunk, BlockPos pos) {
+        AABB bounds = new AABB(pos).inflate(2);
+        if (!level.getEntitiesOfClass(LightningBolt.class, bounds).isEmpty()) return false;
+        LightningBolt bolt = EntityTypes.LIGHTNING_BOLT.create(level, net.minecraft.world.entity.EntitySpawnReason.TRIGGERED);
+        if (bolt == null) return false;
+        bolt.setPos(pos.getX() + 0.5, pos.getY(), pos.getZ() + 0.5);
+        bolt.setVisualOnly(true); // vanilla bolt damage/fire bypasses our explicit budgets
+        if (!level.addFreshEntity(bolt)) return false;
+        List<LivingEntity> targets = level.getEntitiesOfClass(LivingEntity.class, bounds,
+                entity -> entity.isAlive() && entity.level() == level && eligibleEntity(entity));
+        targets.sort(Comparator.comparing(Entity::getUUID));
+        int count = 0;
+        for (LivingEntity target : targets) {
+            if (count++ >= PortInstabilityConfig.hazardsMaxEntities()) break;
+            if (PortInstabilityConfig.hazardsMaxDamage() > 0)
+                target.hurtServer(level, level.damageSources().lightningBolt(), Math.min(5, PortInstabilityConfig.hazardsMaxDamage()));
+        }
+        // Legacy lightning started fires. Keep it separately gated by block policy and game rule.
+        if (canMutate(level) && PortInstabilityConfig.hazardsFire()
+                && level.canSpreadFireAround(pos)
+                && !PortDecayProviders.isSpawnProtected(age, pos)
+                && PortDecayProviders.isLoadedTarget(level, List.of(chunk), pos)) ignite(level, pos);
+        return true;
+    }
+
+    private static boolean explode(ServerLevel level, PortInstabilityData.Age age, ChunkPos chunk, BlockPos pos) {
+        return explodeBounded(level, age, chunk, pos, PortInstabilityConfig.hazardsBlockDamage(),
+                PortInstabilityConfig.hazardsPlayerDamage(), PortInstabilityConfig.hazardsFire(),
+                PortInstabilityConfig.hazardsMaxBlocks(), PortInstabilityConfig.hazardsMaxEntities(),
+                PortInstabilityConfig.hazardsMaxDamage(), PortInstabilityConfig.hazardsExplosionRadius());
+    }
+
+    /** Shared blast guard for meteor impacts; each effect supplies its own damage policy. */
+    static boolean explodeBounded(ServerLevel level, PortInstabilityData.Age age, ChunkPos chunk, BlockPos pos,
+            boolean blockDamage, boolean playerDamage, boolean ignite, int maxBlocks, int maxEntities,
+            int maxDamage, int radius) {
+        boolean grief = destructiveBlocksAllowed(PortInstabilityConfig.instabilityWorldMutation(),
+                level.getGameRules().get(GameRules.MOB_GRIEFING), blockDamage, maxBlocks);
+        boolean fire = grief && ignite
+                && level.canSpreadFireAround(pos);
+        BoundedExplosion calculator = new BoundedExplosion(level, age, chunk, grief,
+                playerDamage, maxBlocks, maxEntities, maxDamage);
+        level.explode(null, null, calculator,
+                pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5,
+                radius, false,
+                grief ? Level.ExplosionInteraction.BLOCK : Level.ExplosionInteraction.NONE);
+        if (fire) {
+            int ignited = 0;
+            for (BlockPos affected : calculator.approved) {
+                if (ignited >= 4) break;
+                if (level.canSpreadFireAround(affected) && !PortDecayProviders.isSpawnProtected(age, affected)
+                        && ignite(level, affected)) ignited++;
+            }
+        }
+        return calculator.started;
+    }
+
+    private static boolean ignite(ServerLevel level, BlockPos pos) {
+        if (!level.getBlockState(pos).isAir() || !Blocks.FIRE.defaultBlockState().canSurvive(level, pos))
+            return false;
+        var actor = FakePlayerFactory.getMinecraft(level);
+        actor.setPos(pos.getX() + 0.5, pos.getY(), pos.getZ() + 0.5);
+        var snapshot = net.neoforged.neoforge.common.util.BlockSnapshot.create(level.dimension(), level, pos);
+        BlockState prior = level.getBlockState(pos);
+        if (!level.setBlock(pos, Blocks.FIRE.defaultBlockState(), 3)) return false;
+        var place = new BlockEvent.EntityPlaceEvent(snapshot, prior, actor);
+        NeoForge.EVENT_BUS.post(place);
+        if (place.isCanceled()) {
+            snapshot.restore();
+            return false;
+        }
+        return true;
+    }
+
+    static boolean canMutate(ServerLevel level) {
+        return PortInstabilityConfig.instabilityWorldMutation()
+                && level.getGameRules().get(GameRules.MOB_GRIEFING);
+    }
+
+    static boolean destructiveBlocksAllowed(boolean worldMutation, boolean mobGriefing,
+                                            boolean blockDamage, int maxBlocks) {
+        return worldMutation && mobGriefing && blockDamage && maxBlocks > 0;
+    }
+
+    static boolean protectedBlock(ServerLevel level, PortInstabilityData.Age age, BlockPos pos, BlockState state) {
+        return state.isAir() || state.hasBlockEntity() || state.is(Blocks.TNT)
+                || state.is(PortDecayProviders.PROTECTED) || state.is(BlockTags.PORTALS)
+                || PortDecayProviders.isSpawnProtected(age, pos)
+                || state.getDestroySpeed(level, pos) < 0
+                || BuiltInRegistries.BLOCK.getKey(state.getBlock()).getNamespace().equals(Rivencraft.MOD_ID);
+    }
+
+    private static boolean eligibleEntity(Entity entity) {
+        return eligibleEntity(entity, PortInstabilityConfig.hazardsPlayerDamage());
+    }
+
+    private static boolean eligibleEntity(Entity entity, boolean playerDamage) {
+        return !(entity instanceof Player player) || playerDamage
+                && !player.isCreative() && !player.isSpectator();
+    }
+
+    private static Identifier id(String path) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+    }
+
+    private static final class BoundedExplosion extends ExplosionDamageCalculator {
+        private final ServerLevel level;
+        private final PortInstabilityData.Age age;
+        private final ChunkPos chunk;
+        private final boolean grief;
+        private final boolean playerDamage;
+        private final int maxBlocks;
+        private final int maxEntities;
+        private final int maxDamage;
+        private final Set<BlockPos> approved = new LinkedHashSet<>();
+        private final Set<UUID> damagedEntities = new HashSet<>();
+        private int damaged;
+        private boolean started;
+
+        private BoundedExplosion(ServerLevel level, PortInstabilityData.Age age, ChunkPos chunk, boolean grief,
+                boolean playerDamage, int maxBlocks, int maxEntities, int maxDamage) {
+            this.level = level;
+            this.age = age;
+            this.chunk = chunk;
+            this.grief = grief;
+            this.playerDamage = playerDamage;
+            this.maxBlocks = maxBlocks;
+            this.maxEntities = maxEntities;
+            this.maxDamage = maxDamage;
+        }
+
+        @Override
+        public Optional<Float> getBlockExplosionResistance(Explosion explosion, BlockGetter reader,
+                BlockPos pos, BlockState state, FluidState fluid) {
+            started = true;
+            if (!inLoadedChunk(pos)) return Optional.of(Float.MAX_VALUE);
+            return super.getBlockExplosionResistance(explosion, reader, pos, state, fluid);
+        }
+
+        @Override
+        public boolean shouldBlockExplode(Explosion explosion, BlockGetter reader, BlockPos pos,
+                BlockState state, float power) {
+            if (!grief || !inLoadedChunk(pos) || protectedBlock(level, age, pos, state)) return false;
+            if (approved.contains(pos)) return true;
+            if (approved.size() >= maxBlocks) return false;
+            var actor = FakePlayerFactory.getMinecraft(level);
+            actor.setPos(pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5);
+            var event = new net.neoforged.neoforge.event.level.block.BreakBlockEvent(level, pos, state, actor);
+            NeoForge.EVENT_BUS.post(event);
+            if (event.isCanceled()) return false;
+            approved.add(pos.immutable());
+            return true;
+        }
+
+        @Override
+        public boolean shouldDamageEntity(Explosion explosion, Entity entity) {
+            if (damaged >= maxEntities || !eligibleEntity(entity, playerDamage)
+                    || maxDamage == 0) return false;
+            damaged++;
+            damagedEntities.add(entity.getUUID());
+            return true;
+        }
+
+        @Override
+        public float getEntityDamageAmount(Explosion explosion, Entity entity, float exposure) {
+            return Math.min(super.getEntityDamageAmount(explosion, entity, exposure), maxDamage);
+        }
+
+        @Override
+        public float getKnockbackMultiplier(Entity entity) {
+            return damagedEntities.contains(entity.getUUID()) ? 1.0F : 0.0F;
+        }
+
+        private boolean inLoadedChunk(BlockPos pos) {
+            return level.isInWorldBounds(pos) && ChunkPos.containing(pos).equals(chunk)
+                    && level.getChunkSource().getChunkNow(chunk.x(), chunk.z()) != null;
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortHazardSavedData.java

@@ -0,0 +1,34 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Per-Age random sequence and event cooldowns survive unload and restart. */
+public final class PortHazardSavedData extends SavedData {
+    private static final Codec<PortHazardSavedData> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            net.minecraft.util.ExtraCodecs.NON_NEGATIVE_LONG.optionalFieldOf("attempts", 0L).forGetter(data -> data.attempts),
+            Codec.LONG.optionalFieldOf("last_lightning", Long.MIN_VALUE).forGetter(data -> data.lastLightning),
+            Codec.LONG.optionalFieldOf("last_explosion", Long.MIN_VALUE).forGetter(data -> data.lastExplosion),
+            Codec.LONG.optionalFieldOf("last_meteor", Long.MIN_VALUE).forGetter(data -> data.lastMeteor)
+    ).apply(instance, PortHazardSavedData::new));
+    private static final SavedDataType<PortHazardSavedData> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "hazards"),
+            () -> new PortHazardSavedData(0, Long.MIN_VALUE, Long.MIN_VALUE, Long.MIN_VALUE), CODEC);
+    private long attempts, lastLightning, lastExplosion, lastMeteor;
+    private PortHazardSavedData(long attempts, long lightning, long explosion, long meteor) {
+        this.attempts = attempts; lastLightning = lightning; lastExplosion = explosion; lastMeteor = meteor;
+    }
+    public static PortHazardSavedData get(ServerLevel level) { return level.getDataStorage().computeIfAbsent(TYPE); }
+    public long nextAttempt() { setDirty(); return attempts++; }
+    public boolean ready(boolean lightning, long time, int interval) {
+        long last = lightning ? lastLightning : lastExplosion;
+        return last == Long.MIN_VALUE || time < last || time - last >= interval;
+    }
+    public void record(boolean lightning, long time) { if (lightning) lastLightning = time; else lastExplosion = time; setDirty(); }
+    public boolean meteorReady(long time, int interval) { return lastMeteor == Long.MIN_VALUE || time < lastMeteor || time - lastMeteor >= interval; }
+    public void recordMeteor(long time) { lastMeteor = time; setDirty(); }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortInstabilityCommands.java

@@ -0,0 +1,172 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.brigadier.arguments.BoolArgumentType;
+import com.mojang.brigadier.arguments.IntegerArgumentType;
+import com.mojang.brigadier.arguments.StringArgumentType;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.commands.Commands;
+import net.minecraft.commands.CommandSourceStack;
+import net.minecraft.core.BlockPos;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.fml.common.EventBusSubscriber;
+import net.neoforged.neoforge.event.RegisterCommandsEvent;
+
+/** Scores and test overrides are deliberately operator-only, never book tooltip data. */
+@EventBusSubscriber(modid = Rivencraft.MOD_ID)
+public final class PortInstabilityCommands {
+    private PortInstabilityCommands() {}
+    @SubscribeEvent public static void register(RegisterCommandsEvent event) {
+        event.getDispatcher().register(Commands.literal("rivencraft_port")
+                .requires(Commands.hasPermission(Commands.LEVEL_ADMINS))
+                .then(Commands.literal("instability")
+                        .then(Commands.literal("status").executes(context -> {
+                            var source = context.getSource(); var level = requireAge(source);
+                            var age = PortInstabilityData.get(source.getServer()).age(level);
+                            source.sendSuccess(() -> Component.literal("Age " + level.dimension().identifier()
+                                    + ": frozen score=" + age.score() + ", enabled=" + age.enabled()
+                                    + ", session test score=" + PortInstabilityRuntime.testScore(level)
+                                    + ", protected spawn=" + age.spawn().map(BlockPos::toShortString).orElse("not recorded; re-enter this Age")), false);
+                            source.sendSuccess(() -> Component.literal("  live block score=" + PortBlockInstability.score(level)
+                                    + "; effective score=" + PortInstabilityRuntime.effectiveScore(level)
+                                    + "; difficulty=" + PortInstabilityConfig.instabilityDifficulty()
+                                    + "; samples Age=" + PortBlockInstability.sampledChunks(level) + "/" + PortBlockProfileSavedData.MIN_AGE_SAMPLES
+                                    + ", Overworld=" + PortBlockInstability.sampledChunks(source.getServer().overworld()) + "/" + PortBlockProfileSavedData.MIN_BASELINE_SAMPLES
+                                    + "; profiling=" + PortInstabilityData.get(source.getServer()).supportsProfiling(level)), false);
+                            for (var cost : age.contributions()) source.sendSuccess(() -> Component.literal(
+                                    "  " + cost.reason() + " page=" + cost.page() + " +" + cost.points()), false);
+                            source.sendSuccess(() -> Component.literal("  erosion testing policy (not a saved card): "
+                                    + PortInstabilityRuntime.providerStatus(level, PortEnvironmentalProviders.EROSION)
+                                    + "; current score=" + PortInstabilityRuntime.effectiveScore(level)), false);
+                            for (var provider : PortInstabilityRuntime.plan(level).providers())
+                                source.sendSuccess(() -> Component.literal("  " + provider.id() + " level=" + provider.level()
+                                        + " [" + PortInstabilityRuntime.providerStatus(level, provider.id()) + "]"), false);
+                            return 1;
+                        }))
+                        .then(Commands.literal("enabled").then(Commands.argument("enabled", BoolArgumentType.bool())
+                                .executes(context -> {
+                                    var level = requireAge(context.getSource());
+                                    boolean enabled = BoolArgumentType.getBool(context, "enabled");
+                                    PortInstabilityData.get(level.getServer()).enabled(level, enabled);
+                                    if (!enabled) PortStatusEffectProviders.clearAge(level);
+                                    context.getSource().sendSuccess(() -> Component.literal("Age instability enabled=" + enabled
+                                            + "; saved score and provider selection unchanged"), false);
+                                    return 1;
+                                })))
+                        .then(Commands.literal("test_score").then(Commands.argument("score", IntegerArgumentType.integer(0, 1_000_000))
+                                .executes(context -> {
+                                    var level = requireAge(context.getSource());
+                                    PortInstabilityRuntime.testScore(level, IntegerArgumentType.getInteger(context, "score"));
+                                    PortStatusEffectProviders.clearAge(level);
+                                    context.getSource().sendSuccess(() -> Component.literal("Session-only score override set; frozen score unchanged. Restart or clear_test_score removes it."), false);
+                                    return 1;
+                                })))
+                        .then(Commands.literal("clear_test_score").executes(context -> {
+                            var level = requireAge(context.getSource()); PortInstabilityRuntime.testScore(level, null);
+                            PortStatusEffectProviders.clearAge(level);
+                            context.getSource().sendSuccess(() -> Component.literal("Cleared test override; restored live effective provider selection"), false); return 1;
+                        }))
+                        .then(Commands.literal("decay").then(Commands.argument("color", StringArgumentType.word())
+                                .suggests((context, builder) -> {
+                                    for (var color : net.dnorberg.rivencraft.block.DecayBlock.Color.values())
+                                        if (color.getSerializedName().startsWith(builder.getRemaining())) builder.suggest(color.getSerializedName());
+                                    return builder.buildFuture();
+                                }).executes(context -> decay(context, 1))
+                                .then(Commands.argument("attempts", IntegerArgumentType.integer(1, 32))
+                                        .executes(context -> decay(context, IntegerArgumentType.getInteger(context, "attempts"))))))
+                        .then(Commands.literal("environment").then(Commands.argument("effect", StringArgumentType.word())
+                                .suggests((context, builder) -> {
+                                    for (String effect : java.util.List.of("burning", "erosion"))
+                                        if (effect.startsWith(builder.getRemaining())) builder.suggest(effect);
+                                    return builder.buildFuture();
+                                }).executes(context -> {
+                                    var source = context.getSource(); requireAge(source);
+                                    String effect = StringArgumentType.getString(context, "effect");
+                                    if (!effect.equals("burning") && !effect.equals("erosion")) {
+                                        source.sendFailure(Component.literal("Choose burning or erosion")); return 0;
+                                    }
+                                    int result = PortEnvironmentalProviders.pulseForTesting(source.getPlayerOrException(), effect);
+                                    if (result > 0) source.sendSuccess(() -> Component.literal("Applied " + effect + "; saved score/plan unchanged"), false);
+                                    else source.sendFailure(Component.literal(result == -2 ? "Burning would be extinguished by water or rain"
+                                            : "No effect applied. Check Age/config/provider policy, spawn protection and sky exposure; burning requires Survival/Adventure, erosion requires score >=10000 and a source fluid beside/above the targeted block."));
+                                    return Math.max(0, result);
+                                })))
+                        .then(Commands.literal("meteor").executes(context -> {
+                            var source = context.getSource(); requireAge(source);
+                            int result = PortMeteorProvider.pulseForTesting(source.getPlayerOrException());
+                            if (result > 0) source.sendSuccess(() -> Component.literal("Meteor descent scheduled; impact in 30 ticks. Saved score/plan unchanged."), false);
+                            else source.sendFailure(Component.literal("No meteor scheduled: check cooldown (200 ticks), active flight, safe loaded terrain and Age/config/provider policy."));
+                            return Math.max(0, result);
+                        }))
+                        .then(Commands.literal("hazard").then(Commands.argument("type", StringArgumentType.word())
+                                .suggests((context, builder) -> {
+                                    for (String type : java.util.List.of("lightning", "explosions"))
+                                        if (type.startsWith(builder.getRemaining())) builder.suggest(type);
+                                    return builder.buildFuture();
+                                }).executes(context -> {
+                                    var source = context.getSource(); var level = requireAge(source);
+                                    String type = StringArgumentType.getString(context, "type");
+                                    if (!type.equals("lightning") && !type.equals("explosions")) {
+                                        source.sendFailure(Component.literal("Choose lightning or explosions")); return 0;
+                                    }
+                                    int result = PortHazardProviders.pulseForTesting(level, BlockPos.containing(source.getPosition()), type.equals("lightning"));
+                                    if (result > 0) source.sendSuccess(() -> Component.literal("Triggered " + type
+                                            + " in a nearby loaded chunk; saved score/plan unchanged"), false);
+                                    else source.sendFailure(Component.literal(result < 0 ? "Hazard disabled by config, Age or provider policy"
+                                            : "No hazard triggered: cooldown, protected spawn, unloaded terrain or event cancellation"));
+                                    return Math.max(0, result);
+                                })))
+                        .then(Commands.literal("pulse").then(Commands.argument("provider", StringArgumentType.word())
+                                .suggests((context, builder) -> {
+                                    for (var deck : InstabilityProviderCatalog.Deck.values()) for (var card : InstabilityProviderCatalog.cards(deck))
+                                        if (card.id().getPath().startsWith(builder.getRemaining())) builder.suggest(card.id().getPath());
+                                    return builder.buildFuture();
+                                }).executes(context -> {
+                                    var source = context.getSource(); var level = requireAge(source);
+                                    String name = StringArgumentType.getString(context, "provider");
+                                    Identifier id = Identifier.tryParse(name.contains(":") ? name : "rivencraft:" + name);
+                                    if (id == null || !InstabilityProviderCatalog.contains(id)) throw new com.mojang.brigadier.exceptions.SimpleCommandExceptionType(Component.literal("Unknown instability provider")).create();
+                                    var chunk = net.minecraft.world.level.ChunkPos.containing(BlockPos.containing(source.getPosition()));
+                                    if (level.getChunkSource().getChunkNow(chunk.x(), chunk.z()) == null)
+                                        throw new com.mojang.brigadier.exceptions.SimpleCommandExceptionType(Component.literal("Current chunk must already be loaded")).create();
+                                    var budget = new PortInstabilityRuntime.Budget(1);
+                                    var effect = new PortInstabilityRuntime.Context(level, PortInstabilityData.get(level.getServer()).age(level),
+                                            java.util.List.of(chunk), source.getServer().getTickCount(), budget);
+                                    boolean attempted = PortInstabilityRuntime.invoke(effect, id, 1);
+                                    boolean applied = attempted && budget.applied() > 0;
+                                    if (applied) source.sendSuccess(() -> Component.literal("Applied " + id + " (" + budget.applied() + " successful action in this chunk)"), false);
+                                    else source.sendFailure(Component.literal("No effect applied. Check eligible targets/terrain, sky exposure, existing effects and protection. Provider status: "
+                                            + PortInstabilityRuntime.providerStatus(level, id)));
+                                    return applied ? 1 : 0;
+                                })))));
+    }
+    private static int decay(com.mojang.brigadier.context.CommandContext<CommandSourceStack> context, int attempts)
+            throws com.mojang.brigadier.exceptions.CommandSyntaxException {
+        requireAge(context.getSource());
+        var color = java.util.Arrays.stream(net.dnorberg.rivencraft.block.DecayBlock.Color.values())
+                .filter(value -> value.getSerializedName().equalsIgnoreCase(StringArgumentType.getString(context, "color")))
+                .findFirst().orElse(null);
+        if (color == null) {
+            context.getSource().sendFailure(Component.literal("Choose blue, purple, red or white")); return 0;
+        }
+        int changed = PortDecayProviders.pulseForTesting(context.getSource().getPlayerOrException(), color, attempts);
+        if (changed < 0) {
+            context.getSource().sendFailure(Component.literal("Decay is disabled by config, Age or provider policy")); return 0;
+        }
+        context.getSource().sendSuccess(() -> Component.literal("Decay " + color.getSerializedName() + ": " + changed
+                + " block changes from " + attempts + " bounded attempts; saved score/plan unchanged"), false);
+        var player = context.getSource().getPlayerOrException();
+        var nearby = PortDecaySavedData.get(player.level()).frontier(color).reversed().stream()
+                .filter(pos -> net.minecraft.world.level.ChunkPos.containing(pos).equals(player.chunkPosition()))
+                .limit(4).map(BlockPos::toShortString).toList();
+        if (!nearby.isEmpty()) context.getSource().sendSuccess(() -> Component.literal("Nearby tracked decay: " + nearby), false);
+        return changed;
+    }
+    private static net.minecraft.server.level.ServerLevel requireAge(CommandSourceStack source)
+            throws com.mojang.brigadier.exceptions.CommandSyntaxException {
+        if (!PortInstabilityRuntime.isAge(source.getLevel())) throw new com.mojang.brigadier.exceptions.SimpleCommandExceptionType(
+                Component.literal("Use this command inside a Rivencraft Age")).create();
+        return source.getLevel();
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortInstabilityConfig.java

@@ -0,0 +1,147 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import net.minecraft.resources.Identifier;
+import net.neoforged.neoforge.common.ModConfigSpec;
+
+/** The 1.21.1 scheduler and status-provider defaults, in the port's server-owned config. */
+public final class PortInstabilityConfig {
+    private static ModConfigSpec.BooleanValue enabled, status, players, nonplayers, hostiles, worldMutation, decay;
+    private static ModConfigSpec.IntValue cooldown, ages, providers, actions, level, chunks, active, candidates, duration, decayAttempts;
+    private static ModConfigSpec.ConfigValue<List<? extends String>> disabledProviders;
+    private static ModConfigSpec.BooleanValue hazards, hazardBlocks, hazardPlayers, hazardFire;
+    private static ModConfigSpec.IntValue hazardInterval, hazardChunks, hazardMaxBlocks, hazardEntities, hazardDamage, hazardRadius;
+    private static ModConfigSpec.BooleanValue meteor, meteorBlocks, meteorPlayers, meteorFire;
+    private static ModConfigSpec.IntValue meteorMaxBlocks, meteorEntities, meteorDamage;
+    private static ModConfigSpec.BooleanValue scorch, scorchPlayers, erosion;
+    private static ModConfigSpec.IntValue scorchTargets;
+    private static ModConfigSpec.IntValue difficulty;
+    private static ModConfigSpec.ConfigValue<List<? extends String>> materialOverrides;
+    private PortInstabilityConfig() {}
+    public static void define(ModConfigSpec.Builder builder) {
+        builder.push("instability");
+        enabled = builder.comment("Run implemented instability providers. Saved scores and plans remain unchanged when disabled.")
+                .define("enabled", true);
+        difficulty = builder.comment("Legacy instability difficulty: 0=quarter, 1=half, 2=normal, 3=1.75x; saved scores stay unchanged.")
+                .defineInRange("difficulty", 2, 0, 3);
+        worldMutation = builder.comment("Allow implemented instability providers to change blocks, as in 1.21.1.")
+                .define("world_mutation", true);
+        cooldown = builder.defineInRange("cooldown_ticks", 20, 20, 1200);
+        ages = builder.defineInRange("max_ages_per_tick", 4, 1, 16);
+        providers = builder.defineInRange("max_providers_per_age", 2, 1, 16);
+        actions = builder.defineInRange("max_actions_per_age", 1, 1, 16);
+        level = builder.defineInRange("max_effect_level", 3, 1, 16);
+        chunks = builder.defineInRange("max_loaded_chunks", 16, 1, 64);
+        disabledProviders = builder.comment("Disable particular providers without changing saved selections. Accepts poison or rivencraft:poison.")
+                .defineListAllowEmpty("disabled_providers", List.of(), () -> "poison", value -> value instanceof String text
+                        && Identifier.tryParse(text) != null);
+        builder.pop();
+        builder.push("instability_status_effects");
+        status = builder.define("enabled", true);
+        players = builder.comment("Affect Survival/Adventure players; Creative and Spectator remain exempt.")
+                .define("affect_players", true);
+        nonplayers = builder.define("affect_nonplayers", true);
+        hostiles = builder.define("buff_hostiles", true);
+        active = builder.defineInRange("max_active_per_age", 32, 1, 128);
+        candidates = builder.defineInRange("max_candidates_per_attempt", 8, 1, 16);
+        duration = builder.defineInRange("max_duration_ticks", 200, 20, 200);
+        builder.pop();
+        builder.push("instability_decay");
+        decay = builder.comment("Allow colored decay in loaded Ages. Also requires instability.world_mutation.")
+                .define("enabled", true);
+        decayAttempts = builder.comment("Maximum six-neighbor conversion attempts per provider call; at most one block changes.")
+                .defineInRange("max_attempts_per_call", 4, 1, 6);
+        builder.pop();
+        builder.push("instability_hazards");
+        hazards = builder.comment("Run Legacy lightning and explosion cards in loaded Ages.").define("enabled", true);
+        hazardBlocks = builder.comment("Allow block destruction; also requires world_mutation and mobGriefing.").define("block_damage", true);
+        hazardPlayers = builder.comment("Allow damage to Survival/Adventure players.").define("player_damage", true);
+        hazardFire = builder.comment("Allow ignition where the vanilla fire-spread rule permits it.").define("fire", true);
+        hazardInterval = builder.defineInRange("minimum_gap_ticks", 20, 20, 12000);
+        hazardChunks = builder.defineInRange("max_loaded_chunks", 81, 1, 169);
+        hazardMaxBlocks = builder.defineInRange("max_explosion_blocks", 16, 0, 64);
+        hazardEntities = builder.defineInRange("max_damaged_entities", 8, 0, 32);
+        hazardDamage = builder.defineInRange("max_entity_damage", 12, 0, 40);
+        hazardRadius = builder.comment("Legacy strength 3, bounded to one already-loaded chunk.").defineInRange("explosion_radius", 3, 1, 3);
+        builder.pop();
+        builder.push("instability_meteor");
+        meteor = builder.comment("Run the active Legacy meteor card in loaded Ages.").define("enabled", true);
+        meteorBlocks = builder.comment("Allow impact block destruction; also requires world_mutation and mobGriefing.")
+                .define("block_damage", true);
+        meteorPlayers = builder.comment("Allow impacts to hurt Survival/Adventure players.").define("player_damage", true);
+        meteorFire = builder.comment("Allow impact fire where the vanilla fire-spread rule permits it.").define("fire", true);
+        meteorMaxBlocks = builder.defineInRange("max_impact_blocks", 24, 0, 64);
+        meteorEntities = builder.defineInRange("max_damaged_entities", 8, 0, 32);
+        meteorDamage = builder.defineInRange("max_entity_damage", 12, 0, 40);
+        builder.pop();
+        builder.push("instability_scorching");
+        scorch = builder.comment("Run Legacy's active burning card on sky-exposed entities.").define("enabled", true);
+        scorchPlayers = builder.comment("Allow burning on Survival/Adventure players.").define("affect_players", true);
+        scorchTargets = builder.defineInRange("max_targets_per_pass", 4, 0, 16);
+        builder.pop();
+        builder.push("instability_erosion");
+        erosion = builder.comment("Enable Legacy's dormant erosion effect for testing; no saved card is added.",
+                "Ages with a score of at least 10000 can spread adjacent source fluid into one eligible block per pass.")
+                .define("enabled", true);
+        builder.pop();
+        builder.push("instability_modded_materials");
+        materialOverrides = builder.comment("Recognized ores, mineral blocks and source fluids from installed mods are scored automatically.",
+                "Optional exact modid:block_id=points overrides; zero excludes a block. No content mod is required.")
+                .defineListAllowEmpty("block_weight_overrides", List.of(), () -> "examplemod:rare_ore=4000", PortInstabilityConfig::validMaterialOverride);
+        builder.pop();
+    }
+    private static boolean validMaterialOverride(Object value) {
+        if (!(value instanceof String entry)) return false;
+        int separator = entry.lastIndexOf('=');
+        if (separator < 1) return false;
+        Identifier id = Identifier.tryParse(entry.substring(0, separator));
+        if (id == null || !entry.substring(0, separator).contains(":")
+                || id.getNamespace().equals("minecraft") || id.getNamespace().equals("rivencraft")) return false;
+        try { int weight = Integer.parseInt(entry.substring(separator + 1)); return weight >= 0 && weight <= 100000; }
+        catch (NumberFormatException ignored) { return false; }
+    }
+    public static int instabilityDifficulty() { return difficulty.get(); }
+    public static List<? extends String> moddedMaterialOverrides() { return materialOverrides.get(); }
+    public static boolean scorchEnabled() { return scorch.get(); }
+    public static boolean scorchPlayers() { return scorchPlayers.get(); }
+    public static int scorchMaxTargets() { return scorchTargets.get(); }
+    public static boolean erosionEnabled() { return erosion.get(); }
+    public static boolean meteorEnabled() { return meteor.get(); }
+    public static boolean meteorBlockDamage() { return meteorBlocks.get(); }
+    public static boolean meteorPlayerDamage() { return meteorPlayers.get(); }
+    public static boolean meteorFire() { return meteorFire.get(); }
+    public static int meteorMaxBlocks() { return meteorMaxBlocks.get(); }
+    public static int meteorMaxEntities() { return meteorEntities.get(); }
+    public static int meteorMaxDamage() { return meteorDamage.get(); }
+    public static boolean hazardsEnabled() { return hazards.get(); }
+    public static boolean hazardsBlockDamage() { return hazardBlocks.get(); }
+    public static boolean hazardsPlayerDamage() { return hazardPlayers.get(); }
+    public static boolean hazardsFire() { return hazardFire.get(); }
+    public static int hazardsMinInterval() { return hazardInterval.get(); }
+    public static int hazardsMaxChunks() { return hazardChunks.get(); }
+    public static int hazardsMaxBlocks() { return hazardMaxBlocks.get(); }
+    public static int hazardsMaxEntities() { return hazardEntities.get(); }
+    public static int hazardsMaxDamage() { return hazardDamage.get(); }
+    public static int hazardsExplosionRadius() { return hazardRadius.get(); }
+    public static boolean instabilityWorldMutation() { return worldMutation.get(); }
+    public static boolean decayEnabled() { return decay.get(); }
+    public static int decayMaxAttempts() { return decayAttempts.get(); }
+    public static boolean instabilityEnabled() { return enabled.get(); }
+    public static boolean instabilityProviderEnabled(Identifier id) {
+        return disabledProviders.get().stream().noneMatch(value -> value.equals(id.toString())
+                || id.getNamespace().equals("rivencraft") && value.equals(id.getPath()));
+    }
+    public static int instabilityCooldown() { return cooldown.get(); }
+    public static int instabilityMaxAges() { return ages.get(); }
+    public static int instabilityMaxProviders() { return providers.get(); }
+    public static int instabilityMaxActions() { return actions.get(); }
+    public static int instabilityMaxLevel() { return level.get(); }
+    public static int instabilityMaxChunks() { return chunks.get(); }
+    public static boolean statusEffectsEnabled() { return status.get(); }
+    public static boolean statusEffectsPlayers() { return players.get(); }
+    public static boolean statusEffectsNonplayers() { return nonplayers.get(); }
+    public static boolean statusEffectsHostiles() { return hostiles.get(); }
+    public static int statusEffectsMaxActive() { return active.get(); }
+    public static int statusEffectsMaxCandidates() { return candidates.get(); }
+    public static int statusEffectsMaxDuration() { return duration.get(); }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortInstabilityData.java

