Port collections, dropped books, return links and Writing Desk to 26.3

README.md

@@ -20,7 +20,7 @@ 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).
+[latest beta release notes](ports/mc263/RELEASE_NOTES_1.0.1.106-beta.1.md).
 Keep the builds and their saves separate, and back up worlds before updating.
 
 ## Getting started

docs/MINECRAFT_26_3_PORT.md

@@ -10,6 +10,77 @@ tracks issues #97–#103 under parent #96.
 
 ## Version boundary
 
+Local slice `1.0.1.106-beta.1` ports the Writing Desk's two-part block,
+88-tab inventory, authoritative catalog sync, copying transactions and 1.21.1
+GUI/model assets. Vial exchange reuses the existing shared helper; symbol copy
+cost defaults to one. Modern Container removal handles content drops while
+the block cleans up its partner. The renderer uses extracted item states.
+Current input helpers also correct Notebook right-click/scrollbar behavior.
+Page content is a derived view of the existing port components; no saved Page
+schema is replaced. Progression awards and optional JEI integration remain
+pending. Client appearance/input/catalog acceptance remains required.
+
+Local slice `1.0.1.105-beta.1` ports category Symbol Portfolios and Sealed
+Notebooks, reusing item textures/models and collection menu/import behavior.
+Portfolio volumes split at 252 pages. Sealed items use 1.21.1's 16-page draw
+and candidate exclusions, with Survival consumption, Creative retention and
+full-inventory drop fallback. No recipes are invented; discovery/library loot
+and JEI integration remain later work. Unported effects are still marked red.
+
+Local slice `1.0.1.104-beta.1` ports 1.21.1's all-or-nothing collection import
+to the current Binder menu: shift-click appends and cursor strip-click inserts
+before a page. Occupied page order is preserved, gaps are compacted and the
+empty collection is returned. Capacity/panel conflicts are checked before any
+mutation. This connects the newly ported collections to actual book assembly;
+the dedicated stored-collection input/UI remains later parity work.
+
+Local follow-up `1.0.1.103-beta.1` corrects old GLFW key literals retained in
+the Notebook screen. Escape always reaches the normal container close path,
+including focused search, and page-movement arrows use 26.3 key helpers.
+The player reported the search-focused GUI could not be escaped in .102;
+client keyboard acceptance must be repeated with .103.
+
+Local slice `1.0.1.102-beta.1` ports Notebook/Collation Folder storage, menu,
+Creative entries, Notebook crafting and the existing sparse page editor.
+The 1.21.1 capacities (252/27), Link Panel insertion rejection, held-item
+locking and search keyboard handling are preserved. The GUI uses 26.3 input
+events/extraction and the existing glyph-only item pipeline, while retaining
+the original page atlas proportions. Discovery, sealed notebooks, portfolios,
+Writing Desk and bulk Binder collection use remain unfinished.
+
+Local slice `1.0.1.101-beta.1` ports dropped-book entities, their open-book
+renderer/textures, decay/weather damage and persistent components. Handheld
+travel detaches only the active book and leaves it at departure after success;
+failed travel or a cancelled entity spawn restores it. Shared handling covers
+both book types and hands and keeps Return Link issuance after departure-book
+handling. The newer render-state-based pickup path replaces the old copy()
+workaround. Client rendering/pickup remain part of in-game validation.
+
+Local slice `1.0.1.100-beta.1` ports automatic Return Link policy from 1.21.1
+for handheld Descriptive Books, default DISABLED. ON_CREATION uses a persistent
+world-wide per-Age marker; ALWAYS issues on each successful arrival. Exact
+departure position/facing is captured before teleportation and issuance occurs
+after Disarm, with inventory-full fallback to a destination item drop. Ordinary
+Linking Books, failures and operator travel do not issue books. Stand/portal
+integration remains pending with those systems.
+
+Local slice `1.0.1.99-beta.1` ports the dedicated non-collectible arrival
+platform block from 1.21.1, reusing its opaque crystal model and strength 0.3.
+Fallback landings use it instead of collectible Crystal Blocks. No item,
+loot, pick-block result, or material Page is available. Existing platforms
+and the port's landing-search/footprint policy are unchanged.
+
+Local slice `1.0.1.98-beta.1` ports the 1.21.1 Accelerated environment page:
+stacking extra random block ticks in already-loaded player-nearby chunks,
+eight-chunk/16,384-attempt default budgets, fair rotating section allocation,
+and an Age-local saved page count. The 26.3 LOCAL config holds these limits.
+Entities, machines and scheduled ticks are unaffected. Existing Ages remain
+unaccelerated; random Age inclusion and instability scoring are not added.
+The suspected host-seed biome zoom mismatch was checked against NeoForge's
+patched ServerLevel constructor: seedOverride already replaces it correctly,
+so the backend seed path was left unchanged. Native Cave policy issue #111
+remains separate future work for both Minecraft tracks.
+
 Minecraft 26.3/NeoForge uses Java 25, while Rivencraft 1.21.1 uses Java 21.
 Build and publish separate artifacts; do not widen the Minecraft dependency
 range of the 1.21.1 JAR. The official [26.3 release notes](https://www.minecraft.net/en-us/article/minecraft-java-edition-26-3),
@@ -1801,6 +1872,144 @@ fresh chunks after full restart again used Nylium/End Stone. No full feature
 or entity chunk scans were run. The server was stopped and temporary world
 deleted. Nothing was committed, pushed or published.
 
+## Structure-aware biome completion
+
+`1.0.1.94-beta.1` adapts root `AgeBiomeSelection.completeStructureBiomes` for
+explicit non-Native biome controllers. It reads compatible biome IDs from
+the active registered structure sets and shares this lookup with random
+structure eligibility, avoiding two different compatibility definitions.
+Repeated structure pages produce one requirement; Dungeons are excluded.
+Single with no supplied biome chooses from the intersection of all structure
+requirements and terrain-eligible biomes. No intersection leaves ordinary
+seeded filling intact. An explicit Single biome is never rewritten.
+
+Multi-biome completion adds one seeded compatible biome for each unmet
+requirement where a terrain-eligible candidate exists, before ordinary minimum
+filling. Root's salts, requirement order and shuffled candidate selection are
+preserved. Existing biome order and duplicate weights remain, but a structure
+can intentionally extend a pool beyond the usual minimum. Native and the
+port's no-controller fallback remain unchanged. Impossible requirements do
+not become new writing rejections: authored structure overrides still apply.
+No saved format, network protocol or generated chunks are changed.
+
+The completed-biome fixture accepts an optional structure page and checks
+32 seeds for compatible Single/Cave Fortress choices, common Village/Stronghold
+requirements, explicit End Single precedence, Native behavior, multi-biome
+prefix preservation and avoiding unnecessary additions for already-compatible
+or repeated structure pages. Existing biome plan codec checks remain in place.
+
+The .94 build and disposable server checks passed. Village Single and Tiny
+fixtures included compatible Plains; Cave Fortress Single selected Crimson
+Forest. The 32-seed authoring assertions and the preexisting no-structure
+completion checks passed. Saved generator pools survived unload/reload,
+terrain reseed and full restart. The server was stopped and its temporary
+world deleted. No structure-placement chunk scan was needed. Client book
+authoring remains a manual check; no commit, push or publication occurred.
+
+## Omitted biome-controller completion
+
+`1.0.1.95-beta.1` ports the no-controller branch of root `AgeBiomeSelection`
+and the first `AgeTraits.select` draw. The rank table and seed stream are
+shared with `PortRandomAgeSelection` rather than duplicated. The production
+seeded biome compiler uses that default when there is no explicit controller;
+the registry-only diagnostic overload retains its exact older defaults.
+Explicit controllers are unchanged. Native rolls with authored biomes, or
+Single rolls with more than one biome page, fall back by authored count to
+Single/Tiled/Medium. Other multi-biome rolls retain their distribution and
+ordinary minimum-only filling, plus .94's structure requirements.
+
+Void's omitted controller remains Single for empty pools and count-based
+for supplied biome pages. Cave's omitted Native roll follows the port's
+existing page-free seeded Single workaround; a native multi-cave source is
+still not implemented. Explicit Native is not silently converted. No other
+terrain, weather, lighting, color or body seed stream changes. Saved plans
+remain frozen through restart and terrain reseed; old Ages are not rewritten.
+
+The completed-biome diagnostic accepts `auto` and checks 128 seeds for all
+nine distribution results, independence from unrelated weather pages,
+authored prefix preservation, one/two-biome fallbacks, Void behavior and
+structure-aware completion. Existing explicit-controller checks still run.
+
+The .95 build and disposable-server checks passed. The expanded 128-seed
+matrix covered all distributions, authored one/two-biome rules and Cave pools.
+Created automatic Standard, Cave, Void and Cave Fortress fixtures, plus the
+unchanged full-random command and explicit Single/Native Cave controls.
+Generator pools survived unload/reload, reseed and full restart. A second seed
+produced Small regions with three biomes, while explicit Native Cave retained
+its Lush Caves source. No chunk-generation scan was needed. The server was
+stopped and its temporary world deleted. Client authoring remains a manual
+check; nothing was committed, pushed or published.
+
+## Omitted terrain completion
+
+`1.0.1.96-beta.1` adapts root `AgeRuntimeProfiles.selectForWriting`. A partly
+authored book without terrain starts with the shared ranked terrain draw;
+if unsupported, compatible profiles in stable ID order are indexed using
+`floorMod(Long.hashCode(seed), count)`. Explicit terrain is never substituted.
+Unlike root's feature-only candidate test, the port additionally preflights
+registry-backed biome restrictions to avoid selecting an unloadable Cave
+combination for supplied surface biomes. This is a deliberate compatibility
+guard while the broader writing/instability recovery remains unported.
+
+Binder availability checks now consider whether any supported terrain can
+host an omitted-terrain book instead of assuming Standard. The server resolves
+the actual terrain and biome plan once, then passes the resolved internal page
+view to material/feature compilers. The inferred terrain is appended internally,
+not inserted before original pages or written back to the book. Original
+indices and ordered modifiers remain intact. Environment controllers use the
+selected terrain, while sky colors and celestials still compile from original
+pages. Page-free random books retain their original path and seed streams.
+The chosen terrain and generator plans use existing saved fields, so no
+network protocol change or retroactive terrain reroll is introduced.
+
+The fixture checks 64 seeds for terrain coverage, deterministic selection,
+original page prefixes, Cave-only Fortress support, implied-fluid constraints,
+surface-biome compatibility, explicit terrain precedence and Binder
+availability. Generator placement still uses the previously ported routines.
+
+The .96 build and disposable server checks passed. The 64-seed assertions
+covered all six terrains, deterministic fallback, page-prefix preservation,
+explicit Flat, surface-biome protection and Cave-only Fortress availability.
+Created Sky-only, Fortress-only, Water-only, Plains-only, explicit Flat and
+full-random fixtures. A Water page retained Water as its implied lake fluid;
+Fortress-only selected Cave with eligible biomes. Plans survived unload/reload,
+reseed and full restart. The server was stopped and its temporary world
+deleted. No chunk scan was needed; client Binder checks remain manual.
+Nothing was committed, pushed or published.
+
+## Native Cave regions
+
+`1.0.1.97-beta.1` ports root `AgeBiomeSelection`'s full Native Cave pool and
+`AgeDimensionService.createBiomeSource`'s Native-to-Tiny mapping. New Native
+Cave plans retain distribution NATIVE with a saved recognized Cave/Nether
+list, and the backend uses `PortScaledBiomeSource` at scale 0 (or Fixed for
+a one-biome pool). Explicit Native biome pages remain prohibited. Both authored
+and page-free/omitted-controller paths use the same eligibility query; the
+temporary Native-to-Single Cave conversions are removed.
+
+Native pool data is permitted only for Cave terrain at backend validation.
+Other Native terrain sources are unchanged. Empty older Native Cave records
+still load the old Lush source; old Single choices also remain frozen. New
+Native pools are saved through the existing biome-plan codec without a new
+network protocol, but earlier betas cannot decode populated Native pools, so
+downgrading those saves is not supported. The current pool is passed to random
+structure eligibility rather than incorrectly assuming Lush Caves.
+
+The fixture verifies registry-derived pool ordering, old empty Native codec
+defaults, the actual generator source, deterministic Tiny-region equivalence,
+horizontal region variation and sampled pool membership without loading
+chunks. The omitted-controller matrix now expects Native Cave to remain
+Native with its full pool. This does not implement modded surface rules.
+
+The .97 build and disposable-server checks passed: explicit and omitted
+Native Cave, the full-random Native Cave path (seed 114), Native + Fortresses,
+explicit Single and the legacy Lush-only control. The vanilla registry pool
+contained nine biomes, including Sulfur Caves and all five Nether biomes;
+the actual Native source passed Tiny-equivalence and sample-membership checks.
+Pools survived unload/reload, reseed and full restart. The server was stopped
+and its temporary world deleted. No chunk scan was needed. Client exploration
+remains a manual check; nothing was committed, pushed or published.
+
 ## Verification of this first slice
 
 The 1.21.1 `compileJava` and `build` tasks passed offline after the backend

ports/mc263/README.md

@@ -2,14 +2,15 @@
 
 This is an **experimental beta port** for issues #97–#104, not gameplay parity
 with the Minecraft 1.21.1 release. The 26.3 backend persists separate Ages and
-their seeds. Books, the Book Binder, and the Ink Mixer work, and the Binder can
+their seeds. Books, the Book Binder, Ink Mixer, Writing Desk and page collections
+are ported, and the Binder can
 author Standard, Amplified, Island, Flat, Void, or Cave terrain with supported
 biome-distribution pages, selected material/vegetation/structure features, and
 independent Age weather and lighting, multiple authored or seeded celestial
 bodies and eclipses, biome/material completion, and random features/structures.
-Instability, crystal portals, discovery/stations, writing recovery and optional
+Instability, crystal portals, remaining discovery/stations, writing recovery and optional
 integration parity remain unfinished. The latest published beta is
-[1.0.1.93-beta.1](RELEASE_NOTES_1.0.1.93-beta.1.md).
+[1.0.1.106-beta.1](RELEASE_NOTES_1.0.1.106-beta.1.md).
 Use a test world and keep a backup; do not
 substitute this JAR for the 1.21.1 mod or import 1.21.1 saves.
 
@@ -1291,6 +1292,360 @@ and `age material_probe <name> [chunk_x chunk_z]`. The latter examines one
 terrain-stage chunk (default 0,0) without feature, lighting or entity generation. Nothing is committed
 or published without explicit request.
 
+The local `1.0.1.94-beta.1` slice ports **structure-aware completion of explicit
+biome distributions** from 1.21.1. Single Biome without a supplied biome now
+prefers a biome compatible with every authored structure page, when a common
+candidate exists. Cave + Single + Nether Fortresses therefore selects an
+eligible Cave/Nether biome rather than an unrelated cave biome. If there is
+no common candidate, ordinary seeded filling and authored structure overrides
+remain available, as in root.
+
+For multi-biome controllers, each uncovered structure requirement can add one
+compatible biome from the terrain's available pool. This is an intentional
+exception to ordinary minimum-only filling: an already-full pool may gain
+another biome for its structure pages. Supplied biomes, their order and
+duplicate weights remain intact. A supplied Single Biome is never replaced,
+Native remains unchanged, and Dungeons impose no biome requirement. The
+no-controller fallback remains unchanged in this slice.
+
+Test Single Biome + Villages without biome pages, Cave + Single Biome + Nether
+Fortresses, and a multi-biome book with structures. Compare an explicit End
+Single Biome + Villages to confirm that authored override still works.
+`age create_completed_biomes <name> <seed> <terrain> <distribution> [structure-page-id]`
+now accepts an optional structure fixture. Existing Ages are not rerolled;
+restart/reseed retains completed pools. Nothing is committed or published
+without explicit request.
+
+The local `1.0.1.95-beta.1` slice seed-completes **omitted biome controllers**
+in partly authored books, using 1.21.1's first AgeTraits distribution draw.
+Native, Single and Medium are common; the other supported distributions are
+rarer. Explicit controllers still win. Supplied biomes are never discarded:
+a Native roll with authored biomes falls back by count, as does a Single roll
+with multiple biome pages. Other seeded multi-biome controllers are retained,
+so a lone supplied biome may receive a second biome to meet the minimum.
+
+Void without biome pages still uses The Void; supplied Void biome pages keep
+their existing count-based behavior. An omitted controller that rolls Native
+on Cave terrain uses the same seeded Single fallback already used by random
+Ages, since the port has no native multi-cave source. Explicit Native Cave
+behavior remains unchanged. Structure-aware completion from .94 applies to
+the resulting nonnative controller. Full Link-Panel-only random generation
+retains its existing selector and seeds.
+
+Test new terrain-only books without biome controllers, one/two supplied biome
+pages without a controller, and Cave + Nether Fortresses without a biome
+controller. Compare an explicit Single Biome book and restart/revisit.
+`age create_completed_biomes <name> <seed> <terrain> auto [structure-page-id]`
+provides an omitted-controller fixture. Existing Ages are not rerolled.
+Nothing is committed or published without explicit request.
+
+The local `1.0.1.96-beta.1` slice seed-completes **omitted terrain pages** in
+partly authored books. It starts with the same ranked terrain draw as random
+Ages, following 1.21.1's `selectForWriting` model. If that terrain cannot host
+the supplied features/materials, a deterministic fallback chooses a compatible
+terrain in stable profile order. The port also preflights its current biome
+restrictions, avoiding an automatic Cave choice for supplied surface biomes.
+
+Explicit terrain still wins and incompatible explicit combinations remain
+rejected. Missing-terrain Fortress books can now bind using Cave terrain;
+unpaired fluids use supported surface noise terrain. No extra random features
+are added to partly authored books. The original book page list stays intact;
+the chosen terrain is appended only to internal generation input so material
+and color/controller indices do not shift. Sky/color/celestial compilation
+still reads the original pages. Fully random Link-Panel-only Ages retain their
+existing selector. Already-created Ages do not change terrain.
+
+Test several new books with Sky or a feature but no terrain page, Nether
+Fortresses alone, and an unpaired Water page. Compare an explicit Flat book
+and a Plains biome page without terrain; the latter must not choose Cave.
+`age create_auto_terrain <name> <seed> <page-id>` exercises the production
+selector for one-page fixtures. Restart and revisit to confirm persistence.
+Nothing is committed or published without explicit request.
+
+The local `1.0.1.97-beta.1` slice ports **Native Cave biome distribution** from
+1.21.1. A new Cave + Native book now freezes the full recognized Cave/Nether
+biome pool and distributes it with the existing seeded Tiny-region sampler,
+instead of forcing Lush Caves. An omitted controller or random Cave Age that
+rolls Native now uses that same pool rather than converting to Single.
+Random structures inspect the saved pool, so eligible Nether structures are
+no longer hidden behind an assumed Lush-only source.
+
+Existing Single Cave Ages remain Single. Old empty Native Cave records keep
+their Lush fallback; they are not silently expanded on load. Other Native
+terrains remain unchanged, and explicit Native still rejects biome pages.
+Pools persist across restart/reseed; reseeding can still change future region
+layout. Modded biome surface-rule integration remains separate pending work.
+Back up before updating and do not downgrade worlds containing new Native
+Cave pools to earlier beta builds.
+
+Test a **new** Cave + Native Biomes book without individual biome pages,
+explore multiple regions, then restart/revisit. Compare an explicit Single
+Cave book and an existing old Cave Age. The existing
+`age create_completed_biomes <name> <seed> cave native` fixture also checks
+the native source against Tiny's sampler without generating chunks.
+Nothing is committed or published without explicit request.
