Port live instability, writing recovery and Link Modifier controls to 26.3

docs/MINECRAFT_26_3_PORT.md

@@ -2326,3 +2326,265 @@ The user passed .120 and authorized commit, push and publication of the accumula
 implemented libraries, fallback crystal portals and partial instability/decay from
 remaining gameplay and optional-integration parity. Tracking issues #98/#102/#104
 remain open; #114 still requires the matching 1.21.1 fix.
+
+
+## .121 lightning/explosion providers
+
+The player passed .120. Adapted the 1.21.1 hazard implementation, independent hazard
+scheduler lane, loaded-only ring candidates, Legacy aggregated rates, bounded explosion
+calculator, entity/Creative policy, protected-block/spawn checks and event guards.
+Modern differences: EntityTypes registry constants, explicit entity spawn reason,
+server damage API, gamerule registry, spatial fire-spread permission, BreakBlockEvent,
+and explosion damage exposure argument. Since Level.explode now returns void, the
+calculator retains its approved positions for bounded post-blast fire and records
+whether an uncancelled explosion actually began. Lightning dispatch also reports
+whether its entity was accepted. Existing optional mods are not required.
+
+Per-Age modern SavedData persists attempt count and separate hazard cooldowns (with
+the meteor field retained for the next provider port). Default config matches 1.21.1.
+Added OP `/rivencraft_port instability hazard lightning|explosions` to skip probability
+without bypassing cooldowns, loaded terrain, Age/config/provider policy or spawn
+exclusion. Console sources may supply dimension/position explicitly. Neither the
+command nor provider registration changes saved instability scores/decks.
+
+Version 1.0.1.121-beta.1 builds and starts a dedicated server. The user offered manual
+damage/block-destruction testing, so the temporary server was stopped before running
+those fixtures and the world removed. Effects, visual/audio behavior, damage/block
+caps and policy/restart checks are handed over; they are not reported as tested.
+No new permanent GameTests, commit, push or publication. Meteor, burning, erosion,
+crumble, full grammar recovery and live material profiling remain pending.
+
+
+## .122 meteor provider
+
+The player passed .121. Extracted the meteor-specific portion of the existing 1.21.1
+AgeEnvironmentalProviders into a focused modern provider. The effect remains the
+30-tick flame/smoke flight and roar followed by a strength-3 bounded impact, without
+inventing a new rendered entity. Natural chance, randomized chunk/central coordinates,
+48-block descent height, headroom/spawn checks, 200-tick cooldown, one active flight
+per Age and 16 active Ages retain the root values.
+
+The selected card uses an independent scheduler pass, sharing the existing hazard
+candidate ring and saved attempt/cooldown data. The impact reuses the .121 blast
+guards with meteor-specific config (24 blocks, eight entities, 12 damage by default).
+Event handlers cancel active flights on disabled policy, absent players, unavailable
+target chunk, Age unload or shutdown; session-only descent state is not replayed.
+Modern changes use loaded ChunkPos accessors, max-Y API and codec SavedData already
+ported for hazards. No optional mod dependency or new asset was introduced.
+
+Added OP `/rivencraft_port instability meteor`, bypassing chance only. Status reports
+meteor config distinctly from potion policy. The original roar is verified in the
+built JAR. Version 1.0.1.122-beta.1 builds; effects, damage/protection, cooldown and
+cancellation/restart behavior are delegated to the player's manual testing as offered.
+No server/test world was launched, no permanent test added, and no commit/publication.
+Burning, erosion/crumble, full grammar recovery and live material profiling remain.
+
+
+## .123 burning and erosion
+
+The player passed .122. Extracted/adapted the 1.21.1 burning/erosion handlers into a
+focused provider class, retaining bounded candidate scans, seeded attempt sequence,
+independent scheduler budgets and protection/event logic. Burning keeps the active
+Legacy card, sky exposure, Survival/Adventure targeting, four targets per pass and
+4..12-second duration. The manual pulse targets the player and uses modern water/rain
+checking rather than the removed isInWaterRainOrBubble API.
+
+Erosion stays absent from the Legacy deck, with the prior requested testing default
+of enabled at >=10,000 current instability. It converts at most one eligible sampled
+block to an adjacent above/horizontal source fluid. Current score resolves creation
+contributions or an explicit session override; live profiling is not yet claimed.
+The pulse requires a real aimed block within six blocks and the same threshold and
+mutation/protection policy. Modern BreakBlockEvent and snapshot placement rollback
+are reused. Provider status distinguishes these controls from potion policy.
+
+Added OP `/rivencraft_port instability environment burning|erosion`. No scores/plans
+are changed by provider registration or test pulses. Config names/defaults match the
+1.21.1 scorching/erosion sections. Version 1.0.1.123-beta.1 builds; visual/damage/fluid,
+exemption, policy and natural scheduling checks are handed to the player. No temporary
+server/world or permanent fixtures were created; no commit/push/publication.
+
+
+## .124 live material profiling
+
+The player passed .123. Crumble has no active 1.21.1 handler, so it remains explicitly
+unavailable. Ported AgeBlockInstability and modern per-dimension profile SavedData,
+using the same 401/500 readiness thresholds, 1,024 sample cap, watched/native/modded
+weights, 5% Overworld allowance, 100,000-point cap and difficulty scaling. Registry
+material eligibility reuses the Page pool rules; common ore/storage tags use modern
+BlockItems tag accessors. Installed content remains optional; exact weight overrides
+retain the existing root syntax and validation.
+
+Deferred chunk-load sampling processes four entries/tick with a bounded queue. Spawn
+completion requests one chunk per second across occupied profiling Ages and their
+baseline, with at most one request in flight. The off-thread getChunkFuture path was
+verified in the local 26.3 source to avoid main-thread managedBlock. Completion checks
+server stop/level identity. Existing sampled chunks are not recounted. Effective
+provider plans now combine live points and frozen writing, cache stable totals/seeds,
+and retain the original saved plan. Old neutral Ages stay excluded. OP status shows
+progress/totals and session override reset restores the live effective plan.
+
+Version 1.0.1.124-beta.1 builds and starts a dedicated server. Real chunk-load sampling
+persisted 25 snapshots and counted a fixture Diamond Block. A bounded restart test
+used synthetic sample records, plus resumed actual loads: 423 Age / 522 baseline
+samples yielded 2,987 live points (independently calculated), a frozen writing score
+of zero and live selected providers. Override reset restored that plan. No hundreds-
+of-chunks generation test was run; occupied-Age background generation and generated
+material/modded/config checks are delegated to the player. Server stopped and world
+removed. No permanent fixtures, commit, push or publication.
+
+
+## .125 ordered controller recovery
+
+The player passed .124. Added semantic-role metadata to the port symbol index and
+a focused recovery pass for singular-controller duplicates/conflicts, category
+order, Native-with-biomes and Single-with-extra-biomes. Last singular choice wins;
+Single retains the first biome; Native drops authored biome choices. Duplicate or
+conflict diagnostics contribute 500 points and order diagnostics 100, following
+the corresponding 1.21.1 grammar rules. Costs retain original page indices.
+
+Binder support and server terrain/environment selection share recovered choices.
+Original book/library pages, color boundaries and celestial-chain indices remain
+intact; raw number/celestial validation and all unimplemented-page guards still
+apply. Missing biome registry entries are checked even if recovery would discard
+the page. Ambient Color has its own stage and is not a singular lighting choice.
+Existing Ages are unchanged. This is the first recovery slice, not completion of
+celestial/dangling/material grammar recovery or season integration.
+
+Version 1.0.1.125-beta.1 builds; 13 temporary focused checks pass, covering recovery,
+costs, preserved chains and rejection boundaries. No server/test world or permanent
+fixtures. In-game last-choice behavior, original-page retention and OP diagnostics
+are delegated to the player. No commit, push or publication.
+
+
+## .126 ordered celestial and number recovery
+
+The player passed .125. Ported the 1.21.1 grammar treatment of pending celestial
+modifiers and numeric adjacency. Repeated Length/Phase/Angle/Size/Direction pages
+before a celestial use the final value of that kind without a duplicate penalty.
+Only the final unconsumed modifier of each kind adds 100 dangling-modifier points.
+A number without an immediately following supported Color/Length/Phase/Angle/Size
+page adds 100 points (misplaced, or dangling at the end). Consecutive numbers leave
+only the last available for the next target. Colors still mix in written order.
+
+These defects no longer block binding. Numbers and celestial compilation retain
+the original page sequence and seeded color indices; controller recovery never
+moves a number next to a new target. A trailing modifier cannot rewrite an earlier
+body, including the optimized single-body compilation path. Missing celestial
+branches retain their existing seeded completion; dangling controls do not apply
+to those generated bodies. All original book/library pages remain. Unsupported
+pages and the ten-sun/ten-moon limit still block binding; existing Ages are unchanged.
+
+Version 1.0.1.126-beta.1 builds. Seventeen temporary focused checks passed, covering
+last-value selection, dangling costs/indices, numeric adjacency, per-body isolation,
+seeded color stability, valid numbered writing, body limits, unsupported pages and
+cycle codec round-trip. No server/world or permanent test fixture was created.
+Manual validation: bind a book with Half Length, Double Length, Sun and verify the
+last length; bind Sun followed by Large Size and confirm it does not resize that
+sun. Test a trailing Number page and inspect the added writing contribution with
+`/rivencraft_port instability status`. Original pages should remain visible.
+No commit, push or publication.
+
+
+## .127 Link Modifier station: title and core link properties
+
+The player passed .126. Started the missing 1.21.1 Link Modifier station port,
+reusing its block model, textures, horizontal facing variants and Legacy 176x166
+single-book GUI. The item is available in the main creative tab or via
+`/give @s rivencraft:link_modifier`; it has no crafting recipe. As in 1.21.1,
+creative acquisition does not impose a new permission restriction on ordinary
+book edits once the station has been placed.
+
+One persistent slot accepts Linking and Descriptive Books, including unbound
+books, with normal and shift-click transfers. The server menu handles renaming
+and Disarm, Maintain Momentum and Intra Linking toggles. Descriptive Books cannot
+toggle Intra Linking, which only governs same-dimension Linking Book travel.
+Existing target, author, symbols and Age identity are retained. Renaming changes
+the item's custom title, not the Age's saved folder/registry identity. Removing
+the title restores the item's normal name. Text editing consumes inventory/hotbar
+shortcuts while focused; Escape closes the screen. Programmatic text refreshes do
+not send rename packets. Menu identity, owner, distance and live station checks
+protect edits; unknown button IDs and non-book inputs are rejected.
+
+The book is saved with modern ValueInput/ValueOutput container serialization.
+Station removal uses block-entity preRemoveSideEffects to release the stored book
+once, including non-player removal. No tick handler or renderer is needed.
+
+This is a station slice, not full Link Modifier parity. Seed editing, Age retirement,
+Relative Link, Intra-Linking Only and platform overrides remain unported and are
+not presented as working controls. Existing core flag behavior is reused unchanged.
+Manual validation: place the station in multiple orientations, insert/shift-click
+both book types, rename using text containing E, toggle each available property,
+remove the book and use it to check travel effects. Confirm Descriptive Book Intra
+Linking is unavailable, restart with a book left in the station, and break a loaded
+station to recover one book. Build and dedicated persistence results are recorded
+below. No commit, push or publication.
+
+Version 1.0.1.127-beta.1 builds. Packaged model, GUI, texture, item definition,
+loot table and localization checks passed; no station recipe is included. A
+fresh dedicated server placed the station and serialized a named Linking Book
+with all three core flags. Restart retained the same book/name/flags and station
+removal completed normally. The first harness run expected the wrong wording
+for vanilla force-load cleanup; the corrected harness completed successfully.
+Both temporary worlds were deleted and servers stopped. No permanent tests were
+added. UI interaction, transfer counts and modifier travel effects await the
+player's in-game check.
+
+
+## .128 six Link Modifier controls
+
+The player reported that .127 exposed only three of 1.21.1's six controls. Added
+the remaining Intra-Linking Only, Relative Link and Generate Platform controls in
+the existing two-column, three-row Legacy layout, with matching bit values and
+server-owned menu actions. Enabling Intra-Linking Only enables Intra Linking too;
+disabling Intra Linking clears Intra-Linking Only. Both intra controls are disabled
+for Descriptive Books. Unknown actions and out-of-range menu edits remain rejected.
+
+Linking Book Intra-Linking Only blocks cross-dimension travel. Relative Link uses
+the traveller's block offset from the source world's spawn, applied to destination
+spawn, preserving destination yaw/pitch. Normal links retain their precise bound
+coordinates. Player and non-player portal travel share the new flags and relative
+coordinate helper. Descriptive relative arrivals still require proper footing.
+
+Generate Platform is off by default for Linking Books. When enabled, a successful
+link fills one missing floor block with cloud platform only if the block two above
+the arrival is air, matching the 1.21.1 helper. Existing floors are retained.
+Descriptive Books instead default to enabled and use Disable Platform internally;
+turning it off prevents fallback platform creation and refuses travel if no footed
+landing is available. Receptacle tint preparation respects that setting too.
+New flags serialize in the shared component and appear in book/panel tooltips.
+Existing three-flag books remain valid. Seed editing and Age retirement remain
+separate, unfinished station work.
+
+Version 1.0.1.128-beta.1 builds. A temporary dedicated-server fixture passed 19
+checks: menu actions/dependencies, descriptive intra rejection, numeric flag codec,
+relative offsets, platform-off/default behavior, platform placement/preservation,
+invalid input and remote edit protection. It did not perform real client travel.
+The test server stopped and its world/fixture sources were removed. The production
+JAR is rebuilt without that fixture. Manual checks: all six buttons and tooltips,
+same/cross-dimension Intra-Linking Only, Relative Link offsets, and platform on/off
+for both book types (including a new Void Age without footing). No commit, push
+or publication.
+
+
+## .129 Link Modifier mouse input repair
+
+The player reported that none of the six controls responded. Confirmed the
+26.3 input constants in the local Minecraft artifact: left/middle/right are
+1/2/3, while the custom Link Modifier handler checked the old left-button value
+0. Its server actions therefore passed the prior direct-menu fixture while
+real mouse clicks never sent an action.
+
+Replaced the manually drawn/clicked areas with six registered Minecraft Button
+widgets at the same Legacy positions. Their callbacks send the existing validated
+menu action IDs, and their custom rendering retains the square controls. Native
+input provides correct mouse mapping, focus, click sound and keyboard activation.
+All six tooltips expose their On/Off state; unavailable Descriptive Book intra
+controls remain disabled. Tooltip objects update only when state changes so their
+hover delay is not reset every tick. Book mutations/travel code is unchanged.
+
+Version 1.0.1.129-beta.1 builds. The native widget's left-button mapping and callback
+dispatch were verified in the local Minecraft bytecode. No client click test or
+new server run was performed; the previous 19 checks covered server actions, not
+client input. Please click each option with an inserted Linking Book and verify
+its selected shading and tooltip/book properties change, then repeat supported
+options with a Descriptive Book. No commit, push or publication.