@@ -0,0 +1,124 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Frozen creation-time contributions and Legacy deck selections. Never silently rescores older Ages. */
+public final class PortInstabilityData extends SavedData {
+    public record Contribution(String reason, int page, int points) {
+        public static final Codec<Contribution> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+                Codec.STRING.fieldOf("reason").forGetter(Contribution::reason),
+                Codec.INT.fieldOf("page").forGetter(Contribution::page),
+                Codec.intRange(0, Integer.MAX_VALUE).fieldOf("points").forGetter(Contribution::points)
+        ).apply(instance, Contribution::new));
+    }
+    public record Age(long seed, List<Contribution> contributions, PortInstabilityPlan plan, boolean enabled, java.util.Optional<net.minecraft.core.BlockPos> spawn) {
+        public static final Codec<Age> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+                Codec.LONG.fieldOf("seed").forGetter(Age::seed),
+                Contribution.CODEC.listOf().fieldOf("contributions").forGetter(Age::contributions),
+                PortInstabilityPlan.CODEC.fieldOf("plan").forGetter(Age::plan),
+                Codec.BOOL.optionalFieldOf("enabled", true).forGetter(Age::enabled),
+                net.minecraft.core.BlockPos.CODEC.optionalFieldOf("spawn").forGetter(Age::spawn)
+        ).apply(instance, Age::new));
+        public Age { contributions = List.copyOf(contributions); spawn = spawn.map(net.minecraft.core.BlockPos::immutable); }
+        public Age(long seed, List<Contribution> contributions, PortInstabilityPlan plan, boolean enabled) {
+            this(seed, contributions, plan, enabled, java.util.Optional.empty());
+        }
+        public int score() { return contributions.stream().mapToInt(Contribution::points).reduce(0, Math::addExact); }
+    }
+    private static final SavedDataType<PortInstabilityData> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "instability"), () -> new PortInstabilityData(Map.of()),
+            Codec.unboundedMap(Identifier.CODEC, Age.CODEC).fieldOf("ages").codec()
+                    .xmap(PortInstabilityData::new, data -> Map.copyOf(data.ages)));
+    private final Map<Identifier, Age> ages = new HashMap<>();
+    private PortInstabilityData(Map<Identifier, Age> values) { ages.putAll(values); }
+    public static PortInstabilityData get(MinecraftServer server) { return server.overworld().getDataStorage().computeIfAbsent(TYPE); }
+    Age snapshot(Identifier id) { return ages.get(id); }
+    void restore(Identifier id, Age snapshot) {
+        if (snapshot == null) ages.remove(id); else ages.put(id, snapshot);
+        setDirty();
+    }
+    public Age age(ServerLevel level) {
+        Age age = ages.get(level.dimension().identifier());
+        return age != null ? age : new Age(level.getSeed(),
+                List.of(new Contribution("predates_instability", -1, 0)), PortInstabilityPlan.empty(), true);
+    }
+    /** Older neutral Ages stay neutral even if an arrival or enabled flag was later saved. */
+    public boolean supportsProfiling(ServerLevel level) {
+        Age state = ages.get(level.dimension().identifier());
+        return state != null && state.contributions().stream().noneMatch(cost -> cost.reason().equals("predates_instability"));
+    }
+    public void enabled(ServerLevel level, boolean enabled) {
+        Age previous = age(level);
+        ages.put(level.dimension().identifier(), new Age(previous.seed(), previous.contributions(), previous.plan(), enabled, previous.spawn()));
+        setDirty();
+    }
+    /** First resolved arrival remains protected without rescoring or rerolling the Age. */
+    public void recordSpawn(ServerLevel level, net.minecraft.core.BlockPos spawn) {
+        Age previous = age(level);
+        if (previous.spawn().isPresent()) return;
+        ages.put(level.dimension().identifier(), new Age(previous.seed(), previous.contributions(), previous.plan(),
+                previous.enabled(), java.util.Optional.of(spawn.immutable())));
+        setDirty();
+    }
+    public void create(ServerLevel level, List<Identifier> pages, PortAgeTerrain terrain,
+                       PortLighting lighting, PortDayCycle cycle) {
+        Identifier id = level.dimension().identifier();
+        if (ages.containsKey(id)) throw new IllegalArgumentException("Instability already recorded for " + id);
+        List<Contribution> costs = new ArrayList<>();
+        costs.add(new Contribution(pages.isEmpty() ? "random_baseline" : "authored_baseline", -1, 0));
+        for (var diagnostic : net.dnorberg.rivencraft.writing.PortWritingRecovery.recover(pages).diagnostics())
+            costs.add(new Contribution("writing_" + diagnostic.code(), diagnostic.index(), diagnostic.points()));
+        boolean authoredBright = false;
+        Map<Identifier, Integer> structures = new HashMap<>();
+        var biomes = level.getChunkSource().getGenerator().getBiomeSource().possibleBiomes().stream()
+                .flatMap(holder -> holder.unwrapKey().stream()).map(key -> key.identifier()).toList();
+        for (int i = 0; i < pages.size(); i++) {
+            Identifier page = pages.get(i);
+            if (!page.getNamespace().equals("rivencraft")) continue;
+            String path = page.getPath();
+            if (path.equals("lighting/bright")) { costs.add(new Contribution("bright_lighting", i, 500)); authoredBright = true; }
+            if (page.equals(PortAcceleratedTicks.PAGE)) costs.add(new Contribution("accelerated", i, 1000));
+            if (isCorrupted(page)) costs.add(new Contribution("corrupted_" + path.substring(10), i,
+                    path.endsWith("small") ? 2000 : path.endsWith("medium") ? 1000 : 0));
+            // Legacy charges for sky/weather controllers that Cave terrain cannot apply.
+            if (terrain == PortAgeTerrain.CAVE && (PortWeatherMode.forPage(page) != null
+                    || PortDayCycle.isController(page) || PortDayCycle.isPeriod(page)
+                    || PortDayCycle.isPhase(page) || PortDayCycle.isAngle(page) || PortDayCycle.isDirection(page)))
+                costs.add(new Contribution("cave_ignored_" + path.replace('/', '_'), i, 100));
+            if (net.dnorberg.rivencraft.compat.RuinsTemplatePages.isSymbol(page)) {
+                if (structures.merge(page, 1, Integer::sum) > 3)
+                    costs.add(new Contribution("excess_" + path, i, 100));
+            }
+            if (PortStructurePages.supports(page)) {
+                int count = structures.merge(page, 1, Integer::sum);
+                if (count > 3) costs.add(new Contribution("excess_" + path, i, 100));
+                var allowed = PortStructurePages.compatibleBiomes(page, level.registryAccess());
+                if (!allowed.isEmpty() && biomes.stream().anyMatch(biome -> !allowed.contains(biome)))
+                    costs.add(new Contribution("forced_biome_" + path, i, 100));
+            }
+        }
+        if (lighting == PortLighting.BRIGHT && !authoredBright) costs.add(new Contribution("seeded_bright_lighting", -1, 500));
+        int suns = 0;
+        for (var body : cycle.bodies()) if (body.kind() == PortDayCycle.SUN && ++suns > 2)
+            costs.add(new Contribution("extra_sun_" + suns, -1, 1000 * (suns - 2)));
+        int score = costs.stream().mapToInt(Contribution::points).reduce(0, Math::addExact);
+        ages.put(id, new Age(level.getSeed(), costs, PortInstabilityPlan.select(score, level.getSeed()), true));
+        setDirty();
+    }
+    public static boolean isCorrupted(Identifier page) {
+        return page.getNamespace().equals("rivencraft") && switch (page.getPath()) {
+            case "corrupted/large", "corrupted/medium", "corrupted/small" -> true;
+            default -> false;
+        };
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortInstabilityPlan.java

@@ -0,0 +1,60 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Random;
+import net.minecraft.resources.Identifier;
+
+/** Frozen provider selection; handler availability and server settings never reroll this plan. */
+public record PortInstabilityPlan(int version, List<ProviderLevel> providers) {
+    public static final com.mojang.serialization.Codec<PortInstabilityPlan> CODEC =
+            com.mojang.serialization.codecs.RecordCodecBuilder.create(instance -> instance.group(
+                    com.mojang.serialization.Codec.INT.fieldOf("version").forGetter(PortInstabilityPlan::version),
+                    ProviderLevel.CODEC.listOf().fieldOf("providers").forGetter(PortInstabilityPlan::providers)
+            ).apply(instance, PortInstabilityPlan::new));
+    public static final int CURRENT_VERSION = 1;
+
+    public PortInstabilityPlan {
+        if (version != CURRENT_VERSION) throw new IllegalArgumentException("Unsupported provider-plan version " + version);
+        providers = List.copyOf(providers);
+        if (providers.stream().map(ProviderLevel::id).distinct().count() != providers.size()) {
+            throw new IllegalArgumentException("Duplicate provider ID in saved Age plan");
+        }
+    }
+
+    public static PortInstabilityPlan empty() { return new PortInstabilityPlan(CURRENT_VERSION, List.of()); }
+
+    public static PortInstabilityPlan select(int score, long ageSeed) {
+        int roundedScore = score / 500 * 500;
+        Map<Identifier, Integer> levels = new LinkedHashMap<>();
+        for (InstabilityProviderCatalog.Deck deck : InstabilityProviderCatalog.Deck.values()) {
+            int remaining = roundedScore - deck.entryCost();
+            if (remaining <= 0) continue;
+            List<InstabilityProviderCatalog.Card> cards = new ArrayList<>(InstabilityProviderCatalog.cards(deck));
+            Collections.shuffle(cards, new Random(ageSeed ^ (0x9E3779B97F4A7C15L * (deck.ordinal() + 1))));
+            for (InstabilityProviderCatalog.Card card : cards) {
+                if (remaining < card.cost()) break;
+                remaining -= card.cost();
+                levels.merge(card.id(), 1, Integer::sum);
+            }
+        }
+        return new PortInstabilityPlan(CURRENT_VERSION, levels.entrySet().stream()
+                .map(entry -> new ProviderLevel(entry.getKey(), entry.getValue())).toList());
+    }
+
+    public record ProviderLevel(Identifier id, int level) {
+        public static final com.mojang.serialization.Codec<ProviderLevel> CODEC =
+                com.mojang.serialization.codecs.RecordCodecBuilder.create(instance -> instance.group(
+                        Identifier.CODEC.fieldOf("id").forGetter(ProviderLevel::id),
+                        com.mojang.serialization.Codec.intRange(1, 255).fieldOf("level").forGetter(ProviderLevel::level)
+                ).apply(instance, ProviderLevel::new));
+        public ProviderLevel {
+            Objects.requireNonNull(id, "id");
+            if (level < 1 || level > 255) throw new IllegalArgumentException("Invalid provider level " + level);
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortInstabilityRuntime.java

@@ -0,0 +1,178 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.WeakHashMap;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.ChunkPos;
+import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.fml.common.EventBusSubscriber;
+import net.neoforged.neoforge.event.server.ServerStoppingEvent;
+import net.neoforged.neoforge.event.tick.LevelTickEvent;
+
+/** The 1.21.1 bounded Age scheduler. Unported cards remain saved and visibly unavailable to operators. */
+@EventBusSubscriber(modid = Rivencraft.MOD_ID)
+public final class PortInstabilityRuntime {
+    private static final Map<ServerLevel, CachedPlan> PLANS = new WeakHashMap<>();
+    private record CachedPlan(int score, long seed, PortInstabilityPlan plan) {}
+    private static final Map<Identifier, Handler> HANDLERS = new HashMap<>();
+    private static final Map<ServerLevel, Map<Identifier, Long>> FAILURES = new WeakHashMap<>();
+    private static final Map<MinecraftServer, Map<Identifier, Integer>> TEST_SCORES = new WeakHashMap<>();
+    private static final Map<MinecraftServer, TickState> TICKS = new WeakHashMap<>();
+    private PortInstabilityRuntime() {}
+    public static void register(Identifier id, ProviderEffect handler) {
+        register(id, false, handler);
+    }
+    public static void register(Identifier id, boolean worldMutating, ProviderEffect handler) {
+        if (HANDLERS.putIfAbsent(id, new Handler(worldMutating, handler)) != null)
+            throw new IllegalArgumentException("Duplicate instability provider " + id);
+    }
+    public static boolean isAge(ServerLevel level) { return level instanceof PortAgeLevel; }
+    public static PortInstabilityPlan plan(ServerLevel level) {
+        var age = PortInstabilityData.get(level.getServer()).age(level);
+        Integer test = testScore(level);
+        int profile = test == null ? PortBlockInstability.score(level) : 0;
+        int difficulty = PortInstabilityConfig.instabilityDifficulty();
+        if (test == null && difficulty == 2 && profile == 0) return age.plan();
+        int score = test != null ? test : PortBlockInstability.difficultyScore((long) age.score() + profile, difficulty);
+        var cached = PLANS.get(level);
+        if (cached == null || cached.score() != score || cached.seed() != age.seed()) {
+            cached = new CachedPlan(score, age.seed(), PortInstabilityPlan.select(score, age.seed()));
+            PLANS.put(level, cached);
+        }
+        return cached.plan();
+    }
+    public static Integer testScore(ServerLevel level) {
+        return TEST_SCORES.getOrDefault(level.getServer(), Map.of()).get(level.dimension().identifier());
+    }
+    public static int effectiveScore(ServerLevel level) {
+        Integer test = testScore(level);
+        if (test != null) return test;
+        return PortBlockInstability.difficultyScore((long) PortInstabilityData.get(level.getServer()).age(level).score()
+                + PortBlockInstability.score(level), PortInstabilityConfig.instabilityDifficulty());
+    }
+    public static void testScore(ServerLevel level, Integer score) {
+        var values = TEST_SCORES.computeIfAbsent(level.getServer(), ignored -> new HashMap<>());
+        if (score == null) values.remove(level.dimension().identifier()); else values.put(level.dimension().identifier(), score);
+    }
+    @SubscribeEvent public static void tick(LevelTickEvent.Post event) {
+        if (!(event.getLevel() instanceof ServerLevel level) || !isAge(level) || level.players().isEmpty()
+                || !PortInstabilityConfig.instabilityEnabled()) return;
+        var server = level.getServer();
+        long tick = server.getTickCount();
+        int cooldown = PortInstabilityConfig.instabilityCooldown();
+        if (tick % cooldown != 0) return;
+        TickState state = TICKS.computeIfAbsent(server, ignored -> new TickState());
+        if (state.tick != tick) {
+            state.tick = tick;
+            var eligible = new ArrayList<Identifier>();
+            for (var loaded : server.getAllLevels()) if (isAge(loaded) && !loaded.players().isEmpty()
+                    && PortInstabilityData.get(server).age(loaded).enabled() && !plan(loaded).providers().isEmpty())
+                eligible.add(loaded.dimension().identifier());
+            eligible.sort(Comparator.comparing(Identifier::toString));
+            state.eligible = List.copyOf(eligible);
+        }
+        int index = state.eligible.indexOf(level.dimension().identifier());
+        if (index < 0 || state.eligible.size() > PortInstabilityConfig.instabilityMaxAges()
+                && Math.floorMod(index - (int) Math.floorMod(tick / cooldown, state.eligible.size()), state.eligible.size())
+                    >= PortInstabilityConfig.instabilityMaxAges()) return;
+        var age = PortInstabilityData.get(server).age(level);
+        if (!age.enabled()) return;
+        var providers = plan(level).providers();
+        PortHazardProviders.tickPlanned(level, age, tick, providers);
+        PortMeteorProvider.tickPlanned(level, age, tick, providers);
+        PortEnvironmentalProviders.tickPlanned(level, age, tick, providers);
+        var chunks = loadedChunks(level);
+        if (providers.isEmpty() || chunks.isEmpty()) return;
+        Context context = new Context(level, age, chunks, tick, new Budget(PortInstabilityConfig.instabilityMaxActions()));
+        int first = (int) Math.floorMod(tick / cooldown + age.seed(), providers.size());
+        int ran = 0;
+        for (int offset = 0; offset < providers.size() && ran < PortInstabilityConfig.instabilityMaxProviders()
+                && context.budget().remaining() > 0; offset++) {
+            var provider = providers.get((first + offset) % providers.size());
+            if (!PortHazardProviders.isHazard(provider.id()) && !provider.id().equals(PortMeteorProvider.METEORS)
+                    && !PortEnvironmentalProviders.isEnvironmental(provider.id()) && invoke(context, provider.id(), provider.level())) ran++;
+        }
+    }
+    public static boolean invoke(Context context, Identifier id, int level) {
+        if (!PortInstabilityConfig.instabilityEnabled() || !PortInstabilityConfig.instabilityProviderEnabled(id)
+                || !PortInstabilityData.get(context.level().getServer()).age(context.level()).enabled()) return false;
+        Handler handler = HANDLERS.get(id);
+        if (handler == null || handler.worldMutating() && !PortInstabilityConfig.instabilityWorldMutation()) return false;
+        var failures = FAILURES.computeIfAbsent(context.level(), ignored -> new HashMap<>());
+        if (context.serverTick() < failures.getOrDefault(id, 0L)) return false;
+        try {
+            handler.effect().apply(context, id, Math.min(level, PortInstabilityConfig.instabilityMaxLevel()));
+        } catch (RuntimeException exception) {
+            failures.put(id, context.serverTick() + Math.max(200L, PortInstabilityConfig.instabilityCooldown() * 10L));
+            Rivencraft.LOGGER.error("Instability provider {} failed in {}; temporarily quarantined", id,
+                    context.level().dimension().identifier(), exception);
+        }
+        return true;
+    }
+    public static String providerStatus(ServerLevel level, Identifier id) {
+        if (!HANDLERS.containsKey(id)) return "not ported yet";
+        if (!PortInstabilityConfig.instabilityEnabled()) return "global config off";
+        if (!PortInstabilityData.get(level.getServer()).age(level).enabled()) return "Age disabled";
+        if (!PortInstabilityConfig.instabilityProviderEnabled(id)) return "provider config off";
+        if (PortHazardProviders.isHazard(id)) {
+            if (!PortInstabilityConfig.hazardsEnabled()) return "hazards config off";
+        } else if (id.equals(PortMeteorProvider.METEORS)) {
+            if (!PortInstabilityConfig.meteorEnabled()) return "meteor config off";
+        } else if (id.equals(PortEnvironmentalProviders.BURNING)) {
+            if (!PortInstabilityConfig.scorchEnabled()) return "burning config off";
+            if (PortInstabilityConfig.scorchMaxTargets() == 0) return "burning target budget zero";
+        } else if (HANDLERS.get(id).worldMutating()) {
+            if (!PortInstabilityConfig.instabilityWorldMutation()) return "world mutation off";
+            if (id.getPath().startsWith("decay") && !PortInstabilityConfig.decayEnabled()) return "decay config off";
+            if (id.equals(PortEnvironmentalProviders.EROSION)) {
+                if (!PortInstabilityConfig.erosionEnabled()) return "erosion config off";
+                if (!PortHazardProviders.canMutate(level)) return "mobGriefing off";
+                if (effectiveScore(level) < InstabilityProviderCatalog.Deck.DESTRUCTIVE.entryCost()) return "erosion threshold not met";
+            }
+        } else {
+            if (!PortInstabilityConfig.statusEffectsEnabled()) return "status effects config off";
+            if (id.getPath().startsWith("enemy") && !PortInstabilityConfig.statusEffectsHostiles()) return "hostile buffs disabled";
+            if (!id.getPath().startsWith("enemy") && !PortInstabilityConfig.statusEffectsPlayers()
+                    && !PortInstabilityConfig.statusEffectsNonplayers()) return "all general targets disabled";
+        }
+        if (level.getServer().getTickCount() < FAILURES.getOrDefault(level, Map.of()).getOrDefault(id, 0L)) return "quarantined";
+        return level.players().isEmpty() ? "no players in Age" : "eligible; sky, targets and budgets still apply";
+    }
+    static List<ChunkPos> loadedChunks(ServerLevel level) {
+        var chunks = new LinkedHashSet<ChunkPos>();
+        for (var player : level.players()) {
+            ChunkPos center = player.chunkPosition();
+            for (int x = -1; x <= 1; x++) for (int z = -1; z <= 1; z++) {
+                if (level.getChunkSource().getChunkNow(center.x() + x, center.z() + z) != null)
+                    chunks.add(new ChunkPos(center.x() + x, center.z() + z));
+                if (chunks.size() >= PortInstabilityConfig.instabilityMaxChunks()) return List.copyOf(chunks);
+            }
+        }
+        return List.copyOf(chunks);
+    }
+    @SubscribeEvent public static void stopping(ServerStoppingEvent event) {
+        TEST_SCORES.remove(event.getServer()); TICKS.remove(event.getServer()); FAILURES.clear(); PLANS.clear();
+    }
+    public interface ProviderEffect { void apply(Context context, Identifier id, int level); }
+    public record Context(ServerLevel level, PortInstabilityData.Age age, List<ChunkPos> loadedChunks,
+                          long serverTick, Budget budget) { public Context { loadedChunks = List.copyOf(loadedChunks); } }
+    public static final class Budget {
+        private int remaining;
+        private int applied;
+        public Budget(int maximum) { remaining = maximum; }
+        public boolean claim() { if (remaining <= 0) return false; remaining--; return true; }
+        public int remaining() { return remaining; }
+        public void recordApplied() { applied++; }
+        public int applied() { return applied; }
+    }
+    private record Handler(boolean worldMutating, ProviderEffect effect) {}
+    private static final class TickState { long tick = Long.MIN_VALUE; List<Identifier> eligible = List.of(); }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortLibraryCommands.java

@@ -0,0 +1,121 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.brigadier.arguments.IntegerArgumentType;
+import net.minecraft.commands.Commands;
+import net.minecraft.core.BlockPos;
+import net.minecraft.network.chat.Component;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.block.ChestBlock;
+import net.minecraft.world.phys.Vec3;
+import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.fml.common.EventBusSubscriber;
+import net.neoforged.neoforge.event.RegisterCommandsEvent;
+
+/** Explicit operator tools; normal generation does not search or force-load remote chunks. */
+@EventBusSubscriber(modid = "rivencraft")
+public final class PortLibraryCommands {
+    @SubscribeEvent public static void register(RegisterCommandsEvent event) {
+        var root = Commands.literal("rivencraft_port").requires(Commands.hasPermission(Commands.LEVEL_ADMINS));
+        root.then(Commands.literal("library")
+                .then(Commands.literal("test_place").executes(context -> {
+                    var level = context.getSource().getLevel();
+                    var direction = context.getSource().getEntity() instanceof net.minecraft.world.entity.player.Player player
+                            ? player.getDirection() : net.minecraft.core.Direction.NORTH;
+                    var result = PortLibraryFeature.testPlace(level, BlockPos.containing(context.getSource().getPosition()), direction,
+                            level.getSeed(), PortLibraryWriting.get(level.getServer()).symbols(level.dimension().identifier()));
+                    if (result.isEmpty()) { context.getSource().sendFailure(Component.literal("No clear placement nearby; use open ground with headroom.")); return 0; }
+                    context.getSource().sendSuccess(() -> Component.literal("Library placed. Chest: " + result.get().toShortString()), false);
+                    return 1;
+                }))
+                .then(Commands.literal("test_spacing").then(Commands.argument("chunks", IntegerArgumentType.integer(1, 32))
+                        .executes(context -> {
+                            var level = context.getSource().getLevel();
+                            if (!RuntimeAgeBackend.savedAges(level.getServer()).containsKey(level.dimension().identifier()))
+                                throw new IllegalArgumentException("Use this test override inside a Rivencraft Age");
+                            int spacing = IntegerArgumentType.getInteger(context, "chunks");
+                            PortLibraryFeature.setTestSpacing(level.getSeed(), spacing);
+                            context.getSource().sendSuccess(() -> Component.literal("Session-only library spacing: " + spacing
+                                    + " chunks. Applies to newly generated chunks; 32 restores normal spacing."), false);
+                            return 1;
+                        })))
+                .then(Commands.literal("candidate").executes(context -> {
+                    var level = context.getSource().getLevel();
+                    var origin = ChunkPos.containing(BlockPos.containing(context.getSource().getPosition()));
+                    ChunkPos best = null;
+                    long distance = Long.MAX_VALUE;
+                    for (int spacing : new int[]{32, PortLibraryFeature.spacing(level.getSeed())}) {
+                        int rx = Math.floorDiv(origin.x(), spacing), rz = Math.floorDiv(origin.z(), spacing);
+                        for (int dx = -2; dx <= 2; dx++) for (int dz = -2; dz <= 2; dz++) {
+                            var candidate = PortLibraryFeature.candidateChunk(level.getSeed(), rx + dx, rz + dz, spacing);
+                            long x = candidate.x() - origin.x(), z = candidate.z() - origin.z();
+                            long d = x * x + z * z;
+                            if (d < distance) { best = candidate; distance = d; }
+                        }
+                    }
+                    var candidate = best;
+                    context.getSource().sendSuccess(() -> Component.literal("Nearest candidate chunk " + candidate
+                            + ", center X=" + (candidate.getMinBlockX() + 8) + " Z=" + (candidate.getMinBlockZ() + 8)
+                            + ". A candidate is not a guaranteed library: footing, slope and clear space must pass."), false);
+                    return 1;
+                }))
+                .then(Commands.literal("probe").executes(context -> {
+                    var level = context.getSource().getLevel();
+                    var chunk = level.getChunkAt(BlockPos.containing(context.getSource().getPosition()));
+                    var chest = PortLibraryFeature.libraryChest(chunk);
+                    if (chest.isPresent()) context.getSource().sendSuccess(() -> Component.literal("Generated library chest: " + chest.get().toShortString()), false);
+                    else {
+                        var check = PortLibraryFeature.check(level, chunk.getPos(), level.getSeed());
+                        context.getSource().sendSuccess(() -> Component.literal(check.eligible() ? "Eligible library candidate, floor Y=" + check.floorY()
+                                : "No library in this chunk: " + check.reason()), false);
+                    }
+                    return 1;
+                }))
+                .then(Commands.literal("inspect_loot").executes(context -> {
+                    var level = context.getSource().getLevel();
+                    var chunk = level.getChunkAt(BlockPos.containing(context.getSource().getPosition()));
+                    var pos = PortLibraryFeature.libraryChest(chunk);
+                    if (pos.isEmpty()) { context.getSource().sendFailure(Component.literal("No marked library chest in this chunk.")); return 0; }
+                    var chest = (net.minecraft.world.level.block.entity.ChestBlockEntity) level.getBlockEntity(pos.get());
+                    var items = new java.util.ArrayList<String>();
+                    for (int i = 0; i < chest.getContainerSize(); i++) {
+                        var item = chest.getItem(i); // Materializes loot exactly as opening the chest does.
+                        if (!item.isEmpty()) items.add(item.getCount() + "x " + item.getHoverName().getString());
+                    }
+                    long stands = chunk.getBlockEntities().values().stream()
+                            .filter(be -> be instanceof net.dnorberg.rivencraft.block.entity.BookStandBlockEntity).count();
+                    context.getSource().sendSuccess(() -> Component.literal("Library at " + pos.get().toShortString()
+                            + "; stands in this chunk=" + stands + "; chest=" + items), false);
+                    return 1;
+                }))
+                .then(Commands.literal("nearest_loaded").executes(context -> {
+                    var player = context.getSource().getPlayerOrException();
+                    var level = player.level();
+                    var origin = player.chunkPosition();
+                    BlockPos best = null; double distance = Double.MAX_VALUE;
+                    for (int x = origin.x() - 16; x <= origin.x() + 16; x++) for (int z = origin.z() - 16; z <= origin.z() + 16; z++) {
+                        var chunk = level.getChunkSource().getChunkNow(x, z);
+                        if (chunk == null) continue;
+                        var found = PortLibraryFeature.libraryChest(chunk);
+                        if (found.isPresent()) {
+                            double d = player.distanceToSqr(Vec3.atCenterOf(found.get()));
+                            if (d < distance) { best = found.get(); distance = d; }
+                        }
+                    }
+                    if (best == null) { context.getSource().sendFailure(Component.literal("No library in loaded chunks within 16 chunks. Use candidate or test_spacing to explore new terrain.")); return 0; }
+                    var facing = level.getBlockState(best).getValue(ChestBlock.FACING);
+                    var feet = best.relative(facing, 2).relative(facing.getCounterClockWise());
+                    var target = Vec3.atBottomCenterOf(feet);
+                    if (!level.getBlockState(feet.below()).isFaceSturdy(level, feet.below(), net.minecraft.core.Direction.UP)
+                            || !level.getFluidState(feet).isEmpty() || !level.getFluidState(feet.above()).isEmpty()
+                            || !level.noCollision(player, player.getBoundingBox().move(target.subtract(player.position())))) {
+                        context.getSource().sendFailure(Component.literal("Library found at " + best.toShortString() + " but its aisle is obstructed.")); return 0;
+                    }
+                    player.teleportTo(level, target.x, target.y, target.z, java.util.Set.of(), facing.getOpposite().toYRot(), 0, true);
+                    return 1;
+                })));
+        event.getDispatcher().register(root);
+    }
+    @SubscribeEvent public static void stopped(net.neoforged.neoforge.event.server.ServerStoppedEvent event) {
+        PortLibraryFeature.clearTestSpacing();
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortLibraryFeature.java