+
+### Accelerated random block ticks
+
+The local `1.0.1.98-beta.1` slice ports the **Accelerated** environment page
+from 1.21.1. Repeated pages stack: each adds three extra random positions per
+eligible block section per tick. Only already-loaded chunks within one chunk
+of players are candidates; no extra chunks are loaded. Defaults match 1.21.1:
+at most eight candidate chunks and 16,384 attempted positions per Age tick,
+shared across sections with rotating selection. These limits live in
+`config/rivencraft-local.toml` under `accelerated_age`; setting
+`max_random_tick_attempts_per_tick` to zero disables the extra ticks.
+
+This affects random-ticking blocks such as crops and saplings, not entities,
+machines, scheduled block ticks, or the day/night clock. The authored page
+count persists with the Age across unload/reload, reseeding and restart.
+Existing Ages default to zero; pageless random Ages do not gain Accelerated
+automatically. Instability costs remain part of the pending instability port.
+
+Test two otherwise comparable new Ages, one with a single Accelerated page
+and one with repeated pages. Plant crops/saplings with suitable light and
+space, remain nearby, and compare growth. Revisit after restart. The operator
+command `/rivencraft_port age acceleration <name>` reports the saved count
+and current budgets. Disposable-server fixture
+`age create_accelerated <name> <seed> <pages>` checks authoring and bounded
+attempt arithmetic and creates a Flat Age; it does not prove live growth.
+Build and disposable dedicated-server checks passed for counts 0, 1 and 32,
+overflow/disabled budget arithmetic, unload/reload, reseed and full restart.
+No player was connected for the server checks, so live growth remains an
+in-game acceptance check. The test server was stopped and its world removed.
+
+### Non-collectible arrival platforms
+
+The local `1.0.1.99-beta.1` slice ports 1.21.1's dedicated `cloud_platform`
+block for fallback Age landings. It reuses the existing opaque Crystal Block
+texture, has glass-like breaking strength (0.3), and produces no loot or
+pick-block item. It has no item, recipe, Creative entry or generated material
+Page. Ordinary Crystal Blocks retain their normal behavior.
+
+New fallback platforms use this block. Existing platforms made from ordinary
+Crystal Blocks are not rewritten. This slice changes the fallback material;
+the port's existing landing search and 3-by-3 fallback footprint remain.
+
+Test a new Void Age: arrive on the platform, check its appearance and footing,
+then break a block in Survival and confirm there is no drop. Creative
+pick-block must not supply an item. Compare a normal Crystal Block, and revisit
+the platform after restart. Operator fixtures
+`/rivencraft_port age create_platform <name> <seed>` and
+`/rivencraft_port age platform_probe <name>` validate a disposable Void
+platform's properties and saved blocks.
+The build and disposable dedicated-server checks passed for actual Void
+arrival generation, collision/opacity, strength, loot, pick-block exclusion,
+material-page exclusion, unload/reload and full restart. Shared model assets
+were verified in the JAR. The test server was stopped and its world removed;
+client appearance and Survival breaking remain the in-game check.
+
+### Configurable automatic Return Links
+
+The local `1.0.1.100-beta.1` slice ports the 1.21.1 automatic Return Link
+policy for successful handheld Descriptive Book arrivals. In
+`config/rivencraft-local.toml`, set `[descriptive_books] return_link_mode` to
+`DISABLED` (the default), `ON_CREATION`, or `ALWAYS`. ON_CREATION issues one
+Return Link when the Age is first reached with that mode enabled, shared
+across players in the world. ALWAYS issues one on each successful arrival.
+Disabled/Always arrivals do not consume the ON_CREATION marker, matching
+1.21.1. The marker persists across reload, reseeding and restart.
+
+Return Links retain the exact departure dimension, position, yaw and pitch.
+They use ordinary Linking Book rules and have no automatic Link Panel
+modifiers. They are issued after Disarm and dropped at the destination if
+inventory space is unavailable. Failed travel, binding a book, ordinary
+Linking Book travel and operator teleport probes do not issue Return Links.
+Stands/portals remain pending and will need the same successful-travel hook.
+
+For the in-game check, confirm the default gives no Return Link. Then enable
+ON_CREATION and visit a fresh Age twice: only the first arrival should grant
+one. Use that book to return and check position/facing; restart and revisit
+to confirm no duplicate. In ALWAYS, each arrival should grant a book. Test
+a Disarm Descriptive Book and a full inventory as well. Restore DISABLED
+after testing if automatic Return Links are unwanted.
+The build and disposable-server fixtures passed mode decisions, book target
+components, visit-record codec round trips, world persistence through
+unload/reload, reseeding and restart, and config loading with DISABLED and
+ON_CREATION. No player joined those fixtures; actual travel, Disarm and
+inventory-full delivery remain the in-game acceptance check. The server was
+stopped and its test world removed.
+
+### Handheld books left at departure
+
+The local `1.0.1.101-beta.1` slice ports the 1.21.1 dropped-book entity and
+handheld travel ownership. Successful handheld Linking and Descriptive Book
+travel removes the active book from its hand and leaves it at departure as
+an open-book entity. The existing Linking/Descriptive entity textures and
+skyward-facing model orientation are reused with 26.3's render-state API.
+The other hand and ordinary inventory remain unchanged unless Disarm applies.
+
+Failed travel restores the book. A rejected dropped-entity spawn also restores
+it instead of consuming it. Return Links are issued after the active book is
+left behind. Dropped books have a one-second pickup delay, no ordinary five-
+minute expiry, slow damage every 10,000 loaded ticks, and water/rain damage,
+matching 1.21.1. Book components and the decay counter persist with the entity.
+26.3 pickup particles use the extracted entity render state; 1.21.1's custom
+`ItemEntity.copy()` workaround is not needed on this target.
+
+Test travel from both hands with each book type, return to recover the open
+book, verify pages face upward, and check pickup animation and restart.
+Attempt a blocked/invalid link and confirm the book stays in hand. With
+Disarm, the active book should use its model while other items drop normally.
+With automatic Return Links enabled, the new Return Link should arrive with
+the player. Test rain/water damage with disposable books only.
+
+Build and disposable dedicated-server checks passed both hands, failed travel,
+exception recovery, cancelled entity spawning, successful hand removal, saved
+book components/lifetime, and a full restart with both book entities restored.
+The fixture uses a fake player and does not prove client rendering or actual
+cross-dimension travel. Entity loading is asynchronous: querying in the same
+command batch as chunk loading can briefly see zero books. The server was
+stopped and its world removed after validation. Operator fixtures are
+`age create_dropped_fixture <name> <seed>` and `age dropped_probe <name>`.
+
+### Notebook and Collation Folder
+
+The local `1.0.1.102-beta.1` slice adapts the 1.21.1 Notebook and Collation
+Folder, their server menu, persistent page component and existing page editor.
+Notebook capacity is 252 positions; Folder capacity is 27. Sparse positions,
+dark empty pages through the last occupied position, search, scrolling,
+single-page movement, shift transfers and the held-item lock are retained.
+Search consumes inventory keys while focused. Large pages keep the native
+30-by-40 atlas proportions and use the existing glyph-only item renderer.
+Unsupported symbol pages receive the port's red tint and retain their items.
+
+Both collections appear in Creative. Notebook crafting reuses the 1.21.1
+leather/string pattern. The Folder has no recipe in 1.21.1 and receives none
+here; discovery/library loot is still pending. Link Panels cannot be inserted
+through the collection menu. Unknown symbol pages remain stored and are
+counted in the tooltip. Writing Desk integration, sealed notebooks, Symbol
+Portfolios and bulk Binder interactions remain later work.
+
+Test both collection types and hands. Insert and remove pages by normal and
+shift clicks, place a page near the final position, move it with left/right
+arrows after selection, scroll/search, and type E in the search field. Verify
+Link Panels are rejected and the held collection cannot be moved/swapped.
+Close/reopen, put the collection in a chest, restart and recover its contents.
+Compare large glyphs and page outlines with the 1.21.1 editor.
+Build and disposable-server checks passed both hands and capacities, sparse
+positions, page movement, shift transfers through the actual menu input path,
+Link Panel/non-Page rejection, held-item pickup locking, save/network codec
+round trips, and all four collections stored in a chest across full restart.
+The recipe and adapted recipe-unlock advancement loaded successfully. Shared
+assets were checked in the JAR. No client joined these fixtures, so appearance,
+mouse handling and search keys still need the in-game check. The test server
+was stopped and every disposable test world removed.
+
+The local `1.0.1.103-beta.1` follow-up fixes the Notebook/Folder keyboard port:
+26.3 uses different key values from the old GLFW-based implementation. Escape
+now delegates to normal container closing even with search focused, while
+left/right page movement uses the current key helpers. Search still consumes
+ordinary inventory/hotbar keys. Check Escape with search focused and while
+holding a page on the cursor; closing should use normal carried-item recovery.
+
+### Collection imports in the Book Binder
+
+The local `1.0.1.104-beta.1` slice adapts 1.21.1's transactional collection
+import. Shift-click a Notebook or Collation Folder in the Binder inventory
+to append its pages. Carry one on the cursor and click the page strip to
+insert its pages before that position; clicking the panel position inserts
+at the beginning. Empty collection positions are skipped, preserving the
+relative order of occupied pages. Later Binder pages shift to make room.
+
+The import validates every page and total capacity before changing anything.
+A full Binder, invalid insertion point, empty collection, or conflicting
+Link Panel rejects the transaction without consuming pages. Successful
+imports leave the empty collection on the cursor or in its inventory slot,
+retaining its other components. Ordinary collection menus still reject Link
+Panels; the Binder retains 1.21.1's handling for explicitly supplied collection
+data containing a panel. Dedicated stored-collection input/UI remains unported.
+
+Test shift-click append and cursor insertion for both collection types, using
+distinct ordered pages and gaps. Check that the collection empties only after
+success and that rejected imports leave both sides unchanged. Bind a book
+with the imported pages, inspect its symbols, and restart with pages in the
+Binder and collections in a chest to check persistence.
+Build and disposable-server checks passed full-capacity and panel-conflict
+rejection, invalid positions, sparse cursor insertion, shift append, empty-cover
+retention, real Binder assembly and book page order. The empty collections and
+finished book survived full restart in a chest. No client joined this fixture;
+cursor/shift UI interaction remains the in-game check. The server was stopped
+and its world removed. Include collection imports in the future JEI guide port.
+
+### Symbol Portfolios and Sealed Notebooks
+
+The local `1.0.1.105-beta.1` slice ports the remaining collection items from
+1.21.1. The main Creative tab offers prefilled Symbol Portfolios for every
+symbol-page category, including registered biome/material/fluid pages.
+Categories exceeding 252 pages split into named volumes without truncation.
+Portfolios use the Notebook editor and Binder collection import and can be
+emptied/refilled like ordinary collections. No portfolio recipe is added.
+
+A Sealed Notebook opens server-side into a Collation Folder with 16 random
+pages. As in 1.21.1, the candidate pool excludes IDs under `block/` and
+`biome/` and the corrupted category; repeated draws are allowed. This also
+excludes biome-controller IDs under `biome/`, matching the existing code.
+The pool is not restricted to already-ported effects, so unsupported pages
+retain their red tint. Survival consumes one sealed item; Creative retains
+it. The last item becomes the Folder in hand, otherwise the Folder goes into
+inventory or drops if there is no space. Sealed Notebooks appear in Creative;
+their discovery/library loot remains pending, and no crafting recipe is added.
+
+Test portfolio names, volumes, contents, editor and Binder import. Open sealed
+stacks from both hands in Survival, including with full inventory, and confirm
+each Folder has 16 pages. Check Creative retains the sealed item. Put the
+resulting items in a chest, restart and revisit.
+Build and disposable-server checks passed the 252/253-page boundary, complete
+base-registry category coverage/order, seeded draws and exclusions, both-hand
+opening, Survival/Creative consumption, full-inventory delivery, and portfolio/
+Folder persistence in a chest across restart. Shared models/textures were
+verified in the JAR. The server was stopped and its world removed. No client
+joined those fixtures; Creative presentation, editor and Binder interaction
+remain the in-game check. Future JEI collection guides should cover these items.
+
+### Writing Desk
+
+The local `1.0.1.106-beta.1` slice adapts the 1.21.1 Writing Desk, its
+two-block model, inventory, server catalog and existing GUI. It reuses the
+Legacy desk/scrollbar/page atlases and current block textures. Selected pages
+and white paper stacks render on the desk using the existing offsets.
+
+There are 88 collection tabs, cycled four at a time. Each holds a loose Page
+or a collection with its normal capacity. Search, AZ sorting, ALL view,
+category filtering, page selection, movement and extraction retain the
+1.21.1 menu rules. Link Panels cannot be stored or copied, and no Link Panel
+creation recipe is added to the desk. Unknown pages remain recoverable but
+cannot be copied while unresolved. Unsupported port effects remain red.
+
+Supply paper and Ink Vials, select a known symbol, then take its virtual output
+to copy it. Previewing consumes nothing; taking a copy consumes one paper and
+one ink by default. `[writing] symbol_ink_cost` in `rivencraft-local.toml`
+retains the 1.21.1 configurable cost. Vials fill a 16-unit meter and return
+vanilla glass bottles. Refilling is event-driven and requires bottle space;
+there is no refill server ticker. Originals remain in their collection.
+
+The desk recipe and its recipe-unlock advancement are adapted to 26.3.
+New Minecraft handles Container drops during block-entity removal, so the
+old onRemove drop call is replaced by partner cleanup without duplicate
+inventory drops. The GUI uses current input helpers, including Escape while
+search is focused. The same mouse-button correction fixes Notebook right-click
+and scrollbar dragging. Progression awards and JEI guides remain later work.
+
+Test placement/orientation and opening from both halves, paper/selected-page
+rendering and neighboring block visibility. Check the atlas layout and tab
+numerals, cycling 0–87, searching/sorting/ALL, page dragging into inventory,
+and copying with paper/ink. Confirm costs occur only on pickup, bottles block
+refill when full, and removing bottle space allows refill. Restart with loaded
+collections and a selected page. Break either half and check drops once.
+
+Build and disposable-server checks passed copy preview/pickup costs,
+inventory-full rejection, Link Panel rejection, sparse page movement/extraction,
+88-tab reachability, all four facings and both halves' removal/drop counts.
+Collections, active tab, ink, paper and display page survived full restart.
+Recipe/advancement data loaded; shared models and atlases were verified in
+the JAR. No client joined these fixtures: visuals, mouse and live catalog
+updates remain the in-game check. The server was stopped and world removed.
+
 From the repository root:
 
 ```sh

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_1.0.1.98-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/build.gradle

@@ -203,6 +203,23 @@ 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 'assets/rivencraft/textures/item/ink_vial.png.mcmeta'
         include 'assets/rivencraft/models/item/ink_vial.json'
         include 'assets/rivencraft/models/item/crystal_shard.json'
@@ -215,6 +232,8 @@ tasks.named('processResources', ProcessResources).configure {
         include 'assets/rivencraft/textures/gui/notebook_pages.png'
         include 'assets/rivencraft/textures/gui/bookui_pager.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'
@@ -233,6 +252,8 @@ tasks.named('processResources', ProcessResources).configure {
         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 +7,4 @@ 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=1.0.1.106-beta.1

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.",

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

@@ -0,0 +1,35 @@
+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 ReturnLinkMode { ON_CREATION, ALWAYS, DISABLED }
+    public static final ModConfigSpec SPEC;
+    public static final ModConfigSpec.IntValue SYMBOL_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("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("writing");
+        SYMBOL_INK_COST = builder.comment("Ink units consumed for one Writing Desk symbol copy.")