ports/mc263/README.md

@@ -9,9 +9,11 @@ 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.
 Crystal portals and libraries are ported. Instability scoring/provider selection,
-status effects and colored decay are partially ported; remaining hazards, live material profiling,
-remaining discovery/stations, writing recovery and optional integrations remain unfinished. The latest published beta is
-[1.0.1.120-beta.1](RELEASE_NOTES_1.0.1.120-beta.1.md).
+status effects, colored decay, lightning, explosions, meteors, burning and erosion,
+ordered writing recovery, live material profiling and all six Link Modifier controls are now ported.
+Link Modifier seed editing/retirement, remaining discovery/configuration and optional
+integrations remain unfinished. The latest published beta is
+[1.0.1.129-beta.1](RELEASE_NOTES_1.0.1.129-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.
 
@@ -2142,3 +2144,390 @@ No permanent test fixtures, commit, push or publication.
 The player passed every slice, including .120 colored decay, and authorized commit,
 push and publication as 1.0.1.120-beta.1. Both Minecraft targets build successfully.
 See the consolidated release notes for the published scope and remaining parity gaps.
+
+
+## Beta .121 — lightning and explosions
+
+The player passed .120. This slice ports the 1.21.1 lightning/explosion providers,
+their separate scheduling lane, persisted per-Age attempt sequence/cooldowns,
+loaded-chunk candidate selection and existing damage/protection settings.
+
+Each selected hazard receives a roll on each admitted Age scheduler pass, independent
+of rotating potion/decay providers. Legacy per-chunk/per-tick odds are aggregated as
+`1 - (1 - 1/denominator)^(loadedChunks * interval * effectiveCopies)`. Denominators
+remain 100,000 for clear-weather lightning, 5,000 during rain plus thunder, and 1,000
+for explosions. Candidate chunks are already-loaded rings around Age players, capped
+at 81 by default; no chunks are generated for hazards. Lightning uses the motion-blocking
+surface; natural explosions choose a random Y across the dimension's modern height.
+
+Defaults match 1.21.1: hazards/block damage/player damage/fire enabled, 20-tick minimum
+gap per hazard type, strength-3 blasts, at most 16 distinct destructible blocks and
+eight damaged entities, and at most 12 damage per entity (lightning itself caps at 5).
+Creative/Spectator are excluded. Spawn columns within eight blocks horizontally are
+excluded as targets; protected infrastructure, block entities, TNT, portals and
+unbreakable blocks resist blasts. Break and placement cancellation checks remain.
+World mutation and mobGriefing gate block damage; entity damage and visual/audio
+feedback can remain active when block mutation is disabled.
+
+The modern API no longer returns an explosion/block list. The damage calculator
+retains its bounded approved positions for post-blast ignition, only where the block
+is now air and fire placement is allowed. Cancelled explosion startup does not count
+as dispatch or generate follow-up fire. NeoForge's renamed BreakBlockEvent and 26.3's
+`canSpreadFireAround` replace the old break event and doFireTick query respectively.
+Vanilla explosion networking and lightning entities provide existing visuals/sounds.
+The `instability_hazards` config section retains the 1.21.1 setting names/defaults.
+
+Operator checks inside an Age:
+
+- `/rivencraft_port instability hazard lightning`
+- `/rivencraft_port instability hazard explosions`
+
+These skip random probability only, retaining loaded-chunk, cooldown, Age/config/provider
+and protected-spawn checks. They target a nearby loaded chunk center, using its surface
+for lightning and the command's Y for explosions, rather than the player's exact feet.
+Move away from the arrival area and allow at least one second between repeats of the
+same hazard. The command reports no dispatch when blocked/cancelled. It also works with
+an explicitly positioned console source. Generic `pulse lightning`/`pulse explosions`
+retain their natural probability roll; `test_score`/`status` exercise normal selection.
+The saved score/plan and catalog protocol are unchanged.
+
+Build and dedicated-server startup passed. The user offered to validate damage and
+block destruction manually, so the server was stopped before effect/terrain fixtures
+were run and its temporary world was removed. Manual checks include lightning/thunder,
+explosion visuals/sound, damage caps and Creative immunity, block/protected-block limits,
+spawn exclusion, world-mutation/mobGriefing/fire settings, cooldown/restart persistence,
+and natural rates in occupied Ages. No permanent tests, commit, push or publication.
+
+
+## Beta .122 — meteor flight and impacts
+
+The player passed .121 lightning/explosion testing. Meteors now reuse the 1.21.1
+particle descent, roar sound, selected Legacy provider card, independent scheduling
+lane and bounded blast helper. They are not a new falling-block/entity model: a
+flame/smoke trail descends for 30 ticks (1.5 seconds) from up to 48 blocks above a
+captured surface target, followed by the impact. The existing meteor roar is bundled.
+
+Natural scheduling aggregates the Legacy 1-in-50,000 per-chunk/per-tick odds across
+loaded chunks, scheduler interval and effective card copies, as in 1.21.1. Targets
+are randomized among already-loaded nearby candidate chunks; X/Z vary within the
+safe central area of each chunk. Up to 16 candidate chunks are considered per
+schedule attempt. Target selection rejects protected spawn columns and surfaces
+without headroom. No terrain is loaded or generated by the provider.
+
+The shared hazard SavedData preserves the meteor cooldown (200 game ticks) and random
+attempt sequence. At most one meteor can descend per Age and 16 Ages can have active
+flights. A pending descent is session-only: server stop, Age unload, no players,
+unloaded target chunk, or disabled Age/global/provider/meteor policy cancels it.
+Interrupted flights never replay after restart; the saved cooldown remains. The
+flight is removed before impact dispatch so a failed impact cannot repeat.
+
+The independent `[instability_meteor]` settings match 1.21.1: enabled/block damage/
+player damage/fire default true, maximum 24 impact blocks, eight damaged entities,
+and 12 damage per entity, strength 3. Impact reuses protected block/BE/infrastructure,
+claim events, Creative/Spectator immunity, world-mutation/mobGriefing and modern fire
+permission checks. Disabling block mutation still permits descent, sound and eligible
+entity damage. Generic instability status reports meteor availability separately
+from potion policy; saved scores/decks and catalog protocol are unchanged.
+
+Test inside an Age, away from its arrival area:
+
+`/rivencraft_port instability meteor`
+
+This skips the natural probability roll, retaining cooldown, loaded target, active
+flight and all policy checks. It uses randomized nearby impact locations, unlike
+the deliberately fixed chunk-center lightning/explosion test commands. Wait at
+least ten seconds before repeating. `/rivencraft_port instability pulse meteors`
+keeps the natural chance roll; test-score/status tools exercise saved deck selection.
+
+The build passed and JAR sound/class packaging was verified. Following the player's
+manual validation preference, particle/audio presentation, impacts/damage/protection,
+repeat cooldown, disabling/leaving during flight and restart cancellation are handed
+over for in-game testing. No server or new world was launched for this slice. No new
+permanent tests, commit, push or publication.
+
+
+## Beta .123 — burning and erosion
+
+The player passed .122 meteor testing. This slice adapts the remaining burning and
+erosion portions of 1.21.1 AgeEnvironmentalProviders, using the existing hazard
+candidate selection, saved attempt sequence, protection helpers and independent
+provider scheduling. No new textures, entities, sounds or optional mods are required.
+
+Burning remains an active Legacy deck card. Sky-exposed eligible living entities
+outside protected spawn can ignite; Survival/Adventure players are included by
+default and Creative/Spectator are excluded. Natural processing inspects at most
+eight loaded chunks/eight eligible candidates per chunk, ignites at most one per
+inspected chunk and four entities per pass by default. The old 1-in-10 per-tick gate
+is aggregated over the scheduler interval. Fire lasts four seconds per effective
+provider level, capped at twelve. Vanilla water/rain extinguishing and fire immunity
+remain in force. Disabling the provider stops new ignitions; existing fire follows
+vanilla behavior rather than the potion lease cleanup mechanism.
+
+Erosion remains outside Legacy's saved card deck. As requested for testing in 1.21.1,
+its config defaults enabled and natural attempts run in admitted occupied Ages at a
+current score of at least 10,000. Current score uses the frozen creation total or an
+explicit session test-score override; live material profiling remains pending.
+At most eight random positions are sampled in already-loaded candidate chunks per
+pass, with at most one conversion. An eligible block next to a source fluid above or
+on a horizontal side is replaced with that fluid's source block; fluid below does
+not grow upward. Normal fluid ticks can subsequently spread it.
+
+Erosion requires world_mutation and mobGriefing, and reuses decay's protection against
+spawn/infrastructure, block entities, fluids, critical/unbreakable blocks and protected
+tags. Modern break/place claim events and rollback remain. Its `instability_erosion`
+enabled toggle does not add a new saved card or alter the Age score. Burning uses
+`instability_scorching`: enabled/affect_players default true and max_targets_per_pass
+is 4 (range 0–16), matching 1.21.1.
+
+Operator manual checks inside an Age:
+
+- On dry ground under open sky, outside arrival protection and in Survival, run
+  `/rivencraft_port instability environment burning`. It targets the player directly
+  for four seconds, skips the chance roll, and explicitly reports water/rain that
+  would immediately extinguish the fire.
+- Place ordinary Stone beside or below source water/lava, outside protected arrival.
+  Use `/rivencraft_port instability test_score 10000`, look at the Stone within six
+  blocks, and run `/rivencraft_port instability environment erosion`. The aimed
+  block should become that adjacent source fluid. Existing policies still apply.
+  End with `/rivencraft_port instability clear_test_score` to restore the saved plan.
+- Automatic burning needs a selected burning card; natural erosion uses the enabled
+  test policy/threshold. `status` exposes both config/threshold information when
+  inspecting the respective provider, without adding scores to ordinary books.
+
+Build passed. The player is performing visual/effect testing, so no server/world or
+new permanent fixtures were created. Manual validation covers burning/fire damage,
+Creative/shelter/spawn exclusion, wet extinguishing feedback, source-fluid conversion,
+protected blocks, mobGriefing/world-mutation/config switches and natural scheduling.
+No commit, push or publication. Crumble, full writing recovery and live abundance
+profiling remain major instability work.
+
+
+## Beta .124 — live material-abundance instability
+
+The player passed .123. This slice ports 1.21.1's Legacy-style generated-block
+profiling and live effective provider selection. Crumble remains a catalog entry
+without a registered handler in 1.21.1; no new Crumble behavior is invented here.
+
+Overworld and runtime-Age chunk loads enqueue bounded sampling work, rather than
+accessing SavedData during chunk-storage callbacks. Four snapshots are processed
+per server tick, with a queue cap of 2,048. Paletted section counts record watched
+block IDs efficiently. Each chunk is sampled once, up to 1,024 per dimension, and
+samples/totals persist in per-dimension `rivencraft/block_profile` SavedData. Subsequent
+player edits or chunk reloads do not replace or double-count a stored snapshot.
+
+Live points remain zero until at least **401 Age samples and 500 Overworld baseline
+samples** exist, matching 1.21.1. For each watched material, positive excess blocks
+per Age chunk above 1.05 times the Overworld average are multiplied by that material's
+weight. The total rounds to an integer and caps at 100,000. The watched list retains
+Legacy ores/quartz/glowstone/crystal and the existing modern/storage extensions,
+including Diamond Blocks, Ancient Debris and Netherite Blocks.
+
+Recognized ores, mineral storage blocks and source-fluid block types from installed
+mods participate automatically via current NeoForge common tags, names and the same
+full-block/fluid material eligibility used for Pages. No content mod/API is required.
+Unknown ore/storage forms use the 1.21.1 fallback weights; known minerals retain its
+named weights. `[instability_modded_materials] block_weight_overrides` accepts exact
+`modid:block_id=points` entries, including zero to exclude a modded block. This is
+installation-based optional support, not a required mod or per-mod opt-in switch.
+