@@ -0,0 +1,363 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.ConcurrentHashMap;
+import net.dnorberg.rivencraft.PortConfig;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.PortSymbolPages;
+import net.dnorberg.rivencraft.block.BookStandBlock;
+import net.dnorberg.rivencraft.block.entity.BookStandBlockEntity;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.resources.Identifier;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.phys.AABB;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.ChestBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.entity.ChestBlockEntity;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.LevelChunk;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+import net.minecraft.world.level.storage.loot.LootTable;
+import net.minecraft.world.level.block.Rotation;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructurePlaceSettings;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+
+/** Sparse, page-free Age library. Its entire footprint lives in its candidate chunk. */
+public final class PortLibraryFeature {
+    public static final int REGION = 32;
+    static final int FOOTPRINT = 11;
+    private static final int OFFSET_BOUND = 24;
+    private static final int MAX_SUPPORT_DEPTH = 24;
+    private static final int SALT = 14357617;
+    private static final int TEST_SALT = 0x4C494252;
+    private static final String CHEST_MARKER = "RivencraftLibrary";
+    private static final ConcurrentHashMap<Long, Integer> TEST_SPACING = new ConcurrentHashMap<>();
+    // x, y, z, clockwise turns relative to the left stand. The middle row
+    // faces across the room; the far stand faces back toward the entrance.
+    private static final int[][] STANDS = {{6, 1, 2, 0}, {8, 1, 4, 1}, {8, 1, 5, 1},
+            {8, 1, 6, 1}, {6, 1, 8, 2}};
+    private static final Identifier TEMPLATE = Identifier.fromNamespaceAndPath(
+            "rivencraft", "mystcraft_library");
+    private static final ResourceKey<LootTable> CHEST_LOOT = ResourceKey.create(Registries.LOOT_TABLE,
+            Identifier.fromNamespaceAndPath("rivencraft", "chests/mystcraft_library"));
+
+    private PortLibraryFeature() {}
+
+    record Site(int x, int z, int rotation) {}
+
+    public static int spacing(long seed) {
+        return TEST_SPACING.getOrDefault(seed, REGION);
+    }
+
+    /** Session-only testing override; normal 32-chunk sites always remain eligible. */
+    public static void setTestSpacing(long seed, int chunks) {
+        if (chunks < 1 || chunks > REGION) throw new IllegalArgumentException("Invalid library spacing " + chunks);
+        if (chunks == REGION) TEST_SPACING.remove(seed);
+        else TEST_SPACING.put(seed, chunks);
+    }
+
+    public static void clearTestSpacing() {
+        TEST_SPACING.clear();
+    }
+
+    /** The single deterministic candidate in one Legacy-sized region. */
+    public static ChunkPos candidateChunk(long seed, int regionX, int regionZ) {
+        return candidateChunk(seed, regionX, regionZ, REGION);
+    }
+
+    public static ChunkPos candidateChunk(long seed, int regionX, int regionZ, int spacing) {
+        if (spacing < 1 || spacing > REGION) throw new IllegalArgumentException("Invalid library spacing " + spacing);
+        WorldgenRandom random = new WorldgenRandom(new LegacyRandomSource(0L));
+        random.setLargeFeatureWithSalt(seed, regionX, regionZ,
+                spacing == REGION ? SALT : TEST_SALT ^ spacing);
+        int bound = spacing == REGION ? OFFSET_BOUND : spacing;
+        return new ChunkPos(regionX * spacing + random.nextInt(bound),
+                regionZ * spacing + random.nextInt(bound));
+    }
+
+    static Site site(long seed, ChunkPos chunk) {
+        Site normal = site(seed, chunk, REGION);
+        return normal != null ? normal : spacing(seed) == REGION ? null : site(seed, chunk, spacing(seed));
+    }
+
+    private static Site site(long seed, ChunkPos chunk, int spacing) {
+        int rx = Math.floorDiv(chunk.x(), spacing);
+        int rz = Math.floorDiv(chunk.z(), spacing);
+        WorldgenRandom random = new WorldgenRandom(new LegacyRandomSource(0L));
+        random.setLargeFeatureWithSalt(seed, rx, rz,
+                spacing == REGION ? SALT : TEST_SALT ^ spacing);
+        int bound = spacing == REGION ? OFFSET_BOUND : spacing;
+        int candidateX = rx * spacing + random.nextInt(bound);
+        int candidateZ = rz * spacing + random.nextInt(bound);
+        if (chunk.x() != candidateX || chunk.z() != candidateZ) return null;
+        return new Site(chunk.getMinBlockX() + 2, chunk.getMinBlockZ() + 2, random.nextInt(4));
+    }
+
+    /** A saved marker distinguishes a generated library from player-built chests. */
+    public static Optional<BlockPos> libraryChest(LevelChunk chunk) {
+        return chunk.getBlockEntities().entrySet().stream()
+                .filter(entry -> entry.getValue() instanceof ChestBlockEntity chest
+                        && chest.getPersistentData().getBooleanOr(CHEST_MARKER, false))
+                .map(java.util.Map.Entry::getKey).findFirst();
+    }
+
+    /** Recognize libraries generated before the chest marker was introduced. */
+    public static Optional<BlockPos> libraryChest(LevelChunk chunk, long seed) {
+        Optional<BlockPos> marked = libraryChest(chunk);
+        if (marked.isPresent()) return marked;
+        Site site = site(seed, chunk.getPos());
+        if (site == null) return Optional.empty();
+        for (var entry : chunk.getBlockEntities().entrySet()) {
+            if (!(entry.getValue() instanceof ChestBlockEntity chest)) continue;
+            int y = entry.getKey().getY();
+            BlockPos.MutableBlockPos cursor = new BlockPos.MutableBlockPos();
+            if (!entry.getKey().equals(mapped(site, cursor, 4, y, 2))
+                    || !chunk.getBlockState(mapped(site, cursor, 2, y, 2)).is(Blocks.BOOKSHELF)
+                    || !chunk.getBlockState(mapped(site, cursor, 2, y + 1, 2)).is(Blocks.BOOKSHELF)
+                    || !chunk.getBlockState(mapped(site, cursor, 4, y + 6, 2)).is(Blocks.OAK_PLANKS))
+                continue;
+            chest.getPersistentData().putBoolean(CHEST_MARKER, true);
+            chest.setChanged();
+            return Optional.of(entry.getKey());
+        }
+        return Optional.empty();
+    }
+
+    /** Open interior aisle, directly above the cobblestone floor. */
+    public static BlockPos arrival(long seed, ChunkPos chunk, int chestY) {
+        Site site = site(seed, chunk);
+        if (site == null) throw new IllegalArgumentException("Not a library candidate chunk: " + chunk);
+        return mapped(site, new BlockPos.MutableBlockPos(), 5, chestY, 4).immutable();
+    }
+
+    public record PlacementCheck(String reason, int floorY, int[][] heights) {
+        public boolean eligible() { return reason == null; }
+    }
+
+    /** Inspect one candidate without placing blocks. The same test gates natural placement. */
+    public static PlacementCheck check(WorldGenLevel level, ChunkPos chunk, long seed) {
+        Site site = site(seed, chunk);
+        if (site == null) return rejected("not a candidate chunk");
+        BlockPos.MutableBlockPos cursor = new BlockPos.MutableBlockPos();
+        int low = Integer.MAX_VALUE;
+        int high = Integer.MIN_VALUE;
+        int[][] heights = new int[FOOTPRINT][FOOTPRINT];
+        for (int x = 0; x < FOOTPRINT; x++) for (int z = 0; z < FOOTPRINT; z++) {
+            int wx = site.x() + x;
+            int wz = site.z() + z;
+            int y = level.getHeight(Heightmap.Types.WORLD_SURFACE_WG, wx, wz);
+            // The heightmap includes tree canopies. Libraries sit on terrain, not leaves.
+            while (y > level.getMinY() + 2) {
+                BlockState below = level.getBlockState(cursor.set(wx, y - 1, wz));
+                if (!below.isAir() && !isVegetation(below)) break;
+                y--;
+            }
+            if (y < level.getMinY() + 2) return rejected("no surface footing");
+            BlockState ground = level.getBlockState(cursor.set(wx, y - 1, wz));
+            if (!ground.getFluidState().isEmpty()) return rejected("fluid at ground level");
+            if (ground.hasBlockEntity() || !ground.isFaceSturdy(level, cursor, Direction.UP))
+                return rejected("ground is not sturdy terrain");
+            heights[x][z] = y;
+            low = Math.min(low, y);
+            high = Math.max(high, y);
+        }
+        if (high + 10 >= level.getMaxY()) return rejected("insufficient build height");
+        if (high - low > MAX_SUPPORT_DEPTH) return rejected("slope exceeds support depth ("
+                + (high - low) + " > " + MAX_SUPPORT_DEPTH + ")");
+        // Check the entire raised foundation and house. Foliage can be cleared, but not
+        // structures, fluids, or block entities already occupying this volume.
+        for (int x = 0; x < FOOTPRINT; x++) for (int z = 0; z < FOOTPRINT; z++)
+            for (int y = heights[x][z]; y <= high + 10; y++) {
+                BlockState state = level.getBlockState(cursor.set(site.x() + x, y, site.z() + z));
+                if (!state.getFluidState().isEmpty()) return rejected("fluid inside footprint");
+                if (state.hasBlockEntity()) return rejected("block entity inside footprint");
+                if (!(state.isAir() || state.canBeReplaced() || isVegetation(state)))
+                    return rejected("solid obstruction inside footprint: "
+                            + state.getBlock().getDescriptionId());
+            }
+        return new PlacementCheck(null, high, heights);
+    }
+
+    private static PlacementCheck rejected(String reason) {
+        return new PlacementCheck(reason, 0, null);
+    }
+
+    private static boolean isVegetation(BlockState state) {
+        return state.is(BlockTags.LEAVES) || state.is(BlockTags.LOGS)
+                || state.is(BlockTags.FLOWERS) || state.is(BlockTags.SAPLINGS)
+                || !state.isAir() && state.canBeReplaced() && state.getFluidState().isEmpty();
+    }
+
+    static boolean generate(WorldGenLevel level, ChunkAccess chunk, long seed,
+                            List<Identifier> ageSymbols) {
+        Site site = site(seed, chunk.getPos());
+        if (site == null) return false;
+        PlacementCheck check = check(level, chunk.getPos(), seed);
+        if (!check.eligible()) return false;
+        BlockPos.MutableBlockPos cursor = new BlockPos.MutableBlockPos();
+        for (int x = 0; x < FOOTPRINT; x++) for (int z = 0; z < FOOTPRINT; z++)
+            for (int y = check.heights()[x][z]; y <= check.floorY() + 10; y++) {
+                BlockPos pos = cursor.set(site.x() + x, y, site.z() + z);
+                if (isVegetation(level.getBlockState(pos))) level.setBlock(pos, Blocks.AIR.defaultBlockState(), 2);
+            }
+        return build(level, site, check.floorY(), check.heights(), seed, ageSymbols);
+    }
+
+    /** Explicit OP testing placement. Never overwrites existing blocks or entities. */
+    public static Optional<BlockPos> testPlace(ServerLevel level, BlockPos playerPos, Direction facing,
+                                               long seed, List<Identifier> ageSymbols) {
+        Direction horizontal = facing.getAxis().isHorizontal() ? facing : Direction.NORTH;
+        BlockPos center = playerPos.relative(horizontal, 13);
+        int rotation = switch (horizontal) {
+            case NORTH -> 2;
+            case EAST -> 3;
+            case WEST -> 1;
+            default -> 0;
+        };
+        Site site = new Site(center.getX() - FOOTPRINT / 2, center.getZ() - FOOTPRINT / 2, rotation);
+        int floorY = playerPos.getY() + 2;
+        for (int x = 0; x < FOOTPRINT; x++) for (int z = 0; z < FOOTPRINT; z++)
+            floorY = Math.max(floorY, level.getHeight(Heightmap.Types.WORLD_SURFACE,
+                    site.x() + x, site.z() + z) + 1);
+        if (floorY + 10 >= level.getMaxY() || floorY - playerPos.getY() > 20)
+            return Optional.empty();
+        BlockPos.MutableBlockPos cursor = new BlockPos.MutableBlockPos();
+        for (int x = 0; x < FOOTPRINT; x++) for (int z = 0; z < FOOTPRINT; z++)
+            for (int y = floorY; y <= floorY + 10; y++) {
+                BlockPos pos = cursor.set(site.x() + x, y, site.z() + z);
+                if (!level.getWorldBorder().isWithinBounds(pos) || !level.getBlockState(pos).isAir())
+                    return Optional.empty();
+            }
+        if (!level.getEntities(null, new AABB(site.x(), floorY, site.z(),
+                site.x() + FOOTPRINT, floorY + 11, site.z() + FOOTPRINT)).isEmpty())
+            return Optional.empty();
+        if (!build(level, site, floorY, null, seed, ageSymbols)) return Optional.empty();
+        return Optional.of(mapped(site, cursor, 4, floorY + 1, 2).immutable());
+    }
+
+    private static boolean build(WorldGenLevel level, Site site, int floorY, int[][] heights,
+                                 long seed, List<Identifier> ageSymbols) {
+        BlockPos.MutableBlockPos cursor = new BlockPos.MutableBlockPos();
+        var template = level.getLevel().getStructureTemplateManager().get(TEMPLATE).orElse(null);
+        if (template == null || template.getSize().getX() != FOOTPRINT
+                || template.getSize().getY() != FOOTPRINT || template.getSize().getZ() != FOOTPRINT)
+            return false;
+        for (int x = 0; x < FOOTPRINT; x++) for (int z = 0; z < FOOTPRINT; z++) {
+            for (int y = heights == null ? floorY : heights[x][z] - 1; y <= floorY; y++)
+                place(level, site, cursor, x, y, z, Blocks.COBBLESTONE.defaultBlockState());
+        }
+        Rotation rotation = switch (site.rotation()) {
+            case 1 -> Rotation.CLOCKWISE_90;
+            case 2 -> Rotation.CLOCKWISE_180;
+            case 3 -> Rotation.COUNTERCLOCKWISE_90;
+            default -> Rotation.NONE;
+        };
+        BlockPos origin = new BlockPos(site.x(), floorY, site.z());
+        var settings = new StructurePlaceSettings().setRotation(rotation)
+                .setRotationPivot(new BlockPos(5, 0, 5)).setIgnoreEntities(true);
+        long positionSalt = new ChunkPos(site.x() >> 4, site.z() >> 4).pack();
+        if (!template.placeInWorld(level, origin, origin, settings,
+                RandomSource.create(seed ^ positionSalt), 2)) return false;
+
+        BlockPos chestPos = mapped(site, cursor, 4, floorY + 1, 2).immutable();
+        level.setBlock(chestPos, Blocks.CHEST.defaultBlockState().setValue(ChestBlock.FACING,
+                Direction.from2DDataValue(site.rotation())), 2);
+        PortConfig.LibraryLootMode mode = PortConfig.LIBRARY_LOOT_MODE.get();
+        boolean ageOnly = mode == PortConfig.LibraryLootMode.AGE_ONLY;
+        List<Identifier> symbols = symbolsForLoot(ageSymbols, mode);
+        RandomSource random = RandomSource.create(seed ^ positionSalt ^ SALT);
+        if (level.getBlockEntity(chestPos) instanceof ChestBlockEntity chest) {
+            chest.getPersistentData().putBoolean(CHEST_MARKER, true);
+            chest.setChanged();
+            if (ageOnly) {
+                // Pages are frozen in the Age generator, then saved as real chest items.
+                boolean[] occupied = new boolean[chest.getContainerSize()];
+                for (int i = 0, count = symbols.isEmpty() ? 0 : 4 + random.nextInt(5); i < count; i++) {
+                    int slot;
+                    do slot = random.nextInt(occupied.length); while (occupied[slot]);
+                    occupied[slot] = true;
+                    chest.setItem(slot, page(symbols, random));
+                }
+            } else {
+                chest.setLootTable(CHEST_LOOT, seed ^ chestPos.asLong());
+            }
+        }
+        for (int[] standCoords : STANDS) {
+            BlockPos pos = mapped(site, cursor, standCoords[0], floorY + standCoords[1], standCoords[2]).immutable();
+            if (!level.getBlockState(pos).isAir()) continue;
+            level.setBlock(pos, Rivencraft.BOOK_STAND.get().defaultBlockState()
+                    .setValue(BookStandBlock.FACING, standFacing(site, standCoords[3]))
+                    .setValue(BookStandBlock.HAS_BOOK, true), 2);
+            if (level.getBlockEntity(pos) instanceof BookStandBlockEntity stand) {
+                stand.setBook(symbols.isEmpty() ? new ItemStack(Items.BOOK) : page(symbols, random));
+            }
+        }
+        return true;
+    }
+
+    static Direction standFacing(Site site, int clockwiseTurns) {
+        return Direction.from2DDataValue((site.rotation() + clockwiseTurns) & 3);
+    }
+
+    /** Correct older generated stands in place, retaining their block entities and pages. */
+    public static int repairStandFacings(ServerLevel level, LevelChunk chunk, long seed) {
+        Site site = site(seed, chunk.getPos());
+        if (site == null || libraryChest(chunk, seed).isEmpty()) return -1;
+        int changed = 0;
+        BlockPos.MutableBlockPos cursor = new BlockPos.MutableBlockPos();
+        int chestY = libraryChest(chunk, seed).orElseThrow().getY();
+        for (int[] standCoords : STANDS) {
+            BlockPos pos = mapped(site, cursor, standCoords[0], chestY, standCoords[2]);
+            BlockState state = level.getBlockState(pos);
+            if (!state.is(Rivencraft.BOOK_STAND.get())) continue;
+            Direction facing = standFacing(site, standCoords[3]);
+            if (state.getValue(BookStandBlock.FACING) != facing) {
+                level.setBlock(pos, state.setValue(BookStandBlock.FACING, facing), 3);
+                changed++;
+            }
+        }
+        return changed;
+    }
+
+    static List<Identifier> symbolsForLoot(List<Identifier> ageSymbols, PortConfig.LibraryLootMode mode) {
+        return symbolsForLoot(ageSymbols, mode, PortRandomPagePolicy.configured());
+    }
+
+    static List<Identifier> symbolsForLoot(List<Identifier> ageSymbols, PortConfig.LibraryLootMode mode,
+                                          PortRandomPagePolicy policy) {
+        return mode == PortConfig.LibraryLootMode.AGE_ONLY
+                ? ageSymbols.stream().filter(policy::allows).filter(id -> PortSymbolPages.find(id) != null).distinct().toList()
+                : PortSymbolPages.libraryCandidateIds().stream().filter(policy::allows).toList();
+    }
+
+    private static ItemStack page(List<Identifier> symbols, RandomSource random) {
+        return PageItem.createSymbolPage(symbols.get(random.nextInt(symbols.size())));
+    }
+
+    private static BlockPos.MutableBlockPos mapped(Site site, BlockPos.MutableBlockPos cursor, int x, int y, int z) {
+        return switch (site.rotation()) {
+            case 1 -> cursor.set(site.x() + FOOTPRINT - 1 - z, y, site.z() + x);
+            case 2 -> cursor.set(site.x() + FOOTPRINT - 1 - x, y, site.z() + FOOTPRINT - 1 - z);
+            case 3 -> cursor.set(site.x() + z, y, site.z() + FOOTPRINT - 1 - x);
+            default -> cursor.set(site.x() + x, y, site.z() + z);
+        };
+    }
+
+    private static void place(WorldGenLevel level, Site site, BlockPos.MutableBlockPos cursor,
+                              int x, int y, int z, BlockState state) {
+        level.setBlock(mapped(site, cursor, x, y, z), state, 2);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortLibraryWriting.java

@@ -0,0 +1,26 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Written pages for library Age-only loot, kept outside the legacy backend index codec. */
+final class PortLibraryWriting extends SavedData {
+    static final Codec<PortLibraryWriting> CODEC = Codec.unboundedMap(Identifier.CODEC, Identifier.CODEC.listOf())
+            .fieldOf("ages").codec().xmap(PortLibraryWriting::new, data -> Map.copyOf(data.pages));
+    static final SavedDataType<PortLibraryWriting> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "library_writing"), () -> new PortLibraryWriting(Map.of()), CODEC);
+    private final Map<Identifier, List<Identifier>> pages = new HashMap<>();
+    private PortLibraryWriting(Map<Identifier, List<Identifier>> pages) { pages.forEach((id, list) -> this.pages.put(id, List.copyOf(list))); }
+    static PortLibraryWriting get(MinecraftServer server) { return server.overworld().getDataStorage().computeIfAbsent(TYPE); }
+    List<Identifier> symbols(Identifier id) { return pages.getOrDefault(id, List.of()); }
+    void put(Identifier id, List<Identifier> symbols) {
+        if (symbols.isEmpty()) pages.remove(id); else pages.put(id, List.copyOf(symbols));
+        setDirty();
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortMeteorProvider.java

@@ -0,0 +1,133 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+import java.util.WeakHashMap;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.particles.ParticleTypes;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.fml.common.EventBusSubscriber;
+import net.neoforged.neoforge.event.level.LevelEvent;
+import net.neoforged.neoforge.event.server.ServerStoppingEvent;
+import net.neoforged.neoforge.event.tick.LevelTickEvent;
+
+/** The 1.21.1 meteor's short particle descent and bounded impact, without a new entity. */
+@EventBusSubscriber(modid = Rivencraft.MOD_ID)
+public final class PortMeteorProvider {
+    public static final Identifier METEORS = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "meteors");
+    private static final int METEOR_FLIGHT_TICKS = 30;
+    private static final int MAX_ACTIVE_AGES = 16;
+    private static final Map<ServerLevel, Meteor> ACTIVE = new WeakHashMap<>();
+    private PortMeteorProvider() {}
+    public static void register() {
+        PortInstabilityRuntime.register(METEORS, false, (context, id, level) -> {
+            if (PortInstabilityRuntime.isAge(context.level())) scheduleMeteor(context, level, false);
+        });
+    }
+    static void tickPlanned(ServerLevel level, PortInstabilityData.Age age, long tick,
+                            List<PortInstabilityPlan.ProviderLevel> providers) {
+        var card = providers.stream().filter(provider -> provider.id().equals(METEORS)).findFirst();
+        if (card.isEmpty() || !PortInstabilityConfig.meteorEnabled()) return;
+        var chunks = PortHazardProviders.loadedChunksNearPlayers(level, PortInstabilityConfig.hazardsMaxChunks());
+        if (!chunks.isEmpty()) PortInstabilityRuntime.invoke(new PortInstabilityRuntime.Context(level, age, chunks,
+                tick, new PortInstabilityRuntime.Budget(1)), METEORS, card.get().level());
+    }
+    /** Skip the chance roll only; retain per-Age policy, loading, active-flight and cooldown checks. */
+    public static int pulseForTesting(ServerPlayer player) {
+        ServerLevel level = player.level();
+        if (!PortInstabilityRuntime.isAge(level)) return -1;
+        var age = PortInstabilityData.get(level.getServer()).age(level);
+        if (!PortInstabilityConfig.instabilityEnabled() || !PortInstabilityConfig.meteorEnabled()
+                || !age.enabled() || !PortInstabilityConfig.instabilityProviderEnabled(METEORS)) return 0;
+        var chunks = PortHazardProviders.loadedChunksNearPlayers(level, 16);
+        if (chunks.isEmpty()) return 0;
+        return scheduleMeteor(new PortInstabilityRuntime.Context(level, age, chunks,
+                level.getServer().getTickCount(), new PortInstabilityRuntime.Budget(1)), 1, true) ? 1 : 0;
+    }
+
+    private static boolean scheduleMeteor(PortInstabilityRuntime.Context context, int effectiveLevel, boolean force) {
+        if (!PortInstabilityConfig.meteorEnabled() || ACTIVE.containsKey(context.level())
+                || ACTIVE.size() >= MAX_ACTIVE_AGES) return false;
+        PortHazardSavedData data = PortHazardSavedData.get(context.level());
+        long gameTime = context.level().getGameTime();
+        if (!data.meteorReady(gameTime, 200)) return false;
+        Random random = new Random(context.age().seed() ^ data.nextAttempt() * 0xD1B54A32D192ED03L
+                ^ METEORS.hashCode());
+        if (!force && random.nextDouble() >= PortHazardProviders.legacyChance(context.loadedChunks().size(),
+                PortInstabilityConfig.instabilityCooldown(), effectiveLevel, 50000)) return false;
+        int start = random.nextInt(context.loadedChunks().size());
+        for (int offset = 0; offset < Math.min(16, context.loadedChunks().size()); offset++) {
+            ChunkPos chunk = context.loadedChunks().get((start + offset) % context.loadedChunks().size());
+            int x = chunk.getMinBlockX() + 6 + random.nextInt(4);
+            int z = chunk.getMinBlockZ() + 6 + random.nextInt(4);
+            int surfaceY = context.level().getHeight(Heightmap.Types.MOTION_BLOCKING_NO_LEAVES, x, z);
+            BlockPos impact = new BlockPos(x, surfaceY, z);
+            if (surfaceY >= context.level().getMaxY() - 8
+                    || !PortHazardProviders.safeTarget(context, impact, 8)) continue;
+            if (!context.budget().claim()) return false;
+            int startY = Math.min(context.level().getMaxY() - 2, surfaceY + 48);
+            data.recordMeteor(gameTime);
+            ACTIVE.put(context.level(), new Meteor(chunk, impact, startY, METEOR_FLIGHT_TICKS));
+            context.level().playSound(null, impact, Rivencraft.METEOR_ROAR.get(), SoundSource.WEATHER, 2.0F, 1.0F);
+            context.budget().recordApplied();
+            return true;
+        }
+        return false;
+    }
+
+    @SubscribeEvent
+    public static void onLevelTickPost(LevelTickEvent.Post event) {
+        if (!(event.getLevel() instanceof ServerLevel level)) return;
+        Meteor meteor = ACTIVE.get(level);
+        if (meteor == null) return;
+        if (!PortInstabilityConfig.instabilityEnabled() || !PortInstabilityConfig.meteorEnabled()
+                || !PortInstabilityRuntime.isAge(level)
+                || level.players().isEmpty()
+                || level.getChunkSource().getChunkNow(meteor.chunk().x(), meteor.chunk().z()) == null) {
+            ACTIVE.remove(level);
+            return;
+        }
+        var age = PortInstabilityData.get(level.getServer()).age(level);
+        if (!age.enabled()
+                || !PortInstabilityConfig.instabilityProviderEnabled(METEORS)) {
+            ACTIVE.remove(level);
+            return;
+        }
+        int remaining = meteor.remaining() - 1;
+        if (remaining <= 0) {
+            ACTIVE.remove(level); // clear before impact so an exception cannot replay it
+            PortHazardProviders.explodeBounded(level, age, meteor.chunk(), meteor.impact(),
+                    PortInstabilityConfig.meteorBlockDamage(), PortInstabilityConfig.meteorPlayerDamage(),
+                    PortInstabilityConfig.meteorFire(), PortInstabilityConfig.meteorMaxBlocks(),
+                    PortInstabilityConfig.meteorMaxEntities(), PortInstabilityConfig.meteorMaxDamage(), 3);
+            return;
+        }
+        double progress = 1.0 - remaining / (double) METEOR_FLIGHT_TICKS;
+        double y = meteor.startY() + (meteor.impact().getY() - meteor.startY()) * progress;
+        double x = meteor.impact().getX() + 0.5 + (1.0 - progress) * 2.0;
+        double z = meteor.impact().getZ() + 0.5 + (1.0 - progress) * 2.0;
+        level.sendParticles(ParticleTypes.FLAME, x, y, z, 5, 0.25, 0.25, 0.25, 0.01);
+        level.sendParticles(ParticleTypes.LARGE_SMOKE, x, y, z, 2, 0.3, 0.3, 0.3, 0.02);
+        ACTIVE.put(level, new Meteor(meteor.chunk(), meteor.impact(), meteor.startY(), remaining));
+    }
+
+    @SubscribeEvent
+    public static void onServerStopping(ServerStoppingEvent event) {
+        ACTIVE.clear(); // an interrupted descent is cancelled, never replayed after restart
+    }
+
+    @SubscribeEvent
+    public static void onLevelUnload(LevelEvent.Unload event) {
+        if (event.getLevel() instanceof ServerLevel level) ACTIVE.remove(level);
+    }
+
+    private record Meteor(ChunkPos chunk, BlockPos impact, int startY, int remaining) {}
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortNotebookProbe.java

@@ -0,0 +1,94 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.menu.NotebookMenu;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.core.BlockPos;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.RegistryOps;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.Container;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.inventory.ContainerInput;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.Blocks;
+
+/** Disposable-world menu, ownership, codec and chest-persistence fixtures. */
+final class PortNotebookProbe {
+    private static final BlockPos CHEST = new BlockPos(0, 64, 0);
+    private PortNotebookProbe() {}
+
+    static void create(ServerLevel level) {
+        PortAgeTravel.findLanding(level);
+        level.setBlock(CHEST, Blocks.CHEST.defaultBlockState(), 3);
+        Container chest = (Container) level.getBlockEntity(CHEST);
+        var player = net.neoforged.neoforge.common.util.FakePlayerFactory.get(level,
+                new com.mojang.authlib.GameProfile(java.util.UUID.fromString("1043b9f3-f348-4a73-b585-e0de13fd5c27"), "RivenNotebookProbe"));
+        int output = 0;
+        try {
+            for (boolean folder : List.of(false, true)) for (var hand : InteractionHand.values()) {
+                player.getInventory().clearContent();
+                player.getInventory().setSelectedSlot(0);
+                ItemStack collection = new ItemStack(folder ? Rivencraft.COLLATION_FOLDER.get() : Rivencraft.NOTEBOOK.get());
+                player.setItemInHand(hand, collection);
+                var menu = new NotebookMenu(1, player.getInventory(), hand);
+                int capacity = CollationFolderItem.capacity(collection);
+                if (!menu.stillValid(player) || menu.pageCapacity() != capacity
+                        || menu.getSlot(0).mayPlace(PageItem.createLinkPanelPage())
+                        || menu.getSlot(0).mayPlace(new ItemStack(net.minecraft.world.item.Items.DIAMOND)))
+                    throw new IllegalStateException("Notebook capacity/page acceptance regression");
+                ItemStack page = PageItem.createSymbolPage(Identifier.fromNamespaceAndPath("rivencraft", "terrain/flat"));
+                player.getInventory().setItem(9, page.copyWithCount(3));
+                menu.clicked(NotebookMenu.NOTEBOOK_SLOTS, 0, ContainerInput.QUICK_MOVE, player);
+                if (!player.getInventory().getItem(9).isEmpty() || contents(collection).pageCount() != 3)
+                    throw new IllegalStateException("Notebook shift insertion regression");
+                for (int i = 0; i < 3; i++) menu.clicked(i, 0, ContainerInput.QUICK_MOVE, player);
+                if (contents(collection).pageCount() != 0) throw new IllegalStateException("Notebook shift extraction regression");
+                menu.getSlot(capacity - 1).set(page.copy());
+                if (contents(collection).pageCount() != 1 || !contents(collection).pages().get(0).isEmpty()
+                        || contents(collection).pages().get(capacity - 1).isEmpty())
+                    throw new IllegalStateException("Notebook sparse position regression");
+                if (!menu.clickMenuButton(player, NotebookMenu.MOVE_PREVIOUS_BASE + capacity - 1)
+                        || !contents(collection).pages().get(capacity - 1).isEmpty())
+                    throw new IllegalStateException("Notebook page movement regression");
+                if (folder && menu.getSlot(capacity).mayPlace(page))
+                    throw new IllegalStateException("Folder exceeded 27 positions");
+                menu.clicked(NotebookMenu.NOTEBOOK_SLOTS + 27, 0, ContainerInput.PICKUP, player);
+                if (player.getItemInHand(hand) != collection || !menu.getCarried().isEmpty())
+                    throw new IllegalStateException("Notebook active item was movable");
+                var ops = RegistryOps.create(com.mojang.serialization.JsonOps.INSTANCE, level.registryAccess());
+                var encoded = NotebookContents.CODEC.encodeStart(ops, contents(collection)).getOrThrow();
+                var decoded = NotebookContents.CODEC.parse(ops, encoded).getOrThrow();
+                var buffer = new RegistryFriendlyByteBuf(io.netty.buffer.Unpooled.buffer(), level.registryAccess());
+                try {
+                    NotebookContents.STREAM_CODEC.encode(buffer, decoded);
+                    decoded = NotebookContents.STREAM_CODEC.decode(buffer);
+                    if (decoded.pageCount() != 1 || decoded.pages().get(capacity - 2).isEmpty())
+                        throw new IllegalStateException("Notebook save/network codec regression");
+                } finally { buffer.release(); }
+                chest.setItem(output++, collection.copy());
+                player.setItemInHand(hand, ItemStack.EMPTY);
+            }
+        } finally { player.getInventory().clearContent(); }
+        verify(level);
+    }
+
+    private static NotebookContents contents(ItemStack stack) {
+        return stack.getOrDefault(Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY);
+    }
+
+    static void verify(ServerLevel level) {
+        if (!(level.getBlockEntity(CHEST) instanceof Container chest)) throw new IllegalStateException("Fixture chest missing");
+        for (int i = 0; i < 4; i++) {
+            var collection = chest.getItem(i);
+            int capacity = i < 2 ? 252 : 27;
+            if (CollationFolderItem.capacity(collection) != capacity || contents(collection).pageCount() != 1
+                    || contents(collection).pages().get(capacity - 2).isEmpty())
+                throw new IllegalStateException("Notebook chest persistence regression: " + i);
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortProgressionPlayer.java