+                .defineInRange("symbol_ink_cost", 1, 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();
+        SPEC = builder.build();
+    }
+
+    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 +91,10 @@ 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<LinkBookTarget>> LINK_BOOK_TARGET = COMPONENTS.registerComponentType(
             "link_book_target", builder -> builder.persistent(LinkBookTarget.CODEC)
                     .networkSynchronized(LinkBookTarget.STREAM_CODEC));
@@ -110,6 +123,10 @@ 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<StarFissureBlock> STAR_FISSURE =
             BLOCKS.registerBlock("star_fissure", StarFissureBlock::new,
                     () -> BlockBehaviour.Properties.ofFullCopy(Blocks.END_PORTAL).lightLevel(state -> 6));
@@ -134,6 +151,25 @@ 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,
@@ -166,10 +202,12 @@ 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);
@@ -179,6 +217,7 @@ public final class Rivencraft {
         PortChunkGenerators.register(modEventBus);
         NeoForge.EVENT_BUS.addListener(RuntimeAgeBackend::onLevelLoad);
         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(AgeCatalogSync::onLogin);
         NeoForge.EVENT_BUS.addListener(AgeCatalogSync::onLogout);

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/PortAgeCommands.java

@@ -69,6 +69,130 @@ public final class PortAgeCommands {
                                     return 1;
                                 })))
                 .then(Commands.literal("age")
+                        .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("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 +232,10 @@ 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)))
@@ -692,6 +819,63 @@ 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 +1130,24 @@ 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(
+            String distributionName = StringArgumentType.getString(context, "distribution");
-                    StringArgumentType.getString(context, "distribution").toUpperCase(Locale.ROOT));
+            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)),
+            var pages = new java.util.ArrayList<Identifier>();
-                    symbol.apply("biome/" + distribution.name().toLowerCase(Locale.ROOT)));
+            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 +1172,10 @@ 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 +1184,121 @@ 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) {
@@ -1947,6 +2257,119 @@ 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/PortAgeTravel.java

@@ -37,7 +37,7 @@ public final class PortAgeTravel {
         return moved ? null : "Teleportation failed; remaining in source dimension";
     }
 
-    private static BlockPos findLanding(ServerLevel target) {
+    static BlockPos findLanding(ServerLevel target) {
         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
@@ -112,7 +112,7 @@ 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 +1,99 @@
+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 = net.neoforged.neoforge.common.util.FakePlayerFactory.get(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");
+            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 (!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/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()
+        if (distribution == null || distribution == Distribution.SINGLE && biomes.size() != 1
-                || 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/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/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/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/PortRandomAgeSelection.java

@@ -19,30 +19,18 @@ public final class PortRandomAgeSelection {
     public static Selection select(MinecraftServer server, long seed) {
         // 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),
+        PortAgeTerrain terrain = terrain(seed);
-                List.of(PortAgeTerrain.AMPLIFIED, PortAgeTerrain.CAVE, PortAgeTerrain.FLAT,
-                        PortAgeTerrain.ISLAND, PortAgeTerrain.STANDARD, PortAgeTerrain.VOID),
-                new int[]{1, 1, 5, 1, 6, 1});
         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),
+        PortBiomePlan.Distribution distribution = distribution(seed);
-                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});
         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)
-            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) {
@@ -54,14 +42,30 @@ 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 weighted(new Random(seed ^ 0x5445525241494E4CL), terrains(), new int[]{1, 1, 5, 1, 6, 1});
+    }
+
+    /** First AgeTraits draw in 1.21.1; shared by random and partly authored Ages. */
+    public static PortBiomePlan.Distribution distribution(long seed) {
+        return 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});
+    }
+
     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()
+            return caveBiomes(server.registryAccess());
-                    .filter(PortRegistryPages::isCaveBiome)
-                    .map(holder -> holder.key().identifier())
-                    .sorted().toList();
-            return caves.isEmpty() ? List.of(Identifier.withDefaultNamespace("lush_caves")) : caves;
         }
         List<Identifier> surface = server.overworld().getChunkSource().getGenerator().getBiomeSource()
                 .possibleBiomes().stream().flatMap(holder -> holder.unwrapKey().stream())
@@ -69,6 +73,12 @@ public final class PortRandomAgeSelection {
         return surface.isEmpty() ? List.of(Identifier.withDefaultNamespace("plains")) : surface;
     }
 
+    public static List<Identifier> caveBiomes(net.minecraft.core.HolderLookup.Provider 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;
+    }
+
     static <T> T weighted(Random random, List<T> choices, int[] weights) {
         int total = 0;
         for (int weight : weights) total += weight;

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

@@ -47,7 +47,7 @@ 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 +1,44 @@
+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);
+        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/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());
+                .collect(java.util.stream.Collectors.toUnmodifiableSet());
-        return compatible.isEmpty() || biomes.stream().anyMatch(compatible::contains);
     }
 
     private static Map<Identifier, Integer> enabled(List<Identifier> pages) {

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

@@ -0,0 +1,98 @@
+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 = net.neoforged.neoforge.common.util.FakePlayerFactory.get(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");
+            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

@@ -366,15 +366,14 @@ 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);
@@ -399,9 +398,12 @@ public final class RuntimeAgeBackend {
                                     PortAgeColors colors, PortDayCycle dayCycle) {
         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 +455,8 @@ 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) {

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/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/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.PortConfig.SYMBOL_INK_COST.get();
+        return InkVialExchange.canPay(items, INK, RETURN, inkRemaining, cost);
+    }
+
+    public boolean consumeCopyMaterials() {
+        if (!canConsumeCopyMaterials()) return false;
+        int cost = net.dnorberg.rivencraft.PortConfig.SYMBOL_INK_COST.get();
+        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

@@ -26,6 +26,7 @@ public final class AgeCatalogClient {
 
     @SubscribeEvent
     public static void register(RegisterClientPayloadHandlersEvent event) {
+        event.register(net.dnorberg.rivencraft.network.WritingDeskCatalogPayload.TYPE, ClientWritingDeskCatalog::handle);
         event.register(AgeCatalogPayload.TYPE, (payload, context) -> {
             if (!(context.listener() instanceof ClientPacketListener listener)) return;
             net.dnorberg.rivencraft.age.PortAgeColors.updateClient(payload.colors());

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/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 +18,16 @@ 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);
     }
 
     @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.NOTEBOOK_MENU.get(), NotebookScreen::new);
+        event.register(Rivencraft.WRITING_DESK_MENU.get(), WritingDeskScreen::new);
     }
 
     @SubscribeEvent

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

@@ -0,0 +1,60 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.math.Axis;
+import net.dnorberg.rivencraft.block.WritingDeskBlock;
+import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
+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.world.item.ItemDisplayContext;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.phys.Vec3;
+
+/** The existing selected-page and white-paper display, extracted for 26.3. */
+public final class WritingDeskRenderer implements BlockEntityRenderer<WritingDeskBlockEntity, WritingDeskRenderer.State> {
+    private final ItemModelResolver resolver;
+    public WritingDeskRenderer(BlockEntityRendererProvider.Context context) { resolver = context.itemModelResolver(); }
+    public static final class State extends BlockEntityRenderState {
+        final ItemStackRenderState paper = new ItemStackRenderState();
+        final ItemStackRenderState page = new ItemStackRenderState();
+        int layers;
+        float rotation;
+    }
+    @Override public State createRenderState() { return new State(); }
+    @Override public void extractRenderState(WritingDeskBlockEntity desk, State state, float partialTick,
+                                             Vec3 camera, ModelFeatureRenderer.CrumblingOverlay overlay) {
+        BlockEntityRenderer.super.extractRenderState(desk, state, partialTick, camera, overlay);
+        int count = desk.getItem(WritingDeskBlockEntity.PAPER).getCount();
+        state.layers = count == 0 ? 0 : Math.min(4, 1 + count / 16);
+        state.rotation = 180 - desk.getBlockState().getValue(WritingDeskBlock.FACING).toYRot();
+        resolver.updateForTopItem(state.paper, new ItemStack(Items.PAPER), ItemDisplayContext.FIXED, desk.getLevel(), null, 0);
+        resolver.updateForTopItem(state.page, desk.displayPage(), ItemDisplayContext.FIXED, desk.getLevel(), null, 0);
+    }
+    @Override public void submit(State state, PoseStack pose, SubmitNodeCollector collector, CameraRenderState camera) {
+        pose.pushPose();
+        pose.translate(0.5, 0, 0.5);
+        pose.rotateDegrees(Axis.YP, state.rotation);
+        for (int i = 0; i < state.layers; i++) draw(state.paper, pose, collector, state.lightCoords,
+                1.22, 0.27 + i * 0.008, -0.14, 0.55F);
+        if (!state.page.isEmpty()) draw(state.page, pose, collector, state.lightCoords, 1.0, 0.572, 0, 0.8F);
+        pose.popPose();
+    }
+    private static void draw(ItemStackRenderState item, PoseStack pose, SubmitNodeCollector collector,
+                             int light, double x, double y, double z, float scale) {
+        pose.pushPose();
+        pose.translate(x, y, z);
+        pose.rotateDegrees(Axis.XP, 90);
+        pose.scale(scale, scale, scale);
+        item.submit(pose, collector, light, OverlayTexture.NO_OVERLAY, 0);
+        pose.popPose();
+    }
+    @Override public boolean shouldRenderOffScreen() { return true; }
+}

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

@@ -0,0 +1,510 @@
+package net.dnorberg.rivencraft.client;
+
+import java.util.List;
+import java.util.Locale;
+import java.util.ArrayList;
+import java.util.Comparator;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.writing.PageContent;
+import net.dnorberg.rivencraft.menu.WritingDeskMenu;
+import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.writing.SymbolDisplayMetadata;
+import net.minecraft.client.gui.GuiGraphicsExtractor;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.components.EditBox;
+import net.minecraft.client.gui.components.Tooltip;
+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.Slot;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.client.input.MouseButtonEvent;
+import net.minecraft.client.input.KeyEvent;
+import com.mojang.blaze3d.platform.InputConstants;
+import net.minecraft.client.renderer.RenderPipelines;
+
+/** Legacy desk atlas layout, with four visible tabs out of the desk's 88 collections. */
+public final class WritingDeskScreen extends AbstractContainerScreen<WritingDeskMenu> {
+    private static final Identifier PAGE_ATLAS = Identifier.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "textures/gui/notebook_pages.png");
+    private static final Identifier LEGACY_DESK = Identifier.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "textures/gui/writing_desk_legacy.png");
+    private static final Identifier SCROLLBAR = Identifier.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "textures/gui/scrollbar.png");
+    private int lastCollection = -1;
+    private int selectedPage;
+    private int scrollRows;
+    private boolean allMode;
+    private boolean sortAlphabetically;
+    private int selectedCollection = -1;
+    private Identifier selectedCategory;
+    private EditBox search;
+    private Button categoryButton;
+    private Button allButton;
+    private Button sortButton;
+    private boolean draggingScrollbar;
+    private record DisplayPage(int collection, int index, ItemStack stack) {}
+    private DisplayPage pageDragSource;
+    private double pageDragStartX;
+    private double pageDragStartY;
+    private boolean draggingPage;
+
+    private boolean isPhysicalPageView() {
+        return !allMode && !sortAlphabetically && selectedCategory == null
+                && (search == null || search.getValue().isBlank());
+    }
+
+    public WritingDeskScreen(WritingDeskMenu menu, Inventory inventory, Component title) {
+        super(menu, inventory, title, 409, 186);
+        titleLabelX = 222;
+    }
+
+    @Override public boolean isPauseScreen() { return false; }
+
+    @Override protected void init() {
+        super.init();
+        sortButton = addRenderableWidget(Button.builder(Component.literal("AZ"), button -> {
+            sortAlphabetically = !sortAlphabetically;
+            scrollRows = 0;
+        }).bounds(leftPos + 58, topPos, 20, 18)
+                .tooltip(Tooltip.create(Component.translatable("screen.rivencraft.writing_desk.sort"))).build());
+        allButton = addRenderableWidget(Button.builder(Component.literal("ALL"), button -> {
+            allMode = !allMode;
+            scrollRows = 0;
+            if (!allMode) {
+                selectedCollection = -1;
+                selectedPage = 0;
+                if (minecraft != null && minecraft.gameMode != null)
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId, WritingDeskMenu.PAGE_BUTTON_BASE);
+            }
+        }).bounds(leftPos + 80, topPos, 28, 18)
+                .tooltip(Tooltip.create(Component.translatable("screen.rivencraft.writing_desk.all"))).build());
+        search = new EditBox(font, leftPos + 110, topPos, 101, 18,
+                Component.translatable("screen.rivencraft.writing_desk.search"));
+        search.setMaxLength(64);
+        search.setHint(Component.translatable("screen.rivencraft.writing_desk.search"));
+        search.setResponder(value -> scrollRows = 0);
+        addRenderableWidget(search);
+        categoryButton = addRenderableWidget(Button.builder(Component.literal("C"), button -> {
+            List<Identifier> categories = menu.catalog().stream()
+                    .map(SymbolDisplayMetadata::category).distinct().sorted().toList();
+            int next = selectedCategory == null ? 0 : categories.indexOf(selectedCategory) + 1;
+            selectedCategory = next >= categories.size() ? null : categories.get(next);
+            categoryButton.setMessage(Component.literal(selectedCategory == null ? "C" : "C*"));
+            scrollRows = 0;
+        }).bounds(leftPos + 213, topPos, 18, 18).build());
+    }
+
+    private List<DisplayPage> filteredPages() {
+        String query = search == null ? "" : search.getValue().trim().toLowerCase(Locale.ROOT);
+        List<DisplayPage> entries = new ArrayList<>();
+        int from = allMode ? 0 : menu.activeCollection();
+        int until = allMode ? WritingDeskBlockEntity.COLLECTIONS : from + 1;
+        for (int collection = from; collection < until; collection++) {
+            List<ItemStack> pages = pages(collection);
+            int last = -1;
+            for (int i = 0; i < pages.size(); i++) if (!pages.get(i).isEmpty()) last = i;
+            // A notebook has exactly its normal GUI capacity; a loose page has one position.
+            if (isPhysicalPageView()) last = menu.pageCapacity(collection) - 1;
+            for (int i = 0; i <= last; i++) {
+                ItemStack page = i < pages.size() ? pages.get(i) : ItemStack.EMPTY;
+                if (page.isEmpty() && (allMode || sortAlphabetically || !query.isEmpty() || selectedCategory != null)) continue;
+                if (!page.isEmpty() && !query.isEmpty()
+                        && !page.getHoverName().getString().toLowerCase(Locale.ROOT).contains(query)
+                        && !PageItem.content(page).symbol().map(symbol -> symbol.id().toString()
+                        .toLowerCase(Locale.ROOT).contains(query)).orElse(false)) continue;
+                if (!page.isEmpty() && selectedCategory != null) {
+                    Identifier id = PageItem.content(page).symbol().map(symbol -> symbol.id()).orElse(null);
+                    if (menu.catalog().stream().noneMatch(metadata -> metadata.id().equals(id)
+                            && metadata.category().equals(selectedCategory))) continue;
+                }
+                entries.add(new DisplayPage(collection, i, page));
+            }
+        }
+        if (sortAlphabetically) entries.sort(Comparator
+                .comparing((DisplayPage entry) -> entry.stack().getHoverName().getString(), String.CASE_INSENSITIVE_ORDER)
+                .thenComparingInt(DisplayPage::collection).thenComparingInt(DisplayPage::index));
+        return entries;
+    }
+
+    @Override public void extractBackground(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        int x = leftPos;
+        int y = topPos;
+        // Legacy GuiWritingDesk draws the entire 176x166 panel, not a stretched swatch.
+        graphics.blit(RenderPipelines.GUI_TEXTURED, LEGACY_DESK, x + 233, y + 20, 0, 0, 176, 166, 256, 256);
+        drawTabControl(graphics, 20, 203, menu.firstVisibleTab() > 0);
+        for (int i = 0; i < 4; i++) {
+            int tab = menu.firstVisibleTab() + i;
+            int tabY = y + 29 + i * 37;
+            graphics.blit(RenderPipelines.GUI_TEXTURED, LEGACY_DESK, x, tabY, 0, 166, 58, 37, 256, 256,
+                    tab == menu.activeCollection() && !allMode ? 0xFF8080FF : -1);
+            // Legacy numbers its Writing Desk collections from zero.
+            drawNumeral(graphics, tab, x + (tab < 25 ? 8 : 4), tabY + 3, 19);
+            ItemStack collection = menu.getSlot(tab).getItem();
+            if (!collection.isEmpty()) {
+                String name = collection.getHoverName().getString();
+                float scale = Math.min(1F, 50F / Math.max(1, font.width(name)));
+                graphics.pose().pushMatrix();
+                graphics.pose().translate(x + 4, tabY + 25);
+                graphics.pose().scale(scale, scale);
+                graphics.text(font, name, 0, 0, 0xFF404040, false);
+                graphics.pose().popMatrix();
+            }
+        }
+        drawTabControl(graphics, 177, 212, menu.firstVisibleTab() < WritingDeskBlockEntity.COLLECTIONS - 4);
+        // GuiElementVSlider: 4-pixel caps, repeated 22-pixel track, 12x15 thumb.
+        graphics.blit(RenderPipelines.GUI_TEXTURED, SCROLLBAR, x + 213, y + 20, 0, 0, 20, 4, 32, 32);
+        for (int offset = 4; offset < 162; offset += 22)
+            graphics.blit(RenderPipelines.GUI_TEXTURED, SCROLLBAR, x + 213, y + 20 + offset, 0, 4, 20, Math.min(22, 162 - offset), 32, 32);
+        graphics.blit(RenderPipelines.GUI_TEXTURED, SCROLLBAR, x + 213, y + 182, 0, 26, 20, 4, 32, 32);
+        int totalRows = (filteredPages().size() + 4) / 5;
+        int maxScroll = Math.max(0, totalRows - 4);
+        scrollRows = Math.clamp(scrollRows, 0, maxScroll);
+        int thumbY = y + 24 + (maxScroll == 0 ? 0 : scrollRows * 143 / maxScroll);
+        graphics.blit(RenderPipelines.GUI_TEXTURED, SCROLLBAR, x + 217, thumbY, 20, draggingScrollbar ? 15 : 0, 12, 15, 32, 32);
+        graphics.fill(x + 365, y + 27, x + 381, y + 97, 0xFF303035);
+        graphics.fill(x + 366, y + 28, x + 380, y + 96, 0xFF6666AA);
+        int filled = 68 * menu.inkRemaining() / 16;
+        if (filled > 0) graphics.fill(x + 366, y + 96 - filled, x + 380, y + 96, 0xFF15151B);
+    }
+
+    private void drawTabControl(GuiGraphicsExtractor graphics, int y, int textureY, boolean enabled) {
+        graphics.blit(RenderPipelines.GUI_TEXTURED, LEGACY_DESK, leftPos, topPos + y, 0, textureY, 58, 9, 256, 256,
+                enabled ? -1 : 0xFF666666);
+    }
+
+    @Override protected void extractLabels(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        // Legacy leaves the inventory grid unlabeled.