+While a profiling-enabled Age is occupied, missing spawn-area samples are requested
+gradually: at most one chunk request per second, one in flight across the server,
+round-robin between active Ages and the Overworld baseline. Existing samples are
+skipped. The modern getChunkFuture API still blocks when invoked on the server
+thread, so requests use its off-thread scheduling path and completion returns to
+the server thread. Closed levels and stopped-server callbacks are discarded. No
+permanent force-load tickets or generation while no Age is occupied are introduced.
+Natural exploration also fills the sample pool and can reach readiness sooner.
+
+Writing contributions and the original saved provider plan remain frozen. The live
+score is added only at runtime, and the effective deck is reselected deterministically
+from the same saved seed as the total changes. Providers can therefore appear or
+change as abundance is measured. Unchanged totals/seeds reuse a cached plan rather
+than reshuffling on each query. Older Ages predating instability records remain
+neutral; saved neutral arrivals/enable flags do not opt them into new scoring.
+
+`[instability] difficulty` matches 1.21.1: 0=quarter, 1=half, 2=normal (default),
+3=1.75x. It scales writing plus live points without rewriting saved contributions.
+A session `test_score` remains an explicit final-score override and is cleared on
+restart; clearing it now restores the live effective plan. Erosion threshold checks
+use this same effective score.
+
+Use `/rivencraft_port instability status` inside an Age to inspect frozen/live/effective
+scores, difficulty, profile eligibility and both sample counts. Normal book/Binder
+screens receive no score/profiler data. Zero live points before both thresholds are
+ready are expected. To validate, create/explore an Age with Diamond Block Rocks or
+another abundant watched material, watch progress, then confirm live points and
+providers change while the frozen writing contribution remains unchanged. Reopen the
+world to check sample persistence; repeated reloads should not duplicate counts.
+
+Build and temporary dedicated-server checks passed. Real loaded snapshots saved 25
+samples per test dimension and captured one deliberately placed fixture Diamond Block.
+A restart with synthetic profile records exercised scoring/decoding without generating
+hundreds of chunks: resumed real chunk samples produced 423 Age and 522 baseline
+samples, with the expected 2,987 live points, frozen score zero and effective providers.
+Clearing a session override restored the same live result. This verifies save/scoring
+plumbing, not natural bulk generation. The player will check background progress,
+actual generated material distribution, modded recognition and difficulty/config
+changes. Test server stopped/world deleted; no permanent tests, commit or publication.
+
+
+## .125 ordered controller recovery
+
+The player passed .124. New authored Ages now recover repeated singular terrain,
+biome-distribution, weather, lighting and sky choices: the last choice wins, with
+500 instability per duplicate or conflict. Supported category-order mistakes add
+100 points instead of blocking binding. Native distribution discards authored
+biome choices with a 500-point conflict; Single retains the first authored biome
+with a 500-point conflict when extras exist. These diagnostics use the 1.21.1
+writing rules. Season pages remain unsupported until their integration is ported.
+
+The original pages remain in the book and library source list. Generation receives
+recovered choices without rearranging material/feature or per-celestial modifier
+chains. Existing Ages are not rescored. OP instability status shows the writing
+contributions; normal book/Binder screens do not expose the score or new warnings.
+Unknown/unported pages and other unsupported combinations still prevent binding.
+Celestial, number and dangling-modifier recovery is a later slice: their existing
+validation still applies to the original page sequence, before controller recovery.
+
+Version 1.0.1.125-beta.1 builds. Thirteen temporary focused checks passed for
+last-choice selection, duplicate/conflict/order costs, Native/Single recovery,
+unimplemented pages, raw numeric guards, celestial-chain preservation, intentional
+feature repeats and Ambient Color ordering. No server/world was launched. In-game
+validation: bind books with conflicting terrain/weather choices and confirm the
+last choice takes effect; test Native with biome pages and Single with two biomes;
+check that all original pages remain and OP status reports the writing costs.
+No commit, push or publication.
+
+
+## .126 ordered celestial and number recovery
+
+The player passed .125. Ported the 1.21.1 grammar treatment of pending celestial
+modifiers and numeric adjacency. Repeated Length/Phase/Angle/Size/Direction pages
+before a celestial use the final value of that kind without a duplicate penalty.
+Only the final unconsumed modifier of each kind adds 100 dangling-modifier points.
+A number without an immediately following supported Color/Length/Phase/Angle/Size
+page adds 100 points (misplaced, or dangling at the end). Consecutive numbers leave
+only the last available for the next target. Colors still mix in written order.
+
+These defects no longer block binding. Numbers and celestial compilation retain
+the original page sequence and seeded color indices; controller recovery never
+moves a number next to a new target. A trailing modifier cannot rewrite an earlier
+body, including the optimized single-body compilation path. Missing celestial
+branches retain their existing seeded completion; dangling controls do not apply
+to those generated bodies. All original book/library pages remain. Unsupported
+pages and the ten-sun/ten-moon limit still block binding; existing Ages are unchanged.
+
+Version 1.0.1.126-beta.1 builds. Seventeen temporary focused checks passed, covering
+last-value selection, dangling costs/indices, numeric adjacency, per-body isolation,
+seeded color stability, valid numbered writing, body limits, unsupported pages and
+cycle codec round-trip. No server/world or permanent test fixture was created.
+Manual validation: bind a book with Half Length, Double Length, Sun and verify the
+last length; bind Sun followed by Large Size and confirm it does not resize that
+sun. Test a trailing Number page and inspect the added writing contribution with
+`/rivencraft_port instability status`. Original pages should remain visible.
+No commit, push or publication.
+
+
+## .127 Link Modifier station: title and core link properties
+
+The player passed .126. Started the missing 1.21.1 Link Modifier station port,
+reusing its block model, textures, horizontal facing variants and Legacy 176x166
+single-book GUI. The item is available in the main creative tab or via
+`/give @s rivencraft:link_modifier`; it has no crafting recipe. As in 1.21.1,
+creative acquisition does not impose a new permission restriction on ordinary
+book edits once the station has been placed.
+
+One persistent slot accepts Linking and Descriptive Books, including unbound
+books, with normal and shift-click transfers. The server menu handles renaming
+and Disarm, Maintain Momentum and Intra Linking toggles. Descriptive Books cannot
+toggle Intra Linking, which only governs same-dimension Linking Book travel.
+Existing target, author, symbols and Age identity are retained. Renaming changes
+the item's custom title, not the Age's saved folder/registry identity. Removing
+the title restores the item's normal name. Text editing consumes inventory/hotbar
+shortcuts while focused; Escape closes the screen. Programmatic text refreshes do
+not send rename packets. Menu identity, owner, distance and live station checks
+protect edits; unknown button IDs and non-book inputs are rejected.
+
+The book is saved with modern ValueInput/ValueOutput container serialization.
+Station removal uses block-entity preRemoveSideEffects to release the stored book
+once, including non-player removal. No tick handler or renderer is needed.
+
+This is a station slice, not full Link Modifier parity. Seed editing, Age retirement,
+Relative Link, Intra-Linking Only and platform overrides remain unported and are
+not presented as working controls. Existing core flag behavior is reused unchanged.
+Manual validation: place the station in multiple orientations, insert/shift-click
+both book types, rename using text containing E, toggle each available property,
+remove the book and use it to check travel effects. Confirm Descriptive Book Intra
+Linking is unavailable, restart with a book left in the station, and break a loaded
+station to recover one book. Build and dedicated persistence results are recorded
+below. No commit, push or publication.
+
+Version 1.0.1.127-beta.1 builds. Packaged model, GUI, texture, item definition,
+loot table and localization checks passed; no station recipe is included. A
+fresh dedicated server placed the station and serialized a named Linking Book
+with all three core flags. Restart retained the same book/name/flags and station
+removal completed normally. The first harness run expected the wrong wording
+for vanilla force-load cleanup; the corrected harness completed successfully.
+Both temporary worlds were deleted and servers stopped. No permanent tests were
+added. UI interaction, transfer counts and modifier travel effects await the
+player's in-game check.
+
+
+## .128 six Link Modifier controls
+
+The player reported that .127 exposed only three of 1.21.1's six controls. Added
+the remaining Intra-Linking Only, Relative Link and Generate Platform controls in
+the existing two-column, three-row Legacy layout, with matching bit values and
+server-owned menu actions. Enabling Intra-Linking Only enables Intra Linking too;
+disabling Intra Linking clears Intra-Linking Only. Both intra controls are disabled
+for Descriptive Books. Unknown actions and out-of-range menu edits remain rejected.
+
+Linking Book Intra-Linking Only blocks cross-dimension travel. Relative Link uses
+the traveller's block offset from the source world's spawn, applied to destination
+spawn, preserving destination yaw/pitch. Normal links retain their precise bound
+coordinates. Player and non-player portal travel share the new flags and relative
+coordinate helper. Descriptive relative arrivals still require proper footing.
+
+Generate Platform is off by default for Linking Books. When enabled, a successful
+link fills one missing floor block with cloud platform only if the block two above
+the arrival is air, matching the 1.21.1 helper. Existing floors are retained.
+Descriptive Books instead default to enabled and use Disable Platform internally;
+turning it off prevents fallback platform creation and refuses travel if no footed
+landing is available. Receptacle tint preparation respects that setting too.
+New flags serialize in the shared component and appear in book/panel tooltips.
+Existing three-flag books remain valid. Seed editing and Age retirement remain
+separate, unfinished station work.
+
+Version 1.0.1.128-beta.1 builds. A temporary dedicated-server fixture passed 19
+checks: menu actions/dependencies, descriptive intra rejection, numeric flag codec,
+relative offsets, platform-off/default behavior, platform placement/preservation,
+invalid input and remote edit protection. It did not perform real client travel.
+The test server stopped and its world/fixture sources were removed. The production
+JAR is rebuilt without that fixture. Manual checks: all six buttons and tooltips,
+same/cross-dimension Intra-Linking Only, Relative Link offsets, and platform on/off
+for both book types (including a new Void Age without footing). No commit, push
+or publication.
+
+
+## .129 Link Modifier mouse input repair
+
+The player reported that none of the six controls responded. Confirmed the
+26.3 input constants in the local Minecraft artifact: left/middle/right are
+1/2/3, while the custom Link Modifier handler checked the old left-button value
+0. Its server actions therefore passed the prior direct-menu fixture while
+real mouse clicks never sent an action.
+
+Replaced the manually drawn/clicked areas with six registered Minecraft Button
+widgets at the same Legacy positions. Their callbacks send the existing validated
+menu action IDs, and their custom rendering retains the square controls. Native
+input provides correct mouse mapping, focus, click sound and keyboard activation.
+All six tooltips expose their On/Off state; unavailable Descriptive Book intra
+controls remain disabled. Tooltip objects update only when state changes so their
+hover delay is not reset every tick. Book mutations/travel code is unchanged.
+
+Version 1.0.1.129-beta.1 builds. The native widget's left-button mapping and callback
+dispatch were verified in the local Minecraft bytecode. No client click test or
+new server run was performed; the previous 19 checks covered server actions, not
+client input. Please click each option with an inserted Linking Book and verify
+its selected shading and tooltip/book properties change, then repeat supported
+options with a Descriptive Book. No commit, push or publication.

