Port Age lighting and animated sky styles to 26.3 beta

Advance to 1.0.1.54-beta.1 after player validation. Port material, vegetation, lake, terrain-volume, crystal, Dense Ores and fissure features with saved plans. Update beta documentation and release notes.

Refs #98, #104

.gitignore

@@ -32,6 +32,10 @@ bin/
 ### Mac OS ###
 .DS_Store
 
+### Python tools ###
+__pycache__/
+*.pyc
+
 ### Minecraft Modding ###
 run/
 logs/

README.md

@@ -7,9 +7,20 @@ of [Mystcraft Legacy](https://github.com/Mystcraft/Mystcraft-Legacy) to
 Minecraft 1.21.1 on NeoForge. Mystcraft veterans will recognize the writing
 flow, D'ni-inspired glyphs, libraries, crystals, and instability. Rivencraft
 also lets you author modern terrain, biomes, structures, seasons, and celestial
-bodies. It is an active pre-public-release project, not a byte-for-byte copy of
+bodies. It is an independently developed project, not a byte-for-byte copy of
 the 1.12.2 mod.
 
+The gameplay guide below describes the **Minecraft 1.21.1 release**. A separate,
+incomplete **Minecraft 26.3 beta** is available: Java 25, NeoForge 26.3.0.99,
+and a first-party Age backend (no Dynamic Dimensions or Bad Packets). It now
+supports authored terrain/biomes, structure and vegetation pages, independent
+Age weather/lighting, Overworld/Nether/End and animated Static skies,
+and a growing set of generation features,
+but does not yet provide full 1.21.1 gameplay or optional-integration parity.
+See the [26.3 beta guide](ports/mc263/README.md) and
+[latest beta release notes](ports/mc263/RELEASE_NOTES_1.0.1.71-beta.1.md).
+Keep the builds and their saves separate, and back up worlds before updating.
+
 ## Getting started
 
 1. Make an Ink Vial from two black dyes, a glass bottle, and a water bucket.
@@ -95,7 +106,10 @@ to control them; only OPs see the diagnostics even when enabled.
 
 This repository is the development source. See the [current implementation](docs/CURRENT_IMPLEMENTATION.md),
 [milestone summaries](docs/MILESTONES.md), [technical document index](docs/README.md),
-and [issues](https://truenas-scale.tail180fb1.ts.net:8443/dnorberg/rivencraft/issues).
+and [issues](https://git.paddedcell.org/dnorberg/rivencraft/issues).
+Help build the [Rivencraft wiki](https://git.paddedcell.org/dnorberg/rivencraft/wiki)
+with guides for Ages, pages, and crafting, or open an issue with documentation
+suggestions and corrections.
 Milestone 7 is complete in 1.0.0.2. Its [acceptance record](docs/MILESTONE_7_ACCEPTANCE.md)
 and [regression matrix](docs/MILESTONE_7_REGRESSION.md) distinguish automated
 checks from manual evidence and known limitations.

docs/MINECRAFT_26_3_ALPHA_1.md

@@ -0,0 +1,42 @@
+# Rivencraft 1.0.1.2-alpha.1 — Minecraft 26.3
+
+Experimental **NeoForge 26.3** port preview. This is a separate artifact from
+the supported Minecraft 1.21.1 release, and it does **not** have feature
+parity. Use a disposable test world or make a backup first. Do not migrate a
+1.21.1 Rivencraft world to this alpha.
+
+## Working in this alpha
+
+- Rivencraft loads on Minecraft 26.3 / NeoForge 26.3.0.99 with Java 25.
+- The first-party runtime Age backend creates separately seeded, persistent
+  prototype dimensions. The operator-only `/rivencraft_port age` commands can
+  create and inspect them.
+- Runtime Age catalogs are synchronized and acknowledged before cross-dimension
+  travel. A missing or unacknowledged destination is refused.
+- Operator-created Descriptive Books can enter prototype Ages.
+- Handheld Linking Books can be named and bound to a location, then used from
+  their book GUI to return there. The destination data survives a restart.
+- The Crystal Block and Crystal Shard are registered with reused art.
+
+## Not yet ported
+
+Normal authored Age generation, book crafting and workstations, Page symbols,
+most blocks and items, portal systems, Link modifiers, the rotating destination
+preview, instability, and optional mod integrations. The Linking Book GUI shows
+a placeholder destination panel rather than a live scene. Generated Ages use
+prototype vanilla terrain, not the player's authored Pages.
+
+The [26.3 port status](MINECRAFT_26_3_PORT.md) and [open port issues](https://git.paddedcell.org/dnorberg/rivencraft/issues)
+track the remaining work. The stable 1.21.1 release remains available
+separately. Please file alpha bugs with the exact Minecraft, NeoForge and
+Rivencraft versions, plus the relevant client/server log.
+
+## Verification
+
+- Clean 26.3 Gradle build passed.
+- Disposable dedicated-server smoke test passed: two distinct Age seeds and
+  their terrain persisted across a restart.
+- The user verified the handheld Linking Book GUI click and travel in-game on
+  2026-10-27.
+
+These checks are **not** the full port acceptance matrix or a stability claim.

docs/MINECRAFT_26_3_ALPHA_2.md

@@ -0,0 +1,37 @@
+# Rivencraft 1.0.1.3-alpha.1 — Minecraft 26.3
+
+Experimental **NeoForge 26.3** port preview. This is separate from the
+supported Minecraft 1.21.1 release and does **not** have feature parity. Use
+a disposable test world or make a backup first. Do not migrate a 1.21.1
+Rivencraft world to this alpha.
+
+## Changes since 1.0.1.2-alpha.1
+
+- An unbound Descriptive Book now opens a naming screen. Binding it creates a
+  distinct prototype Age with a random seed; duplicate names receive a
+  numbered suffix.
+- A bound Descriptive Book opens a book screen whose destination panel can be
+  clicked to enter its Age. The server validates the held book and waits for
+  the client's Age catalog acknowledgement before travel.
+- Retired Age IDs are excluded when assigning a new book's Age name, so an
+  archived world cannot be silently reused.
+
+## Still experimental
+
+These Ages use prototype vanilla terrain. Page-authored generation, crafting
+and workstations, most items and blocks, portals, Link modifiers, instability,
+live destination previews, and optional mod integrations are not ported. The
+book panel is a placeholder, not a rendered destination view. The
+[port status](MINECRAFT_26_3_PORT.md) and [open port issues](https://git.paddedcell.org/dnorberg/rivencraft/issues)
+track the remaining work. The stable 1.21.1 release remains available
+separately.
+
+## Verification
+
+- Clean 26.3 Gradle build passed.
+- Disposable dedicated-server smoke test passed: two distinct Age seeds and
+  their terrain persisted across restart.
+- The player verified Descriptive Book binding and travel in game on
+  2026-10-29.
+
+These checks are **not** the full port acceptance matrix or a stability claim.

docs/PUBLISHING_APIS.md

@@ -0,0 +1,82 @@
+# Publishing Rivencraft with the Gitea, Modrinth, and CurseForge APIs
+
+The local helper is [`scripts/publish_mod_sites.py`](../scripts/publish_mod_sites.py).
+It previews a release unless `--publish` is explicitly supplied. The current
+configuration is for the Minecraft **26.3** artifact only. The 1.21.1 line needs
+its required external dependencies mapped on both sites before API publishing
+is enabled for it.
+
+## One-time token setup
+
+For Gitea, an existing personal access token is sufficient if it has
+`write:repository` scope. That scope covers release creation and attachment
+upload; do not grant `all` if a narrower token is available. Create or inspect
+tokens under [Gitea user settings → Applications](https://git.paddedcell.org/user/settings/applications).
+The helper checks token identity and scope without displaying the secret.
+
+Create a [Modrinth personal access token](https://docs.modrinth.com/api/#authentication)
+in account settings with `VERSION_CREATE` (upload) and `USER_READ` (read-only
+credential check) scopes. Create a
+[CurseForge Upload API token](https://support.curseforge.com/support/solutions/articles/9000197321)
+from the author's API Tokens page. Treat both as passwords: never put them in
+git, chat, a release note, or a command-line argument.
+
+In a terminal at the repository root, run these one at a time and paste the
+corresponding token into the hidden prompt:
+
+```sh
+python3 scripts/publish_mod_sites.py store-token modrinth
+python3 scripts/publish_mod_sites.py store-token curseforge
+python3 scripts/publish_mod_sites.py store-token gitea
+```
+
+The tokens are stored in the desktop Secret Service keyring under
+`application=rivencraft-publishing`, separately by site. The script also accepts
+`RIVENCRAFT_MODRINTH_TOKEN` or `RIVENCRAFT_CURSEFORGE_TOKEN` environment variables,
+but these take precedence over keyring entries and should not be put in shell
+history or startup files.
+
+Verify the credentials without uploading anything:
+
+```sh
+python3 scripts/publish_mod_sites.py check-token modrinth
+python3 scripts/publish_mod_sites.py check-token curseforge
+python3 scripts/publish_mod_sites.py check-token gitea
+```
+
+## Release workflow
+
+Build the JAR, write a Markdown changelog, and preview the metadata:
+
+```sh
+python3 scripts/publish_mod_sites.py release \
+  --jar ports/mc263/build/libs/rivencraft-26.3-1.0.1.32-beta.1.jar \
+  --changelog ports/mc263/RELEASE_NOTES_1.0.1.32-beta.1.md \
+  --version 1.0.1.32-beta.1 \
+  --name 'Rivencraft 1.0.1.32-beta.1 — NeoForge 26.3' \
+  --minecraft 26.3 --java 25 --channel beta
+```
+
+For a *new* version only, append `--publish` to upload to both sites. Use
+`--site modrinth` or `--site curseforge` to target one site. Modrinth rejects an
+existing version number; CurseForge may not, so check its file list before any
+retry after a partial failure. CurseForge approval may take additional time.
+
+The default destination is now all three sites. The Gitea release step requires
+the annotated version tag to have been pushed first. Gitea's `Vx.y.z.b-mc26.3-beta.1`
+tag convention is derived from the version and channel; an existing release
+with different title or notes is never overwritten. If release creation
+succeeds but its JAR upload fails, rerun with `--site gitea --publish` to resume
+only the missing attachment. `--site both` retains the earlier Modrinth and
+CurseForge-only behavior.
+
+The helper uses Gitea's documented
+[`POST /repos/{owner}/{repo}/releases`](https://docs.gitea.com/api/operations/repo-create-release/)
+and [release attachment endpoint](https://docs.gitea.com/api/operations/repo-create-release-attachment/),
+plus Modrinth's documented multipart
+[`POST /version`](https://docs.modrinth.com/api/operations/createversion/) and
+CurseForge's documented
+[`POST /api/projects/{projectId}/upload-file`](https://support.curseforge.com/support/solutions/articles/9000197321)
+with the JAR, changelog, version channel, NeoForge, Minecraft version, Java
+version, and client/server environment. It sets no external dependencies for
+26.3, which uses Rivencraft's first-party Age backend.

gradle.properties

@@ -36,7 +36,7 @@ mod_name=Rivencraft
 # The license of the mod. Review your options at https://choosealicense.com/. All Rights Reserved is the default.
 mod_license=LGPL-3.0-or-later
 # The mod version. Rivencraft uses the x.y.z.b policy documented in README.md.
-mod_version=1.0.0.2
+mod_version=1.0.1.1
 immersive_portals_version=6.0.7
 terrablender_version=4.1.0.8
 serene_seasons_version_id=pHEgQQUE

ports/mc263/README.md

@@ -0,0 +1,721 @@
+# Minecraft 26.3 beta port workspace
+
+This is an **experimental beta port** for issues #97–#104, not gameplay parity
+with the Minecraft 1.21.1 release. The 26.3 backend persists separate Ages and
+their seeds. Books, the Book Binder, and the Ink Mixer work, and the Binder can
+author Standard, Amplified, Island, Flat, Void, or Cave terrain with supported
+biome-distribution pages, selected material/vegetation/structure features, and
+independent Age weather and lighting. Celestial systems, instability, crystal
+portals, and much of the 1.21.1 gameplay remain unported. 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.
+
+The entries below record how the port was built, including earlier alpha-only
+limitations that were addressed by later slices.
+
+The creative tab contains the two Books, Crystal Block and Crystal Shard;
+the player verified these in game. Unbound Linking Books use the Legacy
+sprite, and four Crystal Shards craft into a Crystal Block; both were also
+verified in game. The current local iteration adds Budding Crystal and all
+four blue crystal growth stages with vanilla-style harvesting. Natural crystal
+formation generation is not yet ported; use Creative or commands to obtain a
+Budding Crystal for this test. The player verified the growth chain in game.
+The next local slice adds the Link Panel Page as a separate creative entry,
+using the existing item texture. Blank Pages remain unavailable in Creative;
+the player verified the Link Panel's appearance in game. Ink Vials now use
+the existing crafting recipe and animated sprite. With paper in the other
+hand, an Ink Vial prepares a Link Panel for two of its sixteen ink uses, as
+in the current 1.21.1 default. The player verified the Ink Vial interaction
+in game. Symbol writing remains unported.
+A prepared Link Panel can now be combined shapelessly with leather to craft
+an unwritten Linking Book, as in 1.21.1. This custom recipe rejects a blank
+Page and extra ingredients. The first Book Binder slice now assembles random-Age
+Descriptive Books from leather and a Link Panel. Authored pages remain later.
+
+The next local `1.0.1.10-alpha.1` slice exposes all eight combinations of
+plain, Disarm, Maintain Momentum, and Intra-Linking Link Panels in the Link
+Pages creative tab. Leather crafting preserves those flags on the Linking
+Book. Intra-Linking permits same-dimension travel; Maintain Momentum rotates
+horizontal speed to the destination yaw; Disarm leaves the player's inventory
+at the departure point after a successful teleport. These are development
+variants until the Ink Mixer is ported; other Link Panel modifiers are not
+implemented in 26.3. The player passed this modifier slice in game.
+
+The local `1.0.1.11-alpha.1` slice adds a craftable Book Binder with persistent
+leather, Link Panel, and output slots. Name an Age in its GUI and press Bind;
+the server creates a random prototype Age and places its completed Descriptive
+Book in the output. Disarm and Maintain Momentum carry from the panel into the
+book; Intra-Linking has no effect on Age creation. Symbol-page authoring and
+the Ink Mixer remain unported. This slice passes the build and dedicated-server
+smoke test. The player passed crafting and travel in game, but found that E
+closed the focused title field and the provisional layout did not match the
+existing 1.21.1 Binder GUI.
+
+The local `1.0.1.12-alpha.1` follow-up reuses the 1.21.1 Binder layout: title
+bar, cover and output at opposite sides, and a central Link Panel page strip.
+The title persists in the block, the missing-panel cue pulses red, and a
+focused title field consumes inventory/hotbar keys. Click the output once to
+bind, then click again to take the completed book. Authored symbol strips and
+the full 1.21.1 Binder grammar remain unported. This same slice also ports the
+1.21.1 Ink Mixer block, menu, animation, modifier additives, 16-ink-per-panel
+cost, and automatic vial exchange. The creative tab includes it and its
+vanilla-shaped recipe is available. This slice needs an in-game Binder visual/
+keyboard check and Ink Mixer interaction check.
+
+The local `1.0.1.13-alpha.1` iteration makes Binder assembly place the new
+Descriptive Book directly on the cursor with one click. It also renders the
+five-page strip from the 1.21.1 GUI and refreshes the Mixer's virtual result
+in the same server click that changes paper or ink. The Mixer now consumes
+one ink unit and one paper per Link Panel (16 panels per full vial); additive
+chances reset when a panel is taken. In-game retest of the first-update
+behavior and Binder visual/click flow is pending.
+
+The local `1.0.1.14-alpha.1` follow-up compares the current 26.3 Binder against
+the new dev-image sequence. The Binder no longer paints five permanently empty
+pages: the first strip page appears when a Link Panel is inserted or carried,
+and the missing-panel cue remains above it. Clicking that page inserts/removes
+the Link Panel using the same server-owned cursor flow as 1.21.1. Its tooltip
+also shows the stored panel. Multi-page symbol writing and strip scrolling
+cannot be exercised yet because symbol pages are still unported to 26.3.
+
+The local `1.0.1.15-alpha.1` Binder polish uses the Link Panel's actual 16×16
+item icon for the missing-panel cue instead of a full-size page sprite. The
+red pulse and tooltip remain confined to that icon.
+
+The local `1.0.1.16-alpha.1` slice adds the bundled 1.21.1 symbol-page
+identities to the 26.3 creative menu, grouped by category. Their names and
+descriptions are reused from the 1.21.1 translations, and the Page item now
+persists each symbol ID. These pages currently use the generic symbol-page
+artwork; the Legacy-style runtime glyph compositor has not been ported.
+They cannot yet be inserted into the Binder or change Age generation. This is
+the page-data foundation for the next authored-writing slice.
+
+The local `1.0.1.17-alpha.1` follow-up derives biome pages from the active
+26.3 biome registry instead of only the older bundled list. It excludes the
+TerraBlender staging placeholder and separates cave/Nether biomes. Full-block
+materials and true source-fluid blocks also receive registry-derived pages,
+covering eligible new and modded blocks. Five 26.3 feature symbols cover
+poplar trees, fallen poplars, shelf mushrooms, red shrubs, and abandoned
+camps. These feature pages are identities only until their Age-generation
+handlers are ported. Biome, material, and feature pages still use generic
+artwork and cannot yet be placed in the Binder.
+
+The local `1.0.1.18-alpha.1` follow-up restores the 1.21.1 animated redaction
+for Corrupted Page names and descriptions. It does not yet port the dynamic
+glyph artwork used for other symbol pages.
+
+The local `1.0.1.19-alpha.1` slice ports the runtime glyph compositor for
+symbol Page items. It uses the shared Legacy component sheet and page
+parchment with a bounded 256-texture client cache; generated textures are
+released on resource reload. Registry-derived biome and material pages use
+the same deterministic four-word poem pattern as 1.21.1. No per-symbol PNGs
+are generated in the source tree. Binder insertion and authored Age generation
+are still unported.
+
+The local `1.0.1.20-alpha.1` visual follow-up enlarges symbol artwork on Page
+items, slightly thickens the component strokes, and centers number glyphs at a
+larger size so they remain readable in inventory and creative-menu icons.
+
+The local `1.0.1.21-alpha.1` slice ports the Binder's ordered, scrollable
+symbol-page strip. Pages persist in its block inventory and can be inserted,
+removed, and moved via the cursor or shift-click. A Binder with symbol pages
+cannot yet produce a book: authored Age compilation is the next port step, and
+silently producing a random Age would consume the player's writing incorrectly.
+
+The local `1.0.1.22-alpha.1` visual follow-up gives large Binder pages the
+transparent, full-size Legacy glyph composition. Item icons retain their
+separate parchment-backed, reduced-size artwork.
+
+The local `1.0.1.23-alpha.1` follow-up places Binder glyph overlays in a later
+26.3 GUI stratum than the page atlas, preventing texture batching from drawing
+the opaque page backgrounds over the dynamic artwork.
+
+The local `1.0.1.24-alpha.1` follow-up renders Binder page glyphs through
+their working special item model, scaled to the page thumbnail. Direct GUI
+blitting of the generated texture remained blank in the 26.3 client.
+
+The local `1.0.1.25-alpha.1` follow-up marks temporary Binder preview stacks
+for glyph-only special-model rendering. The full-size transparent artwork now
+uses the working item pipeline without drawing a second, smaller page outline.
+
+The local `1.0.1.26-alpha.1` corrects the temporary preview component's codec
+registration, which NeoForge 26.3 requires during bootstrap.
+
+The local `1.0.1.27-alpha.1` slice applies the first authored Age subset:
+Standard terrain plus at most one Biome page. The selected biome is persisted
+with the Age and used by a fixed-biome Overworld noise generator on creation
+and reload. Ordered page IDs are stored on the finished book. Other page
+combinations remain in the Binder and cannot yet be assembled, preventing
+silent loss of unsupported writing. Multi-biome distribution, other terrain
+profiles, and feature/material pages still need their 26.3 generation ports.
+
+The `1.0.1.28`–`1.0.1.32` slices add Tiled, Grid, Native, and five scaled
+biome distributions; multiple authored Biome pages; Amplified and Island
+terrain; and saved terrain/biome plans across reload. A Binder or Ink Mixer
+beside another block no longer hides that block's faces. Unsupported authoring
+still stays in the Binder rather than silently producing an incorrect Age.
+
+The local `1.0.1.33-beta.1` slice adds Flat and Void terrain to Binder
+authoring. Flat uses vanilla's superflat layers; Void has no generated floor
+and uses the selected Biome for its environmental rules. Each accepts zero or
+one authored Biome page. Unsupported multi-biome Flat/Void books remain in the
+Binder until their custom generator is ported. The operator probe can create
+test Ages with `rivencraft_port age create <name> <seed> flat|void`.
+
+The local `1.0.1.34-beta.1` follow-up starts Flat's solid layers at Y=0
+(bedrock at 0, dirt at 1–2, grass at 3) and lands players at the ground surface
+instead of creating an elevated fallback platform. This affects newly
+generated Flat chunks; previously generated Age chunks are not rewritten.
+
+The local `1.0.1.35-beta.1` follow-up enables biome decoration on newly
+generated Flat chunks, allowing the selected biome's trees, vegetation, and
+other placed features to appear on the Flat surface. Void remains undecorated.
+
+The local `1.0.1.36-beta.1` slice accepts multiple Biome pages with Flat and
+Void terrain. It ports the 1.21.1 authored-biome Flat generator to 26.3, so
+Tiled, Grid, and scaled regions affect climate in both terrain types and
+surface decoration in Flat. Void continues to generate no floor or biome
+decoration. The operator-only `age create_multi` probe creates two-biome test
+Ages for the dedicated-server smoke test.
+
+The local `1.0.1.37-beta.1` slice adds the Cave terrain page to Binder
+authoring. It uses Minecraft's caves noise settings, accepts Cave and Nether
+biome pages (including multi-biome distribution), and searches below Y=64 for
+a safe arrival instead of landing on the roof. The 26.3 vanilla Cave preset
+defaults to water below Y=32, so this port derives a dry Cave setting with
+air as its default fluid and the sea level below the world floor. This applies
+to newly generated Cave chunks; it does not drain existing chunks. Cave-specific Nether surface
+materials from 1.21.1 are not ported yet. The dedicated-server smoke now
+creates and reloads Cave Ages alongside the other terrain families.
+
+The dry-Cave follow-up is packaged as `1.0.1.38-beta.1`; no 26.3 release is
+published until the in-game check passes and publication is explicitly requested.
+
+The local `1.0.1.39-beta.1` follow-up rejects fluid at both feet and head
+height during safe-landing searches. It also refuses to carve the fallback
+platform into submerged space if no dry footing can be found.
+
+The `1.0.1.40-beta.1` port slice seeds terrain and biome selection for
+Descriptive Books with no authored symbol pages. It uses the same terrain and
+biome-controller rank weights as the 1.21.1 line, freezes the resulting plan
+in the Age index, and accepts the result after restart. The operator-only
+`age create_random <name> <seed>` probe exercises this path. Random feature,
+sky, weather, and instability choices are not yet ported; this slice covers
+terrain and biomes only.
+
+The `1.0.1.41-beta.1` slice establishes an Age-scoped decoration wrapper
+for 26.3 and accepts one Block material page immediately before a Rocks feature
+page. Newly generated surface chunks place small rock clusters made from that
+block without modifying the shared biome registry. The selected block and
+generator survive a restart. Cave and Void terrain remain unsupported for this
+first surface-feature path; unsupported combinations stay in the Binder.
+Random feature selection, unpaired materials, duplicate feature pages, and
+instability scoring remain future port steps.
+
+The local `1.0.1.42-beta.1` follow-up lets a Rocks page choose a deterministic
+full-block material when no Block page precedes it. Repeated Rocks pages now
+add independent placement attempts (up to 32) instead of being rejected. The
+ordered material choices are frozen in the Age index and restored after a
+restart; old single-material beta Ages still load. An explicit Block page
+must still directly precede the Rocks page it modifies. Most other feature
+pages and material-feature pairings remain unported.
+
+The local `1.0.1.43-beta.1` slice replaces the temporary 3×3 Rocks piles
+with Minecraft 26.3's forest-rock block-blob feature and its placement rules,
+matching the 1.21.1 Age feature path more closely. The selected material and
+repeat count still come from the frozen Age plan. Only newly generated chunks
+use the new rock shape; previously generated chunks remain unchanged.
+
+The local `1.0.1.44-beta.1` slice ports ordered Flowers, Trees, and Huge
+Trees pages to surface Ages. Their 26.3 vanilla placed features run after
+biome decoration, with the Age's own seed; repeated pages make independent
+placement attempts. Cave/Void terrain and cave/Nether/End biome pools are
+not treated as surface vegetation. The feature plan survives server restart;
+already generated chunks do not gain new decoration.
+
+The local `1.0.1.45-beta.1` slice ports the Dungeons page for Standard,
+Amplified, and Island noise terrain. It uses the 1.21.1 placement definition
+(eight monster-room attempts per page per chunk across the build height),
+stores repeat count with the Age, and rejects Dungeons pages on Flat, Void,
+or Cave terrain. New chunks only; existing chunks are not regenerated.
+
+The local `1.0.1.46-beta.1` slice adds Surface Lakes, Deep Lakes, and Small
+Lakes on surface noise terrain. A Fluid page immediately before a lake page
+selects its fluid. Unmodified pages choose a seeded fluid from the same source-
+fluid pool exposed in Creative, with repeated choices and their order saved
+with the Age. Surface/Small Lakes retain the 1.21.1 one-in-twelve attempt rule;
+Deep Lakes retain vanilla underground placement. These pages currently require
+Standard, Amplified, or Island terrain. Existing chunks do not redecorate.
+
+The local `1.0.1.47-beta.1` slice adds authored Floating Islands alongside
+Standard, Amplified, Island, Flat, and Void terrain. A preceding Block page
+sets the island core material; otherwise each occurrence resolves a seeded
+material from the full-block pool. The 1.21.1 shape, high altitude, rarity,
+and biome-dependent grass/dirt cap are retained. Repeated pages use independent
+island seeds. Cave terrain remains unsupported for this feature.
+
+26.3 combines base noise, surface, and cave carving in one terrain operation.
+Floating Islands run after that operation and before decoration, so the added
+islands are not cut by the base terrain's carvers. The saved feature plan is
+used again after restart and for new chunks; existing chunks keep their blocks.
+
+The local `1.0.1.48-beta.1` slice adds authored Tendrils on every terrain
+type, including Cave and Void. A preceding Block page selects the material;
+unmodified occurrences resolve seeded materials from the full-block pool.
+Repeated pages use independent paths, with up to 32 occurrences per feature.
+Mixed Floating Islands/Tendrils retain their authored order in the saved plan.
+
+Tendrils retain the 1.21.1 branching path algorithm, source rates, and vertical
+distribution concentrated below Y=128. They can replace existing terrain while
+preserving bedrock. As with Floating Islands, they run after 26.3's combined
+terrain operation and before decoration. Build checks are automated; in-game
+generation, appearance, and restart validation are handed to the player.
+
+The local `1.0.1.49-beta.1` slice adds the Skylands feature page. Its seeded
+seven-octave filter removes base terrain at/below a varying cutoff near Y=76
+and removes liquid above it, preserving the upper solid terrain. It accepts
+all terrain types and no Block modifier. On low Flat terrain this removes
+the base layers; on Void it leaves the empty base unchanged.
+
+The filter runs once before authored Floating Islands and Tendrils, matching
+1.21.1; duplicate Skylands pages do not compound the filter. Its flag is saved
+with the terrain-feature plan. Existing chunks are unchanged. Try Amplified
+terrain for a clear visual check; generation and restart validation are manual.
+
+The local `1.0.1.50-beta.1` slice ports Spheres and Spikes using the 1.21.1
+generation algorithms. Spheres add solid nodes on all terrain types, including
+Cave and Void, while preserving bedrock. Spikes require solid surface terrain:
+Standard, Amplified, Island, or Flat. Their circular footprint stays in one
+chunk and must have solid ground beneath every column.
+
+Each page accepts a preceding Block material or resolves a seeded random
+material when unmodified. Repeated pages have independent placement seeds,
+up to 32 per feature. Spheres run during terrain construction, after Skylands;
+Spikes run after biome decoration. Both use the existing saved solid-feature
+plan. New chunks only; in-game appearance and restart checks remain manual.
+
+The local `1.0.1.51-beta.1` slice ports Obelisks. It preserves the 1.21.1
+one-in-128 candidate chance per chunk/occurrence, 4×4 plinth, and 2×2 shaft
+extending 12 blocks above it. Placement requires dry, sturdy ground across
+the base, at most two blocks of surface variation, and clear/replaceable
+space for the complete structure. The footprint stays within its chunk.
+
+Obelisks support Standard, Amplified, Island, and Flat terrain. A preceding
+Block page sets their material; otherwise a seeded full-block material is
+selected. Repeated pages make independent attempts, up to 32 occurrences.
+Spikes and Obelisks share surface-stage classification and preserve their
+authored order within that stage. World and restart validation are manual.
+
+The local `1.0.1.52-beta.1` slice ports Crystal Formations using the 1.21.1
+surface-mound algorithm and the existing blue crystal blocks. Each occurrence
+has a one-in-fifteen candidate chance per chunk; suitable dry, nearly level
+ground produces a 3×3 mound with budding crystal and occasional small buds.
+The existing budding blocks continue growing crystals through random ticks.
+
+Crystal Formations accepts Standard, Amplified, Island, and Flat terrain,
+but not Cave/Void terrain or Block/Fluid modifiers. Up to 32 repeated pages
+make independent attempts. The ordered feature plan survives restart, and
+only newly generated chunks receive formations. For a quick manual test,
+bind a Flat/Plains Age with several Crystal Formations pages, inspect the
+blue mounds and bud growth, then revisit after restarting the world.
+
+The local `1.0.1.53-beta.1` slice ports Dense Ores. Each page replays eligible
+ore placements from the Age's actual biomes, preserving their height ranges,
+replacement rules, and biome filters. Vanilla and modded ore features are
+recognized by their ore targets; custom placements can opt in through the
+`rivencraft:dense_ores` placed-feature tag, just as in 1.21.1.
+
+Up to 32 pages add independent passes on Standard, Amplified, Island, or Cave
+terrain. Flat/Void and Block/Fluid modifiers are unsupported; an explicitly
+authored biome pool must contain at least one ore-producing biome. The count
+survives restart. Only new chunks gain extra ore, and this slice does not yet
+port the later instability system or random-Age feature selection.
+
+For manual validation, create a Standard/Plains Age with several Dense Ores
+pages and inspect underground ore abundance, then restart and explore more
+chunks. A Cave Age with a Nether biome can check Nether ore placements too.
+
+The local `1.0.1.54-beta.1` slice ports the Star Fissures page. On first book/
+operator arrival, it carves the 1.21.1 Legacy-shaped rift near the arrival chunk
+and places a starfield portal at the dimension's minimum Y. Cave terrain keeps
+its bedrock roof. All terrain types are supported; repeated pages still create
+one fissure, and Block/Fluid modifiers are not accepted.
+
+The first arrival and completed generation are saved per Age, so revisits and
+restarts do not recarve the rift. Touching its bottom returns entities to a safe
+location near the shared Overworld spawn, not a bed, with the original fissure
+sound. The portal is unobtainable and inert in the Overworld. Random-Age feature
+selection remains later work; author a Star Fissures page to test this slice.
+
+For manual validation, create a Flat/Plains Age with Star Fissures. Look near
+the arrival point (generally east/south), descend through the rift, and touch
+the starfield to return. Re-enter after restarting; check that the same fissure
+and its portal still work. A Cave Age checks that carving leaves the roof intact.
+
+The local `1.0.1.55-beta.1` slice adds authored Villages, Mineshafts, and
+Strongholds. Repeated pages (up to 32 per type) scale the registered placement
+using the 1.21.1 frequency/spacing and ring-count rules. Copies are Age-local:
+the Overworld's placements and biome source are not modified. Authored
+structures can bypass their usual biome eligibility without changing the
+terrain biome; their instability cost remains pending with the instability port.
+
+Villages and Strongholds allow surface noise terrain and Flat, but not Cave
+or Void. Mineshafts allow noise terrain including Cave, but not Flat or Void.
+These pages do not accept Block/Fluid modifiers. Their ordered counts persist
+in the feature plan. In books using these structure pages, unselected sets
+from these three families are disabled; other structure families and random
+feature selection remain later port work. Earlier books without this new
+structure plan retain their existing native structure behavior.
+
+For manual checks, bind a new Standard/Plains Age with Villages, Mineshafts,
+and Strongholds, then use `/locate structure minecraft:village_plains`,
+`/locate structure minecraft:mineshaft`, and
+`/locate structure minecraft:stronghold` to inspect generated structures.
+Compare one page with several copies in a different Age, and restart/revisit.
+Flat/Plains with Villages and an otherwise incompatible surface biome with
+Villages provide separate terrain and biome-override checks.
+
+The local `1.0.1.56-beta.1` follow-up fixes authored structures outside their
+normal biomes. Build 55 only bypassed the final biome check; 26.3's jigsaw
+placement can reject a whole biome column earlier. The override now supplies
+the generation context's biome predicate before either check, only for the
+explicitly authored structures in that Age. Terrain/height/geometry rules and
+unrelated structures keep their normal checks.
+
+Test with a new Standard or Flat Age using a normally unsupported village
+biome, such as The End, plus a Villages page. Multiple copies increase density.
+Use `/locate structure #minecraft:village` rather than selecting only the
+Plains variant: an override Age can choose other village styles. Old chunks
+that already rejected their structure attempt are not regenerated; existing
+build-55 Ages can also test the fix in previously unexplored chunks.
+
+The local `1.0.1.57-beta.1` slice adds the remaining 1.21.1 authored structure
+families: Nether Fortresses, Bastions, Trial Chambers, Buried Treasure,
+Shipwrecks, Ocean Ruins, Pillager Outposts, Ruined Portals, Nether Fossils,
+Ancient Cities, and Trail Ruins. It also enables the existing 26.3-only
+Abandoned Camps page using Minecraft's registered camp set and variants.
+
+All 15 supported structure-set pages share saved counts, biome overrides,
+and repeated-page density scaling (up to 32 per type). Fortress and Bastion
+sets reuse the separate 1.21.1 placement definitions; the combined vanilla
+Nether set is disabled for authored structure plans so the pages stay separate.
+Unselected supported families are gated in these plans. Already generated
+chunks and Ages without an authored structure plan keep their existing path.
+
+Only Villages/Strongholds support Flat; none support Void. Fortress, Bastion,
+and Nether Fossils require Cave terrain. Villages/Strongholds, Buried Treasure,
+Shipwrecks, Ocean Ruins, Outposts, Trail Ruins, and Abandoned Camps require
+surface terrain. Mineshafts, Trial Chambers, Ancient Cities, and Ruined Portals
+allow surface noise or Cave terrain. Physical terrain/height checks still apply
+even when the authored page overrides biome eligibility. Instability penalties
+and random selection of these features are not part of this slice.
+
+For a quick in-game check, author a new Standard Age with Trial Chambers,
+Trail Ruins, and Abandoned Camps. Use `/locate structure minecraft:trial_chambers`,
+`/locate structure minecraft:trail_ruins`, and
+`/locate structure minecraft:abandoned_camp_forest` to inspect actual generation.
+Separately, test a Cave/Nether Wastes Age with Fortress and Bastion pages
+(`/locate structure minecraft:fortress` and
+`/locate structure minecraft:bastion_remnant`). Repeated pages and restart/
+new-chunk generation remain useful checks. Structures can still fail when
+their geometry or required terrain is unavailable.
+
+The local `1.0.1.58-beta.1` slice enables Caves and Ravines feature pages.
+They add carving to the chosen noise terrain (Standard, Amplified, Island,
+or Cave); they are not aliases for the Cave terrain page. Flat/Void and
+Block/Fluid modifiers remain unsupported, matching the 1.21.1 feature rules.
+
+Authored paths retain 1.21.1's source range and seeded salts, using 26.3's
+registered cave/Nether-cave/canyon carvers. Nether-biome sources select the
+Nether cave carver and skip Ravines. The paths merge into the native carving
+mask before Minecraft applies aquifer, replacement, and surface rules; no
+second approximation carves raw air after terrain generation. Biomes are not
+replaced. The page list is saved, and old plans default to no extra carving.
+
+Duplicate pages are accepted up to 32 per type, but repeat the same seeded
+pattern in 1.21.1; this port skips those redundant passes rather than multiplying
+carving density. Random feature selection and instability remain pending.
+New chunks only. For manual testing, author a Standard/Plains Age with one
+Caves page and one Ravines page and inspect underground in Spectator mode.
+Restart and explore more chunks. A separate Cave/Nether Wastes Age with Caves
+checks the Nether variant without altering its biome distribution.
+
+The local `1.0.1.59-beta.1` slice audits page presentation for the current port.
+Each Symbol Page now reports whether its effect is implemented. Unported pages
+have red-tinted item artwork and a red Binder page background, plus a red status
+line. Supported pages retain their normal artwork. This indicates port
+availability only: supported pages in an invalid order, terrain combination,
+or excessive quantity are not individually tinted red. Link Panels are unchanged.
+
+The stale Standard/one-Biome message is removed. Structure descriptions now
+describe authored biome overrides rather than falsely requiring vanilla biome
+eligibility. Material pages explain the immediate-before-feature requirement;
+Flat/Caves/Ravines/Floating Islands descriptions reflect the current rules.
+These overrides are specific to the 26.3 language file and do not change 1.21.1.
+No new generation effect is introduced in this UI slice.
+
+For manual validation, compare a working Villages or Caves page with an
+unported celestial or lighting page in Creative inventory
+and the Binder. Only the latter should be red; supported Block/Fluid modifiers
+and biome controllers should stay normal even though they need other pages.
+
+The local `1.0.1.60-beta.1` slice implements Poplar Trees, Fallen Poplar Trees,
+Red Shrubs, and Shelf Mushrooms. They use the existing saved vegetation plan,
+ordered attempts, surface-biome rules, and combined 32-vegetation-page limit.
+They accept Standard, Amplified, Island, and Flat terrain, but not Cave/Void
+or Block/Fluid modifiers. The four pages now show as supported, without a red tint.
+
+Poplar Trees uses the vanilla red/orange/yellow leaf-litter tree variants with
+their relative Dappled Forest weights and six attempts per page per chunk;
+it does not also select spruce or fallen trees. Fallen Poplar Trees makes one
+surface attempt per page, using the vanilla fallen-tree feature, decorators,
+and sapling survival rules. Red Shrubs uses the vanilla patch placement.
+All still require suitable ground and space; authoring does not bypass those
+requirements, and existing chunks are not redecorated.
+
+Shelf Mushrooms applies Minecraft's standing/fallen-log decorator to existing
+log groups, not a new tree feature. It can decorate natural trees or logs from
+earlier authored tree pages; no suitable logs means no mushrooms. The vanilla
+side/age/spacing and water-avoidance logic is retained. Writes stay within the
+current chunk and require valid support. Consecutive mushroom pages reuse the
+host scan; adding trees invalidates the cached host list for subsequent pages.
+
+For manual testing, bind a new Flat/Plains Age with Poplar Trees, Fallen Poplar
+Trees, Red Shrubs, then Shelf Mushrooms. Check leaf colours, fallen trunks,
+shrubs, and mushrooms on logs. The four pages should no longer be red. Restart,
+revisit existing terrain, and explore new chunks to check persistence.
+
+The local `1.0.1.61-beta.1` follow-up removes the inappropriate surface-terrain
+and surface-biome gates from Shelf Mushrooms only. No tree page is required:
+natural logs or generated log Tendrils/Spheres/other features are hosts on
+any terrain, including Void and Cave, and in any biome. Other plants keep their
+existing terrain/biome restrictions. For example, Void + Oak Log + Tendrils +
+Shelf Mushrooms is valid authoring; there must still be exposed log faces.
+
+The mushroom scan now considers log faces throughout the chunk height instead
+of treating a connected tendril as a standing tree with a small base-height
+decoration band. Placement retains native replaceability/water checks, valid
+support, random age, a per-side chance, and spacing checks. It does not grow
+hosts or continuously decorate player-built logs after chunk generation.
+Test a new Void Age with the example pages and inspect tendril surfaces.
+
+The local `1.0.1.62-beta.1` sound slice reuses the complete 1.21.1 sound manifest
+and all six OGG files directly in the build. Successful Linking/Descriptive Book
+travel now plays the normal, Intra-Linking, or Disarm sound at departure and
+arrival, with the same modifier precedence and cloud bursts as 1.21.1. Failed
+travel stays silent. Star Fissures also play their return sound after arrival,
+instead of relying only on audio sent immediately before a dimension switch.
+Portal and meteor sound events are bundled for their later gameplay ports;
+this does not implement those systems. Binding still uses vanilla page audio.
+Manual checks: normal book travel, Intra-Linking, Disarm, rejected travel, and
+a Star Fissure return. Existing books/Ages do not need to be recreated.
+
+The local `1.0.1.63-beta.1` slice ports the six active weather pages: Normal,
+Fast, Slow, Off, Always, and Storm. One weather page is accepted per book and
+its policy is saved in the Age's own data directory. Missing weather pages
+currently use Normal; random weather selection is still part of the pending
+random-trait port. Cave terrain forces Off, matching 1.21.1. Precipitation
+still follows biome temperature and precipitation rules; a desert does not
+start showing rain merely because Always or Storm is selected.
+
+26.3 normally shares server WeatherData. Runtime Ages now use an isolated
+native WeatherData instance with its own persisted rain/thunder timers. The
+weather controller runs before the native cycle, allowing vanilla rendering,
+lightning, snow and client dimension-specific packets to handle the result.
+Fixed weather is refreshed before its timers expire; Fast and Slow use the
+1.21.1 duration ranges and preserve saved timers on reload. Overworld weather
+and other Ages are not changed. The vanilla `/weather` command still targets
+the server's global weather, not the independent Age policy.
+
+Operator diagnostics: `/rivencraft_port age create_weather <name> <seed> <mode>`
+creates a Flat test Age; `/rivencraft_port age weather_probe <name>` reports
+its policy, rain/thunder state and timers, data independence, and global state.
+For manual testing, bind separate Storm/Always/Off books with Plains, compare
+the Overworld, revisit and restart, and check that Cave + Storm remains dry.
+The six weather pages should no longer be tinted red. Existing Ages get a
+Normal independent cycle; author a new book to select another policy.
+
+The local `1.0.1.64-beta.1` fix corrects the Binder's biome compiler: it now
+positively selects biome-category pages instead of treating every page not
+in an exclusion list as a biome. Weather pages no longer trigger an unknown
+biome lookup. The weather fixture command now exercises the same page compiler
+before creating an Age, covering the weather-only symbol list used by a Link
+Panel + Storm book. Existing Binder contents can be reused after updating.
+
+The local `1.0.1.65-beta.1` spawn correction removes the Flat-layer shortcut
+and heightmap-only choice for non-Cave Descriptive Book arrivals. The search
+starts at the actual maximum build height and traces each nearby column down
+to its first colliding block, leaves, or fluid. A column without safe dry
+footing/headroom is skipped instead of descending through its roof or water
+into an underground pocket. Leaves are valid footing; fluids are not.
+
+This also revalidates a stored Star Fissure arrival from above on non-Cave
+terrain. Cave terrain retains its Y=64-downward search, and bound Linking
+Books retain their exact coordinates. If no natural surface is safe, the
+safety platform is placed above the actual highest obstruction (or floor
+Y=63 in an empty Void), never buried below it. Plain Flat terrain still lands
+on its ground, not an artificially elevated platform. No new Age is required.
+Operator-only `/rivencraft_port age surface_probe <name> <x> <z>` reports the
+actual highest obstruction and a safe nearby surface without creating a
+platform or teleporting. It can generate chunks while inspecting the region.
+
+The local `1.0.1.66-beta.1` slice ports Normal, Dark, and Bright Lighting.
+One lighting page is accepted per book and its choice is saved in the Age
+index before catalog publication. Missing lighting currently defaults to
+Normal; random lighting selection and Bright's instability cost await those
+systems' later ports. Lighting pages should no longer be tinted red.
+
+Normal surface Ages retain the Overworld type. Dark removes skylight with
+ambient light 0.0; Bright uses ambient light 0.25 and retains surface skylight,
+matching 1.21.1. **Cave + Bright is supported:** it has ambient light 0.25
+without skylight. Cave Normal/Dark use no skylight and ambient light 0.0.
+Placed light sources continue working; ambient light is not a placed light
+level or a guarantee that monsters cannot spawn.
+
+The build derives three registered dimension-type variants from the current
+vanilla Overworld JSON, changing only has_skylight and ambient_light. This
+preserves native attributes/timelines and synchronizes types through the
+normal login registry exchange; no dynamic client registry mutation is used.
+These variants currently use the vanilla type, not custom runtime changes to
+the host Overworld dimension type made by another data pack.
+Saved lighting survives reload, reseed, restart and retirement rollback.
+Existing non-Cave Ages without a choice remain Normal; old Cave Ages now use
+the no-skylight baseline. Use new Ages for clear visual comparisons and avoid
+confusing previously lit chunks with the current dimension settings.
+
+Manual check: create Normal/Dark/Bright surface books and Cave + Bright;
+compare an unlit enclosed room, check placed torches, revisit/restart and
+confirm the Overworld stays unchanged. Operator diagnostics:
+`/rivencraft_port age create_lighting <name> <seed> <mode> <terrain>` and
+`/rivencraft_port age lighting_probe <name>` report the registered type,
+skylight and ambient light. Test JAR: `1.0.1.66-beta.1`.
+
+The local `1.0.1.67-beta.1` correction supersedes slice 66's Bright rendering:
+26.3's lightmap uses `minecraft:visual/ambient_light_color`, not the old
+dimension `ambient_light` field. Bright surface/Cave types now set that native
+attribute to white and ambient_light to 1.0. Cave still has no skylight.
+Bright Ages reject natural/chunk-generation hostile spawns independently of
+stored light levels. Existing mobs, passive mobs, spawners, eggs, commands
+and special-event spawns are not deleted or globally disabled. Actual block
+light propagation and plant light requirements are unchanged. Existing Bright
+Ages receive the corrected registered types after restart; no new Age needed.
+
+Planned color-page target: **ambient light color**, alongside sky/celestial
+colors. Reuse the native 26.3 attribute for authored tints; Bright defaults to
+neutral white until the color-page port. This does not enable color pages yet.
+
+The local `1.0.1.68-beta.1` replaces slice 67's special spawn veto with actual
+effective ambient brightness. The spawn event handler is removed. Bright's
+combined light-engine reading now has a minimum of 15 on server and client,
+including after sky darkening. Its white rendering attribute is retained.
+Vanilla darkness checks therefore reject light-sensitive monsters naturally;
+light-ignoring mobs, spawners and other spawn sources use their native rules,
+not Rivencraft exemptions or bans. This does not remove existing mobs.
+
+Ambient light is not stored as emitted block light or fabricated skylight.
+Consumers of combined brightness, including plant light checks, now see the
+ambient contribution. Normal/Dark and non-Rivencraft dimensions are unchanged.
+Cave Bright remains without skylight. Existing Bright Ages update on restart.
+This supersedes slice 67's statement that crop light checks are unchanged.
+
+The local `1.0.1.69-beta.1` slice seed-completes missing weather and lighting
+pages for newly bound books, including Link-Panel-only random Ages. Explicit
+pages take precedence. Cave weather remains Off, while Cave lighting can
+still choose Bright. Old Ages retain their saved choices; they are not rerolled.
+
+The supported pool uses the 1.21.1 Legacy-rank rule: Normal is rank 1, other
+choices rank 2. Lighting weights are 3:1:1 for Normal/Dark/Bright; weather
+weights are 6:1:1:1:1:1 for Normal/Fast/Slow/Off/Always/Storm. The common weight
+is derived from the supported pool size. Unported Cloudy/Rain/Snow modes are
+not selected. Independent seed salts keep a missing lighting roll unchanged
+when weather is explicitly written, and vice versa. This matches the rank
+policy, not the exact 1.21.1 seed stream/pool. No random feature list, sky or
+celestial choices are added by this slice.
+
+`/rivencraft_port age create_random <name> <seed>` uses the same environment
+resolver and logs its frozen plan. `/rivencraft_port age environment_probe
+<seed> <terrain>` inspects deterministic defaults and explicit Storm/Bright
+precedence without creating an Age. Other explicit operator fixtures keep
+their Normal defaults to isolate the feature under test.
+
+For manual checking, create several Link-Panel-only books and verify weather/
+lighting varies across Ages and persists on revisit/restart. Then author an
+explicit Normal Weather + Normal Lighting book, and a Cave + Bright book.
+Include explicit Normal pages when comparing terrain without random lighting
+or weather changes. Random blocklist policy and instability remain pending.
+
+The local `1.0.1.70-beta.1` slice ports the Overworld, Nether, and End Sky
+pages. One sky style is accepted per book and persisted independently of
+terrain, weather and lighting. Missing sky pages still use Overworld; random
+sky selection is not part of this slice. Static Sky remains unsupported/red
+until its Legacy animated renderer is ported, rather than being replaced by
+a flat gray backdrop. Color and individual celestial pages are also pending.
+
+Nether Sky uses the native no-sky backdrop and reddish fog; End Sky uses the
+native End backdrop. Neither changes dimension height, coordinate scale,
+terrain, Nether water/bed rules, or enables an End dragon fight. All lighting
+choices work with these styles, including Cave + Bright. Bright's render
+attribute and effective ambient level 15 are retained on each variant.
+
+The registered variants derive the vanilla Overworld type and preserve its
+gameplay attributes. Non-Overworld skies use a derived day timeline without
+the three sky/fog/cloud tint tracks, retaining native gameplay schedules and
+illumination while avoiding Overworld day tint on those backdrops. Their
+cloud color is transparent. Biome/weather fog modifiers still apply. Types
+sync through normal registry login; no new rendering dependency is required.
+Sky choices survive reload/reseed/restart and retirement rollback. Old Ages
+without a sky choice retain Overworld style.
+
+For visual checks, author Plains + Normal Lighting + No Weather with each
+sky page; compare the sky/fog and verify the same terrain and normal bed/water
+behavior. Then try Cave + Bright + End Sky and revisit after restarting.
+Static Sky should remain red. Operator fixtures:
+`/rivencraft_port age create_sky <name> <seed> <sky> <lighting> <terrain>` and
+`/rivencraft_port age sky_probe <name>`. Use new books to author a sky choice;
+this does not rewrite the sky choice of already-bound books.
+
+The local `1.0.1.71-beta.1` slice adds the previously pending Static Sky.
+Its client renderer adapts the 1.21.1 Legacy-style background: six independent
+48×48 noise faces, default gray tint `#929292`, and noise intensity 65–224.
+The noise updates every two world ticks. A single small dynamic texture and
+cached cube replace thousands of per-cell draw vertices; resources are closed
+with the sky renderer. No artwork or rendering dependency is added.
+
+Static Sky is now supported rather than red, and persists through the same
+Age index as other sky styles. Four registered lighting variants retain the
+existing terrain/gameplay rules. Their native skybox is NONE (no End flashes);
+only the extracted client state schedules the custom background sky pass.
+Animation state resets between frames and does not consult a different live
+world while rendering. Color pages, celestial pages, and random sky selection
+remain pending.
+
+Build and disposable dedicated-server creation/restart checks passed for
+Static + Normal + Standard and Static + Bright + Cave. These do not validate
+client rendering. For manual testing, bind a new Static Sky + Normal Lighting
++ No Weather book, look around/above/below for animated gray static, then
+visit an Overworld/End Sky Age and return to check there is no sky-state leak.
+Revisit after restarting. Also try Static Sky + Cave + Bright (look outside
+terrain or in spectator mode). The fixture accepts `static` as its sky value.
+The dedicated test server was stopped and its temporary world deleted.
+Changes remain local; no commit/push/publication was requested.
+
+From the repository root:
+
+```sh
+./gradlew -p ports/mc263 build
+```
+
+This standalone Gradle build uses Minecraft 26.3, NeoForge 26.3.0.99,
+ModDevGradle 2.0.148, and Java 25. The repository root remains the independent
+Minecraft 1.21.1/Java 21 build:
+
+```sh
+./gradlew build
+```
+
+The beta JAR is under `ports/mc263/build/libs`. Continue the port and its
+full dual-version validation in issues #98–#104 before calling 26.3 stable.
+
+The dedicated development server uses `build/run-server`, with its own world
+and properties. Set a nonconflicting `server-port` there before running if
+another Minecraft server is active. The prototype restores all indexed Ages
+during the Overworld load, before initial chunk preparation completes.