+    }
+
+    @Override public void extractContents(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        super.extractContents(graphics, mouseX, mouseY, partialTick);
+        if (sortAlphabetically) graphics.outline(leftPos + 58, topPos, 20, 18, 0xFFFFD061);
+        if (allMode) graphics.outline(leftPos + 80, topPos, 28, 18, 0xFFFFD061);
+        renderCollection(graphics);
+        if (draggingPage && pageDragSource != null) {
+            DisplayPage target = pageAtMouse(mouseX, mouseY);
+            if (target != null && canMovePage(pageDragSource, target)) {
+                int x = leftPos + 58 + ((int) mouseX - leftPos - 58) / 31 * 31;
+                int y = topPos + 20 + ((int) mouseY - topPos - 20) / 41 * 41;
+                graphics.outline(x, y, 30, 40, 0xFF57D478);
+            }
+            graphics.fakeItem(pageDragSource.stack(), mouseX - 8, mouseY - 8);
+        }
+
+    }
+
+    @Override protected void extractTooltip(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        super.extractTooltip(graphics, mouseX, mouseY);
+        if (mouseX >= leftPos + 365 && mouseX < leftPos + 381
+                && mouseY >= topPos + 27 && mouseY < topPos + 97) {
+            graphics.setTooltipForNextFrame(font, Component.translatable("screen.rivencraft.writing_desk.ink",
+                    menu.inkRemaining(), 16), mouseX, mouseY);
+        }
+        if (mouseX >= leftPos + 213 && mouseX < leftPos + 231
+                && mouseY >= topPos && mouseY < topPos + 18) {
+            graphics.setTooltipForNextFrame(font, Component.translatable("screen.rivencraft.writing_desk.category",
+                    selectedCategory == null
+                            ? Component.translatable("screen.rivencraft.writing_desk.all_categories")
+                            : Component.literal(selectedCategory.toString())), mouseX, mouseY);
+        }
+        if (mouseX >= leftPos && mouseX < leftPos + 58) {
+            int localY = mouseY - topPos;
+            if (localY >= 20 && localY < 29)
+                graphics.setTooltipForNextFrame(font, Component.translatable("screen.rivencraft.writing_desk.previous_tabs"), mouseX, mouseY);
+            else if (localY >= 177 && localY < 186)
+                graphics.setTooltipForNextFrame(font, Component.translatable("screen.rivencraft.writing_desk.next_tabs"), mouseX, mouseY);
+            else if (mouseX < leftPos + 34 && localY >= 29 && localY < 177) {
+                int tab = menu.firstVisibleTab() + (localY - 29) / 37;
+                graphics.setTooltipForNextFrame(font, Component.translatable("screen.rivencraft.writing_desk.tab_symbol",
+                        tab), mouseX, mouseY);
+            }
+        }
+    }
+
+    private List<ItemStack> pages(int collectionIndex) {
+        ItemStack collection = menu.getSlot(collectionIndex).getItem();
+        if (collection.is(Rivencraft.PAGE.get())) return List.of(collection);
+        if (CollationFolderItem.isCollection(collection)) {
+            return collection.getOrDefault(Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
+        }
+        return List.of();
+    }
+
+    private void renderCollection(GuiGraphicsExtractor graphics) {
+        if (lastCollection != menu.activeCollection()) {
+            lastCollection = menu.activeCollection();
+            scrollRows = 0;
+            selectedPage = 0;
+            selectedCollection = -1;
+        }
+        List<DisplayPage> entries = filteredPages();
+        for (int i = scrollRows * 5; i < entries.size() && i < scrollRows * 5 + 20; i++) {
+            int column = i % 5;
+            int row = i / 5 - scrollRows;
+            DisplayPage entry = entries.get(i);
+            ItemStack page = entry.stack();
+            int x = leftPos + 58 + column * 31;
+            int y = topPos + 20 + row * 41;
+            drawPage(graphics, page, x, y);
+            if (page.isEmpty()) graphics.fill(x, y, x + 30, y + 40, 0xB8000000);
+            int active = selectedCollection >= 0 ? selectedCollection : menu.activeCollection();
+            if (entry.collection() == active && entry.index() == selectedPage && !page.isEmpty())
+                graphics.outline(x, y, 30, 40, 0xFFFFD061);
+        }
+        int active = selectedCollection >= 0 ? selectedCollection : menu.activeCollection();
+        List<ItemStack> source = pages(active);
+        if (selectedPage >= source.size() || source.get(selectedPage).isEmpty()) return;
+        ItemStack selected = source.get(selectedPage);
+        drawPage(graphics, selected, leftPos + 265, topPos + 26);
+        graphics.fill(leftPos + 261, topPos + 81, leftPos + 360, topPos + 95, 0xFF202020);
+        var symbol = PageItem.content(selected).symbol();
+        if (symbol.isPresent() && PageItem.isCorrupted(symbol.orElseThrow())) {
+            graphics.enableScissor(leftPos + 263, topPos + 82, leftPos + 358, topPos + 94);
+            graphics.text(font, selected.getHoverName(), leftPos + 263, topPos + 84,
+                    0xFFE0E0E0, false);
+            graphics.disableScissor();
+        } else {
+            String title = font.plainSubstrByWidth(selected.getHoverName().getString(), 95);
+            graphics.text(font, title, leftPos + 263, topPos + 84, 0xFFE0E0E0, false);
+        }
+    }
+
+    private void drawPage(GuiGraphicsExtractor graphics, ItemStack page, int x, int y) {
+        graphics.nextStratum();
+        graphics.blit(RenderPipelines.GUI_TEXTURED, PAGE_ATLAS, x, y, 156, 0, 30, 40, 256, 256);
+        if (page.isEmpty()) return;
+        if (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 (!net.dnorberg.rivencraft.writing.PortAuthoredWriting.isPageImplemented(page.get(Rivencraft.SYMBOL_PAGE_ID.get())))
+                graphics.fill(x, y, x + 30, y + 40, 0x55FF3333);
+        }
+    }
+
+    private static void drawNumeral(GuiGraphicsExtractor graphics, int number, int x, int y, int size) {
+        int[] digits = net.dnorberg.rivencraft.writing.PortSymbolNumerals.digitsFor(number);
+        int digitSize = digits.length == 1 ? size : Math.max(8, size * 3 / 4);
+        Identifier components = Identifier.fromNamespaceAndPath("rivencraft", "textures/gui/symbolcomponents.png");
+        for (int digit : digits) {
+            for (int component : net.dnorberg.rivencraft.writing.PortSymbolNumerals.componentsForDigit(digit))
+                graphics.blit(RenderPipelines.GUI_TEXTURED, components, x, y + (size - digitSize) / 2,
+                        (component % 8) * 64, (component / 8) * 64, digitSize, digitSize, 64, 64, 512, 512, 0xFF211A14);
+            x += digitSize + 1;
+        }
+    }
+
+    private DisplayPage pageAtMouse(double mouseX, double mouseY) {
+        int x = (int) Math.floor(mouseX - leftPos - 58);
+        int y = (int) Math.floor(mouseY - topPos - 20);
+        if (x < 0 || x >= 155 || y < 0 || y >= 164 || x % 31 >= 30 || y % 41 >= 40) return null;
+        int index = (y / 41 + scrollRows) * 5 + x / 31;
+        List<DisplayPage> entries = filteredPages();
+        return index < entries.size() ? entries.get(index) : null;
+    }
+
+    private boolean canMovePage(DisplayPage source, DisplayPage target) {
+        return !source.stack().isEmpty()
+                && (CollationFolderItem.isCollection(menu.getSlot(source.collection()).getItem())
+                    || menu.getSlot(source.collection()).getItem().is(Rivencraft.PAGE.get()))
+                && (CollationFolderItem.isCollection(menu.getSlot(target.collection()).getItem())
+                    || menu.getSlot(target.collection()).getItem().is(Rivencraft.PAGE.get()))
+                && (source.collection() != target.collection() || source.index() != target.index());
+    }
+
+    private int extractTargetSlot(double mouseX, double mouseY) {
+        for (Slot slot : menu.slots) {
+            int index = slot.index;
+            if (index >= WritingDeskBlockEntity.COLLECTIONS && index <= WritingDeskMenu.COPY_RESULT) continue;
+            if (!slot.isActive() || !isHovering(slot.x, slot.y, 16, 16, mouseX, mouseY)) continue;
+            ItemStack held = pageDragSource.stack();
+            if (!slot.mayPlace(held)) return -1;
+            ItemStack current = slot.getItem();
+            if (current.isEmpty()) return index;
+            if (index < WritingDeskBlockEntity.COLLECTIONS && CollationFolderItem.isCollection(current)) {
+                List<ItemStack> pages = current.getOrDefault(
+                        Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
+                if (pages.size() < CollationFolderItem.capacity(current) || pages.stream().anyMatch(ItemStack::isEmpty))
+                    return index;
+            } else if (index > WritingDeskMenu.COPY_RESULT && ItemStack.isSameItemSameComponents(current, held)
+                    && current.getCount() < slot.getMaxStackSize(held)) return index;
+            return -1;
+        }
+        return -1;
+    }
+
+    @Override public boolean mouseClicked(MouseButtonEvent event, boolean doubleClick) {
+        double mouseX = event.x(), mouseY = event.y();
+        int button = event.button();
+        if (button == InputConstants.MOUSE_BUTTON_LEFT) {
+            pageDragSource = null;
+            draggingPage = false;
+        }
+        int surfaceX = (int) Math.floor(mouseX - leftPos - 58);
+        int surfaceY = (int) Math.floor(mouseY - topPos - 20);
+        if ((button == InputConstants.MOUSE_BUTTON_LEFT || button == InputConstants.MOUSE_BUTTON_RIGHT) && !menu.getCarried().isEmpty()
+                && surfaceX >= 0 && surfaceX < 155 && surfaceY >= 0 && surfaceY < 164) {
+            if (menu.getCarried().is(Rivencraft.PAGE.get())
+                    && PageItem.content(menu.getCarried()).kind() != PageContent.Kind.LINK_PANEL
+                    && surfaceX % 31 < 30 && surfaceY % 41 < 40) {
+                int index = (surfaceY / 41 + scrollRows) * 5 + surfaceX / 31;
+                List<DisplayPage> entries = filteredPages();
+                // Only displayed positions are addressable. Filtering never turns
+                // empty screen space into additional storage for a loose-page tab.
+                int collection = index < entries.size() ? entries.get(index).collection() : menu.activeCollection();
+                int page = index < entries.size() ? entries.get(index).index() : index;
+                if (index < entries.size() && page < menu.pageCapacity(collection)
+                        && minecraft != null && minecraft.gameMode != null) {
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                            WritingDeskMenu.PLACE_PAGE_BUTTON_BASE + collection * NotebookContents.MAX_PAGES + page);
+                }
+            }
+            return true;
+        }
+        if (button == InputConstants.MOUSE_BUTTON_LEFT) {
+            if (mouseX >= leftPos && mouseX < leftPos + 58) {
+                int y = (int) mouseY - topPos;
+                if (y >= 20 && y < 29 || y >= 177 && y < 186) {
+                    if (minecraft != null && minecraft.gameMode != null)
+                        minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                                y < 29 ? WritingDeskMenu.PREVIOUS_TABS : WritingDeskMenu.NEXT_TABS);
+                    return true;
+                }
+            }
+            if (mouseX >= leftPos + 213 && mouseX < leftPos + 233
+                    && mouseY >= topPos + 20 && mouseY < topPos + 186) {
+                draggingScrollbar = true;
+                setScrollFromMouse(mouseY);
+                return true;
+            }
+            int x = (int) Math.floor(mouseX - leftPos - 58);
+            int y = (int) Math.floor(mouseY - topPos - 20);
+            if (x >= 0 && x < 155 && y >= 0 && y < 164) {
+                DisplayPage entry = pageAtMouse(mouseX, mouseY);
+                if (entry != null && !entry.stack().isEmpty()) {
+                    selectedCollection = entry.collection();
+                    selectedPage = entry.index();
+                    if (menu.getCarried().isEmpty()) {
+                        pageDragSource = entry;
+                        pageDragStartX = mouseX;
+                        pageDragStartY = mouseY;
+                    }
+                    if (minecraft != null && minecraft.gameMode != null) {
+                        int id = WritingDeskMenu.ALL_PAGE_BUTTON_BASE
+                                + entry.collection() * NotebookContents.MAX_PAGES + entry.index();
+                        minecraft.gameMode.handleInventoryButtonClick(menu.containerId, id);
+                    }
+                }
+                return true;
+            }
+        }
+        if (button == InputConstants.MOUSE_BUTTON_LEFT && mouseX >= leftPos && mouseX < leftPos + 58) {
+            for (int i = 0; i < 4; i++) {
+                int top = topPos + 29 + i * 37;
+                boolean overSlot = mouseX >= leftPos + 36 && mouseX < leftPos + 54
+                        && mouseY >= top + 4 && mouseY < top + 22;
+                if (mouseY >= top && mouseY < top + 37 && !overSlot) {
+                    allMode = false;
+                    selectedCollection = -1;
+                    if (minecraft != null && minecraft.gameMode != null) {
+                        minecraft.gameMode.handleInventoryButtonClick(menu.containerId, menu.firstVisibleTab() + i);
+                    }
+                    return true;
+                }
+            }
+        }
+        return super.mouseClicked(event, doubleClick);
+    }
+
+    @Override public boolean mouseScrolled(double mouseX, double mouseY, double scrollX, double scrollY) {
+        if (mouseX >= leftPos + 58 && mouseX < leftPos + 233
+                && mouseY >= topPos + 20 && mouseY < topPos + 186) {
+            int rows = (filteredPages().size() + 4) / 5;
+            scrollRows = Math.clamp(scrollRows - (int) Math.signum(scrollY), 0, Math.max(0, rows - 4));
+            return true;
+        }
+        return super.mouseScrolled(mouseX, mouseY, scrollX, scrollY);
+    }
+
+    private void setScrollFromMouse(double mouseY) {
+        int rows = (filteredPages().size() + 4) / 5;
+        int max = Math.max(0, rows - 4);
+        scrollRows = Math.clamp((int) Math.round((mouseY - topPos - 31.5) * max / 143.0), 0, max);
+    }
+
+    @Override public boolean mouseDragged(MouseButtonEvent event, double dragX, double dragY) {
+        double mouseX = event.x(), mouseY = event.y();
+        int button = event.button();
+        if (button == InputConstants.MOUSE_BUTTON_LEFT && pageDragSource != null) {
+            if (Math.abs(mouseX - pageDragStartX) >= 4 || Math.abs(mouseY - pageDragStartY) >= 4)
+                draggingPage = true;
+            return true;
+        }
+        if (button == InputConstants.MOUSE_BUTTON_LEFT && draggingScrollbar) {
+            setScrollFromMouse(mouseY);
+            return true;
+        }
+        return super.mouseDragged(event, dragX, dragY);
+    }
+
+    @Override public boolean mouseReleased(MouseButtonEvent event) {
+        double mouseX = event.x(), mouseY = event.y();
+        int button = event.button();
+        if (button == InputConstants.MOUSE_BUTTON_LEFT && pageDragSource != null) {
+            if (draggingPage) {
+                DisplayPage target = pageAtMouse(mouseX, mouseY);
+                if (target != null && canMovePage(pageDragSource, target)
+                        && minecraft != null && minecraft.gameMode != null) {
+                    selectedCollection = target.collection();
+                    selectedPage = target.index();
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                            WritingDeskMenu.movePageButtonId(pageDragSource.collection(), pageDragSource.index(),
+                                    target.collection(), target.index()));
+                } else if (target == null && minecraft != null && minecraft.gameMode != null) {
+                    int targetSlot = extractTargetSlot(mouseX, mouseY);
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                            WritingDeskMenu.extractPageButtonId(pageDragSource.collection(), pageDragSource.index(),
+                                    targetSlot));
+                }
+            }
+            pageDragSource = null;
+            draggingPage = false;
+            return true;
+        }
+        if (button == InputConstants.MOUSE_BUTTON_LEFT && draggingScrollbar) {
+            draggingScrollbar = false;
+            return true;
+        }
+        return super.mouseReleased(event);
+    }
+
+    @Override public boolean keyPressed(KeyEvent event) {
+        if (event.isEscape()) return super.keyPressed(event);
+        if (search != null && search.isFocused()) {
+            search.keyPressed(event);
+            return true;
+        }
+        if (minecraft != null && minecraft.gameMode != null) {
+            if (event.key() == InputConstants.KEY_PAGEUP) {
+                minecraft.gameMode.handleInventoryButtonClick(menu.containerId, WritingDeskMenu.PREVIOUS_TABS);
+                return true;
+            }
+            if (event.key() == InputConstants.KEY_PAGEDOWN) {
+                minecraft.gameMode.handleInventoryButtonClick(menu.containerId, WritingDeskMenu.NEXT_TABS);
+                return true;
+            }
+        }
+        return super.keyPressed(event);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/entity/DroppedBookEntity.java

@@ -0,0 +1,51 @@
+package net.dnorberg.rivencraft.entity;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.storage.ValueInput;
+import net.minecraft.world.level.storage.ValueOutput;
+import net.minecraft.world.phys.Vec3;
+
+/** Recoverable open-book entity, with the 1.21.1 decay and weather behavior. */
+public final class DroppedBookEntity extends ItemEntity {
+    private static final int SLOW_DECAY_INTERVAL = 10_000;
+    private int decayTicks;
+
+    public DroppedBookEntity(EntityType<? extends DroppedBookEntity> type, Level level) { super(type, level); }
+
+    public DroppedBookEntity(Level level, Vec3 position, ItemStack book) {
+        this(Rivencraft.DROPPED_BOOK.get(), level);
+        setPos(position.x, position.y + 0.25, position.z);
+        setDeltaMovement(Vec3.ZERO);
+        setItem(book);
+        setUnlimitedLifetime();
+        setPickUpDelay(20);
+    }
+
+    @Override
+    public void tick() {
+        super.tick();
+        if (!(level() instanceof ServerLevel serverLevel) || isRemoved()) return;
+        if (++decayTicks >= SLOW_DECAY_INTERVAL) {
+            decayTicks = 0;
+            hurtServer(serverLevel, damageSources().starve(), 1.0F);
+        }
+        if (!isRemoved() && isInWaterOrRain()) hurtServer(serverLevel, damageSources().drown(), 1.0F);
+    }
+
+    @Override
+    protected void addAdditionalSaveData(ValueOutput output) {
+        super.addAdditionalSaveData(output);
+        output.putInt("BookDecayTicks", decayTicks);
+    }
+
+    @Override
+    protected void readAdditionalSaveData(ValueInput input) {
+        super.readAdditionalSaveData(input);
+        decayTicks = Math.clamp(input.getIntOr("BookDecayTicks", 0), 0, SLOW_DECAY_INTERVAL - 1);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/item/CollationFolderItem.java

@@ -0,0 +1,25 @@
+package net.dnorberg.rivencraft.item;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.world.item.ItemStack;
+
+/** Legacy's compact page collection, using the existing Notebook page editor. */
+public final class CollationFolderItem extends NotebookItem {
+    public static final int MAX_PAGES = 27;
+
+    public CollationFolderItem(Properties properties) {
+        super(properties);
+    }
+
+    public static boolean isCollection(ItemStack stack) {
+        return stack.is(Rivencraft.NOTEBOOK.get()) || stack.is(Rivencraft.COLLATION_FOLDER.get())
+                || stack.is(Rivencraft.SYMBOL_PORTFOLIO.get());
+    }
+
+    public static int capacity(ItemStack stack) {
+        return stack.is(Rivencraft.COLLATION_FOLDER.get()) ? MAX_PAGES
+                : stack.is(Rivencraft.NOTEBOOK.get()) || stack.is(Rivencraft.SYMBOL_PORTFOLIO.get())
+                        ? NotebookContents.MAX_PAGES : 0;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/item/NotebookItem.java

@@ -0,0 +1,44 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.function.Consumer;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.menu.NotebookMenu;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.ChatFormatting;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.SimpleMenuProvider;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.TooltipFlag;
+import net.minecraft.world.item.component.TooltipDisplay;
+import net.minecraft.world.level.Level;
+
+/** The 1.21.1 collection editor opened through a server-owned menu. */
+public class NotebookItem extends Item {
+    public NotebookItem(Properties properties) { super(properties); }
+
+    @Override
+    public InteractionResult use(Level level, Player player, InteractionHand hand) {
+        ItemStack notebook = player.getItemInHand(hand);
+        if (player instanceof ServerPlayer serverPlayer) {
+            serverPlayer.openMenu(new SimpleMenuProvider(
+                    (id, inventory, ignored) -> new NotebookMenu(id, inventory, hand), notebook.getHoverName()),
+                    buffer -> buffer.writeBoolean(hand == InteractionHand.OFF_HAND));
+        }
+        return InteractionResult.SUCCESS;
+    }
+
+    @Override
+    public void appendHoverText(ItemStack stack, TooltipContext context, TooltipDisplay display,
+                                Consumer<Component> tooltip, TooltipFlag flag) {
+        var contents = stack.getOrDefault(Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY);
+        tooltip.accept(Component.translatable("item.rivencraft.notebook.pages", contents.pageCount(),
+                CollationFolderItem.capacity(stack)).withStyle(ChatFormatting.GRAY));
+        if (contents.unresolvedCount() > 0) tooltip.accept(Component.translatable(
+                "item.rivencraft.notebook.unresolved", contents.unresolvedCount()).withStyle(ChatFormatting.RED));
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/item/PageItem.java

@@ -42,6 +42,22 @@ public final class PageItem extends Item {
         return stack;
     }
 
+    public static ItemStack createSymbolPage(net.dnorberg.rivencraft.writing.SymbolReference symbol) {
+        return createSymbolPage(symbol.id());
+    }
+
+    /** Resolved view of the port's existing components; no second saved schema. */
+    public static net.dnorberg.rivencraft.writing.PageContent content(ItemStack stack) {
+        var id = stack.get(Rivencraft.SYMBOL_PAGE_ID.get());
+        if (isLinkPanel(stack)) return net.dnorberg.rivencraft.writing.PageContent.LINK_PANEL;
+        return id == null ? net.dnorberg.rivencraft.writing.PageContent.BLANK
+                : net.dnorberg.rivencraft.writing.PageContent.symbol(
+                        new net.dnorberg.rivencraft.writing.SymbolReference(id)).resolve();
+    }
+
+    public static boolean isUsableWriting(ItemStack stack) { return content(stack).isResolvedSymbol(); }
+    public static boolean isCorrupted(net.dnorberg.rivencraft.writing.SymbolReference symbol) { return isCorrupted(symbol.id()); }
+
     @Override
     public Component getName(ItemStack stack) {
         Component customName = stack.get(DataComponents.CUSTOM_NAME);

ports/mc263/src/main/java/net/dnorberg/rivencraft/item/PortHandheldTravel.java

@@ -0,0 +1,35 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.function.Supplier;
+import net.dnorberg.rivencraft.entity.DroppedBookEntity;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.util.Prediction;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.ItemStack;
+
+/** Leaves only the active book behind after successful handheld travel. */
+public final class PortHandheldTravel {
+    private PortHandheldTravel() {}
+
+    public static String travel(ServerPlayer player, InteractionHand hand, ItemStack book,
+                                Supplier<String> travel) {
+        if (book.isEmpty() || player.getItemInHand(hand) != book) return "Book is no longer in the active hand";
+        var source = player.level();
+        var departure = player.position();
+        player.setItemInHand(hand, ItemStack.EMPTY);
+        boolean dropped = false;
+        try {
+            String failure = travel.get();
+            if (failure != null) return failure;
+            dropped = source.addFreshEntity(new DroppedBookEntity(source, departure, book));
+            return null;
+        } finally {
+            // Rejected travel or a cancelled entity spawn must not consume the book.