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

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

ports/mc263/build.gradle

@@ -244,6 +244,12 @@ tasks.named('processResources', ProcessResources).configure {
         include 'assets/rivencraft/textures/block/book_binder.png'
         include 'assets/rivencraft/textures/block/book_binder_press.png'
         include 'assets/rivencraft/textures/gui/book_binder_legacy.png'
+        include 'assets/rivencraft/textures/gui/link_modifier_legacy.png'
+        include 'assets/rivencraft/textures/block/link_modifier_*.png'
+        include 'assets/rivencraft/models/block/link_modifier.json'
+        include 'assets/rivencraft/models/item/link_modifier.json'
+        include 'assets/rivencraft/blockstates/link_modifier.json'
+        include 'data/rivencraft/loot_table/blocks/link_modifier.json'
         include 'assets/rivencraft/textures/gui/ink_mixer_legacy.png'
         include 'assets/rivencraft/textures/block/inkwell_base.png'
         include 'assets/rivencraft/textures/block/inkwell_cup.png'

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=1.0.1.120-beta.1
+mod_version=1.0.1.129-beta.1

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

@@ -164,6 +164,15 @@ public final class Rivencraft {
             "book_binder", PortBookBinderBlock::new,
             () -> BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion());
     public static final DeferredItem<BlockItem> BOOK_BINDER_ITEM = ITEMS.registerSimpleBlockItem(BOOK_BINDER);
+    public static final DeferredBlock<net.dnorberg.rivencraft.block.LinkModifierBlock> LINK_MODIFIER = BLOCKS.registerBlock(
+            "link_modifier", net.dnorberg.rivencraft.block.LinkModifierBlock::new,
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.STONE).noOcclusion());
+    public static final DeferredItem<BlockItem> LINK_MODIFIER_ITEM = ITEMS.registerSimpleBlockItem(LINK_MODIFIER);
+    public static final Supplier<BlockEntityType<net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity>> LINK_MODIFIER_BLOCK_ENTITY =
+            BLOCK_ENTITY_TYPES.register("link_modifier", () -> new BlockEntityType<>(
+                    net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity::new, LINK_MODIFIER.get()));
+    public static final Supplier<MenuType<net.dnorberg.rivencraft.menu.LinkModifierMenu>> LINK_MODIFIER_MENU =
+            MENUS.register("link_modifier", () -> IMenuTypeExtension.create(net.dnorberg.rivencraft.menu.LinkModifierMenu::new));
     public static final DeferredBlock<InkMixerBlock> INK_MIXER = BLOCKS.registerBlock(
             "ink_mixer", InkMixerBlock::new,
             () -> BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion());
@@ -254,6 +263,9 @@ public final class Rivencraft {
         modEventBus.addListener(PortBookNetworking::registerPayloads);
         net.dnorberg.rivencraft.age.PortStatusEffectProviders.register();
         net.dnorberg.rivencraft.age.PortDecayProviders.register();
+        net.dnorberg.rivencraft.age.PortHazardProviders.register();
+        net.dnorberg.rivencraft.age.PortMeteorProvider.register();
+        net.dnorberg.rivencraft.age.PortEnvironmentalProviders.register();
         LOGGER.info("Initializing Rivencraft 26.3 port slice (not release-ready)");
     }
 }

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

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

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

@@ -819,8 +819,8 @@ public final class PortAgeCommands {
                     || new PortDayCycle(true, 2, 0).ticks(12000) != 6000
                     || new PortDayCycle(true, 0, 321).ticks(-123456) != 321
                     || new PortDayCycle(true, 0, 321).ticks(123456) != 321
-                    || PortDayCycle.validWriting(java.util.List.of(symbol.apply("period/half")))
-                    || PortDayCycle.validWriting(java.util.List.of(PortDayCycle.NORMAL_TIME, symbol.apply("period/half"))))
+                    || !PortDayCycle.validWriting(java.util.List.of(symbol.apply("period/half")))
+                    || !PortDayCycle.validWriting(java.util.List.of(PortDayCycle.NORMAL_TIME, symbol.apply("period/half"))))
                 throw new IllegalStateException("Day cycle fixture failed");
             var server = context.getSource().getServer();
             var biomes = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(pages, server.registryAccess());
@@ -1616,7 +1616,7 @@ public final class PortAgeCommands {
                         || Math.abs(moving.bodyAngle(origin + 100) + 3F) > 0.0001F
                         || !PortDayCycle.validWriting(java.util.List.of(target, PortDayCycle.NORMAL_TIME))
                         || !PortDayCycle.validWriting(java.util.List.of(target, target))
-                        || PortDayCycle.validWriting(java.util.List.of(target, symbol.apply("size/large"))))
+                        || !PortDayCycle.validWriting(java.util.List.of(target, symbol.apply("size/large"))))
                     throw new IllegalStateException("Single-body modifier/order invariant failed");
             }
             var older = PortDayCycle.CODEC.parse(com.mojang.serialization.JsonOps.INSTANCE,

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

@@ -18,33 +18,45 @@ public final class PortAgeTravel {
     }
 
     public static String enter(ServerPlayer player, Identifier id) {
+        return enter(player, id, net.dnorberg.rivencraft.item.LinkProperties.NONE);
+    }
+    public static String enter(ServerPlayer player, Identifier id, net.dnorberg.rivencraft.item.LinkProperties properties) {
         ServerLevel target = player.level().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
         if (target == null) return "Age not loaded: " + id;
         if (!AgeCatalogSync.ready(player, id)) {
             return "Age catalog not acknowledged by client; remaining in source dimension";
         }
-        BlockPos landing = resolveLanding(target);
+        BlockPos landing = resolveLanding(target, player, properties);
         if (landing == null) return "No safe landing available; remaining in source dimension";
         boolean moved = player.teleportTo(target, landing.getX() + 0.5, landing.getY(), landing.getZ() + 0.5,
                 Set.of(), player.getYRot(), player.getXRot(), true);
         return moved ? null : "Teleportation failed; remaining in source dimension";
     }
 
-    public static BlockPos resolveLanding(ServerLevel target) {
+    public static BlockPos resolveLanding(ServerLevel target) { return resolveLanding(target, true); }
+    public static BlockPos resolveLanding(ServerLevel target, net.minecraft.world.entity.Entity entity,
+                                          net.dnorberg.rivencraft.item.LinkProperties properties) {
+        BlockPos landing = resolveLanding(target, !properties.has(net.dnorberg.rivencraft.item.LinkProperties.DISABLE_PLATFORM));
+        if (landing == null || !properties.has(net.dnorberg.rivencraft.item.LinkProperties.RELATIVE_LINK)) return landing;
+        return findFootedDestination(target, net.dnorberg.rivencraft.item.PortLinkDestinations.relativeOrigin(
+                (ServerLevel) entity.level(), target, entity.blockPosition())).orElse(null);
+    }
+    public static BlockPos resolveLanding(ServerLevel target, boolean generatePlatform) {
         boolean fissure = target.getChunkSource().getGenerator() instanceof PortFeatureChunkGenerator features
                 && features.terrainFeatures() != null && features.terrainFeatures().starFissures();
         BlockPos landing = fissure ? PortStarFissureFeature.savedSpawn(target) : null;
         if (landing != null) landing = isCaveTerrain(target)
                 ? findFootedDestination(target, landing).orElse(null)
                 : findSurfaceLanding(target, landing.getX(), landing.getZ());
-        if (landing == null) landing = findLanding(target);
+        if (landing == null) landing = findLanding(target, generatePlatform);
         if (landing == null) return null;
         if (fissure) PortStarFissureFeature.generateOnce(target, landing, isCaveTerrain(target));
         if (target instanceof PortAgeLevel) PortInstabilityData.get(target.getServer()).recordSpawn(target, landing);
         return landing;
     }
 
-    static BlockPos findLanding(ServerLevel target) {
+    static BlockPos findLanding(ServerLevel target) { return findLanding(target, true); }
+    static BlockPos findLanding(ServerLevel target, boolean generatePlatform) {
         if (isCaveTerrain(target)) {
             // The cave roof is not a valid arrival surface. Search down from
             // Legacy's Y=64 start, then construct the normal safety platform
@@ -60,7 +72,7 @@ public final class PortAgeTravel {
                     }
                 }
             }
-            return makePlatform(target, new BlockPos(0, 64, 0));
+            return generatePlatform ? makePlatform(target, new BlockPos(0, 64, 0)) : null;
         }
         BlockPos surface = findSurfaceLanding(target, 0, 0);
         if (surface != null) return surface;
@@ -68,7 +80,7 @@ public final class PortAgeTravel {
         // beneath it. Void Ages retain the usual platform floor at Y=63.
         BlockPos obstruction = highestObstruction(target, 0, 0);
         int y = obstruction == null ? 64 : Math.max(64, obstruction.getY() + 3);
-        return makePlatform(target, new BlockPos(0, y, 0));
+        return generatePlatform ? makePlatform(target, new BlockPos(0, y, 0)) : null;
     }
 
     static BlockPos findSurfaceLanding(ServerLevel target, int originX, int originZ) {

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

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

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

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

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

@@ -127,19 +127,15 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
     }
 
     public static boolean validWriting(List<Identifier> pages) {
-        int periods = 0, phases = 0, directions = 0, angles = 0, sizes = 0, suns = 0, moons = 0;
-        for (Identifier page : pages) {
-            if (isPeriod(page) && ++periods > 1 || isPhase(page) && ++phases > 1
-                    || isDirection(page) && ++directions > 1 || isAngle(page) && ++angles > 1
-                    || isSize(page) && ++sizes > 1) return false;
-            if (isController(page)) {
-                if (!page.getPath().equals("celestial/moon")) suns++;
-                if (!page.getPath().equals("celestial/sun")) moons++;
-                if (suns > 10 || moons > 10) return false;
-                periods = phases = directions = angles = sizes = 0;
-            }
+        int suns = 0, moons = 0;
+        for (Identifier page : pages) if (isController(page)) {
+            if (!page.getPath().equals("celestial/moon")) suns++;
+            if (!page.getPath().equals("celestial/sun")) moons++;
+            if (suns > 10 || moons > 10) return false;
         }
-        return periods + phases + directions + angles + sizes == 0;
+        // Repeated modifiers overwrite the pending value. Unconsumed modifiers
+        // earn grammar instability, but never affect an earlier body.
+        return true;
     }
 
     public static PortDayCycle compile(List<Identifier> pages, long seed) {
@@ -148,8 +144,8 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
 
     /** Creation-only completion. Exact diagnostic fixtures can still use compile. */
     public static PortDayCycle resolve(List<Identifier> pages, long seed, long nativeTicks) {
-        if (!validWriting(pages) || !PortAgeColors.validNumbers(pages))
-            throw new IllegalArgumentException("Invalid celestial modifier order");
+        if (!validWriting(pages))
+            throw new IllegalArgumentException("An Age may have at most ten suns and ten moons");
         if (pages.stream().anyMatch(PortDayCycle::isController)) return compile(pages, seed, nativeTicks);
         // Match root AgeSkyProfile.random's count draw positions: sky style,
         // mixed sky color, then independent 0..3 sun and moon counts.
@@ -167,7 +163,7 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
     }
 
     public static PortDayCycle compile(List<Identifier> pages, long seed, long nativeTicks) {
-        if (!validWriting(pages)) throw new IllegalArgumentException("Place at most one of each celestial modifier before its controller; limit ten suns and ten moons");
+        if (!validWriting(pages)) throw new IllegalArgumentException("An Age may have at most ten suns and ten moons");
         if (pages.stream().filter(PortDayCycle::isController).count() <= 1)
             return compileOne(pages, seed, nativeTicks, 0);
         var bodies = new java.util.ArrayList<PortCelestialBody>();
@@ -190,8 +186,13 @@ public record PortDayCycle(boolean authored, double period, int stoppedTime,
     }
 
     private static PortDayCycle compileOne(List<Identifier> pages, long seed, long nativeTicks, int ordinal) {
-        var controller = pages.stream().filter(PortDayCycle::isController).findFirst().orElse(null);
-        if (controller == null) return NATIVE;
+        int controllerIndex = -1;
+        for (int i = 0; i < pages.size(); i++) if (isController(pages.get(i))) { controllerIndex = i; break; }
+        // Only preceding modifiers belong to this controller. In particular, a
+        // trailing dangling modifier must not rewrite the single-body fast path.
+        if (controllerIndex < 0) return NATIVE;
+        pages = pages.subList(0, controllerIndex + 1);
+        var controller = pages.getLast();
         int mode = controller.getPath().equals("celestial/sun") ? SUN
                 : controller.getPath().equals("celestial/moon") ? MOON : PAIRED;
         if (mode != PAIRED && !hasBodyModifiers(pages)) return randomUnmodified(seed, ordinal, nativeTicks, mode);