ports/mc263/RELEASE_NOTES_1.0.1.32-beta.1.md

@@ -0,0 +1,19 @@
+# Rivencraft 26.3 beta 1.0.1.32-beta.1
+
+This is the first 26.3 beta, focused on authored Age generation. It is not yet
+feature-complete with the separate Minecraft 1.21.1 release.
+
+- Ported the Book Binder's ordered symbol-page strip and Legacy-inspired GUI,
+  plus runtime symbol artwork, creative pages, and registry-derived biome pages.
+- Ported the Ink Mixer, its additive modifiers, and one-paper/one-ink-unit Link
+  Panel creation.
+- Added authored Standard, Amplified, and Island terrain; fixed, Tiled, Grid,
+  Native, and Tiny through Huge biome distributions; and persistent Age plans.
+- Fixed workstation block-face occlusion beside the Book Binder and Ink Mixer.
+
+Feature/material writing, Cave/Flat/Void terrain, portals, and other 1.21.1
+systems are still being ported. Use a test world and keep a backup. Minecraft
+1.21.1 saves are not supported by this beta.
+
+Requires Minecraft 26.3, NeoForge 26.3.0.99 or a compatible 26.3 build, and
+Java 25.

ports/mc263/RELEASE_NOTES_1.0.1.36-beta.1.md

@@ -0,0 +1,12 @@
+# Rivencraft 26.3 beta 1.0.1.36-beta.1
+
+This beta adds Flat and Void terrain to authored Ages on Minecraft 26.3.
+
+- Bind Descriptive Books with Flat or Void terrain, including multiple Biome pages and supported biome-distribution pages.
+- Flat ground starts at Y=0; travel lands on its surface rather than on an elevated fallback platform.
+- Flat Ages generate the selected biomes' surface decorations, including trees and vegetation. Void Ages remain empty while retaining authored biome climate.
+- Expanded dedicated-server checks for Flat and Void terrain, biome distribution, and persistence after restart.
+
+This 26.3 port is still experimental and does not yet include all features of the separate Minecraft 1.21.1 version. Use a test world and keep a backup. Minecraft 1.21.1 saves are not supported by this beta.
+
+Requires Minecraft 26.3, NeoForge 26.3.0.99 or a compatible 26.3 build, and Java 25.

ports/mc263/RELEASE_NOTES_1.0.1.39-beta.1.md

@@ -0,0 +1,14 @@
+# Rivencraft 26.3 beta 1.0.1.39-beta.1
+
+This beta adds Cave terrain to authored Ages on Minecraft 26.3.
+
+- Bind Descriptive Books with the Cave terrain page and Cave or Nether biome pages, including supported multi-biome distributions.
+- Cave Ages use the cave noise shape but remain dry by default. Newly generated chunks no longer flood below the vanilla cave sea level.
+- Cave travel searches from Y=64 downward for dry, properly footed space instead of landing on the cave roof or underwater.
+- Expanded dedicated-server checks for Cave creation, biome distribution, and persistence after restart.
+
+The player verified the Cave and safe-landing changes in game. Existing generated chunks are not drained or regenerated. A future Flooded page will provide an authored water level; see [issue #107](https://git.paddedcell.org/dnorberg/rivencraft/issues/107).
+
+This 26.3 port is still experimental and does not yet include all features of the separate Minecraft 1.21.1 version. Use a test world and keep a backup. Minecraft 1.21.1 saves are not supported by this beta.
+
+Requires Minecraft 26.3, NeoForge 26.3.0.99 or a compatible 26.3 build, and Java 25.

ports/mc263/RELEASE_NOTES_1.0.1.41-beta.1.md

@@ -0,0 +1,13 @@
+# Rivencraft 26.3 beta 1.0.1.41-beta.1
+
+This beta expands Age generation on Minecraft 26.3.
+
+- Descriptive Books with no authored symbol pages now choose a seeded random terrain and biome distribution. The chosen plan is saved with the Age and restored after restart.
+- A Block material page followed by a Rocks feature page now generates small clusters of that block in newly generated surface chunks. This first feature path supports Standard, Amplified, Island, and Flat terrain; Cave and Void combinations remain unsupported.
+- Expanded dedicated-server checks cover random Age plans and authored Rocks generation across restart.
+
+The player verified the Rocks feature in game. Random feature selection, duplicate feature pages, unpaired materials, and instability scoring are not yet ported. Existing chunks are not regenerated.
+
+This 26.3 port is still experimental and does not yet include all features of the separate Minecraft 1.21.1 version. Use a test world and keep a backup. Minecraft 1.21.1 saves are not supported by this beta.
+
+Requires Minecraft 26.3, NeoForge 26.3.0.99 or a compatible 26.3 build, and Java 25.

ports/mc263/RELEASE_NOTES_1.0.1.54-beta.1.md

@@ -0,0 +1,51 @@
+# Rivencraft 26.3 beta 1.0.1.54-beta.1
+
+This beta collects the player-validated Age feature port slices since
+1.0.1.41-beta.1. It is not yet feature-complete with Minecraft 1.21.1.
+
+## Age generation
+
+- Rocks now use the established 1.21.1 forest-rock placement. Unmodified
+  material-bearing features choose seeded materials independently; a preceding
+  compatible Block or Fluid page selects the material explicitly.
+- Added Flowers, Trees, Huge Trees, Dungeons, Surface Lakes, Deep Lakes, and
+  Small Lakes using the 1.21.1 placement rules adapted to 26.3.
+- Added Floating Islands, Tendrils, Skylands, Spheres, Spikes, and Obelisks
+  using the existing Rivencraft generation algorithms.
+- Added blue Crystal Formations with budding crystal and initially seeded buds.
+- Added Dense Ores: repeated pages replay eligible biome ore placements,
+  including compatible modded ores and explicitly tagged custom placements.
+- Added Star Fissures: one Legacy-shaped rift near the first arrival point,
+  a starfield at the dimension's minimum Y, and return travel to the shared
+  Overworld spawn with the original fissure sound. Cave roofs are preserved.
+- Feature plans, materials, repeated occurrences, and fissure completion
+  persist across restart. Existing generated chunks are not redecorated.
+
+## Current limits
+
+- Authored features retain terrain restrictions. Most repeated features allow
+  up to 32 occurrences; exceeding the current authoring cap blocks assembly.
+  Skylands and Star Fissures retain their single-effect behavior when repeated.
+- Put a material page immediately before a compatible feature. Dangling
+  material assignment, full Legacy grammar recovery, instability, and random
+  feature selection are not yet ported. Pageless books randomize terrain and
+  biome distribution, not the newly authored feature list.
+- 26.3 combines base terrain, surface, and carving. Added solid volumes run
+  after that combined operation and before decoration, so base carvers do not
+  cut those added volumes.
+- The full 1.21.1 writing/discovery loop, structures, environmental systems,
+  crystal portals, and optional integration parity remain in progress. The
+  presence of a Creative page is not a promise that its effect is ported.
+
+Build and static checks passed. The player reported in-game passes for these
+slices. Earlier server smoke coverage was expanded, but the later generation
+slices were manually validated; this release does not claim a new full
+dedicated-server regression pass.
+
+Requires Minecraft **26.3**, NeoForge **26.3.0.99** or a compatible 26.3 build,
+and **Java 25**. Dynamic Dimensions and Bad Packets are not required by this
+26.3 build. Do not use Minecraft 1.21.1 dependencies or saves with it. Back up
+the entire world before updating; beta-save compatibility is not guaranteed.
+
+Report issues and help with documentation at
+[BlackSheep Git](https://git.paddedcell.org/dnorberg/rivencraft).

ports/mc263/RELEASE_NOTES_1.0.1.65-beta.1.md

@@ -0,0 +1,72 @@
+# Rivencraft 26.3 beta 1.0.1.65-beta.1
+
+This beta collects the player-tested port slices since 1.0.1.54-beta.1.
+It is not yet feature-complete with the Minecraft 1.21.1 release.
+
+## Age generation
+
+- Added authored structure pages: Villages, Mineshafts, Strongholds, Trial
+  Chambers, Buried Treasure, Shipwrecks, Ocean Ruins, Pillager Outposts,
+  Ruined Portals, Nether Fossils, Ancient Cities, Trail Ruins, Nether
+  Fortresses, Bastions, and 26.3's Abandoned Camps. Dungeons remain their
+  separate feature.
+- Fixed the early structure-biome check so authored structures can generate
+  outside their native biome restrictions, within the supported terrain rules.
+  Repeated structure pages increase density up to the current authoring cap.
+- Added Caves and Ravines feature pages through 26.3's native carving stage.
+  These are distinct from Cave terrain; Flat/Void support remains pending.
+- Added Poplar Trees, Fallen Poplar Trees, Red Shrubs, and Shelf Mushrooms.
+  Shelf Mushrooms find exposed logs at any height, including log Tendrils in
+  Void terrain. No Trees page is required.
+- Added Normal, Fast, Slow, Off, Always, and Storm weather pages. Each Age
+  has independent saved weather data and timers; its policy does not change
+  the Overworld or other Ages. Cave terrain keeps weather disabled.
+
+## Fixes and feedback
+
+- Non-Cave Descriptive Book arrivals trace actual blocks down from maximum
+  build height instead of using a Flat-layer shortcut or only a heightmap.
+  The search stops at roofs/fluids rather than selecting underground pockets.
+  Leaves count as footing; submerged footing is rejected. Fallback platforms
+  sit above obstructions, with floor Y=63 in an empty Void.
+- Stored surface-Age Star Fissure arrivals are rechecked from above. Cave
+  terrain still searches down from Y=64, and Linking Books retain exact
+  bound destinations.
+- Restored Legacy linking sounds and successful-link cloud bursts. Disarm
+  and Intra-Linking use their respective sounds. Star Fissure return audio
+  also plays after arrival so a dimension switch does not discard it.
+- Fixed weather-only authoring, including Link Panel + Storm books: non-biome
+  pages no longer get interpreted as biome IDs.
+- Unsupported pages now have a red tint and availability tooltip. Supported
+  pages and their descriptions reflect the implemented 26.3 behavior.
+- Added operator weather and surface diagnostics for testing.
+
+## Current limits
+
+- Only the supported page/terrain combinations can be bound. Most repeated
+  features are capped at 32; vegetation uses a combined 32-page limit. The
+  full 1.21.1 grammar recovery and instability systems remain unported.
+- Pageless books currently randomize terrain and biome distribution, not the
+  complete feature/environment list. Omitted weather currently means Normal.
+- Base carvers do not carve authored solid volumes added after 26.3's combined
+  terrain operation. Previously generated chunks are not regenerated.
+- The full writing/discovery loop, celestial/lighting systems, crystal portals,
+  instability, and optional-integration parity remain in progress. Creative
+  availability alone does not mean a page is supported; check its tooltip.
+- Vanilla `/weather` targets global server weather, not the independent Age
+  policy. Biomes retain their normal precipitation rules.
+
+The player reported in-game passes for these slices. Build/static checks passed.
+Targeted disposable dedicated-server checks covered all six weather policies,
+Overworld isolation, unload/reload and restart persistence, weather-only page
+compilation, and dry surface/leaf spawn probes. This is not a claim of full
+dedicated-server or optional-mod regression coverage. Test servers were stopped
+and their temporary worlds removed.
+
+Requires Minecraft **26.3**, NeoForge **26.3.0.99** or a compatible 26.3 build,
+and **Java 25**. This build does not require Dynamic Dimensions or Bad Packets.
+Keep it separate from the 1.21.1 build and saves. Back up entire worlds before
+updating; beta-save compatibility is not guaranteed.
+
+Report issues and help improve the wiki at
+[BlackSheep Git](https://git.paddedcell.org/dnorberg/rivencraft).

ports/mc263/RELEASE_NOTES_1.0.1.71-beta.1.md

@@ -0,0 +1,59 @@
+# Rivencraft 26.3 beta 1.0.1.71-beta.1
+
+This beta collects the player-tested lighting and sky port slices since
+1.0.1.65-beta.1. It is not yet feature-complete with Minecraft 1.21.1.
+
+## Lighting and seeded environments
+
+- Added Normal, Dark, and Bright lighting pages with saved per-Age settings.
+- Bright works in Cave terrain too, without adding skylight or weather.
+- Bright supplies effective ambient light level 15 to native combined-light
+  checks and the white ambient rendering attribute. Vanilla darkness-based
+  monster checks respond to that lighting; there is no separate mob-spawn
+  veto. Mobs that ignore light retain their normal rules.
+- Missing weather and lighting controllers now resolve deterministically from
+  the Age seed, using independent choices and Legacy-style Normal weighting.
+  Explicit pages win; Cave terrain still forces weather Off. Existing Ages
+  keep their saved choices rather than rerolling on load.
+
+## Sky styles
+
+- Added Overworld, Nether, End, and animated Static Sky pages, independently
+  of terrain, weather, and lighting. Choices persist on reload and restart.
+- Nether Sky uses a reddish fog backdrop; End Sky uses the native End sky.
+  These are visual styles, not Nether/End terrain or gameplay conversions:
+  dimension geometry, coordinate scale, bed/water rules, and dragon behavior
+  are not changed.
+- Static Sky adapts the existing Legacy-style renderer: six independent
+  48×48 animated gray noise faces. A cached cube and small dynamic texture
+  avoid rebuilding thousands of per-cell vertices each frame. Client-only
+  rendering resources are released with the sky renderer.
+- Non-Overworld backgrounds have transparent clouds and a derived day
+  timeline that avoids Overworld sky/fog/cloud color tracks while retaining
+  gameplay and illumination schedules.
+- Updated supported-page feedback and added operator sky/environment probes.
+
+## Current limits and testing
+
+- Missing Sky pages still default to Overworld; random sky selection, color
+  pages and individual celestial bodies remain pending. Number-controlled
+  Static Sky resolution is tracked separately in issue #109 for both versions.
+- The writing/discovery loop, instability, portals, and optional-integration
+  parity are still incomplete. Creative availability is not a support claim;
+  check page tooltips and the beta guide for supported combinations.
+- Previously generated chunks are not regenerated. Save compatibility during
+  the beta is not guaranteed; keep backups and keep both version tracks apart.
+
+The player reported in-game passes for the included slices, including Static
+Sky. Build checks passed for both version tracks. Targeted disposable-server
+checks covered environment defaults, explicit choices, registered sky/lighting
+variants, persistence and restart, including Cave + Bright and Static Sky.
+This is not a claim of complete dedicated-server or optional-mod coverage.
+Test servers were stopped and temporary worlds removed.
+
+Requires Minecraft **26.3**, NeoForge **26.3.0.99** and **Java 25**. Dynamic
+Dimensions and Bad Packets are not required by this build. The 1.21.1 release
+and its dependencies are unchanged.
+
+Report issues and help improve the wiki at
+[BlackSheep Git](https://git.paddedcell.org/dnorberg/rivencraft).

ports/mc263/build.gradle

@@ -0,0 +1,267 @@
+plugins {
+    id 'java-library'
+    id 'net.neoforged.moddev' version '2.0.148'
+}
+
+group = 'net.dnorberg.rivencraft'
+version = mod_version
+
+base {
+    archivesName = "rivencraft-${minecraft_version}"
+}
+
+java.toolchain.languageVersion = JavaLanguageVersion.of(25)
+
+neoForge {
+    version = project.neo_version
+    runs {
+        client {
+            client()
+            if (project.hasProperty('connectAddress')) {
+                programArgument '--quickPlayMultiplayer'
+                programArgument project.property('connectAddress').toString()
+            }
+            if (project.hasProperty('clientName')) {
+                programArgument '--username'
+                programArgument project.property('clientName').toString()
+                gameDirectory = project.layout.buildDirectory.dir('run-client-' + project.property('clientName')).get().asFile
+            }
+        }
+        server {
+            server()
+            gameDirectory = project.hasProperty('serverRunDir')
+                    ? file(project.property('serverRunDir').toString())
+                    : project.layout.buildDirectory.dir('run-server').get().asFile
+            programArgument '--nogui'
+        }
+    }
+    mods {
+        rivencraft {
+            sourceSet(sourceSets.main)
+        }
+    }
+}
+
+def generateModMetadata = tasks.register('generateModMetadata', ProcessResources) {
+    def replaceProperties = [
+            mod_id: mod_id,
+            mod_name: mod_name,
+            mod_license: mod_license,
+            mod_version: mod_version,
+            neo_version: neo_version,
+            minecraft_version_range: minecraft_version_range,
+    ]
+    inputs.properties replaceProperties
+    expand replaceProperties
+    from 'src/main/templates'
+    into 'build/generated/sources/modMetadata'
+}
+sourceSets.main.resources.srcDir generateModMetadata
+neoForge.ideSyncTask generateModMetadata
+
+// Keep the bundled page list in step with the 1.21.1 symbol definitions.
+abstract class GeneratePortSymbolIndex extends DefaultTask {
+    @InputDirectory abstract DirectoryProperty getSymbolsDir()
+    @InputDirectory abstract DirectoryProperty getPortSymbolsDir()
+    @OutputDirectory abstract DirectoryProperty getIndexDir()
+
+    @TaskAction void generate() {
+        File root = symbolsDir.get().asFile
+        def definitions = new LinkedHashMap<String, Object>()
+        java.nio.file.Files.walk(root.toPath()).withCloseable { paths ->
+            paths.filter { java.nio.file.Files.isRegularFile(it) && it.toString().endsWith('.json') }
+                    .sorted().forEach { source ->
+                        String path = root.toPath().relativize(source).toString()
+                                .replace('\\', '/').replaceAll(/\.json$/, '')
+                        definitions["rivencraft:${path}"] = new groovy.json.JsonSlurper().parse(source.toFile())
+                    }
+        }
+        File portRoot = portSymbolsDir.get().asFile
+        java.nio.file.Files.walk(portRoot.toPath()).withCloseable { paths ->
+            paths.filter { java.nio.file.Files.isRegularFile(it) && it.toString().endsWith('.json') }
+                    .sorted().forEach { source ->
+                        String path = portRoot.toPath().relativize(source).toString()
+                                .replace('\\', '/').replaceAll(/\.json$/, '')
+                        definitions["rivencraft:${path}"] = new groovy.json.JsonSlurper().parse(source.toFile())
+                    }
+        }
+        File index = new File(indexDir.get().asFile, 'assets/rivencraft/creative_symbol_pages.json')
+        index.parentFile.mkdirs()
+        index.text = groovy.json.JsonOutput.prettyPrint(groovy.json.JsonOutput.toJson(definitions)) + '\n'
+    }
+}
+
+def generatePortSymbolIndex = tasks.register('generatePortSymbolIndex', GeneratePortSymbolIndex) {
+    symbolsDir.set(layout.projectDirectory.dir('../../src/main/resources/data/rivencraft/rivencraft/symbols'))
+    portSymbolsDir.set(layout.projectDirectory.dir('src/main/resources/data/rivencraft/rivencraft/symbols'))
+    indexDir.set(layout.buildDirectory.dir('generated/resources/creativeSymbols'))
+}
+sourceSets.main.resources.srcDir generatePortSymbolIndex
+
+// Use the established symbol names/descriptions without overwriting 26.3-only strings.
+abstract class GeneratePortLanguage extends DefaultTask {
+    @InputFile abstract RegularFileProperty getBaseLanguage()
+    @InputFile abstract RegularFileProperty getPortLanguage()
+    @OutputDirectory abstract DirectoryProperty getOutputDir()
+
+    @TaskAction void generate() {
+        def base = new groovy.json.JsonSlurper().parse(baseLanguage.get().asFile) as Map
+        def port = new groovy.json.JsonSlurper().parse(portLanguage.get().asFile) as Map
+        base.putAll(port)
+        File result = new File(outputDir.get().asFile, 'assets/rivencraft/lang/en_us.json')
+        result.parentFile.mkdirs()
+        result.text = groovy.json.JsonOutput.prettyPrint(groovy.json.JsonOutput.toJson(base)) + '\n'
+    }
+}
+
+def generatePortLanguage = tasks.register('generatePortLanguage', GeneratePortLanguage) {
+    baseLanguage.set(layout.projectDirectory.file('../../src/main/resources/assets/rivencraft/lang/en_us.json'))
+    portLanguage.set(layout.projectDirectory.file('port_en_us.json'))
+    outputDir.set(layout.buildDirectory.dir('generated/resources/portLanguage'))
+}
+sourceSets.main.resources.srcDir generatePortLanguage
+
+// Derive registered presentation variants without duplicating vanilla gameplay settings.
+abstract class GeneratePortDimensionTypes extends DefaultTask {
+    @InputFile abstract RegularFileProperty getMinecraftJar()
+    @OutputDirectory abstract DirectoryProperty getOutputDir()
+
+    @TaskAction void generate() {
+        new java.util.zip.ZipFile(minecraftJar.get().asFile).withCloseable { archive ->
+            def entry = archive.getEntry('data/minecraft/dimension_type/overworld.json')
+            if (entry == null) throw new GradleException('Missing vanilla Overworld dimension type')
+            String template = archive.getInputStream(entry).withCloseable { it.getText('UTF-8') }
+            def dayEntry = archive.getEntry('data/minecraft/timeline/day.json')
+            if (dayEntry == null) throw new GradleException('Missing vanilla day timeline')
+            def day = archive.getInputStream(dayEntry).withCloseable {
+                new groovy.json.JsonSlurper().parseText(it.getText('UTF-8'))
+            }
+            // Keep gameplay schedules and illumination, but do not tint these
+            // native non-Overworld sky backgrounds blue/black with the day cycle.
+            ['fog_color', 'sky_color', 'cloud_color'].each { day.tracks.remove("minecraft:visual/${it}".toString()) }
+            // Markers are global per clock and already owned by minecraft:day.
+            day.remove('time_markers')
+            File dayFile = new File(outputDir.get().asFile, 'data/rivencraft/timeline/age_sky_day.json')
+            dayFile.parentFile.mkdirs()
+            dayFile.text = groovy.json.JsonOutput.prettyPrint(groovy.json.JsonOutput.toJson(day)) + '\n'
+            File timelineTag = new File(outputDir.get().asFile, 'data/rivencraft/tags/timeline/age_sky.json')
+            timelineTag.parentFile.mkdirs()
+            timelineTag.text = groovy.json.JsonOutput.prettyPrint(groovy.json.JsonOutput.toJson([
+                    values: ['#minecraft:universal', 'rivencraft:age_sky_day',
+                             'minecraft:moon', 'minecraft:early_game']])) + '\n'
+            ['overworld', 'nether', 'end', 'static'].each { sky ->
+                ['age_normal', 'age_dark', 'age_bright', 'age_cave_bright'].each { lighting ->
+                    if (sky == 'overworld' && lighting == 'age_normal') return
+                    String name = lighting + (sky == 'overworld' ? '' : "_sky_${sky}")
+                    def definition = new groovy.json.JsonSlurper().parseText(template)
+                    definition.has_skylight = lighting in ['age_normal', 'age_bright']
+                    definition.ambient_light = lighting in ['age_bright', 'age_cave_bright'] ? 1.0 : 0.0
+                    // 26.3's lightmap reads this attribute, not ambient_light.
+                    if (definition.ambient_light == 1.0)
+                        definition.attributes['minecraft:visual/ambient_light_color'] = '#ffffff'
+                    if (sky != 'overworld') {
+                        definition.skybox = sky == 'end' ? 'end' : 'none'
+                        definition.attributes['minecraft:visual/fog_color'] = sky == 'static' ? '#929292' : sky == 'end' ? '#181318' : '#6b2725'
+                        definition.attributes['minecraft:visual/sky_color'] = sky == 'static' ? '#929292' : sky == 'end' ? '#000000' : '#6b2725'
+                        definition.attributes['minecraft:visual/cloud_color'] = '#00000000'
+                        if (sky == 'nether') {
+                            definition.attributes['minecraft:visual/fog_start_distance'] = 10.0
+                            definition.attributes['minecraft:visual/fog_end_distance'] = 96.0
+                        }
+                        definition.timelines = '#rivencraft:age_sky'
+                    }
+                    File result = new File(outputDir.get().asFile, "data/rivencraft/dimension_type/${name}.json")
+                    result.parentFile.mkdirs()
+                    result.text = groovy.json.JsonOutput.prettyPrint(groovy.json.JsonOutput.toJson(definition)) + '\n'
+                }
+            }
+        }
+    }
+}
+
+def generatePortDimensionTypes = tasks.register('generatePortDimensionTypes', GeneratePortDimensionTypes) {
+    dependsOn 'createMinecraftArtifacts'
+    minecraftJar.set(layout.buildDirectory.file("moddev/artifacts/minecraft-patched-${neo_version}.jar"))
+    outputDir.set(layout.buildDirectory.dir('generated/resources/dimensionTypes'))
+}
+sourceSets.main.resources.srcDir generatePortDimensionTypes
+
+tasks.named('processResources', ProcessResources).configure {
+    // Reuse the existing sprite and base model without copying binary assets.
+    from('../../src/main/resources') {
+        include 'data/rivencraft/worldgen/structure_set/fortresses.json'
+        include 'data/rivencraft/worldgen/structure_set/bastions.json'
+        include 'assets/rivencraft/models/block/star_fissure.json'
+        include 'assets/rivencraft/blockstates/star_fissure.json'
+        include 'assets/rivencraft/sounds.json'
+        include 'assets/rivencraft/sounds/**/*.ogg'
+        include 'assets/rivencraft/textures/item/crystal_shard.png'
+        include 'assets/rivencraft/textures/item/page.png'
+        include 'assets/rivencraft/textures/item/page_link_panel.png'
+        include 'assets/rivencraft/textures/item/page_symbol.png'
+        include 'assets/rivencraft/models/item/page_symbol.json'
+        include 'assets/rivencraft/textures/gui/symbolcomponents.png'
+        include 'assets/rivencraft/models/item/page_link_panel.json'
+        include 'assets/rivencraft/textures/item/ink_vial.png'
+        include 'assets/rivencraft/textures/item/ink_vial.png.mcmeta'
+        include 'assets/rivencraft/models/item/ink_vial.json'
+        include 'assets/rivencraft/models/item/crystal_shard.json'
+        include 'assets/rivencraft/textures/item/descriptive_book.png'
+        include 'assets/rivencraft/models/item/descriptive_book.json'
+        include 'assets/rivencraft/textures/item/linking_book.png'
+        include 'assets/rivencraft/textures/item/linking_book_unwritten.png'
+        include 'assets/rivencraft/models/item/linking_book_bound.json'
+        include 'assets/rivencraft/textures/gui/bookui_cover.png'
+        include 'assets/rivencraft/textures/gui/notebook_pages.png'
+        include 'assets/rivencraft/textures/gui/bookui_pager.png'
+        include 'assets/rivencraft/textures/block/crystal_block.png'
+        include 'assets/rivencraft/textures/block/book_binder.png'
+        include 'assets/rivencraft/textures/block/book_binder_press.png'
+        include 'assets/rivencraft/textures/gui/book_binder_legacy.png'
+        include 'assets/rivencraft/textures/gui/ink_mixer_legacy.png'
+        include 'assets/rivencraft/textures/block/inkwell_base.png'
+        include 'assets/rivencraft/textures/block/inkwell_cup.png'
+        include 'assets/rivencraft/textures/block/ink.png'
+        include 'assets/rivencraft/textures/block/ink_glass.png'
+        include 'assets/rivencraft/models/block/ink_mixer.json'
+        include 'assets/rivencraft/models/item/ink_mixer.json'
+        include 'assets/rivencraft/blockstates/ink_mixer.json'
+        include 'data/rivencraft/loot_table/blocks/ink_mixer.json'
+        include 'assets/rivencraft/models/block/book_binder.json'
+        include 'assets/rivencraft/models/item/book_binder.json'
+        include 'assets/rivencraft/blockstates/book_binder.json'
+        include 'data/rivencraft/loot_table/blocks/book_binder.json'
+        include 'assets/rivencraft/models/block/crystal_block.json'
+        include 'assets/rivencraft/blockstates/crystal_block.json'
+        include 'assets/rivencraft/blockstates/budding_crystal.json'
+        include 'assets/rivencraft/blockstates/small_crystal_bud.json'
+        include 'assets/rivencraft/blockstates/medium_crystal_bud.json'
+        include 'assets/rivencraft/blockstates/large_crystal_bud.json'
+        include 'assets/rivencraft/blockstates/crystal_cluster.json'
+        include 'assets/rivencraft/models/block/budding_crystal.json'
+        include 'assets/rivencraft/models/block/small_crystal_bud.json'
+        include 'assets/rivencraft/models/block/medium_crystal_bud.json'
+        include 'assets/rivencraft/models/block/large_crystal_bud.json'
+        include 'assets/rivencraft/models/block/crystal_cluster.json'
+        include 'assets/rivencraft/models/item/budding_crystal.json'
+        include 'assets/rivencraft/models/item/small_crystal_bud.json'
+        include 'assets/rivencraft/models/item/medium_crystal_bud.json'
+        include 'assets/rivencraft/models/item/large_crystal_bud.json'
+        include 'assets/rivencraft/models/item/crystal_cluster.json'
+        include 'assets/rivencraft/textures/block/small_crystal_bud.png'
+        include 'assets/rivencraft/textures/block/medium_crystal_bud.png'
+        include 'assets/rivencraft/textures/block/large_crystal_bud.png'
+        include 'assets/rivencraft/textures/block/crystal_cluster.png'
+        include 'data/rivencraft/loot_table/blocks/crystal_block.json'
+        include 'data/minecraft/tags/block/mineable/pickaxe.json'
+        include 'data/minecraft/tags/item/cluster_max_harvestables.json'
+    }
+}
+
+tasks.withType(JavaCompile).configureEach {
+    options.encoding = 'UTF-8'
+}
+
+tasks.named('runServer').configure {
+    standardInput = System.in
+}

ports/mc263/gradle.properties

@@ -0,0 +1,10 @@
+org.gradle.jvmargs=-Xmx2G
+org.gradle.caching=true
+
+minecraft_version=26.3
+minecraft_version_range=[26.3]
+neo_version=26.3.0.99
+mod_id=rivencraft
+mod_name=Rivencraft
+mod_license=LGPL-3.0-or-later
+mod_version=1.0.1.71-beta.1

ports/mc263/port_en_us.json

@@ -0,0 +1,79 @@
+{
+  "item.rivencraft.crystal_shard": "Crystal Shard",
+  "item.rivencraft.descriptive_book": "Descriptive Book",
+  "item.rivencraft.linking_book": "Linking Book",
+  "item.rivencraft.page": "Page",
+  "item.rivencraft.page.blank": "Blank Page",
+  "item.rivencraft.page.link_panel": "Link Panel Page",
+  "item.rivencraft.page.unresolved": "Unknown Symbol Page",
+  "item.rivencraft.page.symbol.implemented": "Implemented in 26.3; book and terrain requirements still apply.",
+  "symbol.rivencraft.weather.normal.description": "Use an independent normal weather cycle. Cave terrain keeps weather off.",
+  "symbol.rivencraft.sky.overworld.description": "Use the native Overworld sky. Terrain and lighting remain independently authored.",
+  "symbol.rivencraft.sky.nether.description": "Use a Nether-style sky and reddish fog, without Nether terrain or gameplay rules.",
+  "symbol.rivencraft.sky.end.description": "Use the native End sky backdrop, without End terrain or a dragon fight.",
+  "symbol.rivencraft.sky.static.description": "An animated gray static sky surrounds the Age.",
+  "symbol.rivencraft.lighting.normal.description": "Use normal skylight and ambient brightness. Cave terrain remains without skylight.",
+  "symbol.rivencraft.lighting.dark.description": "Remove skylight from this Age; placed light sources still work.",
+  "symbol.rivencraft.lighting.bright.description": "Provide full ambient brightness and effective light level 15. Vanilla light-based spawn rules apply, including in Cave terrain without skylight.",
+  "symbol.rivencraft.weather.fast.description": "Use the faster Legacy weather cycle in this Age only. Cave terrain keeps weather off.",
+  "symbol.rivencraft.weather.slow.description": "Use the slower Legacy weather cycle in this Age only. Cave terrain keeps weather off.",
+  "symbol.rivencraft.weather.off.description": "Keep this Age clear without changing Overworld weather.",
+  "symbol.rivencraft.weather.always.description": "Keep this Age rainy, or snowy in cold biomes, without thunder. Cave terrain keeps weather off.",
+  "symbol.rivencraft.weather.storm.description": "Keep this Age rainy and thundering. Precipitation still depends on the biome; Cave terrain keeps weather off.",
+  "item.rivencraft.page.symbol.unimplemented": "Not yet implemented in 26.3; cannot be bound into an Age.",
+  "item.rivencraft.link_property.disarm": "Disarm",
+  "item.rivencraft.link_property.maintain_momentum": "Maintain Momentum",
+  "item.rivencraft.link_property.intra_linking": "Intra-Linking",
+  "item.rivencraft.ink_vial": "Ink Vial",
+  "item.rivencraft.ink_vial.remaining": "Ink: %s/%s",
+  "item.rivencraft.ink_vial.usage": "Use with paper in the other hand, or place in an Ink Mixer.",
+  "item.rivencraft.page.blank.port_status": "Internal symbol-page base; not an authoring ingredient.",
+  "item.rivencraft.page.link_panel.port_status": "Use with leather in a Book Binder to make a Descriptive Book.",
+  "block.rivencraft.book_binder": "Book Binder",
+  "container.rivencraft.book_binder": "Book Binder",
+  "screen.rivencraft.book_binder.missing_panel": "Link Panel required",
+  "screen.rivencraft.book_binder.authored_pending": "Unsupported page or page combination",
+  "block.rivencraft.ink_mixer": "Ink Mixer",
+  "container.rivencraft.ink_mixer": "Ink Mixer",
+  "screen.rivencraft.ink_mixer.ink": "Ink: %s/%s",
+  "screen.rivencraft.ink_mixer.additive_hint": "Click with an additive to mix it in",
+  "screen.rivencraft.ink_mixer.chance": "%s: %s%%",
+  "block.rivencraft.crystal_block": "Crystal Block",
+  "block.rivencraft.budding_crystal": "Budding Crystal",
+  "block.rivencraft.small_crystal_bud": "Small Crystal Bud",
+  "block.rivencraft.medium_crystal_bud": "Medium Crystal Bud",
+  "block.rivencraft.large_crystal_bud": "Large Crystal Bud",
+  "block.rivencraft.crystal_cluster": "Crystal Cluster",
+  "itemGroup.rivencraft": "Rivencraft",
+  "itemGroup.rivencraft.pages.link": "Rivencraft Link Pages",
+  "symbol.rivencraft.feature.poplar_trees": "Poplar Trees",
+  "symbol.rivencraft.feature.poplar_trees.description": "Add red, orange, and yellow poplar trees to surface terrain with suitable soil.",
+  "symbol.rivencraft.feature.fallen_poplar_trees": "Fallen Poplar Trees",
+  "symbol.rivencraft.feature.fallen_poplar_trees.description": "Add fallen poplar logs and stumps to surface terrain with suitable soil.",
+  "symbol.rivencraft.feature.shelf_mushrooms": "Shelf Mushrooms",
+  "symbol.rivencraft.feature.shelf_mushrooms.description": "Add shelf mushrooms to exposed log faces on any terrain, including Void. No tree page is required.",
+  "symbol.rivencraft.feature.red_shrubs": "Red Shrubs",
+  "symbol.rivencraft.feature.red_shrubs.description": "Add red shrub patches to surface terrain with suitable ground.",
+  "symbol.rivencraft.feature.abandoned_camps": "Abandoned Camps",
+  "symbol.rivencraft.feature.abandoned_camps.description": "Allow abandoned camps on surface noise terrain, including outside their usual biomes.",
+  "symbol.rivencraft.block.generated.description": "Place immediately before a compatible feature; unpaired materials are not yet supported.",
+  "symbol.rivencraft.biome.native.description": "Use the terrain's native biome source; do not include Biome pages.",
+  "symbol.rivencraft.terrain.flat.description": "A level, biome-decorated landscape with its foundation at Y=0.",
+  "symbol.rivencraft.feature.floating_islands.description": "Add high floating islands alongside noise, Flat, or Void terrain; not Cave terrain.",
+  "symbol.rivencraft.feature.caves.description": "Add extra cave carving to noise terrain, including Cave; not Flat or Void.",
+  "symbol.rivencraft.feature.ravines.description": "Add canyon carving to noise terrain; not Flat or Void. Skips Nether biomes.",
+  "symbol.rivencraft.feature.mineshafts.description": "Allow mineshafts in noise terrain, including Cave, regardless of normal biome eligibility.",
+  "symbol.rivencraft.feature.nether_fortresses.description": "Allow Nether fortresses in Cave terrain; the authored page overrides biome eligibility.",
+  "symbol.rivencraft.feature.strongholds.description": "Allow strongholds in surface noise or Flat terrain, including outside their usual biomes.",
+  "symbol.rivencraft.feature.villages.description": "Allow villages in surface noise or Flat terrain, including outside their usual biomes.",
+  "symbol.rivencraft.feature.trial_chambers.description": "Allow underground Trial Chambers in noise terrain, including Cave, regardless of biome eligibility.",
+  "symbol.rivencraft.feature.bastions.description": "Allow Bastion Remnants in Cave terrain; the authored page overrides biome eligibility.",
+  "symbol.rivencraft.feature.buried_treasure.description": "Allow buried treasure in surface noise terrain; biome eligibility is overridden, but suitable terrain is required.",
+  "symbol.rivencraft.feature.shipwrecks.description": "Allow shipwrecks in surface noise terrain, including outside their usual ocean and beach biomes.",
+  "symbol.rivencraft.feature.ocean_ruins.description": "Allow ocean ruins in surface noise terrain, including outside their usual biomes.",
+  "symbol.rivencraft.feature.pillager_outposts.description": "Allow pillager outposts in surface noise terrain, including outside their usual biomes.",
+  "symbol.rivencraft.feature.ruined_portals.description": "Allow ruined portals in noise terrain, including Cave, regardless of normal biome eligibility.",
+  "symbol.rivencraft.feature.nether_fossils.description": "Allow Nether fossils in Cave terrain; the authored page overrides biome eligibility.",
+  "symbol.rivencraft.feature.ancient_cities.description": "Allow underground Ancient Cities in noise terrain, including Cave, regardless of biome eligibility.",
+  "symbol.rivencraft.feature.trail_ruins.description": "Allow Trail Ruins in surface noise terrain, including outside their usual biomes."
+}

ports/mc263/settings.gradle

@@ -0,0 +1,11 @@
+pluginManagement {
+    repositories {
+        gradlePluginPortal()
+    }
+}
+
+plugins {
+    id 'org.gradle.toolchains.foojay-resolver-convention' version '1.0.0'
+}
+
+rootProject.name = 'rivencraft-mc263-port'