+            if (!dropped) {
+                if (player.getItemInHand(hand).isEmpty()) player.setItemInHand(hand, book);
+                else if (!player.getInventory().add(book)) player.drop(book, false, Prediction.SERVER_ONLY);
+            }
+            player.containerMenu.broadcastChanges();
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/item/SealedNotebookItem.java

@@ -0,0 +1,43 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.ArrayList;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.writing.PortSymbolPages;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.util.Prediction;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.Level;
+
+/** The 1.21.1 booster item, opened into a 16-page Collation Folder. */
+public final class SealedNotebookItem extends Item {
+    public SealedNotebookItem(Properties properties) { super(properties); }
+
+    @Override
+    public InteractionResult use(Level level, Player player, InteractionHand hand) {
+        if (level.isClientSide()) return InteractionResult.SUCCESS;
+        if (!(player instanceof ServerPlayer serverPlayer)) return InteractionResult.PASS;
+        ItemStack sealed = player.getItemInHand(hand);
+        ItemStack folder = open(serverPlayer);
+        if (folder.isEmpty()) return InteractionResult.FAIL;
+        if (!player.hasInfiniteMaterials()) sealed.shrink(1);
+        if (sealed.isEmpty()) player.setItemInHand(hand, folder);
+        else if (!player.getInventory().add(folder)) player.drop(folder, false, Prediction.SERVER_ONLY);
+        return InteractionResult.SUCCESS;
+    }
+
+    public static ItemStack open(ServerPlayer player) {
+        var candidates = PortSymbolPages.sealedCandidateIds();
+        if (candidates.isEmpty()) return ItemStack.EMPTY;
+        var pages = new ArrayList<ItemStack>(16);
+        for (int i = 0; i < 16; i++) pages.add(PageItem.createSymbolPage(
+                candidates.get(player.getRandom().nextInt(candidates.size()))));
+        ItemStack folder = new ItemStack(Rivencraft.COLLATION_FOLDER.get());
+        folder.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(pages));
+        return folder;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/item/SymbolPortfolioItem.java

@@ -0,0 +1,39 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.item.ItemStack;
+
+/** Non-craftable, prefilled Legacy-style collections of one symbol-page category. */
+public final class SymbolPortfolioItem extends NotebookItem {
+    public SymbolPortfolioItem(Properties properties) {
+        super(properties);
+    }
+
+    public static List<ItemStack> createVolumes(Identifier category, List<ItemStack> pages) {
+        if (pages.isEmpty()) return List.of();
+        int capacity = NotebookContents.MAX_PAGES;
+        int volumeCount = (pages.size() + capacity - 1) / capacity;
+        List<ItemStack> volumes = new ArrayList<>(volumeCount);
+        for (int volume = 0; volume < volumeCount; volume++) {
+            ItemStack portfolio = new ItemStack(Rivencraft.SYMBOL_PORTFOLIO.get());
+            int first = volume * capacity;
+            int last = Math.min(first + capacity, pages.size());
+            portfolio.set(Rivencraft.NOTEBOOK_CONTENTS.get(),
+                    new NotebookContents(pages.subList(first, last)));
+            Component categoryName = Component.translatableWithFallback(
+                    "itemGroup.rivencraft.pages." + category.getPath(), category.getPath());
+            portfolio.set(DataComponents.CUSTOM_NAME, volumeCount == 1
+                    ? Component.translatable("item.rivencraft.symbol_portfolio.named", categoryName)
+                    : Component.translatable("item.rivencraft.symbol_portfolio.volume",
+                            categoryName, volume + 1, volumeCount));
+            volumes.add(portfolio);
+        }
+        return List.copyOf(volumes);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/menu/NotebookMenu.java

@@ -0,0 +1,205 @@
+package net.dnorberg.rivencraft.menu;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
+import net.minecraft.core.NonNullList;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.world.Container;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.SimpleContainer;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.AbstractContainerMenu;
+import net.minecraft.world.inventory.ContainerInput;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.ItemStack;
+
+public final class NotebookMenu extends AbstractContainerMenu {
+    public static final int NOTEBOOK_SLOTS = NotebookContents.MAX_PAGES;
+    public static final int MOVE_PREVIOUS_BASE = 0;
+    public static final int MOVE_NEXT_BASE = NOTEBOOK_SLOTS;
+    private static final int PLAYER_INVENTORY_START = NOTEBOOK_SLOTS;
+    private final Inventory playerInventory;
+    private final InteractionHand hand;
+    private final int openedHotbarSlot;
+    private final NotebookContainer contents;
+    private final int pageCapacity;
+
+    public NotebookMenu(int containerId, Inventory inventory, RegistryFriendlyByteBuf data) {
+        this(containerId, inventory, data.readBoolean() ? InteractionHand.OFF_HAND : InteractionHand.MAIN_HAND);
+    }
+
+    public NotebookMenu(int containerId, Inventory inventory, InteractionHand hand) {
+        super(Rivencraft.NOTEBOOK_MENU.get(), containerId);
+        this.playerInventory = inventory;
+        this.hand = hand;
+        this.openedHotbarSlot = inventory.getSelectedSlot();
+        this.pageCapacity = CollationFolderItem.capacity(inventory.player.getItemInHand(hand));
+        this.contents = new NotebookContainer(inventory, hand);
+
+        for (int page = 0; page < NOTEBOOK_SLOTS; page++) {
+            // The client draws these pages on a filtered, scrollable surface instead.
+            addSlot(new PageSlot(contents, page, -1000, -1000, page < pageCapacity));
+        }
+        for (int row = 0; row < 3; row++) {
+            for (int column = 0; column < 9; column++) {
+                int inventoryIndex = column + row * 9 + 9;
+                addSlot(playerSlot(inventoryIndex, 8 + column * 18, 135 + row * 18));
+            }
+        }
+        for (int column = 0; column < 9; column++) {
+            addSlot(playerSlot(column, 8 + column * 18, 193));
+        }
+    }
+
+    private Slot playerSlot(int inventoryIndex, int x, int y) {
+        boolean locked = hand == InteractionHand.MAIN_HAND && inventoryIndex == openedHotbarSlot;
+        return locked ? new LockedSlot(playerInventory, inventoryIndex, x, y)
+                : new Slot(playerInventory, inventoryIndex, x, y);
+    }
+
+    public int pageCapacity() { return pageCapacity; }
+
+    @Override
+    public boolean stillValid(Player player) {
+        return player.isAlive()
+                && (hand == InteractionHand.OFF_HAND || player.getInventory().getSelectedSlot() == openedHotbarSlot)
+                && CollationFolderItem.isCollection(player.getItemInHand(hand));
+    }
+
+    @Override
+    public ItemStack quickMoveStack(Player player, int index) {
+        Slot slot = slots.get(index);
+        if (!slot.hasItem()) {
+            return ItemStack.EMPTY;
+        }
+        ItemStack source = slot.getItem();
+        ItemStack original = source.copy();
+        if (index < PLAYER_INVENTORY_START) {
+            if (!moveItemStackTo(source, PLAYER_INVENTORY_START, slots.size(), true)) {
+                return ItemStack.EMPTY;
+            }
+        } else {
+            if (!source.is(Rivencraft.PAGE.get())
+                    || PageItem.isLinkPanel(source)
+                    || !moveItemStackTo(source, 0, PLAYER_INVENTORY_START, false)) {
+                return ItemStack.EMPTY;
+            }
+        }
+        if (source.isEmpty()) {
+            slot.setByPlayer(ItemStack.EMPTY);
+        } else {
+            slot.setChanged();
+        }
+        return original;
+    }
+
+    @Override
+    public boolean clickMenuButton(Player player, int id) {
+        int source;
+        int target;
+        if (id >= MOVE_PREVIOUS_BASE && id < MOVE_NEXT_BASE) {
+            source = id;
+            target = source - 1;
+        } else if (id >= MOVE_NEXT_BASE && id < MOVE_NEXT_BASE + NOTEBOOK_SLOTS) {
+            source = id - MOVE_NEXT_BASE;
+            target = source + 1;
+        } else {
+            return false;
+        }
+        if (source < 0 || source >= pageCapacity || target < 0 || target >= pageCapacity
+                || contents.getItem(source).isEmpty()) {
+            return false;
+        }
+        contents.swap(source, target);
+        broadcastChanges();
+        return true;
+    }
+
+    @Override
+    public void clicked(int slotId, int button, ContainerInput clickType, Player player) {
+        if (!stillValid(player)) {
+            player.closeContainer();
+            return;
+        }
+        if (clickType == ContainerInput.SWAP
+                && (button == openedHotbarSlot && hand == InteractionHand.MAIN_HAND
+                        || button == 40 && hand == InteractionHand.OFF_HAND)) {
+            return;
+        }
+        super.clicked(slotId, button, clickType, player);
+    }
+
+    private static final class PageSlot extends Slot {
+        private final boolean enabled;
+
+        private PageSlot(Container container, int slot, int x, int y, boolean enabled) {
+            super(container, slot, x, y);
+            this.enabled = enabled;
+        }
+
+        @Override public boolean mayPlace(ItemStack stack) {
+            return enabled && stack.is(Rivencraft.PAGE.get())
+                    && !PageItem.isLinkPanel(stack);
+        }
+        @Override public boolean mayPickup(Player player) { return enabled; }
+        @Override public int getMaxStackSize() { return 1; }
+    }
+
+    private static final class LockedSlot extends Slot {
+        private LockedSlot(Container container, int slot, int x, int y) {
+            super(container, slot, x, y);
+        }
+
+        @Override public boolean mayPickup(Player player) { return false; }
+        @Override public boolean mayPlace(ItemStack stack) { return false; }
+    }
+
+    private static final class NotebookContainer extends SimpleContainer {
+        private final Inventory inventory;
+        private final InteractionHand hand;
+        private boolean loading;
+
+        private NotebookContainer(Inventory inventory, InteractionHand hand) {
+            super(NOTEBOOK_SLOTS);
+            this.inventory = inventory;
+            this.hand = hand;
+            ItemStack notebook = inventory.player.getItemInHand(hand);
+            loading = true;
+            List<ItemStack> saved = notebook.getOrDefault(
+                    Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
+            for (int index = 0; index < saved.size(); index++) {
+                super.setItem(index, saved.get(index).copy());
+            }
+            loading = false;
+        }
+
+        private void swap(int first, int second) {
+            loading = true;
+            ItemStack held = getItem(first);
+            setItem(first, getItem(second));
+            setItem(second, held);
+            loading = false;
+            setChanged();
+        }
+
+        @Override
+        public void setChanged() {
+            super.setChanged();
+            ItemStack notebook = inventory.player.getItemInHand(hand);
+            if (loading || !CollationFolderItem.isCollection(notebook)) {
+                return;
+            }
+            int capacity = CollationFolderItem.capacity(notebook);
+            NonNullList<ItemStack> saved = NonNullList.withSize(capacity, ItemStack.EMPTY);
+            for (int index = 0; index < capacity; index++) {
+                ItemStack page = getItem(index);
+                saved.set(index, page.isEmpty() ? ItemStack.EMPTY : page.copyWithCount(1));
+            }
+            notebook.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(saved));
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/menu/PortBookBinderMenu.java

@@ -72,6 +72,14 @@ public final class PortBookBinderMenu extends AbstractContainerMenu {
         if (player.level().isClientSide()) return true;
         int index = id - STRIP_CLICK_BASE;
         ItemStack carried = getCarried();
+        if (net.dnorberg.rivencraft.item.CollationFolderItem.isCollection(carried)) {
+            ItemStack emptied = blockEntity.importCollection(carried,
+                    Math.min(index == 0 ? 0 : index - 1, blockEntity.nextPageIndex()));
+            if (emptied.isEmpty()) return false;
+            setCarried(emptied);
+            broadcastChanges();
+            return true;
+        }
         if (!carried.isEmpty()) {
             if (index == 0) {
                 if (!PageItem.isLinkPanel(carried)
@@ -145,6 +153,12 @@ public final class PortBookBinderMenu extends AbstractContainerMenu {
         } else if (stack.is(Items.LEATHER)) {
             moved = moveItemStackTo(stack, PortBookBinderBlockEntity.COVER,
                     PortBookBinderBlockEntity.COVER + 1, false);
+        } else if (net.dnorberg.rivencraft.item.CollationFolderItem.isCollection(stack)) {
+            ItemStack emptied = blockEntity.importCollection(stack, blockEntity.nextPageIndex());
+            if (emptied.isEmpty()) return ItemStack.EMPTY;
+            slot.setByPlayer(emptied);
+            broadcastChanges();
+            return original;
         } else if (PageItem.isLinkPanel(stack)) {
             moved = moveItemStackTo(stack, PortBookBinderBlockEntity.PANEL,
                     PortBookBinderBlockEntity.PANEL + 1, false);

ports/mc263/src/main/java/net/dnorberg/rivencraft/menu/WritingDeskMenu.java

@@ -0,0 +1,463 @@
+package net.dnorberg.rivencraft.menu;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.writing.NotebookContents;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
+import net.dnorberg.rivencraft.writing.PageContent;
+import net.dnorberg.rivencraft.writing.PortSymbolPages;
+import net.dnorberg.rivencraft.writing.SymbolDisplayMetadata;
+import net.dnorberg.rivencraft.writing.SymbolReference;
+import net.dnorberg.rivencraft.writing.WritingDeskCatalog;
+import net.dnorberg.rivencraft.network.WritingDeskCatalogPayload;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerPlayer;
+import net.neoforged.neoforge.network.PacketDistributor;
+import java.util.List;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.world.Container;
+import net.minecraft.world.SimpleContainer;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.AbstractContainerMenu;
+import net.minecraft.world.inventory.DataSlot;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+
+public final class WritingDeskMenu extends AbstractContainerMenu {
+    public static final int COPY_RESULT = WritingDeskBlockEntity.SIZE;
+    public static final int VISIBLE_TABS = 4;
+    public static final int PREVIOUS_TABS = 90;
+    public static final int NEXT_TABS = 91;
+    public static final int PAGE_BUTTON_BASE = 128;
+    public static final int CATALOG_BUTTON_BASE = 512;
+    public static final int ALL_PAGE_BUTTON_BASE = 32768;
+    public static final int PLACE_PAGE_BUTTON_BASE = 65536;
+    private static final int PAGE_ADDRESS_COUNT = WritingDeskBlockEntity.COLLECTIONS * NotebookContents.MAX_PAGES;
+    public static final int MOVE_PAGE_BUTTON_BASE = PLACE_PAGE_BUTTON_BASE + PAGE_ADDRESS_COUNT;
+    private static final int PLAYER_START = COPY_RESULT + 1;
+    private static final int EXTRACT_TARGET_COUNT = PLAYER_START + 36 + 1;
+    public static final int EXTRACT_PAGE_BUTTON_BASE = MOVE_PAGE_BUTTON_BASE + PAGE_ADDRESS_COUNT * PAGE_ADDRESS_COUNT;
+    private final Container desk;
+    private final WritingDeskBlockEntity blockEntity;
+    private final SimpleContainer result = new SimpleContainer(1);
+    private final boolean clientSide;
+    private int syncedActiveCollection;
+    private int syncedInkRemaining;
+    private int firstVisibleTab;
+    private int selectedPage;
+    private int selectedCollection = -1;
+    private Identifier selectedSymbol;
+    private List<SymbolDisplayMetadata> catalog = List.of();
+    private final ServerPlayer serverViewer;
+
+    public WritingDeskMenu(int id, Inventory inventory, RegistryFriendlyByteBuf data) {
+        this(id, inventory, inventory.player.level().getBlockEntity(data.readBlockPos())
+                instanceof WritingDeskBlockEntity found ? found : null);
+        catalog = WritingDeskCatalog.read(data);
+    }
+
+    public WritingDeskMenu(int id, Inventory inventory, WritingDeskBlockEntity blockEntity) {
+        super(Rivencraft.WRITING_DESK_MENU.get(), id);
+        this.blockEntity = blockEntity;
+        this.desk = blockEntity == null ? new SimpleContainer(WritingDeskBlockEntity.SIZE) : blockEntity;
+        this.clientSide = inventory.player.level().isClientSide();
+        this.serverViewer = inventory.player instanceof ServerPlayer serverPlayer ? serverPlayer : null;
+        if (blockEntity != null && !clientSide) catalog = WritingDeskCatalog.available(blockEntity);
+        firstVisibleTab = blockEntity == null ? 0 : blockEntity.activeCollection() / VISIBLE_TABS * VISIBLE_TABS;
+        addDataSlot(new DataSlot() {
+            @Override public int get() { return firstVisibleTab; }
+            @Override public void set(int value) { firstVisibleTab = value; }
+        });
+        addDataSlot(new DataSlot() {
+            @Override public int get() { return WritingDeskMenu.this.blockEntity == null
+                    ? syncedActiveCollection : WritingDeskMenu.this.blockEntity.activeCollection(); }
+            @Override public void set(int value) { syncedActiveCollection = value; }
+        });
+        addDataSlot(new DataSlot() {
+            @Override public int get() { return WritingDeskMenu.this.blockEntity == null
+                    ? syncedInkRemaining : WritingDeskMenu.this.blockEntity.inkRemaining(); }
+            @Override public void set(int value) { syncedInkRemaining = value; }
+        });
+        for (int i = 0; i < WritingDeskBlockEntity.COLLECTIONS; i++) {
+            addSlot(new DeskSlot(desk, i, 37, 34 + (i % VISIBLE_TABS) * 37, 1));
+        }
+        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.INK, 385, 28, 16));
+        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.RETURN, 385, 80, 64));
+        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.PAPER, 241, 28, 64));
+        addSlot(new DeskSlot(desk, WritingDeskBlockEntity.LEGACY_OUTPUT, -1000, -1000, 64));
+        addSlot(new CopySlot(result, 0, 241, 80));
+        for (int row = 0; row < 3; row++) {
+            for (int column = 0; column < 9; column++) {
+                addSlot(new Slot(inventory, column + row * 9 + 9, 241 + column * 18, 104 + row * 18));
+            }
+        }
+        for (int column = 0; column < 9; column++) {
+            addSlot(new Slot(inventory, column, 241 + column * 18, 162));
+        }
+    }
+
+    public int activeCollection() { return syncedActiveCollection; }
+    public int firstVisibleTab() { return firstVisibleTab; }
+    public int inkRemaining() { return syncedInkRemaining; }
+    public int pageCapacity(int collectionIndex) {
+        if (collectionIndex < 0 || collectionIndex >= WritingDeskBlockEntity.COLLECTIONS) return 0;
+        ItemStack collection = desk.getItem(collectionIndex);
+        return CollationFolderItem.isCollection(collection) ? CollationFolderItem.capacity(collection)
+                : collection.is(Rivencraft.PAGE.get()) ? 1 : 0;
+    }
+    public List<SymbolDisplayMetadata> catalog() { return catalog; }
+    public void setCatalog(List<SymbolDisplayMetadata> symbols) { catalog = List.copyOf(symbols); }
+
+    public static int movePageButtonId(int sourceCollection, int sourcePage, int targetCollection, int targetPage) {
+        int source = sourceCollection * NotebookContents.MAX_PAGES + sourcePage;
+        int target = targetCollection * NotebookContents.MAX_PAGES + targetPage;
+        return MOVE_PAGE_BUTTON_BASE + source * PAGE_ADDRESS_COUNT + target;
+    }
+
+    /** targetSlot is -1 for the cursor, otherwise a visible player or desk-tab slot. */
+    public static int extractPageButtonId(int sourceCollection, int sourcePage, int targetSlot) {
+        int source = sourceCollection * NotebookContents.MAX_PAGES + sourcePage;
+        return EXTRACT_PAGE_BUTTON_BASE + source * EXTRACT_TARGET_COUNT + targetSlot + 1;
+    }
+
+    @Override public boolean clickMenuButton(Player player, int id) {
+        if (blockEntity == null || !stillValid(player)) return false;
+        if (id == PREVIOUS_TABS || id == NEXT_TABS) {
+            firstVisibleTab = Math.clamp(firstVisibleTab + (id == NEXT_TABS ? VISIBLE_TABS : -VISIBLE_TABS),
+                    0, WritingDeskBlockEntity.COLLECTIONS - VISIBLE_TABS);
+            return true;
+        } else if (id >= 0 && id < WritingDeskBlockEntity.COLLECTIONS) {
+            if (id < firstVisibleTab || id >= firstVisibleTab + VISIBLE_TABS) return false;
+            blockEntity.setActiveCollection(id);
+            selectedPage = 0;
+            selectedCollection = -1;
+            selectedSymbol = null;
+        } else if (id >= EXTRACT_PAGE_BUTTON_BASE
+                && id < EXTRACT_PAGE_BUTTON_BASE + PAGE_ADDRESS_COUNT * EXTRACT_TARGET_COUNT) {
+            int offset = id - EXTRACT_PAGE_BUTTON_BASE;
+            int source = offset / EXTRACT_TARGET_COUNT;
+            int targetSlot = offset % EXTRACT_TARGET_COUNT - 1;
+            if (!extractPage(source / NotebookContents.MAX_PAGES, source % NotebookContents.MAX_PAGES,
+                    targetSlot)) return false;
+        } else if (id >= MOVE_PAGE_BUTTON_BASE && id < MOVE_PAGE_BUTTON_BASE + PAGE_ADDRESS_COUNT * PAGE_ADDRESS_COUNT) {
+            int offset = id - MOVE_PAGE_BUTTON_BASE;
+            int source = offset / PAGE_ADDRESS_COUNT;
+            int target = offset % PAGE_ADDRESS_COUNT;
+            if (!movePage(source / NotebookContents.MAX_PAGES, source % NotebookContents.MAX_PAGES,
+                    target / NotebookContents.MAX_PAGES, target % NotebookContents.MAX_PAGES)) return false;
+        } else if (id >= PLACE_PAGE_BUTTON_BASE
+                && id < PLACE_PAGE_BUTTON_BASE + WritingDeskBlockEntity.COLLECTIONS * NotebookContents.MAX_PAGES) {
+            int offset = id - PLACE_PAGE_BUTTON_BASE;
+            if (!placeCarriedPage(offset / NotebookContents.MAX_PAGES, offset % NotebookContents.MAX_PAGES)) return false;
+        } else if (id >= PAGE_BUTTON_BASE && id < PAGE_BUTTON_BASE + NotebookContents.MAX_PAGES) {
+            selectedPage = id - PAGE_BUTTON_BASE;
+            selectedCollection = -1;
+            selectedSymbol = null;
+        } else if (id >= ALL_PAGE_BUTTON_BASE && id < ALL_PAGE_BUTTON_BASE + WritingDeskBlockEntity.COLLECTIONS * NotebookContents.MAX_PAGES) {
+            int offset = id - ALL_PAGE_BUTTON_BASE;
+            int collection = offset / NotebookContents.MAX_PAGES;
+            int page = offset % NotebookContents.MAX_PAGES;
+            if (pageAt(collection, page).isEmpty()) return false;
+            selectedCollection = collection;
+            selectedPage = page;
+            selectedSymbol = null;
+        } else if (id >= CATALOG_BUTTON_BASE && id < CATALOG_BUTTON_BASE + catalog.size()) {
+            List<SymbolDisplayMetadata> available = WritingDeskCatalog.available(blockEntity);
+            if (!catalog.equals(available)) {
+                refreshCatalog(available);
+                return false;
+            }
+            selectedSymbol = available.get(id - CATALOG_BUTTON_BASE).id();
+        } else return false;
+        refreshOutput();
+        return true;
+    }
+
+    private boolean placeCarriedPage(int collectionIndex, int pageIndex) {
+        // Resolve the actual storage position on the server, never a filtered list index.