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

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

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

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

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

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

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

@@ -28,8 +28,17 @@ public final class PortInstabilityCommands {
                                     + ": frozen score=" + age.score() + ", enabled=" + age.enabled()
                                     + ", session test score=" + PortInstabilityRuntime.testScore(level)
                                     + ", protected spawn=" + age.spawn().map(BlockPos::toShortString).orElse("not recorded; re-enter this Age")), false);
+                            source.sendSuccess(() -> Component.literal("  live block score=" + PortBlockInstability.score(level)
+                                    + "; effective score=" + PortInstabilityRuntime.effectiveScore(level)
+                                    + "; difficulty=" + PortInstabilityConfig.instabilityDifficulty()
+                                    + "; samples Age=" + PortBlockInstability.sampledChunks(level) + "/" + PortBlockProfileSavedData.MIN_AGE_SAMPLES
+                                    + ", Overworld=" + PortBlockInstability.sampledChunks(source.getServer().overworld()) + "/" + PortBlockProfileSavedData.MIN_BASELINE_SAMPLES
+                                    + "; profiling=" + PortInstabilityData.get(source.getServer()).supportsProfiling(level)), false);
                             for (var cost : age.contributions()) source.sendSuccess(() -> Component.literal(
                                     "  " + cost.reason() + " page=" + cost.page() + " +" + cost.points()), false);
+                            source.sendSuccess(() -> Component.literal("  erosion testing policy (not a saved card): "
+                                    + PortInstabilityRuntime.providerStatus(level, PortEnvironmentalProviders.EROSION)
+                                    + "; current score=" + PortInstabilityRuntime.effectiveScore(level)), false);
                             for (var provider : PortInstabilityRuntime.plan(level).providers())
                                 source.sendSuccess(() -> Component.literal("  " + provider.id() + " level=" + provider.level()
                                         + " [" + PortInstabilityRuntime.providerStatus(level, provider.id()) + "]"), false);
@@ -56,7 +65,7 @@ public final class PortInstabilityCommands {
                         .then(Commands.literal("clear_test_score").executes(context -> {
                             var level = requireAge(context.getSource()); PortInstabilityRuntime.testScore(level, null);
                             PortStatusEffectProviders.clearAge(level);
-                            context.getSource().sendSuccess(() -> Component.literal("Restored saved provider selection"), false); return 1;
+                            context.getSource().sendSuccess(() -> Component.literal("Cleared test override; restored live effective provider selection"), false); return 1;
                         }))
                         .then(Commands.literal("decay").then(Commands.argument("color", StringArgumentType.word())
                                 .suggests((context, builder) -> {
@@ -66,6 +75,48 @@ public final class PortInstabilityCommands {
                                 }).executes(context -> decay(context, 1))
                                 .then(Commands.argument("attempts", IntegerArgumentType.integer(1, 32))
                                         .executes(context -> decay(context, IntegerArgumentType.getInteger(context, "attempts"))))))
+                        .then(Commands.literal("environment").then(Commands.argument("effect", StringArgumentType.word())
+                                .suggests((context, builder) -> {
+                                    for (String effect : java.util.List.of("burning", "erosion"))
+                                        if (effect.startsWith(builder.getRemaining())) builder.suggest(effect);
+                                    return builder.buildFuture();
+                                }).executes(context -> {
+                                    var source = context.getSource(); requireAge(source);
+                                    String effect = StringArgumentType.getString(context, "effect");
+                                    if (!effect.equals("burning") && !effect.equals("erosion")) {
+                                        source.sendFailure(Component.literal("Choose burning or erosion")); return 0;
+                                    }
+                                    int result = PortEnvironmentalProviders.pulseForTesting(source.getPlayerOrException(), effect);
+                                    if (result > 0) source.sendSuccess(() -> Component.literal("Applied " + effect + "; saved score/plan unchanged"), false);
+                                    else source.sendFailure(Component.literal(result == -2 ? "Burning would be extinguished by water or rain"
+                                            : "No effect applied. Check Age/config/provider policy, spawn protection and sky exposure; burning requires Survival/Adventure, erosion requires score >=10000 and a source fluid beside/above the targeted block."));
+                                    return Math.max(0, result);
+                                })))
+                        .then(Commands.literal("meteor").executes(context -> {
+                            var source = context.getSource(); requireAge(source);
+                            int result = PortMeteorProvider.pulseForTesting(source.getPlayerOrException());
+                            if (result > 0) source.sendSuccess(() -> Component.literal("Meteor descent scheduled; impact in 30 ticks. Saved score/plan unchanged."), false);
+                            else source.sendFailure(Component.literal("No meteor scheduled: check cooldown (200 ticks), active flight, safe loaded terrain and Age/config/provider policy."));
+                            return Math.max(0, result);
+                        }))
+                        .then(Commands.literal("hazard").then(Commands.argument("type", StringArgumentType.word())
+                                .suggests((context, builder) -> {
+                                    for (String type : java.util.List.of("lightning", "explosions"))
+                                        if (type.startsWith(builder.getRemaining())) builder.suggest(type);
+                                    return builder.buildFuture();
+                                }).executes(context -> {
+                                    var source = context.getSource(); var level = requireAge(source);
+                                    String type = StringArgumentType.getString(context, "type");
+                                    if (!type.equals("lightning") && !type.equals("explosions")) {
+                                        source.sendFailure(Component.literal("Choose lightning or explosions")); return 0;
+                                    }
+                                    int result = PortHazardProviders.pulseForTesting(level, BlockPos.containing(source.getPosition()), type.equals("lightning"));
+                                    if (result > 0) source.sendSuccess(() -> Component.literal("Triggered " + type
+                                            + " in a nearby loaded chunk; saved score/plan unchanged"), false);
+                                    else source.sendFailure(Component.literal(result < 0 ? "Hazard disabled by config, Age or provider policy"
+                                            : "No hazard triggered: cooldown, protected spawn, unloaded terrain or event cancellation"));
+                                    return Math.max(0, result);
+                                })))
                         .then(Commands.literal("pulse").then(Commands.argument("provider", StringArgumentType.word())
                                 .suggests((context, builder) -> {
                                     for (var deck : InstabilityProviderCatalog.Deck.values()) for (var card : InstabilityProviderCatalog.cards(deck))

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

@@ -9,11 +9,21 @@ public final class PortInstabilityConfig {
     private static ModConfigSpec.BooleanValue enabled, status, players, nonplayers, hostiles, worldMutation, decay;
     private static ModConfigSpec.IntValue cooldown, ages, providers, actions, level, chunks, active, candidates, duration, decayAttempts;
     private static ModConfigSpec.ConfigValue<List<? extends String>> disabledProviders;
+    private static ModConfigSpec.BooleanValue hazards, hazardBlocks, hazardPlayers, hazardFire;
+    private static ModConfigSpec.IntValue hazardInterval, hazardChunks, hazardMaxBlocks, hazardEntities, hazardDamage, hazardRadius;
+    private static ModConfigSpec.BooleanValue meteor, meteorBlocks, meteorPlayers, meteorFire;
+    private static ModConfigSpec.IntValue meteorMaxBlocks, meteorEntities, meteorDamage;
+    private static ModConfigSpec.BooleanValue scorch, scorchPlayers, erosion;
+    private static ModConfigSpec.IntValue scorchTargets;
+    private static ModConfigSpec.IntValue difficulty;
+    private static ModConfigSpec.ConfigValue<List<? extends String>> materialOverrides;
     private PortInstabilityConfig() {}
     public static void define(ModConfigSpec.Builder builder) {
         builder.push("instability");
         enabled = builder.comment("Run implemented instability providers. Saved scores and plans remain unchanged when disabled.")
                 .define("enabled", true);
+        difficulty = builder.comment("Legacy instability difficulty: 0=quarter, 1=half, 2=normal, 3=1.75x; saved scores stay unchanged.")
+                .defineInRange("difficulty", 2, 0, 3);
         worldMutation = builder.comment("Allow implemented instability providers to change blocks, as in 1.21.1.")
                 .define("world_mutation", true);
         cooldown = builder.defineInRange("cooldown_ticks", 20, 20, 1200);
@@ -42,7 +52,77 @@ public final class PortInstabilityConfig {
         decayAttempts = builder.comment("Maximum six-neighbor conversion attempts per provider call; at most one block changes.")
                 .defineInRange("max_attempts_per_call", 4, 1, 6);
         builder.pop();
+        builder.push("instability_hazards");
+        hazards = builder.comment("Run Legacy lightning and explosion cards in loaded Ages.").define("enabled", true);
+        hazardBlocks = builder.comment("Allow block destruction; also requires world_mutation and mobGriefing.").define("block_damage", true);
+        hazardPlayers = builder.comment("Allow damage to Survival/Adventure players.").define("player_damage", true);
+        hazardFire = builder.comment("Allow ignition where the vanilla fire-spread rule permits it.").define("fire", true);
+        hazardInterval = builder.defineInRange("minimum_gap_ticks", 20, 20, 12000);
+        hazardChunks = builder.defineInRange("max_loaded_chunks", 81, 1, 169);
+        hazardMaxBlocks = builder.defineInRange("max_explosion_blocks", 16, 0, 64);
+        hazardEntities = builder.defineInRange("max_damaged_entities", 8, 0, 32);
+        hazardDamage = builder.defineInRange("max_entity_damage", 12, 0, 40);
+        hazardRadius = builder.comment("Legacy strength 3, bounded to one already-loaded chunk.").defineInRange("explosion_radius", 3, 1, 3);
+        builder.pop();
+        builder.push("instability_meteor");
+        meteor = builder.comment("Run the active Legacy meteor card in loaded Ages.").define("enabled", true);
+        meteorBlocks = builder.comment("Allow impact block destruction; also requires world_mutation and mobGriefing.")
+                .define("block_damage", true);
+        meteorPlayers = builder.comment("Allow impacts to hurt Survival/Adventure players.").define("player_damage", true);
+        meteorFire = builder.comment("Allow impact fire where the vanilla fire-spread rule permits it.").define("fire", true);
+        meteorMaxBlocks = builder.defineInRange("max_impact_blocks", 24, 0, 64);
+        meteorEntities = builder.defineInRange("max_damaged_entities", 8, 0, 32);
+        meteorDamage = builder.defineInRange("max_entity_damage", 12, 0, 40);
+        builder.pop();
+        builder.push("instability_scorching");
+        scorch = builder.comment("Run Legacy's active burning card on sky-exposed entities.").define("enabled", true);
+        scorchPlayers = builder.comment("Allow burning on Survival/Adventure players.").define("affect_players", true);
+        scorchTargets = builder.defineInRange("max_targets_per_pass", 4, 0, 16);
+        builder.pop();
+        builder.push("instability_erosion");
+        erosion = builder.comment("Enable Legacy's dormant erosion effect for testing; no saved card is added.",
+                "Ages with a score of at least 10000 can spread adjacent source fluid into one eligible block per pass.")
+                .define("enabled", true);
+        builder.pop();
+        builder.push("instability_modded_materials");
+        materialOverrides = builder.comment("Recognized ores, mineral blocks and source fluids from installed mods are scored automatically.",
+                "Optional exact modid:block_id=points overrides; zero excludes a block. No content mod is required.")
+                .defineListAllowEmpty("block_weight_overrides", List.of(), () -> "examplemod:rare_ore=4000", PortInstabilityConfig::validMaterialOverride);
+        builder.pop();
     }
+    private static boolean validMaterialOverride(Object value) {
+        if (!(value instanceof String entry)) return false;
+        int separator = entry.lastIndexOf('=');
+        if (separator < 1) return false;
+        Identifier id = Identifier.tryParse(entry.substring(0, separator));
+        if (id == null || !entry.substring(0, separator).contains(":")
+                || id.getNamespace().equals("minecraft") || id.getNamespace().equals("rivencraft")) return false;
+        try { int weight = Integer.parseInt(entry.substring(separator + 1)); return weight >= 0 && weight <= 100000; }
+        catch (NumberFormatException ignored) { return false; }
+    }
+    public static int instabilityDifficulty() { return difficulty.get(); }
+    public static List<? extends String> moddedMaterialOverrides() { return materialOverrides.get(); }
+    public static boolean scorchEnabled() { return scorch.get(); }
+    public static boolean scorchPlayers() { return scorchPlayers.get(); }
+    public static int scorchMaxTargets() { return scorchTargets.get(); }
+    public static boolean erosionEnabled() { return erosion.get(); }
+    public static boolean meteorEnabled() { return meteor.get(); }
+    public static boolean meteorBlockDamage() { return meteorBlocks.get(); }
+    public static boolean meteorPlayerDamage() { return meteorPlayers.get(); }
+    public static boolean meteorFire() { return meteorFire.get(); }
+    public static int meteorMaxBlocks() { return meteorMaxBlocks.get(); }
+    public static int meteorMaxEntities() { return meteorEntities.get(); }
+    public static int meteorMaxDamage() { return meteorDamage.get(); }
+    public static boolean hazardsEnabled() { return hazards.get(); }
+    public static boolean hazardsBlockDamage() { return hazardBlocks.get(); }
+    public static boolean hazardsPlayerDamage() { return hazardPlayers.get(); }
+    public static boolean hazardsFire() { return hazardFire.get(); }
+    public static int hazardsMinInterval() { return hazardInterval.get(); }
+    public static int hazardsMaxChunks() { return hazardChunks.get(); }
+    public static int hazardsMaxBlocks() { return hazardMaxBlocks.get(); }
+    public static int hazardsMaxEntities() { return hazardEntities.get(); }
+    public static int hazardsMaxDamage() { return hazardDamage.get(); }
+    public static int hazardsExplosionRadius() { return hazardRadius.get(); }
     public static boolean instabilityWorldMutation() { return worldMutation.get(); }
     public static boolean decayEnabled() { return decay.get(); }
     public static int decayMaxAttempts() { return decayAttempts.get(); }