@@ -0,0 +1,25 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.authlib.GameProfile;
+import net.minecraft.server.PlayerAdvancements;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.datafix.DataFixers;
+import net.minecraft.world.level.storage.LevelResource;
+import net.neoforged.neoforge.common.util.FakePlayer;
+
+/** FakePlayer normally discards all advancement progress; fixtures need vanilla tracking. */
+final class PortProgressionPlayer extends FakePlayer {
+    private PlayerAdvancements progress;
+
+    PortProgressionPlayer(ServerLevel level, GameProfile profile) { super(level, profile); }
+
+    @Override public PlayerAdvancements getAdvancements() {
+        if (progress == null) {
+            var server = level().getServer();
+            progress = new PlayerAdvancements(DataFixers.getDataFixer(), server.getPlayerList(),
+                    server.getAdvancements(), server.getWorldPath(LevelResource.PLAYER_ADVANCEMENTS_DIR)
+                            .resolve(getUUID() + ".json"), this);
+        }
+        return progress;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortProgressionProbe.java

@@ -0,0 +1,101 @@
+package net.dnorberg.rivencraft.age;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
+import net.dnorberg.rivencraft.block.entity.InkMixerBlockEntity;
+import net.dnorberg.rivencraft.menu.InkMixerMenu;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.inventory.ContainerInput;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+
+/** Disposable operator fixture for loaded advancement data and committed action awards. */
+final class PortProgressionProbe {
+    /** Operator-fixture assertion; deliberately requires the real loaded advancement. */
+    static boolean isComplete(net.minecraft.server.level.ServerPlayer player, String path) {
+        var advancement = player.level().getServer().getAdvancements().get(
+                net.minecraft.resources.Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "progression/" + path));
+        if (advancement == null) throw new IllegalStateException("Missing progression advancement: " + path);
+        return player.getAdvancements().getOrStartProgress(advancement).isDone();
+    }
+
+
+    static void recipeDiscovery(ServerLevel level) {
+        var materials = java.util.Map.of(
+                "ink_vial", Items.DYE.black(),
+                "ink_mixer", Items.GLASS_BOTTLE,
+                "book_binder", Items.IRON_INGOT,
+                "crystal_block", Rivencraft.CRYSTAL_SHARD.get(),
+                "notebook", Items.LEATHER,
+                "writing_desk", Items.FEATHER);
+        for (var entry : materials.entrySet()) {
+            var id = net.minecraft.resources.Identifier.fromNamespaceAndPath("rivencraft", entry.getKey());
+            var key = net.minecraft.resources.ResourceKey.create(net.minecraft.core.registries.Registries.RECIPE, id);
+            var player = new PortProgressionPlayer(level, new com.mojang.authlib.GameProfile(
+                    java.util.UUID.nameUUIDFromBytes(id.toString().getBytes(java.nio.charset.StandardCharsets.UTF_8)),
+                    "RivenRecipe"));
+            var advancement = level.getServer().getAdvancements().get(
+                    net.minecraft.resources.Identifier.fromNamespaceAndPath("rivencraft", "recipes/misc/" + entry.getKey()));
+            if (advancement == null || level.getServer().getRecipeManager().byKey(key).isEmpty())
+                throw new IllegalStateException("Missing recipe/discovery data: " + id);
+            var progress = player.getAdvancements();
+            net.minecraft.advancements.triggers.CriteriaTriggers.INVENTORY_CHANGED.trigger(player,
+                    player.getInventory(), new ItemStack(Items.COBBLESTONE));
+            if (player.getRecipeBook().contains(key))
+                throw new IllegalStateException("Wrong material unlocked " + id);
+            var material = new ItemStack(entry.getValue());
+            player.getInventory().setItem(0, material);
+            net.minecraft.advancements.triggers.CriteriaTriggers.INVENTORY_CHANGED.trigger(player, player.getInventory(), material);
+            if (!player.getRecipeBook().contains(key) || !progress.getOrStartProgress(advancement).isDone())
+                throw new IllegalStateException("Material did not unlock " + id);
+            // The second criterion supports /recipe give without first obtaining its material.
+            var other = new PortProgressionPlayer(level, new com.mojang.authlib.GameProfile(
+                    java.util.UUID.randomUUID(), "RivenRecipeGive"));
+            if (other.getRecipeBook().contains(key)) throw new IllegalStateException("Recipe leaked between players");
+            other.awardRecipes(java.util.List.of(level.getServer().getRecipeManager().byKey(key).orElseThrow()));
+            if (!other.getAdvancements().getOrStartProgress(advancement).isDone())
+                throw new IllegalStateException("Recipe unlock criterion did not complete " + id);
+        }
+    }
+
+    static void run(ServerLevel level) {
+        var player = new PortProgressionPlayer(level,
+                new com.mojang.authlib.GameProfile(java.util.UUID.fromString("b428c3ef-57a6-43dc-95e8-441b6a171107"), "RivenProgression"));
+        var pos = new BlockPos(4, 64, 0);
+        player.setPos(4.5, 64, 2.5);
+        level.setBlock(pos, Rivencraft.INK_MIXER.get().defaultBlockState(), 3);
+        var mixer = (InkMixerBlockEntity) level.getBlockEntity(pos);
+        try {
+            // Every tree node must decode; portal advancement waits for its missing item/feature port.
+            for (String path : new String[]{"root", "page", "linking_book", "link_panel", "copy_page", "bind_age", "enter_age"})
+                if (isComplete(player, path))
+                    throw new IllegalStateException("Fixture requires fresh player advancement data");
+            var menu = new InkMixerMenu(1, player.getInventory(), mixer);
+            menu.clicked(InkMixerMenu.RESULT, 0, ContainerInput.PICKUP, player);
+            if (isComplete(player, "link_panel"))
+                throw new IllegalStateException("Empty Mixer awarded progression");
+            mixer.setItem(InkMixerBlockEntity.PAPER, new ItemStack(Items.PAPER, 2));
+            mixer.setItem(InkMixerBlockEntity.INK, new ItemStack(Rivencraft.INK_VIAL.get()));
+            menu.broadcastChanges();
+            if (isComplete(player, "link_panel"))
+                throw new IllegalStateException("Mixer preview awarded progression");
+            menu.clicked(InkMixerMenu.RESULT, 0, ContainerInput.PICKUP, player);
+            if (!isComplete(player, "link_panel"))
+                throw new IllegalStateException("Mixer pickup did not award progression");
+            menu.setCarried(ItemStack.EMPTY);
+            var advancement = level.getServer().getAdvancements().get(
+                    net.minecraft.resources.Identifier.fromNamespaceAndPath("rivencraft", "progression/link_panel"));
+            player.getAdvancements().revoke(advancement, "completed");
+            menu.quickMoveStack(player, InkMixerMenu.RESULT);
+            if (!isComplete(player, "link_panel"))
+                throw new IllegalStateException("Mixer shift pickup did not award progression");
+            ProgressionAdvancements.awardAgeTravel(player);
+            if (!isComplete(player, "enter_age"))
+                throw new IllegalStateException("Registered Age did not award entry");
+        } finally {
+            player.getInventory().clearContent();
+            level.removeBlock(pos, false);
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortRandomAgeSelection.java

@@ -17,32 +17,35 @@ public final class PortRandomAgeSelection {
     public record Selection(PortAgeTerrain terrain, PortBiomePlan biomes) {}
 
     public static Selection select(MinecraftServer server, long seed) {
+        return select(server, seed, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static Selection select(MinecraftServer server, long seed, PortRandomPagePolicy policy) {
         // Match the 1.21.1 Legacy-rank choices: Standard and Flat are common;
         // the other terrain families are rarer. The sorted order is deliberate.
-        PortAgeTerrain terrain = weighted(new Random(seed ^ 0x5445525241494E4CL),
-                List.of(PortAgeTerrain.AMPLIFIED, PortAgeTerrain.CAVE, PortAgeTerrain.FLAT,
-                        PortAgeTerrain.ISLAND, PortAgeTerrain.STANDARD, PortAgeTerrain.VOID),
-                new int[]{1, 1, 5, 1, 6, 1});
+        PortAgeTerrain terrain = terrain(seed, policy);
         if (terrain == PortAgeTerrain.VOID)
             return new Selection(terrain, new PortBiomePlan(PortBiomePlan.Distribution.SINGLE,
                     List.of(Identifier.withDefaultNamespace("the_void"))));
 
-        PortBiomePlan.Distribution distribution = weighted(new Random(seed ^ 0x524956454E435241L),
-                List.of(PortBiomePlan.Distribution.NATIVE, PortBiomePlan.Distribution.SINGLE,
-                        PortBiomePlan.Distribution.MEDIUM, PortBiomePlan.Distribution.TILED,
-                        PortBiomePlan.Distribution.GRID, PortBiomePlan.Distribution.TINY,
-                        PortBiomePlan.Distribution.SMALL, PortBiomePlan.Distribution.LARGE,
-                        PortBiomePlan.Distribution.HUGE),
-                new int[]{3, 3, 3, 1, 1, 1, 1, 1, 1});
+        PortBiomePlan.Distribution distribution = distribution(seed, policy);
         List<Identifier> eligible = eligibleBiomes(server, terrain);
-        if (eligible.size() < 2 && distribution != PortBiomePlan.Distribution.NATIVE)
-            distribution = PortBiomePlan.Distribution.SINGLE;
-        // 26.3 has no native multi-cave biome source; choose a seeded Cave
-        // biome rather than silently using Lush Caves for every random Age.
-        if (terrain == PortAgeTerrain.CAVE && distribution == PortBiomePlan.Distribution.NATIVE)
-            distribution = PortBiomePlan.Distribution.SINGLE;
+        if (distribution != PortBiomePlan.Distribution.NATIVE) {
+            var filtered = new ArrayList<>(policy.eligible(eligible, PortRegistryPages::biomePageId));
+            // Native presets are not Page-selected. Other controllers retain their minimum,
+            // with the same preferred-biome/registry fallback as 1.21.1.
+            int minimum = distribution == PortBiomePlan.Distribution.SINGLE ? 1 : 2;
+            Identifier preferred = Identifier.withDefaultNamespace(terrain == PortAgeTerrain.CAVE ? "deep_dark" : "plains");
+            if (filtered.size() < minimum && eligible.contains(preferred) && !filtered.contains(preferred))
+                filtered.add(preferred);
+            for (var candidate : eligible)
+                if (filtered.size() < minimum && !filtered.contains(candidate)) filtered.add(candidate);
+            eligible = List.copyOf(filtered);
+            if (eligible.size() < 2) distribution = PortBiomePlan.Distribution.SINGLE;
+        }
         if (distribution == PortBiomePlan.Distribution.NATIVE)
-            return new Selection(terrain, new PortBiomePlan(distribution, List.of()));
+            return new Selection(terrain, new PortBiomePlan(distribution,
+                    terrain == PortAgeTerrain.CAVE ? eligible : List.of()));
 
         int count = distribution == PortBiomePlan.Distribution.SINGLE ? 1 : 2;
         if (count > 1) {
@@ -54,29 +57,65 @@ public final class PortRandomAgeSelection {
         return new Selection(terrain, new PortBiomePlan(distribution, shuffled.subList(0, count)));
     }
 
+    public static List<PortAgeTerrain> terrains() {
+        return List.of(PortAgeTerrain.AMPLIFIED, PortAgeTerrain.CAVE, PortAgeTerrain.FLAT,
+                PortAgeTerrain.ISLAND, PortAgeTerrain.STANDARD, PortAgeTerrain.VOID);
+    }
+
+    public static PortAgeTerrain terrain(long seed) {
+        return terrain(seed, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static PortAgeTerrain terrain(long seed, PortRandomPagePolicy policy) {
+        return ranked(new Random(seed ^ 0x5445525241494E4CL), terrains(), new int[]{3, 3, 2, 3, 1, 3},
+                policy, value -> PortRandomPagePolicy.page("terrain", value), PortAgeTerrain.STANDARD);
+    }
+
+    /** First AgeTraits draw in 1.21.1; shared by random and partly authored Ages. */
+    public static PortBiomePlan.Distribution distribution(long seed) {
+        return distribution(seed, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static PortBiomePlan.Distribution distribution(long seed, PortRandomPagePolicy policy) {
+        return ranked(new Random(seed ^ 0x524956454E435241L),
+                List.of(PortBiomePlan.Distribution.NATIVE, PortBiomePlan.Distribution.SINGLE,
+                        PortBiomePlan.Distribution.MEDIUM, PortBiomePlan.Distribution.TILED,
+                        PortBiomePlan.Distribution.GRID, PortBiomePlan.Distribution.TINY,
+                        PortBiomePlan.Distribution.SMALL, PortBiomePlan.Distribution.LARGE,
+                        PortBiomePlan.Distribution.HUGE),
+                new int[]{1, 1, 1, 2, 2, 2, 2, 2, 2}, policy,
+                value -> PortRandomPagePolicy.page("biome", value), PortBiomePlan.Distribution.NATIVE);
+    }
+
     public static List<Identifier> eligibleBiomes(MinecraftServer server, PortAgeTerrain terrain) {
         if (terrain == PortAgeTerrain.VOID) return List.of(Identifier.withDefaultNamespace("the_void"));
         if (terrain == PortAgeTerrain.CAVE) {
-            List<Identifier> caves = server.registryAccess().lookupOrThrow(Registries.BIOME).listElements()
-                    .filter(PortRegistryPages::isCaveBiome)
-                    .map(holder -> holder.key().identifier())
-                    .sorted().toList();
-            return caves.isEmpty() ? List.of(Identifier.withDefaultNamespace("lush_caves")) : caves;
+            return caveBiomes(server.registryAccess());
         }
         List<Identifier> surface = server.overworld().getChunkSource().getGenerator().getBiomeSource()
                 .possibleBiomes().stream().flatMap(holder -> holder.unwrapKey().stream())
-                .map(key -> key.identifier()).distinct().sorted(Comparator.naturalOrder()).toList();
+                .map(key -> key.identifier()).filter(id -> !id.equals(PortRegistryPages.DEFERRED_PLACEHOLDER))
+                .distinct().sorted(Comparator.naturalOrder()).toList();
+        surface = java.util.stream.Stream.concat(surface.stream(),
+                net.dnorberg.rivencraft.compat.TerraBlenderBiomes.overworld(server.registryAccess()).stream())
+                .distinct().sorted().toList();
         return surface.isEmpty() ? List.of(Identifier.withDefaultNamespace("plains")) : surface;
     }
 
-    static <T> T weighted(Random random, List<T> choices, int[] weights) {
-        int total = 0;
-        for (int weight : weights) total += weight;
-        int ticket = random.nextInt(total);
-        for (int index = 0; index < choices.size(); index++) {
-            ticket -= weights[index];
-            if (ticket < 0) return choices.get(index);
-        }
-        throw new IllegalStateException("Random Age ticket was not consumed");
+    public static List<Identifier> caveBiomes(net.minecraft.core.HolderLookup.Provider registries) {
+        net.dnorberg.rivencraft.compat.TerraBlenderBiomes.nether(registries);
+        var caves = registries.lookupOrThrow(Registries.BIOME).listElements()
+                .filter(PortRegistryPages::isCaveBiome).map(holder -> holder.key().identifier()).sorted().toList();
+        return caves.isEmpty() ? List.of(Identifier.withDefaultNamespace("lush_caves")) : caves;
     }
+
+    private static <T> T ranked(Random random, List<T> choices, int[] ranks, PortRandomPagePolicy policy,
+                                java.util.function.Function<T, Identifier> page, T fallback) {
+        var options = new ArrayList<PortRankedChoice.Option<T>>();
+        for (int i = 0; i < choices.size(); i++)
+            options.add(new PortRankedChoice.Option<>(choices.get(i), ranks[i]));
+        var eligible = policy.eligible(options, option -> page.apply(option.value()));
+        return eligible.isEmpty() ? fallback : PortRankedChoice.choose(random, eligible);
+    }
+
 }

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortRandomFeatureSelection.java

@@ -14,16 +14,25 @@ public final class PortRandomFeatureSelection {
 
     public static Selection select(net.minecraft.server.MinecraftServer server, long seed,
                                     PortAgeTerrain terrain, PortBiomePlan biomes) {
-        var base = select(seed, terrain);
-        var structures = PortRandomStructureSelection.select(server, seed, terrain, biomes);
+        return select(server, seed, terrain, biomes, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static Selection select(net.minecraft.server.MinecraftServer server, long seed,
+                                    PortAgeTerrain terrain, PortBiomePlan biomes, PortRandomPagePolicy policy) {
+        var base = select(seed, terrain, policy);
+        var structures = PortRandomStructureSelection.select(server, seed, terrain, biomes, policy);
         var plan = base.terrain();
         plan = plan == null ? new PortTerrainFeaturePlan(List.of(), false, 0, false, structures.structures(), List.of(), true)
                     : new PortTerrainFeaturePlan(plan.choices(), plan.skylands(), plan.denseOres(), plan.starFissures(),
-                            structures.structures(), plan.carvers(), true);
+                            structures.structures(), plan.carvers(), true, plan.ruins());
         return new Selection(base.rocks(), base.lakes(), plan, structures.dungeons());
     }
 
     public static Selection select(long seed, PortAgeTerrain terrain) {
+        return select(seed, terrain, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static Selection select(long seed, PortAgeTerrain terrain, PortRandomPagePolicy policy) {
         var random = new Random(seed ^ 0x4D4154455249414CL);
         int count = random.nextInt(3);
         var terrainPage = id("terrain/" + terrain.name().toLowerCase(java.util.Locale.ROOT));
@@ -31,12 +40,13 @@ public final class PortRandomFeatureSelection {
         for (String name : List.of("rocks", "floating_islands", "tendrils", "spheres", "spikes", "obelisks",
                 "surface_lakes", "deep_lakes", "lava_lakes")) {
             var page = id("feature/" + name);
-            if (PortAuthoredWriting.supports(List.of(terrainPage, page)))
+            if (policy.allows(page) && PortAuthoredWriting.supports(List.of(terrainPage, page)))
                 candidates.add(new PortRankedChoice.Option<>(page, rank(name)));
         }
         var pages = new ArrayList<Identifier>();
         pages.add(terrainPage);
-        List<Identifier> solids = PortRegistryPages.solidMaterialIds(), fluids = PortRegistryPages.fluidMaterialIds();
+        List<Identifier> solids = policy.eligible(PortRegistryPages.solidMaterialIds(), PortRegistryPages::blockPageId);
+        List<Identifier> fluids = policy.eligible(PortRegistryPages.fluidMaterialIds(), PortRegistryPages::blockPageId);
         for (int selected = 0; selected < count && !candidates.isEmpty();) {
             Identifier feature = PortRankedChoice.choose(random, candidates);
             candidates.removeIf(option -> option.value().equals(feature));
@@ -46,12 +56,12 @@ public final class PortRandomFeatureSelection {
             pages.add(feature);
             selected++;
         }
-        if (terrain != PortAgeTerrain.FLAT && terrain != PortAgeTerrain.VOID
+        if (policy.allows(PortTerrainFeaturePlan.SKYLANDS) && terrain != PortAgeTerrain.FLAT && terrain != PortAgeTerrain.VOID
                 && Math.floorMod(mix(seed ^ 0x534B594C414E4453L), 8) == 0)
             pages.add(PortTerrainFeaturePlan.SKYLANDS);
-        if (terrain != PortAgeTerrain.CAVE && terrain != PortAgeTerrain.VOID && random.nextInt(10) == 0)
+        if (policy.allows(PortTerrainFeaturePlan.CRYSTAL_FORMATIONS) && terrain != PortAgeTerrain.CAVE && terrain != PortAgeTerrain.VOID && random.nextInt(10) == 0)
             pages.add(PortTerrainFeaturePlan.CRYSTAL_FORMATIONS);
-        if (randomStarFissure(seed)) pages.add(PortTerrainFeaturePlan.STAR_FISSURES);
+        if (policy.allows(PortTerrainFeaturePlan.STAR_FISSURES) && randomStarFissure(seed)) pages.add(PortTerrainFeaturePlan.STAR_FISSURES);
         return new Selection(PortAuthoredWriting.rockPlan(pages, seed), PortAuthoredWriting.lakePlan(pages, seed),
                 PortAuthoredWriting.terrainFeaturePlan(pages, seed), 0);
     }

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortRandomPagePolicy.java

@@ -0,0 +1,66 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+import net.dnorberg.rivencraft.PortConfig;
+import net.minecraft.resources.Identifier;
+
+/** Creation-time eligibility; the resolved Age settings are saved, never reselected on reload. */
+public record PortRandomPagePolicy(Set<Identifier> allowlist, Set<Identifier> blocklist) {
+    public static final PortRandomPagePolicy UNRESTRICTED = new PortRandomPagePolicy(Set.of(), Set.of());
+
+    public PortRandomPagePolicy {
+        allowlist = Set.copyOf(allowlist);
+        blocklist = Set.copyOf(blocklist);
+    }
+
+    public static PortRandomPagePolicy configured() {
+        return new PortRandomPagePolicy(parse(PortConfig.RANDOM_PAGE_ALLOWLIST.get()),
+                parse(PortConfig.RANDOM_PAGE_BLOCKLIST.get()));
+    }
+
+    private static Set<Identifier> parse(List<? extends String> ids) {
+        return ids.stream().map(PortRandomPagePolicy::parsePageId).collect(Collectors.toUnmodifiableSet());
+    }
+
+    /** Server config IDs may omit the built-in Rivencraft namespace. */
+    public static Identifier parsePageId(String value) {
+        Identifier id = Identifier.tryParse(value.contains(":") ? value : "rivencraft:" + value);
+        if (id == null) throw new IllegalArgumentException("Invalid Page ID " + value);
+        return id;
+    }
+
+    public boolean allows(Identifier id) {
+        if (blocklist.contains(id)) return false;
+        String category = category(id);
+        return !restricts(category) || allowlist.contains(id);
+    }
+
+    public boolean restricts(String category) {
+        return allowlist.stream().anyMatch(entry -> category(entry).equals(category));
+    }
+
+    public <T> List<T> eligible(List<T> candidates, java.util.function.Function<T, Identifier> pageId) {
+        return candidates.stream().filter(candidate -> allows(pageId.apply(candidate))).toList();
+    }
+
+    public <T> List<T> required(List<T> candidates, java.util.function.Function<T, Identifier> pageId,
+                                T fallback) {
+        List<T> eligible = eligible(candidates, pageId);
+        return eligible.isEmpty() ? List.of(fallback) : eligible;
+    }
+
+    private static String category(Identifier id) {
+        String path = id.getPath();
+        if (path.startsWith("biome/") && java.util.Set.of("native", "single", "tiled", "grid",
+                "tiny", "small", "medium", "large", "huge").contains(path.substring("biome/".length())))
+            return "biome_distribution";
+        return path.substring(0, path.indexOf('/') < 0 ? path.length() : path.indexOf('/'));
+    }
+
+    public static Identifier page(String category, Enum<?> value) {
+        return Identifier.fromNamespaceAndPath("rivencraft", category + "/"
+                + value.name().toLowerCase(java.util.Locale.ROOT));
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortRandomStructureSelection.java

@@ -19,6 +19,11 @@ public final class PortRandomStructureSelection {
     }
 
     public static Selection select(MinecraftServer server, long seed, PortAgeTerrain terrain, PortBiomePlan plan) {
+        return select(server, seed, terrain, plan, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static Selection select(MinecraftServer server, long seed, PortAgeTerrain terrain, PortBiomePlan plan,
+                                   PortRandomPagePolicy policy) {
         Set<Identifier> biomes = actualBiomes(server, terrain, plan);
         var eligible = new ArrayList<PortRankedChoice.Option<Identifier>>();
         for (String name : List.of("dungeons", "mineshafts", "nether_fortresses", "strongholds", "villages",
@@ -32,7 +37,7 @@ public final class PortRandomStructureSelection {
                             .get(ResourceKey.create(Registries.PLACED_FEATURE,
                                     Identifier.fromNamespaceAndPath("rivencraft", "dungeons"))).isPresent()
                     : PortStructurePages.randomEligible(feature, terrain, biomes, server.registryAccess());
-            if (allowed) eligible.add(new PortRankedChoice.Option<>(feature, rank(name)));
+            if (allowed && policy.allows(feature)) eligible.add(new PortRankedChoice.Option<>(feature, rank(name)));
         }
         var random = new Random(seed ^ 0x5354525543545552L);
         int count = random.nextInt(3), dungeons = 0;
@@ -47,7 +52,7 @@ public final class PortRandomStructureSelection {
     }
 
     private static Set<Identifier> actualBiomes(MinecraftServer server, PortAgeTerrain terrain, PortBiomePlan plan) {
-        if (plan != null && plan.distribution() != PortBiomePlan.Distribution.NATIVE)
+        if (plan != null && !plan.biomes().isEmpty())
             return Set.copyOf(plan.biomes());
         if (terrain == PortAgeTerrain.FLAT) return Set.of(Identifier.withDefaultNamespace("plains"));
         if (terrain == PortAgeTerrain.VOID) return Set.of(Identifier.withDefaultNamespace("the_void"));

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortReturnLinks.java

@@ -0,0 +1,48 @@
+package net.dnorberg.rivencraft.age;
+
+import net.dnorberg.rivencraft.PortConfig;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.LinkBookTarget;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.util.Prediction;
+import net.minecraft.world.item.ItemStack;
+
+/** Called only after successful Descriptive Book travel and its Disarm effect. */
+public final class PortReturnLinks {
+    private PortReturnLinks() {}
+
+    public static void afterSuccessfulTravel(ServerPlayer player, Identifier age, LinkBookTarget departure) {
+        var mode = PortConfig.RETURN_LINK_MODE.get();
+        if (mode == PortConfig.ReturnLinkMode.DISABLED) return;
+        var storage = player.level().getServer().overworld().getDataStorage();
+        boolean issue = shouldIssue(mode, storage.computeIfAbsent(PortAgeVisits.TYPE), age);
+        if (!issue) return;
+        ItemStack book = createBook(departure);
+        var source = player.level().getServer().getLevel(net.minecraft.resources.ResourceKey.create(
+                net.minecraft.core.registries.Registries.DIMENSION, departure.dimension()));
+        if (source != null) book.set(Rivencraft.LINK_DESTINATION_NAME.get(),
+                net.dnorberg.rivencraft.item.LinkingBookItem.destinationName(source));
+        if (!player.getInventory().add(book)) player.drop(book, false, Prediction.SERVER_ONLY);
+        // Persist the once-per-Age marker before the next arrival can issue another.
+        if (mode == PortConfig.ReturnLinkMode.ON_CREATION)
+            storage.saveAndJoin();
+    }
+
+    static boolean shouldIssue(PortConfig.ReturnLinkMode mode, PortAgeVisits visits, Identifier age) {
+        return switch (mode) {
+            case DISABLED -> false;
+            case ALWAYS -> true;
+            case ON_CREATION -> visits.markFirstVisit(age);
+        };
+    }
+
+    static ItemStack createBook(LinkBookTarget departure) {
+        ItemStack book = new ItemStack(Rivencraft.LINKING_BOOK.get());
+        book.set(Rivencraft.LINK_BOOK_TARGET.get(), departure);
+        book.set(DataComponents.CUSTOM_NAME, Component.translatable("item.rivencraft.linking_book.return"));
+        return book;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortSeasonPolicies.java

@@ -0,0 +1,66 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.*;
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Frozen per-Age season choice, separate from the backend's legacy index codec. */
+public final class PortSeasonPolicies extends SavedData {
+    public enum Mode {
+        NO_SEASONS, SEASONS, ETERNAL_WINTER, ETERNAL_SUMMER, ETERNAL_FALL, ETERNAL_SPRING;
+        public boolean eternal() { return this != NO_SEASONS && this != SEASONS; }
+    }
+    public record Policy(Mode mode, boolean authored) {
+        static final Codec<Policy> CODEC = RecordCodecBuilder.create(i -> i.group(
+                Codec.STRING.xmap(Mode::valueOf, Mode::name).fieldOf("mode").forGetter(Policy::mode),
+                Codec.BOOL.fieldOf("authored").forGetter(Policy::authored)).apply(i, Policy::new));
+    }
+    private static final SavedDataType<PortSeasonPolicies> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "season_policies"), () -> new PortSeasonPolicies(Map.of()),
+            Codec.unboundedMap(Identifier.CODEC, Policy.CODEC).fieldOf("ages").codec()
+                    .xmap(PortSeasonPolicies::new, data -> Map.copyOf(data.policies)));
+    private final Map<Identifier, Policy> policies = new HashMap<>();
+    private PortSeasonPolicies(Map<Identifier, Policy> values) { policies.putAll(values); }
+    public static PortSeasonPolicies get(MinecraftServer server) { return server.overworld().getDataStorage().computeIfAbsent(TYPE); }
+    Policy snapshot(Identifier id) { return policies.get(id); }
+    void put(Identifier id, Policy policy) { if (policy == null) policies.remove(id); else policies.put(id, policy); setDirty(); }
+    public Policy forLevel(ServerLevel level) {
+        if (level instanceof PortAgeLevel age && age.caveTerrain()) return new Policy(Mode.NO_SEASONS, true);
+        // Existing Ages retain cycling behavior when integration is installed later.
+        return policies.getOrDefault(level.dimension().identifier(), new Policy(Mode.SEASONS, false));
+    }
+    public static Mode forPage(Identifier id) {
+        if (!id.getNamespace().equals("rivencraft") || !id.getPath().startsWith("season/")) return null;
+        try { return Mode.valueOf(id.getPath().substring(7).toUpperCase(Locale.ROOT)); }
+        catch (IllegalArgumentException e) { return null; }
+    }
+    static Policy select(List<Identifier> pages, long seed, PortAgeTerrain terrain, boolean installed) {
+        return select(pages, seed, terrain, installed, PortRandomPagePolicy.UNRESTRICTED);
+    }
+    static Policy select(List<Identifier> pages, long seed, PortAgeTerrain terrain, boolean installed, PortRandomPagePolicy policy) {
+        if (terrain == PortAgeTerrain.CAVE) return new Policy(Mode.NO_SEASONS, true);
+        Mode written = null;
+        for (var page : pages) if (forPage(page) != null) written = forPage(page);
+        if (written != null) {
+            if (!installed && written != Mode.NO_SEASONS) throw new IllegalArgumentException("Seasonal pages require Serene Seasons");
+            return new Policy(written, true);
+        }
+        if (!installed) return null;
+        // 1.21.1 LegacyRankChoice ranks: Seasons=1, None=2, each Eternal=3.
+        var modes = List.of(new PortRankedChoice.Option<>(Mode.SEASONS, 1),
+                new PortRankedChoice.Option<>(Mode.NO_SEASONS, 2),
+                new PortRankedChoice.Option<>(Mode.ETERNAL_WINTER, 3),
+                new PortRankedChoice.Option<>(Mode.ETERNAL_SUMMER, 3),
+                new PortRankedChoice.Option<>(Mode.ETERNAL_FALL, 3),
+                new PortRankedChoice.Option<>(Mode.ETERNAL_SPRING, 3));
+        Mode mode = PortRankedChoice.choose(new Random(seed ^ 0x5E450A5E5EED21L),
+                policy.required(modes, option -> PortRandomPagePolicy.page("season", option.value()),
+                        new PortRankedChoice.Option<>(Mode.NO_SEASONS, 2)));
+        return new Policy(mode, false);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortSkyStyle.java