+        ItemStack carried = getCarried();
+        if (clientSide || !storablePage(carried)) return false;
+        ItemStack collection = desk.getItem(collectionIndex);
+        if (CollationFolderItem.isCollection(collection)) {
+            if (pageIndex < 0 || pageIndex >= CollationFolderItem.capacity(collection)) return false;
+            var pages = new java.util.ArrayList<>(collection.getOrDefault(
+                    Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages());
+            while (pages.size() <= pageIndex) pages.add(ItemStack.EMPTY);
+            if (!pages.get(pageIndex).isEmpty()) return false;
+            pages.set(pageIndex, carried.copyWithCount(1));
+            ItemStack updated = collection.copy();
+            updated.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(pages));
+            desk.setItem(collectionIndex, updated);
+        } else return false;
+        carried.shrink(1);
+        setCarried(carried.isEmpty() ? ItemStack.EMPTY : carried);
+        selectedCollection = collectionIndex;
+        selectedPage = pageIndex;
+        selectedSymbol = null;
+        refreshCatalog();
+        broadcastChanges();
+        return true;
+    }
+
+    private boolean movePage(int sourceCollection, int sourcePage, int targetCollection, int targetPage) {
+        if (!getCarried().isEmpty() || sourceCollection == targetCollection && sourcePage == targetPage) return false;
+        ItemStack sourceBook = desk.getItem(sourceCollection);
+        ItemStack targetBook = desk.getItem(targetCollection);
+        boolean sourceNotebook = CollationFolderItem.isCollection(sourceBook);
+        boolean targetNotebook = CollationFolderItem.isCollection(targetBook);
+        if (sourceNotebook && sourcePage >= CollationFolderItem.capacity(sourceBook)
+                || targetNotebook && targetPage >= CollationFolderItem.capacity(targetBook)) return false;
+        if ((!sourceNotebook && (!sourceBook.is(Rivencraft.PAGE.get()) || sourcePage != 0))
+                || (!targetNotebook && (!targetBook.is(Rivencraft.PAGE.get()) || targetPage != 0))) return false;
+        var sourcePages = sourceNotebook ? new java.util.ArrayList<>(sourceBook.getOrDefault(
+                Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages()) : null;
+        if (sourceNotebook && (sourcePage >= sourcePages.size() || sourcePages.get(sourcePage).isEmpty())) return false;
+        ItemStack moving = sourceNotebook ? sourcePages.get(sourcePage) : sourceBook;
+        if (moving.getCount() != 1) return false;
+        if (!storablePage(moving)) return false;
+        if (!targetNotebook && targetBook.getCount() != 1) return false;
+        var targetPages = targetNotebook ? sourceCollection == targetCollection ? sourcePages
+                : new java.util.ArrayList<>(targetBook.getOrDefault(
+                        Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages()) : null;
+        if (targetNotebook) while (targetPages.size() <= targetPage) targetPages.add(ItemStack.EMPTY);
+        ItemStack displaced = targetNotebook ? targetPages.get(targetPage) : targetBook;
+        if (!displaced.isEmpty() && !storablePage(displaced)) return false;
+        if (targetNotebook) targetPages.set(targetPage, moving);
+        if (sourceNotebook) {
+            sourcePages.set(sourcePage, displaced);
+            ItemStack updatedSource = sourceBook.copy();
+            updatedSource.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(sourcePages));
+            desk.setItem(sourceCollection, updatedSource);
+        } else desk.setItem(sourceCollection, displaced.isEmpty() ? ItemStack.EMPTY : displaced.copyWithCount(1));
+        if (targetNotebook && sourceCollection != targetCollection) {
+            ItemStack updatedTarget = targetBook.copy();
+            updatedTarget.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(targetPages));
+            desk.setItem(targetCollection, updatedTarget);
+        } else if (!targetNotebook) desk.setItem(targetCollection, moving.copyWithCount(1));
+        selectedCollection = targetCollection;
+        selectedPage = targetPage;
+        selectedSymbol = null;
+        refreshCatalog();
+        broadcastChanges();
+        return true;
+    }
+
+    private boolean extractPage(int sourceCollection, int sourcePage, int targetSlot) {
+        if (!getCarried().isEmpty() || targetSlot < -1 || targetSlot >= slots.size()) return false;
+        ItemStack sourceBook = desk.getItem(sourceCollection);
+        boolean sourceNotebook = CollationFolderItem.isCollection(sourceBook);
+        if (sourceNotebook && sourcePage >= CollationFolderItem.capacity(sourceBook)) return false;
+        if (!sourceNotebook && (!sourceBook.is(Rivencraft.PAGE.get()) || sourcePage != 0)) return false;
+        var sourcePages = sourceNotebook ? new java.util.ArrayList<>(sourceBook.getOrDefault(
+                Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages()) : null;
+        if (sourceNotebook && (sourcePage >= sourcePages.size() || sourcePages.get(sourcePage).isEmpty())) return false;
+        ItemStack moving = sourceNotebook ? sourcePages.get(sourcePage).copyWithCount(1) : sourceBook.copyWithCount(1);
+        if (!sourceNotebook && sourceBook.getCount() != 1) return false;
+
+        if (targetSlot == -1) {
+            setCarried(moving);
+        } else {
+            if (targetSlot >= WritingDeskBlockEntity.COLLECTIONS && targetSlot < PLAYER_START) return false;
+            if (targetSlot < WritingDeskBlockEntity.COLLECTIONS && !storablePage(moving)) return false;
+            Slot target = slots.get(targetSlot);
+            if (!target.isActive() || !target.mayPlace(moving)) return false;
+            ItemStack current = target.getItem();
+            if (targetSlot < WritingDeskBlockEntity.COLLECTIONS && CollationFolderItem.isCollection(current)) {
+                var targetPages = targetSlot == sourceCollection ? sourcePages
+                        : new java.util.ArrayList<>(current.getOrDefault(
+                                Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages());
+                int position = -1;
+                for (int i = 0; i < CollationFolderItem.capacity(current); i++) {
+                    if (i >= targetPages.size() || targetPages.get(i).isEmpty()) {
+                        position = i;
+                        break;
+                    }
+                }
+                if (position < 0) return false;
+                while (targetPages.size() <= position) targetPages.add(ItemStack.EMPTY);
+                targetPages.set(position, moving);
+                if (targetSlot != sourceCollection) {
+                    ItemStack updatedTarget = current.copy();
+                    updatedTarget.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(targetPages));
+                    target.setByPlayer(updatedTarget);
+                }
+            } else if (current.isEmpty()) {
+                target.setByPlayer(moving);
+            } else if (targetSlot >= PLAYER_START && ItemStack.isSameItemSameComponents(current, moving)
+                    && current.getCount() < target.getMaxStackSize(moving)) {
+                target.setByPlayer(current.copyWithCount(current.getCount() + 1));
+            } else return false;
+        }
+
+        if (sourceNotebook) {
+            sourcePages.set(sourcePage, ItemStack.EMPTY);
+            ItemStack updatedSource = sourceBook.copy();
+            updatedSource.set(Rivencraft.NOTEBOOK_CONTENTS.get(), new NotebookContents(sourcePages));
+            desk.setItem(sourceCollection, updatedSource);
+        } else desk.setItem(sourceCollection, ItemStack.EMPTY);
+        selectedCollection = sourceCollection;
+        selectedPage = sourcePage;
+        selectedSymbol = null;
+        refreshCatalog();
+        broadcastChanges();
+        return true;
+    }
+
+    @Override public boolean stillValid(Player player) {
+        return blockEntity != null && blockEntity.stillValid(player);
+    }
+
+    @Override public ItemStack quickMoveStack(Player player, int index) {
+        if (!stillValid(player) || index < 0 || index >= slots.size()) return ItemStack.EMPTY;
+        if (index == COPY_RESULT) {
+            refreshOutput();
+            if (!canCopy()) return ItemStack.EMPTY;
+            ItemStack copy = selectedSource().copyWithCount(1);
+            ItemStack movingCopy = copy.copy();
+            if (!moveItemStackTo(movingCopy, PLAYER_START, slots.size(), true) || !movingCopy.isEmpty()) {
+                return ItemStack.EMPTY;
+            }
+            if (!blockEntity.consumeCopyMaterials()) return ItemStack.EMPTY;
+            refreshOutput();
+            return copy;
+        }
+        Slot slot = slots.get(index);
+        if (!slot.isActive()) return ItemStack.EMPTY;
+        if (!slot.hasItem()) return ItemStack.EMPTY;
+        ItemStack moving = slot.getItem();
+        ItemStack original = moving.copy();
+        if (index < COPY_RESULT) {
+            if (!moveItemStackTo(moving, PLAYER_START, slots.size(), true)) return ItemStack.EMPTY;
+        } else if (!moveIntoDesk(moving)) {
+            return ItemStack.EMPTY;
+        }
+        if (moving.isEmpty()) slot.setByPlayer(ItemStack.EMPTY);
+        else slot.setChanged();
+        return original;
+    }
+
+    private boolean moveIntoDesk(ItemStack moving) {
+        if (moving.is(Rivencraft.INK_VIAL.get())) return moveItemStackTo(moving,
+                WritingDeskBlockEntity.INK, WritingDeskBlockEntity.INK + 1, false);
+        if (CollationFolderItem.isCollection(moving)) return moveItemStackTo(moving, firstVisibleTab, firstVisibleTab + VISIBLE_TABS, false);
+        if (moving.is(Items.PAPER))
+            return moveItemStackTo(moving, WritingDeskBlockEntity.PAPER,
+                    WritingDeskBlockEntity.PAPER + 1, false);
+        if (storablePage(moving)) return moveItemStackTo(moving, firstVisibleTab, firstVisibleTab + VISIBLE_TABS, false);
+        return false;
+    }
+
+    private static boolean storablePage(ItemStack stack) {
+        return stack.is(Rivencraft.PAGE.get())
+                && PageItem.content(stack).kind() != PageContent.Kind.LINK_PANEL;
+    }
+
+    private ItemStack selectedSource() {
+        if (selectedSymbol != null) {
+            SymbolReference reference = new SymbolReference(selectedSymbol);
+            return PortSymbolPages.find(reference.id()) != null
+                    && blockEntity != null
+                    && WritingDeskCatalog.available(blockEntity).stream()
+                    .anyMatch(entry -> entry.id().equals(selectedSymbol))
+                    ? PageItem.createSymbolPage(reference) : ItemStack.EMPTY;
+        }
+        int collectionIndex = selectedCollection >= 0 ? selectedCollection
+                : blockEntity == null ? syncedActiveCollection : blockEntity.activeCollection();
+        return pageAt(collectionIndex, selectedPage);
+    }
+
+    private ItemStack pageAt(int collectionIndex, int pageIndex) {
+        if (collectionIndex < 0 || collectionIndex >= WritingDeskBlockEntity.COLLECTIONS
+                || pageIndex < 0 || pageIndex >= NotebookContents.MAX_PAGES) return ItemStack.EMPTY;
+        ItemStack collection = desk.getItem(collectionIndex);
+        if (collection.is(Rivencraft.PAGE.get())) return pageIndex == 0 ? collection : ItemStack.EMPTY;
+        if (CollationFolderItem.isCollection(collection)) {
+            if (pageIndex >= CollationFolderItem.capacity(collection)) return ItemStack.EMPTY;
+            List<ItemStack> pages = collection.getOrDefault(
+                    Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
+            return pageIndex < pages.size() ? pages.get(pageIndex) : ItemStack.EMPTY;
+        }
+        return ItemStack.EMPTY;
+    }
+
+    private boolean canCopy() {
+        ItemStack source = selectedSource();
+        return blockEntity != null && source.is(Rivencraft.PAGE.get())
+                && PageItem.content(source).kind() != PageContent.Kind.BLANK
+                && PageItem.content(source).kind() != PageContent.Kind.LINK_PANEL
+                && PageItem.isUsableWriting(source) && blockEntity.canConsumeCopyMaterials();
+    }
+
+    private void refreshOutput() {
+        if (clientSide) return;
+        if (blockEntity != null) blockEntity.setDisplayPage(selectedSource());
+        ItemStack preview = canCopy() ? selectedSource().copyWithCount(1) : ItemStack.EMPTY;
+        if (!ItemStack.matches(result.getItem(0), preview)) result.setItem(0, preview);
+    }
+
+    private void refreshCatalog() {
+        if (clientSide || blockEntity == null) return;
+        refreshCatalog(WritingDeskCatalog.available(blockEntity));
+    }
+
+    private void refreshCatalog(List<SymbolDisplayMetadata> current) {
+        if (clientSide || blockEntity == null) return;
+        if (!current.equals(catalog)) {
+            catalog = current;
+            if (serverViewer != null && serverViewer.containerMenu == this) {
+                PacketDistributor.sendToPlayer(serverViewer, new WritingDeskCatalogPayload(containerId, catalog));
+            }
+        }
+    }
+
+    @Override public void broadcastChanges() {
+        refreshCatalog();
+        refreshOutput();
+        super.broadcastChanges();
+    }
+
+    @Override public void clicked(int slotId, int button, net.minecraft.world.inventory.ContainerInput clickType,
+                                  Player player) {
+        if (!stillValid(player)) {
+            player.closeContainer();
+            return;
+        }
+        refreshCatalog();
+        refreshOutput();
+        if (slotId >= 0 && slotId < slots.size() && !slots.get(slotId).isActive()) return;
+        super.clicked(slotId, button, clickType, player);
+    }
+
+    private final class CopySlot extends Slot {
+        private CopySlot(Container container, int index, int x, int y) { super(container, index, x, y); }
+        @Override public boolean mayPlace(ItemStack stack) { return false; }
+        @Override public boolean mayPickup(Player player) {
+            return clientSide ? hasItem() : WritingDeskMenu.this.stillValid(player) && canCopy();
+        }
+        @Override public void onTake(Player player, ItemStack stack) {
+            if (!clientSide && blockEntity.consumeCopyMaterials()) {
+                refreshOutput();
+            }
+            super.onTake(player, stack);
+        }
+    }
+
+    private final class DeskSlot extends Slot {
+        private final int limit;
+        private DeskSlot(Container container, int index, int x, int y, int limit) {
+            super(container, index, x, y);
+            this.limit = limit;
+        }
+        @Override public boolean isActive() {
+            int slot = getContainerSlot();
+            return slot >= WritingDeskBlockEntity.COLLECTIONS
+                    || slot >= firstVisibleTab && slot < firstVisibleTab + VISIBLE_TABS;
+        }
+        @Override public boolean mayPickup(Player player) { return isActive(); }
+        @Override public boolean mayPlace(ItemStack stack) { return isActive() && container.canPlaceItem(getContainerSlot(), stack); }
+        @Override public int getMaxStackSize() { return limit; }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/network/PortBookNetworking.java

@@ -33,6 +33,7 @@ public final class PortBookNetworking {
 
     public static void registerPayloads(RegisterPayloadHandlersEvent event) {
         var registrar = event.registrar("1");
+        registrar.playToClient(WritingDeskCatalogPayload.TYPE, WritingDeskCatalogPayload.STREAM_CODEC);
         registrar.playToServer(BindLinkingBookPayload.TYPE, BindLinkingBookPayload.STREAM_CODEC,
                 (payload, context) -> {
                     if (context.player() instanceof ServerPlayer player) bind(player, payload);
@@ -82,7 +83,8 @@ public final class PortBookNetworking {
     private static void use(ServerPlayer player, UseLinkingBookPayload payload) {
         ItemStack stack = player.getItemInHand(hand(payload.offhand()));
         if (!stack.is(Rivencraft.LINKING_BOOK.get())) return;
-        String failure = LinkingBookItem.travel(player, stack);
+        String failure = net.dnorberg.rivencraft.item.PortHandheldTravel.travel(player,
+                hand(payload.offhand()), stack, () -> LinkingBookItem.travel(player, stack));
         if (failure != null) player.sendOverlayMessage(Component.literal(failure));
     }
 
@@ -110,8 +112,20 @@ public final class PortBookNetworking {
         if (title == null || title.isBlank() || title.length() > MAX_BOOK_TITLE_LENGTH) return null;
         long seed = player.getRandom().nextLong();
         net.dnorberg.rivencraft.age.PortBiomePlan biomePlan;
+        PortAgeTerrain terrain;
+        List<Identifier> generationPages;
         try {
-            biomePlan = PortAuthoredWriting.biomePlan(pages, player.level().getServer(), seed);
+            if (pages.isEmpty()) {
+                var random = PortRandomAgeSelection.select(player.level().getServer(), seed);
+                terrain = random.terrain();
+                biomePlan = random.biomes();
+                generationPages = pages;
+            } else {
+                var selected = net.dnorberg.rivencraft.writing.PortAuthoredTerrainSelection.select(player.level().getServer(), pages, seed);
+                terrain = selected.terrain();
+                biomePlan = selected.biomes();
+                generationPages = selected.generationPages();
+            }
         } catch (IllegalArgumentException exception) {
             player.sendOverlayMessage(Component.literal("Age writing unavailable: " + exception.getMessage()));
             return null;
@@ -128,25 +142,21 @@ public final class PortBookNetworking {
             id = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age/" + name);
         }
         try {
-            PortAgeTerrain terrain = PortAuthoredWriting.terrain(pages);
-            if (pages.isEmpty()) {
-                PortRandomAgeSelection.Selection random = PortRandomAgeSelection.select(server, seed);
-                terrain = random.terrain();
-                biomePlan = random.biomes();
-            }
             var environment = net.dnorberg.rivencraft.age.PortEnvironmentSelection.resolve(pages, seed, terrain);
             var randomFeatures = pages.isEmpty()
                     ? net.dnorberg.rivencraft.age.PortRandomFeatureSelection.select(server, seed, terrain, biomePlan) : null;
-            RuntimeAgeBackend.create(server, id, seed, biomePlan, terrain,
+            var level = RuntimeAgeBackend.create(server, id, seed, biomePlan, terrain,