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

@@ -47,6 +47,11 @@ public final class PortInstabilityData extends SavedData {
         return age != null ? age : new Age(level.getSeed(),
                 List.of(new Contribution("predates_instability", -1, 0)), PortInstabilityPlan.empty(), true);
     }
+    /** Older neutral Ages stay neutral even if an arrival or enabled flag was later saved. */
+    public boolean supportsProfiling(ServerLevel level) {
+        Age state = ages.get(level.dimension().identifier());
+        return state != null && state.contributions().stream().noneMatch(cost -> cost.reason().equals("predates_instability"));
+    }
     public void enabled(ServerLevel level, boolean enabled) {
         Age previous = age(level);
         ages.put(level.dimension().identifier(), new Age(previous.seed(), previous.contributions(), previous.plan(), enabled, previous.spawn()));
@@ -66,6 +71,8 @@ public final class PortInstabilityData extends SavedData {
         if (ages.containsKey(id)) throw new IllegalArgumentException("Instability already recorded for " + id);
         List<Contribution> costs = new ArrayList<>();
         costs.add(new Contribution(pages.isEmpty() ? "random_baseline" : "authored_baseline", -1, 0));
+        for (var diagnostic : net.dnorberg.rivencraft.writing.PortWritingRecovery.recover(pages).diagnostics())
+            costs.add(new Contribution("writing_" + diagnostic.code(), diagnostic.index(), diagnostic.points()));
         boolean authoredBright = false;
         Map<Identifier, Integer> structures = new HashMap<>();
         var biomes = level.getChunkSource().getGenerator().getBiomeSource().possibleBiomes().stream()

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

@@ -20,6 +20,8 @@ import net.neoforged.neoforge.event.tick.LevelTickEvent;
 /** The 1.21.1 bounded Age scheduler. Unported cards remain saved and visibly unavailable to operators. */
 @EventBusSubscriber(modid = Rivencraft.MOD_ID)
 public final class PortInstabilityRuntime {
+    private static final Map<ServerLevel, CachedPlan> PLANS = new WeakHashMap<>();
+    private record CachedPlan(int score, long seed, PortInstabilityPlan plan) {}
     private static final Map<Identifier, Handler> HANDLERS = new HashMap<>();
     private static final Map<ServerLevel, Map<Identifier, Long>> FAILURES = new WeakHashMap<>();
     private static final Map<MinecraftServer, Map<Identifier, Integer>> TEST_SCORES = new WeakHashMap<>();
@@ -35,12 +37,27 @@ public final class PortInstabilityRuntime {
     public static boolean isAge(ServerLevel level) { return level instanceof PortAgeLevel; }
     public static PortInstabilityPlan plan(ServerLevel level) {
         var age = PortInstabilityData.get(level.getServer()).age(level);
-        Integer test = TEST_SCORES.getOrDefault(level.getServer(), Map.of()).get(level.dimension().identifier());
-        return test == null ? age.plan() : PortInstabilityPlan.select(test, age.seed());
+        Integer test = testScore(level);
+        int profile = test == null ? PortBlockInstability.score(level) : 0;
+        int difficulty = PortInstabilityConfig.instabilityDifficulty();
+        if (test == null && difficulty == 2 && profile == 0) return age.plan();
+        int score = test != null ? test : PortBlockInstability.difficultyScore((long) age.score() + profile, difficulty);
+        var cached = PLANS.get(level);
+        if (cached == null || cached.score() != score || cached.seed() != age.seed()) {
+            cached = new CachedPlan(score, age.seed(), PortInstabilityPlan.select(score, age.seed()));
+            PLANS.put(level, cached);
+        }
+        return cached.plan();
     }
     public static Integer testScore(ServerLevel level) {
         return TEST_SCORES.getOrDefault(level.getServer(), Map.of()).get(level.dimension().identifier());
     }
+    public static int effectiveScore(ServerLevel level) {
+        Integer test = testScore(level);
+        if (test != null) return test;
+        return PortBlockInstability.difficultyScore((long) PortInstabilityData.get(level.getServer()).age(level).score()
+                + PortBlockInstability.score(level), PortInstabilityConfig.instabilityDifficulty());
+    }
     public static void testScore(ServerLevel level, Integer score) {
         var values = TEST_SCORES.computeIfAbsent(level.getServer(), ignored -> new HashMap<>());
         if (score == null) values.remove(level.dimension().identifier()); else values.put(level.dimension().identifier(), score);
@@ -69,6 +86,9 @@ public final class PortInstabilityRuntime {
         var age = PortInstabilityData.get(server).age(level);
         if (!age.enabled()) return;
         var providers = plan(level).providers();
+        PortHazardProviders.tickPlanned(level, age, tick, providers);
+        PortMeteorProvider.tickPlanned(level, age, tick, providers);
+        PortEnvironmentalProviders.tickPlanned(level, age, tick, providers);
         var chunks = loadedChunks(level);
         if (providers.isEmpty() || chunks.isEmpty()) return;
         Context context = new Context(level, age, chunks, tick, new Budget(PortInstabilityConfig.instabilityMaxActions()));
@@ -77,7 +97,8 @@ public final class PortInstabilityRuntime {
         for (int offset = 0; offset < providers.size() && ran < PortInstabilityConfig.instabilityMaxProviders()
                 && context.budget().remaining() > 0; offset++) {
             var provider = providers.get((first + offset) % providers.size());
-            if (invoke(context, provider.id(), provider.level())) ran++;
+            if (!PortHazardProviders.isHazard(provider.id()) && !provider.id().equals(PortMeteorProvider.METEORS)
+                    && !PortEnvironmentalProviders.isEnvironmental(provider.id()) && invoke(context, provider.id(), provider.level())) ran++;
         }
     }
     public static boolean invoke(Context context, Identifier id, int level) {
@@ -101,9 +122,21 @@ public final class PortInstabilityRuntime {
         if (!PortInstabilityConfig.instabilityEnabled()) return "global config off";
         if (!PortInstabilityData.get(level.getServer()).age(level).enabled()) return "Age disabled";
         if (!PortInstabilityConfig.instabilityProviderEnabled(id)) return "provider config off";
-        if (HANDLERS.get(id).worldMutating()) {
+        if (PortHazardProviders.isHazard(id)) {
+            if (!PortInstabilityConfig.hazardsEnabled()) return "hazards config off";
+        } else if (id.equals(PortMeteorProvider.METEORS)) {
+            if (!PortInstabilityConfig.meteorEnabled()) return "meteor config off";
+        } else if (id.equals(PortEnvironmentalProviders.BURNING)) {
+            if (!PortInstabilityConfig.scorchEnabled()) return "burning config off";
+            if (PortInstabilityConfig.scorchMaxTargets() == 0) return "burning target budget zero";
+        } else if (HANDLERS.get(id).worldMutating()) {
             if (!PortInstabilityConfig.instabilityWorldMutation()) return "world mutation off";
             if (id.getPath().startsWith("decay") && !PortInstabilityConfig.decayEnabled()) return "decay config off";
+            if (id.equals(PortEnvironmentalProviders.EROSION)) {
+                if (!PortInstabilityConfig.erosionEnabled()) return "erosion config off";
+                if (!PortHazardProviders.canMutate(level)) return "mobGriefing off";
+                if (effectiveScore(level) < InstabilityProviderCatalog.Deck.DESTRUCTIVE.entryCost()) return "erosion threshold not met";
+            }
         } else {
             if (!PortInstabilityConfig.statusEffectsEnabled()) return "status effects config off";
             if (id.getPath().startsWith("enemy") && !PortInstabilityConfig.statusEffectsHostiles()) return "hostile buffs disabled";
@@ -126,7 +159,7 @@ public final class PortInstabilityRuntime {
         return List.copyOf(chunks);
     }
     @SubscribeEvent public static void stopping(ServerStoppingEvent event) {
-        TEST_SCORES.remove(event.getServer()); TICKS.remove(event.getServer()); FAILURES.clear();
+        TEST_SCORES.remove(event.getServer()); TICKS.remove(event.getServer()); FAILURES.clear(); PLANS.clear();
     }
     public interface ProviderEffect { void apply(Context context, Identifier id, int level); }
     public record Context(ServerLevel level, PortInstabilityData.Age age, List<ChunkPos> loadedChunks,

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

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

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

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

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

@@ -34,7 +34,8 @@ public final class BookReceptacleBlockEntity extends BlockEntity {
             var target = id == null ? null : source.getServer().getLevel(net.minecraft.resources.ResourceKey.create(
                     net.minecraft.core.registries.Registries.DIMENSION, id));
             if (target != null) {
-                var pos = destination == null ? net.dnorberg.rivencraft.age.PortAgeTravel.resolveLanding(target)
+                var pos = destination == null ? net.dnorberg.rivencraft.age.PortAgeTravel.resolveLanding(target, !book.getOrDefault(Rivencraft.LINK_PROPERTIES.get(),
+                        net.dnorberg.rivencraft.item.LinkProperties.NONE).has(net.dnorberg.rivencraft.item.LinkProperties.DISABLE_PLATFORM))
                         : BlockPos.containing(destination.x(), destination.y(), destination.z());
                 if (pos != null) {
                     int written = net.dnorberg.rivencraft.age.PortAgeColors.forLevel(target).sky();

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

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

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

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

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

@@ -43,6 +43,7 @@ public final class PortBookBinderClientEvents {
     public static void registerScreens(RegisterMenuScreensEvent event) {
         event.register(Rivencraft.BOOK_BINDER_MENU.get(), PortBookBinderScreen::new);
         event.register(Rivencraft.INK_MIXER_MENU.get(), InkMixerScreen::new);
+        event.register(Rivencraft.LINK_MODIFIER_MENU.get(), LinkModifierScreen::new);
         event.register(Rivencraft.NOTEBOOK_MENU.get(), NotebookScreen::new);
         event.register(Rivencraft.WRITING_DESK_MENU.get(), WritingDeskScreen::new);
     }

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

@@ -36,5 +36,6 @@ public final class DescriptiveBookItem extends Item {
                                 Consumer<Component> tooltip, TooltipFlag flag) {
         Identifier id = stack.get(Rivencraft.AGE_BOOK_ID.get());
         tooltip.accept(Component.literal(id == null ? "Unbound (26.3 port preview)" : "Age: " + id));
+        stack.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE).forDescriptiveBook().appendTooltip(tooltip);
     }
 }

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

@@ -5,12 +5,17 @@ import io.netty.buffer.ByteBuf;
 import net.minecraft.network.codec.ByteBufCodecs;
 import net.minecraft.network.codec.StreamCodec;
 
-/** The three Ink Mixer modifiers currently supported by the 26.3 port. */
+/** Link Panel flags shared by the mixer, books and Link Modifier station. */
 public record LinkProperties(int flags) {
     public static final int DISARM = 1;
+    public static final int GENERATE_PLATFORM = 2;
+    public static final int INTRA_LINKING_ONLY = 16;
+    public static final int RELATIVE_LINK = 32;
+    public static final int DISABLE_PLATFORM = 64;
     public static final int MAINTAIN_MOMENTUM = 4;
     public static final int INTRA_LINKING = 8;
-    public static final int SUPPORTED = DISARM | MAINTAIN_MOMENTUM | INTRA_LINKING;
+    public static final int SUPPORTED = DISARM | GENERATE_PLATFORM | MAINTAIN_MOMENTUM | INTRA_LINKING
+            | INTRA_LINKING_ONLY | RELATIVE_LINK | DISABLE_PLATFORM;
     public static final LinkProperties NONE = new LinkProperties(0);
     public static final Codec<LinkProperties> CODEC = Codec.INT.xmap(LinkProperties::new, LinkProperties::flags);
     public static final StreamCodec<ByteBuf, LinkProperties> STREAM_CODEC = StreamCodec.of(
@@ -23,6 +28,18 @@ public record LinkProperties(int flags) {
         }
     }
 
+    public boolean allowsTravel(boolean sameDimension) {
+        return sameDimension ? has(INTRA_LINKING) || has(INTRA_LINKING_ONLY) : !has(INTRA_LINKING_ONLY);
+    }
+    public LinkProperties forDescriptiveBook() {
+        return new LinkProperties(flags & ~(INTRA_LINKING | INTRA_LINKING_ONLY));
+    }
+    public void appendTooltip(java.util.function.Consumer<net.minecraft.network.chat.Component> tooltip) {
+        int[] flags = {DISARM, MAINTAIN_MOMENTUM, INTRA_LINKING, INTRA_LINKING_ONLY, RELATIVE_LINK, GENERATE_PLATFORM, DISABLE_PLATFORM};
+        String[] names = {"disarm", "maintain_momentum", "intra_linking", "intra_linking_only", "relative_link", "generate_platform", "disable_platform"};
+        for (int i = 0; i < flags.length; i++) if (has(flags[i]))
+            tooltip.accept(net.minecraft.network.chat.Component.translatable("item.rivencraft.link_property." + names[i]));
+    }
     public boolean has(int flag) {
         return (flags & flag) != 0;
     }