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

@@ -0,0 +1,190 @@
+package net.dnorberg.rivencraft;
+
+import com.mojang.logging.LogUtils;
+import com.mojang.serialization.Codec;
+import net.dnorberg.rivencraft.age.RuntimeAgeBackend;
+import net.dnorberg.rivencraft.age.PortAgeCommands;
+import net.dnorberg.rivencraft.age.AgeCatalogSync;
+import net.dnorberg.rivencraft.block.BuddingCrystalBlock;
+import net.dnorberg.rivencraft.block.PortBookBinderBlock;
+import net.dnorberg.rivencraft.block.InkMixerBlock;
+import net.dnorberg.rivencraft.block.StarFissureBlock;
+import net.dnorberg.rivencraft.block.entity.StarFissureBlockEntity;
+import net.dnorberg.rivencraft.block.entity.PortBookBinderBlockEntity;
+import net.dnorberg.rivencraft.block.entity.InkMixerBlockEntity;
+import net.dnorberg.rivencraft.menu.PortBookBinderMenu;
+import net.dnorberg.rivencraft.menu.InkMixerMenu;
+import net.dnorberg.rivencraft.item.DescriptiveBookItem;
+import net.dnorberg.rivencraft.item.LinkBookTarget;
+import net.dnorberg.rivencraft.item.LinkProperties;
+import net.dnorberg.rivencraft.item.InkVialItem;
+import net.dnorberg.rivencraft.item.LinkingBookItem;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.network.PortBookNetworking;
+import net.dnorberg.rivencraft.registry.ModCreativeTabs;
+import net.dnorberg.rivencraft.registry.PortBiomeSources;
+import net.dnorberg.rivencraft.registry.PortChunkGenerators;
+import net.dnorberg.rivencraft.writing.LinkingBookRecipe;
+import net.minecraft.core.component.DataComponentType;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.sounds.SoundEvent;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.AmethystClusterBlock;
+import net.minecraft.world.level.block.state.BlockBehaviour;
+import net.minecraft.world.level.material.MapColor;
+import net.minecraft.world.item.BlockItem;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.crafting.RecipeSerializer;
+import net.minecraft.world.inventory.MenuType;
+import net.minecraft.world.level.block.entity.BlockEntityType;
+import net.neoforged.bus.api.IEventBus;
+import net.neoforged.fml.common.Mod;
+import net.neoforged.neoforge.registries.DeferredBlock;
+import net.neoforged.neoforge.registries.DeferredItem;
+import net.neoforged.neoforge.registries.DeferredRegister;
+import net.neoforged.neoforge.common.extensions.IMenuTypeExtension;
+import java.util.function.Supplier;
+import net.neoforged.neoforge.common.NeoForge;
+import org.slf4j.Logger;
+
+/** First 26.3 registry slice; gameplay remains in the 1.21.1 target for now. */
+@Mod(Rivencraft.MOD_ID)
+public final class Rivencraft {
+    public static final String MOD_ID = "rivencraft";
+    public static final Logger LOGGER = LogUtils.getLogger();
+    private static final DeferredRegister.Blocks BLOCKS = DeferredRegister.createBlocks(MOD_ID);
+    private static final DeferredRegister.Items ITEMS = DeferredRegister.createItems(MOD_ID);
+    private static final DeferredRegister<SoundEvent> SOUNDS =
+            DeferredRegister.create(Registries.SOUND_EVENT, MOD_ID);
+    public static final Supplier<SoundEvent> LINK = sound("linking.link");
+    public static final Supplier<SoundEvent> LINK_DISARM = sound("linking.link-disarm");
+    public static final Supplier<SoundEvent> LINK_INTRA = sound("linking.link-intra");
+    public static final Supplier<SoundEvent> LINK_FISSURE = sound("linking.link-fissure");
+    public static final Supplier<SoundEvent> LINK_PORTAL = sound("linking.link-portal");
+    public static final Supplier<SoundEvent> METEOR_ROAR = sound("entity.meteor.roar");
+
+    private static Supplier<SoundEvent> sound(String name) {
+        return SOUNDS.register(name, () -> SoundEvent.createVariableRangeEvent(
+                Identifier.fromNamespaceAndPath(MOD_ID, name)));
+    }
+    private static final DeferredRegister<BlockEntityType<?>> BLOCK_ENTITY_TYPES =
+            DeferredRegister.create(Registries.BLOCK_ENTITY_TYPE, MOD_ID);
+    private static final DeferredRegister<MenuType<?>> MENUS =
+            DeferredRegister.create(Registries.MENU, MOD_ID);
+    private static final DeferredRegister<RecipeSerializer<?>> RECIPE_SERIALIZERS =
+            DeferredRegister.create(Registries.RECIPE_SERIALIZER, MOD_ID);
+    private static final DeferredRegister.DataComponents COMPONENTS =
+            DeferredRegister.createDataComponents(Registries.DATA_COMPONENT_TYPE, MOD_ID);
+
+    public static final Supplier<DataComponentType<Identifier>> AGE_BOOK_ID = COMPONENTS.registerComponentType(
+            "age_book_id", builder -> builder.persistent(Identifier.CODEC)
+                    .networkSynchronized(Identifier.STREAM_CODEC));
+    public static final Supplier<DataComponentType<LinkBookTarget>> LINK_BOOK_TARGET = COMPONENTS.registerComponentType(
+            "link_book_target", builder -> builder.persistent(LinkBookTarget.CODEC)
+                    .networkSynchronized(LinkBookTarget.STREAM_CODEC));
+    /** A present component distinguishes Link Panels from unwritten base Pages. */
+    public static final Supplier<DataComponentType<Boolean>> LINK_PANEL_PAGE = COMPONENTS.registerComponentType(
+            "link_panel_page", builder -> builder.persistent(Codec.BOOL)
+                    .networkSynchronized(ByteBufCodecs.BOOL));
+    public static final Supplier<DataComponentType<Identifier>> SYMBOL_PAGE_ID = COMPONENTS.registerComponentType(
+            "symbol_page_id", builder -> builder.persistent(Identifier.CODEC)
+                    .networkSynchronized(Identifier.STREAM_CODEC));
+    /** Ordered authored page IDs remain on the finished book for later port slices. */
+    public static final Supplier<DataComponentType<java.util.List<Identifier>>> BOOK_SYMBOLS = COMPONENTS.registerComponentType(
+            "book_symbols", builder -> builder.persistent(Identifier.CODEC.listOf())
+                    .networkSynchronized(ByteBufCodecs.<io.netty.buffer.ByteBuf, Identifier>list(252)
+                            .apply(Identifier.STREAM_CODEC)));
+    /** Set only on temporary GUI stacks; NeoForge 26.3 requires a registered codec. */
+    public static final Supplier<DataComponentType<Boolean>> PAGE_GLYPH_ONLY = COMPONENTS.registerComponentType(
+            "page_glyph_only", builder -> builder.persistent(Codec.BOOL)
+                    .networkSynchronized(ByteBufCodecs.BOOL));
+    public static final Supplier<DataComponentType<Integer>> INK_REMAINING = COMPONENTS.registerComponentType(
+            "ink_remaining", builder -> builder.persistent(Codec.INT)
+                    .networkSynchronized(ByteBufCodecs.VAR_INT));
+    public static final Supplier<DataComponentType<LinkProperties>> LINK_PROPERTIES = COMPONENTS.registerComponentType(
+            "link_properties", builder -> builder.persistent(LinkProperties.CODEC)
+                    .networkSynchronized(LinkProperties.STREAM_CODEC));
+
+    public static final DeferredBlock<Block> CRYSTAL_BLOCK = BLOCKS.registerBlock("crystal_block",
+            Block::new, () -> BlockBehaviour.Properties.ofFullCopy(Blocks.AMETHYST_BLOCK));
+    public static final DeferredBlock<StarFissureBlock> STAR_FISSURE =
+            BLOCKS.registerBlock("star_fissure", StarFissureBlock::new,
+                    () -> BlockBehaviour.Properties.ofFullCopy(Blocks.END_PORTAL).lightLevel(state -> 6));
+    public static final Supplier<BlockEntityType<StarFissureBlockEntity>>
+            STAR_FISSURE_BLOCK_ENTITY = BLOCK_ENTITY_TYPES.register("star_fissure", () -> new BlockEntityType<>(
+                    StarFissureBlockEntity::new, STAR_FISSURE.get()));
+    public static final DeferredBlock<PortBookBinderBlock> BOOK_BINDER = BLOCKS.registerBlock(
+            "book_binder", PortBookBinderBlock::new,
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion());
+    public static final DeferredItem<BlockItem> BOOK_BINDER_ITEM = ITEMS.registerSimpleBlockItem(BOOK_BINDER);
+    public static final DeferredBlock<InkMixerBlock> INK_MIXER = BLOCKS.registerBlock(
+            "ink_mixer", InkMixerBlock::new,
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.CRAFTING_TABLE).noOcclusion());
+    public static final DeferredItem<BlockItem> INK_MIXER_ITEM = ITEMS.registerSimpleBlockItem(INK_MIXER);
+    public static final Supplier<BlockEntityType<PortBookBinderBlockEntity>> BOOK_BINDER_BLOCK_ENTITY =
+            BLOCK_ENTITY_TYPES.register("book_binder", () ->
+                    new BlockEntityType<>(PortBookBinderBlockEntity::new, BOOK_BINDER.get()));
+    public static final Supplier<MenuType<PortBookBinderMenu>> BOOK_BINDER_MENU =
+            MENUS.register("book_binder", () -> IMenuTypeExtension.create(PortBookBinderMenu::new));
+    public static final Supplier<BlockEntityType<InkMixerBlockEntity>> INK_MIXER_BLOCK_ENTITY =
+            BLOCK_ENTITY_TYPES.register("ink_mixer", () ->
+                    new BlockEntityType<>(InkMixerBlockEntity::new, INK_MIXER.get()));
+    public static final Supplier<MenuType<InkMixerMenu>> INK_MIXER_MENU =
+            MENUS.register("ink_mixer", () -> IMenuTypeExtension.create(InkMixerMenu::new));
+    public static final DeferredItem<BlockItem> CRYSTAL_BLOCK_ITEM = ITEMS.registerSimpleBlockItem(CRYSTAL_BLOCK);
+    public static final DeferredBlock<BuddingCrystalBlock> BUDDING_CRYSTAL = BLOCKS.registerBlock(
+            "budding_crystal", BuddingCrystalBlock::new,
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.BUDDING_AMETHYST).mapColor(MapColor.COLOR_BLUE));
+    public static final DeferredItem<BlockItem> BUDDING_CRYSTAL_ITEM = ITEMS.registerSimpleBlockItem(BUDDING_CRYSTAL);
+    public static final DeferredBlock<AmethystClusterBlock> SMALL_CRYSTAL_BUD = BLOCKS.registerBlock(
+            "small_crystal_bud", properties -> new AmethystClusterBlock(3.0F, 4.0F, properties),
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.SMALL_AMETHYST_BUD));
+    public static final DeferredItem<BlockItem> SMALL_CRYSTAL_BUD_ITEM = ITEMS.registerSimpleBlockItem(SMALL_CRYSTAL_BUD);
+    public static final DeferredBlock<AmethystClusterBlock> MEDIUM_CRYSTAL_BUD = BLOCKS.registerBlock(
+            "medium_crystal_bud", properties -> new AmethystClusterBlock(4.0F, 3.0F, properties),
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.MEDIUM_AMETHYST_BUD));
+    public static final DeferredItem<BlockItem> MEDIUM_CRYSTAL_BUD_ITEM = ITEMS.registerSimpleBlockItem(MEDIUM_CRYSTAL_BUD);
+    public static final DeferredBlock<AmethystClusterBlock> LARGE_CRYSTAL_BUD = BLOCKS.registerBlock(
+            "large_crystal_bud", properties -> new AmethystClusterBlock(5.0F, 3.0F, properties),
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.LARGE_AMETHYST_BUD));
+    public static final DeferredItem<BlockItem> LARGE_CRYSTAL_BUD_ITEM = ITEMS.registerSimpleBlockItem(LARGE_CRYSTAL_BUD);
+    public static final DeferredBlock<AmethystClusterBlock> CRYSTAL_CLUSTER = BLOCKS.registerBlock(
+            "crystal_cluster", properties -> new AmethystClusterBlock(7.0F, 3.0F, properties),
+            () -> BlockBehaviour.Properties.ofFullCopy(Blocks.AMETHYST_CLUSTER));
+    public static final DeferredItem<BlockItem> CRYSTAL_CLUSTER_ITEM = ITEMS.registerSimpleBlockItem(CRYSTAL_CLUSTER);
+    public static final DeferredItem<Item> CRYSTAL_SHARD = ITEMS.registerSimpleItem("crystal_shard");
+    public static final DeferredItem<PageItem> PAGE = ITEMS.registerItem("page", PageItem::new);
+    public static final DeferredItem<InkVialItem> INK_VIAL = ITEMS.registerItem(
+            "ink_vial", InkVialItem::new, properties -> properties.stacksTo(16));
+    public static final DeferredItem<DescriptiveBookItem> DESCRIPTIVE_BOOK = ITEMS.registerItem(
+            "descriptive_book", DescriptiveBookItem::new, properties -> properties.stacksTo(1));
+    public static final DeferredItem<LinkingBookItem> LINKING_BOOK = ITEMS.registerItem(
+            "linking_book", LinkingBookItem::new, properties -> properties.stacksTo(1));
+    public static final Supplier<RecipeSerializer<LinkingBookRecipe>> LINKING_BOOK_RECIPE =
+            RECIPE_SERIALIZERS.register("linking_book", () -> LinkingBookRecipe.SERIALIZER);
+
+    public Rivencraft(IEventBus modEventBus) {
+        BLOCKS.register(modEventBus);
+        SOUNDS.register(modEventBus);
+        ITEMS.register(modEventBus);
+        BLOCK_ENTITY_TYPES.register(modEventBus);
+        MENUS.register(modEventBus);
+        COMPONENTS.register(modEventBus);
+        RECIPE_SERIALIZERS.register(modEventBus);
+        ModCreativeTabs.register(modEventBus);
+        PortBiomeSources.register(modEventBus);
+        PortChunkGenerators.register(modEventBus);
+        NeoForge.EVENT_BUS.addListener(RuntimeAgeBackend::onLevelLoad);
+        NeoForge.EVENT_BUS.addListener(net.dnorberg.rivencraft.age.PortAgeWeather::onLevelTickPre);
+        NeoForge.EVENT_BUS.addListener(PortAgeCommands::register);
+        NeoForge.EVENT_BUS.addListener(AgeCatalogSync::onLogin);
+        NeoForge.EVENT_BUS.addListener(AgeCatalogSync::onLogout);
+        NeoForge.EVENT_BUS.addListener(AgeCatalogSync::onServerStopped);
+        modEventBus.addListener(AgeCatalogSync::registerPayloads);
+        modEventBus.addListener(PortBookNetworking::registerPayloads);
+        LOGGER.info("Initializing Rivencraft 26.3 port slice (not release-ready)");
+    }
+}

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

@@ -0,0 +1,22 @@
+package net.dnorberg.rivencraft.age;
+
+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;
+
+/** Acknowledges the exact catalog version applied on the client main thread. */
+public record AgeCatalogAckPayload(int version) implements CustomPacketPayload {
+    public static final Type<AgeCatalogAckPayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age_catalog_ack"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, AgeCatalogAckPayload> STREAM_CODEC = StreamCodec.composite(
+            ByteBufCodecs.VAR_INT, AgeCatalogAckPayload::version, AgeCatalogAckPayload::new
+    );
+
+    @Override
+    public Type<AgeCatalogAckPayload> type() {
+        return TYPE;
+    }
+}

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

@@ -0,0 +1,29 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.network.protocol.common.custom.CustomPacketPayload;
+import net.minecraft.resources.Identifier;
+
+/** Full server level catalog, sent on login and after a runtime Age is added. */
+public record AgeCatalogPayload(int version, List<Identifier> dimensions) implements CustomPacketPayload {
+    public static final Type<AgeCatalogPayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age_catalog"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, AgeCatalogPayload> STREAM_CODEC = StreamCodec.composite(
+            ByteBufCodecs.VAR_INT, AgeCatalogPayload::version,
+            Identifier.STREAM_CODEC.apply(ByteBufCodecs.list()), AgeCatalogPayload::dimensions,
+            AgeCatalogPayload::new
+    );
+
+    public AgeCatalogPayload {
+        dimensions = List.copyOf(dimensions);
+    }
+
+    @Override
+    public Type<AgeCatalogPayload> type() {
+        return TYPE;
+    }
+}

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

@@ -0,0 +1,102 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.HashMap;
+import java.util.IdentityHashMap;
+import java.util.Map;
+import java.util.UUID;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerPlayer;
+import net.neoforged.neoforge.event.entity.player.PlayerEvent;
+import net.neoforged.neoforge.event.server.ServerStoppedEvent;
+import net.neoforged.neoforge.network.PacketDistributor;
+import net.neoforged.neoforge.network.event.RegisterPayloadHandlersEvent;
+
+/** Refuses runtime-Age travel until the connected client confirms its catalog. */
+public final class AgeCatalogSync {
+    private static final Map<MinecraftServer, State> STATES = new IdentityHashMap<>();
+
+    private AgeCatalogSync() {
+    }
+
+    public static void registerPayloads(RegisterPayloadHandlersEvent event) {
+        var registrar = event.registrar("1");
+        registrar.playToClient(AgeCatalogPayload.TYPE, AgeCatalogPayload.STREAM_CODEC);
+        registrar.playToServer(AgeCatalogAckPayload.TYPE, AgeCatalogAckPayload.STREAM_CODEC,
+                (payload, context) -> {
+                    if (context.player() instanceof ServerPlayer player) acknowledge(player, payload.version());
+                });
+    }
+
+    public static void onLogin(PlayerEvent.PlayerLoggedInEvent event) {
+        if (event.getEntity() instanceof ServerPlayer player) {
+            try {
+                send(player);
+            } catch (RuntimeException exception) {
+                Rivencraft.LOGGER.error("Could not send initial Age catalog to {}; travel remains blocked",
+                        player.getName().getString(), exception);
+            }
+        }
+    }
+
+    public static void onLogout(PlayerEvent.PlayerLoggedOutEvent event) {
+        if (event.getEntity() instanceof ServerPlayer player) {
+            State state = STATES.get(player.level().getServer());
+            if (state != null) state.acknowledged.remove(player.getUUID());
+        }
+    }
+
+    public static void onServerStopped(ServerStoppedEvent event) {
+        STATES.remove(event.getServer());
+    }
+
+    public static void onCatalogChanged(MinecraftServer server) {
+        State state = state(server);
+        state.version++;
+        state.acknowledged.clear();
+        for (ServerPlayer player : server.getPlayerList().getPlayers()) {
+            try {
+                send(player);
+            } catch (RuntimeException exception) {
+                Rivencraft.LOGGER.error("Could not send Age catalog to {}; travel remains blocked",
+                        player.getName().getString(), exception);
+            }
+        }
+    }
+
+    public static boolean ready(ServerPlayer player, Identifier target) {
+        MinecraftServer server = player.level().getServer();
+        State state = state(server);
+        return state.version == state.acknowledged.getOrDefault(player.getUUID(), -1)
+                && server.levelKeys().stream().anyMatch(key -> key.identifier().equals(target));
+    }
+
+    private static void send(ServerPlayer player) {
+        MinecraftServer server = player.level().getServer();
+        State state = state(server);
+        state.acknowledged.remove(player.getUUID());
+        var dimensions = server.levelKeys().stream().map(key -> key.identifier()).sorted().toList();
+        PacketDistributor.sendToPlayer(player, new AgeCatalogPayload(state.version, dimensions));
+    }
+
+    private static void acknowledge(ServerPlayer player, int version) {
+        State state = state(player.level().getServer());
+        if (version != state.version) {
+            Rivencraft.LOGGER.warn("Ignoring stale Age catalog acknowledgement {} from {} (current {})",
+                    version, player.getName().getString(), state.version);
+            return;
+        }
+        state.acknowledged.put(player.getUUID(), version);
+        Rivencraft.LOGGER.info("Age catalog {} acknowledged by {}", version, player.getName().getString());
+    }
+
+    private static State state(MinecraftServer server) {
+        return STATES.computeIfAbsent(server, ignored -> new State());
+    }
+
+    private static final class State {
+        private int version = 1;
+        private final Map<UUID, Integer> acknowledged = new HashMap<>();
+    }
+}

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

@@ -0,0 +1,193 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Server-owned seed index for the first-party 26.3 runtime-level prototype. */
+final class AgeLevelIndex extends SavedData {
+    private static final Codec<AgeLevelIndex> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Codec.unboundedMap(Identifier.CODEC, Codec.LONG).fieldOf("ages").forGetter(index -> index.ages),
+            Identifier.CODEC.listOf().optionalFieldOf("retired", List.of())
+                    .forGetter(index -> List.copyOf(index.retired)),
+            Codec.unboundedMap(Identifier.CODEC, Identifier.CODEC).optionalFieldOf("biome_overrides", Map.of())
+                    .forGetter(index -> index.biomeOverrides),
+            Codec.unboundedMap(Identifier.CODEC, PortBiomePlan.CODEC).optionalFieldOf("biome_plans", Map.of())
+                    .forGetter(index -> index.biomePlans),
+            Codec.unboundedMap(Identifier.CODEC,
+                    Codec.STRING.xmap(PortAgeTerrain::valueOf, PortAgeTerrain::name))
+                    .optionalFieldOf("terrain", Map.of()).forGetter(index -> index.terrain),
+            Codec.unboundedMap(Identifier.CODEC, PortRockPlan.CODEC).optionalFieldOf("rocks", Map.of())
+                    .forGetter(index -> index.rocks),
+            Codec.unboundedMap(Identifier.CODEC, PortVegetationPlan.CODEC)
+                    .optionalFieldOf("vegetation", Map.of()).forGetter(index -> index.vegetation),
+            Codec.unboundedMap(Identifier.CODEC, Codec.intRange(1, 32))
+                    .optionalFieldOf("dungeons", Map.of()).forGetter(index -> index.dungeons),
+            Codec.unboundedMap(Identifier.CODEC, PortLakePlan.CODEC)
+                    .optionalFieldOf("lakes", Map.of()).forGetter(index -> index.lakes),
+            Codec.unboundedMap(Identifier.CODEC, PortTerrainFeaturePlan.CODEC)
+                    .optionalFieldOf("terrain_features", Map.of()).forGetter(index -> index.terrainFeatures),
+            Codec.unboundedMap(Identifier.CODEC, PortLighting.CODEC)
+                    .optionalFieldOf("lighting", Map.of()).forGetter(index -> index.lighting),
+            Codec.unboundedMap(Identifier.CODEC, PortSkyStyle.CODEC)
+                    .optionalFieldOf("sky", Map.of()).forGetter(index -> index.sky)
+    ).apply(instance, AgeLevelIndex::new));
+
+    static final SavedDataType<AgeLevelIndex> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "runtime_ages"),
+            AgeLevelIndex::new,
+            CODEC
+    );
+
+    private final Map<Identifier, Long> ages;
+    private final Set<Identifier> retired;
+    private final Map<Identifier, Identifier> biomeOverrides;
+    private final Map<Identifier, PortBiomePlan> biomePlans;
+    private final Map<Identifier, PortAgeTerrain> terrain;
+    private final Map<Identifier, PortRockPlan> rocks;
+    private final Map<Identifier, PortVegetationPlan> vegetation;
+    private final Map<Identifier, Integer> dungeons;
+    private final Map<Identifier, PortLakePlan> lakes;
+    private final Map<Identifier, PortTerrainFeaturePlan> terrainFeatures;
+    private final Map<Identifier, PortLighting> lighting;
+    private final Map<Identifier, PortSkyStyle> sky;
+
+    private AgeLevelIndex() {
+        this.ages = new LinkedHashMap<>();
+        this.retired = new LinkedHashSet<>();
+        this.biomeOverrides = new LinkedHashMap<>();
+        this.biomePlans = new LinkedHashMap<>();
+        this.terrain = new LinkedHashMap<>();
+        this.rocks = new LinkedHashMap<>();
+        this.vegetation = new LinkedHashMap<>();
+        this.dungeons = new LinkedHashMap<>();
+        this.lakes = new LinkedHashMap<>();
+        this.terrainFeatures = new LinkedHashMap<>();
+        this.lighting = new LinkedHashMap<>();
+        this.sky = new LinkedHashMap<>();
+    }
+
+    private AgeLevelIndex(Map<Identifier, Long> ages, List<Identifier> retired,
+                          Map<Identifier, Identifier> biomeOverrides,
+                          Map<Identifier, PortBiomePlan> biomePlans,
+                          Map<Identifier, PortAgeTerrain> terrain,
+                          Map<Identifier, PortRockPlan> rocks,
+                          Map<Identifier, PortVegetationPlan> vegetation,
+                          Map<Identifier, Integer> dungeons,
+                          Map<Identifier, PortLakePlan> lakes,
+                          Map<Identifier, PortTerrainFeaturePlan> terrainFeatures,
+                          Map<Identifier, PortLighting> lighting,
+                          Map<Identifier, PortSkyStyle> sky) {
+        this.ages = new LinkedHashMap<>(ages);
+        this.retired = new LinkedHashSet<>(retired);
+        this.biomeOverrides = new LinkedHashMap<>(biomeOverrides);
+        this.biomePlans = new LinkedHashMap<>(biomePlans);
+        this.terrain = new LinkedHashMap<>(terrain);
+        this.rocks = new LinkedHashMap<>(rocks);
+        this.vegetation = new LinkedHashMap<>(vegetation);
+        this.dungeons = new LinkedHashMap<>(dungeons);
+        this.lakes = new LinkedHashMap<>(lakes);
+        this.terrainFeatures = new LinkedHashMap<>(terrainFeatures);
+        this.lighting = new LinkedHashMap<>(lighting);
+        this.sky = new LinkedHashMap<>(sky);
+    }
+
+    Map<Identifier, Long> entries() {
+        return Map.copyOf(ages);
+    }
+
+    boolean contains(Identifier id) {
+        return ages.containsKey(id) || retired.contains(id);
+    }
+
+    Long seed(Identifier id) {
+        return ages.get(id);
+    }
+
+    PortBiomePlan biomePlan(Identifier id) {
+        PortBiomePlan plan = biomePlans.get(id);
+        if (plan != null) return plan;
+        Identifier oldBiome = biomeOverrides.get(id);
+        return oldBiome == null ? null : new PortBiomePlan(PortBiomePlan.Distribution.SINGLE, List.of(oldBiome));
+    }
+
+    PortAgeTerrain terrain(Identifier id) {
+        return terrain.getOrDefault(id, PortAgeTerrain.STANDARD);
+    }
+
+    PortRockPlan rocks(Identifier id) { return rocks.get(id); }
+    PortVegetationPlan vegetation(Identifier id) { return vegetation.get(id); }
+    int dungeons(Identifier id) { return dungeons.getOrDefault(id, 0); }
+    PortLakePlan lakes(Identifier id) { return lakes.get(id); }
+    PortTerrainFeaturePlan terrainFeatures(Identifier id) { return terrainFeatures.get(id); }
+    PortLighting lighting(Identifier id) { return lighting.getOrDefault(id, PortLighting.NORMAL); }
+    PortSkyStyle sky(Identifier id) { return sky.getOrDefault(id, PortSkyStyle.OVERWORLD); }
+
+    void add(Identifier id, long seed, PortBiomePlan biomePlan, PortAgeTerrain ageTerrain,
+             PortRockPlan rockPlan, PortVegetationPlan vegetationPlan, int dungeonCount,
+             PortLakePlan lakePlan, PortTerrainFeaturePlan terrainFeaturePlan, PortLighting light, PortSkyStyle skyStyle) {
+        if (contains(id)) {
+            throw new IllegalArgumentException("Age already exists: " + id);
+        }
+        ages.put(id, seed);
+        if (biomePlan != null) biomePlans.put(id, biomePlan);
+        if (ageTerrain != PortAgeTerrain.STANDARD) terrain.put(id, ageTerrain);
+        if (rockPlan != null) rocks.put(id, rockPlan);
+        if (vegetationPlan != null) vegetation.put(id, vegetationPlan);
+        if (dungeonCount > 0) dungeons.put(id, dungeonCount);
+        if (lakePlan != null) lakes.put(id, lakePlan);
+        if (terrainFeaturePlan != null) terrainFeatures.put(id, terrainFeaturePlan);
+        if (light != PortLighting.NORMAL) lighting.put(id, light);
+        if (skyStyle != PortSkyStyle.OVERWORLD) sky.put(id, skyStyle);
+        setDirty();
+    }
+
+    void retire(Identifier id) {
+        if (ages.remove(id) == null) throw new IllegalArgumentException("Age not indexed: " + id);
+        biomeOverrides.remove(id);
+        biomePlans.remove(id);
+        terrain.remove(id);
+        rocks.remove(id);
+        vegetation.remove(id);
+        dungeons.remove(id);
+        lakes.remove(id);
+        terrainFeatures.remove(id);
+        lighting.remove(id);
+        sky.remove(id);
+        retired.add(id);
+        setDirty();
+    }
+
+    void restoreAfterFailedRetirement(Identifier id, long seed, PortBiomePlan biomePlan,
+                                      PortAgeTerrain ageTerrain, PortRockPlan rockPlan,
+                                      PortVegetationPlan vegetationPlan, int dungeonCount,
+                                      PortLakePlan lakePlan, PortTerrainFeaturePlan terrainFeaturePlan, PortLighting light,
+                                      PortSkyStyle skyStyle) {
+        if (!retired.remove(id)) throw new IllegalStateException("Age is not retired: " + id);
+        ages.put(id, seed);
+        if (biomePlan != null) biomePlans.put(id, biomePlan);
+        if (ageTerrain != PortAgeTerrain.STANDARD) terrain.put(id, ageTerrain);
+        if (rockPlan != null) rocks.put(id, rockPlan);
+        if (vegetationPlan != null) vegetation.put(id, vegetationPlan);
+        if (dungeonCount > 0) dungeons.put(id, dungeonCount);
+        if (lakePlan != null) lakes.put(id, lakePlan);
+        if (terrainFeaturePlan != null) terrainFeatures.put(id, terrainFeaturePlan);
+        if (light != PortLighting.NORMAL) lighting.put(id, light);
+        if (skyStyle != PortSkyStyle.OVERWORLD) sky.put(id, skyStyle);
+        setDirty();
+    }
+
+    void reseed(Identifier id, long seed) {
+        if (!ages.containsKey(id)) throw new IllegalArgumentException("Age not indexed: " + id);
+        ages.put(id, seed);
+        setDirty();
+    }
+}

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

@@ -0,0 +1,816 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.brigadier.arguments.LongArgumentType;
+import com.mojang.brigadier.arguments.IntegerArgumentType;
+import com.mojang.brigadier.arguments.StringArgumentType;
+import com.mojang.brigadier.context.CommandContext;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.LinkBookTarget;
+import net.minecraft.commands.Commands;
+import net.minecraft.commands.CommandSourceStack;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.util.Prediction;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.world.level.block.Blocks;
+import net.neoforged.neoforge.event.RegisterCommandsEvent;
+import net.neoforged.fml.ModList;
+import java.util.Map;
+import java.util.TreeMap;
+import java.util.Locale;
+
+/** Operator-only backend and synchronized-travel probes, not normal book behavior. */
+public final class PortAgeCommands {
+    private PortAgeCommands() {
+    }
+
+    public static void register(RegisterCommandsEvent event) {
+        event.getDispatcher().register(Commands.literal("rivencraft_port")
+                .requires(Commands.hasPermission(Commands.LEVEL_ADMINS))
+                .then(Commands.literal("compat")
+                        .executes(context -> {
+                            StringBuilder mods = new StringBuilder("Optional mods: ");
+                            for (String id : new String[]{"jei", "terrablender", "biomesoplenty",
+                                    "sereneseasons", "glitchcore", "ruins", "create",
+                                    "ponder", "immersive_portals_core"}) {
+                                if (mods.length() > "Optional mods: ".length()) mods.append(", ");
+                                mods.append(id).append('=').append(ModList.get().isLoaded(id));
+                            }
+                            context.getSource().sendSuccess(() -> Component.literal(mods.toString()), false);
+                            Map<String, Integer> biomeCounts = new TreeMap<>();
+                            context.getSource().getServer().registryAccess()
+                                    .lookupOrThrow(Registries.BIOME).listElementIds()
+                                    .forEach(key -> biomeCounts.merge(key.identifier().getNamespace(), 1, Integer::sum));
+                            context.getSource().sendSuccess(() -> Component.literal(
+                                    "Registered biomes by namespace: " + biomeCounts), false);
+                            return 1;
+                        }))
+                .then(Commands.literal("link")
+                        .then(Commands.literal("book")
+                                .executes(context -> {
+                                    ServerPlayer player = context.getSource().getPlayerOrException();
+                                    ItemStack book = new ItemStack(Rivencraft.LINKING_BOOK.get());
+                                    LinkBookTarget target = LinkBookTarget.at(player);
+                                    book.set(Rivencraft.LINK_BOOK_TARGET.get(), target);
+                                    book.set(DataComponents.CUSTOM_NAME, Component.literal(
+                                            "Link to " + target.dimension()));
+                                    if (!player.getInventory().add(book)) player.drop(book, false, Prediction.SERVER_ONLY);
+                                    context.getSource().sendSuccess(() -> Component.literal(
+                                            "Granted Linking Book bound to " + target.dimension() + " at "
+                                                    + player.blockPosition()), false);
+                                    return 1;
+                                })))
+                .then(Commands.literal("age")
+                        .then(Commands.literal("create_sky")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .then(Commands.argument("sky", StringArgumentType.word())
+                                                        .then(Commands.argument("lighting", StringArgumentType.word())
+                                                                .then(Commands.argument("terrain", StringArgumentType.word())
+                                                                        .executes(PortAgeCommands::createSkyAge)))))))
+                        .then(Commands.literal("sky_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeSky)))
+                        .then(Commands.literal("environment_probe")
+                                .then(Commands.argument("seed", LongArgumentType.longArg())
+                                        .then(Commands.argument("terrain", StringArgumentType.word())
+                                                .executes(PortAgeCommands::probeEnvironment))))
+                        .then(Commands.literal("create_lighting")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .then(Commands.argument("mode", StringArgumentType.word())
+                                                        .suggests((context, builder) -> net.minecraft.commands.SharedSuggestionProvider.suggest(
+                                                                java.util.Arrays.stream(PortLighting.values())
+                                                                        .map(mode -> mode.name().toLowerCase(Locale.ROOT)), builder))
+                                                        .then(Commands.argument("terrain", StringArgumentType.word())
+                                                                .executes(PortAgeCommands::createLightingAge))))))
+                        .then(Commands.literal("lighting_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeLighting)))
+                        .then(Commands.literal("surface_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("x", IntegerArgumentType.integer())
+                                                .then(Commands.argument("z", IntegerArgumentType.integer())
+                                                        .executes(PortAgeCommands::probeSurface)))))
+                        .then(Commands.literal("create_weather")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .then(Commands.argument("mode", StringArgumentType.word())
+                                                        .suggests((context, builder) -> net.minecraft.commands.SharedSuggestionProvider.suggest(
+                                                                java.util.Arrays.stream(PortWeatherMode.values())
+                                                                        .map(mode -> mode.name().toLowerCase(Locale.ROOT)), builder))
+                                                        .executes(PortAgeCommands::createWeatherAge)))))
+                        .then(Commands.literal("weather_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeWeather)))
+                        .then(Commands.literal("create")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.STANDARD))
+                                                .then(Commands.argument("terrain", StringArgumentType.word())
+                                                        .executes(context -> {
+                                                            PortAgeTerrain terrain;
+                                                            try {
+                                                                terrain = PortAgeTerrain.valueOf(StringArgumentType.getString(
+                                                                        context, "terrain").toUpperCase(Locale.ROOT));
+                                                            } catch (IllegalArgumentException exception) {
+                                                                context.getSource().sendFailure(Component.literal(
+                                                                        "Unknown terrain; use standard, amplified, island, cave, flat, or void"));
+                                                                return 0;
+                                                            }
+                                                            return createAge(context, terrain);
+                                                        })))))
+                        .then(Commands.literal("create_multi")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .then(Commands.argument("terrain", StringArgumentType.word())
+                                                        .executes(context -> {
+                                                            PortAgeTerrain terrain;
+                                                            try {
+                                                                terrain = PortAgeTerrain.valueOf(StringArgumentType.getString(
+                                                                        context, "terrain").toUpperCase(Locale.ROOT));
+                                                            } catch (IllegalArgumentException exception) {
+                                                                context.getSource().sendFailure(Component.literal(
+                                                                        "Unknown terrain; use cave, flat, or void"));
+                                                                return 0;
+                                                            }
+                                                            if (terrain != PortAgeTerrain.CAVE
+                                                                    && terrain != PortAgeTerrain.FLAT
+                                                                    && terrain != PortAgeTerrain.VOID) {
+                                                                context.getSource().sendFailure(Component.literal(
+                                                                        "Multi-biome probe supports cave, flat, or void only"));
+                                                                return 0;
+                                                            }
+                                                            return createAge(context, terrain, new PortBiomePlan(
+                                                                    PortBiomePlan.Distribution.TILED,
+                                                                    terrain == PortAgeTerrain.CAVE
+                                                                            ? java.util.List.of(Identifier.withDefaultNamespace("lush_caves"),
+                                                                                    Identifier.withDefaultNamespace("dripstone_caves"))
+                                                                            : java.util.List.of(Identifier.withDefaultNamespace("plains"),
+                                                                                    Identifier.withDefaultNamespace("forest"))));
+                                                        })))))
+                        .then(Commands.literal("create_random")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    long seed = LongArgumentType.getLong(context, "seed");
+                                                    PortRandomAgeSelection.Selection selected = PortRandomAgeSelection.select(
+                                                            context.getSource().getServer(), seed);
+                                                    var environment = PortEnvironmentSelection.resolve(java.util.List.of(), seed, selected.terrain());
+                                                    int created = createAge(context, selected.terrain(), selected.biomes(),
+                                                            null, null, 0, null, null, environment);
+                                                    if (created != 0) context.getSource().sendSuccess(() -> Component.literal(
+                                                            "Random Age plan: terrain=" + selected.terrain()
+                                                                    + " biomes=" + selected.biomes()
+                                                                    + " environment=" + environment), false);
+                                                    return created;
+                                                }))))
+                        .then(Commands.literal("create_rocks")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.FLAT,
+                                                        null, new PortRockPlan(Identifier.withDefaultNamespace("gold_block")))))))
+                        .then(Commands.literal("create_rocks_multi")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.FLAT, null,
+                                                        fourGoldRocks(LongArgumentType.getLong(context, "seed")))))))
+                        .then(Commands.literal("create_rocks_random")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.FLAT, null,
+                                                        net.dnorberg.rivencraft.writing.PortAuthoredWriting.rockPlan(
+                                                                java.util.List.of(Identifier.fromNamespaceAndPath(
+                                                                        Rivencraft.MOD_ID, "feature/rocks")),
+                                                                LongArgumentType.getLong(context, "seed")))))))
+                        .then(Commands.literal("create_vegetation")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.FLAT, null,
+                                                        null, testVegetation())))))
+                        .then(Commands.literal("create_dungeons")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.STANDARD,
+                                                        null, null, null, testDungeons())))))
+                        .then(Commands.literal("create_lakes")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.STANDARD,
+                                                        null, null, null, 0, testLakes(
+                                                                LongArgumentType.getLong(context, "seed"), false))))))
+                        .then(Commands.literal("create_lakes_random")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> createAge(context, PortAgeTerrain.STANDARD,
+                                                        null, null, null, 0, testLakes(
+                                                                LongArgumentType.getLong(context, "seed"), true))))))
+                        .then(Commands.literal("create_islands")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .then(Commands.argument("terrain", StringArgumentType.word())
+                                                        .executes(context -> createIslandAge(context, false))))))
+                        .then(Commands.literal("create_islands_random")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .then(Commands.argument("terrain", StringArgumentType.word())
+                                                        .executes(context -> createIslandAge(context, true))))))
+                        .then(Commands.literal("list")
+                                .executes(context -> {
+                                    var ages = RuntimeAgeBackend.savedAges(context.getSource().getServer());
+                                    context.getSource().sendSuccess(() -> Component.literal(
+                                            "Saved prototype Ages: " + ages), false);
+                                    return ages.size();
+                                }))
+                        .then(Commands.literal("retire")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            String name = StringArgumentType.getString(context, "name");
+                                            Identifier id = Identifier.fromNamespaceAndPath(
+                                                    Rivencraft.MOD_ID, "age/" + name);
+                                            try {
+                                                RuntimeAgeBackend.retire(context.getSource().getServer(), id);
+                                            } catch (IllegalArgumentException | IllegalStateException exception) {
+                                                context.getSource().sendFailure(Component.literal(exception.getMessage()));
+                                                return 0;
+                                            }
+                                            context.getSource().sendSuccess(() -> Component.literal(
+                                                    "Retired " + id + "; exact Age data archived"), true);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("unload")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            Identifier id = ageId(context);
+                                            try {
+                                                RuntimeAgeBackend.unload(context.getSource().getServer(), id);
+                                            } catch (IllegalArgumentException | IllegalStateException exception) {
+                                                context.getSource().sendFailure(Component.literal(exception.getMessage()));
+                                                return 0;
+                                            }
+                                            context.getSource().sendSuccess(() -> Component.literal("Unloaded " + id), true);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("reload")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            Identifier id = ageId(context);
+                                            try {
+                                                RuntimeAgeBackend.reload(context.getSource().getServer(), id);
+                                            } catch (IllegalArgumentException | IllegalStateException exception) {
+                                                context.getSource().sendFailure(Component.literal(exception.getMessage()));
+                                                return 0;
+                                            }
+                                            context.getSource().sendSuccess(() -> Component.literal("Reloaded " + id), true);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("reseed")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("seed", LongArgumentType.longArg())
+                                                .executes(context -> {
+                                                    Identifier id = ageId(context);
+                                                    long seed = LongArgumentType.getLong(context, "seed");
+                                                    try {
+                                                        RuntimeAgeBackend.reseed(context.getSource().getServer(), id, seed);
+                                                    } catch (IllegalArgumentException | IllegalStateException exception) {
+                                                        context.getSource().sendFailure(Component.literal(exception.getMessage()));
+                                                        return 0;
+                                                    }
+                                                    context.getSource().sendSuccess(() -> Component.literal(
+                                                            "Reseeded " + id + " to " + seed + " for future chunks"), true);
+                                                    return 1;
+                                                }))))
+                        .then(Commands.literal("enter")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            ServerPlayer player = context.getSource().getPlayerOrException();
+                                            Identifier id = ageId(context);
+                                            String failure = PortAgeTravel.enter(player, id);
+                                            if (failure != null) {
+                                                context.getSource().sendFailure(Component.literal(failure));
+                                                return 0;
+                                            }
+                                            context.getSource().sendSuccess(() -> Component.literal(
+                                                    "Entered " + id + " after Age catalog acknowledgement"), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("book")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> {
+                                            ServerPlayer player = context.getSource().getPlayerOrException();
+                                            Identifier id = ageId(context);
+                                            if (!RuntimeAgeBackend.savedAges(context.getSource().getServer()).containsKey(id)) {
+                                                context.getSource().sendFailure(Component.literal("Age not active: " + id));
+                                                return 0;
+                                            }
+                                            ItemStack book = new ItemStack(Rivencraft.DESCRIPTIVE_BOOK.get());
+                                            book.set(Rivencraft.AGE_BOOK_ID.get(), id);
+                                            book.set(DataComponents.CUSTOM_NAME, Component.literal(
+                                                    StringArgumentType.getString(context, "name")));
+                                            if (!player.getInventory().add(book)) player.drop(book, false, Prediction.SERVER_ONLY);
+                                            context.getSource().sendSuccess(() -> Component.literal(
+                                                    "Granted bound Descriptive Book for " + id), false);
+                                            return 1;
+                                        })))
+                        .then(Commands.literal("sample")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(context -> sampleAge(context, 0))
+                                        .then(Commands.argument("chunkOffset", IntegerArgumentType.integer(0))
+                                                .executes(context -> sampleAge(context,
+                                                        IntegerArgumentType.getInteger(context, "chunkOffset"))))))
+                        .then(Commands.literal("rocks_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeRocks)))
+                        .then(Commands.literal("vegetation_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeVegetation)))
+                        .then(Commands.literal("dungeons_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeDungeons)))
+                        .then(Commands.literal("lakes_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeLakes)))
+                        .then(Commands.literal("islands_probe")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .executes(PortAgeCommands::probeIslands)))
+                        .then(Commands.literal("biome")
+                                .then(Commands.argument("name", StringArgumentType.word())
+                                        .then(Commands.argument("x", IntegerArgumentType.integer())
+                                                .then(Commands.argument("z", IntegerArgumentType.integer())
+                                                        .executes(PortAgeCommands::sampleBiome)))))));
+    }
+
+    private static int createSkyAge(CommandContext<CommandSourceStack> context) {
+        try {
+            PortSkyStyle sky = PortSkyStyle.valueOf(StringArgumentType.getString(context, "sky").toUpperCase(Locale.ROOT));
+            PortLighting lighting = PortLighting.valueOf(StringArgumentType.getString(context, "lighting").toUpperCase(Locale.ROOT));
+            PortAgeTerrain terrain = PortAgeTerrain.valueOf(StringArgumentType.getString(context, "terrain").toUpperCase(Locale.ROOT));
+            var pages = java.util.List.of(
+                    Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "sky/" + sky.name().toLowerCase(Locale.ROOT)),
+                    Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "lighting/" + lighting.name().toLowerCase(Locale.ROOT)),
+                    Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "terrain/" + terrain.name().toLowerCase(Locale.ROOT)),
+                    Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "weather/off"));
+            var server = context.getSource().getServer();
+            var biomes = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(pages, server.registryAccess());
+            RuntimeAgeBackend.create(server, ageId(context), LongArgumentType.getLong(context, "seed"),
+                    biomes, terrain, null, null, 0, null, null, PortWeatherMode.OFF, lighting, sky);
+            return probeSky(context);
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            context.getSource().sendFailure(Component.literal(exception.getMessage()));
+            return 0;
+        }
+    }
+
+    private static int probeSky(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        var server = context.getSource().getServer();
+        var level = server.getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + id));
+            return 0;
+        }
+        var type = level.dimensionType();
+        context.getSource().sendSuccess(() -> Component.literal("Sky probe " + id
+                + " type=" + level.dimensionTypeRegistration().unwrapKey().orElseThrow().identifier()
+                + " skybox=" + type.skybox() + " skylight=" + type.hasSkyLight() + " ambient=" + type.ambientLight()
+                + " fog=" + level.environmentAttributes().getValue(net.minecraft.world.attribute.EnvironmentAttributes.FOG_COLOR,
+                        new net.minecraft.core.BlockPos(0, 80, 0))
+                + " ceiling=" + type.hasCeiling() + " scale=" + type.coordinateScale()
+                + " minY=" + type.minY() + " height=" + type.height() + " dragon=" + type.hasEnderDragonFight()), false);
+        return 1;
+    }
+
+    private static int probeEnvironment(CommandContext<CommandSourceStack> context) {
+        try {
+            long seed = LongArgumentType.getLong(context, "seed");
+            PortAgeTerrain terrain = PortAgeTerrain.valueOf(
+                    StringArgumentType.getString(context, "terrain").toUpperCase(Locale.ROOT));
+            var selected = PortEnvironmentSelection.resolve(java.util.List.of(), seed, terrain);
+            var explicitPages = java.util.List.of(
+                    Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "weather/storm"),
+                    Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "lighting/bright"));
+            var explicit = PortEnvironmentSelection.resolve(explicitPages, seed, terrain);
+            var weatherOnly = PortEnvironmentSelection.resolve(java.util.List.of(explicitPages.get(0)), seed, terrain);
+            var lightingOnly = PortEnvironmentSelection.resolve(java.util.List.of(explicitPages.get(1)), seed, terrain);
+            if (!selected.equals(PortEnvironmentSelection.resolve(java.util.List.of(), seed, terrain))
+                    || explicit.lighting() != PortLighting.BRIGHT
+                    || explicit.weather() != (terrain == PortAgeTerrain.CAVE ? PortWeatherMode.OFF : PortWeatherMode.STORM)
+                    || weatherOnly.lighting() != selected.lighting() || lightingOnly.weather() != selected.weather())
+                throw new IllegalStateException("Environment selection invariant failed");
+            context.getSource().sendSuccess(() -> Component.literal("Environment probe seed=" + seed
+                    + " terrain=" + terrain + " selected=" + selected + " explicit=" + explicit
+                    + " deterministic=true"), false);
+            return 1;
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            context.getSource().sendFailure(Component.literal(exception.getMessage()));
+            return 0;
+        }
+    }
+
+    private static int createLightingAge(CommandContext<CommandSourceStack> context) {
+        try {
+            PortLighting mode = PortLighting.valueOf(
+                    StringArgumentType.getString(context, "mode").toUpperCase(Locale.ROOT));
+            PortAgeTerrain terrain = PortAgeTerrain.valueOf(
+                    StringArgumentType.getString(context, "terrain").toUpperCase(Locale.ROOT));
+            var pages = java.util.List.of(
+                    Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "lighting/" + mode.name().toLowerCase(Locale.ROOT)),
+                    Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "terrain/" + terrain.name().toLowerCase(Locale.ROOT)));
+            var server = context.getSource().getServer();
+            var biomePlan = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(pages, server.registryAccess());
+            RuntimeAgeBackend.create(server, ageId(context), LongArgumentType.getLong(context, "seed"),
+                    biomePlan, terrain, null, null, 0, null, null, PortWeatherMode.NORMAL, mode);
+            return probeLighting(context);
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            context.getSource().sendFailure(Component.literal(exception.getMessage()));
+            return 0;
+        }
+    }
+
+    private static int probeLighting(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        var server = context.getSource().getServer();
+        ServerLevel level = server.getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + id));
+            return 0;
+        }
+        context.getSource().sendSuccess(() -> Component.literal("Lighting probe " + id
+                + " type=" + level.dimensionTypeRegistration().unwrapKey().orElseThrow().identifier()
+                + " skylight=" + level.dimensionType().hasSkyLight()
+                + " ambient=" + level.dimensionType().ambientLight()
+                + " undergroundBrightness=" + level.getMaxLocalRawBrightness(
+                        new net.minecraft.core.BlockPos(0, level.getMinY() + 2, 0))
+                + " vanillaDarkEnough=" + net.minecraft.world.entity.monster.Monster.isDarkEnoughToSpawn(
+                        level, new net.minecraft.core.BlockPos(0, level.getMinY() + 2, 0),
+                        net.minecraft.util.RandomSource.create(0))
+                + " overworldSkylight=" + server.overworld().dimensionType().hasSkyLight()
+                + " overworldAmbient=" + server.overworld().dimensionType().ambientLight()), false);
+        return 1;
+    }
+
+    private static int probeSurface(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + id));
+            return 0;
+        }
+        int x = IntegerArgumentType.getInteger(context, "x");
+        int z = IntegerArgumentType.getInteger(context, "z");
+        var obstruction = PortAgeTravel.highestObstruction(level, x, z);
+        var landing = PortAgeTravel.findSurfaceLanding(level, x, z);
+        context.getSource().sendSuccess(() -> Component.literal("Surface probe " + id
+                + " highest=" + obstruction + " landing=" + landing), false);
+        return landing == null ? 0 : 1;
+    }
+
+    private static int createWeatherAge(CommandContext<CommandSourceStack> context) {
+        try {
+            PortWeatherMode mode = PortWeatherMode.valueOf(
+                    StringArgumentType.getString(context, "mode").toUpperCase(Locale.ROOT));
+            Identifier id = ageId(context);
+            var server = context.getSource().getServer();
+            // Exercise the Binder's page compiler too, not just direct backend creation.
+            var pages = java.util.List.of(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID,
+                    "weather/" + mode.name().toLowerCase(Locale.ROOT)));
+            var biomePlan = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                    pages, server.registryAccess());
+            RuntimeAgeBackend.create(server, id,
+                    LongArgumentType.getLong(context, "seed"), biomePlan, PortAgeTerrain.FLAT,
+                    null, null, 0, null, null, mode);
+            return probeWeather(context);
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            context.getSource().sendFailure(Component.literal(exception.getMessage()));
+            return 0;
+        }
+    }
+
+    private static int probeWeather(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        var server = context.getSource().getServer();
+        ServerLevel loaded = server.getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (!(loaded instanceof PortAgeLevel level)) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + id));
+            return 0;
+        }
+        var weather = level.getWeatherData();
+        context.getSource().sendSuccess(() -> Component.literal("Weather probe " + id
+                + " mode=" + level.weatherMode() + " raining=" + weather.isRaining()
+                + " thundering=" + weather.isThundering() + " rainTicks=" + weather.getRainTime()
+                + " thunderTicks=" + weather.getThunderTime()
+                + " independent=" + (weather != server.getWeatherData())
+                + " overworldRaining=" + server.getWeatherData().isRaining()
+                + " overworldThundering=" + server.getWeatherData().isThundering()), false);
+        return 1;
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context, PortAgeTerrain terrain) {
+        return createAge(context, terrain, null);
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context,
+                                 PortAgeTerrain terrain, PortBiomePlan biomePlan) {
+        return createAge(context, terrain, biomePlan, null);
+    }
+
+    private static int probeRocks(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null || !(level.getChunkSource().getGenerator() instanceof PortFeatureChunkGenerator features)
+                || features.rocks() == null) {
+            context.getSource().sendFailure(Component.literal("Age has no loaded Rocks generator: " + id));
+            return 0;
+        }
+        var materials = features.rocks().materials().stream()
+                .map(net.minecraft.core.registries.BuiltInRegistries.BLOCK::getValue).toList();
+        int count = 0;
+        for (int x = 0; x < 64; x++) for (int z = 0; z < 64; z++) {
+            int y = level.getHeight(Heightmap.Types.MOTION_BLOCKING, x, z) - 1;
+            var state = level.getBlockState(new net.minecraft.core.BlockPos(x, y, z));
+            if (materials.stream().anyMatch(state::is)) count++;
+        }
+        int placed = count;
+        context.getSource().sendSuccess(() -> Component.literal(
+                "Rocks probe " + id + " materials=" + features.rocks().materials() + " count=" + placed), false);
+        return placed;
+    }
+
+    private static int probeVegetation(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + id));
+            return 0;
+        }
+        int flowers = 0;
+        int logs = 0;
+        for (int x = 0; x < 64; x++) for (int z = 0; z < 64; z++) {
+            for (int y = 4; y < 32; y++) {
+                var state = level.getBlockState(new net.minecraft.core.BlockPos(x, y, z));
+                if (state.is(BlockTags.FLOWERS)) flowers++;
+                if (state.is(BlockTags.LOGS)) logs++;
+            }
+        }
+        int flowerCount = flowers;
+        int logCount = logs;
+        context.getSource().sendSuccess(() -> Component.literal(
+                "Vegetation probe " + id + " flowers=" + flowerCount + " logs=" + logCount), false);
+        return flowerCount + logCount;
+    }
+
+    private static PortVegetationPlan testVegetation() {
+        java.util.List<Identifier> pages = new java.util.ArrayList<>();
+        for (int i = 0; i < 10; i++) {
+            pages.add(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/flowers"));
+            pages.add(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/trees"));
+            pages.add(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/huge_trees"));
+        }
+        return net.dnorberg.rivencraft.writing.PortAuthoredWriting.vegetationPlan(pages);
+    }
+
+    private static int testDungeons() {
+        Identifier page = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/dungeons");
+        return net.dnorberg.rivencraft.writing.PortAuthoredWriting.dungeonCount(
+                java.util.Collections.nCopies(8, page));
+    }
+
+    private static int probeDungeons(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null || !(level.getChunkSource().getGenerator() instanceof PortFeatureChunkGenerator features)) {
+            context.getSource().sendFailure(Component.literal("Age has no loaded feature generator: " + id));
+            return 0;
+        }
+        int count = features.dungeons();
+        int spawners = 0;
+        for (int chunkX = 0; chunkX < 4; chunkX++) for (int chunkZ = 0; chunkZ < 4; chunkZ++) {
+            var chunk = level.getChunk(chunkX, chunkZ);
+            for (var pos : chunk.getBlockEntitiesPos()) {
+                if (chunk.getBlockState(pos).is(Blocks.SPAWNER)) spawners++;
+            }
+        }
+        int placed = spawners;
+        context.getSource().sendSuccess(() -> Component.literal(
+                "Dungeons probe " + id + " pages=" + count + " spawners=" + placed), false);
+        return placed;
+    }
+
+    private static PortLakePlan testLakes(long seed, boolean randomFluids) {
+        java.util.List<Identifier> pages = new java.util.ArrayList<>();
+        for (int i = 0; i < 8; i++) {
+            for (String kind : java.util.List.of("surface_lakes", "deep_lakes", "lava_lakes")) {
+                if (!randomFluids) pages.add(net.dnorberg.rivencraft.writing.PortRegistryPages.blockPageId(
+                        Identifier.withDefaultNamespace("water")));
+                pages.add(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/" + kind));
+            }
+        }
+        return net.dnorberg.rivencraft.writing.PortAuthoredWriting.lakePlan(pages, seed);
+    }
+
+    private static int probeLakes(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + id));
+            return 0;
+        }
+        PortLakePlan lakes = level.getChunkSource().getGenerator() instanceof PortFeatureChunkGenerator features
+                ? features.lakes() : null;
+        // Finish neighboring features before counting, since lake bowls can
+        // cross a chunk boundary. Include underground lakes in the probe.
+        for (int x = -1; x <= 4; x++) for (int z = -1; z <= 4; z++) level.getChunk(x, z);
+        int[] fluids = new int[2];
+        for (int x = 0; x < 4; x++) for (int z = 0; z < 4; z++) {
+            level.getChunk(x, z).findBlocks(state -> state.is(Blocks.WATER) || state.is(Blocks.LAVA),
+                    (pos, state) -> fluids[state.is(Blocks.WATER) ? 0 : 1]++);
+        }
+        int waterCount = fluids[0];
+        int lavaCount = fluids[1];
+        context.getSource().sendSuccess(() -> Component.literal(
+                "Lakes probe " + id + " pages=" + (lakes == null ? 0 : lakes.choices().size())
+                        + " fluids=" + (lakes == null ? java.util.List.of() : lakes.choices().stream()
+                                .map(PortLakePlan.Choice::fluid).distinct().toList())
+                        + " plan=" + (lakes == null ? 0 : lakes.choices().hashCode())
+                        + " water=" + waterCount + " lava=" + lavaCount), false);
+        return waterCount + lavaCount;
+    }
+
+    private static int createIslandAge(CommandContext<CommandSourceStack> context, boolean randomMaterials) {
+        PortAgeTerrain terrain;
+        try {
+            terrain = PortAgeTerrain.valueOf(StringArgumentType.getString(context, "terrain").toUpperCase(Locale.ROOT));
+        } catch (IllegalArgumentException exception) {
+            context.getSource().sendFailure(Component.literal("Unknown island test terrain"));
+            return 0;
+        }
+        java.util.List<Identifier> pages = new java.util.ArrayList<>();
+        pages.add(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "terrain/" + terrain.name().toLowerCase(Locale.ROOT)));
+        pages.add(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "biome/forest"));
+        for (int i = 0; i < 4; i++) {
+            if (!randomMaterials) pages.add(net.dnorberg.rivencraft.writing.PortRegistryPages.blockPageId(
+                    Identifier.withDefaultNamespace("gold_block")));
+            pages.add(PortTerrainFeaturePlan.FLOATING_ISLANDS);
+        }
+        try {
+            long seed = LongArgumentType.getLong(context, "seed");
+            var biomes = net.dnorberg.rivencraft.writing.PortAuthoredWriting.biomePlan(
+                    pages, context.getSource().getServer().registryAccess());
+            var features = net.dnorberg.rivencraft.writing.PortAuthoredWriting.terrainFeaturePlan(pages, seed);
+            return createAge(context, terrain, biomes, null, null, 0, null, features);
+        } catch (IllegalArgumentException exception) {
+            context.getSource().sendFailure(Component.literal(exception.getMessage()));
+            return 0;
+        }
+    }
+
+    private static int probeIslands(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null || !(level.getChunkSource().getGenerator() instanceof PortFeatureChunkGenerator features)
+                || features.terrainFeatures() == null) {
+            context.getSource().sendFailure(Component.literal("Age has no loaded island generator: " + id));
+            return 0;
+        }
+        var choices = features.terrainFeatures().choices();
+        var materials = choices.stream().map(PortTerrainFeaturePlan.Choice::material).distinct().toList();
+        var blocks = materials.stream().map(net.minecraft.core.registries.BuiltInRegistries.BLOCK::getValue).toList();
+        for (int x = -1; x <= 4; x++) for (int z = -1; z <= 4; z++) level.getChunk(x, z);
+        int[] count = {0};
+        long[] fingerprint = {0};
+        for (int x = 0; x < 4; x++) for (int z = 0; z < 4; z++) {
+            level.getChunk(x, z).findBlocks(state -> !state.isAir(), (pos, state) -> {
+                if (pos.getY() < 128 || pos.getY() >= 240) return;
+                if (blocks.stream().anyMatch(state::is)) count[0]++;
+                fingerprint[0] += pos.asLong() * 0x9E3779B97F4A7C15L ^ state.toString().hashCode();
+            });
+        }
+        context.getSource().sendSuccess(() -> Component.literal(
+                "Islands probe " + id + " pages=" + choices.size() + " materials=" + materials
+                        + " count=" + count[0] + " fingerprint=" + fingerprint[0]), false);
+        return count[0];
+    }
+
+    /** Exercise the actual ordered writing parser, not only the generator codec. */
+    private static PortRockPlan fourGoldRocks(long seed) {
+        Identifier block = net.dnorberg.rivencraft.writing.PortRegistryPages.blockPageId(
+                Identifier.withDefaultNamespace("gold_block"));
+        Identifier feature = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/rocks");
+        java.util.List<Identifier> pages = new java.util.ArrayList<>();
+        for (int i = 0; i < 4; i++) {
+            pages.add(block);
+            pages.add(feature);
+        }
+        return net.dnorberg.rivencraft.writing.PortAuthoredWriting.rockPlan(pages, seed);
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context,
+                                 PortAgeTerrain terrain, PortBiomePlan biomePlan, PortRockPlan rockPlan) {
+        return createAge(context, terrain, biomePlan, rockPlan, null);
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context,
+                                 PortAgeTerrain terrain, PortBiomePlan biomePlan,
+                                 PortRockPlan rockPlan, PortVegetationPlan vegetationPlan) {
+        return createAge(context, terrain, biomePlan, rockPlan, vegetationPlan, 0);
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context,
+                                 PortAgeTerrain terrain, PortBiomePlan biomePlan,
+                                 PortRockPlan rockPlan, PortVegetationPlan vegetationPlan,
+                                 int dungeons) {
+        return createAge(context, terrain, biomePlan, rockPlan, vegetationPlan, dungeons, null);
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context,
+                                 PortAgeTerrain terrain, PortBiomePlan biomePlan,
+                                 PortRockPlan rockPlan, PortVegetationPlan vegetationPlan,
+                                 int dungeons, PortLakePlan lakes) {
+        return createAge(context, terrain, biomePlan, rockPlan, vegetationPlan, dungeons, lakes, null);
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context,
+                                 PortAgeTerrain terrain, PortBiomePlan biomePlan,
+                                 PortRockPlan rockPlan, PortVegetationPlan vegetationPlan,
+                                 int dungeons, PortLakePlan lakes, PortTerrainFeaturePlan terrainFeatures) {
+        return createAge(context, terrain, biomePlan, rockPlan, vegetationPlan, dungeons, lakes, terrainFeatures,
+                new PortEnvironmentSelection(PortWeatherMode.NORMAL, PortLighting.NORMAL));
+    }
+
+    private static int createAge(CommandContext<CommandSourceStack> context,
+                                 PortAgeTerrain terrain, PortBiomePlan biomePlan,
+                                 PortRockPlan rockPlan, PortVegetationPlan vegetationPlan,
+                                 int dungeons, PortLakePlan lakes, PortTerrainFeaturePlan terrainFeatures,
+                                 PortEnvironmentSelection environment) {
+        String name = StringArgumentType.getString(context, "name");
+        Identifier id = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age/" + name);
+        long seed = LongArgumentType.getLong(context, "seed");
+        ServerLevel level;
+        try {
+            level = RuntimeAgeBackend.create(context.getSource().getServer(), id, seed, biomePlan,
+                    terrain, rockPlan, vegetationPlan, dungeons, lakes, terrainFeatures,
+                    environment.weather(), environment.lighting());
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            context.getSource().sendFailure(Component.literal(exception.getMessage()));
+            return 0;
+        }
+        context.getSource().sendSuccess(() -> Component.literal(
+                "Created " + id + " with seed " + level.getSeed() + " terrain=" + terrain), true);
+        return 1;
+    }
+
+    private static int sampleAge(com.mojang.brigadier.context.CommandContext<net.minecraft.commands.CommandSourceStack> context,
+                                 int chunkOffset) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(
+                ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + id));
+            return 0;
+        }
+        int fingerprint = 1;
+        for (int x = 0; x < 2; x++) {
+            for (int z = 0; z < 2; z++) {
+                int chunkX = chunkOffset + x * 4;
+                int chunkZ = chunkOffset + z * 4;
+                level.getChunk(chunkX, chunkZ);
+                fingerprint = 31 * fingerprint + level.getHeight(
+                        Heightmap.Types.WORLD_SURFACE, chunkX * 16, chunkZ * 16);
+            }
+        }
+        int result = fingerprint;
+        context.getSource().sendSuccess(() -> Component.literal(
+                id + " seed=" + level.getSeed() + " chunkOffset=" + chunkOffset + " terrain=" + result), false);
+        return 1;
+    }
+
+    private static int sampleBiome(CommandContext<CommandSourceStack> context) {
+        Identifier id = ageId(context);
+        ServerLevel level = context.getSource().getServer().getLevel(ResourceKey.create(Registries.DIMENSION, id));
+        if (level == null) {
+            context.getSource().sendFailure(Component.literal("Age not loaded: " + id));
+            return 0;
+        }
+        int x = IntegerArgumentType.getInteger(context, "x");
+        int z = IntegerArgumentType.getInteger(context, "z");
+        level.getChunk(x >> 4, z >> 4);
+        Identifier biome = level.getBiome(new net.minecraft.core.BlockPos(x, 4, z))
+                .unwrapKey().orElseThrow().identifier();
+        context.getSource().sendSuccess(() -> Component.literal(
+                id + " biome at " + x + "," + z + "=" + biome), false);
+        return 1;
+    }
+
+    private static Identifier ageId(com.mojang.brigadier.context.CommandContext<net.minecraft.commands.CommandSourceStack> context) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID,
+                "age/" + StringArgumentType.getString(context, "name"));
+    }
+
+}