-                    randomFeatures == null ? PortAuthoredWriting.rockPlan(pages, seed) : randomFeatures.rocks(),
+                    randomFeatures == null ? PortAuthoredWriting.rockPlan(generationPages, seed) : randomFeatures.rocks(),
-                    PortAuthoredWriting.vegetationPlan(pages),
+                    PortAuthoredWriting.vegetationPlan(generationPages),
-                    randomFeatures == null ? PortAuthoredWriting.dungeonCount(pages) : randomFeatures.dungeons(),
+                    randomFeatures == null ? PortAuthoredWriting.dungeonCount(generationPages) : randomFeatures.dungeons(),
-                    randomFeatures == null ? PortAuthoredWriting.lakePlan(pages, seed) : randomFeatures.lakes(),
+                    randomFeatures == null ? PortAuthoredWriting.lakePlan(generationPages, seed) : randomFeatures.lakes(),
-                    randomFeatures == null ? PortAuthoredWriting.terrainFeaturePlan(pages, seed) : randomFeatures.terrain(),
+                    randomFeatures == null ? PortAuthoredWriting.terrainFeaturePlan(generationPages, seed) : randomFeatures.terrain(),
                     environment.weather(), environment.lighting(), environment.sky(),
                     net.dnorberg.rivencraft.age.PortAgeColors.resolve(pages, seed),
                     net.dnorberg.rivencraft.age.PortDayCycle.resolve(pages, seed,
                             net.dnorberg.rivencraft.age.PortDayCycle.nativeTicks(server.overworld())));
+            net.dnorberg.rivencraft.age.PortAcceleratedTicks.configure(level,
+                    net.dnorberg.rivencraft.age.PortAcceleratedTicks.pageCount(pages));
         } catch (IllegalArgumentException | IllegalStateException exception) {
             player.sendOverlayMessage(Component.literal("Age creation failed: " + exception.getMessage()));
             return null;
@@ -160,13 +170,19 @@ public final class PortBookNetworking {
         Identifier id = stack.get(Rivencraft.AGE_BOOK_ID.get());
         if (id == null) return;
         ServerLevel source = player.level();
+        LinkBookTarget returnTarget = LinkBookTarget.at(player);
         Vec3 departure = player.position();
         Vec3 incoming = player.getDeltaMovement();
-        String failure = PortAgeTravel.enter(player, id);
+        String failure = net.dnorberg.rivencraft.item.PortHandheldTravel.travel(player,
+                hand(payload.offhand()), stack, () -> {
+                    String result = PortAgeTravel.enter(player, id);
+                    if (result == null) LinkingBookItem.applySuccessfulLink(player,
+                            stack.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE),
+                            source, departure, incoming, player.getYRot());
+                    return result;
+                });
         if (failure != null) player.sendOverlayMessage(Component.literal(failure));
-        else LinkingBookItem.applySuccessfulLink(player,
+        else net.dnorberg.rivencraft.age.PortReturnLinks.afterSuccessfulTravel(player, id, returnTarget);
-                stack.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE),
-                source, departure, incoming, player.getYRot());
     }
 
     private static InteractionHand hand(boolean offhand) {

ports/mc263/src/main/java/net/dnorberg/rivencraft/network/WritingDeskCatalogPayload.java

@@ -0,0 +1,26 @@
+package net.dnorberg.rivencraft.network;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.SymbolDisplayMetadata;
+import net.dnorberg.rivencraft.writing.WritingDeskCatalog;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.Identifier;
+
+/** Current server-approved symbols from this open Writing Desk menu. */
+public record WritingDeskCatalogPayload(int containerId, List<SymbolDisplayMetadata> symbols)
+        implements CustomPacketPayload {
+    public static final Type<WritingDeskCatalogPayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "writing_desk_catalog"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, WritingDeskCatalogPayload> STREAM_CODEC =
+            StreamCodec.of(
+                    (buffer, payload) -> {
+                        buffer.writeVarInt(payload.containerId());
+                        WritingDeskCatalog.write(buffer, payload.symbols());
+                    },
+                    buffer -> new WritingDeskCatalogPayload(buffer.readVarInt(), WritingDeskCatalog.read(buffer)));
+
+    @Override public Type<? extends CustomPacketPayload> type() { return TYPE; }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/registry/ModCreativeTabs.java

@@ -32,6 +32,11 @@ public final class ModCreativeTabs {
                     output.accept(Rivencraft.INK_VIAL.get());
                     output.accept(Rivencraft.BOOK_BINDER_ITEM.get());
                     output.accept(Rivencraft.INK_MIXER_ITEM.get());
+                    output.accept(Rivencraft.WRITING_DESK_ITEM.get());
+                    output.accept(Rivencraft.NOTEBOOK.get());
+                    output.accept(Rivencraft.COLLATION_FOLDER.get());
+                    output.accept(Rivencraft.SEALED_NOTEBOOK.get());
+                    creativeSymbolPortfolios(parameters.holders()).forEach(output::accept);
                 })
                 .build());
         TABS.register("rivencraft_link_pages", () -> CreativeModeTab.builder()
@@ -65,6 +70,15 @@ public final class ModCreativeTabs {
     private ModCreativeTabs() {
     }
 
+    public static java.util.List<net.minecraft.world.item.ItemStack> creativeSymbolPortfolios(
+            net.minecraft.core.HolderLookup.Provider registries) {
+        var portfolios = new java.util.ArrayList<net.minecraft.world.item.ItemStack>();
+        for (String category : PortSymbolPages.categories()) portfolios.addAll(
+                net.dnorberg.rivencraft.item.SymbolPortfolioItem.createVolumes(
+                        net.minecraft.resources.Identifier.parse(category), PortSymbolPages.pages(category, registries)));
+        return java.util.List.copyOf(portfolios);
+    }
+
     public static void register(IEventBus modEventBus) {
         TABS.register(modEventBus);
     }

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/NotebookContents.java

@@ -0,0 +1,90 @@
+package net.dnorberg.rivencraft.writing;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.DataResult;
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.world.item.ItemStack;
+
+/** A bounded, position-preserving collection of Page stacks stored on a Notebook item. */
+public record NotebookContents(List<ItemStack> pages) {
+    // Legacy did not impose a book-page cap. Our fixed-slot binder persists slot IDs
+    // as unsigned bytes; 252 page positions (after its three input slots) fit safely.
+    public static final int MAX_PAGES = 252;
+    public static final NotebookContents EMPTY = new NotebookContents(List.of());
+    public static final Codec<NotebookContents> CODEC = ItemStack.OPTIONAL_CODEC.listOf()
+            .validate(NotebookContents::validate)
+            .xmap(NotebookContents::new, NotebookContents::pages);
+    public static final StreamCodec<RegistryFriendlyByteBuf, NotebookContents> STREAM_CODEC = StreamCodec.of(
+            NotebookContents::encode, NotebookContents::decode);
+
+    public NotebookContents {
+        if (pages.size() > MAX_PAGES) {
+            throw new IllegalArgumentException("Notebook exceeds " + MAX_PAGES + " page positions");
+        }
+        List<ItemStack> copies = new ArrayList<>(pages.size());
+        for (ItemStack page : pages) {
+            validatePage(page).getOrThrow();
+            copies.add(page.copy());
+        }
+        pages = List.copyOf(copies);
+    }
+
+    public int pageCount() {
+        return (int)pages.stream().filter(page -> !page.isEmpty()).count();
+    }
+
+    public int unresolvedCount() {
+        return (int)pages.stream()
+                .filter(page -> !page.isEmpty()
+                        && page.has(Rivencraft.SYMBOL_PAGE_ID.get())
+                        && PortSymbolPages.find(page.get(Rivencraft.SYMBOL_PAGE_ID.get())) == null)
+                .count();
+    }
+
+    private static DataResult<List<ItemStack>> validate(List<ItemStack> pages) {
+        if (pages.size() > MAX_PAGES) {
+            return DataResult.error(() -> "Notebook exceeds " + MAX_PAGES + " page positions");
+        }
+        for (ItemStack page : pages) {
+            DataResult<ItemStack> result = validatePage(page);
+            if (result.error().isPresent()) {
+                return DataResult.error(() -> result.error().orElseThrow().message());
+            }
+        }
+        return DataResult.success(pages);
+    }
+
+    private static DataResult<ItemStack> validatePage(ItemStack page) {
+        if (page.isEmpty()) {
+            return DataResult.success(page);
+        }
+        if (!page.is(Rivencraft.PAGE.get())) {
+            return DataResult.error(() -> "Notebook contains a non-Page item");
+        }
+        return page.getCount() == 1
+                ? DataResult.success(page)
+                : DataResult.error(() -> "Notebook Page stacks must contain exactly one item");
+    }
+
+    private static void encode(RegistryFriendlyByteBuf buffer, NotebookContents contents) {
+        ByteBufCodecs.VAR_INT.encode(buffer, contents.pages.size());
+        contents.pages.forEach(page -> ItemStack.OPTIONAL_STREAM_CODEC.encode(buffer, page));
+    }
+
+    private static NotebookContents decode(RegistryFriendlyByteBuf buffer) {
+        int size = ByteBufCodecs.VAR_INT.decode(buffer);
+        if (size < 0 || size > MAX_PAGES) {
+            throw new IllegalArgumentException("Invalid Notebook page count " + size);
+        }
+        List<ItemStack> pages = new ArrayList<>(size);
+        for (int index = 0; index < size; index++) {
+            pages.add(ItemStack.OPTIONAL_STREAM_CODEC.decode(buffer));
+        }
+        return new NotebookContents(pages);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/PageContent.java

@@ -0,0 +1,95 @@
+package net.dnorberg.rivencraft.writing;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.DataResult;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import io.netty.buffer.ByteBuf;
+import java.util.Locale;
+import java.util.Objects;
+import java.util.Optional;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+
+/** Persistent contents of a Page item. Unknown symbols remain explicit and recoverable. */
+public record PageContent(Kind kind, Optional<SymbolReference> symbol) {
+    public static final PageContent BLANK = new PageContent(Kind.BLANK, Optional.empty());
+    public static final PageContent LINK_PANEL = new PageContent(Kind.LINK_PANEL, Optional.empty());
+    private static final Codec<Kind> KIND_CODEC = Codec.STRING.comapFlatMap(
+            value -> {
+                try {
+                    return DataResult.success(Kind.valueOf(value.toUpperCase(Locale.ROOT)));
+                } catch (IllegalArgumentException exception) {
+                    return DataResult.error(() -> "Unknown page content kind: " + value);
+                }
+            },
+            value -> value.name().toLowerCase(Locale.ROOT)
+    );
+    private static final Codec<PageContent> RECORD_CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            KIND_CODEC.fieldOf("kind").forGetter(PageContent::kind),
+            SymbolReference.CODEC.optionalFieldOf("symbol").forGetter(PageContent::symbol)
+    ).apply(instance, PageContent::new));
+    public static final Codec<PageContent> CODEC = RECORD_CODEC.flatXmap(PageContent::validate, PageContent::validate);
+    public static final StreamCodec<ByteBuf, PageContent> STREAM_CODEC = StreamCodec.of(
+            PageContent::encode, PageContent::decode);
+
+    public PageContent {
+        Objects.requireNonNull(kind, "kind");
+        symbol = Objects.requireNonNull(symbol, "symbol");
+        boolean needsSymbol = kind == Kind.SYMBOL || kind == Kind.UNRESOLVED_SYMBOL;
+        if (needsSymbol != symbol.isPresent()) {
+            throw new IllegalArgumentException("Page contents do not match kind " + kind);
+        }
+    }
+
+    public static PageContent symbol(SymbolReference symbol) {
+        return new PageContent(Kind.SYMBOL, Optional.of(symbol));
+    }
+
+    public static PageContent unresolved(SymbolReference symbol) {
+        return new PageContent(Kind.UNRESOLVED_SYMBOL, Optional.of(symbol));
+    }
+
+    /** Re-resolves persisted data against the authoritative current server catalog. */
+    public PageContent resolve() {
+        if (kind != Kind.SYMBOL && kind != Kind.UNRESOLVED_SYMBOL) {
+            return this;
+        }
+        SymbolReference reference = symbol.orElseThrow();
+        return PortSymbolPages.find(reference.id()) != null ? symbol(reference) : unresolved(reference);
+    }
+
+    public boolean isResolvedSymbol() {
+        return kind == Kind.SYMBOL;
+    }
+
+    private static DataResult<PageContent> validate(PageContent content) {
+        boolean needsSymbol = content.kind == Kind.SYMBOL || content.kind == Kind.UNRESOLVED_SYMBOL;
+        return needsSymbol == content.symbol.isPresent()
+                ? DataResult.success(content)
+                : DataResult.error(() -> "Page contents do not match kind " + content.kind);
+    }
+
+    private static void encode(ByteBuf buffer, PageContent content) {
+        ByteBufCodecs.VAR_INT.encode(buffer, content.kind.ordinal());
+        content.symbol.ifPresent(reference -> SymbolReference.STREAM_CODEC.encode(buffer, reference));
+    }
+
+    private static PageContent decode(ByteBuf buffer) {
+        int ordinal = ByteBufCodecs.VAR_INT.decode(buffer);
+        if (ordinal < 0 || ordinal >= Kind.values().length) {
+            throw new IllegalArgumentException("Unknown page content kind ordinal " + ordinal);
+        }
+        Kind kind = Kind.values()[ordinal];
+        Optional<SymbolReference> symbol = kind == Kind.SYMBOL || kind == Kind.UNRESOLVED_SYMBOL
+                ? Optional.of(SymbolReference.STREAM_CODEC.decode(buffer))
+                : Optional.empty();
+        return new PageContent(kind, symbol);
+    }
+
+    public enum Kind {
+        BLANK,
+        SYMBOL,
+        UNRESOLVED_SYMBOL,
+        LINK_PANEL
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/PortAuthoredTerrainSelection.java

@@ -0,0 +1,47 @@
+package net.dnorberg.rivencraft.writing;
+
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.age.PortAgeTerrain;
+import net.dnorberg.rivencraft.age.PortBiomePlan;
+import net.dnorberg.rivencraft.age.PortRandomAgeSelection;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+
+/** Root AgeRuntimeProfiles.selectForWriting, limited to currently supported port combinations. */
+public final class PortAuthoredTerrainSelection {
+    private PortAuthoredTerrainSelection() {}
+
+    public record Selection(PortAgeTerrain terrain, List<Identifier> generationPages, PortBiomePlan biomes) {
+        public Selection { generationPages = List.copyOf(generationPages); }
+    }
+
+    public static Selection select(MinecraftServer server, List<Identifier> pages, long seed) {
+        var explicit = PortAuthoredWriting.explicitTerrain(pages);
+        if (explicit != null) return compile(server, pages, seed, explicit);
+        var preferred = PortRandomAgeSelection.terrain(seed);
+        try {
+            return compile(server, pages, seed, preferred);
+        } catch (IllegalArgumentException ignored) {
+            // Match root's stable profile-ID fallback rather than rerolling the seed.
+        }
+        var compatible = new ArrayList<Selection>();
+        for (var terrain : PortRandomAgeSelection.terrains()) {
+            if (terrain == preferred) continue;
+            try { compatible.add(compile(server, pages, seed, terrain)); }
+            catch (IllegalArgumentException ignored) { }
+        }
+        if (compatible.isEmpty()) throw new IllegalArgumentException("No supported terrain can host this book's pages");
+        return compatible.get(Math.floorMod(Long.hashCode(seed), compatible.size()));
+    }
+
+    private static Selection compile(MinecraftServer server, List<Identifier> pages, long seed, PortAgeTerrain terrain) {
+        if (!PortAuthoredWriting.supportsOnTerrain(pages, terrain, seed))
+            throw new IllegalArgumentException("Unsupported pages for " + terrain + " terrain");
+        var resolved = PortAuthoredWriting.withTerrain(pages, terrain);
+        // Also preflight registry-backed biome restrictions, so an automatic Cave
+        // choice cannot turn supplied surface biome pages into an unusable book.
+        var biomes = PortAuthoredWriting.biomePlan(resolved, server, seed);
+        return new Selection(terrain, resolved, biomes);
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/PortAuthoredWriting.java

@@ -57,6 +57,7 @@ public final class PortAuthoredWriting {
         if (entry == null) return false;
         if (net.dnorberg.rivencraft.age.PortAgeColors.isModifier(page)
                 || net.dnorberg.rivencraft.age.PortDayCycle.supports(page)) return true;
+        if (page.equals(net.dnorberg.rivencraft.age.PortAcceleratedTicks.PAGE)) return true;
         if (isTerrain(page) || controller(page) != null || PortWeatherMode.forPage(page) != null
                 || PortLighting.forPage(page) != null || PortSkyStyle.forPage(page) != null) return true;
         if (entry.category().equals("rivencraft:biome") && PortRegistryPages.biomeId(page) != null) return true;
@@ -72,11 +73,35 @@ public final class PortAuthoredWriting {
 
     /** A page never disappears into an Age unless this port can apply its effect. */
     public static boolean supports(List<Identifier> pages) {
+        if (pages.stream().noneMatch(PortAuthoredWriting::isTerrain))
+            return net.dnorberg.rivencraft.age.PortRandomAgeSelection.terrains().stream()
+                    .anyMatch(terrain -> supportsOnTerrain(pages, terrain, 0));
         try {
             return supportsExplicit(PortMaterialCompletion.complete(pages, 0));
         } catch (IllegalArgumentException exception) { return false; }
     }
 
+    static boolean supportsOnTerrain(List<Identifier> pages, PortAgeTerrain terrain, long seed) {
+        try {
+            return supportsExplicit(PortMaterialCompletion.complete(withTerrain(pages, terrain), seed));
+        } catch (IllegalArgumentException exception) { return false; }
+    }
+
+    static List<Identifier> withTerrain(List<Identifier> pages, PortAgeTerrain terrain) {
+        if (pages.stream().anyMatch(PortAuthoredWriting::isTerrain)) return List.copyOf(pages);
+        var resolved = new ArrayList<>(pages);
+        // Append internally so original material/color/controller indices stay stable.