@@ -26,9 +26,13 @@ public enum PortSkyStyle {
     }
 
     public static PortSkyStyle resolve(List<Identifier> pages, long seed) {
+        return resolve(pages, seed, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static PortSkyStyle resolve(List<Identifier> pages, long seed, PortRandomPagePolicy policy) {
         return pages.stream().map(PortSkyStyle::forPage).filter(java.util.Objects::nonNull)
                 .findFirst().orElseGet(() -> pages.stream().anyMatch(PortSkyStyle::isCelestial)
-                        ? OVERWORLD : random(seed));
+                        ? OVERWORLD : random(seed, policy));
     }
 
     /** Nether-style Ages use their fog clear color as the visible backdrop. */
@@ -50,11 +54,17 @@ public enum PortSkyStyle {
         };
     }
 
-    private static PortSkyStyle random(long seed) {
+    private static PortSkyStyle random(long seed, PortRandomPagePolicy policy) {
         // Match the first draw in 1.21.1 AgeSkyProfile.random: its equally
         // likely INHERITED and OVERWORLD slots currently share the native
         // Overworld presentation here. Do not add unported colors/bodies.
-        int choice = new Random(seed ^ 0x534B5950524F464CL).nextInt(5);
+        var styles = policy.required(java.util.stream.IntStream.range(0, 5).boxed()
+                        .filter(slot -> slot != 0 || !policy.restricts("sky")).toList(),
+                slot -> Identifier.fromNamespaceAndPath("rivencraft", "sky/" + switch (slot) {
+                    case 0 -> "inherited"; case 1 -> "overworld"; case 2 -> "nether";
+                    case 3 -> "end"; default -> "static";
+                }), 0);
+        int choice = styles.get(new Random(seed ^ 0x534B5950524F464CL).nextInt(styles.size()));
         return switch (choice) {
             case 0, 1 -> OVERWORLD;
             case 2 -> NETHER;

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortStatusEffectProviders.java

@@ -0,0 +1,233 @@
+package net.dnorberg.rivencraft.age;
+
+import java.lang.ref.WeakReference;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.Random;
+import java.util.WeakHashMap;
+import net.dnorberg.rivencraft.Rivencraft;
+
+import net.minecraft.core.Holder;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.effect.MobEffect;
+import net.minecraft.world.effect.MobEffectInstance;
+import net.minecraft.world.effect.MobEffects;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.LivingEntity;
+import net.minecraft.world.entity.monster.Monster;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.entity.EntityTypeTest;
+import net.minecraft.world.phys.AABB;
+import net.neoforged.neoforge.event.entity.EntityTravelToDimensionEvent;
+import net.neoforged.neoforge.event.entity.player.PlayerEvent;
+import net.neoforged.neoforge.event.server.ServerStoppingEvent;
+import net.neoforged.neoforge.event.tick.ServerTickEvent;
+
+/** Legacy potion cards adapted to bounded, Age-local server effects. */
+@net.neoforged.fml.common.EventBusSubscriber(modid = Rivencraft.MOD_ID)
+public final class PortStatusEffectProviders {
+    private static final int MAX_TRACKED_AGES = 64;
+    private static final Map<Identifier, Spec> SPECS = createSpecs();
+    private static final Map<ServerLevel, List<Lease>> LEASES = new WeakHashMap<>();
+
+    private PortStatusEffectProviders() {}
+
+    public static void register() {
+        SPECS.keySet().forEach(id -> PortInstabilityRuntime.register(id, PortStatusEffectProviders::apply));
+    }
+
+    static void apply(PortInstabilityRuntime.Context context, Identifier id, int level) {
+        if (!PortInstabilityConfig.statusEffectsEnabled()
+                || !PortInstabilityRuntime.isAge(context.level())) return;
+        Spec spec = SPECS.get(id);
+        if (spec == null || spec.target() == Target.HOSTILE && !PortInstabilityConfig.statusEffectsHostiles()
+                || spec.target() == Target.GENERAL && !PortInstabilityConfig.statusEffectsPlayers()
+                && !PortInstabilityConfig.statusEffectsNonplayers()) return;
+        List<Lease> leases = LEASES.get(context.level());
+        if (leases == null) {
+            if (LEASES.size() >= MAX_TRACKED_AGES) return;
+            leases = new ArrayList<>();
+            LEASES.put(context.level(), leases);
+        }
+        prune(context.level(), leases, context.serverTick(), false);
+        if (leases.size() >= PortInstabilityConfig.statusEffectsMaxActive()) return;
+
+        Random random = new Random(context.age().seed() ^ (context.serverTick() * 0x9E3779B97F4A7C15L)
+                ^ id.hashCode());
+        ChunkPos chunk = context.loadedChunks().get(random.nextInt(context.loadedChunks().size()));
+        AABB bounds = new AABB(chunk.getMinBlockX(), context.level().getMinY(), chunk.getMinBlockZ(),
+                chunk.getMaxBlockX() + 1, context.level().getMaxY(), chunk.getMaxBlockZ() + 1);
+        int duration = Math.min(spec.legacyDuration(), PortInstabilityConfig.statusEffectsMaxDuration());
+        int amplifier = Math.max(0, level - 1);
+        MobEffectInstance instance = new MobEffectInstance(spec.effect(), duration, amplifier);
+        List<LivingEntity> candidates = new ArrayList<>();
+        context.level().getEntities(EntityTypeTest.forClass(LivingEntity.class), bounds,
+                entity -> eligible(context.level(), entity, spec, instance), candidates,
+                PortInstabilityConfig.statusEffectsMaxCandidates());
+        if (candidates.isEmpty()) return;
+        candidates.sort(Comparator.comparing(Entity::getUUID));
+        LivingEntity target = candidates.get(random.nextInt(candidates.size()));
+        if (!context.budget().claim() || !target.addEffect(instance)) return;
+        context.budget().recordApplied();
+        leases.add(new Lease(id, new WeakReference<>(target), instance,
+                context.serverTick() + duration, spec.target()));
+    }
+
+    private static boolean eligible(ServerLevel level, LivingEntity entity, Spec spec,
+                                    MobEffectInstance instance) {
+        if (!entity.isAlive() || entity.isRemoved() || entity.level() != level
+                || entity.getEffect(spec.effect()) != null || !entity.canBeAffected(instance)
+                || !spec.global() && !level.canSeeSky(entity.blockPosition())) return false;
+        return allowedByPolicy(spec.target(), entity);
+    }
+
+    private static boolean allowedByPolicy(Target target, LivingEntity entity) {
+        if (entity instanceof Player player) {
+            return target == Target.GENERAL && PortInstabilityConfig.statusEffectsPlayers()
+                    && !player.isCreative() && !player.isSpectator();
+        }
+        return target == Target.GENERAL ? PortInstabilityConfig.statusEffectsNonplayers()
+                : entity instanceof Monster && PortInstabilityConfig.statusEffectsHostiles();
+    }
+
+    @net.neoforged.bus.api.SubscribeEvent
+    public static void onServerTickPost(ServerTickEvent.Post event) {
+        if (event.getServer().getTickCount() % 20 != 0) return;
+        boolean disabled = !PortInstabilityConfig.instabilityEnabled() || !PortInstabilityConfig.statusEffectsEnabled();
+        long tick = event.getServer().getTickCount();
+        for (var entry : LEASES.entrySet()) {
+            prune(entry.getKey(), entry.getValue(), tick, disabled
+                    || !PortInstabilityData.get(entry.getKey().getServer()).age(entry.getKey()).enabled());
+        }
+        LEASES.values().removeIf(List::isEmpty);
+    }
+
+    @net.neoforged.bus.api.SubscribeEvent
+    public static void onEntityTravel(EntityTravelToDimensionEvent event) {
+        Entity entity = event.getEntity();
+        if (entity instanceof LivingEntity living && !entity.level().dimension().equals(event.getDimension())) {
+            clearEntity(living);
+        }
+    }
+
+    @net.neoforged.bus.api.SubscribeEvent
+    public static void onPlayerChangedDimension(PlayerEvent.PlayerChangedDimensionEvent event) {
+        if (event.getEntity() instanceof ServerPlayer player) clearEntity(player);
+    }
+
+    @net.neoforged.bus.api.SubscribeEvent
+    public static void onPlayerLoggedOut(PlayerEvent.PlayerLoggedOutEvent event) {
+        if (event.getEntity() instanceof ServerPlayer player) clearEntity(player);
+    }
+
+    @net.neoforged.bus.api.SubscribeEvent
+    public static void onServerStopping(ServerStoppingEvent event) {
+        long tick = event.getServer().getTickCount();
+        for (var entry : LEASES.entrySet()) prune(entry.getKey(), entry.getValue(), tick, true);
+        LEASES.clear();
+    }
+
+    public static void clearAge(ServerLevel level) {
+        var leases = LEASES.remove(level);
+        if (leases != null) prune(level, leases, level.getServer().getTickCount(), true);
+    }
+
+    private static void clearEntity(LivingEntity entity) {
+        for (List<Lease> leases : LEASES.values()) {
+            Iterator<Lease> iterator = leases.iterator();
+            while (iterator.hasNext()) {
+                Lease lease = iterator.next();
+                if (lease.entity().get() != entity) continue;
+                removeOwnedEffect(entity, lease);
+                iterator.remove();
+            }
+        }
+    }
+
+    private static void prune(ServerLevel level, List<Lease> leases, long tick, boolean removeAll) {
+        Iterator<Lease> iterator = leases.iterator();
+        while (iterator.hasNext()) {
+            Lease lease = iterator.next();
+            LivingEntity entity = lease.entity().get();
+            if (entity == null || entity.isRemoved() || entity.getEffect(lease.instance().getEffect()) == null) {
+                iterator.remove();
+                continue;
+            }
+            boolean revoke = removeAll || !PortInstabilityConfig.instabilityProviderEnabled(lease.provider())
+                    || entity.level() != level
+                    || !allowedByPolicy(lease.target(), entity);
+            if (revoke || tick >= lease.expiresAt()) {
+                removeOwnedEffect(entity, lease);
+                iterator.remove();
+            }
+        }
+    }
+
+    private static void removeOwnedEffect(LivingEntity entity, Lease lease) {
+        // addEffect stores the supplied instance when no effect exists. Do not remove
+        // a replacement from another mod (or a stronger/extended effect).
+        if (entity.getEffect(lease.instance().getEffect()) == lease.instance()
+                && lease.instance().getAmplifier() == lease.amplifier()
+                && lease.instance().getDuration() <= lease.originalDuration()) {
+            entity.removeEffect(lease.instance().getEffect());
+        }
+    }
+
+    static int legacyDuration(Identifier id) {
+        Spec spec = SPECS.get(id);
+        return spec == null ? -1 : spec.legacyDuration();
+    }
+
+    static boolean localRequiresSky(Identifier id) {
+        Spec spec = SPECS.get(id);
+        return spec != null && !spec.global();
+    }
+
+    static boolean eligibleTarget(ServerLevel level, LivingEntity entity, Identifier id) {
+        Spec spec = SPECS.get(id);
+        return spec != null && eligible(level, entity, spec,
+                new MobEffectInstance(spec.effect(), spec.legacyDuration(), 0));
+    }
+
+    private static Map<Identifier, Spec> createSpecs() {
+        Map<Identifier, Spec> specs = new HashMap<>();
+        addPair(specs, "blindness", MobEffects.BLINDNESS, 60);
+        addPair(specs, "fatigue", MobEffects.MINING_FATIGUE, 80);
+        addPair(specs, "hunger", MobEffects.HUNGER, 80);
+        addPair(specs, "nausea", MobEffects.NAUSEA, 60);
+        addPair(specs, "poison", MobEffects.POISON, 80);
+        addPair(specs, "slow", MobEffects.SLOWNESS, 80);
+        addPair(specs, "weakness", MobEffects.WEAKNESS, 80);
+        addPair(specs, "wither", MobEffects.WITHER, 30);
+        specs.put(id("enemyregen_global"), new Spec(MobEffects.REGENERATION, 200, true, Target.HOSTILE));
+        specs.put(id("enemyresist_global"), new Spec(MobEffects.RESISTANCE, 200, true, Target.HOSTILE));
+        return Map.copyOf(specs);
+    }
+
+    private static void addPair(Map<Identifier, Spec> specs, String name,
+                                Holder<MobEffect> effect, int duration) {
+        specs.put(id(name), new Spec(effect, duration, false, Target.GENERAL));
+        specs.put(id(name + "_global"), new Spec(effect, duration, true, Target.GENERAL));
+    }
+
+    private static Identifier id(String path) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path);
+    }
+
+    private enum Target { GENERAL, HOSTILE }
+    private record Spec(Holder<MobEffect> effect, int legacyDuration, boolean global, Target target) {}
+    private record Lease(Identifier provider, WeakReference<LivingEntity> entity, MobEffectInstance instance, long expiresAt,
+                         Target target, int amplifier, int originalDuration) {
+        private Lease(Identifier provider, WeakReference<LivingEntity> entity, MobEffectInstance instance, long expiresAt,
+                      Target target) {
+            this(provider, entity, instance, expiresAt, target, instance.getAmplifier(), instance.getDuration());
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortStructurePages.java

@@ -95,11 +95,22 @@ public final class PortStructurePages {
         var set = registries.lookupOrThrow(Registries.STRUCTURE_SET)
                 .get(ResourceKey.create(Registries.STRUCTURE_SET, SETS.get(page)));
         if (set.isEmpty()) return false;
-        var compatible = set.get().value().structures().stream()
+        var compatible = compatibleBiomes(set.get().value());
+        return compatible.isEmpty() || biomes.stream().anyMatch(compatible::contains);
+    }
+
+    public static Set<Identifier> compatibleBiomes(Identifier page, HolderLookup.Provider registries) {
+        if (!supports(page)) return Set.of();
+        return registries.lookupOrThrow(Registries.STRUCTURE_SET)
+                .get(ResourceKey.create(Registries.STRUCTURE_SET, SETS.get(page)))
+                .map(holder -> compatibleBiomes(holder.value())).orElse(Set.of());
+    }
+
+    private static Set<Identifier> compatibleBiomes(StructureSet set) {
+        return set.structures().stream()
                 .flatMap(entry -> entry.structure().value().biomes().stream())
                 .flatMap(holder -> holder.unwrapKey().stream()).map(key -> key.identifier())
-                .collect(java.util.stream.Collectors.toSet());
-        return compatible.isEmpty() || biomes.stream().anyMatch(compatible::contains);
+                .collect(java.util.stream.Collectors.toUnmodifiableSet());
     }
 
     private static Map<Identifier, Integer> enabled(List<Identifier> pages) {

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortTerrainFeaturePlan.java

@@ -10,7 +10,7 @@ import net.minecraft.resources.Identifier;
 /** Frozen terrain filters and ordered solid/surface features for an Age. */
 public record PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int denseOres,
                                      boolean starFissures, List<Identifier> structures, List<Identifier> carvers,
-                                     boolean structureControl) {
+                                     boolean structureControl, List<Identifier> ruins) {
     public static final Identifier FLOATING_ISLANDS = Identifier.fromNamespaceAndPath(
             Rivencraft.MOD_ID, "feature/floating_islands");
     public static final Identifier TENDRILS = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/tendrils");
@@ -32,7 +32,8 @@ public record PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int
             Codec.BOOL.optionalFieldOf("star_fissures", false).forGetter(PortTerrainFeaturePlan::starFissures),
             Identifier.CODEC.listOf().optionalFieldOf("structures", List.of()).forGetter(PortTerrainFeaturePlan::structures),
             Identifier.CODEC.listOf().optionalFieldOf("carvers", List.of()).forGetter(PortTerrainFeaturePlan::carvers),
-            Codec.BOOL.optionalFieldOf("structure_control", false).forGetter(PortTerrainFeaturePlan::structureControl)
+            Codec.BOOL.optionalFieldOf("structure_control", false).forGetter(PortTerrainFeaturePlan::structureControl),
+            Identifier.CODEC.listOf().optionalFieldOf("ruins", List.of()).forGetter(PortTerrainFeaturePlan::ruins)
     ).apply(instance, PortTerrainFeaturePlan::new));
 
     public record Choice(Identifier page, Identifier material) {
@@ -50,6 +51,9 @@ public record PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int
     }
 
     public PortTerrainFeaturePlan {
+        ruins = List.copyOf(ruins);
+        if (ruins.size() > 252 || ruins.stream().anyMatch(id -> !net.dnorberg.rivencraft.compat.RuinsTemplatePages.isSymbol(id)))
+            throw new IllegalArgumentException("Invalid Ruins template pages");
         choices = List.copyOf(choices);
         structures = List.copyOf(structures);
         carvers = List.copyOf(carvers);
@@ -57,7 +61,7 @@ public record PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int
         PortCarverPages.validateCounts(carvers);
         if (denseOres < 0 || denseOres > MAX_PER_FEATURE)
             throw new IllegalArgumentException("Dense Ores permits at most 32 occurrences");
-        if (choices.isEmpty() && !skylands && denseOres == 0 && !starFissures && structures.isEmpty() && carvers.isEmpty() && !structureControl)
+        if (choices.isEmpty() && !skylands && denseOres == 0 && !starFissures && structures.isEmpty() && carvers.isEmpty() && !structureControl && ruins.isEmpty())
             throw new IllegalArgumentException("Terrain feature plan must not be empty");
         var counts = new HashMap<Identifier, Integer>();
         for (Choice choice : choices) {
@@ -66,6 +70,12 @@ public record PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int
         }
     }
 
+    public PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int denseOres,
+                                 boolean starFissures, List<Identifier> structures, List<Identifier> carvers,
+                                 boolean structureControl) {
+        this(choices, skylands, denseOres, starFissures, structures, carvers, structureControl, List.of());
+    }
+
     public PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int denseOres,
                                  boolean starFissures, List<Identifier> structures, List<Identifier> carvers) {
         this(choices, skylands, denseOres, starFissures, structures, carvers, false);

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/PortWritingDeskProbe.java

@@ -0,0 +1,100 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.WritingDeskBlock;
+import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.menu.WritingDeskMenu;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.inventory.ContainerInput;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+
+/** Disposable server fixture for copying transactions, page moves and two-part removal. */
+final class PortWritingDeskProbe {
+    private static final BlockPos POS = new BlockPos(0, 64, 0);
+    private PortWritingDeskProbe() {}
+    private static ItemStack page(String path) { return PageItem.createSymbolPage(Identifier.fromNamespaceAndPath("rivencraft", path)); }
+
+    static void create(ServerLevel level) {
+        PortAgeTravel.findLanding(level);
+        var player = new PortProgressionPlayer(level,
+                new com.mojang.authlib.GameProfile(java.util.UUID.fromString("f92ad9ee-1ff0-4fe2-bcd3-994d4c035933"), "RivenDeskProbe"));
+        player.setPos(0.5, 64, 2.5);
+        // New Minecraft drops Container block-entity contents during removal.
+        // Removing either half must remove its partner and drop contents once.
+        for (Direction facing : Direction.Plane.HORIZONTAL) for (boolean extension : List.of(false, true)) {
+            var state = Rivencraft.WRITING_DESK.get().defaultBlockState().setValue(WritingDeskBlock.FACING, facing);
+            level.setBlock(POS, state, 3);
+            Rivencraft.WRITING_DESK.get().setPlacedBy(level, POS, state, player, new ItemStack(Rivencraft.WRITING_DESK_ITEM.get()));
+            BlockPos other = POS.relative(facing.getClockWise());
+            if (!level.getBlockState(other).getValue(WritingDeskBlock.EXTENSION))
+                throw new IllegalStateException("Desk extension not placed");
+            var desk = (WritingDeskBlockEntity) level.getBlockEntity(POS);
+            desk.setItem(WritingDeskBlockEntity.PAPER, new ItemStack(Items.PAPER, 3));
+            level.destroyBlock(extension ? other : POS, true);
+            if (level.getBlockState(POS).is(Rivencraft.WRITING_DESK.get()) || level.getBlockState(other).is(Rivencraft.WRITING_DESK.get()))
+                throw new IllegalStateException("Desk partner survived removal");
+            var drops = level.getEntitiesOfClass(net.minecraft.world.entity.item.ItemEntity.class,
+                    new net.minecraft.world.phys.AABB(-3, 60, -3, 4, 69, 4));
+            int paper = drops.stream().filter(e -> e.getItem().is(Items.PAPER)).mapToInt(e -> e.getItem().getCount()).sum();
+            int desks = drops.stream().filter(e -> e.getItem().is(Rivencraft.WRITING_DESK_ITEM.get())).mapToInt(e -> e.getItem().getCount()).sum();
+            if (paper != 3 || desks != 1) throw new IllegalStateException("Desk removal duplicated/lost drops: " + paper + "/" + desks);
+            drops.forEach(net.minecraft.world.entity.Entity::discard);
+        }
+        var state = Rivencraft.WRITING_DESK.get().defaultBlockState();
+        level.setBlock(POS, state, 3);
+        Rivencraft.WRITING_DESK.get().setPlacedBy(level, POS, state, player, new ItemStack(Rivencraft.WRITING_DESK_ITEM.get()));
+        var desk = (WritingDeskBlockEntity) level.getBlockEntity(POS);
+        try {
+            if (desk.canPlaceItem(0, PageItem.createLinkPanelPage())) throw new IllegalStateException("Desk accepted Link Panel");
+            desk.setItem(0, page("terrain/flat"));
+            var folder = new ItemStack(Rivencraft.COLLATION_FOLDER.get());
+            folder.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(List.of(page("weather/off"))));
+            desk.setItem(1, folder);
+            desk.setItem(WritingDeskBlockEntity.PAPER, new ItemStack(Items.PAPER, 2));
+            desk.setItem(WritingDeskBlockEntity.INK, new ItemStack(Rivencraft.INK_VIAL.get()));
+            if (desk.inkRemaining() != 16 || !desk.getItem(WritingDeskBlockEntity.RETURN).is(Items.GLASS_BOTTLE))
+                throw new IllegalStateException("Desk ink exchange regression");
+            var menu = new WritingDeskMenu(1, player.getInventory(), desk);
+            menu.broadcastChanges();
+            if (menu.getSlot(WritingDeskMenu.COPY_RESULT).getItem().isEmpty() || desk.inkRemaining() != 16)
+                throw new IllegalStateException("Desk virtual result consumed inputs");
+            menu.clicked(WritingDeskMenu.COPY_RESULT, 0, ContainerInput.PICKUP, player);
+            if (menu.getCarried().isEmpty() || desk.inkRemaining() != 15
+                    || desk.getItem(WritingDeskBlockEntity.PAPER).getCount() != 1 || desk.getItem(0).isEmpty())
+                throw new IllegalStateException("Desk copy did not consume exactly one paper/ink");
+            if (!PortProgressionProbe.isComplete(player, "copy_page"))
+                throw new IllegalStateException("Missing copy_page award");
+            menu.setCarried(ItemStack.EMPTY);
+            for (int slot = 0; slot < player.getInventory().getContainerSize(); slot++)
+                player.getInventory().setItem(slot, new ItemStack(Items.COBBLESTONE, 64));
+            if (!menu.quickMoveStack(player, WritingDeskMenu.COPY_RESULT).isEmpty() || desk.inkRemaining() != 15)
+                throw new IllegalStateException("Full inventory consumed copy inputs");
+            player.getInventory().clearContent();
+            if (!menu.clickMenuButton(player, WritingDeskMenu.movePageButtonId(1, 0, 1, 26)))
+                throw new IllegalStateException("Desk sparse page movement failed");
+            if (!menu.clickMenuButton(player, WritingDeskMenu.extractPageButtonId(1, 26, -1)) || menu.getCarried().isEmpty())
+                throw new IllegalStateException("Desk page extraction failed");
+            menu.setCarried(ItemStack.EMPTY);
+            for (int i = 0; i < 21; i++) menu.clickMenuButton(player, WritingDeskMenu.NEXT_TABS);
+            if (menu.firstVisibleTab() != 84 || !menu.clickMenuButton(player, 87)) throw new IllegalStateException("88 desk tabs not reachable");
+            desk.setItem(87, page("lighting/bright"));
+            menu.clickMenuButton(player, WritingDeskMenu.PAGE_BUTTON_BASE);
+            menu.broadcastChanges();
+        } finally { player.getInventory().clearContent(); }
+        verify(level);
+    }
+
+    static void verify(ServerLevel level) {
+        if (!(level.getBlockEntity(POS) instanceof WritingDeskBlockEntity desk)
+                || desk.activeCollection() != 87 || desk.inkRemaining() != 15
+                || desk.getItem(WritingDeskBlockEntity.PAPER).getCount() != 1 || desk.getItem(87).isEmpty()
+                || desk.displayPage().isEmpty()) throw new IllegalStateException("Desk persistence regression");
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/age/RuntimeAgeBackend.java

@@ -149,22 +149,130 @@ public final class RuntimeAgeBackend {
                                      PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
                                      PortTerrainFeaturePlan terrainFeatures, PortWeatherMode weather,
                                      PortLighting lighting, PortSkyStyle sky, PortAgeColors colors, PortDayCycle dayCycle) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
+                terrainFeatures, weather, lighting, sky, colors, dayCycle, List.of());
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures, PortWeatherMode weather,
+                                     PortLighting lighting, PortSkyStyle sky, PortAgeColors colors, PortDayCycle dayCycle,
+                                     List<Identifier> librarySymbols) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, terrainFeatures,
+                weather, lighting, sky, colors, dayCycle, librarySymbols, null);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures, PortWeatherMode weather,
+                                     PortLighting lighting, PortSkyStyle sky, PortAgeColors colors, PortDayCycle dayCycle,
+                                     List<Identifier> librarySymbols, String displayName) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, terrainFeatures,
+                weather, lighting, sky, colors, dayCycle, librarySymbols, displayName, PortRandomPagePolicy.UNRESTRICTED);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures, PortWeatherMode weather,
+                                     PortLighting lighting, PortSkyStyle sky, PortAgeColors colors, PortDayCycle dayCycle,
+                                     List<Identifier> librarySymbols, String displayName, PortRandomPagePolicy policy) {
         checkServerThread(server);
-        ageName(id);
+        String name = ageName(id);
         AgeLevelIndex index = index(server);
-        if (index.contains(id)) throw new IllegalArgumentException("Age already exists: " + id);
-        ServerLevel level = load(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
-                terrainFeatures, lighting, sky, colors, dayCycle);
-        ((PortAgeLevel) level).configureWeather(weather);
-        index.add(id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, terrainFeatures, lighting, sky, colors, dayCycle);
-        // A newly bound book may be used immediately. Persist its Age identity
-        // before publishing the catalog so a later crash cannot leave that
-        // book pointing at a world omitted from the on-disk index.
-        server.overworld().getDataStorage().saveAndJoin();
+        if (index.contains(id) || server.getLevel(dimensionKey(id)) != null)
+            throw new IllegalArgumentException("Age already exists: " + id);
+        Path directory = archivePaths(server, name).live();
+        if (Files.exists(directory, LinkOption.NOFOLLOW_LINKS))
+            throw new IllegalArgumentException("Age storage already exists: " + id);
+        PortLibraryWriting writing = PortLibraryWriting.get(server);
+        List<Identifier> priorWriting = writing.symbols(id);
+        PortInstabilityData instability = PortInstabilityData.get(server);
+        PortInstabilityData.Age priorInstability = instability.snapshot(id);
+        PortSeasonPolicies seasons = PortSeasonPolicies.get(server);
+        PortSeasonPolicies.Policy priorSeason = seasons.snapshot(id);
+        ServerLevel level = null;
+        try {
+            seasons.put(id, PortSeasonPolicies.select(librarySymbols, seed, terrain,
+                    net.dnorberg.rivencraft.compat.SereneSeasonsCompatibility.available(), policy));
+            writing.put(id, librarySymbols);
+            level = load(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
+                    terrainFeatures, lighting, sky, colors, dayCycle);
+            ((PortAgeLevel) level).configureWeather(weather);
+            int accelerated = PortAcceleratedTicks.pageCount(librarySymbols);
+            if (accelerated > 0) PortAcceleratedTicks.configure(level, accelerated);
+            index.add(id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, terrainFeatures, lighting, sky, colors, dayCycle);
+            instability.create(level, librarySymbols, terrain, lighting, dayCycle);
+            if (displayName != null) index.setDisplayName(id, displayName);
+            // Commit all initial metadata before announcing an enterable Age.
+            level.getDataStorage().saveAndJoin();
+            server.overworld().getDataStorage().saveAndJoin();
+        } catch (RuntimeException failure) {
+            boolean closed = !(failure instanceof FailedAgeCleanupException);
+            if (level != null) {
+                try { closeFailedCreation(server, level); }
+                catch (RuntimeException cleanup) { closed = false; failure.addSuppressed(cleanup); }
+            }
+            index.discardCreation(id);
+            writing.put(id, priorWriting);
+            instability.restore(id, priorInstability);
+            seasons.put(id, priorSeason);
+            try { server.overworld().getDataStorage().saveAndJoin(); }
+            catch (RuntimeException cleanup) { failure.addSuppressed(cleanup); }
+            // Only the exact, previously absent directory belongs to this attempt.
+            // If closing failed, leave its files in place rather than race a writer.
+            if (closed) {
+                try { removeFailedCreationDirectory(server, name, directory); }
+                catch (IOException | RuntimeException cleanup) { failure.addSuppressed(cleanup); }
+            }
+            throw failure;
+        }
+        net.dnorberg.rivencraft.compat.SereneSeasonsCompatibility.apply(level);
         AgeCatalogSync.onCatalogChanged(server);
         return level;
     }
 