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

@@ -0,0 +1,48 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.List;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.saveddata.WeatherData;
+import net.minecraft.world.level.storage.DerivedLevelData;
+
+/** Runtime Age with independent native weather, rather than 26.3's shared server cycle. */
+final class PortAgeLevel extends ServerLevel {
+    private final WeatherData ageWeather;
+    private final PortWeatherSettings weatherSettings;
+    private final boolean cave;
+
+    PortAgeLevel(MinecraftServer server, ResourceKey<Level> key, LevelStem stem,
+                 long biomeZoomSeed, PortAgeTerrain terrain) {
+        super(server, server.executor, server.storageSource,
+                new DerivedLevelData(server.getWorldData(), server.getWorldData().overworldData()),
+                key, stem, server.getWorldData().isDebugWorld(), biomeZoomSeed, List.of(), false);
+        ageWeather = getDataStorage().computeIfAbsent(WeatherData.TYPE);
+        weatherSettings = getDataStorage().computeIfAbsent(PortWeatherSettings.TYPE);
+        cave = terrain == PortAgeTerrain.CAVE;
+        PortAgeWeather.apply(this);
+        // The base constructor initializes visual levels from server weather.
+        // Replace them before publishing this Age or sending its join packets.
+        setRainLevel(ageWeather.isRaining() ? 1.0F : 0.0F);
+        setThunderLevel(ageWeather.isThundering() ? 1.0F : 0.0F);
+    }
+
+    @Override
+    public WeatherData getWeatherData() {
+        // The base constructor may query weather before our fields are initialized.
+        return ageWeather == null ? super.getWeatherData() : ageWeather;
+    }
+
+    PortWeatherMode weatherMode() { return cave ? PortWeatherMode.OFF : weatherSettings.mode(); }
+
+    void configureWeather(PortWeatherMode mode) {
+        weatherSettings.setMode(mode);
+        PortAgeWeather.apply(this);
+        setRainLevel(ageWeather.isRaining() ? 1.0F : 0.0F);
+        setThunderLevel(ageWeather.isThundering() ? 1.0F : 0.0F);
+        getDataStorage().saveAndJoin();
+    }
+}

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

@@ -0,0 +1,11 @@
+package net.dnorberg.rivencraft.age;
+
+/** Terrain variants currently backed by 26.3 vanilla noise settings. */
+public enum PortAgeTerrain {
+    STANDARD,
+    AMPLIFIED,
+    ISLAND,
+    CAVE,
+    FLAT,
+    VOID
+}

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

@@ -0,0 +1,165 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.Set;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.levelgen.Heightmap;
+
+/** Shared, server-authoritative landing for the 26.3 book and operator probe. */
+public final class PortAgeTravel {
+    private PortAgeTravel() {
+    }
+
+    public static String enter(ServerPlayer player, Identifier id) {
+        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";
+        }
+        boolean fissure = target.getChunkSource().getGenerator() instanceof PortFeatureChunkGenerator features
+                && features.terrainFeatures() != null && features.terrainFeatures().starFissures();
+        BlockPos landing = fissure ? PortStarFissureFeature.savedSpawn(target) : null;
+        if (landing != null) landing = isCaveTerrain(target)
+                ? findFootedDestination(target, landing).orElse(null)
+                : findSurfaceLanding(target, landing.getX(), landing.getZ());
+        if (landing == null) landing = findLanding(target);
+        if (landing == null) return "No safe test landing available; remaining in source dimension";
+        if (fissure) PortStarFissureFeature.generateOnce(target, landing, isCaveTerrain(target));
+        boolean moved = player.teleportTo(target, landing.getX() + 0.5, landing.getY(), landing.getZ() + 0.5,
+                Set.of(), player.getYRot(), player.getXRot(), true);
+        return moved ? null : "Teleportation failed; remaining in source dimension";
+    }
+
+    private static BlockPos findLanding(ServerLevel target) {
+        if (isCaveTerrain(target)) {
+            // The cave roof is not a valid arrival surface. Search down from
+            // Legacy's Y=64 start, then construct the normal safety platform
+            // at that height only when no footed opening can be found.
+            for (int radius = 0; radius <= 16; radius++) {
+                for (int x = -radius; x <= radius; x++) {
+                    for (int z = -radius; z <= radius; z++) {
+                        if (Math.max(Math.abs(x), Math.abs(z)) != radius) continue;
+                        for (int y = Math.min(64, target.getMaxY() - 2); y > target.getMinY(); y--) {
+                            BlockPos foot = new BlockPos(x, y, z);
+                            if (hasFooting(target, foot)) return foot;
+                        }
+                    }
+                }
+            }
+            return makePlatform(target, new BlockPos(0, 64, 0));
+        }
+        BlockPos surface = findSurfaceLanding(target, 0, 0);
+        if (surface != null) return surface;
+        // Only build above the actual highest obstruction, never in a pocket
+        // 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));
+    }
+
+    static BlockPos findSurfaceLanding(ServerLevel target, int originX, int originZ) {
+        for (int radius = 0; radius <= 16; radius++) {
+            for (int x = -radius; x <= radius; x++) {
+                for (int z = -radius; z <= radius; z++) {
+                    if (Math.max(Math.abs(x), Math.abs(z)) != radius) continue;
+                    BlockPos floor = highestObstruction(target, originX + x, originZ + z);
+                    if (floor != null && hasFooting(target, floor.above())) return floor.above();
+                }
+            }
+        }
+        return null;
+    }
+
+    /** First obstructing surface seen from the sky; never continue through a roof or liquid. */
+    static BlockPos highestObstruction(ServerLevel level, int x, int z) {
+        var chunk = level.getChunk(x >> 4, z >> 4);
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos(x, level.getMaxY() - 1, z);
+        for (int y = level.getMaxY() - 1; y >= level.getMinY(); y--) {
+            pos.setY(y);
+            var state = chunk.getBlockState(pos);
+            if (!state.isAir() && (!state.getFluidState().isEmpty()
+                    || state.is(net.minecraft.tags.BlockTags.LEAVES)
+                    || !state.getCollisionShape(level, pos).isEmpty())) return pos.immutable();
+        }
+        return null;
+    }
+
+    private static boolean isCaveTerrain(ServerLevel target) {
+        var generator = target.getChunkSource().getGenerator();
+        if (generator instanceof PortFeatureChunkGenerator features) generator = features.base();
+        return generator instanceof net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator noise
+                && noise.generatorSettings().value().noiseSettings().equals(target.registryAccess()
+                .lookupOrThrow(Registries.NOISE_SETTINGS)
+                .getOrThrow(net.minecraft.world.level.levelgen.NoiseGeneratorSettings.CAVES)
+                .value().noiseSettings());
+    }
+
+    private static BlockPos makePlatform(ServerLevel target, BlockPos foot) {
+        if (foot.getY() <= target.getMinY() || foot.getY() + 2 >= target.getMaxY()) return null;
+        // A carved pocket inside a flooded cave immediately refills. Refuse
+        // that landing instead of placing the player in submerged spawn space.
+        if (!target.getFluidState(foot).isEmpty() || !target.getFluidState(foot.above()).isEmpty()) return null;
+        for (Direction direction : Direction.Plane.HORIZONTAL) {
+            if (!target.getFluidState(foot.relative(direction)).isEmpty()
+                    || !target.getFluidState(foot.above().relative(direction)).isEmpty()) return null;
+        }
+        for (int x = -1; x <= 1; x++) {
+            for (int z = -1; z <= 1; z++) {
+                target.setBlock(foot.offset(x, -1, z), Rivencraft.CRYSTAL_BLOCK.get().defaultBlockState(), 3);
+            }
+        }
+        target.setBlock(foot, Blocks.AIR.defaultBlockState(), 3);
+        target.setBlock(foot.above(), Blocks.AIR.defaultBlockState(), 3);
+        return foot;
+    }
+
+    private static boolean hasFooting(ServerLevel target, BlockPos foot) {
+        if (foot.getY() <= target.getMinY() || foot.getY() + 1 >= target.getMaxY()
+                || !target.getWorldBorder().isWithinBounds(foot)) return false;
+        BlockPos floor = foot.below();
+        var floorState = target.getBlockState(floor);
+        return (floorState.isFaceSturdy(target, floor, Direction.UP)
+                || floorState.is(net.minecraft.tags.BlockTags.LEAVES))
+                && floorState.getFluidState().isEmpty()
+                && target.getFluidState(foot).isEmpty()
+                && target.getFluidState(foot.above()).isEmpty()
+                && passable(target, foot) && passable(target, foot.above());
+    }
+
+    private static boolean passable(ServerLevel level, BlockPos pos) {
+        var state = level.getBlockState(pos);
+        return state.getCollisionShape(level, pos).isEmpty() || state.is(net.minecraft.tags.BlockTags.LEAVES);
+    }
+
+    /** Same local-then-surface safe-return search used by 1.21.1 fissures. */
+    public static java.util.Optional<BlockPos> findFootedDestination(ServerLevel level, BlockPos origin) {
+        var local = BlockPos.betweenClosedStream(origin.offset(-4, -2, -4), origin.offset(4, 2, 4))
+                .map(BlockPos::immutable).sorted(java.util.Comparator.comparingDouble(pos -> pos.distSqr(origin)))
+                .filter(pos -> level.isInWorldBounds(pos) && level.getWorldBorder().isWithinBounds(pos))
+                .filter(pos -> hasFooting(level, pos)).findFirst();
+        if (local.isPresent()) return local;
+        for (int radius = 1; radius <= 64; radius++) {
+            final int ring = radius;
+            var found = BlockPos.betweenClosedStream(origin.offset(-ring, 0, -ring), origin.offset(ring, 0, ring))
+                    .filter(pos -> Math.max(Math.abs(pos.getX() - origin.getX()), Math.abs(pos.getZ() - origin.getZ())) == ring)
+                    .map(BlockPos::immutable)
+                    .flatMap(pos -> {
+                        BlockPos surface = new BlockPos(pos.getX(),
+                                level.getHeight(Heightmap.Types.MOTION_BLOCKING, pos.getX(), pos.getZ()), pos.getZ());
+                        return java.util.stream.Stream.of(surface, surface.above(), surface.below(),
+                                surface.above(2), surface.below(2));
+                    })
+                    .filter(pos -> level.isInWorldBounds(pos) && level.getWorldBorder().isWithinBounds(pos))
+                    .filter(pos -> hasFooting(level, pos)).findFirst();
+            if (found.isPresent()) return found;
+        }
+        return java.util.Optional.empty();
+    }
+}

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

@@ -0,0 +1,52 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.Map;
+import java.util.WeakHashMap;
+import net.minecraft.world.level.saveddata.WeatherData;
+import net.neoforged.neoforge.event.tick.LevelTickEvent;
+
+/** 1.21.1 weather policies, applied before the independent native Age cycle advances. */
+public final class PortAgeWeather {
+    private static final Map<PortAgeLevel, Integer> STATES = new WeakHashMap<>();
+
+    private PortAgeWeather() {}
+
+    public static void onLevelTickPre(LevelTickEvent.Pre event) {
+        if (event.getLevel() instanceof PortAgeLevel level) apply(level);
+    }
+
+    static void apply(PortAgeLevel level) {
+        PortWeatherMode mode = level.weatherMode();
+        if (mode == PortWeatherMode.NORMAL) {
+            STATES.remove(level);
+            return;
+        }
+        WeatherData weather = level.getWeatherData();
+        if (mode == PortWeatherMode.FAST || mode == PortWeatherMode.SLOW) {
+            int state = (weather.isRaining() ? 1 : 0) | (weather.isThundering() ? 2 : 0);
+            Integer previous = STATES.put(level, state);
+            if (previous != null && previous == state) return;
+            // Keep persisted timers on reload; rescale only when a cycle changes.
+            if (previous == null && weather.getRainTime() > 0) return;
+            int scale = mode == PortWeatherMode.FAST ? 1 : 4;
+            int duration = 6000 * scale + level.getRandom().nextInt(
+                    (weather.isRaining() ? 6000 : 84000) * scale);
+            set(weather, duration, weather.isRaining(), weather.isThundering());
+        } else {
+            STATES.remove(level);
+            boolean rain = mode != PortWeatherMode.OFF;
+            boolean thunder = mode == PortWeatherMode.STORM;
+            if (weather.isRaining() != rain || weather.isThundering() != thunder
+                    || weather.getRainTime() < 200 || weather.getThunderTime() < 200
+                    || weather.getClearWeatherTime() != 0) set(weather, 6000, rain, thunder);
+        }
+    }
+
+    private static void set(WeatherData data, int duration, boolean rain, boolean thunder) {
+        data.setClearWeatherTime(0);
+        data.setRainTime(duration);
+        data.setThunderTime(duration);
+        data.setRaining(rain);
+        data.setThundering(thunder);
+    }
+}

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

@@ -0,0 +1,25 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.List;
+import net.minecraft.resources.Identifier;
+
+/** Frozen authored biome choice; repeated entries retain their selection weight. */
+public record PortBiomePlan(Distribution distribution, List<Identifier> biomes) {
+    public enum Distribution { NATIVE, SINGLE, TILED, GRID, TINY, SMALL, MEDIUM, LARGE, HUGE }
+
+    public static final Codec<PortBiomePlan> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Codec.STRING.xmap(Distribution::valueOf, Distribution::name).fieldOf("distribution")
+                    .forGetter(PortBiomePlan::distribution),
+            Identifier.CODEC.listOf().fieldOf("biomes").forGetter(PortBiomePlan::biomes)
+    ).apply(instance, PortBiomePlan::new));
+
+    public PortBiomePlan {
+        biomes = List.copyOf(biomes);
+        if (distribution == Distribution.NATIVE && !biomes.isEmpty()
+                || distribution == Distribution.SINGLE && biomes.size() != 1
+                || distribution != Distribution.NATIVE && distribution != Distribution.SINGLE && biomes.size() < 2)
+            throw new IllegalArgumentException("Invalid authored biome distribution");
+    }
+}

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

@@ -0,0 +1,78 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.QuartPos;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.tags.BiomeTags;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.chunk.CarvingMask;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.LegacyRandomSource;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.WorldGenerationContext;
+import net.minecraft.world.level.levelgen.WorldgenRandom;
+import net.minecraft.world.level.levelgen.carver.WorldCarver;
+
+/** Authored Caves/Ravines, independent of the terrain page, with 1.21.1 source seeds. */
+public final class PortCarverPages {
+    public static final Identifier CAVES = Identifier.fromNamespaceAndPath("rivencraft", "feature/caves");
+    public static final Identifier RAVINES = Identifier.fromNamespaceAndPath("rivencraft", "feature/ravines");
+    private static final long CAVE_SALT = 0x4341564553464541L;
+    private static final long RAVINE_SALT = 0x524156494E45534CL;
+
+    private PortCarverPages() {}
+
+    public static boolean supports(Identifier page) { return CAVES.equals(page) || RAVINES.equals(page); }
+
+    public static void validateCounts(List<Identifier> pages) {
+        Map<Identifier, Integer> counts = new HashMap<>();
+        for (Identifier page : pages) if (!supports(page) || counts.merge(page, 1, Integer::sum) > 32)
+            throw new IllegalArgumentException("Carver plan requires Caves/Ravines pages, at most 32 per type");
+    }
+
+    public static void validateRegistry(List<Identifier> pages, HolderLookup.Provider registries) {
+        if (pages.stream().noneMatch(PortCarverPages::supports)) return;
+        var carvers = registries.lookupOrThrow(Registries.CARVER);
+        for (String name : pages.contains(CAVES) ? List.of("cave", "nether_cave", "canyon") : List.of("canyon")) {
+            if (name.equals("canyon") && !pages.contains(RAVINES)) continue;
+            carvers.get(ResourceKey.create(Registries.CARVER, Identifier.withDefaultNamespace(name)))
+                    .orElseThrow(() -> new IllegalArgumentException("Missing authored carver minecraft:" + name));
+        }
+    }
+
+    public static void carve(ChunkGenerator generator, ChunkAccess chunk, RandomState randomState,
+                             HolderLookup.Provider registries, List<Identifier> pages, long seed, CarvingMask mask) {
+        if (pages.isEmpty()) return;
+        var registry = registries.lookupOrThrow(Registries.CARVER);
+        var biomes = generator.getBiomeSource().createUncachedResolver(randomState);
+        var context = new WorldGenerationContext(generator, chunk.getHeightAccessorForGeneration());
+        var random = new WorldgenRandom(new LegacyRandomSource(0L));
+        ChunkPos target = chunk.getPos();
+        // 1.21.1 repeats identical seeds for duplicate Caves/Ravines pages.
+        // Their union is identical; avoid replaying the same mask up to 32 times.
+        for (Identifier page : pages.stream().distinct().toList()) {
+            boolean ravine = page.equals(RAVINES);
+            WorldCarver overworld = registry.getOrThrow(ResourceKey.create(Registries.CARVER,
+                    Identifier.withDefaultNamespace(ravine ? "canyon" : "cave"))).value();
+            WorldCarver nether = ravine ? null : registry.getOrThrow(ResourceKey.create(Registries.CARVER,
+                    Identifier.withDefaultNamespace("nether_cave"))).value();
+            for (int dx = -8; dx <= 8; dx++) {
+                for (int dz = -8; dz <= 8; dz++) {
+                    ChunkPos source = new ChunkPos(target.x() + dx, target.z() + dz);
+                    boolean isNether = biomes.getNoiseBiome(QuartPos.fromBlock(source.getMinBlockX()), 0,
+                            QuartPos.fromBlock(source.getMinBlockZ())).is(BiomeTags.IS_NETHER);
+                    if (ravine && isNether) continue;
+                    WorldCarver carver = isNether ? nether : overworld;
+                    random.setLargeFeatureSeed(seed ^ (ravine ? RAVINE_SALT : CAVE_SALT), source.x(), source.z());
+                    if (carver.isStartChunk(random)) carver.carve(context, random, target, source, mask);
+                }
+            }
+        }
+    }
+}

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

@@ -0,0 +1,78 @@
+package net.dnorberg.rivencraft.age;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.AmethystClusterBlock;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.Heightmap;
+
+/** 26.3 port of the 1.21.1 surface crystal mound with budding hearts and seeded buds. */
+final class PortCrystalFormationsFeature {
+    private static final long SALT = 0x4352595354414C53L;
+    private static final int CHANCE = 15;
+
+    private PortCrystalFormationsFeature() {}
+
+    record Site(int x, int z, long seed) {}
+
+    static Site site(long ageSeed, ChunkPos chunk, int occurrence) {
+        long seed = mix(ageSeed ^ SALT ^ (long) chunk.x() * 341873128712L
+                ^ (long) chunk.z() * 132897987541L ^ (long) occurrence * 0x9E3779B97F4A7C15L);
+        RandomSource random = RandomSource.create(seed);
+        if (random.nextInt(CHANCE) != 0) return null;
+        return new Site(chunk.getMinBlockX() + 5 + random.nextInt(6),
+                chunk.getMinBlockZ() + 5 + random.nextInt(6), seed);
+    }
+
+    static void generate(WorldGenLevel level, ChunkAccess chunk, long ageSeed, int occurrence) {
+        Site site = site(ageSeed, chunk.getPos(), occurrence);
+        if (site == null) return;
+        RandomSource random = RandomSource.create(site.seed() ^ 0x42554444494E474CL);
+        int y = level.getHeight(Heightmap.Types.WORLD_SURFACE_WG, site.x(), site.z());
+        if (y <= level.getMinY() + 1 || y + 4 >= level.getMaxY()) return;
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        for (int dx = -1; dx <= 1; dx++) {
+            for (int dz = -1; dz <= 1; dz++) {
+                int x = site.x() + dx;
+                int z = site.z() + dz;
+                if (Math.abs(level.getHeight(Heightmap.Types.WORLD_SURFACE_WG, x, z) - y) > 1) return;
+                BlockState floor = level.getBlockState(pos.set(x, y - 1, z));
+                if (!floor.isFaceSturdy(level, pos, Direction.UP) || !floor.getFluidState().isEmpty()
+                        || floor.hasBlockEntity()) return;
+                for (int h = 0; h < 4; h++) {
+                    BlockState existing = level.getBlockState(pos.set(x, y + h, z));
+                    if (!existing.isAir() && !existing.canBeReplaced()) return;
+                }
+            }
+        }
+        for (int dx = -1; dx <= 1; dx++) {
+            for (int dz = -1; dz <= 1; dz++) {
+                boolean center = dx == 0 && dz == 0;
+                int height = center ? 3 : random.nextInt(3) == 0 ? 2 : 1;
+                for (int h = 0; h < height; h++) {
+                    boolean budding = h == height - 1 && (center || random.nextBoolean());
+                    level.setBlock(pos.set(site.x() + dx, y + h, site.z() + dz),
+                            budding ? Rivencraft.BUDDING_CRYSTAL.get().defaultBlockState()
+                                    : Rivencraft.CRYSTAL_BLOCK.get().defaultBlockState(), 2);
+                }
+                if (level.getBlockState(pos.set(site.x() + dx, y + height - 1, site.z() + dz))
+                        .is(Rivencraft.BUDDING_CRYSTAL) && random.nextBoolean()) {
+                    level.setBlock(pos.set(site.x() + dx, y + height, site.z() + dz),
+                            Rivencraft.SMALL_CRYSTAL_BUD.get().defaultBlockState()
+                                    .setValue(AmethystClusterBlock.FACING, Direction.UP), 2);
+                }
+            }
+        }
+    }
+
+    private static long mix(long value) {
+        value = (value ^ value >>> 30) * 0xBF58476D1CE4E5B9L;
+        value = (value ^ value >>> 27) * 0x94D049BB133111EBL;
+        return value ^ value >>> 31;
+    }
+}

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

@@ -0,0 +1,90 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.TreeMap;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.tags.TagKey;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.feature.AbstractOreFeature;
+import net.minecraft.world.level.levelgen.placement.FeaturePlacer;
+import net.minecraft.world.level.levelgen.placement.PlacedFeature;
+import net.neoforged.neoforge.common.Tags;
+
+/** Replays each eligible biome ore placement once per page, matching Rivencraft 1.21.1. */
+public final class PortDenseOres {
+    public static final TagKey<PlacedFeature> EXTRA_ORES = TagKey.create(Registries.PLACED_FEATURE,
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "dense_ores"));
+
+    private PortDenseOres() {}
+
+    public static boolean hasOres(Holder<Biome> biome) {
+        return oreFeatures(biome).anyMatch(PortDenseOres::isOre);
+    }
+
+    /** Modern ore features carry their targets directly rather than an OreConfiguration. */
+    public static boolean isOre(Holder<PlacedFeature> holder) {
+        if (holder.is(EXTRA_ORES)) return true;
+        if (!(holder.value().feature().value() instanceof AbstractOreFeature ore)) return false;
+        return ore.targetStates().stream().anyMatch(target -> isOreBlock(target.state()));
+    }
+
+    private static boolean isOreBlock(BlockState state) {
+        if (state.is(Tags.BlockItems.ORES.block())) return true;
+        String path = BuiltInRegistries.BLOCK.getKey(state.getBlock()).getPath();
+        return path.endsWith("_ore") || path.contains("_ore_");
+    }
+
+    private static java.util.stream.Stream<Holder<PlacedFeature>> oreFeatures(Holder<Biome> biome) {
+        return biome.value().getGenerationSettings().features().stream().flatMap(HolderSet::stream);
+    }
+
+    public static void place(WorldGenLevel level, ChunkAccess chunk, ChunkGenerator generator,
+                             long ageSeed, int count) {
+        if (count == 0) return;
+        Set<Holder<Biome>> biomes = new HashSet<>();
+        ChunkPos.rangeClosed(chunk.getPos(), 1).forEach(pos -> {
+            for (var section : level.getChunk(pos.x(), pos.z()).getSections())
+                section.getBiomes().getAll(biomes::add);
+        });
+        biomes.retainAll(generator.getBiomeSource().possibleBiomes());
+        // Collect once per chunk, not once per repeated page. Stable registry-ID
+        // order and per-occurrence seeds retain the 1.21.1 placement sequence.
+        Map<Identifier, PlacedFeature> ores = new TreeMap<>();
+        for (Holder<Biome> biome : biomes) {
+            oreFeatures(biome).filter(PortDenseOres::isOre).forEach(feature ->
+                    feature.unwrapKey().ifPresent(key -> ores.putIfAbsent(key.identifier(), feature.value())));
+        }
+        BlockPos origin = new BlockPos(chunk.getPos().getMinBlockX(), level.getMinY(),
+                chunk.getPos().getMinBlockZ());
+        FeaturePlacer placer = new FeaturePlacer(level, generator);
+        for (int occurrence = 0; occurrence < count; occurrence++) {
+            for (var entry : ores.entrySet()) {
+                long seed = mix(ageSeed ^ (long) origin.getX() * 341873128712L
+                        ^ (long) origin.getZ() * 132897987541L
+                        ^ (long) entry.getKey().hashCode() * 0x9E3779B97F4A7C15L
+                        ^ (long) occurrence * 0xD1B54A32D192ED03L);
+                placer.placeWithBiomeCheck(entry.getValue(), RandomSource.create(seed), origin);
+            }
+        }
+    }
+
+    private static long mix(long value) {
+        value = (value ^ value >>> 30) * 0xBF58476D1CE4E5B9L;
+        value = (value ^ value >>> 27) * 0x94D049BB133111EBL;
+        return value ^ value >>> 31;
+    }
+}

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

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

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

@@ -0,0 +1,290 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.MapCodec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.List;
+import java.util.Optional;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.PortRegistryPages;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.core.registries.BuiltInRegistries;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.tags.TagKey;
+import net.minecraft.tags.BiomeTags;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.NoiseColumn;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeManager;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.blending.Blender;
+import net.minecraft.world.level.levelgen.densityfunction.SamplerContext;
+import net.minecraft.world.level.levelgen.blockpredicates.BlockPredicate;
+import net.minecraft.world.level.levelgen.feature.BlockBlobFeature;
+import net.minecraft.world.level.levelgen.feature.LakeFeature;
+import net.minecraft.world.level.levelgen.feature.stateproviders.BlockStateProvider;
+import net.minecraft.world.level.levelgen.placement.BiomeFilter;
+import net.minecraft.world.level.levelgen.placement.PlacedFeature;
+import net.minecraft.world.level.levelgen.placement.RarityFilter;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import com.mojang.datafixers.util.Pair;
+import net.minecraft.core.HolderSet;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.block.Block;
+
+/** Delegates terrain generation and applies frozen Age-scoped features. */
+public final class PortFeatureChunkGenerator extends ChunkGenerator {
+    private static final ResourceKey<PlacedFeature> FOREST_ROCK = ResourceKey.create(
+            Registries.PLACED_FEATURE, Identifier.withDefaultNamespace("forest_rock"));
+    private static final ResourceKey<PlacedFeature> DUNGEONS = ResourceKey.create(
+            Registries.PLACED_FEATURE, Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "dungeons"));
+    private static final TagKey<Block> ROCK_GROUND = TagKey.create(
+            Registries.BLOCK, Identifier.withDefaultNamespace("forest_rock_can_place_on"));
+    public static final MapCodec<PortFeatureChunkGenerator> CODEC = RecordCodecBuilder.mapCodec(instance -> instance.group(
+            ChunkGenerator.CODEC.fieldOf("base").forGetter(generator -> generator.base),
+            PortRockPlan.CODEC.optionalFieldOf("rocks").forGetter(generator -> Optional.ofNullable(generator.rocks)),
+            PortVegetationPlan.CODEC.optionalFieldOf("vegetation")
+                    .forGetter(generator -> Optional.ofNullable(generator.vegetation)),
+            com.mojang.serialization.Codec.intRange(0, 32).optionalFieldOf("dungeons", 0)
+                    .forGetter(generator -> generator.dungeons),
+            PortLakePlan.CODEC.optionalFieldOf("lakes")
+                    .forGetter(generator -> Optional.ofNullable(generator.lakes)),
+            PortTerrainFeaturePlan.CODEC.optionalFieldOf("terrain_features")
+                    .forGetter(generator -> Optional.ofNullable(generator.terrainFeatures)),
+            com.mojang.serialization.Codec.LONG.fieldOf("age_seed").forGetter(generator -> generator.ageSeed)
+    ).apply(instance, (base, rocks, vegetation, dungeons, lakes, terrainFeatures, seed) ->
+            new PortFeatureChunkGenerator(base, rocks.orElse(null), vegetation.orElse(null),
+                    dungeons, lakes.orElse(null), terrainFeatures.orElse(null), seed)));
+
+    private final ChunkGenerator base;
+    private final PortRockPlan rocks;
+    private final PortVegetationPlan vegetation;
+    private final int dungeons;
+    private final PortLakePlan lakes;
+    private final PortTerrainFeaturePlan terrainFeatures;
+    private final long ageSeed;
+
+    public PortFeatureChunkGenerator(ChunkGenerator base, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures, long ageSeed) {
+        super(base.getBiomeSource(), base::getBiomeGenerationSettings);
+        this.base = base;
+        this.rocks = rocks;
+        this.vegetation = vegetation;
+        this.dungeons = dungeons;
+        this.lakes = lakes;
+        this.terrainFeatures = terrainFeatures;
+        this.ageSeed = ageSeed;
+    }
+
+    public ChunkGenerator base() { return base; }
+    public PortRockPlan rocks() { return rocks; }
+    public PortVegetationPlan vegetation() { return vegetation; }
+    public int dungeons() { return dungeons; }
+    public PortLakePlan lakes() { return lakes; }
+    public PortTerrainFeaturePlan terrainFeatures() { return terrainFeatures; }
+
+    @Override protected MapCodec<? extends ChunkGenerator> codec() { return CODEC; }
+    @Override public void validate() { base.validate(); }
+    @Override public ChunkPos getOrigin(RandomState random) { return base.getOrigin(random); }
+    @Override public java.util.Optional<Identifier> getTypeNameForDataFixer() { return base.getTypeNameForDataFixer(); }
+    @Override public CompletableFuture<ChunkAccess> createBiomes(RandomState random, Blender blender,
+                                                                  StructureManager structures, ChunkAccess chunk) {
+        return base.createBiomes(random, blender, structures, chunk);
+    }
+    @Override public ChunkGeneratorStructureState createState(HolderLookup<StructureSet> sets,
+                                                               RandomState random, long seed) {
+        if (hasStructurePages()) {
+            var lookup = PortStructurePages.filtered(sets, terrainFeatures.structures(), getBiomeSource());
+            var planning = PortStructurePages.planningBiomes(getBiomeSource(), sets, terrainFeatures.structures());
+            if (base instanceof PortFlatChunkGenerator || base instanceof net.minecraft.world.level.levelgen.FlatLevelSource)
+                return ChunkGeneratorStructureState.createForFlat(random, seed, getOrigin(random), planning,
+                        lookup.listElements().map(holder -> (Holder<StructureSet>) holder));
+            return ChunkGeneratorStructureState.createForNormal(random, seed, getOrigin(random), planning, lookup);
+        }
+        return base.createState(sets, random, seed);
+    }
+
+    private boolean hasStructurePages() {
+        return terrainFeatures != null && !terrainFeatures.structures().isEmpty();
+    }
+    @Override public void createStructures(RegistryAccess registries, ChunkGeneratorStructureState state,
+                                           StructureManager structures, ChunkAccess chunk,
+                                           StructureTemplateManager templates, ResourceKey<Level> dimension) {
+        if (hasStructurePages()) super.createStructures(registries, state, structures, chunk, templates, dimension);
+        else base.createStructures(registries, state, structures, chunk, templates, dimension);
+    }
+    @Override public void createReferences(WorldGenLevel level, StructureManager structures, ChunkAccess chunk) {
+        base.createReferences(level, structures, chunk);
+    }
+    @Override public Pair<BlockPos, Holder<Structure>> findNearestMapStructure(ServerLevel level,
+            HolderSet<Structure> targets, BlockPos origin, int radius, boolean skipKnown) {
+        return base.findNearestMapStructure(level, targets, origin, radius, skipKnown);
+    }
+    @Override public void spawnOriginalMobs(WorldGenRegion level) { base.spawnOriginalMobs(level); }
+    @Override public int getSpawnHeight(LevelHeightAccessor height) { return base.getSpawnHeight(height); }
+    @Override public int getGenDepth() { return base.getGenDepth(); }
+    @Override public int getSeaLevel() { return base.getSeaLevel(); }
+    @Override public int getMinY() { return base.getMinY(); }
+    @Override public CompletableFuture<ChunkAccess> buildTerrain(ChunkAccess chunk, Blender blender,
+            RandomState random, StructureManager structures, BiomeManager biomes,
+            WorldGenRegion carverBiomeRegion, Set<Holder<Biome>> possibleBiomes) {
+        CompletableFuture<ChunkAccess> built = base.buildTerrain(
+                chunk, blender, random, structures, biomes, carverBiomeRegion, possibleBiomes);
+        if (terrainFeatures == null || !terrainFeatures.skylands() && terrainFeatures.choices().isEmpty()) return built;
+        return built.thenApply(result -> {
+            // Match 1.21.1: filter the base terrain once, then add the authored
+            // solid volumes, irrespective of the Skylands page's written position.
+            if (terrainFeatures.skylands()) PortSkylandsFeature.filter(result, ageSeed);
+            java.util.Map<Identifier, Integer> occurrences = new java.util.HashMap<>();
+            for (PortTerrainFeaturePlan.Choice choice : terrainFeatures.choices()) {
+                if (PortTerrainFeaturePlan.isSurface(choice.page())) continue;
+                int occurrence = occurrences.merge(choice.page(), 1, Integer::sum) - 1;
+                long featureSeed = ageSeed ^ (long) occurrence * 0x9E3779B97F4A7C15L;
+                BlockState material = BuiltInRegistries.BLOCK.getValue(choice.material()).defaultBlockState();
+                if (choice.page().equals(PortTerrainFeaturePlan.FLOATING_ISLANDS))
+                    PortFloatingIslandFeature.generate(result, featureSeed, material);
+                else if (choice.page().equals(PortTerrainFeaturePlan.TENDRILS))
+                    PortTendrilFeature.generate(result, featureSeed, material);
+                else if (choice.page().equals(PortTerrainFeaturePlan.SPHERES))
+                    PortSpheresFeature.generate(result, featureSeed, material);
+                else throw new IllegalStateException("Unsupported terrain feature: " + choice.page());
+            }
+            return result;
+        });
+    }
+    @Override public int getBaseHeight(int x, int z, Heightmap.Types type,
+                                       LevelHeightAccessor height, RandomState random) {
+        return base.getBaseHeight(x, z, type, height, random);
+    }
+    @Override public NoiseColumn getBaseColumn(int x, int z, LevelHeightAccessor height, RandomState random) {
+        return base.getBaseColumn(x, z, height, random);
+    }
+    @Override public void addDebugScreenInfo(List<String> info, RandomState random,
+                                              BlockPos pos, SamplerContext context) {
+        base.addDebugScreenInfo(info, random, pos, context);
+    }
+    @Override public void refreshFeaturesPerStep() {
+        base.refreshFeaturesPerStep();
+        super.refreshFeaturesPerStep();
+    }
+
+    @Override public void applyBiomeDecoration(WorldGenLevel level, ChunkAccess chunk,
+                                                StructureManager structures) {
+        base.applyBiomeDecoration(level, chunk, structures);
+        if (terrainFeatures != null) {
+            PortDenseOres.place(level, chunk, this, ageSeed, terrainFeatures.denseOres());
+            int spikeOccurrence = 0;
+            int obeliskOccurrence = 0;
+            int crystalOccurrence = 0;
+            for (PortTerrainFeaturePlan.Choice choice : terrainFeatures.choices()) {
+                if (!PortTerrainFeaturePlan.isSurface(choice.page())) continue;
+                BlockState material = BuiltInRegistries.BLOCK.getValue(choice.material()).defaultBlockState();
+                if (choice.page().equals(PortTerrainFeaturePlan.SPIKES))
+                    PortSpikesFeature.generate(level, chunk, ageSeed, material, spikeOccurrence++);
+                else if (choice.page().equals(PortTerrainFeaturePlan.OBELISKS))
+                    PortObelisksFeature.generate(level, chunk, ageSeed, material, obeliskOccurrence++);
+                else if (choice.page().equals(PortTerrainFeaturePlan.CRYSTAL_FORMATIONS))
+                    PortCrystalFormationsFeature.generate(level, chunk, ageSeed, crystalOccurrence++);
+                else throw new IllegalStateException("Unsupported surface feature: " + choice.page());
+            }
+        }
+        ChunkPos chunkPos = chunk.getPos();
+        long chunkSeed = ageSeed ^ (long) chunkPos.x() * 341873128712L
+                ^ (long) chunkPos.z() * 132897987541L;
+        BlockPos origin = new BlockPos(chunkPos.getMinBlockX(), level.getMinY(), chunkPos.getMinBlockZ());
+        if (rocks != null) {
+            PlacedFeature vanilla = level.registryAccess().lookupOrThrow(Registries.PLACED_FEATURE)
+                    .getOrThrow(FOREST_ROCK).value();
+            var placement = vanilla.placement().stream()
+                    .filter(modifier -> !(modifier instanceof BiomeFilter)).toList();
+            for (int occurrence = 0; occurrence < rocks.materials().size(); occurrence++) {
+                RandomSource random = RandomSource.create(chunkSeed
+                        ^ (long) occurrence * 0xD1B54A32D192ED03L);
+                BlockState material = BuiltInRegistries.BLOCK.getValue(
+                        rocks.materials().get(occurrence)).defaultBlockState();
+                PlacedFeature authored = new PlacedFeature(Holder.direct(new BlockBlobFeature(
+                        material, BlockPredicate.matchesTag(ROCK_GROUND))), placement);
+                authored.place(level, this, random, origin);
+            }
+        }
+        if (dungeons > 0) {
+            PlacedFeature authored = level.registryAccess().lookupOrThrow(Registries.PLACED_FEATURE)
+                    .getOrThrow(DUNGEONS).value();
+            for (int occurrence = 0; occurrence < dungeons; occurrence++) {
+                RandomSource random = RandomSource.create(chunkSeed
+                        ^ 0x44554E47454F4E53L ^ (long) occurrence * 0xD1B54A32D192ED03L);
+                authored.place(level, this, random, origin);
+            }
+        }
+        if (lakes != null) {
+            var registry = level.registryAccess().lookupOrThrow(Registries.PLACED_FEATURE);
+            java.util.Map<PortLakePlan.Choice, Integer> occurrences = new java.util.HashMap<>();
+            for (PortLakePlan.Choice choice : lakes.choices()) {
+                PlacedFeature vanilla = registry.getOrThrow(ResourceKey.create(
+                        Registries.PLACED_FEATURE, PortLakePlan.placedFeature(choice.page()))).value();
+                if (!(vanilla.feature().value() instanceof LakeFeature lake))
+                    throw new IllegalStateException("Lake placement no longer references a LakeFeature: " + choice.page());
+                BlockState fluid = BuiltInRegistries.BLOCK.getValue(choice.fluid()).defaultBlockState();
+                LakeFeature feature = new LakeFeature(BlockStateProvider.holderOf(fluid), lake.barrier(),
+                        lake.canPlaceFeature(), lake.canReplaceWithAirOrFluid(), lake.canReplaceWithBarrier());
+                PlacedFeature authored = new PlacedFeature(Holder.direct(feature), vanilla.placement().stream()
+                        .filter(modifier -> !(modifier instanceof BiomeFilter))
+                        .map(modifier -> !PortLakePlan.isDeep(choice.page()) && modifier instanceof RarityFilter
+                                ? RarityFilter.onAverageOnceEvery(12) : modifier)
+                        .toList());
+                int occurrence = occurrences.merge(choice, 1, Integer::sum) - 1;
+                RandomSource random = RandomSource.create(chunkSeed
+                        ^ (long) choice.hashCode() * 0x9E3779B97F4A7C15L
+                        ^ (long) occurrence * 0xD1B54A32D192ED03L);
+                authored.place(level, this, random, origin);
+            }
+        }
+        if (vegetation != null) {
+            int surface = chunk.getHeight(Heightmap.Types.WORLD_SURFACE_WG, 8, 8);
+            Holder<Biome> biome = level.getBiome(new BlockPos(
+                    chunkPos.getMinBlockX() + 8, surface, chunkPos.getMinBlockZ() + 8));
+            boolean surfaceBiome = !biome.is(BiomeTags.IS_END) && !PortRegistryPages.isCaveBiome(biome);
+            var registry = level.registryAccess().lookupOrThrow(Registries.PLACED_FEATURE);
+            List<BlockPos> mushroomHosts = null;
+            for (int occurrence = 0; occurrence < vegetation.pages().size(); occurrence++) {
+                Identifier page = vegetation.pages().get(occurrence);
+                RandomSource random = RandomSource.create(chunkSeed
+                        ^ (long) page.hashCode() * 0x9E3779B97F4A7C15L
+                        ^ (long) occurrence * 0xD1B54A32D192ED03L);
+                if (page.equals(PortVegetationPlan.SHELF_MUSHROOMS)) {
+                    if (mushroomHosts == null) mushroomHosts = PortShelfMushrooms.findHosts(chunk);
+                    PortShelfMushrooms.decorate(level, chunk, mushroomHosts, random);
+                    continue;
+                }
+                if (!surfaceBiome) continue;
+                Identifier placedId = PortVegetationPlan.placedFeature(page);
+                PlacedFeature vanilla = registry.getOrThrow(
+                        ResourceKey.create(Registries.PLACED_FEATURE, placedId)).value();
+                PlacedFeature authored = new PlacedFeature(vanilla.feature(), vanilla.placement().stream()
+                        .filter(modifier -> !(modifier instanceof BiomeFilter)).toList());
+                authored.place(level, this, random, origin);
+                if (PortVegetationPlan.addsLogs(page)) mushroomHosts = null;
+            }
+        }
+    }
+}