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

@@ -48,7 +48,7 @@ public final class LinkingBookItem extends Item {
         if (destination == null) return "Unbound Linking Book (26.3 port preview)";
         if (!destination.valid()) return "Invalid Linking Book destination";
         if (player.level().dimension().identifier().equals(destination.dimension())
-                && !properties.has(LinkProperties.INTRA_LINKING)) {
+                && !properties.allowsTravel(true)) {
             return "Same-dimension linking requires an Intra-Linking page";
         }
         ServerLevel target = player.level().getServer().getLevel(
@@ -57,11 +57,13 @@ public final class LinkingBookItem extends Item {
         if (!AgeCatalogSync.ready(player, destination.dimension())) {
             return "Destination catalog not acknowledged by client";
         }
+        if (!properties.allowsTravel(target == player.level())) return "Intra-Linking Only cannot travel between dimensions";
+        destination = PortLinkDestinations.resolve(player.level(), target, player.blockPosition(), destination, properties);
+        if (!destination.valid()) return "Invalid relative destination";
         BlockPos feet = BlockPos.containing(destination.x(), destination.y(), destination.z());
         if (feet.getY() < target.getMinY() || feet.getY() + 1 >= target.getMaxY()
-                || !target.getWorldBorder().isWithinBounds(feet)) {
-            return "Destination is outside the world bounds";
-        }
+                || !target.getWorldBorder().isWithinBounds(feet)) return "Destination is outside the world bounds";
+        target.getChunkAt(feet);
         // Test the player's actual arrival volume: checking whole block shapes
         // would incorrectly reject links bound while standing on a slab.
         if (!target.noCollision(player, player.getBoundingBox().move(
@@ -74,7 +76,10 @@ public final class LinkingBookItem extends Item {
         Vec3 incoming = player.getDeltaMovement();
         boolean moved = player.teleportTo(target, destination.x(), destination.y(), destination.z(),
                 Set.of(), destination.yaw(), destination.pitch(), true);
-        if (moved) applySuccessfulLink(player, properties, source, departure, incoming, destination.yaw(), portal);
+        if (moved) {
+            PortLinkDestinations.generatePlatform(target, player.position(), properties);
+            applySuccessfulLink(player, properties, source, departure, incoming, destination.yaw(), portal);
+        }
         return moved ? null : "Teleportation failed";
     }
 
@@ -133,11 +138,6 @@ public final class LinkingBookItem extends Item {
                     destinationName(stack, target).getString(), pos.getX(), pos.getY(), pos.getZ()));
         }
         LinkProperties properties = stack.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE);
-        if (properties.has(LinkProperties.DISARM))
-            tooltip.accept(Component.translatable("item.rivencraft.link_property.disarm"));
-        if (properties.has(LinkProperties.MAINTAIN_MOMENTUM))
-            tooltip.accept(Component.translatable("item.rivencraft.link_property.maintain_momentum"));
-        if (properties.has(LinkProperties.INTRA_LINKING))
-            tooltip.accept(Component.translatable("item.rivencraft.link_property.intra_linking"));
+        properties.appendTooltip(tooltip);
     }
 }

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

@@ -96,15 +96,7 @@ public final class PageItem extends Item {
             return;
         }
         LinkProperties properties = stack.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE);
-        if (properties.has(LinkProperties.DISARM))
-            tooltip.accept(Component.translatable("item.rivencraft.link_property.disarm"));
-        if (properties.has(LinkProperties.MAINTAIN_MOMENTUM))
-            tooltip.accept(Component.translatable("item.rivencraft.link_property.maintain_momentum"));
-        if (properties.has(LinkProperties.INTRA_LINKING))
-            tooltip.accept(Component.translatable("item.rivencraft.link_property.intra_linking"));
-        tooltip.accept(Component.translatable(isLinkPanel(stack)
-                ? "item.rivencraft.page.link_panel.port_status"
-                : "item.rivencraft.page.blank.port_status"));
+        properties.appendTooltip(tooltip);
     }
 
     private static boolean isCorrupted(Identifier id) {

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

@@ -0,0 +1,30 @@
+package net.dnorberg.rivencraft.item;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.phys.Vec3;
+
+/** 1.21.1 Relative Link and optional Linking Book arrival-floor rules. */
+public final class PortLinkDestinations {
+    private PortLinkDestinations() {}
+    public static BlockPos relativeOrigin(BlockPos sourceSpawn, BlockPos destinationSpawn, BlockPos departure) {
+        return destinationSpawn.offset(departure.getX() - sourceSpawn.getX(), departure.getY() - sourceSpawn.getY(),
+                departure.getZ() - sourceSpawn.getZ());
+    }
+    public static BlockPos relativeOrigin(ServerLevel source, ServerLevel target, BlockPos departure) {
+        return relativeOrigin(source.getRespawnData().pos(), target.getRespawnData().pos(), departure);
+    }
+    public static LinkBookTarget resolve(ServerLevel source, ServerLevel target, BlockPos departure,
+                                          LinkBookTarget written, LinkProperties properties) {
+        if (!properties.has(LinkProperties.RELATIVE_LINK)) return written;
+        BlockPos pos = relativeOrigin(source, target, departure);
+        return new LinkBookTarget(written.dimension(), pos.getX() + 0.5, pos.getY(), pos.getZ() + 0.5, written.yaw(), written.pitch());
+    }
+    public static void generatePlatform(ServerLevel level, Vec3 arrival, LinkProperties properties) {
+        if (!properties.has(LinkProperties.GENERATE_PLATFORM)) return;
+        BlockPos feet = BlockPos.containing(arrival), floor = feet.below();
+        if (level.isEmptyBlock(floor) && level.isEmptyBlock(feet.above(2)))
+            level.setBlock(floor, Rivencraft.CLOUD_PLATFORM.get().defaultBlockState(), 3);
+    }
+}

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

@@ -0,0 +1,94 @@
+package net.dnorberg.rivencraft.menu;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.entity.LinkModifierBlockEntity;
+import net.dnorberg.rivencraft.item.LinkProperties;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.chat.Component;
+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.Slot;
+import net.minecraft.world.item.ItemStack;
+
+/** 1.21.1's persistent single-book editing station, adapted to 26.3. */
+public final class LinkModifierMenu extends AbstractContainerMenu {
+    public static final int TOGGLE_DISARM = 1, TOGGLE_MOMENTUM = 2, TOGGLE_INTRA = 3,
+            TOGGLE_INTRA_ONLY = 5, TOGGLE_RELATIVE = 6, TOGGLE_PLATFORM = 7;
+    private final LinkModifierBlockEntity modifier;
+    private final Container books;
+    private final Player owner;
+    public LinkModifierMenu(int id, Inventory inventory, RegistryFriendlyByteBuf data) {
+        this(id, inventory, inventory.player.level().getBlockEntity(data.readBlockPos())
+                instanceof LinkModifierBlockEntity found ? found : null);
+    }
+    public LinkModifierMenu(int id, Inventory inventory, LinkModifierBlockEntity modifier) {
+        super(Rivencraft.LINK_MODIFIER_MENU.get(), id);
+        this.modifier = modifier;
+        books = modifier == null ? new SimpleContainer(1) : modifier;
+        owner = inventory.player;
+        addSlot(new Slot(books, 0, 80, 35) {
+            @Override public boolean mayPlace(ItemStack stack) { return isBook(stack); }
+            @Override public int getMaxStackSize() { return 1; }
+        });
+        for (int row = 0; row < 3; row++) for (int col = 0; col < 9; col++)
+            addSlot(new Slot(inventory, col + row * 9 + 9, 8 + col * 18, 84 + row * 18));
+        for (int col = 0; col < 9; col++) addSlot(new Slot(inventory, col, 8 + col * 18, 142));
+    }
+    private static boolean isBook(ItemStack stack) {
+        return stack.is(Rivencraft.LINKING_BOOK.get()) || stack.is(Rivencraft.DESCRIPTIVE_BOOK.get());
+    }
+    public ItemStack book() { return books.getItem(0); }
+    public boolean setTitle(Player player, String title) {
+        if (player.level().isClientSide() || !stillValid(player) || !isBook(book())
+                || title == null || title.length() > 32) return false;
+        String clean = title.strip();
+        if (clean.isEmpty()) book().remove(DataComponents.CUSTOM_NAME);
+        else book().set(DataComponents.CUSTOM_NAME, Component.literal(clean));
+        books.setChanged();
+        broadcastChanges();
+        return true;
+    }
+    @Override public boolean clickMenuButton(Player player, int id) {
+        if (player.level().isClientSide() || !stillValid(player) || !isBook(book())) return false;
+        int flag = switch (id) {
+            case TOGGLE_DISARM -> LinkProperties.DISARM;
+            case TOGGLE_MOMENTUM -> LinkProperties.MAINTAIN_MOMENTUM;
+            case TOGGLE_INTRA -> LinkProperties.INTRA_LINKING;
+            case TOGGLE_INTRA_ONLY -> LinkProperties.INTRA_LINKING_ONLY;
+            case TOGGLE_RELATIVE -> LinkProperties.RELATIVE_LINK;
+            case TOGGLE_PLATFORM -> book().is(Rivencraft.LINKING_BOOK.get())
+                    ? LinkProperties.GENERATE_PLATFORM : LinkProperties.DISABLE_PLATFORM;
+            default -> 0;
+        };
+        // Descriptive Books travel to an Age; Intra Linking is a Linking Book property.
+        if (flag == 0 || (flag == LinkProperties.INTRA_LINKING || flag == LinkProperties.INTRA_LINKING_ONLY) && book().is(Rivencraft.DESCRIPTIVE_BOOK.get())) return false;
+        int flags = book().getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE).flags();
+        if (flag == LinkProperties.INTRA_LINKING_ONLY && (flags & LinkProperties.INTRA_LINKING_ONLY) == 0)
+            flags |= LinkProperties.INTRA_LINKING;
+        if (flag == LinkProperties.INTRA_LINKING && (flags & LinkProperties.INTRA_LINKING) != 0)
+            flags &= ~LinkProperties.INTRA_LINKING_ONLY;
+        book().set(Rivencraft.LINK_PROPERTIES.get(), new LinkProperties(flags ^ flag));
+        books.setChanged();
+        broadcastChanges();
+        return true;
+    }
+    @Override public boolean stillValid(Player player) {
+        return player == owner && modifier != null && modifier.stillValid(player);
+    }
+    @Override public ItemStack quickMoveStack(Player player, int index) {
+        if (!stillValid(player) || index < 0 || index >= slots.size()) return ItemStack.EMPTY;
+        Slot slot = slots.get(index);
+        if (!slot.hasItem()) return ItemStack.EMPTY;
+        ItemStack source = slot.getItem(), copy = source.copy();
+        if (index == 0) {
+            if (!moveItemStackTo(source, 1, slots.size(), true)) return ItemStack.EMPTY;
+        } else if (!moveItemStackTo(source, 0, 1, false)) return ItemStack.EMPTY;
+        if (source.isEmpty()) slot.set(ItemStack.EMPTY);
+        else slot.setChanged();
+        return copy;
+    }
+}

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

@@ -33,6 +33,12 @@ public final class PortBookNetworking {
 
     public static void registerPayloads(RegisterPayloadHandlersEvent event) {
         var registrar = event.registrar("1");
+        registrar.playToServer(SetLinkModifierTitlePayload.TYPE, SetLinkModifierTitlePayload.STREAM_CODEC,
+                (payload, context) -> {
+                    if (context.player() instanceof ServerPlayer player
+                            && player.containerMenu instanceof net.dnorberg.rivencraft.menu.LinkModifierMenu menu
+                            && menu.containerId == payload.containerId()) menu.setTitle(player, payload.title());
+                });
         registrar.playToClient(WritingDeskCatalogPayload.TYPE, WritingDeskCatalogPayload.STREAM_CODEC);
         registrar.playToServer(BindLinkingBookPayload.TYPE, BindLinkingBookPayload.STREAM_CODEC,
                 (payload, context) -> {
@@ -117,6 +123,8 @@ public final class PortBookNetworking {
     public static Identifier createAge(ServerPlayer player, String title, List<Identifier> pages) {
         if (title == null || title.isBlank() || title.length() > MAX_BOOK_TITLE_LENGTH) return null;
         long seed = player.getRandom().nextLong();
+        var recovery = net.dnorberg.rivencraft.writing.PortWritingRecovery.recover(pages);
+        List<Identifier> activePages = recovery.activePages();
         net.dnorberg.rivencraft.age.PortBiomePlan biomePlan;
         PortAgeTerrain terrain;
         List<Identifier> generationPages;
@@ -148,7 +156,7 @@ public final class PortBookNetworking {
             id = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age/" + name);
         }
         try {
-            var environment = net.dnorberg.rivencraft.age.PortEnvironmentSelection.resolve(pages, seed, terrain);
+            var environment = net.dnorberg.rivencraft.age.PortEnvironmentSelection.resolve(activePages, seed, terrain);
             var randomFeatures = pages.isEmpty()
                     ? net.dnorberg.rivencraft.age.PortRandomFeatureSelection.select(server, seed, terrain, biomePlan) : null;
             var level = RuntimeAgeBackend.create(server, id, seed, biomePlan, terrain,
@@ -210,7 +218,8 @@ public final class PortBookNetworking {
         Vec3 departure = player.position();
         Vec3 incoming = player.getDeltaMovement();
         java.util.function.Supplier<String> travel = () -> {
-            String result = PortAgeTravel.enter(player, id);
+            String result = PortAgeTravel.enter(player, id,
+                    stack.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE).forDescriptiveBook());
             if (result == null) LinkingBookItem.applySuccessfulLink(player,
                     stack.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE),
                     source, departure, incoming, player.getYRot(), portal);