+    private static final class FailedAgeCleanupException extends IllegalStateException {
+        FailedAgeCleanupException(RuntimeException cause) { super("Failed Age stores could not close; files retained", cause); }
+    }
+
+    private static void closeFailedCreation(MinecraftServer server, ServerLevel level) {
+        if (!level.players().isEmpty()) throw new IllegalStateException("Failed Age contains players: " + level.dimension().identifier());
+        RuntimeException error = null;
+        try { level.getChunkSource().deactivateTicketsOnClosing(); }
+        catch (RuntimeException failure) { error = failure; }
+        try { level.close(); }
+        catch (IOException | RuntimeException failure) {
+            if (error == null) error = new IllegalStateException("Could not close failed Age", failure);
+            else error.addSuppressed(failure);
+        } finally {
+            server.levels.remove(level.dimension(), level);
+            try { NeoForge.EVENT_BUS.post(new LevelEvent.Unload(level)); }
+            catch (RuntimeException failure) {
+                if (error == null) error = failure; else error.addSuppressed(failure);
+            }
+        }
+        if (error != null) throw error;
+    }
+
+    private static void removeFailedCreationDirectory(MinecraftServer server, String name, Path directory) throws IOException {
+        if (!archivePaths(server, name).live().equals(directory)) throw new IOException("Age directory changed during rollback");
+        if (!Files.exists(directory, LinkOption.NOFOLLOW_LINKS)) return;
+        Files.walkFileTree(directory, new java.nio.file.SimpleFileVisitor<Path>() {
+            @Override public java.nio.file.FileVisitResult visitFile(Path file, java.nio.file.attribute.BasicFileAttributes attributes) throws IOException {
+                Files.delete(file);
+                return java.nio.file.FileVisitResult.CONTINUE;
+            }
+            @Override public java.nio.file.FileVisitResult postVisitDirectory(Path dir, IOException error) throws IOException {
+                if (error != null) throw error;
+                Files.delete(dir);
+                return java.nio.file.FileVisitResult.CONTINUE;
+            }
+        });
+    }
+
     /** Unloads an Age only when no player remains; save(true) flushes other entities. */
     public static void unload(MinecraftServer server, Identifier id) {
         checkServerThread(server);
@@ -266,10 +374,23 @@ public final class RuntimeAgeBackend {
             }
             throw new IllegalStateException("Could not archive Age " + id, exception);
         }
+        net.dnorberg.rivencraft.compat.SereneSeasonsCompatibility.retired(server, id);
         AgeCatalogSync.onCatalogChanged(server);
         Rivencraft.LOGGER.info("Retired 26.3 prototype Age {} (archived at {})", id, paths.archive());
     }
 
+    /** Display metadata never changes the dimension identity, seed or filesystem path. */
+    public static java.util.Optional<String> savedAgeName(MinecraftServer server, Identifier id) {
+        checkServerThread(server);
+        return java.util.Optional.ofNullable(index(server).displayName(id));
+    }
+
+    public static void setAgeDisplayName(MinecraftServer server, Identifier id, String name) {
+        checkServerThread(server);
+        index(server).setDisplayName(id, name);
+        server.overworld().getDataStorage().saveAndJoin();
+    }
+
     public static Map<Identifier, Long> savedAges(MinecraftServer server) {
         checkServerThread(server);
         return index(server).entries();
@@ -285,6 +406,23 @@ public final class RuntimeAgeBackend {
         return index(server).dayCycles();
     }
 
+    /** Snapshot only loaded Age settings; viewing a book never loads its destination. */
+    public static Map<Identifier, PortAgeDescription> loadedDescriptions(MinecraftServer server) {
+        checkServerThread(server);
+        AgeLevelIndex index = index(server);
+        var descriptions = new java.util.HashMap<Identifier, PortAgeDescription>();
+        var knownAges = index.entries().keySet();
+        for (var level : server.getAllLevels()) {
+            Identifier id = level.dimension().identifier();
+            if (!(level instanceof PortAgeLevel age) || !knownAges.contains(id)) continue;
+            PortBiomePlan biomes = index.biomePlan(id);
+            descriptions.put(id, new PortAgeDescription(index.terrain(id),
+                    biomes == null ? PortBiomePlan.Distribution.NATIVE : biomes.distribution(),
+                    index.lighting(id), age.weatherMode()));
+        }
+        return Map.copyOf(descriptions);
+    }
+
     /** Includes retired IDs, which must never be silently reused by a new book. */
     public static boolean isNameTaken(MinecraftServer server, Identifier id) {
         checkServerThread(server);
@@ -366,15 +504,14 @@ public final class RuntimeAgeBackend {
     }
 
     private static BiomeSource authoredBiomeSource(MinecraftServer server, PortBiomePlan plan, long seed) {
-        if (plan.distribution() == PortBiomePlan.Distribution.NATIVE)
-            throw new IllegalArgumentException("Native biome distribution has no authored source");
         var registry = server.registryAccess().lookupOrThrow(Registries.BIOME);
         List<Holder<Biome>> biomes = plan.biomes().stream().map(id ->
                 (Holder<Biome>) registry.get(ResourceKey.create(Registries.BIOME, id))
                         .orElseThrow(() -> new IllegalArgumentException("Unknown authored biome: " + id)))
                 .toList();
         return switch (plan.distribution()) {
-            case NATIVE -> throw new IllegalStateException("Native is not an override");
+            case NATIVE -> biomes.size() == 1 ? new FixedBiomeSource(biomes.getFirst())
+                    : new PortScaledBiomeSource(HolderSet.direct(biomes), seed, 0);
             case SINGLE -> new FixedBiomeSource(biomes.getFirst());
             case TILED, GRID -> new CheckerboardColumnBiomeSource(HolderSet.direct(biomes),
                     plan.distribution() == PortBiomePlan.Distribution.GRID ? 0 : 4);
@@ -397,11 +534,15 @@ public final class RuntimeAgeBackend {
                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
                                     PortTerrainFeaturePlan terrainFeatures, PortLighting lighting, PortSkyStyle sky,
                                     PortAgeColors colors, PortDayCycle dayCycle) {
+        net.dnorberg.rivencraft.compat.TerraBlenderBiomes.nether(server.registryAccess());
         ResourceKey<Level> key = ResourceKey.create(Registries.DIMENSION, id);
         if (server.getLevel(key) != null) throw new IllegalArgumentException("Level already loaded: " + id);
+        if (biomePlan != null && biomePlan.distribution() == PortBiomePlan.Distribution.NATIVE
+                && !biomePlan.biomes().isEmpty() && terrain != PortAgeTerrain.CAVE)
+            throw new IllegalArgumentException("Only Native Cave terrain may carry an explicit native biome pool");
 
         // Noise terrains reuse the Overworld biome source unless a
-        // non-Native authored distribution replaces it.
+        // non-Native authored distribution or a frozen Native Cave pool replaces it.
         // LevelStem.seedOverride controls chunk random state and getSeed().
         LevelStem overworldStem = server.registryAccess().lookupOrThrow(Registries.LEVEL_STEM)
                 .getValue(LevelStem.OVERWORLD);
@@ -453,7 +594,8 @@ public final class RuntimeAgeBackend {
                         throw new IllegalArgumentException("Cave terrain requires a Cave or Nether biome: " + biomeId);
                 }
             }
-            if (biomePlan != null && biomePlan.distribution() != PortBiomePlan.Distribution.NATIVE) {
+            if (biomePlan != null && (biomePlan.distribution() != PortBiomePlan.Distribution.NATIVE
+                    || terrain == PortAgeTerrain.CAVE && !biomePlan.biomes().isEmpty())) {
                 source = authoredBiomeSource(server, biomePlan, seed);
             }
             var settings = switch (terrain) {
@@ -467,8 +609,8 @@ public final class RuntimeAgeBackend {
             };
             generator = new NoiseBasedChunkGenerator(source, PortBiomeMaterialRules.apply(server.registryAccess(), settings.value()));
         }
-        if (rocks != null || vegetation != null || dungeons > 0 || lakes != null || terrainFeatures != null)
-            generator = new PortFeatureChunkGenerator(generator, rocks, vegetation, dungeons, lakes, terrainFeatures, seed);
+        generator = new PortFeatureChunkGenerator(generator, rocks, vegetation, dungeons, lakes, terrainFeatures, seed,
+                terrain != PortAgeTerrain.CAVE, PortLibraryWriting.get(server).symbols(id));
         LevelStem stem = new LevelStem(lighting.dimensionType(server, terrain, overworldStem.type(), sky),
                 generator, OptionalLong.of(seed));
         long biomeZoomSeed = BiomeManager.obfuscateSeed(server.getWorldGenSettings().options().seed());
@@ -479,6 +621,7 @@ public final class RuntimeAgeBackend {
         // Publish only after the constructor succeeds. If the load event fails,
         // roll back the map and close the newly opened chunk/entity stores.
         try {
+            net.dnorberg.rivencraft.compat.RuinsCompatibility.registerAge(id, terrainFeatures);
             server.levels.put(key, level);
             level.getWorldBorder().setAbsoluteMaxSize(server.getAbsoluteMaxWorldSize());
             server.getPlayerList().addWorldborderListener(level);
@@ -491,11 +634,10 @@ public final class RuntimeAgeBackend {
             Rivencraft.LOGGER.info("Loaded 26.3 prototype Age {} with seed {}", id, seed);
             return level;
         } catch (RuntimeException exception) {
-            server.levels.remove(key);
-            try {
-                level.close();
-            } catch (IOException closeException) {
-                exception.addSuppressed(closeException);
+            try { closeFailedCreation(server, level); }
+            catch (RuntimeException cleanup) {
+                exception.addSuppressed(cleanup);
+                throw new FailedAgeCleanupException(exception);
             }
             throw exception;
         }

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/BookReceptacleBlock.java

@@ -0,0 +1,136 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.advancement.ProgressionAdvancements;
+import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
+import net.dnorberg.rivencraft.portal.CrystalPortalNetwork;
+import net.dnorberg.rivencraft.portal.PortalBookTravel;
+
+
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.sounds.SoundEvents;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.context.BlockPlaceContext;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.block.BaseEntityBlock;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.RenderShape;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.entity.BlockEntityTicker;
+import net.minecraft.world.level.block.entity.BlockEntityType;
+
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.StateDefinition;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.EnumProperty;
+import net.minecraft.world.level.block.state.properties.BooleanProperty;
+import net.minecraft.world.phys.BlockHitResult;
+import net.minecraft.world.phys.shapes.CollisionContext;
+import net.minecraft.world.phys.shapes.VoxelShape;
+
+/** A book-holding crystal attachment, with server-authoritative frame activation. */
+public final class BookReceptacleBlock extends BaseEntityBlock {
+    public static final EnumProperty<Direction> FACING = BlockStateProperties.FACING;
+    public static final BooleanProperty HAS_BOOK = BlockStateProperties.HAS_BOOK;
+
+    public BookReceptacleBlock(Properties properties) {
+        super(properties);
+        registerDefaultState(stateDefinition.any().setValue(FACING, Direction.NORTH).setValue(HAS_BOOK, false));
+    }
+
+    @Override protected RenderShape getRenderShape(BlockState state) { return RenderShape.MODEL; }
+    @Override protected VoxelShape getShape(BlockState state, BlockGetter level, BlockPos pos,
+                                             CollisionContext context) {
+        return switch (state.getValue(FACING)) {
+            case NORTH -> Block.box(0, 0, 10, 16, 16, 16);
+            case SOUTH -> Block.box(0, 0, 0, 16, 16, 6);
+            case EAST -> Block.box(0, 0, 0, 6, 16, 16);
+            case WEST -> Block.box(10, 0, 0, 16, 16, 16);
+            case UP -> Block.box(0, 0, 0, 16, 6, 16);
+            case DOWN -> Block.box(0, 10, 0, 16, 16, 16);
+        };
+    }
+    @Override protected void createBlockStateDefinition(StateDefinition.Builder<Block, BlockState> builder) {
+        builder.add(FACING, HAS_BOOK);
+    }
+    @Override public BlockEntity newBlockEntity(BlockPos pos, BlockState state) {
+        return new BookReceptacleBlockEntity(pos, state);
+    }
+    @Override public <T extends BlockEntity> BlockEntityTicker<T> getTicker(Level level, BlockState state,
+            BlockEntityType<T> type) {
+        return level instanceof ServerLevel
+                ? createTickerHelper(type, Rivencraft.BOOK_RECEPTACLE_BLOCK_ENTITY.get(), (world, pos, current, holder) -> BookReceptacleBlockEntity.serverTick((ServerLevel) world, pos, holder))
+                : null;
+    }
+    @Override public BlockState getStateForPlacement(BlockPlaceContext context) {
+        Direction face = context.getClickedFace();
+        if (!context.getLevel().getBlockState(
+                context.getClickedPos().relative(face.getOpposite())).is(Rivencraft.CRYSTAL_BLOCK.get())) return null;
+        return defaultBlockState().setValue(FACING, face);
+    }
+
+    @Override protected InteractionResult useItemOn(ItemStack stack, BlockState state, Level level, BlockPos pos,
+            Player player, InteractionHand hand, BlockHitResult hit) {
+        if (!isBoundBook(stack)) return InteractionResult.TRY_WITH_EMPTY_HAND;
+        if (level.isClientSide()) return InteractionResult.SUCCESS;
+        if (!(level instanceof ServerLevel server) ||
+                !(level.getBlockEntity(pos) instanceof BookReceptacleBlockEntity holder)) return InteractionResult.FAIL;
+        if (!holder.getBook().isEmpty()) return InteractionResult.FAIL;
+        CrystalPortalNetwork.Plan plan = CrystalPortalNetwork.plan(server, pos);
+        if (!plan.valid()) {
+            if (player instanceof ServerPlayer serverPlayer) serverPlayer.sendOverlayMessage(Component.translatable("message.rivencraft.portal.invalid_frame"));
+            return InteractionResult.FAIL;
+        }
+        if (!PortalBookTravel.available(server, stack)) {
+            if (player instanceof ServerPlayer serverPlayer) serverPlayer.sendOverlayMessage(Component.translatable("message.rivencraft.descriptive_book.unavailable"));
+            return InteractionResult.FAIL;
+        }
+        holder.setBook(stack.copyWithCount(1));
+        if (!CrystalPortalNetwork.activate(server, pos, plan, player)) {
+            holder.takeBook();
+            return InteractionResult.FAIL;
+        }
+        if (!player.getAbilities().instabuild) stack.shrink(1);
+        level.playSound(null, pos, SoundEvents.ENCHANTMENT_TABLE_USE, SoundSource.BLOCKS, 1, 1);
+        if (player instanceof ServerPlayer serverPlayer)
+            ProgressionAdvancements.award(serverPlayer, ProgressionAdvancements.OPEN_PORTAL);
+        return InteractionResult.SUCCESS;
+    }
+
+    @Override protected InteractionResult useWithoutItem(BlockState state, Level level, BlockPos pos,
+            Player player, BlockHitResult hit) {
+        if (level.isClientSide()) return InteractionResult.SUCCESS;
+        if (level instanceof ServerLevel server && level.getBlockEntity(pos) instanceof BookReceptacleBlockEntity holder
+                && !holder.getBook().isEmpty()) {
+            CrystalPortalNetwork.shutdown(server, pos);
+            ItemStack book = holder.takeBook();
+            if (!player.getInventory().add(book)) player.drop(book, false, net.minecraft.util.Prediction.SERVER_ONLY);
+            level.playSound(null, pos, SoundEvents.BOOK_PAGE_TURN, SoundSource.BLOCKS, 1, 1);
+            return InteractionResult.SUCCESS;
+        }
+        return InteractionResult.PASS;
+    }
+
+    @Override protected void neighborChanged(BlockState state, Level level, BlockPos pos, Block neighbor,
+            net.minecraft.world.level.redstone.Orientation orientation, boolean moved) {
+        super.neighborChanged(state, level, pos, neighbor, orientation, moved);
+        BlockPos support = pos.relative(state.getValue(FACING).getOpposite());
+        if (!level.isClientSide() && level.hasChunkAt(support) && !level.getBlockState(support)
+                .is(Rivencraft.CRYSTAL_BLOCK.get())) level.destroyBlock(pos, true);
+    }
+
+    private static boolean isBoundBook(ItemStack stack) {
+        return stack.is(Rivencraft.LINKING_BOOK.get()) && stack.has(Rivencraft.LINK_BOOK_TARGET.get())
+                || stack.is(Rivencraft.DESCRIPTIVE_BOOK.get()) && stack.has(Rivencraft.AGE_BOOK_ID.get());
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/BookStandBlock.java

@@ -0,0 +1,33 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.block.entity.BookStandBlockEntity;
+import net.minecraft.core.BlockPos;
+import net.minecraft.sounds.SoundEvents;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.util.Prediction;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.LecternBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.phys.BlockHitResult;
+
+/** Vanilla lectern geometry with Rivencraft storage instead of a vanilla book menu. */
+public final class BookStandBlock extends LecternBlock {
+    public BookStandBlock(Properties properties) { super(properties); }
+    @Override public BlockEntity newBlockEntity(BlockPos pos, BlockState state) { return new BookStandBlockEntity(pos, state); }
+    @Override protected InteractionResult useWithoutItem(BlockState state, Level level, BlockPos pos, Player player, BlockHitResult hit) {
+        if (!(level.getBlockEntity(pos) instanceof BookStandBlockEntity stand)) return InteractionResult.PASS;
+        if (player.isShiftKeyDown() && !level.isClientSide()) {
+            var book = stand.takeBook();
+            level.setBlock(pos, Blocks.LECTERN.defaultBlockState().setValue(FACING, state.getValue(FACING)), 3);
+            if (!player.getInventory().add(book)) player.drop(book, false, Prediction.SERVER_ONLY);
+            level.playSound(null, pos, SoundEvents.BOOK_PAGE_TURN, SoundSource.BLOCKS, 1, 1);
+        }
+        return InteractionResult.SUCCESS;
+    }
+    @Override protected net.minecraft.world.MenuProvider getMenuProvider(BlockState state, Level level, BlockPos pos) { return null; }
+    @Override protected int getAnalogOutputSignal(BlockState state, Level level, BlockPos pos, net.minecraft.core.Direction direction) { return 0; }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/CloudPlatformBlock.java

@@ -0,0 +1,17 @@
+package net.dnorberg.rivencraft.block;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.LevelReader;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.state.BlockState;
+
+/** Solid crystal-textured arrival footing that cannot be collected. */
+public final class CloudPlatformBlock extends Block {
+    public CloudPlatformBlock(Properties properties) { super(properties); }
+
+    @Override
+    protected ItemStack getCloneItemStack(LevelReader level, BlockPos pos, BlockState state, boolean includeData) {
+        return ItemStack.EMPTY;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/CrystalPortalBlock.java

@@ -0,0 +1,80 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
+import net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity;
+import net.dnorberg.rivencraft.portal.CrystalPortalNetwork;
+import net.dnorberg.rivencraft.portal.PortalTravelCooldown;
+import net.dnorberg.rivencraft.portal.PortalTravelQueue;
+import net.dnorberg.rivencraft.Rivencraft;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.BaseEntityBlock;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.RenderShape;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.StateDefinition;
+import net.minecraft.world.level.block.state.properties.BooleanProperty;
+import net.minecraft.world.level.block.state.properties.EnumProperty;
+import net.minecraft.world.level.material.Fluid;
+
+/** Non-solid linked surface; all travel is delegated to the held book's rules. */
+public final class CrystalPortalBlock extends BaseEntityBlock {
+    // Retained so portal blocks already saved with this state still deserialize.
+    public static final BooleanProperty LIVE_VIEW = BooleanProperty.create("live_view");
+    public static final EnumProperty<Direction.Axis> AXIS = EnumProperty.create("axis", Direction.Axis.class);
+
+    public CrystalPortalBlock(Properties properties) {
+        super(properties);
+        registerDefaultState(stateDefinition.any().setValue(LIVE_VIEW, false).setValue(AXIS, Direction.Axis.Z));
+    }
+    @Override protected void createBlockStateDefinition(StateDefinition.Builder<Block, BlockState> builder) {
+        builder.add(LIVE_VIEW, AXIS);
+    }
+    @Override protected RenderShape getRenderShape(BlockState state) {
+        // Keep the animated fallback until the optional destination view has
+        // actually been established, including after a world restart.
+        return net.dnorberg.rivencraft.compat.RebornBookPreviews.available() && state.getValue(LIVE_VIEW)
+                ? RenderShape.INVISIBLE : RenderShape.MODEL;
+    }
+    @Override public BlockEntity newBlockEntity(BlockPos pos, BlockState state) {
+        return new CrystalPortalBlockEntity(pos, state);
+    }
+    @Override protected boolean canBeReplaced(BlockState state, Fluid fluid) { return false; }
+
+    @Override protected void entityInside(BlockState state, Level level, BlockPos pos, Entity entity, net.minecraft.world.entity.InsideBlockEffectApplier effects, boolean precise) {
+        if (!(level instanceof ServerLevel server) || !entity.canUsePortal(false)) return;
+        long now = server.getServer().getTickCount();
+        if (PortalTravelCooldown.blocked(entity, now)) return;
+        if (!(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
+                || portal.receptacle() == null || !level.hasChunkAt(portal.receptacle())
+                || !(level.getBlockEntity(portal.receptacle()) instanceof BookReceptacleBlockEntity holder)) return;
+        ItemStack book = holder.getBook();
+        if (book.isEmpty()) return;
+        PortalTravelCooldown.mark(entity, now);
+        PortalTravelQueue.enqueue(entity, server, pos, portal.receptacle(), book, now);
+    }
+
+    @Override protected void neighborChanged(BlockState state, Level level, BlockPos pos, Block neighbor,
+            net.minecraft.world.level.redstone.Orientation orientation, boolean moved) {
+        super.neighborChanged(state, level, pos, neighbor, orientation, moved);
+        if (!(level instanceof ServerLevel server)
+                || !(level.getBlockEntity(pos) instanceof CrystalPortalBlockEntity portal)
+                || portal.receptacle() == null) return;
+        // Like a vanilla portal, validate when the frame changes, not on a
+        // repeating timer that can race block entities loading after restart.
+        if (CrystalPortalNetwork.cellStatus(server, pos, portal.receptacle())
+                == CrystalPortalNetwork.CellStatus.INVALID) server.removeBlock(pos, false);
+    }
+
+    @Override protected void tick(BlockState state, ServerLevel level, BlockPos pos, RandomSource random) {
+        // Ignore validation ticks saved by older builds. Frame edits are
+        // handled by neighborChanged, and the receptacle maintains the view.
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/DecayBlock.java

@@ -0,0 +1,46 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.age.PortInstabilityRuntime;
+import net.dnorberg.rivencraft.age.PortInstabilityConfig;
+import net.minecraft.core.BlockPos;
+import net.minecraft.util.StringRepresentable;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.StateDefinition;
+import net.minecraft.world.level.block.state.properties.EnumProperty;
+
+/** The four colored decay variants selected by the current instability deck. */
+public final class DecayBlock extends Block {
+    public static final EnumProperty<Color> COLOR = EnumProperty.create("color", Color.class);
+
+    public DecayBlock(Properties properties) {
+        super(properties);
+        registerDefaultState(stateDefinition.any().setValue(COLOR, Color.BLUE));
+    }
+
+    @Override
+    protected void createBlockStateDefinition(StateDefinition.Builder<Block, BlockState> builder) {
+        builder.add(COLOR);
+    }
+
+    @Override
+    public void stepOn(Level level, BlockPos pos, BlockState state, Entity entity) {
+        if (level instanceof net.minecraft.server.level.ServerLevel server && state.getValue(COLOR) == Color.WHITE
+                && PortInstabilityConfig.decayEnabled() && PortInstabilityConfig.instabilityWorldMutation()
+                && PortInstabilityRuntime.isAge(server)) {
+            entity.hurtServer(server, level.damageSources().magic(), 1.0F);
+        }
+        super.stepOn(level, pos, state, entity);
+    }
+
+    public enum Color implements StringRepresentable {
+        BLUE, PURPLE, RED, WHITE;
+
+        @Override
+        public String getSerializedName() {
+            return name().toLowerCase(java.util.Locale.ROOT);
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/LinkModifierBlock.java

@@ -0,0 +1,51 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity;
+import net.dnorberg.rivencraft.menu.LinkModifierMenu;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.SimpleMenuProvider;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.context.BlockPlaceContext;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.BaseEntityBlock;
+import net.minecraft.world.level.block.RenderShape;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.StateDefinition;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.EnumProperty;
+import net.minecraft.world.phys.BlockHitResult;
+
+public final class LinkModifierBlock extends BaseEntityBlock {
+    public static final EnumProperty<Direction> FACING = BlockStateProperties.HORIZONTAL_FACING;
+
+    public LinkModifierBlock(Properties properties) {
+        super(properties);
+        registerDefaultState(stateDefinition.any().setValue(FACING, Direction.NORTH));
+    }
+
+    @Override protected void createBlockStateDefinition(StateDefinition.Builder<net.minecraft.world.level.block.Block,
+            BlockState> builder) { builder.add(FACING); }
+    @Override public BlockState getStateForPlacement(BlockPlaceContext context) {
+        return defaultBlockState().setValue(FACING, context.getHorizontalDirection().getOpposite());
+    }
+    @Override protected RenderShape getRenderShape(BlockState state) { return RenderShape.MODEL; }
+    @Override public BlockEntity newBlockEntity(BlockPos pos, BlockState state) {
+        return new LinkModifierBlockEntity(pos, state);
+    }
+    @Override protected InteractionResult useWithoutItem(BlockState state, Level level, BlockPos pos,
+                                                          Player player, BlockHitResult hit) {
+        if (!level.isClientSide() && player instanceof ServerPlayer serverPlayer
+                && level.getBlockEntity(pos) instanceof LinkModifierBlockEntity modifier) {
+            serverPlayer.openMenu(new SimpleMenuProvider(
+                    (id, inventory, ignored) -> new LinkModifierMenu(id, inventory, modifier),
+                    Component.translatable("container.rivencraft.link_modifier")),
+                    buffer -> buffer.writeBlockPos(pos));
+        }
+        return InteractionResult.SUCCESS;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/WritingDeskBlock.java

@@ -0,0 +1,83 @@
+package net.dnorberg.rivencraft.block;
+
+import com.mojang.serialization.MapCodec;
+import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
+import net.dnorberg.rivencraft.menu.WritingDeskMenu;
+import net.dnorberg.rivencraft.writing.WritingDeskCatalog;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Containers;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.SimpleMenuProvider;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.context.BlockPlaceContext;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.BaseEntityBlock;
+import net.minecraft.world.level.block.RenderShape;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.state.StateDefinition;
+import net.minecraft.world.level.block.state.properties.BlockStateProperties;
+import net.minecraft.world.level.block.state.properties.EnumProperty;
+import net.minecraft.world.level.block.state.properties.BooleanProperty;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.entity.LivingEntity;
+import org.jetbrains.annotations.Nullable;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.phys.BlockHitResult;
+
+public final class WritingDeskBlock extends BaseEntityBlock {
+    public static final EnumProperty<Direction> FACING = BlockStateProperties.HORIZONTAL_FACING;
+    public static final BooleanProperty EXTENSION = BooleanProperty.create("extension");
+
+    public WritingDeskBlock(Properties properties) {
+        super(properties);
+        registerDefaultState(stateDefinition.any().setValue(FACING, Direction.NORTH).setValue(EXTENSION, false));
+    }
+
+    @Override protected void createBlockStateDefinition(StateDefinition.Builder<net.minecraft.world.level.block.Block, BlockState> builder) {
+        builder.add(FACING, EXTENSION);
+    }
+    @Override public BlockState getStateForPlacement(BlockPlaceContext context) {
+        Direction facing = context.getHorizontalDirection().getOpposite();
+        BlockPos extension = context.getClickedPos().relative(facing.getClockWise());
+        return context.getLevel().getBlockState(extension).canBeReplaced(context)
+                ? defaultBlockState().setValue(FACING, facing) : null;
+    }
+    @Override public void setPlacedBy(Level level, BlockPos pos, BlockState state,
+                                      @Nullable LivingEntity placer, ItemStack stack) {
+        super.setPlacedBy(level, pos, state, placer, stack);
+        level.setBlock(pos.relative(state.getValue(FACING).getClockWise()),
+                state.setValue(EXTENSION, true), 3);
+    }
+    @Override protected RenderShape getRenderShape(BlockState state) { return RenderShape.MODEL; }
+    @Override public BlockEntity newBlockEntity(BlockPos pos, BlockState state) {
+        return state.getValue(EXTENSION) ? null : new WritingDeskBlockEntity(pos, state);
+    }
+    @Override protected InteractionResult useWithoutItem(BlockState state, Level level, BlockPos pos,
+                                                          Player player, BlockHitResult hit) {
+        BlockPos controller = state.getValue(EXTENSION)
+                ? pos.relative(state.getValue(FACING).getCounterClockWise()) : pos;
+        if (!level.isClientSide() && player instanceof ServerPlayer serverPlayer
+                && level.getBlockEntity(controller) instanceof WritingDeskBlockEntity desk) {
+            serverPlayer.openMenu(new SimpleMenuProvider(
+                    (id, inventory, ignored) -> new WritingDeskMenu(id, inventory, desk),
+                    Component.translatable("container.rivencraft.writing_desk")),
+                    buffer -> {
+                        buffer.writeBlockPos(controller);
+                        WritingDeskCatalog.write(buffer, WritingDeskCatalog.available(desk));
+                    });
+        }
+        return InteractionResult.SUCCESS;
+    }
+    @Override protected void affectNeighborsAfterRemoval(BlockState state, net.minecraft.server.level.ServerLevel level,
+                                                           BlockPos pos, boolean movedByPiston) {
+        BlockPos other = pos.relative(state.getValue(FACING).getClockWise(), state.getValue(EXTENSION) ? -1 : 1);
+        BlockState otherState = level.getBlockState(other);
+        if (otherState.is(this) && otherState.getValue(EXTENSION) != state.getValue(EXTENSION)
+                && otherState.getValue(FACING) == state.getValue(FACING))
+            level.setBlock(other, net.minecraft.world.level.block.Blocks.AIR.defaultBlockState(), 35);
+        Containers.updateNeighboursAfterDestroy(state, level, pos);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/entity/BookReceptacleBlockEntity.java