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

@@ -0,0 +1,142 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.MapCodec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.List;
+import java.util.Set;
+import java.util.concurrent.CompletableFuture;
+import java.util.stream.Stream;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.HolderSet;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.NoiseColumn;
+import net.minecraft.world.level.StructureManager;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeGenerationSettings;
+import net.minecraft.world.level.biome.BiomeManager;
+import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.chunk.ChunkGeneratorStructureState;
+import net.minecraft.world.level.levelgen.GenerationStep;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.blending.Blender;
+import net.minecraft.world.level.levelgen.densityfunction.SamplerContext;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
+import net.minecraft.world.level.levelgen.placement.PlacedFeature;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import net.neoforged.neoforge.common.util.MemoizedFunction;
+import org.jspecify.annotations.Nullable;
+
+/** Flat layers with the authored biome distribution used by 1.21.1 Ages. */
+public final class PortFlatChunkGenerator extends ChunkGenerator {
+    public static final MapCodec<PortFlatChunkGenerator> CODEC = RecordCodecBuilder.mapCodec(instance -> instance.group(
+            BiomeSource.CODEC.fieldOf("biome_source").forGetter(generator -> generator.biomeSource),
+            FlatLevelGeneratorSettings.CODEC.fieldOf("settings").forGetter(PortFlatChunkGenerator::settings)
+    ).apply(instance, PortFlatChunkGenerator::new));
+
+    private final FlatLevelGeneratorSettings settings;
+    private final MemoizedFunction<Holder<Biome>, BiomeGenerationSettings> generationSettingsGetter;
+
+    public PortFlatChunkGenerator(BiomeSource biomeSource, FlatLevelGeneratorSettings settings) {
+        super(biomeSource, this.generationSettingsGetter = MemoizedFunction.of(
+                biome -> generationSettings(settings, biome)));
+        this.settings = settings;
+    }
+
+    public FlatLevelGeneratorSettings settings() {
+        return settings;
+    }
+
+    private static BiomeGenerationSettings generationSettings(FlatLevelGeneratorSettings settings, Holder<Biome> biome) {
+        // Void biomes still control climate, but must not place terrain features.
+        if (settings.getLayersInfo().isEmpty()) return BiomeGenerationSettings.EMPTY;
+        if (biome.equals(settings.getBiome())) return settings.adjustGenerationSettings(biome);
+        BiomeGenerationSettings.PlainBuilder builder = new BiomeGenerationSettings.PlainBuilder();
+        List<HolderSet<PlacedFeature>> features = biome.value().getGenerationSettings().features();
+        for (int step = 0; step < features.size(); step++) {
+            if (step == GenerationStep.Decoration.UNDERGROUND_STRUCTURES.ordinal()
+                    || step == GenerationStep.Decoration.SURFACE_STRUCTURES.ordinal()) continue;
+            for (Holder<PlacedFeature> feature : features.get(step)) builder.addFeature(step, feature);
+        }
+        return builder.build();
+    }
+
+    @Override
+    protected MapCodec<? extends ChunkGenerator> codec() {
+        return CODEC;
+    }
+
+    @Override
+    public ChunkGeneratorStructureState createState(HolderLookup<StructureSet> structures,
+                                                    RandomState random, long seed) {
+        Stream<Holder<StructureSet>> entries = settings.structureOverrides()
+                .map(HolderSet::stream)
+                .orElseGet(() -> structures.listElements().map(holder -> (Holder<StructureSet>) holder));
+        return ChunkGeneratorStructureState.createForFlat(random, seed, getOrigin(random), biomeSource, entries);
+    }
+
+    @Override
+    public int getSpawnHeight(LevelHeightAccessor height) {
+        return height.getMinY() + Math.min(height.getHeight(), settings.getLayers().size());
+    }
+
+    @Override
+    public CompletableFuture<ChunkAccess> buildTerrain(ChunkAccess chunk, Blender blender,
+            RandomState random, StructureManager structures, BiomeManager biomes,
+            @Nullable WorldGenRegion carverBiomeRegion, Set<Holder<Biome>> possibleBiomes) {
+        List<BlockState> layers = settings.getLayers();
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        Heightmap floor = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.OCEAN_FLOOR_WG);
+        Heightmap surface = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.WORLD_SURFACE_WG);
+        for (int layer = 0; layer < Math.min(chunk.getHeight(), layers.size()); layer++) {
+            BlockState state = layers.get(layer);
+            if (state == null) continue;
+            int y = chunk.getMinY() + layer;
+            for (int x = 0; x < 16; x++) for (int z = 0; z < 16; z++) {
+                chunk.setBlockState(pos.set(x, y, z), state);
+                floor.update(x, y, z, state);
+                surface.update(x, y, z, state);
+            }
+        }
+        return CompletableFuture.completedFuture(chunk);
+    }
+
+    @Override
+    public int getBaseHeight(int x, int z, Heightmap.Types type,
+                             LevelHeightAccessor height, RandomState random) {
+        List<BlockState> layers = settings.getLayers();
+        for (int layer = Math.min(layers.size() - 1, height.getHeight() - 1); layer >= 0; layer--) {
+            BlockState state = layers.get(layer);
+            if (state != null && type.isOpaque().test(state)) return height.getMinY() + layer + 1;
+        }
+        return height.getMinY();
+    }
+
+    @Override
+    public NoiseColumn getBaseColumn(int x, int z, LevelHeightAccessor height, RandomState random) {
+        return new NoiseColumn(height.getMinY(), settings.getLayers().stream().limit(height.getHeight())
+                .map(state -> state == null ? Blocks.AIR.defaultBlockState() : state)
+                .toArray(BlockState[]::new));
+    }
+
+    @Override public void addDebugScreenInfo(List<String> info, RandomState random,
+                                             BlockPos pos, SamplerContext context) { }
+    @Override public void spawnOriginalMobs(WorldGenRegion level) { }
+    @Override public int getMinY() { return 0; }
+    @Override public int getGenDepth() { return 384; }
+    @Override public int getSeaLevel() { return -63; }
+
+    @Override
+    public void refreshFeaturesPerStep() {
+        super.refreshFeaturesPerStep();
+        generationSettingsGetter.clear();
+        settings.updateLayers();
+    }
+}

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

@@ -0,0 +1,83 @@
+package net.dnorberg.rivencraft.age;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.QuartPos;
+import net.minecraft.tags.BiomeTags;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.dnorberg.rivencraft.writing.PortRegistryPages;
+
+/** 1.21.1 floating-island shape adapted to the 26.3 chunk terrain stage. */
+final class PortFloatingIslandFeature {
+    private static final long SALT = 0x464C4F4154494E47L;
+    private static final int SOURCE_RANGE = 3;
+    private static final int CHANCE = 128;
+
+    private PortFloatingIslandFeature() {}
+
+    static void generate(ChunkAccess chunk, long ageSeed, BlockState material) {
+        var target = chunk.getPos();
+        for (int sourceX = target.x() - SOURCE_RANGE; sourceX <= target.x() + SOURCE_RANGE; sourceX++) {
+            for (int sourceZ = target.z() - SOURCE_RANGE; sourceZ <= target.z() + SOURCE_RANGE; sourceZ++) {
+                RandomSource random = RandomSource.create(mix(ageSeed ^ SALT
+                        ^ (long) sourceX * 341873128712L ^ (long) sourceZ * 132897987541L));
+                if (random.nextInt(CHANCE) != 0) continue;
+                int centerX = sourceX * 16 + random.nextInt(16);
+                int centerZ = sourceZ * 16 + random.nextInt(16);
+                int centerY = Math.min(chunk.getMaxY() - 30, 168 + random.nextInt(48));
+                if (centerY < chunk.getMinY() + 24) continue;
+                int radiusX = 24 + random.nextInt(18);
+                int radiusZ = 24 + random.nextInt(18);
+                fill(chunk, ageSeed, material, centerX, centerY, centerZ, radiusX, radiusZ);
+            }
+        }
+    }
+
+    private static void fill(ChunkAccess chunk, long ageSeed, BlockState material,
+                             int centerX, int centerY, int centerZ, int radiusX, int radiusZ) {
+        int originX = chunk.getPos().getMinBlockX();
+        int originZ = chunk.getPos().getMinBlockZ();
+        Heightmap surface = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.WORLD_SURFACE_WG);
+        Heightmap floor = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.OCEAN_FLOOR_WG);
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        for (int localX = 0; localX < 16; localX++) {
+            int worldX = originX + localX;
+            double dx = (worldX - centerX) / (double) radiusX;
+            for (int localZ = 0; localZ < 16; localZ++) {
+                int worldZ = originZ + localZ;
+                double dz = (worldZ - centerZ) / (double) radiusZ;
+                double distance = dx * dx + dz * dz;
+                if (distance >= 1.0) continue;
+                long detail = mix(ageSeed ^ (long) centerX * 341873128712L
+                        ^ (long) centerZ * 132897987541L ^ (long) worldX * 42317861L
+                        ^ (long) worldZ * 374761393L);
+                int top = centerY + (int) Math.round(3 * (1 - distance)) + Math.floorMod(detail, 3) - 1;
+                int depth = Math.max(1, (int) Math.round(3 + 17 * Math.pow(1 - distance, 1.5)));
+                // Biomes are already populated by createBiomes in 26.3, so
+                // sampling this chunk preserves its authored biome distribution.
+                var biome = chunk.getNoiseBiome(QuartPos.fromBlock(worldX), QuartPos.fromBlock(top),
+                        QuartPos.fromBlock(worldZ));
+                BlockState soil = biome.is(BiomeTags.IS_END) || PortRegistryPages.isCaveBiome(biome)
+                        ? material : Blocks.DIRT.defaultBlockState();
+                BlockState cap = soil == material ? material : Blocks.GRASS_BLOCK.defaultBlockState();
+                for (int y = Math.max(top - depth, chunk.getMinY()); y <= top; y++) {
+                    pos.set(worldX, y, worldZ);
+                    if (!chunk.getBlockState(pos).isAir()) continue;
+                    BlockState state = y == top ? cap : y >= top - 3 ? soil : material;
+                    chunk.setBlockState(pos, state);
+                    surface.update(localX, y, localZ, state);
+                    floor.update(localX, y, localZ, state);
+                }
+            }
+        }
+    }
+
+    private static long mix(long value) {
+        value = (value ^ value >>> 30) * 0xBF58476D1CE4E5B9L;
+        value = (value ^ value >>> 27) * 0x94D049BB133111EBL;
+        return value ^ value >>> 31;
+    }
+}

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

@@ -0,0 +1,46 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+
+/** Ordered lake pages with fluid choices frozen when the Age is bound. */
+public record PortLakePlan(List<Choice> choices) {
+    public static final Codec<PortLakePlan> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Choice.CODEC.listOf().fieldOf("choices").forGetter(PortLakePlan::choices)
+    ).apply(instance, PortLakePlan::new));
+
+    public record Choice(Identifier page, Identifier fluid) {
+        public static final Codec<Choice> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+                Identifier.CODEC.fieldOf("page").forGetter(Choice::page),
+                Identifier.CODEC.fieldOf("fluid").forGetter(Choice::fluid)
+        ).apply(instance, Choice::new));
+
+        public Choice {
+            if (!isLake(page) || fluid == null) throw new IllegalArgumentException("Invalid lake choice");
+        }
+    }
+
+    public PortLakePlan {
+        choices = List.copyOf(choices);
+        if (choices.isEmpty() || choices.size() > 32)
+            throw new IllegalArgumentException("Lake plan must contain 1–32 choices");
+    }
+
+    public static boolean isLake(Identifier page) {
+        if (page == null || !page.getNamespace().equals(Rivencraft.MOD_ID)) return false;
+        return switch (page.getPath()) {
+            case "feature/surface_lakes", "feature/deep_lakes", "feature/lava_lakes" -> true;
+            default -> false;
+        };
+    }
+
+    public static boolean isDeep(Identifier page) { return page.getPath().equals("feature/deep_lakes"); }
+
+    public static Identifier placedFeature(Identifier page) {
+        if (!isLake(page)) throw new IllegalArgumentException("Unsupported lake page " + page);
+        return Identifier.withDefaultNamespace(isDeep(page) ? "lake_lava_underground" : "lake_lava_surface");
+    }
+}

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

@@ -0,0 +1,52 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import java.util.Locale;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.Holder;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.world.level.dimension.DimensionType;
+import net.minecraft.world.level.Level;
+
+/** Authored lighting choices using statically registered, client-synchronized types. */
+public enum PortLighting {
+    NORMAL, DARK, BRIGHT;
+
+    public static final Codec<PortLighting> CODEC = Codec.STRING.xmap(
+            name -> valueOf(name.toUpperCase(Locale.ROOT)), mode -> mode.name().toLowerCase(Locale.ROOT));
+
+    public static PortLighting forPage(Identifier page) {
+        if (!page.getNamespace().equals(Rivencraft.MOD_ID)) return null;
+        return switch (page.getPath()) {
+            case "lighting/normal" -> NORMAL;
+            case "lighting/dark" -> DARK;
+            case "lighting/bright" -> BRIGHT;
+            default -> null;
+        };
+    }
+
+    public static boolean isBright(Level level) {
+        return level.dimensionTypeRegistration().unwrapKey().map(key -> {
+            Identifier id = key.identifier();
+            return id.getNamespace().equals(Rivencraft.MOD_ID)
+                    && (id.getPath().equals("age_bright") || id.getPath().equals("age_cave_bright")
+                        || id.getPath().startsWith("age_bright_sky_")
+                        || id.getPath().startsWith("age_cave_bright_sky_"));
+        }).orElse(false);
+    }
+
+    Holder<DimensionType> dimensionType(MinecraftServer server, PortAgeTerrain terrain,
+                                       Holder<DimensionType> overworldType, PortSkyStyle sky) {
+        boolean cave = terrain == PortAgeTerrain.CAVE;
+        if (this == NORMAL && !cave && sky == PortSkyStyle.OVERWORLD) return overworldType;
+        String variant = this == BRIGHT ? (cave ? "age_cave_bright" : "age_bright")
+                : this == DARK || cave ? "age_dark" : "age_normal";
+        if (sky != PortSkyStyle.OVERWORLD) variant += "_sky_" + sky.name().toLowerCase(Locale.ROOT);
+        return server.registryAccess().lookupOrThrow(Registries.DIMENSION_TYPE).getOrThrow(
+                ResourceKey.create(Registries.DIMENSION_TYPE,
+                        Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, variant)));
+    }
+}

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

@@ -0,0 +1,91 @@
+package net.dnorberg.rivencraft.age;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.Heightmap;
+
+/** 26.3 port of Rivencraft 1.21.1's Legacy-style 4×4 plinth and 2×12×2 shaft. */
+final class PortObelisksFeature {
+    private static final long SALT = 0x4F42454C49534B53L;
+    private static final int CHANCE = 128;
+    private static final int BASE = 4;
+    private static final int HEIGHT = 12;
+
+    private PortObelisksFeature() {}
+
+    record Site(int x, int z) {}
+
+    static Site site(long ageSeed, ChunkPos chunk, int occurrence) {
+        RandomSource random = RandomSource.create(mix(ageSeed ^ SALT
+                ^ (long) chunk.x() * 341873128712L ^ (long) chunk.z() * 132897987541L
+                ^ (long) occurrence * 0x9E3779B97F4A7C15L));
+        if (random.nextInt(CHANCE) != 0) return null;
+        return new Site(chunk.getMinBlockX() + 4 + random.nextInt(8),
+                chunk.getMinBlockZ() + 4 + random.nextInt(8));
+    }
+
+    static void generate(WorldGenLevel level, ChunkAccess chunk, long ageSeed, BlockState material, int occurrence) {
+        Site site = site(ageSeed, chunk.getPos(), occurrence);
+        if (site == null) return;
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        int minSurface = Integer.MAX_VALUE;
+        int maxSurface = Integer.MIN_VALUE;
+        int[][] surface = new int[BASE][BASE];
+        for (int dx = 0; dx < BASE; dx++) {
+            for (int dz = 0; dz < BASE; dz++) {
+                int x = site.x() + dx;
+                int z = site.z() + dz;
+                int y = level.getHeight(Heightmap.Types.WORLD_SURFACE_WG, x, z);
+                if (y <= level.getMinY() + 1) return;
+                BlockState ground = level.getBlockState(pos.set(x, y - 1, z));
+                if (!ground.isFaceSturdy(level, pos, Direction.UP)
+                        || !ground.getFluidState().isEmpty() || ground.hasBlockEntity()) return;
+                surface[dx][dz] = y;
+                minSurface = Math.min(minSurface, y);
+                maxSurface = Math.max(maxSurface, y);
+            }
+        }
+        if (maxSurface - minSurface > 2 || maxSurface + HEIGHT >= level.getMaxY()) return;
+        for (int dx = 0; dx < BASE; dx++) {
+            for (int dz = 0; dz < BASE; dz++) {
+                for (int y = surface[dx][dz]; y <= maxSurface; y++) {
+                    if (!open(level.getBlockState(pos.set(site.x() + dx, y, site.z() + dz)))) return;
+                }
+            }
+        }
+        for (int dx = 1; dx <= 2; dx++) {
+            for (int dz = 1; dz <= 2; dz++) {
+                for (int y = maxSurface + 1; y <= maxSurface + HEIGHT; y++) {
+                    if (!open(level.getBlockState(pos.set(site.x() + dx, y, site.z() + dz)))) return;
+                }
+            }
+        }
+        for (int dx = 0; dx < BASE; dx++) {
+            for (int dz = 0; dz < BASE; dz++) {
+                for (int y = surface[dx][dz]; y <= maxSurface; y++)
+                    level.setBlock(pos.set(site.x() + dx, y, site.z() + dz), material, 2);
+            }
+        }
+        for (int dx = 1; dx <= 2; dx++) {
+            for (int dz = 1; dz <= 2; dz++) {
+                for (int y = maxSurface + 1; y <= maxSurface + HEIGHT; y++)
+                    level.setBlock(pos.set(site.x() + dx, y, site.z() + dz), material, 2);
+            }
+        }
+    }
+
+    private static boolean open(BlockState state) {
+        return state.getFluidState().isEmpty() && (state.isAir() || state.canBeReplaced());
+    }
+
+    private static long mix(long value) {
+        value = (value ^ value >>> 30) * 0xBF58476D1CE4E5B9L;
+        value = (value ^ value >>> 27) * 0x94D049BB133111EBL;
+        return value ^ value >>> 31;
+    }
+}

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

@@ -0,0 +1,81 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.Random;
+import net.dnorberg.rivencraft.writing.PortRegistryPages;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.MinecraftServer;
+
+/** Seed-frozen terrain and biome choices for a book with no authored symbols. */
+public final class PortRandomAgeSelection {
+    private PortRandomAgeSelection() {}
+
+    public record Selection(PortAgeTerrain terrain, PortBiomePlan biomes) {}
+
+    public static Selection select(MinecraftServer server, long seed) {
+        // Match the 1.21.1 Legacy-rank choices: Standard and Flat are common;
+        // the other terrain families are rarer. The sorted order is deliberate.
+        PortAgeTerrain terrain = weighted(new Random(seed ^ 0x5445525241494E4CL),
+                List.of(PortAgeTerrain.AMPLIFIED, PortAgeTerrain.CAVE, PortAgeTerrain.FLAT,
+                        PortAgeTerrain.ISLAND, PortAgeTerrain.STANDARD, PortAgeTerrain.VOID),
+                new int[]{1, 1, 5, 1, 6, 1});
+        if (terrain == PortAgeTerrain.VOID)
+            return new Selection(terrain, new PortBiomePlan(PortBiomePlan.Distribution.SINGLE,
+                    List.of(Identifier.withDefaultNamespace("the_void"))));
+
+        PortBiomePlan.Distribution distribution = weighted(new Random(seed ^ 0x524956454E435241L),
+                List.of(PortBiomePlan.Distribution.NATIVE, PortBiomePlan.Distribution.SINGLE,
+                        PortBiomePlan.Distribution.MEDIUM, PortBiomePlan.Distribution.TILED,
+                        PortBiomePlan.Distribution.GRID, PortBiomePlan.Distribution.TINY,
+                        PortBiomePlan.Distribution.SMALL, PortBiomePlan.Distribution.LARGE,
+                        PortBiomePlan.Distribution.HUGE),
+                new int[]{3, 3, 3, 1, 1, 1, 1, 1, 1});
+        List<Identifier> eligible = eligibleBiomes(server, terrain);
+        if (eligible.size() < 2 && distribution != PortBiomePlan.Distribution.NATIVE)
+            distribution = PortBiomePlan.Distribution.SINGLE;
+        // 26.3 has no native multi-cave biome source; choose a seeded Cave
+        // biome rather than silently using Lush Caves for every random Age.
+        if (terrain == PortAgeTerrain.CAVE && distribution == PortBiomePlan.Distribution.NATIVE)
+            distribution = PortBiomePlan.Distribution.SINGLE;
+        if (distribution == PortBiomePlan.Distribution.NATIVE)
+            return new Selection(terrain, new PortBiomePlan(distribution, List.of()));
+
+        int count = distribution == PortBiomePlan.Distribution.SINGLE ? 1 : 2;
+        if (count > 1) {
+            Random countRandom = new Random(seed ^ 0x42494F4D45434F55L);
+            while (count < eligible.size() && countRandom.nextInt(3) != 0) count++;
+        }
+        List<Identifier> shuffled = new ArrayList<>(eligible);
+        Collections.shuffle(shuffled, new Random(seed ^ 0x42494F4D45504F4FL));
+        return new Selection(terrain, new PortBiomePlan(distribution, shuffled.subList(0, count)));
+    }
+
+    private static List<Identifier> eligibleBiomes(MinecraftServer server, PortAgeTerrain terrain) {
+        if (terrain == PortAgeTerrain.CAVE) {
+            List<Identifier> caves = server.registryAccess().lookupOrThrow(Registries.BIOME).listElements()
+                    .filter(PortRegistryPages::isCaveBiome)
+                    .map(holder -> holder.key().identifier())
+                    .sorted().toList();
+            return caves.isEmpty() ? List.of(Identifier.withDefaultNamespace("lush_caves")) : caves;
+        }
+        List<Identifier> surface = server.overworld().getChunkSource().getGenerator().getBiomeSource()
+                .possibleBiomes().stream().flatMap(holder -> holder.unwrapKey().stream())
+                .map(key -> key.identifier()).distinct().sorted(Comparator.naturalOrder()).toList();
+        return surface.isEmpty() ? List.of(Identifier.withDefaultNamespace("plains")) : surface;
+    }
+
+    static <T> T weighted(Random random, List<T> choices, int[] weights) {
+        int total = 0;
+        for (int weight : weights) total += weight;
+        int ticket = random.nextInt(total);
+        for (int index = 0; index < choices.size(); index++) {
+            ticket -= weights[index];
+            if (ticket < 0) return choices.get(index);
+        }
+        throw new IllegalStateException("Random Age ticket was not consumed");
+    }
+}

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

@@ -0,0 +1,24 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.List;
+import java.util.Optional;
+import net.minecraft.resources.Identifier;
+
+/** Frozen, ordered Rocks materials. Old single-material beta Ages remain readable. */
+public record PortRockPlan(List<Identifier> materials) {
+    public static final Codec<PortRockPlan> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Identifier.CODEC.optionalFieldOf("material").forGetter(plan -> Optional.empty()),
+            Identifier.CODEC.listOf().optionalFieldOf("materials", List.of()).forGetter(PortRockPlan::materials)
+    ).apply(instance, (old, current) -> new PortRockPlan(current.isEmpty()
+            ? old.map(List::of).orElse(List.of()) : current)));
+
+    public PortRockPlan {
+        materials = List.copyOf(materials);
+        if (materials.isEmpty() || materials.size() > 32)
+            throw new IllegalArgumentException("Rocks plan must contain 1–32 materials");
+    }
+
+    public PortRockPlan(Identifier material) { this(List.of(material)); }
+}

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

@@ -0,0 +1,91 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.MapCodec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.stream.Stream;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeResolver;
+import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.biome.Climate;
+
+/** 26.3 resolver port of the seeded 1.21.1 Mystcraft-style region distribution. */
+public final class PortScaledBiomeSource extends BiomeSource implements BiomeResolver {
+    public static final MapCodec<PortScaledBiomeSource> CODEC = RecordCodecBuilder.mapCodec(instance -> instance.group(
+            Biome.LIST_CODEC.fieldOf("biomes").forGetter(source -> source.biomes),
+            Codec.LONG.fieldOf("seed").forGetter(source -> source.seed),
+            Codec.intRange(0, 4).fieldOf("scale").forGetter(source -> source.scale)
+    ).apply(instance, PortScaledBiomeSource::new));
+
+    private final HolderSet<Biome> biomes;
+    private final long seed;
+    private final int scale;
+    private final int cellWidth;
+
+    public PortScaledBiomeSource(HolderSet<Biome> biomes, long seed, int scale) {
+        if (biomes.size() < 2 || scale < 0 || scale > 4)
+            throw new IllegalArgumentException("Scaled regions need two biomes and scale 0..4");
+        this.biomes = biomes;
+        this.seed = seed;
+        this.scale = scale;
+        // Quart coordinates; Tiny starts at 16 blocks and each scale doubles.
+        this.cellWidth = 4 << scale;
+    }
+
+    @Override
+    protected MapCodec<? extends BiomeSource> codec() {
+        return CODEC;
+    }
+
+    @Override
+    protected Stream<Holder<Biome>> collectPossibleBiomes() {
+        return biomes.stream();
+    }
+
+    @Override
+    public BiomeResolver createResolver(Climate.Sampler sampler) {
+        return this;
+    }
+
+    @Override
+    public Holder<Biome> getNoiseBiome(int x, int y, int z) {
+        int baseX = Math.floorDiv(x, cellWidth);
+        int baseZ = Math.floorDiv(z, cellWidth);
+        int closestX = baseX;
+        int closestZ = baseZ;
+        double closestDistance = Double.POSITIVE_INFINITY;
+        for (int cellX = baseX - 1; cellX <= baseX + 1; cellX++) {
+            for (int cellZ = baseZ - 1; cellZ <= baseZ + 1; cellZ++) {
+                long cellSeed = mix(seed, cellX, cellZ);
+                double centerX = (cellX + 0.5D + jitter(cellSeed) * 0.8D) * cellWidth;
+                double centerZ = (cellZ + 0.5D + jitter(mix64(cellSeed)) * 0.8D) * cellWidth;
+                double deltaX = x - centerX;
+                double deltaZ = z - centerZ;
+                double distance = deltaX * deltaX + deltaZ * deltaZ;
+                if (distance < closestDistance) {
+                    closestDistance = distance;
+                    closestX = cellX;
+                    closestZ = cellZ;
+                }
+            }
+        }
+        return biomes.get(Math.floorMod((int) mix(seed ^ 0x42494F4D45534CL,
+                closestX, closestZ), biomes.size()));
+    }
+
+    private static double jitter(long value) {
+        return ((value >>> 11) * 0x1.0p-53) - 0.5D;
+    }
+
+    private static long mix(long seed, int x, int z) {
+        return mix64(seed ^ (long) x * 0x9E3779B97F4A7C15L ^ (long) z * 0xC2B2AE3D27D4EB4FL);
+    }
+
+    private static long mix64(long value) {
+        value = (value ^ value >>> 30) * 0xBF58476D1CE4E5B9L;
+        value = (value ^ value >>> 27) * 0x94D049BB133111EBL;
+        return value ^ value >>> 31;
+    }
+}

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

@@ -0,0 +1,70 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Set;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.tags.BlockTags;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.ShelfMushroomBlock;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.feature.treedecorators.ShelfMushroomDecorator;
+import net.minecraft.world.level.levelgen.feature.treedecorators.TreeDecorator;
+
+/** Shelf mushrooms on exposed log faces, regardless of how the logs were generated. */
+final class PortShelfMushrooms {
+    private PortShelfMushrooms() {}
+
+    static List<BlockPos> findHosts(ChunkAccess chunk) {
+        List<BlockPos> logs = new ArrayList<>();
+        var sections = chunk.getSections();
+        for (int index = 0; index < sections.length; index++) {
+            var section = sections[index];
+            if (!section.maybeHas(state -> state.is(BlockTags.LOGS))) continue;
+            int baseY = chunk.getSectionYFromSectionIndex(index) << 4;
+            for (int y = 0; y < 16; y++) for (int z = 0; z < 16; z++) for (int x = 0; x < 16; x++) {
+                if (section.getBlockState(x, y, z).is(BlockTags.LOGS))
+                    logs.add(new BlockPos(chunk.getPos().getMinBlockX() + x, baseY + y,
+                            chunk.getPos().getMinBlockZ() + z));
+            }
+        }
+        return logs;
+    }
+
+    static void decorate(WorldGenLevel level, ChunkAccess chunk, List<BlockPos> logs, RandomSource random) {
+        // Reuse vanilla replaceability/water checks, but not its tree-base height
+        // band: a log tendril or sphere has no meaningful tree base.
+        TreeDecorator.Context context = new TreeDecorator.Context(level,
+                (pos, state) -> level.setBlock(pos, state, 2), random, Set.of(), Set.of(), Set.of());
+        for (BlockPos log : logs) {
+            if (!level.getBlockState(log).is(BlockTags.LOGS)) continue;
+            Direction first = Direction.Plane.HORIZONTAL.getRandomDirection(random);
+            for (Direction facing : List.of(first, first.getClockWise())) {
+                if (random.nextFloat() > 0.25F) continue;
+                BlockPos pos = log.relative(facing);
+                if ((pos.getX() >> 4) != chunk.getPos().x() || (pos.getZ() >> 4) != chunk.getPos().z()) continue;
+                if (pos.getY() < level.getMinY() || pos.getY() >= level.getMaxY()) continue;
+                if (!level.getFluidState(pos).isEmpty()
+                        || !ShelfMushroomDecorator.isBlockReplaceableWithShelfMushroom(context, pos)
+                        || level.getBlockState(pos.below()).is(Blocks.SHELF_MUSHROOM)) continue;
+                boolean adjacent = false;
+                for (Direction side : Direction.Plane.HORIZONTAL) {
+                    if (level.getBlockState(pos.relative(side)).is(Blocks.SHELF_MUSHROOM)) {
+                        adjacent = true;
+                        break;
+                    }
+                }
+                if (adjacent) continue;
+                var mushroom = Blocks.SHELF_MUSHROOM.defaultBlockState()
+                        .setValue(ShelfMushroomBlock.FACING, facing)
+                        .setValue(ShelfMushroomBlock.AGE, random.nextInt(2));
+                if (!mushroom.canSurvive(level, pos)) continue;
+                context.setBlock(pos, mushroom);
+                break;
+            }
+        }
+    }
+}

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

@@ -0,0 +1,31 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import java.util.List;
+import java.util.Locale;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+
+/** Persisted sky styles, including the client-rendered Legacy static background. */
+public enum PortSkyStyle {
+    OVERWORLD, NETHER, END, STATIC;
+
+    public static final Codec<PortSkyStyle> CODEC = Codec.STRING.xmap(
+            name -> valueOf(name.toUpperCase(Locale.ROOT)), sky -> sky.name().toLowerCase(Locale.ROOT));
+
+    public static PortSkyStyle forPage(Identifier page) {
+        if (!page.getNamespace().equals(Rivencraft.MOD_ID)) return null;
+        return switch (page.getPath()) {
+            case "sky/overworld" -> OVERWORLD;
+            case "sky/nether" -> NETHER;
+            case "sky/end" -> END;
+            case "sky/static" -> STATIC;
+            default -> null;
+        };
+    }
+
+    public static PortSkyStyle fromPages(List<Identifier> pages) {
+        return pages.stream().map(PortSkyStyle::forPage).filter(java.util.Objects::nonNull)
+                .findFirst().orElse(OVERWORLD);
+    }
+}

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

@@ -0,0 +1,87 @@
+package net.dnorberg.rivencraft.age;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.Heightmap;
+
+/**
+ * 26.3 port of Rivencraft's subtractive Skylands filter, adapted from
+ * Mystcraft Legacy's SymbolSkylands (LGPL-3.0-or-later). Keeps upper solid
+ * terrain above a seven-octave cutoff near Y=76 and removes liquids.
+ */
+final class PortSkylandsFeature {
+    private static final long SALT = 0x534B594C414E4453L;
+    private static final int BASE_CUTOFF = 76;
+    private static final BlockState AIR = Blocks.AIR.defaultBlockState();
+
+    private PortSkylandsFeature() {}
+
+    static void filter(ChunkAccess chunk, long ageSeed) {
+        int originX = chunk.getPos().getMinBlockX();
+        int originZ = chunk.getPos().getMinBlockZ();
+        int minY = chunk.getMinY();
+        int maxY = chunk.getMaxY();
+        Heightmap surface = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.WORLD_SURFACE_WG);
+        Heightmap floor = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.OCEAN_FLOOR_WG);
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        for (int localX = 0; localX < 16; localX++) {
+            for (int localZ = 0; localZ < 16; localZ++) {
+                int cutoff = cutoff(ageSeed, originX + localX, originZ + localZ);
+                for (int y = minY; y < maxY; y++) {
+                    pos.set(originX + localX, y, originZ + localZ);
+                    BlockState state = chunk.getBlockState(pos);
+                    if (!removes(state, y, cutoff)) continue;
+                    chunk.setBlockState(pos, AIR);
+                    surface.update(localX, y, localZ, AIR);
+                    floor.update(localX, y, localZ, AIR);
+                }
+            }
+        }
+    }
+
+    static boolean removes(BlockState state, int y, int cutoff) {
+        return !state.isAir() && (y <= cutoff || state.liquid());
+    }
+
+    static int cutoff(long ageSeed, int x, int z) {
+        double variation = 0.0D;
+        int cellSize = 128;
+        double amplitude = 12.0D;
+        for (int octave = 0; octave < 7; octave++) {
+            variation += valueNoise(ageSeed ^ SALT ^ (long) octave * 0x9E3779B97F4A7C15L,
+                    x, z, cellSize) * amplitude;
+            cellSize /= 2;
+            amplitude /= 2.0D;
+        }
+        return BASE_CUTOFF + (int) Math.round(variation);
+    }
+
+    private static double valueNoise(long seed, int x, int z, int cellSize) {
+        int cellX = Math.floorDiv(x, cellSize);
+        int cellZ = Math.floorDiv(z, cellSize);
+        double u = smooth((x - cellX * cellSize) / (double) cellSize);
+        double v = smooth((z - cellZ * cellSize) / (double) cellSize);
+        double north = lerp(value(seed, cellX, cellZ), value(seed, cellX + 1, cellZ), u);
+        double south = lerp(value(seed, cellX, cellZ + 1), value(seed, cellX + 1, cellZ + 1), u);
+        return lerp(north, south, v);
+    }
+
+    private static double value(long seed, int x, int z) {
+        long hash = mix(seed ^ (long) x * 0xD1B54A32D192ED03L ^ (long) z * 0xABC98388FB8FAC03L);
+        return (hash >>> 11) * 0x1.0p-52 - 1.0D;
+    }
+
+    private static double smooth(double value) { return value * value * (3.0D - 2.0D * value); }
+
+    private static double lerp(double first, double second, double amount) {
+        return first + (second - first) * amount;
+    }
+
+    private static long mix(long value) {
+        value = (value ^ value >>> 30) * 0xBF58476D1CE4E5B9L;
+        value = (value ^ value >>> 27) * 0x94D049BB133111EBL;
+        return value ^ value >>> 31;
+    }
+}

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

@@ -0,0 +1,122 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.Random;
+import net.minecraft.core.BlockPos;
+import net.minecraft.util.Mth;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.Heightmap;
+
+/**
+ * 26.3 adaptation of Rivencraft 1.21.1's solid sphere nodes, derived from
+ * Mystcraft Legacy's MapGenSpheresMyst (Mystcraft contributors,
+ * LGPL-3.0-or-later, commit 9bc8ddc). Writes stay within the target chunk.
+ */
+final class PortSpheresFeature {
+    private static final int SOURCE_RANGE = 8;
+    private static final long SALT = 0x53504845524553L;
+
+    private PortSpheresFeature() {}
+
+    static void generate(ChunkAccess chunk, long ageSeed, BlockState material) {
+        var target = chunk.getPos();
+        Random master = new Random(ageSeed ^ SALT);
+        long xSeed = master.nextLong();
+        long zSeed = master.nextLong();
+        for (int sx = target.x() - SOURCE_RANGE; sx <= target.x() + SOURCE_RANGE; sx++) {
+            for (int sz = target.z() - SOURCE_RANGE; sz <= target.z() + SOURCE_RANGE; sz++) {
+                Random source = new Random((long) sx * xSeed ^ (long) sz * zSeed ^ ageSeed ^ SALT);
+                if (source.nextFloat() > 0.05F) continue;
+                double x = sx * 16 + source.nextInt(16);
+                double y = source.nextInt(source.nextInt(192) + 1) + 32;
+                double z = sz * 16 + source.nextInt(16);
+                trace(chunk, material, source.nextLong(), x, y, z,
+                        1.0F + source.nextFloat() * 4.0F, 0, 0, -1, -1);
+            }
+        }
+    }
+
+    private static void trace(ChunkAccess chunk, BlockState material, long seed,
+                              double x, double y, double z, float radius, float yaw, float pitch,
+                              int step, int length) {
+        Random random = new Random(seed);
+        if (length <= 0) {
+            int maximum = SOURCE_RANGE * 16 - 16;
+            length = maximum - random.nextInt(maximum / 4);
+        }
+        boolean singleNode = step == -1;
+        if (singleNode) step = length / 2;
+        int splitAt = random.nextInt(length / 2) + length / 4;
+        boolean slowPitch = random.nextInt(6) == 0;
+        float yawDrift = 0;
+        float pitchDrift = 0;
+        double middleX = chunk.getPos().getMinBlockX() + 8;
+        double middleZ = chunk.getPos().getMinBlockZ() + 8;
+        for (; step < length; step++) {
+            double nodeRadius = 1.5D + Math.sin(step * Math.PI / length) * radius;
+            float horizontal = Mth.cos(pitch);
+            x += Mth.cos(yaw) * horizontal;
+            y += Mth.sin(pitch);
+            z += Mth.sin(yaw) * horizontal;
+            pitch *= slowPitch ? 0.92F : 0.7F;
+            pitch += pitchDrift * 0.1F;
+            yaw += yawDrift * 0.1F;
+            pitchDrift = pitchDrift * 0.9F
+                    + (random.nextFloat() - random.nextFloat()) * random.nextFloat() * 2.0F;
+            yawDrift = yawDrift * 0.75F
+                    + (random.nextFloat() - random.nextFloat()) * random.nextFloat() * 4.0F;
+            if (!singleNode && step == splitAt && radius > 1.0F) {
+                trace(chunk, material, random.nextLong(), x, y, z,
+                        random.nextFloat() * 0.5F + 0.5F, yaw - Mth.HALF_PI, pitch / 3, step, length);
+                trace(chunk, material, random.nextLong(), x, y, z,
+                        random.nextFloat() * 0.5F + 0.5F, yaw + Mth.HALF_PI, pitch / 3, step, length);
+                return;
+            }
+            if (!singleNode && random.nextInt(4) == 0) continue;
+            double dx = x - middleX;
+            double dz = z - middleZ;
+            double remaining = length - step;
+            double reach = radius + 18;
+            if (dx * dx + dz * dz - remaining * remaining > reach * reach) return;
+            if (Math.abs(dx) <= 16 + nodeRadius * 2 && Math.abs(dz) <= 16 + nodeRadius * 2)
+                fillNode(chunk, material, x, y, z, nodeRadius);
+            if (singleNode) break;
+        }
+    }
+
+    private static void fillNode(ChunkAccess chunk, BlockState material,
+                                 double centerX, double centerY, double centerZ, double radius) {
+        int originX = chunk.getPos().getMinBlockX();
+        int originZ = chunk.getPos().getMinBlockZ();
+        int minX = Math.max(0, Mth.floor(centerX - radius) - originX - 1);
+        int maxX = Math.min(16, Mth.floor(centerX + radius) - originX + 2);
+        int minZ = Math.max(0, Mth.floor(centerZ - radius) - originZ - 1);
+        int maxZ = Math.min(16, Mth.floor(centerZ + radius) - originZ + 2);
+        int minY = Math.max(chunk.getMinY() + 1, Mth.floor(centerY - radius) - 1);
+        int maxY = Math.min(chunk.getMaxY(), Mth.floor(centerY + radius) + 2);
+        Heightmap surface = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.WORLD_SURFACE_WG);
+        Heightmap floor = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.OCEAN_FLOOR_WG);
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        for (int worldY = minY; worldY < maxY; worldY++) {
+            double dy = (worldY + 0.5D - centerY) / radius;
+            for (int localZ = minZ; localZ < maxZ; localZ++) {
+                double dz = (originZ + localZ + 0.5D - centerZ) / radius;
+                for (int localX = minX; localX < maxX; localX++) {
+                    double dx = (originX + localX + 0.5D - centerX) / radius;
+                    if (!insideSphere(dx, dy, dz)) continue;
+                    pos.set(originX + localX, worldY, originZ + localZ);
+                    BlockState previous = chunk.getBlockState(pos);
+                    if (previous == material || previous.is(Blocks.BEDROCK)) continue;
+                    chunk.setBlockState(pos, material);
+                    surface.update(localX, worldY, localZ, material);
+                    floor.update(localX, worldY, localZ, material);
+                }
+            }
+        }
+    }
+
+    static boolean insideSphere(double dx, double dy, double dz) {
+        return dx * dx + dy * dy + dz * dz < 1.0D;
+    }
+}