+        resolved.add(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID,
+                "terrain/" + terrain.name().toLowerCase(java.util.Locale.ROOT)));
+        return List.copyOf(resolved);
+    }
+
+    static PortAgeTerrain explicitTerrain(List<Identifier> pages) {
+        return pages.stream().filter(PortAuthoredWriting::isTerrain).findFirst()
+                .map(page -> PortAgeTerrain.valueOf(page.getPath().substring(8).toUpperCase(java.util.Locale.ROOT)))
+                .orElse(null);
+    }
+
     private static boolean supportsExplicit(List<Identifier> pages) {
         if (!net.dnorberg.rivencraft.age.PortAgeColors.validNumbers(pages)) return false;
         if (!net.dnorberg.rivencraft.age.PortDayCycle.validWriting(pages)) return false;
@@ -104,6 +129,8 @@ public final class PortAuthoredWriting {
             if (net.dnorberg.rivencraft.age.PortAgeColors.isModifier(page)
                     || net.dnorberg.rivencraft.age.PortDayCycle.supports(page)) {
                 // Shared colors target Sky, Ambient Light Color or Normal Time; trailing colors tint the sky.
+            } else if (page.equals(net.dnorberg.rivencraft.age.PortAcceleratedTicks.PAGE)) {
+                // Every Accelerated page adds random-tick attempts; it is not a controller.
             } else if (isTerrain(page) && !terrain) {
                 terrain = true;
             } else if (PortSkyStyle.forPage(page) != null && sky++ == 0) {
@@ -321,17 +348,18 @@ public final class PortAuthoredWriting {
 
     /** Resolves all authored biomes from the active registry before creating a level. */
     public static PortBiomePlan biomePlan(List<Identifier> pages, HolderLookup.Provider registries) {
-        return biomePlan(pages, registries, 0, null);
+        return biomePlan(pages, registries, 0, null, null);
     }
 
     /** Creation-only completion; the saved plan never rerolls on load or reseed. */
     public static PortBiomePlan biomePlan(List<Identifier> pages, net.minecraft.server.MinecraftServer server, long seed) {
         return biomePlan(pages, server.registryAccess(), seed,
-                net.dnorberg.rivencraft.age.PortRandomAgeSelection.eligibleBiomes(server, terrain(pages)));
+                net.dnorberg.rivencraft.age.PortRandomAgeSelection.eligibleBiomes(server, terrain(pages)),
+                net.dnorberg.rivencraft.age.PortRandomAgeSelection.distribution(seed));
     }
 
     private static PortBiomePlan biomePlan(List<Identifier> pages, HolderLookup.Provider registries,
-                                          long seed, List<Identifier> available) {
+                                          long seed, List<Identifier> available, PortBiomePlan.Distribution fallback) {
         if (!supports(pages)) throw new IllegalArgumentException(
                 "Unsupported terrain or biome-page combination in this port slice");
         List<Identifier> biomes = new ArrayList<>();
@@ -364,8 +392,22 @@ public final class PortAuthoredWriting {
             throw new IllegalArgumentException("Vegetation pages need at least one surface Overworld biome");
         if (pages.contains(PortTerrainFeaturePlan.DENSE_ORES) && !biomes.isEmpty() && !hasOreBiome)
             throw new IllegalArgumentException("Dense Ores needs at least one biome with registered ore placements");
-        if (distribution == PortBiomePlan.Distribution.NATIVE)
+        if (distribution == null && fallback != null) {
-            return new PortBiomePlan(distribution, List.of());
+            distribution = fallback;
+            // Root's authored-pool fallback never discards supplied biome pages.
+            if (pages.contains(VOID_TERRAIN) && biomes.isEmpty()) distribution = PortBiomePlan.Distribution.SINGLE;
+            if (!biomes.isEmpty() && (pages.contains(VOID_TERRAIN)
+                    || distribution == PortBiomePlan.Distribution.NATIVE
+                    || distribution == PortBiomePlan.Distribution.SINGLE && biomes.size() > 1))
+                distribution = biomes.size() == 1 ? PortBiomePlan.Distribution.SINGLE : biomes.size() == 2
+                        ? PortBiomePlan.Distribution.TILED : PortBiomePlan.Distribution.MEDIUM;
+        }
+        if (distribution == PortBiomePlan.Distribution.NATIVE) {
+            var nativePool = caveTerrain
+                    ? (available != null ? available : net.dnorberg.rivencraft.age.PortRandomAgeSelection.caveBiomes(registries))
+                    : List.<Identifier>of();
+            return new PortBiomePlan(distribution, nativePool);
+        }
         if (distribution != null && available != null) {
             int minimum = distribution == PortBiomePlan.Distribution.SINGLE ? 1 : 2;
             int target = minimum;
@@ -374,6 +416,9 @@ public final class PortAuthoredWriting {
                 while (target < available.size() && random.nextInt(3) != 0) target++;
             }
             var distinct = new java.util.HashSet<>(biomes);
+            PortStructureBiomeCompletion.complete(pages, registries, available, !biomes.isEmpty(),
+                    distribution, biomes, distinct, seed);
+            target = Math.max(target, distinct.size());
             // Void may retain authored weather/season biomes, but must not gain
             // an unrequested The Void biome just to fill a multi-biome controller.
             var filler = new ArrayList<>(pages.contains(VOID_TERRAIN) && !biomes.isEmpty() ? List.<Identifier>of() : available);

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/PortRegistryPages.java

@@ -103,6 +103,7 @@ public final class PortRegistryPages {
 
     private static String materialCategory(Block block) {
         if (block == null || block == Blocks.AIR || block == Blocks.CAVE_AIR || block == Blocks.VOID_AIR
+                || block == Rivencraft.CLOUD_PLATFORM.get()
                 || block instanceof EntityBlock || block.defaultBlockState().hasBlockEntity()) return null;
         var state = block.defaultBlockState();
         var fluid = state.getFluidState();

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/PortStructureBiomeCompletion.java

@@ -0,0 +1,54 @@
+package net.dnorberg.rivencraft.writing;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.Random;
+import java.util.Set;
+import net.dnorberg.rivencraft.age.PortBiomePlan;
+import net.dnorberg.rivencraft.age.PortStructurePages;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.resources.Identifier;
+
+/** Root AgeBiomeSelection.completeStructureBiomes, before ordinary minimum filling. */
+final class PortStructureBiomeCompletion {
+    private PortStructureBiomeCompletion() {}
+
+    static void complete(List<Identifier> pages, HolderLookup.Provider registries, List<Identifier> available,
+                         boolean hasAuthoredBiomes, PortBiomePlan.Distribution distribution,
+                         List<Identifier> selected, Set<Identifier> distinct, long seed) {
+        var requirements = pages.stream().filter(PortStructurePages::supports).distinct()
+                .map(page -> PortStructurePages.compatibleBiomes(page, registries))
+                .filter(requirement -> !requirement.isEmpty()).toList();
+        if (requirements.isEmpty()) return;
+        if (distribution == PortBiomePlan.Distribution.SINGLE) {
+            if (hasAuthoredBiomes) return;
+            var candidates = available.stream()
+                    .filter(candidate -> requirements.stream().allMatch(requirement -> requirement.contains(candidate)))
+                    .toList();
+            if (candidates.isEmpty()) return;
+            Identifier biome = choose(candidates, seed, 0x5354525543544249L);
+            selected.clear();
+            distinct.clear();
+            selected.add(biome);
+            distinct.add(biome);
+            return;
+        }
+        for (int index = 0; index < requirements.size(); index++) {
+            var requirement = requirements.get(index);
+            if (selected.stream().anyMatch(requirement::contains)) continue;
+            var candidates = available.stream().filter(requirement::contains)
+                    .filter(candidate -> !distinct.contains(candidate)).toList();
+            if (candidates.isEmpty()) continue;
+            Identifier biome = choose(candidates, seed, 0x5354525543544249L + index);
+            selected.add(biome);
+            distinct.add(biome);
+        }
+    }
+
+    private static Identifier choose(List<Identifier> candidates, long seed, long salt) {
+        var shuffled = new ArrayList<>(candidates);
+        Collections.shuffle(shuffled, new Random(seed ^ salt));
+        return shuffled.getFirst();
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/PortSymbolNumerals.java

@@ -4,6 +4,17 @@ package net.dnorberg.rivencraft.writing;
 public final class PortSymbolNumerals {
     private PortSymbolNumerals() {}
 
+    public static int[] digitsFor(int number) {
+        if (number < 0) throw new IllegalArgumentException("Numeral must be non-negative");
+        if (number < 25) return new int[] {number};
+        int count = 0;
+        for (int remaining = number; remaining > 0; remaining /= 25) count++;
+        int[] digits = new int[count];
+        for (int remaining = number, index = count - 1; index >= 0; index--, remaining /= 25)
+            digits[index] = remaining % 25;
+        return digits;
+    }
+
     public static int[] componentsForDigit(int digit) {
         if (digit < 0 || digit >= 25) throw new IllegalArgumentException("Base-25 digit must be in [0, 24]");
         if (digit == 0) return new int[] {1};

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/PortSymbolPages.java

@@ -37,6 +37,15 @@ public final class PortSymbolPages {
         return List.copyOf(categories);
     }
 
+    /** Same bundled, non-biome/material/non-corrupted pool as 1.21.1's booster. */
+    public static List<Identifier> sealedCandidateIds() {
+        return ENTRIES.values().stream().filter(entry -> entry.id().getNamespace().equals(Rivencraft.MOD_ID)
+                        && !entry.id().getPath().startsWith("block/")
+                        && !entry.id().getPath().startsWith("biome/")
+                        && !entry.category().equals("rivencraft:corrupted"))
+                .map(Entry::id).sorted().toList();
+    }
+
     public static List<ItemStack> pages(String category, HolderLookup.Provider registries) {
         List<ItemStack> pages = new ArrayList<>();
         ENTRIES.values().stream().filter(entry -> entry.category().equals(category))

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/SymbolDisplayMetadata.java

@@ -0,0 +1,48 @@
+package net.dnorberg.rivencraft.writing;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import io.netty.buffer.ByteBuf;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.resources.Identifier;
+
+/** Client-safe symbol presentation selected by the authoritative server catalog. */
+public record SymbolDisplayMetadata(
+        Identifier id,
+        String nameTranslationKey,
+        String descriptionTranslationKey,
+        Identifier category,
+        boolean resolved,
+        String poem
+) {
+    public static final Codec<SymbolDisplayMetadata> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Identifier.CODEC.fieldOf("id").forGetter(SymbolDisplayMetadata::id),
+            Codec.STRING.fieldOf("name").forGetter(SymbolDisplayMetadata::nameTranslationKey),
+            Codec.STRING.fieldOf("description").forGetter(SymbolDisplayMetadata::descriptionTranslationKey),
+            Identifier.CODEC.fieldOf("category").forGetter(SymbolDisplayMetadata::category),
+            Codec.BOOL.fieldOf("resolved").forGetter(SymbolDisplayMetadata::resolved),
+            Codec.STRING.optionalFieldOf("poem", "").forGetter(SymbolDisplayMetadata::poem)
+    ).apply(instance, SymbolDisplayMetadata::new));
+    public static final StreamCodec<ByteBuf, SymbolDisplayMetadata> STREAM_CODEC = StreamCodec.composite(
+            Identifier.STREAM_CODEC, SymbolDisplayMetadata::id,
+            ByteBufCodecs.STRING_UTF8, SymbolDisplayMetadata::nameTranslationKey,
+            ByteBufCodecs.STRING_UTF8, SymbolDisplayMetadata::descriptionTranslationKey,
+            Identifier.STREAM_CODEC, SymbolDisplayMetadata::category,
+            ByteBufCodecs.BOOL, SymbolDisplayMetadata::resolved,
+            ByteBufCodecs.STRING_UTF8, SymbolDisplayMetadata::poem,
+            SymbolDisplayMetadata::new
+    );
+
+    public static SymbolDisplayMetadata unresolved(SymbolReference reference) {
+        return new SymbolDisplayMetadata(
+                reference.id(),
+                "symbol.rivencraft.unresolved",
+                "symbol.rivencraft.unresolved.description",
+                Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "unresolved"),
+                false,
+                ""
+        );
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/SymbolReference.java

@@ -0,0 +1,24 @@
+package net.dnorberg.rivencraft.writing;
+
+import com.mojang.serialization.Codec;
+import io.netty.buffer.ByteBuf;
+import java.util.Objects;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.resources.Identifier;
+
+/** Stable namespaced identity for one writing symbol. */
+public record SymbolReference(Identifier id) {
+    public static final Codec<SymbolReference> CODEC = Identifier.CODEC.xmap(
+            SymbolReference::new, SymbolReference::id);
+    public static final StreamCodec<ByteBuf, SymbolReference> STREAM_CODEC = Identifier.STREAM_CODEC.map(
+            SymbolReference::new, SymbolReference::id);
+
+    public SymbolReference {
+        Objects.requireNonNull(id, "id");
+    }
+
+    /** Remains useful when the defining data pack has been removed. */
+    public String unresolvedName() {
+        return id.toString();
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/writing/WritingDeskCatalog.java

@@ -0,0 +1,64 @@
+package net.dnorberg.rivencraft.writing;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import java.util.ArrayList;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import net.dnorberg.rivencraft.block.entity.WritingDeskBlockEntity;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.item.CollationFolderItem;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.item.ItemStack;
+
+/** A bounded, server-derived view of symbols physically present in the desk. */
+public final class WritingDeskCatalog {
+    private static final int MAX_ENTRIES = WritingDeskBlockEntity.COLLECTIONS * NotebookContents.MAX_PAGES;
+
+    private WritingDeskCatalog() {}
+
+    public static List<SymbolDisplayMetadata> available(WritingDeskBlockEntity desk) {
+        Map<Identifier, SymbolDisplayMetadata> unique = new HashMap<>();
+        for (int slot = 0; slot < WritingDeskBlockEntity.COLLECTIONS; slot++) {
+            ItemStack collection = desk.getItem(slot);
+            if (collection.is(Rivencraft.PAGE.get())) add(unique, collection);
+            if (CollationFolderItem.isCollection(collection)) {
+                List<ItemStack> pages = collection.getOrDefault(
+                        Rivencraft.NOTEBOOK_CONTENTS.get(), NotebookContents.EMPTY).pages();
+                pages.forEach(page -> add(unique, page));
+            }
+        }
+        return unique.values().stream()
+                .sorted(Comparator.comparing((SymbolDisplayMetadata symbol) -> symbol.category().toString())
+                        .thenComparing(symbol -> symbol.id().toString()))
+                .toList();
+    }
+
+    private static void add(Map<Identifier, SymbolDisplayMetadata> unique, ItemStack page) {
+        if (!page.is(Rivencraft.PAGE.get())) return;
+        PageContent content = PageItem.content(page).resolve();
+        if (content.kind() != PageContent.Kind.SYMBOL) return;
+        SymbolReference reference = content.symbol().orElseThrow();
+        var entry = PortSymbolPages.find(reference.id());
+        if (entry != null) unique.put(reference.id(), new SymbolDisplayMetadata(entry.id(),
+                entry.nameKey(), entry.descriptionKey(), Identifier.parse(entry.category()), true, entry.poem()));
+    }
+
+    public static void write(RegistryFriendlyByteBuf buffer, List<SymbolDisplayMetadata> entries) {
+        if (entries.size() > MAX_ENTRIES) throw new IllegalArgumentException("Desk symbol catalog exceeds limit");
+        buffer.writeVarInt(entries.size());
+        entries.forEach(entry -> SymbolDisplayMetadata.STREAM_CODEC.encode(buffer, entry));
+    }
+
+    public static List<SymbolDisplayMetadata> read(RegistryFriendlyByteBuf buffer) {
+        int count = buffer.readVarInt();
+        if (count < 0 || count > MAX_ENTRIES) throw new IllegalArgumentException("Invalid desk symbol count " + count);
+        List<SymbolDisplayMetadata> entries = new ArrayList<>(count);
+        for (int index = 0; index < count; index++) {
+            entries.add(SymbolDisplayMetadata.STREAM_CODEC.decode(buffer));
+        }
+        return List.copyOf(entries);
+    }
+}

ports/mc263/src/main/resources/assets/rivencraft/items/collation_folder.json

@@ -0,0 +1 @@
+{"model":{"type":"minecraft:model","model":"rivencraft:item/collation_folder"}}

ports/mc263/src/main/resources/assets/rivencraft/items/notebook.json

@@ -0,0 +1 @@
+{"model":{"type":"minecraft:model","model":"rivencraft:item/notebook"}}

ports/mc263/src/main/resources/assets/rivencraft/items/sealed_notebook.json

@@ -0,0 +1 @@
+{"model":{"type":"minecraft:model","model":"rivencraft:item/sealed_notebook"}}

ports/mc263/src/main/resources/assets/rivencraft/items/symbol_portfolio.json

@@ -0,0 +1 @@
+{"model":{"type":"minecraft:model","model":"rivencraft:item/symbol_portfolio"}}

ports/mc263/src/main/resources/assets/rivencraft/items/writing_desk.json

@@ -0,0 +1 @@
+{"model":{"type":"minecraft:model","model":"rivencraft:item/writing_desk"}}

ports/mc263/src/main/resources/data/rivencraft/advancement/recipes/misc/notebook.json

@@ -0,0 +1,9 @@
+{
+  "parent": "minecraft:recipes/root",
+  "criteria": {
+    "has_material": {"trigger":"minecraft:inventory_changed","conditions":{"items":[{"items":"minecraft:leather"}]}},
+    "has_the_recipe": {"trigger":"minecraft:recipe_unlocked","conditions":{"recipes":["rivencraft:notebook"]}}
+  },
+  "requirements": [["has_material", "has_the_recipe"]],
+  "rewards": {"recipes":["rivencraft:notebook"]}
+}

ports/mc263/src/main/resources/data/rivencraft/advancement/recipes/misc/writing_desk.json

@@ -0,0 +1,9 @@
+{
+  "parent":"minecraft:recipes/root",
+  "criteria":{
+    "has_material":{"trigger":"minecraft:inventory_changed","conditions":{"items":[{"items":"minecraft:feather"}]}},
+    "has_the_recipe":{"trigger":"minecraft:recipe_unlocked","conditions":{"recipes":["rivencraft:writing_desk"]}}
+  },
+  "requirements":[["has_material","has_the_recipe"]],
+  "rewards":{"recipes":["rivencraft:writing_desk"]}
+}

ports/mc263/src/main/resources/data/rivencraft/recipe/notebook.json

@@ -0,0 +1,7 @@
+{
+  "type": "minecraft:crafting_shaped",
+  "category": "misc",
+  "key": {"L": "minecraft:leather", "S": "minecraft:string"},
+  "pattern": [" L ", "S  ", " L "],
+  "result": {"count": 1, "id": "rivencraft:notebook"}
+}

ports/mc263/src/main/resources/data/rivencraft/recipe/writing_desk.json

@@ -0,0 +1,6 @@
+{
+  "type":"minecraft:crafting_shaped", "category":"misc",
+  "pattern":["V F", "PPP", "P P"],
+  "key":{"V":"minecraft:glass_bottle", "F":"minecraft:feather", "P":"#minecraft:planks"},
+  "result":{"id":"rivencraft:writing_desk", "count":1}
+}