@@ -0,0 +1,110 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.BookReceptacleBlock;
+import net.dnorberg.rivencraft.portal.CrystalPortalNetwork;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.network.protocol.game.ClientboundBlockEntityDataPacket;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.storage.ValueInput;
+import net.minecraft.world.level.storage.ValueOutput;
+
+/** One persisted book owns the whole crystal network. Portal cells retain only its position. */
+public final class BookReceptacleBlockEntity extends BlockEntity {
+    private ItemStack book = ItemStack.EMPTY;
+    private boolean restore = true;
+    private int skyColor = 0xffffff;
+    public BookReceptacleBlockEntity(BlockPos pos, BlockState state) {
+        super(Rivencraft.BOOK_RECEPTACLE_BLOCK_ENTITY.get(), pos, state);
+    }
+    public ItemStack getBook() { return book; }
+    public int skyColor() { return skyColor; }
+    public void setBook(ItemStack value) {
+        if (level instanceof ServerLevel server)
+            net.dnorberg.rivencraft.compat.RebornCrystalPortals.remove(server, worldPosition);
+        book = value.copyWithCount(1);
+        restore = true;
+        skyColor = 0xffffff;
+        if (level instanceof ServerLevel source) {
+            var destination = book.get(Rivencraft.LINK_BOOK_TARGET.get());
+            var id = book.is(Rivencraft.DESCRIPTIVE_BOOK.get()) ? book.get(Rivencraft.AGE_BOOK_ID.get())
+                    : destination == null ? null : destination.dimension();
+            var target = id == null ? null : source.getServer().getLevel(net.minecraft.resources.ResourceKey.create(
+                    net.minecraft.core.registries.Registries.DIMENSION, id));
+            if (target != null) {
+                var pos = destination == null ? net.dnorberg.rivencraft.age.PortAgeTravel.resolveLanding(target, !book.getOrDefault(Rivencraft.LINK_PROPERTIES.get(),
+                        net.dnorberg.rivencraft.item.LinkProperties.NONE).has(net.dnorberg.rivencraft.item.LinkProperties.DISABLE_PLATFORM))
+                        : BlockPos.containing(destination.x(), destination.y(), destination.z());
+                if (pos != null) {
+                    int written = net.dnorberg.rivencraft.age.PortAgeColors.forLevel(target).sky();
+                    String type = target.dimensionTypeRegistration().unwrapKey()
+                            .map(key -> key.identifier().getPath()).orElse("");
+                    skyColor = written >= 0 ? written
+                            : target.dimension() == net.minecraft.world.level.Level.NETHER || type.endsWith("_sky_nether")
+                                ? 0x6b2725
+                            : target.dimension() == net.minecraft.world.level.Level.END || type.endsWith("_sky_end")
+                                ? 0x211835
+                            : net.minecraft.util.ARGB.colorFromVector3f(target.environmentAttributes().getValue(
+                                    net.minecraft.world.attribute.EnvironmentAttributes.SKY_COLOR, pos)) & 0xffffff;
+                }
+            }
+        }
+        sync();
+    }
+    public ItemStack takeBook() {
+        if (level instanceof ServerLevel server)
+            net.dnorberg.rivencraft.compat.RebornCrystalPortals.remove(server, worldPosition);
+        ItemStack result = book; book = ItemStack.EMPTY; skyColor = 0xffffff; sync(); return result;
+    }
+    private void sync() {
+        setChanged();
+        if (level != null && !level.isClientSide()) {
+            BlockState current = level.getBlockState(worldPosition);
+            if (current.is(Rivencraft.BOOK_RECEPTACLE.get())) {
+                level.setBlock(worldPosition, current.setValue(BookReceptacleBlock.HAS_BOOK, !book.isEmpty()), 2);
+                level.sendBlockUpdated(worldPosition, current, level.getBlockState(worldPosition), 2);
+            }
+        }
+    }
+    public static void serverTick(ServerLevel level, BlockPos pos, BookReceptacleBlockEntity holder) {
+        if (holder.book.isEmpty()) { holder.restore = false; return; }
+        int interval = holder.restore ? 20 : 200;
+        if (level.getGameTime() % interval != Math.floorMod(pos.asLong(), interval)) return;
+        var plan = CrystalPortalNetwork.plan(level, pos);
+        if (plan.waitingForChunks()) return;
+        boolean restoring = holder.restore;
+        if (restoring && !plan.valid() && CrystalPortalNetwork.recoverSavedOwners(level, pos))
+            plan = CrystalPortalNetwork.plan(level, pos);
+        if (restoring && plan.valid()) CrystalPortalNetwork.setLiveView(level, plan, false);
+        CrystalPortalNetwork.reconcile(level, pos, plan);
+        holder.restore = false;
+        if (restoring) holder.sync();
+    }
+    @Override protected void loadAdditional(ValueInput input) {
+        super.loadAdditional(input);
+        book = input.read("Book", ItemStack.CODEC).orElse(ItemStack.EMPTY);
+        skyColor = input.getIntOr("SkyColor", 0xffffff);
+        restore = true;
+    }
+    @Override protected void saveAdditional(ValueOutput output) {
+        super.saveAdditional(output);
+        if (!book.isEmpty()) output.store("Book", ItemStack.CODEC, book);
+        output.putInt("SkyColor", skyColor);
+    }
+    @Override public CompoundTag getUpdateTag(HolderLookup.Provider registries) { return saveWithoutMetadata(registries); }
+    @Override public ClientboundBlockEntityDataPacket getUpdatePacket() { return ClientboundBlockEntityDataPacket.create(this); }
+    @Override public void preRemoveSideEffects(BlockPos pos, BlockState oldState) {
+        if (level instanceof ServerLevel server) {
+            CrystalPortalNetwork.shutdown(server, pos);
+            ItemStack removed = book;
+            book = ItemStack.EMPTY;
+            net.minecraft.world.Containers.dropItemStack(level, pos.getX() + 0.5, pos.getY() + 0.5, pos.getZ() + 0.5, removed);
+        }
+        super.preRemoveSideEffects(pos, oldState);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/entity/BookStandBlockEntity.java

@@ -0,0 +1,40 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.network.protocol.game.ClientboundBlockEntityDataPacket;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.storage.ValueInput;
+import net.minecraft.world.level.storage.ValueOutput;
+
+/** One stored book or page, synchronized independently of the player's inventory. */
+public final class BookStandBlockEntity extends BlockEntity {
+    private ItemStack book = ItemStack.EMPTY;
+    public BookStandBlockEntity(BlockPos pos, BlockState state) { super(Rivencraft.BOOK_STAND_BLOCK_ENTITY.get(), pos, state); }
+    public ItemStack getBook() { return book; }
+    public void setBook(ItemStack stack) { book = stack; sync(); }
+    public ItemStack takeBook() { ItemStack result = book; book = ItemStack.EMPTY; sync(); return result; }
+    private void sync() {
+        setChanged();
+        if (level != null && !level.isClientSide()) level.sendBlockUpdated(worldPosition, getBlockState(), getBlockState(), 2);
+    }
+    @Override protected void loadAdditional(ValueInput input) {
+        super.loadAdditional(input);
+        book = input.read("Book", ItemStack.CODEC).orElse(ItemStack.EMPTY);
+    }
+    @Override protected void saveAdditional(ValueOutput output) {
+        super.saveAdditional(output);
+        if (!book.isEmpty()) output.store("Book", ItemStack.CODEC, book);
+    }
+    @Override public CompoundTag getUpdateTag(HolderLookup.Provider registries) { return saveWithoutMetadata(registries); }
+    @Override public ClientboundBlockEntityDataPacket getUpdatePacket() { return ClientboundBlockEntityDataPacket.create(this); }
+    @Override public void preRemoveSideEffects(BlockPos pos, BlockState oldState) {
+        if (level != null && !level.isClientSide())
+            net.minecraft.world.Containers.dropItemStack(level, pos.getX() + 0.5, pos.getY() + 1, pos.getZ() + 0.5, takeBook());
+        super.preRemoveSideEffects(pos, oldState);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/entity/CrystalPortalBlockEntity.java

@@ -0,0 +1,33 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.network.protocol.game.ClientboundBlockEntityDataPacket;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.storage.ValueInput;
+import net.minecraft.world.level.storage.ValueOutput;
+
+/** One stored book or page, synchronized independently of the player's inventory. */
+public final class CrystalPortalBlockEntity extends BlockEntity {
+    private BlockPos receptacle;
+    public CrystalPortalBlockEntity(BlockPos pos, BlockState state) { super(Rivencraft.CRYSTAL_PORTAL_BLOCK_ENTITY.get(), pos, state); }
+    public BlockPos receptacle() { return receptacle; }
+    public void setReceptacle(BlockPos pos) {
+        receptacle = pos.immutable();
+        setChanged();
+        if (level != null && !level.isClientSide()) level.sendBlockUpdated(worldPosition, getBlockState(), getBlockState(), 2);
+    }
+    @Override protected void loadAdditional(ValueInput input) {
+        super.loadAdditional(input);
+        receptacle = input.read("Receptacle", BlockPos.CODEC).orElse(null);
+    }
+    @Override protected void saveAdditional(ValueOutput output) {
+        super.saveAdditional(output);
+        if (receptacle != null) output.store("Receptacle", BlockPos.CODEC, receptacle);
+    }
+    @Override public CompoundTag getUpdateTag(HolderLookup.Provider registries) { return saveWithoutMetadata(registries); }
+    @Override public ClientboundBlockEntityDataPacket getUpdatePacket() { return ClientboundBlockEntityDataPacket.create(this); }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/entity/LinkModifierBlockEntity.java

@@ -0,0 +1,69 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.storage.ValueInput;
+import net.minecraft.world.level.storage.ValueOutput;
+import net.minecraft.core.NonNullList;
+import net.minecraft.world.Container;
+import net.minecraft.world.ContainerHelper;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+
+/** One persisted book slot; edits are performed by the server menu. */
+public final class LinkModifierBlockEntity extends BlockEntity implements Container {
+    private NonNullList<ItemStack> items = NonNullList.withSize(1, ItemStack.EMPTY);
+
+    public LinkModifierBlockEntity(BlockPos pos, BlockState state) {
+        super(Rivencraft.LINK_MODIFIER_BLOCK_ENTITY.get(), pos, state);
+    }
+
+    @Override public int getContainerSize() { return 1; }
+    @Override public boolean isEmpty() { return items.getFirst().isEmpty(); }
+    @Override public ItemStack getItem(int slot) { return items.get(slot); }
+    @Override public ItemStack removeItem(int slot, int amount) {
+        ItemStack removed = ContainerHelper.removeItem(items, slot, amount);
+        if (!removed.isEmpty()) setChanged();
+        return removed;
+    }
+    @Override public ItemStack removeItemNoUpdate(int slot) {
+        ItemStack removed = ContainerHelper.takeItem(items, slot);
+        if (!removed.isEmpty()) setChanged();
+        return removed;
+    }
+    @Override public void setItem(int slot, ItemStack stack) {
+        items.set(slot, stack.copyWithCount(Math.min(1, stack.getCount())));
+        setChanged();
+    }
+    @Override public boolean canPlaceItem(int slot, ItemStack stack) {
+        return slot == 0 && (stack.is(Rivencraft.LINKING_BOOK.get())
+                || stack.is(Rivencraft.DESCRIPTIVE_BOOK.get()));
+    }
+    @Override public boolean stillValid(Player player) {
+        return level != null && level.isLoaded(worldPosition) && level.getBlockEntity(worldPosition) == this
+                && player.distanceToSqr(worldPosition.getX() + 0.5, worldPosition.getY() + 0.5,
+                        worldPosition.getZ() + 0.5) <= 64.0;
+    }
+    @Override public void preRemoveSideEffects(BlockPos pos, BlockState oldState) {
+        if (level != null && !level.isClientSide()) {
+            net.minecraft.world.Containers.dropContents(level, pos, this);
+            clearContent();
+        }
+        super.preRemoveSideEffects(pos, oldState);
+    }
+    @Override public void clearContent() {
+        items = NonNullList.withSize(1, ItemStack.EMPTY);
+        setChanged();
+    }
+    @Override protected void loadAdditional(ValueInput input) {
+        super.loadAdditional(input);
+        items = NonNullList.withSize(1, ItemStack.EMPTY);
+        ContainerHelper.loadAllItems(input, items);
+    }
+    @Override protected void saveAdditional(ValueOutput output) {
+        super.saveAdditional(output);
+        ContainerHelper.saveAllItems(output, items);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/entity/PortBookBinderBlockEntity.java

@@ -112,6 +112,36 @@ public final class PortBookBinderBlockEntity extends BlockEntity implements Cont
         return true;
     }
 
+    /** Validate the complete collection before moving any page, as in 1.21.1. */
+    public ItemStack importCollection(ItemStack collection, int index) {
+        if (!net.dnorberg.rivencraft.item.CollationFolderItem.isCollection(collection)
+                || collection.getCount() != 1) return ItemStack.EMPTY;
+        var contents = collection.getOrDefault(Rivencraft.NOTEBOOK_CONTENTS.get(),
+                net.dnorberg.rivencraft.writing.NotebookContents.EMPTY);
+        int end = nextPageIndex();
+        if (index < 0 || index > end) return ItemStack.EMPTY;
+        ItemStack panel = ItemStack.EMPTY;
+        List<ItemStack> writing = new ArrayList<>();
+        for (ItemStack page : contents.pages()) {
+            if (page.isEmpty()) continue;
+            if (!page.is(Rivencraft.PAGE.get()) || page.getCount() != 1) return ItemStack.EMPTY;
+            if (PageItem.isLinkPanel(page)) {
+                if (!panel.isEmpty() || !items.get(PANEL).isEmpty()) return ItemStack.EMPTY;
+                panel = page;
+            } else if (validSymbolPage(page)) writing.add(page);
+            else return ItemStack.EMPTY;
+        }
+        if (end + writing.size() > PAGE_COUNT || writing.isEmpty() && panel.isEmpty()) return ItemStack.EMPTY;
+        if (!panel.isEmpty()) items.set(PANEL, panel.copy());
+        for (int current = end - 1; current >= index; current--)
+            items.set(FIRST_PAGE + current + writing.size(), items.get(FIRST_PAGE + current));
+        for (ItemStack page : writing) items.set(FIRST_PAGE + index++, page.copy());
+        ItemStack emptied = collection.copy();
+        emptied.set(Rivencraft.NOTEBOOK_CONTENTS.get(), net.dnorberg.rivencraft.writing.NotebookContents.EMPTY);
+        setChanged();
+        return emptied;
+    }
+
     public ItemStack takePage(int index) {
         int end = nextPageIndex();
         if (index < 0 || index >= end) return ItemStack.EMPTY;

ports/mc263/src/main/java/net/dnorberg/rivencraft/block/entity/WritingDeskBlockEntity.java

@@ -0,0 +1,173 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.InkVialItem;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
+import net.dnorberg.rivencraft.writing.InkVialExchange;
+import net.dnorberg.rivencraft.writing.PageContent;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.world.level.storage.ValueInput;
+import net.minecraft.world.level.storage.ValueOutput;
+import net.minecraft.core.NonNullList;
+import net.minecraft.nbt.CompoundTag;
+import net.minecraft.network.protocol.Packet;
+import net.minecraft.network.protocol.game.ClientGamePacketListener;
+import net.minecraft.network.protocol.game.ClientboundBlockEntityDataPacket;
+import net.minecraft.world.Container;
+import net.minecraft.world.ContainerHelper;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+
+/** Collection tabs, paper, ink vials and empty-vial return are owned by the block. */
+public final class WritingDeskBlockEntity extends BlockEntity implements Container {
+    public static final int COLLECTIONS = 88;
+    public static final int INK = COLLECTIONS;
+    public static final int RETURN = INK + 1;
+    public static final int PAPER = INK + 2;
+    /** Unused by new desks; retained so old saves cannot silently lose slot contents. */
+    public static final int LEGACY_OUTPUT = INK + 3;
+    public static final int SIZE = INK + 4;
+    private NonNullList<ItemStack> items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+    private int activeCollection;
+    private int inkRemaining;
+    private ItemStack displayPage = ItemStack.EMPTY;
+
+    public WritingDeskBlockEntity(BlockPos pos, BlockState state) {
+        super(Rivencraft.WRITING_DESK_BLOCK_ENTITY.get(), pos, state);
+    }
+
+    public int activeCollection() { return activeCollection; }
+    public int inkRemaining() { return inkRemaining; }
+    public ItemStack displayPage() { return displayPage; }
+    public void setDisplayPage(ItemStack page) {
+        ItemStack next = page.isEmpty() ? ItemStack.EMPTY : page.copyWithCount(1);
+        if (!ItemStack.matches(displayPage, next)) {
+            displayPage = next;
+            setChanged();
+        }
+    }
+    public void setActiveCollection(int index) {
+        if (index >= 0 && index < COLLECTIONS && activeCollection != index) {
+            activeCollection = index;
+            setChanged();
+        }
+    }
+
+    @Override public int getContainerSize() { return SIZE; }
+    @Override public boolean isEmpty() { return items.stream().allMatch(ItemStack::isEmpty); }
+    @Override public ItemStack getItem(int slot) { return items.get(slot); }
+    @Override public ItemStack removeItem(int slot, int amount) {
+        ItemStack removed = ContainerHelper.removeItem(items, slot, amount);
+        if (!removed.isEmpty()) {
+            if (slot < COLLECTIONS) displayPage = ItemStack.EMPTY;
+            setChanged();
+            if (slot == RETURN) refillEmptyInkBar();
+        }
+        return removed;
+    }
+    @Override public ItemStack removeItemNoUpdate(int slot) { return ContainerHelper.takeItem(items, slot); }
+    @Override public void setItem(int slot, ItemStack stack) {
+        items.set(slot, stack);
+        if (stack.getCount() > getMaxStackSize()) stack.setCount(getMaxStackSize());
+        if (slot < COLLECTIONS) displayPage = ItemStack.EMPTY;
+        setChanged();
+        if (slot == INK || slot == RETURN) refillEmptyInkBar();
+    }
+    @Override public boolean stillValid(Player player) {
+        return level != null && level.isLoaded(worldPosition)
+                && level.getBlockEntity(worldPosition) == this
+                && player.distanceToSqr(worldPosition.getX() + 0.5, worldPosition.getY() + 0.5,
+                        worldPosition.getZ() + 0.5) <= 64.0;
+    }
+    @Override public boolean canPlaceItem(int slot, ItemStack stack) {
+        if (slot < COLLECTIONS) return CollationFolderItem.isCollection(stack)
+                && stack.getOrDefault(Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY)
+                        .pages().stream().noneMatch(page -> PageItem.content(page).kind() == PageContent.Kind.LINK_PANEL)
+                || stack.is(Rivencraft.PAGE.get())
+                && PageItem.content(stack).kind() != PageContent.Kind.LINK_PANEL;
+        return switch (slot) {
+            case INK -> stack.is(Rivencraft.INK_VIAL.get());
+            case RETURN -> false;
+            case PAPER -> stack.is(Items.PAPER);
+            case LEGACY_OUTPUT -> false;
+            default -> false;
+        };
+    }
+
+    /** Consume one vial only when the empty meter can return its glass bottle. */
+    private void refillEmptyInkBar() {
+        if (level != null && !level.isClientSide() && inkRemaining == 0) {
+            int addedInk = InkVialExchange.exchange(items, INK, RETURN);
+            if (addedInk > 0) {
+                inkRemaining = addedInk;
+                setChanged();
+            }
+        }
+    }
+
+    /** The output is virtual; inputs are committed only after a result can be given to a player. */
+    public boolean canConsumeCopyMaterials() {
+        ItemStack paper = items.get(PAPER);
+        if (!canPlaceItem(PAPER, paper) || paper.isEmpty()) return false;
+        int cost = net.dnorberg.rivencraft.writing.WritingInkService.symbolCopyCost();
+        return InkVialExchange.canPay(items, INK, RETURN, inkRemaining, cost);
+    }
+
+    public boolean consumeCopyMaterials() {
+        if (!canConsumeCopyMaterials()) return false;
+        int cost = net.dnorberg.rivencraft.writing.WritingInkService.symbolCopyCost();
+        if (inkRemaining < cost) {
+            inkRemaining += InkVialExchange.exchange(items, INK, RETURN);
+        }
+        inkRemaining -= cost;
+        removeItem(PAPER, 1);
+        setChanged();
+        if (inkRemaining == 0) refillEmptyInkBar();
+        return true;
+    }
+    @Override public void setLevel(Level level) {
+        super.setLevel(level);
+        refillEmptyInkBar();
+    }
+    @Override public void clearContent() {
+        items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+        inkRemaining = 0;
+        displayPage = ItemStack.EMPTY;
+        setChanged();
+    }
+    @Override protected void loadAdditional(ValueInput input) {
+        super.loadAdditional(input);
+        items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+        ContainerHelper.loadAllItems(input, items);
+        activeCollection = Math.clamp(input.getIntOr("ActiveCollection", 0), 0, COLLECTIONS - 1);
+        inkRemaining = Math.clamp(input.getIntOr("InkRemaining", 0), 0, InkVialItem.CAPACITY);
+        displayPage = input.read("DisplayPage", ItemStack.CODEC).orElse(ItemStack.EMPTY);
+        refillEmptyInkBar();
+    }
+    @Override protected void saveAdditional(ValueOutput output) {
+        super.saveAdditional(output);
+        ContainerHelper.saveAllItems(output, items);
+        output.putInt("ActiveCollection", activeCollection);
+        output.putInt("InkRemaining", inkRemaining);
+        if (!displayPage.isEmpty()) output.store("DisplayPage", ItemStack.CODEC, displayPage);
+    }
+    @Override public Packet<ClientGamePacketListener> getUpdatePacket() {
+        return ClientboundBlockEntityDataPacket.create(this);
+    }
+    @Override public CompoundTag getUpdateTag(HolderLookup.Provider registries) {
+        return saveWithoutMetadata(registries);
+    }
+    @Override public void setChanged() {
+        super.setChanged();
+        if (level != null && !level.isClientSide()) {
+            level.sendBlockUpdated(worldPosition, getBlockState(), getBlockState(), 2);
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/client/AgeCatalogClient.java

@@ -20,16 +20,23 @@ public final class AgeCatalogClient {
 
     @SubscribeEvent
     public static void logout(net.neoforged.neoforge.client.event.ClientPlayerNetworkEvent.LoggingOut event) {
+        PortBookPreview.logout();
         net.dnorberg.rivencraft.age.PortAgeColors.updateClient(java.util.Map.of());
         net.dnorberg.rivencraft.age.PortDayCycle.updateClient(java.util.Map.of());
+        net.dnorberg.rivencraft.age.PortAgeDescription.updateClient(java.util.Map.of());
     }
 
     @SubscribeEvent
     public static void register(RegisterClientPayloadHandlersEvent event) {
+        event.register(net.dnorberg.rivencraft.network.BookPreviewPayload.TYPE, (payload, context) -> PortBookPreview.accept(payload));
+        event.register(net.dnorberg.rivencraft.network.WritingDeskCatalogPayload.TYPE, ClientWritingDeskCatalog::handle);
+        event.register(net.dnorberg.rivencraft.network.SereneAgeWhitelistPayload.TYPE, (payload, context) ->
+                net.dnorberg.rivencraft.compat.SereneSeasonsCompatibility.acceptClient(payload.dimensionId(), payload.enabled()));
         event.register(AgeCatalogPayload.TYPE, (payload, context) -> {
             if (!(context.listener() instanceof ClientPacketListener listener)) return;
             net.dnorberg.rivencraft.age.PortAgeColors.updateClient(payload.colors());
             net.dnorberg.rivencraft.age.PortDayCycle.updateClient(payload.dayCycles());
+            net.dnorberg.rivencraft.age.PortAgeDescription.updateClient(payload.descriptions());
             if (listener.getLevel() != null) {
                 listener.getLevel().environmentAttributes().invalidateTickCache();
                 listener.getLevel().updateSkyBrightness();

ports/mc263/src/main/java/net/dnorberg/rivencraft/client/BookReceptacleRenderer.java

@@ -0,0 +1,67 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.math.Axis;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.BookReceptacleBlock;
+import net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity;
+import net.minecraft.client.model.geom.ModelLayers;
+import net.minecraft.client.model.object.book.BookModel;
+import net.minecraft.client.renderer.SubmitNodeCollector;
+import net.minecraft.client.renderer.blockentity.BlockEntityRenderer;
+import net.minecraft.client.renderer.blockentity.BlockEntityRendererProvider;
+import net.minecraft.client.renderer.blockentity.state.BlockEntityRenderState;
+import net.minecraft.client.renderer.feature.ModelFeatureRenderer;
+import net.minecraft.client.renderer.state.level.CameraRenderState;
+import net.minecraft.client.renderer.texture.OverlayTexture;
+import net.minecraft.core.Direction;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.phys.Vec3;
+
+/** The 1.21.1 receptacle book orientation in the 26.3 extracted renderer. */
+public final class BookReceptacleRenderer implements BlockEntityRenderer<BookReceptacleBlockEntity, BookReceptacleRenderer.State> {
+    private static final Identifier LINKING = Identifier.fromNamespaceAndPath("rivencraft", "textures/entity/linking_book.png");
+    private static final Identifier DESCRIPTIVE = Identifier.fromNamespaceAndPath("rivencraft", "textures/entity/descriptive_book.png");
+    private final BookModel model;
+    public BookReceptacleRenderer(BlockEntityRendererProvider.Context context) {
+        model = new BookModel(context.bakeLayer(ModelLayers.BOOK));
+    }
+    public static final class State extends BlockEntityRenderState {
+        boolean present, descriptive;
+        Direction facing = Direction.NORTH;
+    }
+    @Override public State createRenderState() { return new State(); }
+    @Override public void extractRenderState(BookReceptacleBlockEntity holder, State state, float partialTick,
+                                             Vec3 camera, ModelFeatureRenderer.CrumblingOverlay overlay) {
+        BlockEntityRenderer.super.extractRenderState(holder, state, partialTick, camera, overlay);
+        state.present = !holder.getBook().isEmpty() && holder.getBlockState().getValue(BookReceptacleBlock.HAS_BOOK);
+        state.descriptive = holder.getBook().is(Rivencraft.DESCRIPTIVE_BOOK.get());
+        state.facing = holder.getBlockState().getValue(BookReceptacleBlock.FACING);
+    }
+    @Override public void submit(State state, PoseStack pose, SubmitNodeCollector collector, CameraRenderState camera) {
+        if (!state.present) return;
+        pose.pushPose();
+        pose.translate(0.5F, 0.5F, 0.5F);
+        switch (state.facing) {
+            case UP -> {
+                pose.rotateDegrees(Axis.ZP, 180);
+                pose.rotateDegrees(Axis.XP, -90);
+                pose.rotateDegrees(Axis.YP, 90);
+                pose.rotateDegrees(Axis.ZP, 180);
+            }
+            case DOWN -> {
+                pose.rotateDegrees(Axis.XP, -90);
+                pose.rotateDegrees(Axis.YP, 90);
+                pose.rotateDegrees(Axis.ZP, 180);
+            }
+            case NORTH -> pose.rotateDegrees(Axis.YP, -90);
+            case SOUTH -> pose.rotateDegrees(Axis.YP, 90);
+            case EAST -> pose.rotateDegrees(Axis.YP, 180);
+            case WEST -> { }
+        }
+        pose.scale(0.8F, 0.8F, 0.8F);
+        collector.submitModel(model, BookModel.State.forAnimation(0, 0.1F, 0.1F, 0.005F), pose,
+                state.descriptive ? DESCRIPTIVE : LINKING, state.lightCoords, OverlayTexture.NO_OVERLAY, 0);
+        pose.popPose();
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/client/BookStandRenderer.java

@@ -0,0 +1,85 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.math.Axis;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.BookStandBlock;
+import net.dnorberg.rivencraft.block.entity.BookStandBlockEntity;
+import net.minecraft.client.gui.Font;
+import net.minecraft.client.model.geom.ModelLayers;
+import net.minecraft.client.model.object.book.BookModel;
+import net.minecraft.client.renderer.SubmitNodeCollector;
+import net.minecraft.client.renderer.blockentity.BlockEntityRenderer;
+import net.minecraft.client.renderer.blockentity.BlockEntityRendererProvider;
+import net.minecraft.client.renderer.blockentity.state.BlockEntityRenderState;
+import net.minecraft.client.renderer.feature.ModelFeatureRenderer;
+import net.minecraft.client.renderer.item.ItemModelResolver;
+import net.minecraft.client.renderer.item.ItemStackRenderState;
+import net.minecraft.client.renderer.state.level.CameraRenderState;
+import net.minecraft.client.renderer.texture.OverlayTexture;
+import net.minecraft.core.Direction;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.item.ItemDisplayContext;
+import net.minecraft.world.phys.Vec3;
+
+/** Extracted version of the 1.21.1 lectern display, retaining its final page orientation. */
+public final class BookStandRenderer implements BlockEntityRenderer<BookStandBlockEntity, BookStandRenderer.State> {
+    private static final Identifier LINKING = Identifier.fromNamespaceAndPath("rivencraft", "textures/entity/linking_book.png");
+    private static final Identifier DESCRIPTIVE = Identifier.fromNamespaceAndPath("rivencraft", "textures/entity/descriptive_book.png");
+    private final BookModel model;
+    private final ItemModelResolver resolver;
+    private final Font font;
+    public BookStandRenderer(BlockEntityRendererProvider.Context context) {
+        model = new BookModel(context.bakeLayer(ModelLayers.BOOK));
+        resolver = context.itemModelResolver();
+        font = context.font();
+    }
+    public static final class State extends BlockEntityRenderState {
+        final ItemStackRenderState page = new ItemStackRenderState();
+        boolean present, isPage, descriptive;
+        float rotation;
+        Component name;
+    }
+    @Override public State createRenderState() { return new State(); }
+    @Override public void extractRenderState(BookStandBlockEntity stand, State state, float partialTick,
+                                             Vec3 camera, ModelFeatureRenderer.CrumblingOverlay overlay) {
+        BlockEntityRenderer.super.extractRenderState(stand, state, partialTick, camera, overlay);
+        var book = stand.getBook();
+        state.present = !book.isEmpty();
+        state.isPage = book.is(Rivencraft.PAGE.get());
+        state.descriptive = book.is(Rivencraft.DESCRIPTIVE_BOOK.get());
+        state.name = state.present && !state.isPage ? book.getHoverName().copy() : null;
+        Direction facing = stand.getBlockState().getValue(BookStandBlock.FACING);
+        state.rotation = state.isPage ? facing.toYRot() - 180 + (facing.getAxis() == Direction.Axis.X ? 180 : 0)
+                : -facing.getClockWise().toYRot();
+        resolver.updateForTopItem(state.page, state.isPage ? book : net.minecraft.world.item.ItemStack.EMPTY,
+                ItemDisplayContext.FIXED, stand.getLevel(), null, 0);
+    }
+    @Override public void submit(State state, PoseStack pose, SubmitNodeCollector collector, CameraRenderState camera) {
+        if (!state.present) return;
+        pose.pushPose();
+        pose.translate(0.5F, 1.0625F, 0.5F);
+        pose.rotateDegrees(Axis.YP, state.rotation);
+        if (state.isPage) {
+            pose.rotateDegrees(Axis.XP, 67.5F);
+            pose.scale(0.7F, 0.7F, 0.7F);
+            state.page.submit(pose, collector, state.lightCoords, OverlayTexture.NO_OVERLAY, 0);
+        } else {
+            pose.rotateDegrees(Axis.ZP, 67.5F);
+            pose.translate(0, -0.125F, 0);
+            collector.submitModel(model, BookModel.State.forAnimation(0, 0.1F, 0.9F, 1.2F), pose,
+                    state.descriptive ? DESCRIPTIVE : LINKING, state.lightCoords, OverlayTexture.NO_OVERLAY, 0);
+        }
+        pose.popPose();
+        if (state.name != null) {
+            pose.pushPose();
+            pose.translate(0.5F, 1.6F, 0.5F);
+            pose.rotate(camera.orientation);
+            pose.scale(0.025F, -0.025F, 0.025F);
+            collector.submitText(pose, -font.width(state.name) / 2.0F, 0, state.name.getVisualOrderText(),
+                    false, Font.DisplayMode.NORMAL, state.lightCoords, 0xFFFFFFFF, 0, 0);
+            pose.popPose();
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/client/ClientWritingDeskCatalog.java

@@ -0,0 +1,20 @@
+package net.dnorberg.rivencraft.client;
+
+import net.dnorberg.rivencraft.menu.WritingDeskMenu;
+import net.dnorberg.rivencraft.network.WritingDeskCatalogPayload;
+import net.minecraft.client.Minecraft;
+import net.neoforged.neoforge.network.handling.IPayloadContext;
+
+public final class ClientWritingDeskCatalog {
+    private ClientWritingDeskCatalog() {}
+
+    public static void handle(WritingDeskCatalogPayload payload, IPayloadContext context) {
+        context.enqueueWork(() -> {
+            var player = Minecraft.getInstance().player;
+            if (player != null && player.containerMenu instanceof WritingDeskMenu menu
+                    && menu.containerId == payload.containerId()) {
+                menu.setCatalog(payload.symbols());
+            }
+        });
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/client/DroppedBookRenderer.java