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

@@ -0,0 +1,56 @@
+package net.dnorberg.rivencraft.age;
+
+import net.minecraft.core.BlockPos;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.WorldGenLevel;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.Heightmap;
+
+/**
+ * 26.3 port of Rivencraft 1.21.1's rare surface spikes, adapted from
+ * Mystcraft Legacy's WorldGenSpikesAdv (Mystcraft contributors,
+ * LGPL-3.0-or-later, commit 9bc8ddc). The footprint stays within one chunk.
+ */
+final class PortSpikesFeature {
+    private static final long SALT = 0x5350494B4553L;
+
+    private PortSpikesFeature() {}
+
+    static void generate(WorldGenLevel level, ChunkAccess chunk, long ageSeed, BlockState material, int occurrence) {
+        int originX = chunk.getPos().getMinBlockX();
+        int originZ = chunk.getPos().getMinBlockZ();
+        RandomSource random = RandomSource.create(ageSeed ^ SALT
+                ^ (long) originX * 341873128712L ^ (long) originZ * 132897987541L
+                ^ (long) occurrence * 0x9E3779B97F4A7C15L);
+        if (random.nextInt(18) != 0) return;
+        int x = originX + 4 + random.nextInt(8);
+        int z = originZ + 4 + random.nextInt(8);
+        int y = level.getHeight(Heightmap.Types.WORLD_SURFACE_WG, x, z);
+        int height = 6 + random.nextInt(32);
+        int width = 1 + random.nextInt(4);
+        if (y < level.getMinY() + 1 || y + height >= level.getMaxY()) return;
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        if (!level.isEmptyBlock(pos.set(x, y, z))) return;
+        for (int px = x - width; px <= x + width; px++) {
+            for (int pz = z - width; pz <= z + width; pz++) {
+                if (!insideFootprint(px - x, pz - z, width)) continue;
+                if (!level.getBlockState(pos.set(px, y - 1, pz)).isSolid()) return;
+            }
+        }
+        for (int px = x - width; px <= x + width; px++) {
+            for (int pz = z - width; pz <= z + width; pz++) {
+                if (!insideFootprint(px - x, pz - z, width)) continue;
+                int top = y + 1 + random.nextInt(random.nextInt(height) + 1);
+                for (int py = y; py < top; py++) {
+                    pos.set(px, py, pz);
+                    if (level.isEmptyBlock(pos)) level.setBlock(pos, material, 2);
+                }
+            }
+        }
+    }
+
+    static boolean insideFootprint(int dx, int dz, int width) {
+        return dx * dx + dz * dz <= width * width + 1;
+    }
+}

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

@@ -0,0 +1,107 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.Random;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.levelgen.Heightmap;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/**
+ * Ports Rivencraft 1.21.1's Legacy fissure footprint/carving.
+ * Derived from Mystcraft's WorldGenMystStarFissure, LGPL-3.0,
+ * copyright XCompWiz and Mystcraft contributors.
+ */
+public final class PortStarFissureFeature {
+    private static final long SALT = 0x5354415246495353L;
+
+    private PortStarFissureFeature() {}
+
+    /** Per-Age data prevents revisits/restarts from carving the same fissure again. */
+    private static final class Arrival extends SavedData {
+        private static final Codec<Arrival> CODEC = BlockPos.CODEC.optionalFieldOf("spawn").codec()
+                .xmap(Arrival::new, data -> Optional.ofNullable(data.spawn));
+        private static final SavedDataType<Arrival> TYPE = new SavedDataType<>(
+                Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "star_fissure_arrival"),
+                () -> new Arrival(Optional.empty()), CODEC);
+        private BlockPos spawn;
+
+        private Arrival(Optional<BlockPos> spawn) { this.spawn = spawn.orElse(null); }
+    }
+
+    public static BlockPos savedSpawn(ServerLevel level) {
+        return level.getDataStorage().computeIfAbsent(Arrival.TYPE).spawn;
+    }
+
+    public static void generateOnce(ServerLevel level, BlockPos spawn, boolean caveTerrain) {
+        Arrival data = level.getDataStorage().computeIfAbsent(Arrival.TYPE);
+        if (data.spawn != null) return;
+        generate(level, level.getSeed(), spawn, caveTerrain);
+        data.spawn = spawn.immutable();
+        data.setDirty();
+    }
+
+    /** Legacy chooses 8–23 blocks after the spawn chunk, then grows along +Z. */
+    public static List<BlockPos> footprint(long ageSeed, BlockPos spawn) {
+        long chunkX = spawn.getX() >> 4;
+        long chunkZ = spawn.getZ() >> 4;
+        Random random = new Random(ageSeed ^ SALT ^ chunkX ^ (chunkZ << 32));
+        int originX = ((int) chunkX << 4) + random.nextInt(16) + 8;
+        int originZ = ((int) chunkZ << 4) + random.nextInt(16) + 8;
+        int length = random.nextInt(8) + 10;
+        int[][] intervals = new int[length][2];
+        List<BlockPos> columns = new ArrayList<>();
+        addRow(columns, originX, originZ, 0, 0, 0);
+        for (int row = 1; row < length; row++) {
+            int range = length + Math.min(row, length - row) + 1;
+            int right = (random.nextInt(range) - (range >> 1) + intervals[row - 1][1]) / 2;
+            int left = (random.nextInt(range) - (range >> 1) + intervals[row - 1][0]) / 2;
+            if (left > right) {
+                int swap = left;
+                left = right;
+                right = swap;
+            }
+            left = Math.min(left, intervals[row - 1][1]);
+            right = Math.max(right, intervals[row - 1][0]);
+            intervals[row][0] = left;
+            intervals[row][1] = right;
+            addRow(columns, originX, originZ, row, left, right);
+        }
+        return List.copyOf(columns);
+    }
+
+    private static void addRow(List<BlockPos> columns, int originX, int originZ, int row, int left, int right) {
+        for (int x = left; x <= right; x++) {
+            // Only X/Z are used; the real floor is the dimension's minimum Y.
+            columns.add(new BlockPos(originX + x, 0, originZ + row * 2));
+            columns.add(new BlockPos(originX + x, 0, originZ + row * 2 + 1));
+        }
+    }
+
+    private static void generate(ServerLevel level, long ageSeed, BlockPos spawn, boolean caveTerrain) {
+        int floorY = level.getMinY();
+        BlockPos.MutableBlockPos mutable = new BlockPos.MutableBlockPos();
+        for (BlockPos column : footprint(ageSeed, spawn)) {
+            int top = level.getHeight(Heightmap.Types.WORLD_SURFACE, column.getX(), column.getZ());
+            if (caveTerrain) {
+                for (int y = Math.max(spawn.getY(), floorY + 1); y < top; y++) {
+                    if (level.getBlockState(mutable.set(column.getX(), y, column.getZ())).is(Blocks.BEDROCK)) {
+                        top = y;
+                        break;
+                    }
+                }
+            }
+            for (int y = floorY + 1; y < top; y++)
+                level.setBlock(mutable.set(column.getX(), y, column.getZ()), Blocks.AIR.defaultBlockState(), 2);
+            level.setBlock(mutable.set(column.getX(), floorY, column.getZ()),
+                    Rivencraft.STAR_FISSURE.get().defaultBlockState(), 2);
+        }
+    }
+}

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

@@ -0,0 +1,180 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.MapCodec;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.Set;
+import java.util.stream.Stream;
+import net.dnorberg.rivencraft.mixin.StructurePlacementAccessor;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderLookup;
+import net.minecraft.core.HolderOwner;
+import net.minecraft.core.HolderSet;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.tags.TagKey;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.biome.Climate;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.StructureSet;
+import net.minecraft.world.level.levelgen.structure.placement.ConcentricRingsStructurePlacement;
+import net.minecraft.world.level.levelgen.structure.placement.RandomSpreadStructurePlacement;
+
+/** 1.21.1 structure planning/density rules adapted to modern placement classes. */
+public final class PortStructurePages {
+    private static final Map<Identifier, Identifier> SETS = Map.ofEntries(
+            vanillaSet("villages", "villages"),
+            vanillaSet("mineshafts", "mineshafts"),
+            vanillaSet("strongholds", "strongholds"),
+            vanillaSet("trial_chambers", "trial_chambers"),
+            vanillaSet("buried_treasure", "buried_treasures"),
+            vanillaSet("shipwrecks", "shipwrecks"),
+            vanillaSet("ocean_ruins", "ocean_ruins"),
+            vanillaSet("pillager_outposts", "pillager_outposts"),
+            vanillaSet("ruined_portals", "ruined_portals"),
+            vanillaSet("nether_fossils", "nether_fossils"),
+            vanillaSet("ancient_cities", "ancient_cities"),
+            vanillaSet("trail_ruins", "trail_ruins"),
+            vanillaSet("abandoned_camps", "abandoned_camp"),
+            Map.entry(page("nether_fortresses"), Identifier.fromNamespaceAndPath("rivencraft", "fortresses")),
+            Map.entry(page("bastions"), Identifier.fromNamespaceAndPath("rivencraft", "bastions")));
+    // Suppress vanilla's combined Nether set so an authored Fortress page does
+    // not also introduce Bastions (or vice versa).
+    private static final Set<Identifier> CONTROLLED_SETS = Stream.concat(SETS.values().stream(),
+            Stream.of(Identifier.withDefaultNamespace("nether_complexes")))
+            .collect(java.util.stream.Collectors.toUnmodifiableSet());
+    private static final Set<Identifier> CAVE_ONLY = Set.of(
+            page("nether_fortresses"), page("bastions"), page("nether_fossils"));
+    private static final Set<Identifier> SURFACE_ONLY = Set.of(
+            page("villages"), page("strongholds"), page("buried_treasure"), page("shipwrecks"),
+            page("ocean_ruins"), page("pillager_outposts"), page("trail_ruins"), page("abandoned_camps"));
+    private static final Set<Identifier> FLAT_ALLOWED = Set.of(page("villages"), page("strongholds"));
+
+    private PortStructurePages() {}
+
+    private static Identifier page(String name) {
+        return Identifier.fromNamespaceAndPath("rivencraft", "feature/" + name);
+    }
+
+    private static Map.Entry<Identifier, Identifier> vanillaSet(String page, String set) {
+        return Map.entry(page(page), Identifier.withDefaultNamespace(set));
+    }
+
+    public static boolean supports(Identifier page) { return SETS.containsKey(page); }
+
+    public static void validateCounts(List<Identifier> pages) {
+        Map<Identifier, Integer> counts = new HashMap<>();
+        for (Identifier page : pages) {
+            if (!supports(page) || counts.merge(page, 1, Integer::sum) > 32)
+                throw new IllegalArgumentException("Structure plan requires supported pages, at most 32 per feature");
+        }
+    }
+
+    public static boolean supportsTerrain(Identifier page, PortAgeTerrain terrain) {
+        if (!supports(page) || terrain == PortAgeTerrain.VOID) return false;
+        if (terrain == PortAgeTerrain.FLAT && !FLAT_ALLOWED.contains(page)) return false;
+        if (CAVE_ONLY.contains(page)) return terrain == PortAgeTerrain.CAVE;
+        return terrain != PortAgeTerrain.CAVE || !SURFACE_ONLY.contains(page);
+    }
+
+    public static void validateRegistry(List<Identifier> pages, HolderLookup.Provider registries) {
+        var sets = registries.lookupOrThrow(Registries.STRUCTURE_SET);
+        pages.stream().filter(PortStructurePages::supports).distinct().forEach(page ->
+                sets.get(ResourceKey.create(Registries.STRUCTURE_SET, SETS.get(page)))
+                        .orElseThrow(() -> new IllegalArgumentException("Missing structure set for " + page)));
+    }
+
+    private static Map<Identifier, Integer> enabled(List<Identifier> pages) {
+        Map<Identifier, Integer> result = new HashMap<>();
+        for (Identifier page : pages) result.merge(SETS.get(page), 1, Integer::sum);
+        return result;
+    }
+
+    public static boolean authored(Structure structure, HolderLookup.Provider registries, List<Identifier> pages) {
+        var sets = registries.lookupOrThrow(Registries.STRUCTURE_SET);
+        return enabled(pages).keySet().stream()
+                .map(id -> sets.getOrThrow(ResourceKey.create(Registries.STRUCTURE_SET, id)).value())
+                .flatMap(set -> set.structures().stream()).anyMatch(entry -> entry.structure().value() == structure);
+    }
+
+    /** Extra possible biomes affect planning only; terrain still uses its original source. */
+    public static BiomeSource planningBiomes(BiomeSource actual, HolderLookup<StructureSet> sets, List<Identifier> pages) {
+        List<Holder<Biome>> extra = enabled(pages).keySet().stream()
+                .map(id -> sets.getOrThrow(ResourceKey.create(Registries.STRUCTURE_SET, id)).value())
+                .flatMap(set -> set.structures().stream()).flatMap(entry -> entry.structure().value().biomes().stream())
+                .distinct().toList();
+        return new BiomeSource() {
+            @Override protected MapCodec<? extends BiomeSource> codec() {
+                throw new UnsupportedOperationException("Planning biome sources are never serialized");
+            }
+            @Override protected Stream<Holder<Biome>> collectPossibleBiomes() {
+                return Stream.concat(actual.possibleBiomes().stream(), extra.stream());
+            }
+            @Override public net.minecraft.world.level.biome.BiomeResolver createResolver(Climate.Sampler sampler) {
+                return actual.createResolver(sampler);
+            }
+        };
+    }
+
+    public static HolderLookup<StructureSet> filtered(HolderLookup<StructureSet> source, List<Identifier> pages,
+                                                     BiomeSource actual) {
+        Map<Identifier, Integer> counts = enabled(pages);
+        Map<ResourceKey<StructureSet>, Holder.Reference<StructureSet>> copies = new HashMap<>();
+        return new HolderLookup<>() {
+            @Override public Optional<Holder.Reference<StructureSet>> get(ResourceKey<StructureSet> key) {
+                if (CONTROLLED_SETS.contains(key.identifier()) && !counts.containsKey(key.identifier())) return Optional.empty();
+                return source.get(key).filter(holder -> counts.containsKey(key.identifier()) || hasBiome(holder.value(), actual))
+                        .map(holder -> copies.computeIfAbsent(key, ignored -> {
+                            int count = counts.getOrDefault(key.identifier(), 1);
+                            return count == 1 ? holder : new LocalReference(key, scaled(holder.value(), count));
+                        }));
+            }
+            @Override public Optional<HolderSet.Named<StructureSet>> get(TagKey<StructureSet> key) { return source.get(key); }
+            @Override public Stream<Holder.Reference<StructureSet>> listElements() {
+                return source.listElements().flatMap(holder -> get(holder.key()).stream());
+            }
+            @Override public Stream<HolderSet.Named<StructureSet>> listTags() { return source.listTags(); }
+        };
+    }
+
+    private static boolean hasBiome(StructureSet set, BiomeSource source) {
+        Set<Holder<Biome>> possible = source.possibleBiomes();
+        return set.structures().stream().flatMap(entry -> entry.structure().value().biomes().stream()).anyMatch(possible::contains);
+    }
+
+    private static StructureSet scaled(StructureSet set, int count) {
+        var placement = set.placement();
+        if (!(placement instanceof RandomSpreadStructurePlacement)
+                && !(placement instanceof ConcentricRingsStructurePlacement)) return set;
+        StructurePlacementAccessor settings = (StructurePlacementAccessor) placement;
+        if (placement instanceof RandomSpreadStructurePlacement random) {
+            float original = settings.rivencraft$frequency();
+            float frequency = Math.min(1.0F, original * count);
+            double frequencyFactor = original > 0 ? frequency / original : 1;
+            int spacing = Math.max(1, (int) Math.round(random.spacing() / Math.sqrt(count / frequencyFactor)));
+            int separation = spacing == 1 ? 0 : Math.min(spacing - 1,
+                    (int) Math.round((double) random.separation() * spacing / random.spacing()));
+            return new StructureSet(set.structures(), new RandomSpreadStructurePlacement(placement.locateOffset(),
+                    settings.rivencraft$frequencyReductionMethod(), frequency, settings.rivencraft$salt(),
+                    settings.rivencraft$exclusionZone(), spacing, separation, random.spreadType()));
+        }
+        if (placement instanceof ConcentricRingsStructurePlacement rings) {
+            int total = (int) Math.min(4095, (long) rings.count() * count);
+            int spread = Math.min(total, (int) Math.min(1023, (long) rings.spread() * count));
+            return new StructureSet(set.structures(), new ConcentricRingsStructurePlacement(placement.locateOffset(),
+                    settings.rivencraft$frequencyReductionMethod(), settings.rivencraft$frequency(),
+                    settings.rivencraft$salt(), settings.rivencraft$exclusionZone(), rings.distance(), spread,
+                    total, rings.preferredBiomes()));
+        }
+        return set;
+    }
+
+    private static final class LocalReference extends Holder.Reference<StructureSet> {
+        private static final HolderOwner<StructureSet> OWNER = new HolderOwner<>() {};
+        private LocalReference(ResourceKey<StructureSet> key, StructureSet value) { super(Type.STAND_ALONE, OWNER, key, value); }
+    }
+}

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

@@ -0,0 +1,142 @@
+package net.dnorberg.rivencraft.age;
+
+import java.util.Random;
+import net.minecraft.core.BlockPos;
+import net.minecraft.util.Mth;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.Heightmap;
+
+/**
+ * 26.3 adaptation of Rivencraft 1.21.1's winding solid volumes, originally
+ * adapted from Mystcraft Legacy's SymbolTendrils and MapGenCavesMyst (LGPL-3.0-or-later).
+ * Each chunk reconstructs the neighboring source paths to preserve continuous borders.
+ */
+final class PortTendrilFeature {
+    private static final long SALT = 0x54454E4452494C53L;
+    private static final int SOURCE_RANGE = 8;
+    private static final int SOURCE_RATE = 15;
+    private static final int SOURCE_SIZE = 18;
+
+    private PortTendrilFeature() {}
+
+    static void generate(ChunkAccess chunk, long ageSeed, BlockState material) {
+        var target = chunk.getPos();
+        Random master = new Random(ageSeed ^ SALT);
+        long xSeed = master.nextLong();
+        long zSeed = master.nextLong();
+        for (int sourceX = target.x() - SOURCE_RANGE; sourceX <= target.x() + SOURCE_RANGE; sourceX++) {
+            for (int sourceZ = target.z() - SOURCE_RANGE; sourceZ <= target.z() + SOURCE_RANGE; sourceZ++) {
+                Random source = new Random((long) sourceX * xSeed ^ (long) sourceZ * zSeed ^ ageSeed ^ SALT);
+                int nodes = source.nextInt(source.nextInt(source.nextInt(SOURCE_SIZE) + 1) + 1);
+                if (source.nextInt(SOURCE_RATE) != 0) continue;
+                for (int node = 0; node < nodes; node++) {
+                    double x = sourceX * 16 + source.nextInt(16);
+                    double y = source.nextInt(source.nextInt(120) + 8);
+                    double z = sourceZ * 16 + source.nextInt(16);
+                    int branches = 1;
+                    if (source.nextInt(4) == 0) {
+                        trace(chunk, material, source.nextLong(), x, y, z,
+                                1.0F + source.nextFloat() * 6.0F, 0.0F, 0.0F, -1, -1, 0.5D);
+                        branches += source.nextInt(4);
+                    }
+                    for (int branch = 0; branch < branches; branch++) {
+                        float yaw = source.nextFloat() * Mth.TWO_PI;
+                        float pitch = (source.nextFloat() - 0.5F) / 4.0F;
+                        float radius = source.nextFloat() * 2.0F + source.nextFloat();
+                        if (source.nextInt(10) == 0)
+                            radius *= source.nextFloat() * source.nextFloat() * 3.0F + 1.0F;
+                        trace(chunk, material, source.nextLong(), x, y, z,
+                                radius, yaw, pitch, 0, 0, 1.0D);
+                    }
+                }
+            }
+        }
+    }
+
+    private static void trace(ChunkAccess chunk, BlockState material, long seed,
+                              double x, double y, double z, float radius, float yaw, float pitch,
+                              int step, int length, double verticalScale) {
+        Random random = new Random(seed);
+        if (length <= 0) {
+            int maximum = SOURCE_RANGE * 16 - 16;
+            length = maximum - random.nextInt(maximum / 4);
+        }
+        boolean singleNode = step == -1;
+        if (singleNode) step = length / 2;
+        int splitAt = random.nextInt(length / 2) + length / 4;
+        boolean slowPitch = random.nextInt(6) == 0;
+        float yawDrift = 0.0F;
+        float pitchDrift = 0.0F;
+        double middleX = chunk.getPos().getMinBlockX() + 8;
+        double middleZ = chunk.getPos().getMinBlockZ() + 8;
+        for (; step < length; step++) {
+            double horizontalRadius = 1.5D + Math.sin(step * Math.PI / length) * radius;
+            double verticalRadius = horizontalRadius * verticalScale;
+            float horizontalMotion = Mth.cos(pitch);
+            x += Mth.cos(yaw) * horizontalMotion;
+            y += Mth.sin(pitch);
+            z += Mth.sin(yaw) * horizontalMotion;
+            pitch *= slowPitch ? 0.92F : 0.7F;
+            pitch += pitchDrift * 0.1F;
+            yaw += yawDrift * 0.1F;
+            pitchDrift = pitchDrift * 0.9F
+                    + (random.nextFloat() - random.nextFloat()) * random.nextFloat() * 2.0F;
+            yawDrift = yawDrift * 0.75F
+                    + (random.nextFloat() - random.nextFloat()) * random.nextFloat() * 4.0F;
+            if (!singleNode && step == splitAt && radius > 1.0F) {
+                trace(chunk, material, random.nextLong(), x, y, z, random.nextFloat() * 0.5F + 0.5F,
+                        yaw - Mth.HALF_PI, pitch / 3.0F, step, length, 1.0D);
+                trace(chunk, material, random.nextLong(), x, y, z, random.nextFloat() * 0.5F + 0.5F,
+                        yaw + Mth.HALF_PI, pitch / 3.0F, step, length, 1.0D);
+                return;
+            }
+            if (!singleNode && random.nextInt(4) == 0) continue;
+            double distanceX = x - middleX;
+            double distanceZ = z - middleZ;
+            double remaining = length - step;
+            double reach = radius + 18.0D;
+            if (distanceX * distanceX + distanceZ * distanceZ - remaining * remaining > reach * reach) return;
+            if (x >= middleX - 16.0D - horizontalRadius * 2.0D
+                    && x <= middleX + 16.0D + horizontalRadius * 2.0D
+                    && z >= middleZ - 16.0D - horizontalRadius * 2.0D
+                    && z <= middleZ + 16.0D + horizontalRadius * 2.0D) {
+                fillNode(chunk, material, x, y, z, horizontalRadius, verticalRadius);
+            }
+            if (singleNode) break;
+        }
+    }
+
+    private static void fillNode(ChunkAccess chunk, BlockState material, double centerX, double centerY,
+                                 double centerZ, double horizontalRadius, double verticalRadius) {
+        int originX = chunk.getPos().getMinBlockX();
+        int originZ = chunk.getPos().getMinBlockZ();
+        int minX = Math.max(0, Mth.floor(centerX - horizontalRadius) - originX - 1);
+        int maxX = Math.min(16, Mth.floor(centerX + horizontalRadius) - originX + 2);
+        int minZ = Math.max(0, Mth.floor(centerZ - horizontalRadius) - originZ - 1);
+        int maxZ = Math.min(16, Mth.floor(centerZ + horizontalRadius) - originZ + 2);
+        int minY = Math.max(chunk.getMinY() + 1, Mth.floor(centerY - verticalRadius) - 1);
+        int maxY = Math.min(chunk.getMaxY(), Mth.floor(centerY + verticalRadius) + 2);
+        Heightmap surface = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.WORLD_SURFACE_WG);
+        Heightmap floor = chunk.getOrCreateHeightmapUnprimed(Heightmap.Types.OCEAN_FLOOR_WG);
+        BlockPos.MutableBlockPos pos = new BlockPos.MutableBlockPos();
+        for (int worldY = minY; worldY < maxY; worldY++) {
+            double dy = (worldY + 0.5D - centerY) / verticalRadius;
+            if (dy <= -0.7D || dy * dy >= 1.0D) continue;
+            for (int localZ = minZ; localZ < maxZ; localZ++) {
+                double dz = (originZ + localZ + 0.5D - centerZ) / horizontalRadius;
+                for (int localX = minX; localX < maxX; localX++) {
+                    double dx = (originX + localX + 0.5D - centerX) / horizontalRadius;
+                    if (dx * dx + dy * dy + dz * dz >= 1.0D) continue;
+                    pos.set(originX + localX, worldY, originZ + localZ);
+                    BlockState previous = chunk.getBlockState(pos);
+                    if (previous == material || previous.is(Blocks.BEDROCK)) continue;
+                    chunk.setBlockState(pos, material);
+                    surface.update(localX, worldY, localZ, material);
+                    floor.update(localX, worldY, localZ, material);
+                }
+            }
+        }
+    }
+}

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

@@ -0,0 +1,95 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.List;
+import java.util.HashMap;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+
+/** Frozen terrain filters and ordered solid/surface features for an Age. */
+public record PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int denseOres,
+                                     boolean starFissures, List<Identifier> structures, List<Identifier> carvers) {
+    public static final Identifier FLOATING_ISLANDS = Identifier.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "feature/floating_islands");
+    public static final Identifier TENDRILS = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/tendrils");
+    public static final Identifier SKYLANDS = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/skylands");
+    public static final Identifier SPHERES = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/spheres");
+    public static final Identifier SPIKES = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/spikes");
+    public static final Identifier OBELISKS = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/obelisks");
+    public static final Identifier CRYSTAL_FORMATIONS = Identifier.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "feature/crystal_formations");
+    public static final Identifier CRYSTAL_MATERIAL = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "crystal_block");
+    public static final Identifier DENSE_ORES = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/dense_ores");
+    public static final Identifier STAR_FISSURES = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/star_fissures");
+    public static final int MAX_PER_FEATURE = 32;
+    public static final Codec<PortTerrainFeaturePlan> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Choice.CODEC.listOf().fieldOf("choices").forGetter(PortTerrainFeaturePlan::choices),
+            Codec.BOOL.optionalFieldOf("skylands", false).forGetter(PortTerrainFeaturePlan::skylands),
+            Codec.intRange(0, MAX_PER_FEATURE).optionalFieldOf("dense_ores", 0)
+                    .forGetter(PortTerrainFeaturePlan::denseOres),
+            Codec.BOOL.optionalFieldOf("star_fissures", false).forGetter(PortTerrainFeaturePlan::starFissures),
+            Identifier.CODEC.listOf().optionalFieldOf("structures", List.of()).forGetter(PortTerrainFeaturePlan::structures),
+            Identifier.CODEC.listOf().optionalFieldOf("carvers", List.of()).forGetter(PortTerrainFeaturePlan::carvers)
+    ).apply(instance, PortTerrainFeaturePlan::new));
+
+    public record Choice(Identifier page, Identifier material) {
+        public static final Codec<Choice> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+                Identifier.CODEC.fieldOf("page").forGetter(Choice::page),
+                Identifier.CODEC.fieldOf("material").forGetter(Choice::material)
+        ).apply(instance, Choice::new));
+
+        public Choice {
+            if (!isSupported(page) || material == null)
+                throw new IllegalArgumentException("Invalid terrain feature choice");
+            if (CRYSTAL_FORMATIONS.equals(page) && !CRYSTAL_MATERIAL.equals(material))
+                throw new IllegalArgumentException("Crystal formations use Rivencraft crystal, not a Block modifier");
+        }
+    }
+
+    public PortTerrainFeaturePlan {
+        choices = List.copyOf(choices);
+        structures = List.copyOf(structures);
+        carvers = List.copyOf(carvers);
+        PortStructurePages.validateCounts(structures);
+        PortCarverPages.validateCounts(carvers);
+        if (denseOres < 0 || denseOres > MAX_PER_FEATURE)
+            throw new IllegalArgumentException("Dense Ores permits at most 32 occurrences");
+        if (choices.isEmpty() && !skylands && denseOres == 0 && !starFissures && structures.isEmpty() && carvers.isEmpty())
+            throw new IllegalArgumentException("Terrain feature plan must not be empty");
+        var counts = new HashMap<Identifier, Integer>();
+        for (Choice choice : choices) {
+            if (counts.merge(choice.page(), 1, Integer::sum) > MAX_PER_FEATURE)
+                throw new IllegalArgumentException("Terrain feature plan permits at most 32 occurrences per feature");
+        }
+    }
+
+    public PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int denseOres,
+                                 boolean starFissures, List<Identifier> structures) {
+        this(choices, skylands, denseOres, starFissures, structures, List.of());
+    }
+
+    public PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int denseOres, boolean starFissures) {
+        this(choices, skylands, denseOres, starFissures, List.of());
+    }
+
+    public PortTerrainFeaturePlan(List<Choice> choices, boolean skylands, int denseOres) {
+        this(choices, skylands, denseOres, false);
+    }
+
+    public PortTerrainFeaturePlan(List<Choice> choices, boolean skylands) { this(choices, skylands, 0, false); }
+
+    public PortTerrainFeaturePlan(List<Choice> choices) { this(choices, false, 0, false); }
+
+    public static boolean isSupported(Identifier page) {
+        return FLOATING_ISLANDS.equals(page) || TENDRILS.equals(page) || SPHERES.equals(page) || isSurface(page);
+    }
+
+    public static boolean acceptsMaterial(Identifier page) {
+        return isSupported(page) && !CRYSTAL_FORMATIONS.equals(page);
+    }
+
+    public static boolean isSurface(Identifier page) {
+        return SPIKES.equals(page) || OBELISKS.equals(page) || CRYSTAL_FORMATIONS.equals(page);
+    }
+}

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

@@ -0,0 +1,56 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+
+/** Ordered, frozen plants and log decorations; not all require surface terrain. */
+public record PortVegetationPlan(List<Identifier> pages) {
+    public static final Identifier FLOWERS = page("flowers");
+    public static final Identifier TREES = page("trees");
+    public static final Identifier HUGE_TREES = page("huge_trees");
+    public static final Identifier POPLAR_TREES = page("poplar_trees");
+    public static final Identifier FALLEN_POPLAR_TREES = page("fallen_poplar_trees");
+    public static final Identifier RED_SHRUBS = page("red_shrubs");
+    public static final Identifier SHELF_MUSHROOMS = page("shelf_mushrooms");
+    public static final Codec<PortVegetationPlan> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Identifier.CODEC.listOf().fieldOf("pages").forGetter(PortVegetationPlan::pages)
+    ).apply(instance, PortVegetationPlan::new));
+
+    public PortVegetationPlan {
+        pages = List.copyOf(pages);
+        if (pages.isEmpty() || pages.size() > 32 || pages.stream().anyMatch(page -> !isVegetation(page)))
+            throw new IllegalArgumentException("Vegetation plan requires 1–32 supported pages");
+    }
+
+    public static boolean isVegetation(Identifier page) {
+        return page.equals(FLOWERS) || page.equals(TREES) || page.equals(HUGE_TREES)
+                || page.equals(POPLAR_TREES) || page.equals(FALLEN_POPLAR_TREES)
+                || page.equals(RED_SHRUBS) || page.equals(SHELF_MUSHROOMS);
+    }
+
+    public static Identifier placedFeature(Identifier page) {
+        if (page.equals(FLOWERS)) return Identifier.withDefaultNamespace("flower_default");
+        if (page.equals(TREES)) return Identifier.withDefaultNamespace("trees_plains");
+        if (page.equals(HUGE_TREES)) return Identifier.withDefaultNamespace("trees_old_growth_spruce_taiga");
+        if (page.equals(POPLAR_TREES)) return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "poplar_trees");
+        if (page.equals(FALLEN_POPLAR_TREES)) return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "fallen_poplar_trees");
+        if (page.equals(RED_SHRUBS)) return Identifier.withDefaultNamespace("patch_red_shrub");
+        throw new IllegalArgumentException("Unsupported vegetation page " + page);
+    }
+
+    public static boolean addsLogs(Identifier page) {
+        return page.equals(TREES) || page.equals(HUGE_TREES)
+                || page.equals(POPLAR_TREES) || page.equals(FALLEN_POPLAR_TREES);
+    }
+
+    public static boolean requiresSurface(Identifier page) {
+        return isVegetation(page) && !page.equals(SHELF_MUSHROOMS);
+    }
+
+    private static Identifier page(String name) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "feature/" + name);
+    }
+}

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

@@ -0,0 +1,28 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.resources.Identifier;
+
+/** The six active weather pages in the 1.21.1 writing system. */
+public enum PortWeatherMode {
+    NORMAL, FAST, SLOW, OFF, ALWAYS, STORM;
+
+    public static final Codec<PortWeatherMode> CODEC = Codec.STRING.xmap(
+            name -> valueOf(name.toUpperCase(java.util.Locale.ROOT)),
+            mode -> mode.name().toLowerCase(java.util.Locale.ROOT));
+
+    public static PortWeatherMode forPage(Identifier page) {
+        if (!page.getNamespace().equals(Rivencraft.MOD_ID)) return null;
+        return switch (page.getPath()) {
+            case "weather/normal" -> NORMAL;
+            case "weather/fast" -> FAST;
+            case "weather/slow" -> SLOW;
+            case "weather/off" -> OFF;
+            case "weather/always" -> ALWAYS;
+            case "weather/storm" -> STORM;
+            default -> null;
+        };
+    }
+
+}

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

@@ -0,0 +1,24 @@
+package net.dnorberg.rivencraft.age;
+
+import com.mojang.serialization.Codec;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.level.saveddata.SavedData;
+import net.minecraft.world.level.saveddata.SavedDataType;
+
+/** Age-local policy; native WeatherData separately persists its live cycle. */
+final class PortWeatherSettings extends SavedData {
+    private static final Codec<PortWeatherSettings> CODEC = PortWeatherMode.CODEC
+            .fieldOf("mode").codec().xmap(PortWeatherSettings::new, settings -> settings.mode);
+    static final SavedDataType<PortWeatherSettings> TYPE = new SavedDataType<>(
+            Identifier.fromNamespaceAndPath("rivencraft", "weather_policy"),
+            () -> new PortWeatherSettings(PortWeatherMode.NORMAL), CODEC);
+
+    private PortWeatherMode mode;
+
+    private PortWeatherSettings(PortWeatherMode mode) { this.mode = mode; }
+    PortWeatherMode mode() { return mode; }
+    void setMode(PortWeatherMode mode) {
+        this.mode = mode;
+        setDirty();
+    }
+}

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

@@ -0,0 +1,480 @@
+package net.dnorberg.rivencraft.age;
+
+import java.io.IOException;
+import java.nio.file.AtomicMoveNotSupportedException;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+import java.util.List;
+import java.util.Map;
+import java.util.Optional;
+import java.util.OptionalLong;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.PortRegistryPages;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.core.Holder;
+import net.minecraft.core.HolderSet;
+import net.minecraft.resources.Identifier;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.TicketStorage;
+import net.minecraft.world.level.biome.BiomeManager;
+import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.biome.FixedBiomeSource;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.Biomes;
+import net.minecraft.world.level.biome.CheckerboardColumnBiomeSource;
+import net.minecraft.world.level.dimension.LevelStem;
+import net.minecraft.world.level.levelgen.FlatLevelSource;
+import net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator;
+import net.minecraft.world.level.levelgen.NoiseGeneratorSettings;
+import net.minecraft.world.level.levelgen.flat.FlatLevelGeneratorSettings;
+import net.minecraft.world.level.levelgen.flat.FlatLayerInfo;
+import net.minecraft.world.level.block.Blocks;
+import net.minecraft.world.level.storage.LevelResource;
+import net.neoforged.neoforge.common.NeoForge;
+import net.neoforged.neoforge.common.world.chunk.ForcedChunkManager;
+import net.neoforged.neoforge.event.level.LevelEvent;
+
+/**
+ * Server-side runtime-level foundation for 26.3. Authored generators and
+ * dynamic client registry synchronization remain separate migration steps.
+ */
+public final class RuntimeAgeBackend {
+    private RuntimeAgeBackend() {
+    }
+
+    public static void onLevelLoad(LevelEvent.Load event) {
+        if (!(event.getLevel() instanceof ServerLevel overworld) || overworld.dimension() != Level.OVERWORLD) {
+            return;
+        }
+        MinecraftServer server = overworld.getServer();
+        AgeLevelIndex index = index(server);
+        for (Map.Entry<Identifier, Long> age : index.entries().entrySet()) {
+            try {
+                load(server, age.getKey(), age.getValue(), index.biomePlan(age.getKey()),
+                        index.terrain(age.getKey()), index.rocks(age.getKey()), index.vegetation(age.getKey()),
+                        index.dungeons(age.getKey()), index.lakes(age.getKey()), index.terrainFeatures(age.getKey()));
+            } catch (RuntimeException exception) {
+                Rivencraft.LOGGER.error("Could not restore Age {}. Its saved index remains intact.", age.getKey(), exception);
+            }
+        }
+    }
+
+    /** Creates a server level, then commits its identity only after successful construction. */
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed) {
+        return create(server, id, seed, null);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed, PortBiomePlan biomePlan) {
+        return create(server, id, seed, biomePlan, PortAgeTerrain.STANDARD);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain) {
+        return create(server, id, seed, biomePlan, terrain, null);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks) {
+        return create(server, id, seed, biomePlan, terrain, rocks, null);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, 0);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, null);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, null);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
+                terrainFeatures, PortWeatherMode.NORMAL);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures, PortWeatherMode weather) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
+                terrainFeatures, weather, PortLighting.NORMAL);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures, PortWeatherMode weather,
+                                     PortLighting lighting) {
+        return create(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
+                terrainFeatures, weather, lighting, PortSkyStyle.OVERWORLD);
+    }
+
+    public static ServerLevel create(MinecraftServer server, Identifier id, long seed,
+                                     PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                     PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                     PortTerrainFeaturePlan terrainFeatures, PortWeatherMode weather,
+                                     PortLighting lighting, PortSkyStyle sky) {
+        checkServerThread(server);
+        ageName(id);
+        AgeLevelIndex index = index(server);
+        if (index.contains(id)) throw new IllegalArgumentException("Age already exists: " + id);
+        ServerLevel level = load(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
+                terrainFeatures, lighting, sky);
+        ((PortAgeLevel) level).configureWeather(weather);
+        index.add(id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, terrainFeatures, lighting, sky);
+        // A newly bound book may be used immediately. Persist its Age identity
+        // before publishing the catalog so a later crash cannot leave that
+        // book pointing at a world omitted from the on-disk index.
+        server.overworld().getDataStorage().saveAndJoin();
+        AgeCatalogSync.onCatalogChanged(server);
+        return level;
+    }
+
+    /** Unloads an Age only when no player remains; save(true) flushes other entities. */
+    public static void unload(MinecraftServer server, Identifier id) {
+        checkServerThread(server);
+        requireSeed(server, id);
+        unloadLoaded(server, id);
+        AgeCatalogSync.onCatalogChanged(server);
+    }
+
+    public static ServerLevel reload(MinecraftServer server, Identifier id) {
+        checkServerThread(server);
+        long seed = requireSeed(server, id);
+        ServerLevel level = load(server, id, seed, index(server).biomePlan(id), index(server).terrain(id),
+                index(server).rocks(id), index(server).vegetation(id), index(server).dungeons(id), index(server).lakes(id),
+                index(server).terrainFeatures(id));
+        AgeCatalogSync.onCatalogChanged(server);
+        return level;
+    }
+
+    /** Existing saved chunks stay in place; the replacement level uses the new seed. */
+    public static void reseed(MinecraftServer server, Identifier id, long seed) {
+        checkServerThread(server);
+        AgeLevelIndex index = index(server);
+        long previousSeed = requireSeed(server, id);
+        PortBiomePlan biomePlan = index.biomePlan(id);
+        PortAgeTerrain terrain = index.terrain(id);
+        PortRockPlan rocks = index.rocks(id);
+        PortVegetationPlan vegetation = index.vegetation(id);
+        int dungeons = index.dungeons(id);
+        PortLakePlan lakes = index.lakes(id);
+        PortTerrainFeaturePlan terrainFeatures = index.terrainFeatures(id);
+        if (previousSeed == seed) return;
+        boolean loaded = server.getLevel(dimensionKey(id)) != null;
+        if (loaded) unloadLoaded(server, id);
+        try {
+            if (loaded) load(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, terrainFeatures);
+            index.reseed(id, seed);
+            server.overworld().getDataStorage().saveAndJoin();
+            if (loaded) AgeCatalogSync.onCatalogChanged(server);
+        } catch (RuntimeException exception) {
+            if (loaded) {
+                try {
+                    load(server, id, previousSeed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, terrainFeatures);
+                    AgeCatalogSync.onCatalogChanged(server);
+                } catch (RuntimeException rollbackFailure) {
+                    exception.addSuppressed(rollbackFailure);
+                }
+            }
+            throw exception;
+        }
+    }
+
+    /** Retires one unloaded Age and moves only its own storage to a recoverable archive. */
+    public static void retire(MinecraftServer server, Identifier id) {
+        checkServerThread(server);
+        String name = ageName(id);
+        AgeLevelIndex index = index(server);
+        long seed = requireSeed(server, id);
+        PortBiomePlan biomePlan = index.biomePlan(id);
+        PortAgeTerrain terrain = index.terrain(id);
+        PortRockPlan rocks = index.rocks(id);
+        PortVegetationPlan vegetation = index.vegetation(id);
+        int dungeons = index.dungeons(id);
+        PortLakePlan lakes = index.lakes(id);
+        PortTerrainFeaturePlan terrainFeatures = index.terrainFeatures(id);
+        boolean loaded = server.getLevel(dimensionKey(id)) != null;
+        ArchivePaths paths = archivePaths(server, name);
+        PortLighting lighting = index.lighting(id);
+        PortSkyStyle sky = index.sky(id);
+        if (loaded) unloadLoaded(server, id);
+        // Persist the tombstone before moving files: a crash mid-archive must
+        // not let an old book silently regenerate this identity.
+        index.retire(id);
+        try {
+            server.overworld().getDataStorage().saveAndJoin();
+            if (Files.exists(paths.live(), LinkOption.NOFOLLOW_LINKS)) {
+                Files.createDirectories(paths.archive().getParent());
+                try {
+                    Files.move(paths.live(), paths.archive(), StandardCopyOption.ATOMIC_MOVE);
+                } catch (AtomicMoveNotSupportedException exception) {
+                    Files.move(paths.live(), paths.archive());
+                }
+            }
+        } catch (IOException | RuntimeException exception) {
+            try {
+                index.restoreAfterFailedRetirement(id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
+                        terrainFeatures, lighting, sky);
+                server.overworld().getDataStorage().saveAndJoin();
+            } catch (RuntimeException rollbackFailure) {
+                exception.addSuppressed(rollbackFailure);
+            }
+            if (loaded) {
+                try {
+                    load(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes, terrainFeatures);
+                } catch (RuntimeException rollbackFailure) {
+                    exception.addSuppressed(rollbackFailure);
+                }
+            }
+            throw new IllegalStateException("Could not archive Age " + id, exception);
+        }
+        AgeCatalogSync.onCatalogChanged(server);
+        Rivencraft.LOGGER.info("Retired 26.3 prototype Age {} (archived at {})", id, paths.archive());
+    }
+
+    public static Map<Identifier, Long> savedAges(MinecraftServer server) {
+        checkServerThread(server);
+        return index(server).entries();
+    }
+
+    /** Includes retired IDs, which must never be silently reused by a new book. */
+    public static boolean isNameTaken(MinecraftServer server, Identifier id) {
+        checkServerThread(server);
+        ageName(id);
+        return index(server).contains(id);
+    }
+
+    private static AgeLevelIndex index(MinecraftServer server) {
+        return server.overworld().getDataStorage().computeIfAbsent(AgeLevelIndex.TYPE);
+    }
+
+    private static void checkServerThread(MinecraftServer server) {
+        if (!server.isSameThread()) throw new IllegalStateException("Runtime Age operation outside server thread");
+    }
+
+    private static long requireSeed(MinecraftServer server, Identifier id) {
+        ageName(id);
+        Long seed = index(server).seed(id);
+        if (seed == null) throw new IllegalArgumentException("Age not active: " + id);
+        return seed;
+    }
+
+    private static String ageName(Identifier id) {
+        if (!id.getNamespace().equals(Rivencraft.MOD_ID) || !id.getPath().startsWith("age/")) {
+            throw new IllegalArgumentException("Expected a rivencraft:age/* dimension ID: " + id);
+        }
+        String name = id.getPath().substring("age/".length());
+        if (name.isBlank() || name.contains("/") || name.equals(".") || name.equals("..")) {
+            throw new IllegalArgumentException("Expected a single safe Age path segment: " + id);
+        }
+        return name;
+    }
+
+    private static ResourceKey<Level> dimensionKey(Identifier id) {
+        return ResourceKey.create(Registries.DIMENSION, id);
+    }
+
+    private static void unloadLoaded(MinecraftServer server, Identifier id) {
+        ResourceKey<Level> key = dimensionKey(id);
+        ServerLevel level = server.getLevel(key);
+        if (level == null) throw new IllegalStateException("Age not loaded: " + id);
+        if (!level.players().isEmpty()) {
+            throw new IllegalStateException("Age still contains players; move them before unloading: " + id);
+        }
+        // Match the server shutdown sequence so forced tickets are persisted
+        // as inactive, rather than holding stale references to this level.
+        level.getChunkSource().deactivateTicketsOnClosing();
+        level.getChunkSource().tick(() -> true, false);
+        level.save(null, true, false);
+        try {
+            level.close();
+        } catch (IOException exception) {
+            throw new IllegalStateException("Could not close Age: " + id, exception);
+        }
+        server.levels.remove(key);
+        NeoForge.EVENT_BUS.post(new LevelEvent.Unload(level));
+        Rivencraft.LOGGER.info("Unloaded 26.3 prototype Age {}", id);
+    }
+
+    private static ArchivePaths archivePaths(MinecraftServer server, String name) {
+        Path world = server.getWorldPath(LevelResource.ROOT).toAbsolutePath().normalize();
+        Path dimensions = world.resolve("dimensions");
+        Path namespace = dimensions.resolve(Rivencraft.MOD_ID);
+        Path ageRoot = namespace.resolve("age");
+        Path live = ageRoot.resolve(name).normalize();
+        Path archiveRoot = world.getParent().resolve(world.getFileName() + "-retired-ages").normalize();
+        Path archive = archiveRoot.resolve(name).normalize();
+        if (!live.getParent().equals(ageRoot) || !archive.getParent().equals(archiveRoot)
+                || Files.isSymbolicLink(world) || Files.isSymbolicLink(dimensions)
+                || Files.isSymbolicLink(namespace) || Files.isSymbolicLink(ageRoot)
+                || Files.isSymbolicLink(live) || Files.isSymbolicLink(archiveRoot)
+                || Files.exists(archive, LinkOption.NOFOLLOW_LINKS)) {
+            throw new IllegalStateException("Unsafe or existing Age archive path for " + name);
+        }
+        return new ArchivePaths(live, archive);
+    }
+
+    private record ArchivePaths(Path live, Path archive) {
+    }
+
+    private static BiomeSource authoredBiomeSource(MinecraftServer server, PortBiomePlan plan, long seed) {
+        if (plan.distribution() == PortBiomePlan.Distribution.NATIVE)
+            throw new IllegalArgumentException("Native biome distribution has no authored source");
+        var registry = server.registryAccess().lookupOrThrow(Registries.BIOME);
+        List<Holder<Biome>> biomes = plan.biomes().stream().map(id ->
+                (Holder<Biome>) registry.get(ResourceKey.create(Registries.BIOME, id))
+                        .orElseThrow(() -> new IllegalArgumentException("Unknown authored biome: " + id)))
+                .toList();
+        return switch (plan.distribution()) {
+            case NATIVE -> throw new IllegalStateException("Native is not an override");
+            case SINGLE -> new FixedBiomeSource(biomes.getFirst());
+            case TILED, GRID -> new CheckerboardColumnBiomeSource(HolderSet.direct(biomes),
+                    plan.distribution() == PortBiomePlan.Distribution.GRID ? 0 : 4);
+            case TINY, SMALL, MEDIUM, LARGE, HUGE -> new PortScaledBiomeSource(
+                    HolderSet.direct(biomes), seed, plan.distribution().ordinal() -
+                            PortBiomePlan.Distribution.TINY.ordinal());
+        };
+    }
+
+    private static ServerLevel load(MinecraftServer server, Identifier id, long seed,
+                                    PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                    PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                    PortTerrainFeaturePlan terrainFeatures) {
+        return load(server, id, seed, biomePlan, terrain, rocks, vegetation, dungeons, lakes,
+                terrainFeatures, index(server).lighting(id), index(server).sky(id));
+    }
+
+    private static ServerLevel load(MinecraftServer server, Identifier id, long seed,
+                                    PortBiomePlan biomePlan, PortAgeTerrain terrain, PortRockPlan rocks,
+                                    PortVegetationPlan vegetation, int dungeons, PortLakePlan lakes,
+                                    PortTerrainFeaturePlan terrainFeatures, PortLighting lighting, PortSkyStyle sky) {
+        ResourceKey<Level> key = ResourceKey.create(Registries.DIMENSION, id);
+        if (server.getLevel(key) != null) throw new IllegalArgumentException("Level already loaded: " + id);
+
+        // Noise terrains reuse the Overworld biome source unless a
+        // non-Native authored distribution replaces it.
+        // LevelStem.seedOverride controls chunk random state and getSeed().
+        LevelStem overworldStem = server.registryAccess().lookupOrThrow(Registries.LEVEL_STEM)
+                .getValue(LevelStem.OVERWORLD);
+        if (overworldStem == null) throw new IllegalStateException("Missing Overworld LevelStem");
+        var generator = overworldStem.generator();
+        if (terrain == PortAgeTerrain.FLAT || terrain == PortAgeTerrain.VOID) {
+            var biomes = server.registryAccess().lookupOrThrow(Registries.BIOME);
+            Holder<Biome> biome = biomes.getOrThrow(terrain == PortAgeTerrain.VOID
+                    ? Biomes.THE_VOID : Biomes.PLAINS);
+            if (biomePlan != null && !biomePlan.biomes().isEmpty()) {
+                Identifier biomeId = biomePlan.biomes().getFirst();
+                biome = biomes.get(ResourceKey.create(Registries.BIOME, biomeId))
+                        .orElseThrow(() -> new IllegalArgumentException("Unknown authored biome: " + biomeId));
+            }
+            FlatLevelGeneratorSettings settings;
+            if (terrain == PortAgeTerrain.FLAT) {
+                settings = FlatLevelGeneratorSettings.getDefault(biomes,
+                        server.registryAccess().lookupOrThrow(Registries.STRUCTURE_SET),
+                        server.registryAccess().lookupOrThrow(Registries.PLACED_FEATURE));
+                // Vanilla superflat begins at the modern minimum build height.
+                // Pad the column with air so the first solid layer begins at Y=0.
+                int airBelowZero = Math.max(0, -server.overworld().getMinY());
+                if (airBelowZero > 0)
+                    settings.getLayersInfo().addFirst(new FlatLayerInfo(airBelowZero, Blocks.AIR));
+                settings = settings.withBiomeAndLayers(settings.getLayersInfo(),
+                        settings.structureOverrides(), biome);
+                settings.setDecoration();
+            } else {
+                settings = new FlatLevelGeneratorSettings(Optional.empty(), biome, List.of());
+                settings.updateLayers();
+            }
+            generator = biomePlan != null && biomePlan.biomes().size() > 1
+                    ? new PortFlatChunkGenerator(authoredBiomeSource(server, biomePlan, seed), settings)
+                    : new FlatLevelSource(settings);
+        } else if ((biomePlan != null && biomePlan.distribution() != PortBiomePlan.Distribution.NATIVE)
+                || terrain != PortAgeTerrain.STANDARD) {
+            if (!(generator instanceof NoiseBasedChunkGenerator noise))
+                throw new IllegalStateException("Overworld generator cannot accept authored noise settings");
+            var source = terrain == PortAgeTerrain.CAVE
+                    ? new FixedBiomeSource(server.registryAccess().lookupOrThrow(Registries.BIOME)
+                            .getOrThrow(Biomes.LUSH_CAVES))
+                    : generator.getBiomeSource();
+            if (terrain == PortAgeTerrain.CAVE && biomePlan != null) {
+                var biomes = server.registryAccess().lookupOrThrow(Registries.BIOME);
+                for (Identifier biomeId : biomePlan.biomes()) {
+                    var holder = biomes.get(ResourceKey.create(Registries.BIOME, biomeId))
+                            .orElseThrow(() -> new IllegalArgumentException("Unknown authored biome: " + biomeId));
+                    if (!PortRegistryPages.isCaveBiome(holder))
+                        throw new IllegalArgumentException("Cave terrain requires a Cave or Nether biome: " + biomeId);
+                }
+            }
+            if (biomePlan != null && biomePlan.distribution() != PortBiomePlan.Distribution.NATIVE) {
+                source = authoredBiomeSource(server, biomePlan, seed);
+            }
+            var settings = switch (terrain) {
+                case STANDARD -> noise.generatorSettings();
+                case AMPLIFIED -> server.registryAccess().lookupOrThrow(Registries.NOISE_SETTINGS)
+                        .getOrThrow(NoiseGeneratorSettings.AMPLIFIED);
+                case ISLAND -> server.registryAccess().lookupOrThrow(Registries.NOISE_SETTINGS)
+                        .getOrThrow(NoiseGeneratorSettings.FLOATING_ISLANDS);
+                case CAVE -> dryCaveSettings(server);
+                case FLAT, VOID -> throw new IllegalStateException("Flat terrain should use FlatLevelSource");
+            };
+            generator = new NoiseBasedChunkGenerator(source, settings);
+        }
+        if (rocks != null || vegetation != null || dungeons > 0 || lakes != null || terrainFeatures != null)
+            generator = new PortFeatureChunkGenerator(generator, rocks, vegetation, dungeons, lakes, terrainFeatures, seed);
+        LevelStem stem = new LevelStem(lighting.dimensionType(server, terrain, overworldStem.type(), sky),
+                generator, OptionalLong.of(seed));
+        long biomeZoomSeed = BiomeManager.obfuscateSeed(server.getWorldGenSettings().options().seed());
+        ServerLevel level = new PortAgeLevel(server, key, stem, biomeZoomSeed, terrain);
+
+        // Publish only after the constructor succeeds. If the load event fails,
+        // roll back the map and close the newly opened chunk/entity stores.
+        try {
+            server.levels.put(key, level);
+            level.getWorldBorder().setAbsoluteMaxSize(server.getAbsoluteMaxWorldSize());
+            server.getPlayerList().addWorldborderListener(level);
+            NeoForge.EVENT_BUS.post(new LevelEvent.Load(level));
+            TicketStorage tickets = level.getDataStorage().get(TicketStorage.TYPE);
+            if (tickets != null) {
+                tickets.activateAllDeactivatedTickets();
+                ForcedChunkManager.activateAllDeactivatedTickets(level, tickets);
+            }
+            Rivencraft.LOGGER.info("Loaded 26.3 prototype Age {} with seed {}", id, seed);
+            return level;
+        } catch (RuntimeException exception) {
+            server.levels.remove(key);
+            try {
+                level.close();
+            } catch (IOException closeException) {
+                exception.addSuppressed(closeException);
+            }
+            throw exception;
+        }
+    }
+
+    private static Holder<NoiseGeneratorSettings> dryCaveSettings(MinecraftServer server) {
+        NoiseGeneratorSettings caves = server.registryAccess().lookupOrThrow(Registries.NOISE_SETTINGS)
+                .getOrThrow(NoiseGeneratorSettings.CAVES).value();
+        return Holder.direct(new NoiseGeneratorSettings(
+                caves.noiseSettings(), caves.defaultBlock(), Blocks.AIR.defaultBlockState(),
+                caves.noiseRouter(), caves.materialRule(), caves.spawnTarget(),
+                caves.noiseSettings().minY() - 1, caves.disableMobGeneration(), Optional.empty(),
+                caves.useLegacyRandomSource(), caves.debugFunctions()));
+    }
+}