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

@@ -0,0 +1,18 @@
+package net.dnorberg.rivencraft.network;
+
+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.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.Identifier;
+
+public record SetLinkModifierTitlePayload(int containerId, String title) implements CustomPacketPayload {
+    public static final Type<SetLinkModifierTitlePayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "set_link_modifier_title"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, SetLinkModifierTitlePayload> STREAM_CODEC =
+            StreamCodec.composite(ByteBufCodecs.VAR_INT, SetLinkModifierTitlePayload::containerId,
+                    ByteBufCodecs.stringUtf8(32), SetLinkModifierTitlePayload::title,
+                    SetLinkModifierTitlePayload::new);
+    @Override public Type<SetLinkModifierTitlePayload> type() { return TYPE; }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/portal/PortalBookTravel.java

@@ -43,14 +43,17 @@ public final class PortalBookTravel {
             var id = book.get(Rivencraft.AGE_BOOK_ID.get());
             ServerLevel level = id == null ? null : source.getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
             if (level == null) return;
-            var landing = PortAgeTravel.resolveLanding(level);
+            var landing = PortAgeTravel.resolveLanding(level, entity, properties.forDescriptiveBook());
             if (landing == null) return;
             destination = new LinkBookTarget(id, landing.getX() + 0.5, landing.getY(), landing.getZ() + 0.5,
                     entity.getYRot(), entity.getXRot());
         }
         if (destination == null || !destination.valid()) return;
         ServerLevel target = source.getServer().getLevel(ResourceKey.create(Registries.DIMENSION, destination.dimension()));
-        if (target == null || !entity.canTeleport(source, target) || !descriptive && target == source && !properties.has(LinkProperties.INTRA_LINKING)) return;
+        if (target == null || !entity.canTeleport(source, target) || !descriptive && !properties.allowsTravel(target == source)) return;
+        if (!descriptive) destination = net.dnorberg.rivencraft.item.PortLinkDestinations.resolve(source, target,
+                entity.blockPosition(), destination, properties);
+        if (!destination.valid()) return;
         var feet = net.minecraft.core.BlockPos.containing(destination.x(), destination.y(), destination.z());
         if (feet.getY() < target.getMinY() || entity.getBbHeight() + feet.getY() >= target.getMaxY()
                 || !target.getWorldBorder().isWithinBounds(feet)) return;
@@ -68,6 +71,7 @@ public final class PortalBookTravel {
         Entity arrived = entity.teleport(new TeleportTransition(target, arrival, velocity, destination.yaw(),
                 destination.pitch(), TeleportTransition.PLACE_PORTAL_TICKET));
         if (arrived == null) return;
+        if (!descriptive) net.dnorberg.rivencraft.item.PortLinkDestinations.generatePlatform(target, arrival, properties);
         if (properties.has(LinkProperties.DISARM)) {
             LinkDisarmService.disarmAt(arrived, source, departure);
         }

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

@@ -33,6 +33,7 @@ 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.LINK_MODIFIER_ITEM.get());
                     output.accept(Rivencraft.WRITING_DESK_ITEM.get());
                     output.accept(Rivencraft.NOTEBOOK.get());
                     output.accept(Rivencraft.COLLATION_FOLDER.get());

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

@@ -17,6 +17,20 @@ public final class PortAuthoredTerrainSelection {
     }
 
     public static Selection select(MinecraftServer server, List<Identifier> pages, long seed) {
+        if (!net.dnorberg.rivencraft.age.PortDayCycle.validWriting(pages))
+            throw new IllegalArgumentException("An Age may have at most ten suns and ten moons");
+        for (var page : pages) {
+            var entry = PortSymbolPages.find(page);
+            if (entry != null && entry.role().equals("biome")) {
+                var biome = PortRegistryPages.biomeId(page);
+                if (biome == null || server.registryAccess().lookupOrThrow(net.minecraft.core.registries.Registries.BIOME)
+                        .get(net.minecraft.resources.ResourceKey.create(net.minecraft.core.registries.Registries.BIOME, biome)).isEmpty())
+                    throw new IllegalArgumentException("Unknown biome page: " + page);
+            }
+        }
+        var recovered = PortWritingRecovery.recover(pages);
+        if (!recovered.implemented()) throw new IllegalArgumentException("Unimplemented symbol page in this book");
+        pages = recovered.activePages();
         var explicit = PortAuthoredWriting.explicitTerrain(pages);
         if (explicit != null) return compile(server, pages, seed, explicit);
         var preferred = PortRandomAgeSelection.terrain(seed);

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

@@ -72,20 +72,25 @@ public final class PortAuthoredWriting {
                 || PortStructurePages.supports(page) || PortCarverPages.supports(page);
     }
 
-    /** A page never disappears into an Age unless this port can apply its effect. */
+    /** Recover known category defects; unimplemented pages and unsupported runtime combinations still block binding. */
     public static boolean supports(List<Identifier> pages) {
-        if (pages.stream().noneMatch(PortAuthoredWriting::isTerrain))
+        if (!net.dnorberg.rivencraft.age.PortDayCycle.validWriting(pages)) return false;
+        var recovered = PortWritingRecovery.recover(pages);
+        if (!recovered.implemented()) return false;
+        List<Identifier> active = recovered.activePages();
+        if (active.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; }
+                    .anyMatch(terrain -> supportsOnTerrain(active, terrain, 0));
+        try { return supportsExplicit(PortMaterialCompletion.complete(active, 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; }
+        if (!net.dnorberg.rivencraft.age.PortDayCycle.validWriting(pages)) return false;
+        var recovered = PortWritingRecovery.recover(pages);
+        if (!recovered.implemented()) return false;
+        try { return supportsExplicit(PortMaterialCompletion.complete(withTerrain(recovered.activePages(), terrain), seed)); }
+        catch (IllegalArgumentException exception) { return false; }
     }
 
     static List<Identifier> withTerrain(List<Identifier> pages, PortAgeTerrain terrain) {
@@ -104,7 +109,6 @@ public final class PortAuthoredWriting {
     }
 
     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;
         boolean terrain = false;
         int biomes = 0;

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

@@ -101,7 +101,7 @@ public final class PortRegistryPages {
                 || path.equals("deep_dark") || path.endsWith("_caves");
     }
 
-    private static String materialCategory(Block block) {
+    public 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;

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

@@ -17,7 +17,13 @@ import net.dnorberg.rivencraft.item.PageItem;
 
 /** Bundled 1.21.1 symbol identities, shared by the port's creative pages. */
 public final class PortSymbolPages {
-    public record Entry(Identifier id, String category, String nameKey, String descriptionKey, String poem) {}
+    public record Entry(Identifier id, String category, String nameKey, String descriptionKey, String poem, String role) {
+        public Entry(Identifier id, String category, String nameKey, String descriptionKey, String poem) {
+            this(id, category, nameKey, descriptionKey, poem,
+                    category.equals("rivencraft:biome") ? "biome"
+                    : category.equals("rivencraft:block") || category.equals("rivencraft:fluid") ? "block" : "unknown");
+        }
+    }
 
     private static final Map<Identifier, Entry> ENTRIES = load();
 
@@ -100,7 +106,9 @@ public final class PortSymbolPages {
                     category = "rivencraft:biome_generation";
                 entries.put(id, new Entry(id, category, definition.get("name").getAsString(),
                         definition.get("description").getAsString(),
-                        definition.has("poem") ? definition.get("poem").getAsString() : ""));
+                        definition.has("poem") ? definition.get("poem").getAsString() : "",
+                        definition.has("semantics") ? definition.getAsJsonObject("semantics").get("role").getAsString()
+                                : id.getPath().equals("lighting/ambient_color") ? "ambient_color" : "unknown"));
             });
             return Collections.unmodifiableMap(entries);
         } catch (java.io.IOException exception) {

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

@@ -0,0 +1,99 @@
+package net.dnorberg.rivencraft.writing;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import net.minecraft.resources.Identifier;
+
+/** 1.21.1 grammar diagnostics and singular-controller recovery; preserve ordered modifier chains. */
+public final class PortWritingRecovery {
+    private static final Set<String> SINGULAR = Set.of("terrain", "biome_controller", "weather", "season", "lighting", "sky");
+    private static final Set<String> MODIFIERS = Set.of("period_modifier", "angle_modifier", "phase_modifier", "size_modifier",
+            "celestial_color", "direction_modifier");
+    public record Diagnostic(String code, int index, int points) {}
+    public record Result(List<Identifier> activePages, List<Diagnostic> diagnostics, boolean implemented) {
+        public Result { activePages = List.copyOf(activePages); diagnostics = List.copyOf(diagnostics); }
+    }
+    private PortWritingRecovery() {}
+    public static Result recover(List<Identifier> pages) {
+        Map<String, Integer> last = new HashMap<>();
+        List<Diagnostic> diagnostics = new ArrayList<>();
+        boolean implemented = pages.size() <= NotebookContents.MAX_PAGES;
+        int previousStage = -1, biomes = 0;
+        Map<String, Integer> pendingModifiers = new java.util.LinkedHashMap<>();
+        Integer pendingNumber = null;
+        for (int index = 0; index < pages.size(); index++) {
+            Identifier page = pages.get(index);
+            var entry = PortSymbolPages.find(page);
+            if (entry == null || !PortAuthoredWriting.isPageImplemented(page)) { implemented = false; continue; }
+            String role = entry.role();
+            if (pendingNumber != null && !numberTarget(role)) {
+                diagnostics.add(new Diagnostic("misplaced_modifier", pendingNumber, 100));
+                pendingNumber = null;
+            }
+            if (role.equals("color_number")) pendingNumber = index;
+            else if (numberTarget(role)) pendingNumber = null;
+            if (MODIFIERS.contains(role)) pendingModifiers.put(role, index);
+            else if (role.equals("celestial")) pendingModifiers.clear();
+            if (SINGULAR.contains(role)) {
+                Integer prior = last.put(role, index);
+                if (prior != null) {
+                    diagnostics.add(new Diagnostic(pages.get(prior).equals(page) ? "duplicate" : "conflict", index, 500));
+                    // Match WritingGrammar: a repeated singular choice does not also earn an order penalty.
+                    continue;
+                }
+            }
+            if (role.equals("biome")) biomes++;
+            int stage = stage(role);
+            if (stage < previousStage && !MODIFIERS.contains(role) && !role.equals("color") && !role.equals("color_number"))
+                diagnostics.add(new Diagnostic("out_of_order", index, 100));
+            else if (!role.equals("color") && !role.equals("color_number")) previousStage = stage;
+        }
+        if (pendingNumber != null) diagnostics.add(new Diagnostic("dangling_modifier", pendingNumber, 100));
+        for (int index : pendingModifiers.values())
+            diagnostics.add(new Diagnostic("dangling_modifier", index, 100));
+        Integer controller = last.get("biome_controller");
+        boolean nativeBiomes = controller != null && pages.get(controller).getPath().equals("biome/native");
+        boolean single = controller != null && pages.get(controller).getPath().equals("biome/single");
+        if (nativeBiomes && biomes > 0 || single && biomes > 1)
+            diagnostics.add(new Diagnostic("conflict", controller, 500));
+        List<Identifier> active = new ArrayList<>();
+        boolean retainedBiome = false;
+        for (int index = 0; index < pages.size(); index++) {
+            var page = pages.get(index);
+            var entry = PortSymbolPages.find(page);
+            if (entry != null) {
+                String role = entry.role();
+                if (SINGULAR.contains(role) && last.getOrDefault(role, -1) != index) continue;
+                if (role.equals("biome")) {
+                    if (nativeBiomes || single && retainedBiome) continue;
+                    retainedBiome = true;
+                }
+            }
+            active.add(page);
+        }
+        // Keep source order for material pairing and per-celestial modifier chains.
+        // The port's category compilers select by role, so no physical resort is necessary.
+        return new Result(active, diagnostics, implemented);
+    }
+    private static boolean numberTarget(String role) {
+        return role.equals("color") || role.equals("period_modifier") || role.equals("angle_modifier")
+                || role.equals("phase_modifier") || role.equals("size_modifier");
+    }
+    private static int stage(String role) {
+        return switch (role) {
+            case "terrain" -> 0;
+            case "biome" -> 1;
+            case "biome_controller" -> 2;
+            case "weather" -> 3;
+            case "season" -> 4;
+            case "lighting" -> 5;
+            case "sky", "sky_color", "ambient_color", "color", "color_number" -> 6;
+            case "period_modifier", "angle_modifier", "phase_modifier", "size_modifier", "celestial_color", "direction_modifier" -> 7;
+            case "celestial" -> 8;
+            default -> 9;
+        };
+    }
+}

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

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