@@ -0,0 +1,57 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.math.Axis;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.entity.DroppedBookEntity;
+import net.minecraft.client.model.geom.ModelLayers;
+import net.minecraft.client.model.object.book.BookModel;
+import net.minecraft.client.renderer.SubmitNodeCollector;
+import net.minecraft.client.renderer.entity.EntityRenderer;
+import net.minecraft.client.renderer.entity.EntityRendererProvider;
+import net.minecraft.client.renderer.entity.state.EntityRenderState;
+import net.minecraft.client.renderer.state.level.CameraRenderState;
+import net.minecraft.client.renderer.texture.OverlayTexture;
+import net.minecraft.resources.Identifier;
+
+/** Uses the same skyward-facing open book and textures as the 1.21.1 renderer. */
+public final class DroppedBookRenderer extends EntityRenderer<DroppedBookEntity, DroppedBookRenderer.State> {
+    private static final Identifier LINKING = Identifier.fromNamespaceAndPath("rivencraft", "textures/entity/linking_book.png");
+    private static final Identifier DESCRIPTIVE = Identifier.fromNamespaceAndPath("rivencraft", "textures/entity/descriptive_book.png");
+    private final BookModel model;
+
+    public DroppedBookRenderer(EntityRendererProvider.Context context) {
+        super(context);
+        model = new BookModel(context.bakeLayer(ModelLayers.BOOK));
+        shadowRadius = 0.25F;
+    }
+
+    public static final class State extends EntityRenderState {
+        float yaw;
+        boolean descriptive;
+    }
+
+    @Override
+    public State createRenderState() { return new State(); }
+
+    @Override
+    public void extractRenderState(DroppedBookEntity entity, State state, float partialTick) {
+        super.extractRenderState(entity, state, partialTick);
+        state.yaw = entity.getYRot();
+        state.descriptive = entity.getItem().is(Rivencraft.DESCRIPTIVE_BOOK.get());
+    }
+
+    @Override
+    public void submit(State state, PoseStack pose, SubmitNodeCollector collector, CameraRenderState camera) {
+        pose.pushPose();
+        pose.translate(0.0F, 0.0625F, 0.0F);
+        pose.rotateDegrees(Axis.YP, state.yaw + 90.0F);
+        pose.rotateDegrees(Axis.ZP, 90.0F);
+        pose.scale(0.8F, 0.8F, 0.8F);
+        collector.submitModel(model, BookModel.State.forAnimation(0, 0, 0, 1.2F), pose,
+                state.descriptive ? DESCRIPTIVE : LINKING, state.lightCoords, OverlayTexture.NO_OVERLAY,
+                state.outlineColor);
+        pose.popPose();
+        super.submit(state, pose, collector, camera);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/client/LinkModifierScreen.java

@@ -0,0 +1,198 @@
+package net.dnorberg.rivencraft.client;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.LinkProperties;
+import net.dnorberg.rivencraft.menu.LinkModifierMenu;
+import net.dnorberg.rivencraft.network.SetLinkModifierTitlePayload;
+import net.dnorberg.rivencraft.network.SetLinkModifierSeedPayload;
+import com.mojang.blaze3d.platform.InputConstants;
+import net.minecraft.client.input.MouseButtonEvent;
+import net.minecraft.client.gui.GuiGraphicsExtractor;
+import net.minecraft.client.gui.components.EditBox;
+import net.minecraft.client.gui.screens.inventory.AbstractContainerScreen;
+import net.minecraft.client.input.KeyEvent;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.components.Tooltip;
+import net.minecraft.client.renderer.RenderPipelines;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.item.ItemStack;
+import net.neoforged.neoforge.client.network.ClientPacketDistributor;
+
+/** Existing Legacy single-slot layout, using the 26.3 extraction/input APIs. */
+public final class LinkModifierScreen extends AbstractContainerScreen<LinkModifierMenu> {
+    private static final Identifier BACKGROUND = Identifier.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "textures/gui/link_modifier_legacy.png");
+    private static final int[] FLAGS = {LinkProperties.DISARM, LinkProperties.INTRA_LINKING,
+            LinkProperties.INTRA_LINKING_ONLY, LinkProperties.MAINTAIN_MOMENTUM, LinkProperties.RELATIVE_LINK, LinkProperties.DISABLE_PLATFORM};
+    private static final int[] IDS = {LinkModifierMenu.TOGGLE_DISARM, LinkModifierMenu.TOGGLE_INTRA,
+            LinkModifierMenu.TOGGLE_INTRA_ONLY, LinkModifierMenu.TOGGLE_MOMENTUM, LinkModifierMenu.TOGGLE_RELATIVE, LinkModifierMenu.TOGGLE_PLATFORM};
+    private static final String[] NAMES = {"disarm", "intra_linking", "intra_linking_only", "maintain_momentum", "relative_link", "generate_platform"};
+    private EditBox titleInput;
+    private EditBox seedInput;
+    private Identifier seedAge;
+    private long lastSeed = Long.MIN_VALUE;
+    private ItemStack lastBook = ItemStack.EMPTY;
+    private boolean refreshing;
+    private Button retireButton;
+    private Button confirmRetireButton;
+    private final Button[] options = new Button[6];
+
+    public LinkModifierScreen(LinkModifierMenu menu, Inventory inventory, Component title) {
+        super(menu, inventory, title, 176, 166);
+        inventoryLabelY = 72;
+    }
+    @Override public boolean isPauseScreen() { return false; }
+    @Override protected void init() {
+        super.init();
+        titleInput = new EditBox(font, leftPos + 80, topPos + 56, 87, 14,
+                Component.translatable("screen.rivencraft.link_modifier.title"));
+        titleInput.setMaxLength(32);
+        titleInput.setResponder(value -> {
+            if (!refreshing) ClientPacketDistributor.sendToServer(new SetLinkModifierTitlePayload(menu.containerId, value));
+        });
+        addRenderableWidget(titleInput);
+        seedInput = new EditBox(font, leftPos + 80, topPos + 15, 87, 14,
+                Component.translatable("screen.rivencraft.link_modifier.seed"));
+        seedInput.setMaxLength(21);
+        seedInput.setTooltip(Tooltip.create(Component.translatable("screen.rivencraft.link_modifier.seed_warning")));
+        addRenderableWidget(seedInput);
+        for (int index = 0; index < options.length; index++) {
+            final int option = index;
+            options[index] = addRenderableWidget(new Button(leftPos + 5 + (index / 3) * 20,
+                    topPos + 10 + (index % 3) * 20, 18, 18, label(index), button -> {
+                        if (minecraft != null && minecraft.gameMode != null)
+                            minecraft.gameMode.handleInventoryButtonClick(menu.containerId, IDS[option]);
+                    }, java.util.function.Supplier::get) {
+                @Override protected void extractContents(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+                    int x = getX(), y = getY();
+                    graphics.fill(x, y, x + 18, y + 18, isHoveredOrFocused() ? 0xFFFFFFFF : 0xFFAAAAAA);
+                    graphics.fill(x + 2, y + 2, x + 17, y + 17, !active ? 0xFF555555
+                            : selected(option, menu.book().getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE))
+                                    ? 0xFFBBBBBB : 0xFF777777);
+                }
+            });
+            options[index].setTooltip(Tooltip.create(label(index)));
+        }
+        retireButton = addRenderableWidget(new RetirementButton(120, LinkModifierMenu.RETIRE_AGE, "retire", false));
+        confirmRetireButton = addRenderableWidget(new RetirementButton(140, LinkModifierMenu.CONFIRM_RETIRE_AGE, "confirm", true));
+        refreshControls();
+    }
+    private final class RetirementButton extends Button {
+        private final boolean danger;
+        RetirementButton(int x, int action, String name, boolean danger) {
+            super(leftPos + x, topPos + 32, 18, 18,
+                    Component.translatable("screen.rivencraft.link_modifier." + name), button -> {
+                        if (minecraft != null && minecraft.gameMode != null)
+                            minecraft.gameMode.handleInventoryButtonClick(menu.containerId, action);
+                    }, DEFAULT_NARRATION);
+            this.danger = danger;
+            setTooltip(Tooltip.create(getMessage()));
+        }
+        @Override protected void extractContents(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+            int x = getX(), y = getY();
+            graphics.fill(x, y, x + 18, y + 18, isHoveredOrFocused() ? 0xFFFFFFFF : 0xFFAAAAAA);
+            graphics.fill(x + 2, y + 2, x + 17, y + 17, danger ? 0xFFAA5555
+                    : menu.awaitingRetirementConfirmation() ? 0xFFBBBBBB : 0xFF777777);
+        }
+    }
+    @Override protected void containerTick() { refreshControls(); }
+    private void refreshControls() {
+        ItemStack book = menu.book();
+        // Changing book kinds refreshes immediately; otherwise avoid replacing
+        // focused text with an earlier server echo while the player is typing.
+        if (!ItemStack.isSameItem(book, lastBook) || !titleInput.isFocused()) {
+            if (!ItemStack.isSameItemSameComponents(book, lastBook)) {
+                Component name = book.get(DataComponents.CUSTOM_NAME);
+                refreshing = true;
+                titleInput.setValue(name == null ? "" : name.getString());
+                refreshing = false;
+                lastBook = book.copy();
+            }
+        }
+        titleInput.setEditable(!book.isEmpty());
+        boolean canRetire = minecraft != null && minecraft.player != null && menu.canRetire(minecraft.player);
+        if (retireButton != null) {
+            retireButton.visible = canRetire;
+            retireButton.active = canRetire && !menu.awaitingRetirementConfirmation();
+            confirmRetireButton.visible = canRetire && menu.awaitingRetirementConfirmation();
+            confirmRetireButton.active = confirmRetireButton.visible;
+        }
+        Identifier age = book.get(Rivencraft.AGE_BOOK_ID.get());
+        if (!java.util.Objects.equals(seedAge, age)) {
+            seedInput.setFocused(false);
+            seedAge = age;
+            seedInput.setValue(Long.toString(menu.seed()));
+            lastSeed = menu.seed();
+        }
+        seedInput.visible = menu.hasSeed();
+        seedInput.setEditable(seedInput.visible);
+        if (!seedInput.visible) seedInput.setFocused(false);
+        else if (!seedInput.isFocused() && (lastSeed != menu.seed()
+                || !seedInput.getValue().equals(Long.toString(menu.seed())))) {
+            lastSeed = menu.seed();
+            seedInput.setValue(Long.toString(lastSeed));
+        }
+        for (int i = 0; i < options.length; i++) if (options[i] != null) {
+            options[i].active = available(i);
+            Component label = label(i);
+            if (!options[i].getMessage().equals(label)) {
+                options[i].setMessage(label);
+                options[i].setTooltip(Tooltip.create(label));
+            }
+        }
+    }
+    private boolean available(int index) {
+        return !menu.book().isEmpty() && ((index != 1 && index != 2) || menu.book().is(Rivencraft.LINKING_BOOK.get()));
+    }
+    private Component label(int index) {
+        Component name = Component.translatable("item.rivencraft.link_property." + NAMES[index]);
+        return name.copy().append(selected(index,
+                menu.book().getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE)) ? ": On" : ": Off");
+    }
+    private void submitSeed() {
+        if (seedInput.visible && seedAge != null && !seedInput.getValue().equals(Long.toString(menu.seed())))
+            ClientPacketDistributor.sendToServer(new SetLinkModifierSeedPayload(menu.containerId, seedAge, seedInput.getValue()));
+    }
+    @Override public boolean mouseClicked(MouseButtonEvent event, boolean doubleClick) {
+        if (seedInput.isFocused() && !seedInput.isMouseOver(event.x(), event.y())) {
+            submitSeed();
+            seedInput.setFocused(false);
+        }
+        return super.mouseClicked(event, doubleClick);
+    }
+    @Override public boolean keyPressed(KeyEvent event) {
+        if (seedInput != null && seedInput.isFocused()) {
+            if (event.key() == InputConstants.KEY_RETURN || event.key() == InputConstants.KEY_NUMPADENTER) {
+                submitSeed();
+                seedInput.setFocused(false);
+                setFocused(null);
+                return true;
+            }
+            if (!event.isEscape()) {
+                seedInput.keyPressed(event);
+                return true;
+            }
+        }
+        if (titleInput != null && titleInput.isFocused() && !event.isEscape()) {
+            titleInput.keyPressed(event);
+            return true; // Character input must never activate inventory/hotbar shortcuts.
+        }
+        return super.keyPressed(event);
+    }
+    @Override public void extractBackground(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        super.extractBackground(graphics, mouseX, mouseY, partialTick);
+        graphics.blit(RenderPipelines.GUI_TEXTURED, BACKGROUND, leftPos, topPos, 0, 0, imageWidth, imageHeight, 256, 256);
+    }
+
+    private boolean selected(int index, LinkProperties properties) {
+        if (index != 5) return properties.has(FLAGS[index]);
+        return menu.book().is(Rivencraft.LINKING_BOOK.get()) ? properties.has(LinkProperties.GENERATE_PLATFORM)
+                : !properties.has(LinkProperties.DISABLE_PLATFORM);
+    }
+    @Override protected void extractLabels(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        graphics.text(font, playerInventoryTitle, inventoryLabelX, inventoryLabelY, 0xFF404040, false);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/client/NotebookScreen.java

@@ -0,0 +1,317 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.platform.InputConstants;
+import java.util.Locale;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.menu.NotebookMenu;
+import net.minecraft.client.gui.GuiGraphicsExtractor;
+import net.minecraft.client.input.MouseButtonEvent;
+import net.minecraft.client.input.KeyEvent;
+import net.minecraft.client.renderer.RenderPipelines;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.components.EditBox;
+import net.minecraft.client.gui.screens.inventory.AbstractContainerScreen;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.inventory.ContainerInput;
+import net.minecraft.world.item.ItemStack;
+
+/** A page surface modelled on Legacy's folder GUI, backed by the Notebook menu. */
+public final class NotebookScreen extends AbstractContainerScreen<NotebookMenu> {
+    private static final int SURFACE_TOP = 20;
+    private static final int SURFACE_BOTTOM = 132;
+    private static final int SURFACE_RIGHT = 156;
+    private static final int PAGE_WIDTH = 30;
+    private static final int PAGE_HEIGHT = 40;
+    private static final int PAGE_STEP_X = 31;
+    private static final int PAGE_STEP_Y = 41;
+    private static final int PAGE_COLUMNS = 5;
+    private static final Identifier PAGE_ATLAS = texture("gui/notebook_pages");
+    private EditBox textInput;
+    private boolean draggingScrollbar;
+    private boolean surfaceClickPendingRelease;
+    private int selectedSlot = -1;
+    private int scroll;
+
+    public NotebookScreen(NotebookMenu menu, Inventory inventory, Component title) {
+        super(menu, inventory, title, 176, 213);
+        inventoryLabelY = 123;
+    }
+
+    @Override public boolean isPauseScreen() { return false; }
+
+    @Override
+    protected void init() {
+        super.init();
+        Button sortButton = Button.builder(Component.literal("AZ"), button -> {})
+                .bounds(leftPos, topPos, 18, 18).build();
+        Button allButton = Button.builder(Component.literal("ALL"), button -> {})
+                .bounds(leftPos + 20, topPos, 26, 18).build();
+        sortButton.active = false;
+        allButton.active = false;
+        addRenderableWidget(sortButton);
+        addRenderableWidget(allButton);
+        textInput = new EditBox(font, leftPos + 48, topPos, 128, 18,
+                Component.translatable("screen.rivencraft.notebook.search"));
+        textInput.setMaxLength(32);
+        textInput.setHint(Component.translatable("screen.rivencraft.notebook.search"));
+        textInput.setResponder(value -> scroll = 0);
+        addRenderableWidget(textInput);
+    }
+
+    @Override
+    public void extractBackground(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        super.extractBackground(graphics, mouseX, mouseY, partialTick);
+        graphics.fill(leftPos, topPos + SURFACE_TOP, leftPos + SURFACE_RIGHT,
+                topPos + SURFACE_BOTTOM, 0xB0000000);
+        drawBeveledPanel(graphics, leftPos, topPos + 132, imageWidth, 81);
+        for (int row = 0; row < 3; row++) {
+            for (int column = 0; column < 9; column++) drawSlot(graphics, 7 + column * 18, 134 + row * 18);
+        }
+        for (int column = 0; column < 9; column++) drawSlot(graphics, 7 + column * 18, 192);
+    }
+
+    @Override
+    public void extractContents(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        super.extractContents(graphics, mouseX, mouseY, partialTick);
+        int pageSlots = displayedPageSlots();
+        scroll = Math.min(scroll, maxScroll(pageSlots));
+        graphics.nextStratum();
+        graphics.enableScissor(leftPos, topPos + SURFACE_TOP, leftPos + SURFACE_RIGHT, topPos + SURFACE_BOTTOM);
+        for (int index = 0; index < pageSlots; index++) {
+            int x = leftPos + (index % PAGE_COLUMNS) * PAGE_STEP_X;
+            int y = topPos + SURFACE_TOP + (index / PAGE_COLUMNS) * PAGE_STEP_Y - scroll;
+            if (y + PAGE_HEIGHT > topPos + SURFACE_TOP && y < topPos + SURFACE_BOTTOM) drawPage(graphics, index, x, y);
+        }
+        graphics.disableScissor();
+        drawScrollbar(graphics, pageSlots);
+    }
+
+    @Override
+    protected void extractTooltip(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        int hovered = pageAt(mouseX, mouseY);
+        if (hovered >= 0 && menu.getCarried().isEmpty() && !menu.getSlot(hovered).getItem().isEmpty()) {
+            ItemStack page = menu.getSlot(hovered).getItem();
+            if (matchesSearch(page)) graphics.setTooltipForNextFrame(font, page, mouseX, mouseY);
+        } else super.extractTooltip(graphics, mouseX, mouseY);
+    }
+
+    @Override
+    protected void extractSlots(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        // Collection slots are drawn above as large pages. Do not submit up to
+        // 252 additional item models at their off-screen server-slot positions.
+        for (int index = NotebookMenu.NOTEBOOK_SLOTS; index < menu.slots.size(); index++) {
+            var slot = menu.getSlot(index);
+            if (slot.isActive()) extractSlot(graphics, slot, mouseX, mouseY);
+        }
+    }
+
+    @Override
+    protected void extractLabels(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        graphics.text(font, playerInventoryTitle, inventoryLabelX, inventoryLabelY, 0xFF404040, false);
+    }
+
+    @Override
+    public boolean mouseClicked(MouseButtonEvent event, boolean doubleClick) {
+        double mouseX = event.x(), mouseY = event.y();
+        int button = event.button();
+        if (inScrollbar(mouseX, mouseY) && button == InputConstants.MOUSE_BUTTON_LEFT) {
+            draggingScrollbar = true;
+            setScrollFromMouse(mouseY, displayedPageSlots());
+            return true;
+        }
+        int index = pageAt(mouseX, mouseY);
+        if (index >= 0 && (button == InputConstants.MOUSE_BUTTON_LEFT || button == InputConstants.MOUSE_BUTTON_RIGHT)) {
+            ItemStack page = menu.getSlot(index).getItem();
+            if ((!page.isEmpty() && !matchesSearch(page))
+                    || (page.isEmpty() && (!menu.getCarried().is(Rivencraft.PAGE.get())
+                            || PageItem.isLinkPanel(menu.getCarried())))) {
+                return true;
+            }
+            setFocused(null);
+            textInput.setFocused(false);
+            selectedSlot = index;
+            slotClicked(menu.getSlot(index), index, button == InputConstants.MOUSE_BUTTON_RIGHT ? 1 : 0, ContainerInput.PICKUP);
+            surfaceClickPendingRelease = true;
+            return true;
+        }
+        return super.mouseClicked(event, doubleClick);
+    }
+
+    @Override
+    public boolean mouseDragged(MouseButtonEvent event, double dragX, double dragY) {
+        double mouseY = event.y();
+        int button = event.button();
+        if (draggingScrollbar && button == InputConstants.MOUSE_BUTTON_LEFT) {
+            setScrollFromMouse(mouseY, displayedPageSlots());
+            return true;
+        }
+        return super.mouseDragged(event, dragX, dragY);
+    }
+
+    @Override
+    public boolean mouseReleased(MouseButtonEvent event) {
+        if (draggingScrollbar || surfaceClickPendingRelease) {
+            draggingScrollbar = false;
+            surfaceClickPendingRelease = false;
+            return true;
+        }
+        draggingScrollbar = false;
+        return super.mouseReleased(event);
+    }
+
+    @Override
+    public boolean mouseScrolled(double mouseX, double mouseY, double scrollX, double scrollY) {
+        if (inSurface(mouseX, mouseY) || inScrollbar(mouseX, mouseY)) {
+            scroll = Math.clamp(scroll - (int)Math.signum(scrollY) * 20,
+                    0, maxScroll(displayedPageSlots()));
+            return true;
+        }
+        return super.mouseScrolled(mouseX, mouseY, scrollX, scrollY);
+    }
+
+    @Override
+    public boolean keyPressed(KeyEvent event) {
+        // Let the container close normally, including returning its carried
+        // stack, even while the search field owns keyboard focus.
+        if (event.isEscape()) return super.keyPressed(event);
+        if (textInput != null && textInput.isFocused()) {
+            textInput.keyPressed(event);
+            // EditBox does not consume ordinary letter key presses; the matching charTyped
+            // event handles text input. Do not pass them to the container's inventory keys.
+            return true;
+        }
+        if (selectedSlot >= 0 && (event.isLeft() || event.isRight())) {
+            moveSelected(event.isRight());
+            return true;
+        }
+        return super.keyPressed(event);
+    }
+
+    private int displayedPageSlots() {
+        if (menu.getCarried().is(Rivencraft.PAGE.get())) {
+            return menu.pageCapacity();
+        }
+        for (int index = menu.pageCapacity() - 1; index >= 0; index--) {
+            if (!menu.getSlot(index).getItem().isEmpty()) {
+                return index + 1;
+            }
+        }
+        return 0;
+    }
+
+    private boolean matchesSearch(ItemStack page) {
+        return textInput.getValue().isBlank()
+                || page.getHoverName().getString().toLowerCase(Locale.ROOT)
+                        .contains(textInput.getValue().toLowerCase(Locale.ROOT));
+    }
+
+    private int pageAt(double mouseX, double mouseY) {
+        if (!inSurface(mouseX, mouseY)) return -1;
+        int localX = (int)mouseX - leftPos;
+        int localY = (int)mouseY - topPos - SURFACE_TOP + scroll;
+        int column = localX / PAGE_STEP_X;
+        int index = (localY / PAGE_STEP_Y) * PAGE_COLUMNS + column;
+        return column < PAGE_COLUMNS && localX % PAGE_STEP_X < PAGE_WIDTH
+                && localY % PAGE_STEP_Y < PAGE_HEIGHT && index < displayedPageSlots()
+                ? index : -1;
+    }
+
+    private boolean inSurface(double mouseX, double mouseY) {
+        return mouseX >= leftPos && mouseX < leftPos + SURFACE_RIGHT
+                && mouseY >= topPos + SURFACE_TOP && mouseY < topPos + SURFACE_BOTTOM;
+    }
+
+    private boolean inScrollbar(double mouseX, double mouseY) {
+        return mouseX >= leftPos + SURFACE_RIGHT && mouseX < leftPos + imageWidth
+                && mouseY >= topPos + SURFACE_TOP && mouseY < topPos + SURFACE_BOTTOM;
+    }
+
+    private int maxScroll(int pageCount) {
+        int rows = (pageCount + PAGE_COLUMNS - 1) / PAGE_COLUMNS;
+        return Math.max(0, rows * PAGE_STEP_Y - (SURFACE_BOTTOM - SURFACE_TOP));
+    }
+
+    private void setScrollFromMouse(double mouseY, int pageCount) {
+        int maximum = maxScroll(pageCount);
+        double fraction = (mouseY - topPos - SURFACE_TOP - 10.0)
+                / (SURFACE_BOTTOM - SURFACE_TOP - 20.0);
+        scroll = Math.clamp((int)(Math.clamp(fraction, 0.0, 1.0) * maximum), 0, maximum);
+    }
+
+    private void drawScrollbar(GuiGraphicsExtractor graphics, int pageCount) {
+        int x = leftPos + SURFACE_RIGHT;
+        int y = topPos + SURFACE_TOP;
+        int height = SURFACE_BOTTOM - SURFACE_TOP;
+        graphics.fill(x, y, x + 20, y + height, 0xFF858585);
+        graphics.outline(x, y, 20, height, 0xFF262626);
+        for (int line = y + 5; line < y + height - 4; line += 5) {
+            graphics.fill(x + 4, line, x + 16, line + 1, 0xFFB7B7B7);
+        }
+        int maximum = maxScroll(pageCount);
+        int thumbY = y + 4 + (maximum == 0 ? 0 : scroll * (height - 23) / maximum);
+        graphics.fill(x + 4, thumbY, x + 16, thumbY + 15, 0xFFC9C9C9);
+        graphics.outline(x + 4, thumbY, 12, 15, 0xFF414141);
+    }
+
+    private void drawPage(GuiGraphicsExtractor graphics, int index, int x, int y) {
+        ItemStack page = menu.getSlot(index).getItem();
+        boolean dimmed = page.isEmpty() || !matchesSearch(page);
+        // Legacy's Notebook draws the atlas' native 30x40 page, not a stretched item icon.
+        graphics.nextStratum();
+        graphics.blit(RenderPipelines.GUI_TEXTURED, PAGE_ATLAS, x, y, 156, 0, PAGE_WIDTH, PAGE_HEIGHT, 256, 256);
+        if (!page.isEmpty() && page.has(Rivencraft.SYMBOL_PAGE_ID.get())) {
+            graphics.nextStratum();
+            ItemStack glyph = page.copy();
+            glyph.set(Rivencraft.PAGE_GLYPH_ONLY.get(), true);
+            graphics.pose().pushMatrix();
+            graphics.pose().translate(x + 1, y + 6);
+            graphics.pose().scale(1.75F, 1.75F);
+            graphics.fakeItem(glyph, 0, 0);
+            graphics.pose().popMatrix();
+            graphics.nextStratum();
+        }
+        if (dimmed) {
+            graphics.fill(x, y, x + PAGE_WIDTH, y + PAGE_HEIGHT, 0xB8000000);
+        } else if (!net.dnorberg.rivencraft.writing.PortAuthoredWriting.isPageImplemented(
+                page.get(Rivencraft.SYMBOL_PAGE_ID.get()))) {
+            graphics.fill(x, y, x + PAGE_WIDTH, y + PAGE_HEIGHT, 0x55FF3333);
+        }
+        if (index == selectedSlot && !page.isEmpty()) {
+            graphics.outline(x, y, PAGE_WIDTH, PAGE_HEIGHT, 0xFFFFD061);
+        }
+    }
+
+    private static Identifier texture(String path) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "textures/" + path + ".png");
+    }
+
+    private void moveSelected(boolean next) {
+        int target = selectedSlot + (next ? 1 : -1);
+        if (selectedSlot < 0 || target < 0 || target >= NotebookMenu.NOTEBOOK_SLOTS
+                || menu.getSlot(selectedSlot).getItem().isEmpty()) return;
+        int buttonId = (next ? NotebookMenu.MOVE_NEXT_BASE : NotebookMenu.MOVE_PREVIOUS_BASE) + selectedSlot;
+        if (menu.clickMenuButton(minecraft.player, buttonId)) {
+            minecraft.gameMode.handleInventoryButtonClick(menu.containerId, buttonId);
+            selectedSlot = target;
+        }
+    }
+
+    private static void drawBeveledPanel(GuiGraphicsExtractor graphics, int x, int y, int width, int height) {
+        graphics.fill(x, y, x + width, y + height, 0xFFC6C6C6);
+        graphics.fill(x, y, x + width, y + 2, 0xFFFFFFFF);
+        graphics.fill(x, y, x + 2, y + height, 0xFFFFFFFF);
+        graphics.fill(x, y + height - 2, x + width, y + height, 0xFF555555);
+        graphics.fill(x + width - 2, y, x + width, y + height, 0xFF555555);
+    }
+
+    private void drawSlot(GuiGraphicsExtractor graphics, int x, int y) {
+        graphics.fill(leftPos + x, topPos + y, leftPos + x + 18, topPos + y + 18, 0xFF8B8B8B);
+        graphics.fill(leftPos + x, topPos + y, leftPos + x + 18, topPos + y + 1, 0xFF373737);
+        graphics.fill(leftPos + x, topPos + y, leftPos + x + 1, topPos + y + 18, 0xFF373737);
+        graphics.fill(leftPos + x + 17, topPos + y, leftPos + x + 18, topPos + y + 18, 0xFFFFFFFF);
+        graphics.fill(leftPos + x, topPos + y + 17, leftPos + x + 18, topPos + y + 18, 0xFFFFFFFF);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/client/PortBookBinderClientEvents.java

@@ -18,12 +18,34 @@ public final class PortBookBinderClientEvents {
     public static void registerBlockEntityRenderers(
             net.neoforged.neoforge.client.event.EntityRenderersEvent.RegisterRenderers event) {
         event.registerBlockEntityRenderer(Rivencraft.STAR_FISSURE_BLOCK_ENTITY.get(), context -> new StarFissureRenderer());
+        event.registerEntityRenderer(Rivencraft.DROPPED_BOOK.get(), DroppedBookRenderer::new);
+        event.registerBlockEntityRenderer(Rivencraft.WRITING_DESK_BLOCK_ENTITY.get(), WritingDeskRenderer::new);
+        event.registerBlockEntityRenderer(Rivencraft.BOOK_STAND_BLOCK_ENTITY.get(), BookStandRenderer::new);
+        event.registerBlockEntityRenderer(Rivencraft.BOOK_RECEPTACLE_BLOCK_ENTITY.get(), BookReceptacleRenderer::new);
+    }
+
+    @SubscribeEvent
+    public static void portalTint(net.neoforged.neoforge.client.event.RegisterColorHandlersEvent.BlockTintSources event) {
+        event.register(java.util.List.of(new net.minecraft.client.color.block.BlockTintSource() {
+            @Override public int color(net.minecraft.world.level.block.state.BlockState state) { return 0xffffffff; }
+            @Override public int colorInWorld(net.minecraft.world.level.block.state.BlockState state,
+                    net.minecraft.client.renderer.block.BlockAndTintGetter level, net.minecraft.core.BlockPos pos) {
+                if (level.getBlockEntity(pos) instanceof net.dnorberg.rivencraft.block.entity.CrystalPortalBlockEntity portal
+                        && portal.receptacle() != null
+                        && level.getBlockEntity(portal.receptacle()) instanceof net.dnorberg.rivencraft.block.entity.BookReceptacleBlockEntity holder)
+                    return 0xff000000 | holder.skyColor();
+                return 0xffffffff;
+            }
+        }), Rivencraft.CRYSTAL_PORTAL.get());
     }
 
     @SubscribeEvent
     public static void registerScreens(RegisterMenuScreensEvent event) {
         event.register(Rivencraft.BOOK_BINDER_MENU.get(), PortBookBinderScreen::new);
         event.register(Rivencraft.INK_MIXER_MENU.get(), InkMixerScreen::new);
+        event.register(Rivencraft.LINK_MODIFIER_MENU.get(), LinkModifierScreen::new);
+        event.register(Rivencraft.NOTEBOOK_MENU.get(), NotebookScreen::new);
+        event.register(Rivencraft.WRITING_DESK_MENU.get(), WritingDeskScreen::new);
     }
 
     @SubscribeEvent