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

@@ -0,0 +1,45 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Direction;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.util.RandomSource;
+import net.minecraft.world.level.block.AmethystBlock;
+import net.minecraft.world.level.block.AmethystClusterBlock;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.BuddingAmethystBlock;
+import net.minecraft.world.level.block.state.BlockBehaviour;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.material.Fluids;
+
+/** Vanilla amethyst growth, using Rivencraft's blue crystal stages. */
+public final class BuddingCrystalBlock extends AmethystBlock {
+    public BuddingCrystalBlock(BlockBehaviour.Properties properties) {
+        super(properties);
+    }
+
+    @Override
+    protected void randomTick(BlockState state, ServerLevel level, BlockPos pos, RandomSource random) {
+        if (random.nextInt(5) != 0) return;
+        Direction direction = Direction.values()[random.nextInt(Direction.values().length)];
+        BlockPos target = pos.relative(direction);
+        BlockState existing = level.getBlockState(target);
+        Block next = nextStage(existing, direction);
+        if (next == null) return;
+        level.setBlockAndUpdate(target, next.defaultBlockState()
+                .setValue(AmethystClusterBlock.FACING, direction)
+                .setValue(AmethystClusterBlock.WATERLOGGED,
+                        existing.getFluidState().getType() == Fluids.WATER));
+    }
+
+    public static Block nextStage(BlockState existing, Direction direction) {
+        if (BuddingAmethystBlock.canClusterGrowAtState(existing)) return Rivencraft.SMALL_CRYSTAL_BUD.get();
+        if (!existing.hasProperty(AmethystClusterBlock.FACING)
+                || existing.getValue(AmethystClusterBlock.FACING) != direction) return null;
+        if (existing.is(Rivencraft.SMALL_CRYSTAL_BUD)) return Rivencraft.MEDIUM_CRYSTAL_BUD.get();
+        if (existing.is(Rivencraft.MEDIUM_CRYSTAL_BUD)) return Rivencraft.LARGE_CRYSTAL_BUD.get();
+        if (existing.is(Rivencraft.LARGE_CRYSTAL_BUD)) return Rivencraft.CRYSTAL_CLUSTER.get();
+        return null;
+    }
+}

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

@@ -0,0 +1,47 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.block.entity.InkMixerBlockEntity;
+import net.dnorberg.rivencraft.menu.InkMixerMenu;
+import net.minecraft.core.BlockPos;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.Containers;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.SimpleMenuProvider;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+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.phys.BlockHitResult;
+
+/** 26.3 API adaptation of the 1.21.1 Ink Mixer block. */
+public final class InkMixerBlock extends BaseEntityBlock {
+    public InkMixerBlock(Properties properties) { super(properties); }
+
+    @Override protected RenderShape getRenderShape(BlockState state) { return RenderShape.MODEL; }
+    @Override public BlockEntity newBlockEntity(BlockPos pos, BlockState state) {
+        return new InkMixerBlockEntity(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 InkMixerBlockEntity mixer) {
+            serverPlayer.openMenu(new SimpleMenuProvider(
+                    (id, inventory, ignored) -> new InkMixerMenu(id, inventory, mixer),
+                    Component.translatable("container.rivencraft.ink_mixer")),
+                    buffer -> buffer.writeBlockPos(pos));
+        }
+        return InteractionResult.SUCCESS;
+    }
+
+    @Override public void playerDestroy(ServerLevel level, ServerPlayer player, BlockPos pos,
+                                        BlockState state, BlockEntity entity, ItemStack tool) {
+        if (entity instanceof InkMixerBlockEntity mixer) Containers.dropContents(level, pos, mixer);
+        super.playerDestroy(level, player, pos, state, entity, tool);
+    }
+}

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

@@ -0,0 +1,63 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.block.entity.PortBookBinderBlockEntity;
+import net.dnorberg.rivencraft.menu.PortBookBinderMenu;
+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.server.level.ServerLevel;
+import net.minecraft.world.Containers;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.SimpleMenuProvider;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.ItemStack;
+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 PortBookBinderBlock extends BaseEntityBlock {
+    public static final EnumProperty<Direction> FACING = BlockStateProperties.HORIZONTAL_FACING;
+
+    public PortBookBinderBlock(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 PortBookBinderBlockEntity(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 PortBookBinderBlockEntity binder) {
+            serverPlayer.openMenu(new SimpleMenuProvider(
+                    (id, inventory, ignored) -> new PortBookBinderMenu(id, inventory, binder),
+                    Component.translatable("container.rivencraft.book_binder")),
+                    buffer -> {
+                        buffer.writeBlockPos(pos);
+                        buffer.writeUtf(binder.title(), 32);
+                    });
+        }
+        return InteractionResult.SUCCESS;
+    }
+    @Override public void playerDestroy(ServerLevel level, ServerPlayer player, BlockPos pos,
+                                        BlockState state, BlockEntity entity, ItemStack tool) {
+        if (entity instanceof PortBookBinderBlockEntity binder) Containers.dropContents(level, pos, binder);
+        super.playerDestroy(level, player, pos, state, entity, tool);
+    }
+}

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

@@ -0,0 +1,66 @@
+package net.dnorberg.rivencraft.block;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.entity.StarFissureBlockEntity;
+import net.minecraft.core.BlockPos;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.world.entity.Entity;
+import net.minecraft.world.entity.InsideBlockEffectApplier;
+import net.minecraft.world.level.BlockGetter;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.Block;
+import net.minecraft.world.level.block.EndPortalBlock;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockBehaviour;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.portal.TeleportTransition;
+import net.minecraft.world.phys.Vec3;
+import net.minecraft.world.phys.shapes.CollisionContext;
+import net.minecraft.world.phys.shapes.VoxelShape;
+
+/** Non-obtainable starfield portal returning entities to the shared Overworld spawn. */
+public final class StarFissureBlock extends EndPortalBlock {
+    private static final VoxelShape SHAPE = Block.box(0, 0, 0, 16, 1.6, 16);
+
+    public StarFissureBlock(BlockBehaviour.Properties properties) { super(properties); }
+
+    @Override
+    public BlockEntity newBlockEntity(BlockPos pos, BlockState state) {
+        return new StarFissureBlockEntity(pos, state);
+    }
+
+    @Override
+    public void animateTick(BlockState state, Level level, BlockPos pos, net.minecraft.util.RandomSource random) {
+        // Legacy fissures have a starfield, not vanilla End portal smoke.
+    }
+
+    @Override
+    protected VoxelShape getShape(BlockState state, BlockGetter level, BlockPos pos, CollisionContext context) {
+        return SHAPE;
+    }
+
+    @Override
+    protected void entityInside(BlockState state, Level level, BlockPos pos, Entity entity,
+                                InsideBlockEffectApplier effects, boolean precise) {
+        // Do not inherit End credits or End-dimension travel from the vanilla block.
+        if (entity.canUsePortal(false)) entity.setAsInsidePortal(this, pos);
+    }
+
+    @Override
+    public TeleportTransition getPortalDestination(ServerLevel level, Entity entity, BlockPos pos) {
+        if (level.dimension() == Level.OVERWORLD) return null;
+        ServerLevel overworld = level.getServer().overworld();
+        if (overworld == null) return null;
+        BlockPos spawn = overworld.getRespawnData().pos();
+        BlockPos landing = net.dnorberg.rivencraft.age.PortAgeTravel.findFootedDestination(overworld, spawn).orElse(spawn);
+        level.playSound(null, pos, Rivencraft.LINK_FISSURE.get(), SoundSource.BLOCKS, 1.0F, 1.0F);
+        return new TeleportTransition(overworld, Vec3.atBottomCenterOf(landing), entity.getDeltaMovement(),
+                entity.getYRot(), entity.getXRot(), TeleportTransition.PLACE_PORTAL_TICKET.then(arrived -> {
+                    // Departure audio can be discarded when the client switches levels.
+                    // Play after arrival too so the traveler hears the successful return.
+                    arrived.level().playSound(null, arrived.blockPosition(), Rivencraft.LINK_FISSURE.get(),
+                            SoundSource.BLOCKS, 1.0F, 1.0F);
+                }));
+    }
+}

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

@@ -0,0 +1,176 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import java.util.Random;
+import net.dnorberg.rivencraft.item.LinkProperties;
+import net.dnorberg.rivencraft.item.InkVialItem;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.writing.InkVialExchange;
+import net.dnorberg.rivencraft.writing.InkModifierIngredients;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+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.item.Items;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.storage.ValueInput;
+import net.minecraft.world.level.storage.ValueOutput;
+
+/** Server-owned Link Panel mixer with a persistent, Legacy-style additive mixture. */
+public final class InkMixerBlockEntity extends BlockEntity implements Container {
+    public static final int INK = 0;
+    public static final int PAPER = 1;
+    public static final int BOTTLES = 2;
+    public static final int SIZE = 3;
+
+    private NonNullList<ItemStack> items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+    private int inkRemaining;
+    private long nextModifierSeed = new Random().nextLong();
+    private final double[] modifierChances = new double[3];
+    private static final int[] FLAGS = {LinkProperties.DISARM,
+            LinkProperties.MAINTAIN_MOMENTUM, LinkProperties.INTRA_LINKING};
+    private static final String[] CHANCE_KEYS = {"DisarmChance", "MomentumChance", "IntraLinkingChance"};
+    private static final int[] OLD_CHANCE_INDEX = {0, 2, 3};
+
+    public InkMixerBlockEntity(BlockPos pos, BlockState state) {
+        super(Rivencraft.INK_MIXER_BLOCK_ENTITY.get(), pos, state);
+    }
+
+    public int inkRemaining() { return inkRemaining; }
+
+    public int modifierChancePermille(int index) {
+        return Math.clamp((int) Math.round(modifierChances[index] * 1000), 0, 1000);
+    }
+
+    /** Infuses a carried ingredient into the current ink pool; only the server calls this. */
+    public boolean addModifier(ItemStack carried, int amount) {
+        InkModifierIngredients.Ingredient ingredient = InkModifierIngredients.find(carried);
+        if (ingredient == null || inkRemaining == 0 || amount <= 0 || carried.getCount() < amount)
+            return false;
+        for (InkModifierIngredients.Effect effect : ingredient.effects())
+            for (int index = 0; index < FLAGS.length; index++)
+                if (FLAGS[index] == effect.flag())
+                    modifierChances[index] = 1.0 - (1.0 - modifierChances[index])
+                            * Math.pow(1.0 - effect.chance(), amount);
+        carried.shrink(amount);
+        setChanged();
+        return true;
+    }
+
+    public ItemStack previewLinkPanel() {
+        if (!canCreateLinkPanel()) return ItemStack.EMPTY;
+        ItemStack panel = PageItem.createLinkPanelPage();
+        LinkProperties properties = rollProperties(nextModifierSeed).properties();
+        if (properties.flags() != 0) panel.set(Rivencraft.LINK_PROPERTIES.get(), properties);
+        return panel;
+    }
+
+    private record Roll(LinkProperties properties, long nextSeed) {}
+
+    private Roll rollProperties(long seed) {
+        Random random = new Random(seed);
+        int selected = 0;
+        for (int index = 0; index < FLAGS.length; index++)
+            if (modifierChances[index] > 0 && random.nextDouble() < modifierChances[index])
+                selected |= FLAGS[index];
+        return new Roll(new LinkProperties(selected), random.nextLong());
+    }
+
+    @Override public int getContainerSize() { return SIZE; }
+    @Override public boolean isEmpty() { return items.stream().allMatch(ItemStack::isEmpty); }
+    @Override public ItemStack getItem(int slot) { return items.get(slot); }
+    @Override public ItemStack removeItem(int slot, int amount) {
+        ItemStack removed = ContainerHelper.removeItem(items, slot, amount);
+        if (!removed.isEmpty()) {
+            setChanged();
+            if (slot == BOTTLES) refillEmptyBasin();
+        }
+        return removed;
+    }
+    @Override public ItemStack removeItemNoUpdate(int slot) { return ContainerHelper.takeItem(items, slot); }
+    @Override public void setItem(int slot, ItemStack stack) {
+        items.set(slot, stack);
+        if (stack.getCount() > getMaxStackSize()) stack.setCount(getMaxStackSize());
+        setChanged();
+        if (slot == INK || slot == BOTTLES) refillEmptyBasin();
+    }
+    @Override public boolean canPlaceItem(int slot, ItemStack stack) {
+        return switch (slot) {
+            case INK -> stack.is(Rivencraft.INK_VIAL.get());
+            case PAPER -> stack.is(Items.PAPER);
+            default -> false;
+        };
+    }
+    @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;
+    }
+
+    /** No server tick: refill only when ink, bottle space, or consumption changes. */
+    private void refillEmptyBasin() {
+        if (level != null && !level.isClientSide() && inkRemaining == 0) {
+            int addedInk = InkVialExchange.exchange(items, INK, BOTTLES);
+            if (addedInk > 0) {
+                inkRemaining = addedInk;
+                setChanged();
+            }
+        }
+    }
+
+    public boolean canCreateLinkPanel() {
+        if (!items.get(PAPER).is(Items.PAPER)) return false;
+        return InkVialExchange.canPay(items, INK, BOTTLES, inkRemaining, 1);
+    }
+
+    /** Commit inputs only when a virtual output is actually taken. */
+    public boolean consumeLinkPanelMaterials() {
+        if (!canCreateLinkPanel()) return false;
+        int cost = 1;
+        if (inkRemaining < cost) {
+            inkRemaining += InkVialExchange.exchange(items, INK, BOTTLES);
+        }
+        inkRemaining -= cost;
+        items.get(PAPER).shrink(1);
+        if (items.get(PAPER).isEmpty()) items.set(PAPER, ItemStack.EMPTY);
+        nextModifierSeed = rollProperties(nextModifierSeed).nextSeed();
+        java.util.Arrays.fill(modifierChances, 0);
+        setChanged();
+        if (inkRemaining == 0) refillEmptyBasin();
+        return true;
+    }
+
+    @Override public void setLevel(Level level) {
+        super.setLevel(level);
+        refillEmptyBasin();
+    }
+    @Override public void clearContent() {
+        items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+        inkRemaining = 0;
+        java.util.Arrays.fill(modifierChances, 0);
+        setChanged();
+    }
+    @Override protected void loadAdditional(ValueInput input) {
+        super.loadAdditional(input);
+        items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+        ContainerHelper.loadAllItems(input, items);
+        inkRemaining = Math.clamp(input.getIntOr("InkRemaining", 0), 0, InkVialItem.CAPACITY);
+        nextModifierSeed = input.getLongOr("NextModifierSeed", nextModifierSeed);
+        for (int index = 0; index < modifierChances.length; index++) {
+            modifierChances[index] = Math.clamp(input.getDoubleOr(CHANCE_KEYS[index],
+                    input.getDoubleOr("ModifierChance" + OLD_CHANCE_INDEX[index], 0.0)), 0.0, 1.0);
+        }
+    }
+    @Override protected void saveAdditional(ValueOutput output) {
+        super.saveAdditional(output);
+        ContainerHelper.saveAllItems(output, items);
+        output.putInt("InkRemaining", inkRemaining);
+        output.putLong("NextModifierSeed", nextModifierSeed);
+        for (int index = 0; index < modifierChances.length; index++)
+            output.putDouble(CHANCE_KEYS[index], modifierChances[index]);
+    }
+}

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

@@ -0,0 +1,141 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import java.util.ArrayList;
+import java.util.List;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.minecraft.resources.Identifier;
+import net.minecraft.core.BlockPos;
+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.item.Items;
+import net.minecraft.world.level.block.entity.BlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+import net.minecraft.world.level.storage.ValueInput;
+import net.minecraft.world.level.storage.ValueOutput;
+
+/** Persistent, server-owned Binder inputs. */
+public final class PortBookBinderBlockEntity extends BlockEntity implements Container {
+    public static final int COVER = 0;
+    public static final int PANEL = 1;
+    public static final int OUTPUT = 2;
+    public static final int FIRST_PAGE = 3;
+    public static final int PAGE_COUNT = 252;
+    public static final int SIZE = FIRST_PAGE + PAGE_COUNT;
+    private NonNullList<ItemStack> items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+    private String title = "";
+
+    public PortBookBinderBlockEntity(BlockPos pos, BlockState state) {
+        super(Rivencraft.BOOK_BINDER_BLOCK_ENTITY.get(), pos, state);
+    }
+
+    public String title() { return title; }
+
+    public void setTitle(String value) {
+        String normalized = value == null ? "" : value.strip();
+        if (normalized.length() > 32) return;
+        if (!title.equals(normalized)) {
+            title = normalized;
+            setChanged();
+        }
+    }
+
+    @Override public int getContainerSize() { return SIZE; }
+    @Override public boolean isEmpty() { return items.stream().allMatch(ItemStack::isEmpty); }
+    @Override public void clearContent() {
+        items.clear();
+        items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+        setChanged();
+    }
+    @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);
+        setChanged();
+    }
+    @Override public boolean canPlaceItem(int slot, ItemStack stack) {
+        if (slot == COVER) return stack.is(Items.LEATHER);
+        if (slot == PANEL) return PageItem.isLinkPanel(stack);
+        return slot >= FIRST_PAGE && slot < SIZE && validSymbolPage(stack);
+    }
+    private static boolean validSymbolPage(ItemStack stack) {
+        return stack.is(Rivencraft.PAGE.get()) && !PageItem.isLinkPanel(stack)
+                && stack.has(Rivencraft.SYMBOL_PAGE_ID.get());
+    }
+
+    public boolean hasSymbolPages() {
+        for (int slot = FIRST_PAGE; slot < SIZE; slot++)
+            if (!items.get(slot).isEmpty()) return true;
+        return false;
+    }
+
+    public List<Identifier> symbolPages() {
+        List<Identifier> pages = new ArrayList<>();
+        for (int slot = FIRST_PAGE; slot < SIZE; slot++) {
+            Identifier symbol = items.get(slot).get(Rivencraft.SYMBOL_PAGE_ID.get());
+            if (symbol != null) pages.add(symbol);
+        }
+        return List.copyOf(pages);
+    }
+
+    public void clearSymbolPages() {
+        for (int slot = FIRST_PAGE; slot < SIZE; slot++) items.set(slot, ItemStack.EMPTY);
+        setChanged();
+    }
+
+    public int nextPageIndex() {
+        for (int index = PAGE_COUNT - 1; index >= 0; index--)
+            if (!items.get(FIRST_PAGE + index).isEmpty()) return index + 1;
+        return 0;
+    }
+
+    public boolean insertPage(int index, ItemStack page) {
+        int end = nextPageIndex();
+        if (index < 0 || index > end || end >= PAGE_COUNT || page.getCount() != 1
+                || !validSymbolPage(page)) return false;
+        for (int current = end; current > index; current--)
+            items.set(FIRST_PAGE + current, items.get(FIRST_PAGE + current - 1));
+        items.set(FIRST_PAGE + index, page.copy());
+        setChanged();
+        return true;
+    }
+
+    public ItemStack takePage(int index) {
+        int end = nextPageIndex();
+        if (index < 0 || index >= end) return ItemStack.EMPTY;
+        ItemStack removed = items.get(FIRST_PAGE + index);
+        for (int current = index; current < end - 1; current++)
+            items.set(FIRST_PAGE + current, items.get(FIRST_PAGE + current + 1));
+        items.set(FIRST_PAGE + end - 1, ItemStack.EMPTY);
+        setChanged();
+        return removed;
+    }
+    @Override public boolean stillValid(Player player) {
+        return level != null && level.getBlockEntity(worldPosition) == this
+                && player.distanceToSqr(worldPosition.getX() + 0.5, worldPosition.getY() + 0.5,
+                        worldPosition.getZ() + 0.5) <= 64.0;
+    }
+    @Override protected void saveAdditional(ValueOutput output) {
+        super.saveAdditional(output);
+        ContainerHelper.saveAllItems(output, items);
+        output.putString("Title", title);
+    }
+    @Override protected void loadAdditional(ValueInput input) {
+        super.loadAdditional(input);
+        items = NonNullList.withSize(SIZE, ItemStack.EMPTY);
+        ContainerHelper.loadAllItems(input, items);
+        title = input.getStringOr("Title", "");
+    }
+}

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

@@ -0,0 +1,12 @@
+package net.dnorberg.rivencraft.block.entity;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.BlockPos;
+import net.minecraft.world.level.block.entity.TheEndPortalBlockEntity;
+import net.minecraft.world.level.block.state.BlockState;
+
+public final class StarFissureBlockEntity extends TheEndPortalBlockEntity {
+    public StarFissureBlockEntity(BlockPos pos, BlockState state) {
+        super(Rivencraft.STAR_FISSURE_BLOCK_ENTITY.get(), pos, state);
+    }
+}

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

@@ -0,0 +1,31 @@
+package net.dnorberg.rivencraft.client;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.age.AgeCatalogAckPayload;
+import net.dnorberg.rivencraft.age.AgeCatalogPayload;
+import net.minecraft.client.multiplayer.ClientPacketListener;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.world.level.Level;
+import net.neoforged.api.distmarker.Dist;
+import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.fml.common.EventBusSubscriber;
+import net.neoforged.neoforge.client.network.event.RegisterClientPayloadHandlersEvent;
+import java.util.stream.Collectors;
+
+@EventBusSubscriber(modid = Rivencraft.MOD_ID, value = Dist.CLIENT)
+public final class AgeCatalogClient {
+    private AgeCatalogClient() {
+    }
+
+    @SubscribeEvent
+    public static void register(RegisterClientPayloadHandlersEvent event) {
+        event.register(AgeCatalogPayload.TYPE, (payload, context) -> {
+            if (!(context.listener() instanceof ClientPacketListener listener)) return;
+            listener.levels = payload.dimensions().stream()
+                    .map(id -> ResourceKey.<Level>create(Registries.DIMENSION, id))
+                    .collect(Collectors.toUnmodifiableSet());
+            context.reply(new AgeCatalogAckPayload(payload.version()));
+        });
+    }
+}

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

@@ -0,0 +1,167 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.platform.InputConstants;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.InkVialItem;
+import net.dnorberg.rivencraft.menu.InkMixerMenu;
+import net.minecraft.client.gui.GuiGraphicsExtractor;
+import net.minecraft.client.input.MouseButtonEvent;
+import net.minecraft.client.gui.screens.inventory.AbstractContainerScreen;
+import net.minecraft.client.renderer.RenderPipelines;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.inventory.ContainerInput;
+import net.minecraft.world.item.ItemStack;
+
+/** 1.21.1 Legacy atlas and mixer animation adapted to the 26.3 GUI API. */
+public final class InkMixerScreen extends AbstractContainerScreen<InkMixerMenu> {
+    private static final Identifier BACKGROUND = Identifier.fromNamespaceAndPath(
+            Rivencraft.MOD_ID, "textures/gui/ink_mixer_legacy.png");
+    private static final int BASIN_X = 88;
+    private static final int BASIN_Y = 49;
+    private static final int BASIN_RADIUS = 30;
+    private static final int[] PROPERTY_COLORS = {0xFFE84848, 0xFF5555FF, 0xFF55EF55};
+    private final int[] lastChances = new int[3];
+    private boolean basinClickPendingRelease;
+    private long lastAdditionTime;
+
+    public InkMixerScreen(InkMixerMenu menu, Inventory inventory, Component title) {
+        super(menu, inventory, title, 176, 181);
+        inventoryLabelY = 87;
+    }
+
+    @Override public boolean isPauseScreen() { return false; }
+
+    @Override public void extractBackground(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        super.extractBackground(graphics, mouseX, mouseY, partialTick);
+        int left = (width - imageWidth) / 2;
+        int top = (height - imageHeight) / 2;
+        graphics.blit(RenderPipelines.GUI_TEXTURED, BACKGROUND, left + 54, top + 16,
+                179, 16, 66, 65, 256, 256);
+        if (menu.inkRemaining() > 0) {
+            graphics.fill(left + 54, top + 16, left + 120, top + 81, 0xFF101014);
+            renderPropertyGlyph(graphics);
+        }
+        graphics.blit(RenderPipelines.GUI_TEXTURED, BACKGROUND, left, top,
+                0, 0, imageWidth, imageHeight, 256, 256);
+    }
+
+    @Override protected void extractLabels(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        graphics.text(font, playerInventoryTitle, inventoryLabelX, inventoryLabelY, 0xFF404040, false);
+    }
+
+    @Override protected void extractTooltip(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        super.extractTooltip(graphics, mouseX, mouseY);
+        if (overBasin(mouseX, mouseY)) {
+            var lines = new java.util.ArrayList<Component>();
+            lines.add(Component.translatable("screen.rivencraft.ink_mixer.ink",
+                    menu.inkRemaining(), InkVialItem.CAPACITY));
+            lines.add(Component.translatable("screen.rivencraft.ink_mixer.additive_hint"));
+            for (int index = 0; index < 3; index++) {
+                int chance = menu.modifierChancePermille(index);
+                if (chance > 0) lines.add(Component.translatable("screen.rivencraft.ink_mixer.chance",
+                        switch (index) {
+                            case 0 -> Component.translatable("item.rivencraft.link_property.disarm");
+                            case 1 -> Component.translatable("item.rivencraft.link_property.maintain_momentum");
+                            default -> Component.translatable("item.rivencraft.link_property.intra_linking");
+                        }, chance / 10.0));
+            }
+            graphics.setComponentTooltipForNextFrame(font, lines, mouseX, mouseY, ItemStack.EMPTY, null);
+        }
+    }
+
+    @Override public boolean mouseClicked(MouseButtonEvent event, boolean doubleClick) {
+        if ((event.button() == InputConstants.MOUSE_BUTTON_LEFT
+                || event.button() == InputConstants.MOUSE_BUTTON_RIGHT)
+                && overBasin(event.x(), event.y()) && !menu.getCarried().isEmpty()) {
+            minecraft.gameMode.handleContainerInput(menu.containerId, InkMixerMenu.MODIFIER,
+                    event.button() == InputConstants.MOUSE_BUTTON_RIGHT ? 1 : 0,
+                    ContainerInput.PICKUP, minecraft.player);
+            basinClickPendingRelease = true;
+            return true;
+        }
+        return super.mouseClicked(event, doubleClick);
+    }
+
+    @Override public boolean mouseReleased(MouseButtonEvent event) {
+        if (basinClickPendingRelease) {
+            basinClickPendingRelease = false;
+            return true;
+        }
+        return super.mouseReleased(event);
+    }
+
+    private boolean overBasin(double mouseX, double mouseY) {
+        double x = mouseX - leftPos - BASIN_X;
+        double y = mouseY - topPos - BASIN_Y;
+        return x * x + y * y < BASIN_RADIUS * BASIN_RADIUS;
+    }
+
+    /** A GUI-scale projection of Legacy's colored, rotating D'ni ink effect. */
+    private void renderPropertyGlyph(GuiGraphicsExtractor graphics) {
+        long now = System.currentTimeMillis();
+        int[] active = new int[3];
+        int count = 0;
+        int strongest = 0;
+        for (int index = 0; index < lastChances.length; index++) {
+            int chance = menu.modifierChancePermille(index);
+            if (chance > lastChances[index]) lastAdditionTime = now;
+            lastChances[index] = chance;
+            if (chance > 0) {
+                active[count++] = index;
+                strongest = Math.max(strongest, chance);
+            }
+        }
+        if (count == 0) {
+            lastAdditionTime = 0;
+            return;
+        }
+
+        double cycle = now / 1800.0;
+        int first = active[(int) cycle % count];
+        int second = active[((int) cycle + 1) % count];
+        double blend = (1.0 - Math.cos((cycle % 1.0) * Math.PI)) / 2.0;
+        int rgb = blendRgb(PROPERTY_COLORS[first], PROPERTY_COLORS[second], blend);
+        double pulse = Math.max(0.0, 1.0 - (now - lastAdditionTime) / 700.0);
+        int alpha = Math.clamp((int) (70 + strongest * 0.14 + pulse * 45), 0, 255);
+        int color = alpha << 24 | rgb;
+        int centerX = leftPos + BASIN_X;
+        int centerY = topPos + BASIN_Y;
+        double turn = now / 1200.0;
+
+        for (int spoke = 0; spoke < 4; spoke++) {
+            for (int step = 0; step <= 30; step++) {
+                double progress = step / 30.0;
+                double angle = turn + spoke * Math.PI / 2.0 + progress * 0.9;
+                double radius = 3.0 + progress * (15.0 + pulse * 3.0);
+                plot(graphics, centerX + Math.cos(angle) * radius,
+                        centerY + Math.sin(angle) * radius, color);
+            }
+        }
+        for (int step = 0; step < 96; step++) {
+            double angle = step * Math.PI / 48.0 + turn * 0.3;
+            plot(graphics, centerX + Math.cos(angle) * 19.0,
+                    centerY + Math.sin(angle) * 19.0, color);
+            if (strongest >= 990 && step % 2 == 0) {
+                plot(graphics, centerX + Math.cos(angle) * 23.0,
+                        centerY + Math.sin(angle) * 23.0, color);
+            }
+        }
+    }
+
+    private static int blendRgb(int first, int second, double amount) {
+        int red = (int) (((first >> 16) & 0xFF) * (1.0 - amount)
+                + ((second >> 16) & 0xFF) * amount);
+        int green = (int) (((first >> 8) & 0xFF) * (1.0 - amount)
+                + ((second >> 8) & 0xFF) * amount);
+        int blue = (int) ((first & 0xFF) * (1.0 - amount) + (second & 0xFF) * amount);
+        return red << 16 | green << 8 | blue;
+    }
+
+    private static void plot(GuiGraphicsExtractor graphics, double x, double y, int color) {
+        int pixelX = (int) Math.round(x);
+        int pixelY = (int) Math.round(y);
+        graphics.fill(pixelX, pixelY, pixelX + 1, pixelY + 1, color);
+    }
+}

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

@@ -0,0 +1,40 @@
+package net.dnorberg.rivencraft.client;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.neoforged.api.distmarker.Dist;
+import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.fml.common.EventBusSubscriber;
+import net.neoforged.neoforge.client.event.RegisterMenuScreensEvent;
+import net.neoforged.neoforge.client.event.RegisterSpecialModelRendererEvent;
+import net.neoforged.neoforge.client.event.AddClientReloadListenersEvent;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.packs.resources.ResourceManagerReloadListener;
+
+@EventBusSubscriber(modid = Rivencraft.MOD_ID, value = Dist.CLIENT)
+public final class PortBookBinderClientEvents {
+    private PortBookBinderClientEvents() {}
+
+    @SubscribeEvent
+    public static void registerBlockEntityRenderers(
+            net.neoforged.neoforge.client.event.EntityRenderersEvent.RegisterRenderers event) {
+        event.registerBlockEntityRenderer(Rivencraft.STAR_FISSURE_BLOCK_ENTITY.get(), context -> new StarFissureRenderer());
+    }
+
+    @SubscribeEvent
+    public static void registerScreens(RegisterMenuScreensEvent event) {
+        event.register(Rivencraft.BOOK_BINDER_MENU.get(), PortBookBinderScreen::new);
+        event.register(Rivencraft.INK_MIXER_MENU.get(), InkMixerScreen::new);
+    }
+
+    @SubscribeEvent
+    public static void registerPageRenderer(RegisterSpecialModelRendererEvent event) {
+        event.register(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "symbol_page"),
+                PortSymbolPageRenderer.Unbaked.MAP_CODEC);
+    }
+
+    @SubscribeEvent
+    public static void registerPageTextureReload(AddClientReloadListenersEvent event) {
+        event.addListener(Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "symbol_page_textures"),
+                (ResourceManagerReloadListener) manager -> PortSymbolPageTextures.clear());
+    }
+}

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

@@ -0,0 +1,259 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.platform.InputConstants;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.entity.PortBookBinderBlockEntity;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.menu.PortBookBinderMenu;
+import net.dnorberg.rivencraft.network.AssembleBinderPayload;
+import net.dnorberg.rivencraft.network.PortBookNetworking;
+import net.dnorberg.rivencraft.network.SetBinderTitlePayload;
+import net.dnorberg.rivencraft.writing.PortAuthoredWriting;
+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.input.MouseButtonEvent;
+import net.minecraft.client.renderer.RenderPipelines;
+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;
+
+/** Legacy-sized Binder with a page strip and single-click book assembly. */
+public final class PortBookBinderScreen extends AbstractContainerScreen<PortBookBinderMenu> {
+    private static final Identifier BACKGROUND = Identifier.fromNamespaceAndPath(
+            "rivencraft", "textures/gui/book_binder_legacy.png");
+    private static final Identifier PAGE_ATLAS = Identifier.fromNamespaceAndPath(
+            "rivencraft", "textures/gui/notebook_pages.png");
+    private static final int PAGE_Y = 48;
+    private static final int PAGE_WIDTH = 26;
+    private static final int PAGE_HEIGHT = 34;
+    private static final int PAGE_STEP = 28;
+    private static final int VISIBLE_PAGES = 5;
+    private static final int STRIP_X = 7;
+    private static final int STRIP_Y = 45;
+    private static final int STRIP_WIDTH = 162;
+    private static final int STRIP_HEIGHT = 40;
+    private static final int MISSING_PANEL_X = 27;
+    private static final int MISSING_PANEL_Y = 26;
+    private static final int MISSING_PANEL_SIZE = 16;
+    private static final ItemStack MISSING_PANEL_ICON = PageItem.createLinkPanelPage();
+    private EditBox titleInput;
+    private boolean stripClickPendingRelease;
+    private int firstVisible;
+
+    public PortBookBinderScreen(PortBookBinderMenu menu, Inventory inventory, Component title) {
+        super(menu, inventory, title, 176, 181);
+        inventoryLabelY = 87;
+    }
+
+    @Override public boolean isPauseScreen() { return false; }
+
+    @Override protected void init() {
+        super.init();
+        int left = (width - imageWidth) / 2;
+        int top = (height - imageHeight) / 2;
+        titleInput = new EditBox(font, left + 9, top + 10, 112, 12, Component.literal("Age name"));
+        titleInput.setBordered(false);
+        titleInput.setTextColor(0xFFFFFFFF);
+        titleInput.setMaxLength(PortBookNetworking.MAX_BOOK_TITLE_LENGTH);
+        titleInput.setValue(menu.title());
+        titleInput.setHint(Component.literal("Name this Age"));
+        titleInput.setResponder(value -> ClientPacketDistributor.sendToServer(
+                new SetBinderTitlePayload(menu.containerId, value)));
+        addRenderableWidget(titleInput);
+        setInitialFocus(titleInput);
+    }
+
+    @Override public void extractBackground(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        super.extractBackground(graphics, mouseX, mouseY, partialTick);
+        int left = (width - imageWidth) / 2;
+        int top = (height - imageHeight) / 2;
+        graphics.blit(RenderPipelines.GUI_TEXTURED, BACKGROUND, left, top, 0, 0,
+                imageWidth, imageHeight, 256, 256);
+        graphics.fill(left + 7, top + 9, left + 123, top + 23, 0xFF000000);
+        firstVisible = Math.min(firstVisible, maxFirstVisible());
+        int visibleCount = Math.min(VISIBLE_PAGES, visiblePageCount() - firstVisible);
+        for (int visible = 0; visible < visibleCount; visible++) {
+            int x = left + 16 + visible * PAGE_STEP;
+            graphics.blit(RenderPipelines.GUI_TEXTURED, PAGE_ATLAS,
+                    x, top + PAGE_Y, 156, 0, PAGE_WIDTH, PAGE_HEIGHT, 256, 256);
+        }
+        // GUI extraction batches textures within a stratum. The glyphs need a
+        // later stratum so another atlas page cannot cover their transparent quad.
+        graphics.nextStratum();
+        for (int visible = 0; visible < visibleCount; visible++) {
+            int index = firstVisible + visible;
+            int x = left + 16 + visible * PAGE_STEP;
+            int y = top + PAGE_Y;
+            ItemStack page = pageAt(index);
+            if (page.isEmpty()) {
+                graphics.fill(x, y, x + PAGE_WIDTH, y + PAGE_HEIGHT, 0xAA000000);
+            } else if (PageItem.isLinkPanel(page)) {
+                graphics.fill(x + 5, y + 6, x + 22, y + 17, 0xFF000000);
+            } else {
+                if (!PortAuthoredWriting.isPageImplemented(page.get(Rivencraft.SYMBOL_PAGE_ID.get())))
+                    graphics.fill(x, y, x + PAGE_WIDTH, y + PAGE_HEIGHT, 0x88FF3333);
+                // Render the full-size transparent glyph through the working
+                // item pipeline, without its small parchment-backed icon.
+                ItemStack glyphOnly = page.copy();
+                glyphOnly.set(Rivencraft.PAGE_GLYPH_ONLY.get(), true);
+                graphics.pose().pushMatrix();
+                graphics.pose().translate(x + 1, y + 5);
+                graphics.pose().scale(1.5F, 1.5F);
+                graphics.fakeItem(glyphOnly, 0, 0);
+                graphics.pose().popMatrix();
+            }
+        }
+        graphics.fill(left + STRIP_X, top + STRIP_Y, left + STRIP_X + 8,
+                top + STRIP_Y + STRIP_HEIGHT, firstVisible == 0 ? 0x33000000 : 0xAA000000);
+        graphics.fill(left + STRIP_X + STRIP_WIDTH - 8, top + STRIP_Y,
+                left + STRIP_X + STRIP_WIDTH, top + STRIP_Y + STRIP_HEIGHT,
+                firstVisible >= maxFirstVisible() ? 0x33000000 : 0xAA000000);
+        boolean panelPresent = !menu.getSlot(PortBookBinderBlockEntity.PANEL).getItem().isEmpty();
+        if (titleInput == null || titleInput.getValue().isBlank()) {
+            graphics.fill(left + 7, top + 9, left + 123, top + 10, 0xFFFF3030);
+            graphics.fill(left + 7, top + 22, left + 123, top + 23, 0xFFFF3030);
+        }
+        if (!panelPresent) {
+            graphics.fakeItem(MISSING_PANEL_ICON, left + MISSING_PANEL_X, top + MISSING_PANEL_Y);
+            float phase = (System.currentTimeMillis() % 4000L) / 2000.0F;
+            float fade = phase > 1.0F ? 2.0F - phase : phase;
+            int alpha = 40 + (int) (125 * fade);
+            graphics.fill(left + MISSING_PANEL_X, top + MISSING_PANEL_Y,
+                    left + MISSING_PANEL_X + MISSING_PANEL_SIZE,
+                    top + MISSING_PANEL_Y + MISSING_PANEL_SIZE,
+                    (alpha << 24) | 0x00B02020);
+        }
+        if (hasUnsupportedPages()) graphics.text(font,
+                Component.translatable("screen.rivencraft.book_binder.authored_pending"),
+                left + 75, top + 31, 0xFFB84B42, false);
+        if (!hasUnsupportedPages() && menu.getSlot(2).getItem().isEmpty() && !menu.getSlot(0).getItem().isEmpty()
+                && !menu.getSlot(1).getItem().isEmpty() && titleInput != null
+                && !titleInput.getValue().isBlank()) {
+            graphics.fakeItem(new ItemStack(Rivencraft.DESCRIPTIVE_BOOK.get()), left + 152, top + 27);
+        }
+    }
+
+    @Override protected void extractLabels(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        graphics.text(font, playerInventoryTitle, inventoryLabelX, inventoryLabelY, 0xFF404040, false);
+    }
+
+    @Override protected void extractTooltip(GuiGraphicsExtractor graphics, int mouseX, int mouseY) {
+        super.extractTooltip(graphics, mouseX, mouseY);
+        int x = mouseX - leftPos;
+        int y = mouseY - topPos;
+        if (x >= MISSING_PANEL_X && x < MISSING_PANEL_X + MISSING_PANEL_SIZE
+                && y >= MISSING_PANEL_Y && y < MISSING_PANEL_Y + MISSING_PANEL_SIZE
+                && menu.getSlot(1).getItem().isEmpty()) {
+            graphics.setTooltipForNextFrame(font,
+                    Component.translatable("screen.rivencraft.book_binder.missing_panel"), mouseX, mouseY);
+        } else {
+            int index = pageIndexAt(mouseX, mouseY);
+            if (index >= 0 && !pageAt(index).isEmpty())
+                graphics.setTooltipForNextFrame(font, pageAt(index), mouseX, mouseY);
+        }
+    }
+
+    private ItemStack pageAt(int index) {
+        return menu.getSlot(index == 0 ? PortBookBinderBlockEntity.PANEL
+                : PortBookBinderBlockEntity.FIRST_PAGE + index - 1).getItem();
+    }
+
+    private int displayedPages() {
+        for (int index = PortBookBinderBlockEntity.PAGE_COUNT; index >= 1; index--)
+            if (!pageAt(index).isEmpty()) return index + 1;
+        return pageAt(0).isEmpty() ? 0 : 1;
+    }
+
+    private boolean hasUnsupportedPages() {
+        java.util.List<Identifier> pages = new java.util.ArrayList<>();
+        for (int index = 1; index <= PortBookBinderBlockEntity.PAGE_COUNT; index++) {
+            Identifier id = pageAt(index).get(Rivencraft.SYMBOL_PAGE_ID.get());
+            if (id != null) pages.add(id);
+        }
+        return !PortAuthoredWriting.supports(pages);
+    }
+
+    private int visiblePageCount() {
+        return Math.min(PortBookBinderBlockEntity.PAGE_COUNT + 1,
+                displayedPages() + (menu.getCarried().isEmpty() ? 0 : 1));
+    }
+
+    private int maxFirstVisible() { return Math.max(0, visiblePageCount() - VISIBLE_PAGES); }
+
+    private int pageIndexAt(double mouseX, double mouseY) {
+        int x = (int) mouseX - leftPos;
+        int y = (int) mouseY - topPos;
+        if (x < 16 || x >= STRIP_X + STRIP_WIDTH - 8 || y < STRIP_Y || y >= STRIP_Y + STRIP_HEIGHT)
+            return -1;
+        int visible = (x - 16) / PAGE_STEP;
+        return visible < VISIBLE_PAGES ? firstVisible + visible : -1;
+    }
+
+    @Override public boolean mouseClicked(MouseButtonEvent event, boolean doubleClick) {
+        int left = (width - imageWidth) / 2;
+        int top = (height - imageHeight) / 2;
+        if ((event.button() == InputConstants.MOUSE_BUTTON_LEFT
+                || event.button() == InputConstants.MOUSE_BUTTON_RIGHT)
+                && event.x() >= left + STRIP_X && event.x() < left + STRIP_X + STRIP_WIDTH
+                && event.y() >= top + STRIP_Y && event.y() < top + STRIP_Y + STRIP_HEIGHT) {
+            stripClickPendingRelease = true;
+            if (event.x() < left + STRIP_X + 8) firstVisible = Math.max(0, firstVisible - 1);
+            else if (event.x() >= left + STRIP_X + STRIP_WIDTH - 8)
+                firstVisible = Math.min(maxFirstVisible(), firstVisible + 1);
+            else {
+                int index = pageIndexAt(event.x(), event.y());
+                if (index >= 0 && index <= displayedPages()
+                        && (index < displayedPages() || !menu.getCarried().isEmpty()))
+                    minecraft.gameMode.handleInventoryButtonClick(menu.containerId,
+                            PortBookBinderMenu.STRIP_CLICK_BASE + index);
+            }
+            return true;
+        }
+        if (event.button() == InputConstants.MOUSE_BUTTON_LEFT
+                && event.x() >= left + 151 && event.x() < left + 170
+                && event.y() >= top + 26 && event.y() < top + 45
+                && !hasUnsupportedPages() && menu.getSlot(2).getItem().isEmpty()
+                && menu.getCarried().isEmpty()) {
+            String name = titleInput.getValue().strip();
+            if (!name.isEmpty()) ClientPacketDistributor.sendToServer(new AssembleBinderPayload(name));
+            return true;
+        }
+        return super.mouseClicked(event, doubleClick);
+    }
+
+    @Override public boolean mouseReleased(MouseButtonEvent event) {
+        if (stripClickPendingRelease) {
+            stripClickPendingRelease = false;
+            return true;
+        }
+        return super.mouseReleased(event);
+    }
+
+    @Override public boolean mouseScrolled(double mouseX, double mouseY, double scrollX, double scrollY) {
+        if (mouseX >= leftPos + STRIP_X && mouseX < leftPos + STRIP_X + STRIP_WIDTH
+                && mouseY >= topPos + STRIP_Y && mouseY < topPos + STRIP_Y + STRIP_HEIGHT) {
+            firstVisible = Math.clamp(firstVisible - (int) Math.signum(scrollY), 0, maxFirstVisible());
+            return true;
+        }
+        return super.mouseScrolled(mouseX, mouseY, scrollX, scrollY);
+    }
+
+    @Override public boolean keyPressed(KeyEvent event) {
+        if (titleInput != null && titleInput.isFocused()) {
+            if (event.isEscape()) {
+                setFocused(null);
+                titleInput.setFocused(false);
+            } else {
+                titleInput.keyPressed(event);
+            }
+            // The character event inserts text. Never forward a focused key
+            // to the container's inventory/hotbar shortcuts.
+            return true;
+        }
+        return super.keyPressed(event);
+    }
+}

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

@@ -0,0 +1,29 @@
+package net.dnorberg.rivencraft.client;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.client.Minecraft;
+import net.minecraft.world.InteractionResult;
+import net.neoforged.api.distmarker.Dist;
+import net.neoforged.bus.api.SubscribeEvent;
+import net.neoforged.fml.common.EventBusSubscriber;
+import net.neoforged.neoforge.event.entity.player.PlayerInteractEvent;
+
+/** Opens screens only on the physical client, including integrated singleplayer. */
+@EventBusSubscriber(modid = Rivencraft.MOD_ID, value = Dist.CLIENT)
+public final class PortBookInteractionHandler {
+    private PortBookInteractionHandler() {
+    }
+
+    @SubscribeEvent
+    public static void onRightClickItem(PlayerInteractEvent.RightClickItem event) {
+        if (!event.getEntity().level().isClientSide()) return;
+        boolean linking = event.getItemStack().is(Rivencraft.LINKING_BOOK.get());
+        boolean descriptive = event.getItemStack().is(Rivencraft.DESCRIPTIVE_BOOK.get());
+        if (!linking && !descriptive) return;
+        event.setCanceled(true);
+        event.setCancellationResult(InteractionResult.SUCCESS);
+        Minecraft.getInstance().setScreenAndShow(linking
+                ? new PortLinkingBookScreen(event.getHand(), event.getItemStack().copy())
+                : new PortDescriptiveBookScreen(event.getHand(), event.getItemStack().copy()));
+    }
+}

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

@@ -0,0 +1,116 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.platform.InputConstants;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.network.BindDescriptiveBookPayload;
+import net.dnorberg.rivencraft.network.PortBookNetworking;
+import net.dnorberg.rivencraft.network.UseDescriptiveBookPayload;
+import net.minecraft.client.gui.GuiGraphicsExtractor;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.components.EditBox;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.client.input.MouseButtonEvent;
+import net.minecraft.client.renderer.RenderPipelines;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.ItemStack;
+import net.neoforged.neoforge.client.network.ClientPacketDistributor;
+
+/** Temporary 26.3 descriptive-book interaction; authored pages and live previews remain unported. */
+public final class PortDescriptiveBookScreen extends Screen {
+    private static final int WIDTH = 327;
+    private static final int HEIGHT = 199;
+    private static final int TEXT_COLOR = 0xFF3B281B;
+    private static final Identifier COVER = texture("bookui_cover.png");
+    private static final Identifier LEFT_PAGE = texture("notebook_pages.png");
+    private static final Identifier RIGHT_PANEL = texture("bookui_pager.png");
+
+    private final InteractionHand hand;
+    private final boolean bound;
+    private EditBox titleInput;
+
+    public PortDescriptiveBookScreen(InteractionHand hand, ItemStack book) {
+        super(book.getHoverName());
+        this.hand = hand;
+        bound = book.has(Rivencraft.AGE_BOOK_ID.get());
+    }
+
+    @Override
+    protected void init() {
+        if (bound) return;
+        int left = (width - WIDTH) / 2;
+        int top = (height - HEIGHT) / 2;
+        titleInput = new EditBox(font, left + 40, top + 69, 110, 20,
+                Component.literal("Age name"));
+        titleInput.setMaxLength(PortBookNetworking.MAX_BOOK_TITLE_LENGTH);
+        titleInput.setHint(Component.literal("Name this Age"));
+        addRenderableWidget(titleInput);
+        setInitialFocus(titleInput);
+        addRenderableWidget(Button.builder(Component.literal("Bind"), button -> bind())
+                .bounds(left + 40, top + 100, 53, 20).build());
+        addRenderableWidget(Button.builder(Component.literal("Cancel"), button -> onClose())
+                .bounds(left + 97, top + 100, 53, 20).build());
+    }
+
+    @Override
+    public void extractRenderState(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        int left = (width - WIDTH) / 2;
+        int top = (height - HEIGHT) / 2;
+        blit(graphics, COVER, left, top + 7, 34, 192, 152, 0);
+        blit(graphics, COVER, left + 34, top + 7, 103, 192, 49, 0);
+        blit(graphics, COVER, left + 137, top + 7, 4, 192, 45, 0);
+        blit(graphics, COVER, left + 141, top + 7, 186, 192, 0, 0);
+        blit(graphics, LEFT_PAGE, left + 7, top, 156, 195, 0, 0);
+        blit(graphics, RIGHT_PANEL, left + 163, top, 156, 195, 0, 0);
+        graphics.text(font, title, left + 42, top + 29, TEXT_COLOR, false);
+        if (bound) {
+            graphics.fill(left + 173, top + 20, left + 305, top + 103, 0xFF15141D);
+            graphics.text(font, Component.literal("Age preview unavailable"), left + 181, top + 47,
+                    0xFFE9DFCB, false);
+            graphics.text(font, Component.literal("Click to enter"), left + 205, top + 65,
+                    0xFFE9DFCB, false);
+        } else {
+            graphics.text(font, Component.literal("Bind a prototype Age"), left + 183, top + 39,
+                    TEXT_COLOR, false);
+        }
+        super.extractRenderState(graphics, mouseX, mouseY, partialTick);
+    }
+
+    @Override
+    public boolean mouseClicked(MouseButtonEvent event, boolean doubleClick) {
+        if (bound && event.button() == InputConstants.MOUSE_BUTTON_LEFT) {
+            int left = (width - WIDTH) / 2;
+            int top = (height - HEIGHT) / 2;
+            if (event.x() >= left + 173 && event.x() < left + 305
+                    && event.y() >= top + 20 && event.y() < top + 103) {
+                ClientPacketDistributor.sendToServer(new UseDescriptiveBookPayload(hand == InteractionHand.OFF_HAND));
+                onClose();
+                return true;
+            }
+        }
+        return super.mouseClicked(event, doubleClick);
+    }
+
+    @Override
+    public boolean isPauseScreen() {
+        return false;
+    }
+
+    private void bind() {
+        if (titleInput == null) return;
+        String name = titleInput.getValue().strip();
+        if (name.isEmpty()) return;
+        ClientPacketDistributor.sendToServer(new BindDescriptiveBookPayload(hand == InteractionHand.OFF_HAND, name));
+        onClose();
+    }
+
+    private static Identifier texture(String filename) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "textures/gui/" + filename);
+    }
+
+    private static void blit(GuiGraphicsExtractor graphics, Identifier texture, int x, int y,
+                             int width, int height, int u, int v) {
+        graphics.blit(RenderPipelines.GUI_TEXTURED, texture, x, y, u, v, width, height, 256, 256);
+    }
+}

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

@@ -0,0 +1,114 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.platform.InputConstants;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.network.BindLinkingBookPayload;
+import net.dnorberg.rivencraft.network.PortBookNetworking;
+import net.dnorberg.rivencraft.network.UseLinkingBookPayload;
+import net.minecraft.client.gui.GuiGraphicsExtractor;
+import net.minecraft.client.gui.components.Button;
+import net.minecraft.client.gui.components.EditBox;
+import net.minecraft.client.gui.screens.Screen;
+import net.minecraft.client.input.MouseButtonEvent;
+import net.minecraft.client.renderer.RenderPipelines;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.ItemStack;
+import net.neoforged.neoforge.client.network.ClientPacketDistributor;
+
+/** Minimal 26.3 book interaction using the Legacy artwork; live preview is not ported yet. */
+public final class PortLinkingBookScreen extends Screen {
+    private static final int WIDTH = 327;
+    private static final int HEIGHT = 199;
+    private static final int TEXT_COLOR = 0xFF3B281B;
+    private static final Identifier COVER = texture("bookui_cover.png");
+    private static final Identifier LEFT_PAGE = texture("notebook_pages.png");
+    private static final Identifier RIGHT_PANEL = texture("bookui_pager.png");
+
+    private final InteractionHand hand;
+    private final boolean bound;
+    private EditBox titleInput;
+
+    public PortLinkingBookScreen(InteractionHand hand, ItemStack book) {
+        super(book.getHoverName());
+        this.hand = hand;
+        bound = book.has(Rivencraft.LINK_BOOK_TARGET.get());
+    }
+
+    @Override
+    protected void init() {
+        if (bound) return;
+        int left = (width - WIDTH) / 2;
+        int top = (height - HEIGHT) / 2;
+        titleInput = new EditBox(font, left + 40, top + 69, 110, 20,
+                Component.literal("Linking Book name"));
+        titleInput.setMaxLength(PortBookNetworking.MAX_BOOK_TITLE_LENGTH);
+        titleInput.setHint(Component.literal("Name this link"));
+        addRenderableWidget(titleInput);
+        setInitialFocus(titleInput);
+        addRenderableWidget(Button.builder(Component.literal("Bind"), button -> bind())
+                .bounds(left + 40, top + 100, 53, 20).build());
+        addRenderableWidget(Button.builder(Component.literal("Cancel"), button -> onClose())
+                .bounds(left + 97, top + 100, 53, 20).build());
+    }
+
+    @Override
+    public void extractRenderState(GuiGraphicsExtractor graphics, int mouseX, int mouseY, float partialTick) {
+        int left = (width - WIDTH) / 2;
+        int top = (height - HEIGHT) / 2;
+        blit(graphics, COVER, left, top + 7, 34, 192, 152, 0);
+        blit(graphics, COVER, left + 34, top + 7, 103, 192, 49, 0);
+        blit(graphics, COVER, left + 137, top + 7, 4, 192, 45, 0);
+        blit(graphics, COVER, left + 141, top + 7, 186, 192, 0, 0);
+        if (bound) blit(graphics, LEFT_PAGE, left + 7, top, 156, 195, 0, 0);
+        blit(graphics, RIGHT_PANEL, left + 163, top, 156, 195, 0, 0);
+        graphics.text(font, title, left + 42, top + 29, TEXT_COLOR, false);
+        if (bound) {
+            graphics.fill(left + 173, top + 20, left + 305, top + 103, 0xFF15141D);
+            graphics.text(font, Component.literal("Destination preview"), left + 185, top + 47, 0xFFE9DFCB, false);
+            graphics.text(font, Component.literal("Click to link"), left + 205, top + 65, 0xFFE9DFCB, false);
+        } else {
+            graphics.text(font, Component.literal("Name this Linking Book"), left + 183, top + 39,
+                    TEXT_COLOR, false);
+        }
+        super.extractRenderState(graphics, mouseX, mouseY, partialTick);
+    }
+
+    @Override
+    public boolean mouseClicked(MouseButtonEvent event, boolean doubleClick) {
+        if (bound && event.button() == InputConstants.MOUSE_BUTTON_LEFT) {
+            int left = (width - WIDTH) / 2;
+            int top = (height - HEIGHT) / 2;
+            if (event.x() >= left + 173 && event.x() < left + 305
+                    && event.y() >= top + 20 && event.y() < top + 103) {
+                ClientPacketDistributor.sendToServer(new UseLinkingBookPayload(hand == InteractionHand.OFF_HAND));
+                onClose();
+                return true;
+            }
+        }
+        return super.mouseClicked(event, doubleClick);
+    }
+
+    @Override
+    public boolean isPauseScreen() {
+        return false;
+    }
+
+    private void bind() {
+        if (titleInput == null) return;
+        String name = titleInput.getValue().strip();
+        if (name.isEmpty()) return;
+        ClientPacketDistributor.sendToServer(new BindLinkingBookPayload(hand == InteractionHand.OFF_HAND, name));
+        onClose();
+    }
+
+    private static Identifier texture(String filename) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "textures/gui/" + filename);
+    }
+
+    private static void blit(GuiGraphicsExtractor graphics, Identifier texture, int x, int y,
+                             int width, int height, int u, int v) {
+        graphics.blit(RenderPipelines.GUI_TEXTURED, texture, x, y, u, v, width, height, 256, 256);
+    }
+}

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

@@ -0,0 +1,87 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.pipeline.RenderTarget;
+import com.mojang.blaze3d.systems.RenderSystem;
+import com.mojang.blaze3d.vertex.BufferBuilder;
+import com.mojang.blaze3d.vertex.ByteBufferBuilder;
+import com.mojang.blaze3d.vertex.DefaultVertexFormat;
+import com.mojang.blaze3d.vertex.MeshData;
+import com.mojang.renderpearl.api.buffers.GpuBuffer;
+import com.mojang.renderpearl.api.buffers.GpuBufferSlice;
+import com.mojang.renderpearl.api.pipeline.PrimitiveTopology;
+import java.util.Optional;
+import java.util.OptionalDouble;
+import net.minecraft.client.renderer.RenderPipelines;
+import net.minecraft.client.renderer.texture.DynamicTexture;
+import net.minecraft.util.RandomSource;
+import org.joml.Matrix4f;
+
+/** Legacy's six 48x48 noise faces, uploaded once per animation frame rather than per cell. */
+public final class PortStaticSky implements AutoCloseable {
+    private static final int GRID = 48;
+    private final DynamicTexture texture = new DynamicTexture("Rivencraft static sky", GRID * 6, GRID, false);
+    private final GpuBuffer cube = buildCube();
+    private long uploadedFrame = Long.MIN_VALUE;
+
+    public void render(RenderTarget target, GpuBufferSlice fog, long frame) {
+        if (uploadedFrame != frame) {
+            RandomSource random = RandomSource.create(frame);
+            var image = texture.getPixels();
+            for (int face = 0; face < 6; face++) {
+                for (int y = 0; y < GRID; y++) {
+                    for (int x = 0; x < GRID; x++) {
+                        int gray = 146 * (65 + random.nextInt(160)) / 255;
+                        image.setPixel(face * GRID + x, y, 0xff000000 | gray << 16 | gray << 8 | gray);
+                    }
+                }
+            }
+            texture.upload();
+            uploadedFrame = frame;
+        }
+        RenderSystem.setShaderFog(fog);
+        var indices = RenderSystem.getSequentialBuffer(PrimitiveTopology.QUADS);
+        var indexBuffer = indices.getBuffer(36);
+        var transform = RenderSystem.getDynamicUniforms().writeTransform(RenderSystem.getModelViewMatrixCopy());
+        try (var pass = RenderSystem.getDevice().createCommandEncoder().createRenderPass(
+                () -> "Rivencraft static sky", target.getColorTextureView(), Optional.empty(),
+                target.getDepthTextureView(), OptionalDouble.empty())) {
+            pass.setPipeline(RenderSystem.getCompiledPipeline(RenderPipelines.END_SKY));
+            RenderSystem.bindDefaultUniforms(pass);
+            pass.setUniform("DynamicTransforms", transform);
+            pass.setUniform("Sampler0", texture.getTextureView(), texture.getSampler());
+            pass.setVertexBuffer(0, cube.slice());
+            pass.setIndexBuffer(indexBuffer, indices.type());
+            pass.drawIndexed(36, 1, 0, 0, 0);
+        }
+    }
+
+    private static GpuBuffer buildCube() {
+        var format = DefaultVertexFormat.POSITION_TEX_COLOR;
+        try (var bytes = ByteBufferBuilder.exactlySized(24 * format.getVertexSize())) {
+            var builder = new BufferBuilder(bytes, PrimitiveTopology.QUADS, format);
+            for (int face = 0; face < 6; face++) {
+                var pose = new Matrix4f();
+                switch (face) {
+                    case 1 -> pose.rotationX((float) Math.PI / 2);
+                    case 2 -> pose.rotationX((float) -Math.PI / 2);
+                    case 3 -> pose.rotationX((float) Math.PI);
+                    case 4 -> pose.rotationZ((float) Math.PI / 2);
+                    case 5 -> pose.rotationZ((float) -Math.PI / 2);
+                }
+                float u0 = face / 6f, u1 = (face + 1) / 6f;
+                builder.addVertex(pose, -100, -100, -100).setUv(u0, 0).setColor(-1);
+                builder.addVertex(pose, -100, -100, 100).setUv(u0, 1).setColor(-1);
+                builder.addVertex(pose, 100, -100, 100).setUv(u1, 1).setColor(-1);
+                builder.addVertex(pose, 100, -100, -100).setUv(u1, 0).setColor(-1);
+            }
+            try (MeshData mesh = builder.buildOrThrow()) {
+                return RenderSystem.getDevice().createBuffer(() -> "Rivencraft static sky cube", 40, mesh.vertexBuffer());
+            }
+        }
+    }
+
+    @Override public void close() {
+        cube.close();
+        texture.close();
+    }
+}

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

@@ -0,0 +1,65 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import com.mojang.blaze3d.vertex.VertexConsumer;
+import com.mojang.serialization.MapCodec;
+import java.util.function.Consumer;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.PortAuthoredWriting;
+import net.minecraft.client.renderer.SubmitNodeCollector;
+import net.minecraft.client.renderer.rendertype.RenderTypes;
+import net.minecraft.client.renderer.special.SpecialModelRenderer;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.item.ItemStack;
+import org.joml.Vector3f;
+
+/** Flat item geometry textured with a page composed from its symbol stack. */
+public final class PortSymbolPageRenderer implements SpecialModelRenderer<PortSymbolPageRenderer.PageArt> {
+    @Override
+    public PageArt extractArgument(ItemStack stack) {
+        Identifier symbol = stack.get(Rivencraft.SYMBOL_PAGE_ID.get());
+        return symbol == null ? null : new PageArt(symbol,
+                stack.getOrDefault(Rivencraft.PAGE_GLYPH_ONLY.get(), false),
+                PortAuthoredWriting.isPageImplemented(symbol) ? 0xFFFFFFFF : 0xFFFF6666);
+    }
+
+    @Override
+    public void submit(PageArt art, PoseStack pose, SubmitNodeCollector collector,
+                       int light, int overlay, boolean hasFoil, int outlineColor) {
+        if (art == null) return;
+        Identifier texture = art.glyphOnly()
+                ? PortSymbolPageTextures.forPage(art.symbol())
+                : PortSymbolPageTextures.forItem(art.symbol());
+        collector.submitCustomGeometry(pose, RenderTypes.entityCutout(texture),
+                (matrix, vertices) -> {
+                    vertex(vertices, matrix, 0, 0, 0, 1, light, overlay, art.color());
+                    vertex(vertices, matrix, 1, 0, 1, 1, light, overlay, art.color());
+                    vertex(vertices, matrix, 1, 1, 1, 0, light, overlay, art.color());
+                    vertex(vertices, matrix, 0, 1, 0, 0, light, overlay, art.color());
+                });
+    }
+
+    @Override
+    public void getExtents(Consumer<org.joml.Vector3fc> extents) {
+        extents.accept(new Vector3f(0, 0, 0.5F));
+        extents.accept(new Vector3f(1, 1, 0.5F));
+    }
+
+    private static void vertex(VertexConsumer vertices, PoseStack.Pose pose,
+                               float x, float y, float u, float v, int light, int overlay, int color) {
+        vertices.addVertex(pose, x, y, 0.5F).setColor(color)
+                .setUv(u, v).setOverlay(overlay).setLight(light).setNormal(pose, 0, 0, 1);
+    }
+
+    public record PageArt(Identifier symbol, boolean glyphOnly, int color) {}
+
+    public record Unbaked() implements SpecialModelRenderer.Unbaked<PageArt> {
+        public static final Unbaked INSTANCE = new Unbaked();
+        public static final MapCodec<Unbaked> MAP_CODEC = MapCodec.unit(INSTANCE);
+
+        @Override public MapCodec<Unbaked> type() { return MAP_CODEC; }
+        @Override public SpecialModelRenderer<PageArt> bake(BakingContext context) {
+            return new PortSymbolPageRenderer();
+        }
+    }
+}

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

@@ -0,0 +1,189 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.platform.NativeImage;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.LinkedHashMap;
+import java.util.Locale;
+import java.util.Map;
+import java.util.Random;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.PortSymbolNumerals;
+import net.dnorberg.rivencraft.writing.PortSymbolPages;
+import net.minecraft.client.Minecraft;
+import net.minecraft.client.renderer.texture.DynamicTexture;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.packs.resources.ResourceManager;
+import net.minecraft.util.ARGB;
+
+/** The 1.21.1 Legacy-style glyph compositor adapted to 26.3's texture API. */
+public final class PortSymbolPageTextures {
+    private static final int SIZE = 128;
+    private static final int GLYPH = 51;
+    private static final int ITEM_SYMBOL_SIZE = 15;
+    private static final int NUMBER_GLYPH_SIZE = 64;
+    private static final int CACHE_LIMIT = 256;
+    private static final Identifier PAGE = texture("item/page");
+    private static final Identifier COMPONENTS = texture("gui/symbolcomponents");
+    private static final Identifier FALLBACK = texture("item/page_symbol");
+    private static final Map<String, Identifier> CACHE = new LinkedHashMap<>(16, .75F, true);
+    private static final Map<String, int[]> WORD_CACHE = new LinkedHashMap<>(16, .75F, true);
+    private static NativeImage page;
+    private static NativeImage components;
+    private static int nextId;
+
+    // WordData from Mystcraft Legacy 0.13.7.06, matching the 1.21.1 compositor.
+    private static final Map<String, int[]> WORDS = Map.ofEntries(
+            Map.entry("Terrain", new int[] {6,10,12,13,16,19,24,25,27}),
+            Map.entry("Form", new int[] {4,6,8,9,10,11,13,14,16,23}),
+            Map.entry("Tradition", new int[] {4,6,7,8,9,14,17,18,20}),
+            Map.entry("Flow", new int[] {4,7,12,13,17,18}),
+            Map.entry("Constraint", new int[] {5,6,9,11,13,20,22,23}),
+            Map.entry("Nature", new int[] {5,6,8,10,11,12,15,16,17,22}),
+            Map.entry("Sustain", new int[] {6,16,19,20,21,23}),
+            Map.entry("Ethereal", new int[] {4,6,8,13,14,16,18,21,23}),
+            Map.entry("Dynamic", new int[] {4,5,6,12,13,17,18,22,23}),
+            Map.entry("Cycle", new int[] {4,5,7,16,17,18}),
+            Map.entry("Balance", new int[] {4,6,9,10,16,19}),
+            Map.entry("Transform", new int[] {4,5,6,8,11,14,18,20,21}),
+            Map.entry("Time", new int[] {4,5,7,12,13,19,20,21,22,23}),
+            Map.entry("System", new int[] {10,12,14,15,16,20,21,22}),
+            Map.entry("Void", new int[] {4,5,6,16,17,18,23})
+    );
+
+    private PortSymbolPageTextures() {}
+
+    public static Identifier forItem(Identifier id) {
+        return forSymbol(id, true);
+    }
+
+    /** Transparent, full-size glyphs layered over the Binder's page atlas. */
+    public static Identifier forPage(Identifier id) {
+        return forSymbol(id, false);
+    }
+
+    private static Identifier forSymbol(Identifier id, boolean item) {
+        PortSymbolPages.Entry entry = PortSymbolPages.find(id);
+        if (entry == null) return FALLBACK;
+        String poem = entry.poem();
+        if (!poem.matches("[A-Za-z]+(?: [A-Za-z]+){3}")) poem = "";
+        String key = id + "|" + poem + (item ? "|item" : "|page");
+        Identifier cached = CACHE.get(key);
+        if (cached != null) return cached;
+        try {
+            loadSources(Minecraft.getInstance().getResourceManager());
+            NativeImage image = compose(id, poem, item);
+            Identifier location = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID,
+                    "generated/page_" + nextId++);
+            Minecraft.getInstance().getTextureManager().register(location,
+                    new DynamicTexture(() -> "Rivencraft symbol page " + id, image));
+            CACHE.put(key, location);
+            if (CACHE.size() > CACHE_LIMIT) {
+                String eldest = CACHE.keySet().iterator().next();
+                Minecraft.getInstance().getTextureManager().release(CACHE.remove(eldest));
+            }
+            return location;
+        } catch (IOException exception) {
+            Rivencraft.LOGGER.error("Could not compose symbol page {}", id, exception);
+            return FALLBACK;
+        }
+    }
+
+    public static void clear() {
+        var textures = Minecraft.getInstance().getTextureManager();
+        CACHE.values().forEach(textures::release);
+        CACHE.clear();
+        WORD_CACHE.clear();
+        if (page != null) page.close();
+        if (components != null) components.close();
+        page = null;
+        components = null;
+    }
+
+    private static void loadSources(ResourceManager manager) throws IOException {
+        if (page != null && components != null) return;
+        try (InputStream pageStream = manager.getResourceOrThrow(PAGE).open();
+             InputStream componentsStream = manager.getResourceOrThrow(COMPONENTS).open()) {
+            page = NativeImage.read(pageStream);
+            components = NativeImage.read(componentsStream);
+        }
+    }
+
+    private static NativeImage compose(Identifier id, String poem, boolean item) {
+        NativeImage image = new NativeImage(SIZE, SIZE, true);
+        if (item) {
+            for (int y = 0; y < SIZE; y++) for (int x = 0; x < SIZE; x++) {
+                image.setPixel(x, y, page.getPixel(x * page.getWidth() / SIZE,
+                        y * page.getHeight() / SIZE));
+            }
+        }
+        String numberPath = id.getPath().startsWith("number/")
+                ? id.getPath().substring("number/".length()) : "";
+        if (id.getNamespace().equals(Rivencraft.MOD_ID)
+                && numberPath.matches("(?:[0-9]|1[0-9]|2[0-4])")) {
+            int digit = Integer.parseInt(numberPath);
+            int glyphSize = item ? NUMBER_GLYPH_SIZE : GLYPH;
+            int origin = item ? (SIZE - glyphSize) / 2 : 38;
+            for (int component : PortSymbolNumerals.componentsForDigit(digit))
+                blendComponent(image, component, origin, origin, glyphSize);
+            return image;
+        }
+        String[] words = poem.isBlank() ? generatedWords(id) : poem.split(" ");
+        int[] offsetsX = {38, 77, 38, 0};
+        int[] offsetsY = {0, 38, 77, 38};
+        int glyphSize = item ? GLYPH * ITEM_SYMBOL_SIZE / 16 : GLYPH;
+        for (int word = 0; word < 4; word++) {
+            int x = item ? scaleForItem(offsetsX[word]) : offsetsX[word];
+            int y = item ? scaleForItem(offsetsY[word]) : offsetsY[word];
+            for (int component : glyphs(words[word]))
+                blendComponent(image, component, x, y, glyphSize);
+        }
+        return image;
+    }
+
+    private static void blendComponent(NativeImage image, int component, int x0, int y0, int size) {
+        int cellX = (component % 8) * 64;
+        int cellY = (component / 8) * 64;
+        for (int y = 0; y < size; y++) for (int x = 0; x < size; x++) {
+            int sourceX = cellX + x * 64 / size;
+            int sourceY = cellY + y * 64 / size;
+            // One source-pixel of coverage keeps the thin Legacy strokes legible
+            // when Minecraft shrinks this 128px composite to a 16px item icon.
+            int alpha = ARGB.alpha(components.getPixel(sourceX, sourceY));
+            if (sourceX > cellX) alpha = Math.max(alpha, ARGB.alpha(components.getPixel(sourceX - 1, sourceY)));
+            if (sourceX < cellX + 63) alpha = Math.max(alpha, ARGB.alpha(components.getPixel(sourceX + 1, sourceY)));
+            if (sourceY > cellY) alpha = Math.max(alpha, ARGB.alpha(components.getPixel(sourceX, sourceY - 1)));
+            if (sourceY < cellY + 63) alpha = Math.max(alpha, ARGB.alpha(components.getPixel(sourceX, sourceY + 1)));
+            if (alpha != 0) image.setPixel(x0 + x, y0 + y,
+                    ARGB.alphaBlend(image.getPixel(x0 + x, y0 + y),
+                            (alpha << 24) | 0x001A212B));
+        }
+    }
+
+    private static int scaleForItem(int coordinate) {
+        return SIZE / 2 + Math.round((coordinate - SIZE / 2F) * ITEM_SYMBOL_SIZE / 16F);
+    }
+
+    private static String[] generatedWords(Identifier id) {
+        String stem = id.toString();
+        return new String[] {stem + 'a', stem + 'b', stem + 'c', stem + 'd'};
+    }
+
+    private static int[] glyphs(String word) {
+        int[] known = WORDS.get(word);
+        if (known != null) return known;
+        String key = word.toLowerCase(Locale.ROOT);
+        int[] cached = WORD_CACHE.get(key);
+        if (cached != null) return cached;
+        Random random = new Random(key.hashCode());
+        int[] result = new int[random.nextInt(10) + 3];
+        for (int i = 0; i < result.length; i++) result[i] = random.nextInt(20) + 4;
+        WORD_CACHE.put(key, result);
+        if (WORD_CACHE.size() > CACHE_LIMIT) WORD_CACHE.remove(WORD_CACHE.keySet().iterator().next());
+        return result;
+    }
+
+    private static Identifier texture(String path) {
+        return Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "textures/" + path + ".png");
+    }
+}

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

@@ -0,0 +1,34 @@
+package net.dnorberg.rivencraft.client;
+
+import com.mojang.blaze3d.vertex.PoseStack;
+import java.util.List;
+import net.dnorberg.rivencraft.block.entity.StarFissureBlockEntity;
+import net.minecraft.client.renderer.SubmitNodeCollector;
+import net.minecraft.client.renderer.blockentity.AbstractEndPortalRenderer;
+import net.minecraft.client.renderer.blockentity.state.EndPortalRenderState;
+import net.minecraft.client.renderer.rendertype.RenderTypes;
+import net.minecraft.client.renderer.state.level.CameraRenderState;
+import net.minecraft.core.Direction;
+
+/** Retains 1.21.1's UP-at-zero/DOWN-at-one planes with the modern starfield renderer. */
+public final class StarFissureRenderer extends AbstractEndPortalRenderer<StarFissureBlockEntity, EndPortalRenderState> {
+    @Override
+    public EndPortalRenderState createRenderState() { return new EndPortalRenderState(); }
+
+    @Override
+    public void submit(EndPortalRenderState state, PoseStack pose, SubmitNodeCollector collector,
+                       CameraRenderState camera) {
+        if (state.facesToShow.contains(Direction.UP)) {
+            pose.pushPose();
+            pose.translate(0, -1, 0);
+            submitCube(List.of(Direction.UP), RenderTypes.endPortal(), pose, collector);
+            pose.popPose();
+        }
+        if (state.facesToShow.contains(Direction.DOWN)) {
+            pose.pushPose();
+            pose.translate(0, 1, 0);
+            submitCube(List.of(Direction.DOWN), RenderTypes.endPortal(), pose, collector);
+            pose.popPose();
+        }
+    }
+}

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

@@ -0,0 +1,7 @@
+package net.dnorberg.rivencraft.client;
+
+/** Carries the extracted animation frame without consulting the live world during drawing. */
+public interface StaticSkyState {
+    long rivencraft$staticFrame();
+    void rivencraft$staticFrame(long frame);
+}

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

@@ -0,0 +1,40 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.function.Consumer;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.TooltipFlag;
+import net.minecraft.world.item.component.TooltipDisplay;
+import net.minecraft.world.level.Level;
+
+/** Descriptive Book shell for the 26.3 prototype Age backend. */
+public final class DescriptiveBookItem extends Item {
+    public DescriptiveBookItem(Properties properties) {
+        super(properties);
+    }
+
+    @Override
+    public boolean isFoil(ItemStack stack) {
+        return stack.has(Rivencraft.AGE_BOOK_ID.get()) || super.isFoil(stack);
+    }
+
+    @Override
+    public InteractionResult use(Level level, Player player, InteractionHand hand) {
+        // The client opens the GUI. Binding and travel are validated on the
+        // server through dedicated packets; item use cannot bypass them.
+        return InteractionResult.SUCCESS;
+    }
+
+    @Override
+    public void appendHoverText(ItemStack stack, TooltipContext context, TooltipDisplay display,
+                                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));
+    }
+}

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

@@ -0,0 +1,76 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.function.Consumer;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.network.chat.Component;
+import net.minecraft.util.Prediction;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+import net.minecraft.world.item.TooltipFlag;
+import net.minecraft.world.item.component.TooltipDisplay;
+import net.minecraft.world.level.Level;
+
+/** A stackable 16-use vial; using it with paper in the other hand prepares a Link Panel. */
+public final class InkVialItem extends Item {
+    public static final int CAPACITY = 16;
+    // Match the 1.21.1 default; port the configurable cost with the full configuration system.
+    public static final int LINK_PANEL_COST = 2;
+
+    public InkVialItem(Properties properties) {
+        super(properties);
+    }
+
+    public static int remaining(ItemStack vial) {
+        return vial.getOrDefault(Rivencraft.INK_REMAINING.get(), CAPACITY);
+    }
+
+    @Override
+    public InteractionResult use(Level level, Player player, InteractionHand hand) {
+        InteractionHand paperHand = hand == InteractionHand.MAIN_HAND
+                ? InteractionHand.OFF_HAND : InteractionHand.MAIN_HAND;
+        ItemStack vial = player.getItemInHand(hand);
+        ItemStack paper = player.getItemInHand(paperHand);
+        int ink = remaining(vial);
+        if (!vial.is(Rivencraft.INK_VIAL.get()) || !paper.is(Items.PAPER)
+                || ink < LINK_PANEL_COST || ink > CAPACITY) {
+            return InteractionResult.PASS;
+        }
+        if (level.isClientSide()) return InteractionResult.SUCCESS;
+
+        ItemStack panel = PageItem.createLinkPanelPage();
+        int newInk = ink - LINK_PANEL_COST;
+        ItemStack spentVial = newInk == 0
+                ? new ItemStack(Items.GLASS_BOTTLE)
+                : new ItemStack(Rivencraft.INK_VIAL.get());
+        if (newInk > 0) spentVial.set(Rivencraft.INK_REMAINING.get(), newInk);
+
+        if (paper.getCount() == 1) {
+            player.setItemInHand(paperHand, panel);
+        } else {
+            paper.shrink(1);
+            giveOrDrop(player, panel);
+        }
+        if (vial.getCount() == 1) {
+            player.setItemInHand(hand, spentVial);
+        } else {
+            vial.shrink(1);
+            giveOrDrop(player, spentVial);
+        }
+        return InteractionResult.SUCCESS;
+    }
+
+    @Override
+    public void appendHoverText(ItemStack stack, TooltipContext context, TooltipDisplay display,
+                                Consumer<Component> tooltip, TooltipFlag flag) {
+        tooltip.accept(Component.translatable("item.rivencraft.ink_vial.remaining", remaining(stack), CAPACITY));
+        tooltip.accept(Component.translatable("item.rivencraft.ink_vial.usage"));
+    }
+
+    private static void giveOrDrop(Player player, ItemStack stack) {
+        if (!player.getInventory().add(stack)) player.drop(stack, false, Prediction.SERVER_ONLY);
+    }
+}

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

@@ -0,0 +1,40 @@
+package net.dnorberg.rivencraft.item;
+
+import com.mojang.serialization.Codec;
+import com.mojang.serialization.codecs.RecordCodecBuilder;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.codec.ByteBufCodecs;
+import net.minecraft.network.codec.StreamCodec;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerPlayer;
+
+/** Persistent destination captured when a 26.3 prototype Linking Book is bound. */
+public record LinkBookTarget(Identifier dimension, double x, double y, double z, float yaw, float pitch) {
+    public static final Codec<LinkBookTarget> CODEC = RecordCodecBuilder.create(instance -> instance.group(
+            Identifier.CODEC.fieldOf("dimension").forGetter(LinkBookTarget::dimension),
+            Codec.DOUBLE.fieldOf("x").forGetter(LinkBookTarget::x),
+            Codec.DOUBLE.fieldOf("y").forGetter(LinkBookTarget::y),
+            Codec.DOUBLE.fieldOf("z").forGetter(LinkBookTarget::z),
+            Codec.FLOAT.fieldOf("yaw").forGetter(LinkBookTarget::yaw),
+            Codec.FLOAT.fieldOf("pitch").forGetter(LinkBookTarget::pitch)
+    ).apply(instance, LinkBookTarget::new));
+    public static final StreamCodec<RegistryFriendlyByteBuf, LinkBookTarget> STREAM_CODEC = StreamCodec.composite(
+            Identifier.STREAM_CODEC, LinkBookTarget::dimension,
+            ByteBufCodecs.DOUBLE, LinkBookTarget::x,
+            ByteBufCodecs.DOUBLE, LinkBookTarget::y,
+            ByteBufCodecs.DOUBLE, LinkBookTarget::z,
+            ByteBufCodecs.FLOAT, LinkBookTarget::yaw,
+            ByteBufCodecs.FLOAT, LinkBookTarget::pitch,
+            LinkBookTarget::new);
+
+    public static LinkBookTarget at(ServerPlayer player) {
+        return new LinkBookTarget(player.level().dimension().identifier(),
+                player.getX(), player.getY(), player.getZ(), player.getYRot(), player.getXRot());
+    }
+
+    public boolean valid() {
+        return Double.isFinite(x) && Double.isFinite(y) && Double.isFinite(z)
+                && Float.isFinite(yaw) && Float.isFinite(pitch)
+                && Math.abs(x) <= 30_000_000 && Math.abs(z) <= 30_000_000;
+    }
+}

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

@@ -0,0 +1,29 @@
+package net.dnorberg.rivencraft.item;
+
+import com.mojang.serialization.Codec;
+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. */
+public record LinkProperties(int flags) {
+    public static final int DISARM = 1;
+    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 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(
+            (buffer, value) -> ByteBufCodecs.VAR_INT.encode(buffer, value.flags()),
+            buffer -> new LinkProperties(ByteBufCodecs.VAR_INT.decode(buffer)));
+
+    public LinkProperties {
+        if (flags < 0 || (flags & ~SUPPORTED) != 0) {
+            throw new IllegalArgumentException("Unsupported Link Panel flags: " + flags);
+        }
+    }
+
+    public boolean has(int flag) {
+        return (flags & flag) != 0;
+    }
+}

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

@@ -0,0 +1,35 @@
+package net.dnorberg.rivencraft.item;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.minecraft.core.particles.ParticleTypes;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.sounds.SoundEvent;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.world.phys.Vec3;
+
+/** Same successful-link feedback and sound precedence as the 1.21.1 target. */
+public final class LinkVisualEffects {
+    private LinkVisualEffects() {}
+
+    public static SoundEvent sound(LinkProperties properties, boolean portal) {
+        if (properties.has(LinkProperties.DISARM)) return Rivencraft.LINK_DISARM.get();
+        if (portal) return Rivencraft.LINK_PORTAL.get();
+        if (properties.has(LinkProperties.INTRA_LINKING)) return Rivencraft.LINK_INTRA.get();
+        return Rivencraft.LINK.get();
+    }
+
+    public static void play(ServerLevel source, Vec3 departure, ServerPlayer player,
+                            LinkProperties properties, boolean portal) {
+        SoundEvent event = sound(properties, portal);
+        burst(source, departure, event);
+        burst(player.level(), player.position(), event);
+    }
+
+    private static void burst(ServerLevel level, Vec3 position, SoundEvent event) {
+        level.playSound(null, position.x, position.y, position.z, event,
+                SoundSource.PLAYERS, 0.8F, level.getRandom().nextFloat() * 0.2F + 0.9F);
+        level.sendParticles(ParticleTypes.CLOUD, position.x, position.y, position.z,
+                50, 0.5, 1.0, 0.5, 0.005);
+    }
+}

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

@@ -0,0 +1,120 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.Set;
+import java.util.function.Consumer;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.age.AgeCatalogSync;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.ResourceKey;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.InteractionResult;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.TooltipFlag;
+import net.minecraft.world.item.component.TooltipDisplay;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.entity.item.ItemEntity;
+import net.minecraft.world.phys.Vec3;
+
+/** Handheld Linking Book; destination binding and travel are server-authoritative packets. */
+public final class LinkingBookItem extends Item {
+    public LinkingBookItem(Properties properties) {
+        super(properties);
+    }
+
+    @Override
+    public boolean isFoil(ItemStack stack) {
+        return stack.has(Rivencraft.LINK_BOOK_TARGET.get()) || super.isFoil(stack);
+    }
+
+    @Override
+    public InteractionResult use(Level level, Player player, InteractionHand hand) {
+        // Client-side interaction opens the book screen. A direct server-side
+        // item-use packet must never bypass the screen's validated payloads.
+        return InteractionResult.SUCCESS;
+    }
+
+    public static String travel(ServerPlayer player, ItemStack book) {
+        LinkBookTarget destination = book.get(Rivencraft.LINK_BOOK_TARGET.get());
+        LinkProperties properties = book.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE);
+        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)) {
+            return "Same-dimension linking requires an Intra-Linking page";
+        }
+        ServerLevel target = player.level().getServer().getLevel(
+                ResourceKey.create(Registries.DIMENSION, destination.dimension()));
+        if (target == null) return "Destination dimension is unavailable: " + destination.dimension();
+        if (!AgeCatalogSync.ready(player, destination.dimension())) {
+            return "Destination catalog not acknowledged by client";
+        }
+        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";
+        }
+        // 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(
+                destination.x() - player.getX(), destination.y() - player.getY(),
+                destination.z() - player.getZ()))) {
+            return "Linked destination is obstructed";
+        }
+        ServerLevel source = player.level();
+        Vec3 departure = player.position();
+        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());
+        return moved ? null : "Teleportation failed";
+    }
+
+    /** Link Panel effects are shared by Linking and Descriptive Books. */
+    public static void applySuccessfulLink(ServerPlayer player, LinkProperties properties,
+                                           ServerLevel source, Vec3 departure, Vec3 incoming, float destinationYaw) {
+        LinkVisualEffects.play(source, departure, player, properties, false);
+        if (properties.has(LinkProperties.MAINTAIN_MOMENTUM)) {
+            double speed = Math.hypot(incoming.x, incoming.z);
+            double yaw = Math.toRadians(destinationYaw);
+            player.setDeltaMovement(speed * Math.cos(yaw), incoming.y + 0.2,
+                    speed * Math.sin(yaw));
+        } else {
+            player.setDeltaMovement(Vec3.ZERO);
+        }
+        if (properties.has(LinkProperties.DISARM)) {
+            for (int slot = 0; slot < player.getInventory().getContainerSize(); slot++) {
+                ItemStack carried = player.getInventory().getItem(slot);
+                if (carried.isEmpty()) continue;
+                player.getInventory().setItem(slot, ItemStack.EMPTY);
+                ItemEntity dropped = new ItemEntity(source, departure.x, departure.y, departure.z,
+                        carried.copy());
+                dropped.setDefaultPickUpDelay();
+                source.addFreshEntity(dropped);
+            }
+            player.getInventory().setChanged();
+            player.containerMenu.broadcastChanges();
+        }
+    }
+
+    @Override
+    public void appendHoverText(ItemStack stack, TooltipContext context, TooltipDisplay display,
+                                Consumer<Component> tooltip, TooltipFlag flag) {
+        LinkBookTarget target = stack.get(Rivencraft.LINK_BOOK_TARGET.get());
+        tooltip.accept(Component.literal(target == null ? "Unbound (26.3 port preview)"
+                : "Destination: " + target.dimension() + " (" + (int) target.x() + ", "
+                + (int) target.y() + ", " + (int) target.z() + ")"));
+        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"));
+    }
+}

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

@@ -0,0 +1,97 @@
+package net.dnorberg.rivencraft.item;
+
+import java.util.function.Consumer;
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.writing.PortSymbolPages;
+import net.dnorberg.rivencraft.writing.PortAuthoredWriting;
+import net.minecraft.ChatFormatting;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.world.item.Item;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.TooltipFlag;
+import net.minecraft.world.item.component.TooltipDisplay;
+
+/** Shared Page item with persistent Link Panel and authored symbol variants. */
+public final class PageItem extends Item {
+    public PageItem(Properties properties) {
+        super(properties);
+    }
+
+    public static ItemStack createLinkPanelPage() {
+        return createLinkPanelPage(0);
+    }
+
+    public static ItemStack createLinkPanelPage(int flags) {
+        ItemStack stack = new ItemStack(Rivencraft.PAGE.get());
+        stack.set(Rivencraft.LINK_PANEL_PAGE.get(), true);
+        if (flags != 0) stack.set(Rivencraft.LINK_PROPERTIES.get(), new LinkProperties(flags));
+        return stack;
+    }
+
+    public static boolean isLinkPanel(ItemStack stack) {
+        return stack.is(Rivencraft.PAGE.get()) && stack.getOrDefault(Rivencraft.LINK_PANEL_PAGE.get(), false);
+    }
+
+    public static ItemStack createSymbolPage(Identifier id) {
+        if (PortSymbolPages.find(id) == null)
+            throw new IllegalArgumentException("Unknown bundled symbol " + id);
+        ItemStack stack = new ItemStack(Rivencraft.PAGE.get());
+        stack.set(Rivencraft.SYMBOL_PAGE_ID.get(), id);
+        return stack;
+    }
+
+    @Override
+    public Component getName(ItemStack stack) {
+        Component customName = stack.get(DataComponents.CUSTOM_NAME);
+        if (customName != null) return customName;
+        Identifier symbolId = stack.get(Rivencraft.SYMBOL_PAGE_ID.get());
+        if (symbolId != null) {
+            PortSymbolPages.Entry entry = PortSymbolPages.find(symbolId);
+            if (entry != null) {
+                Component name = Component.translatableWithFallback(
+                        entry.nameKey(), PortSymbolPages.fallbackName(symbolId));
+                return isCorrupted(symbolId) ? name.copy().withStyle(ChatFormatting.OBFUSCATED) : name;
+            }
+            return Component.translatableWithFallback("item.rivencraft.page.unresolved", "Unknown Symbol Page");
+        }
+        return Component.translatable(isLinkPanel(stack)
+                ? "item.rivencraft.page.link_panel" : "item.rivencraft.page.blank");
+    }
+
+    @Override
+    public void appendHoverText(ItemStack stack, TooltipContext context, TooltipDisplay display,
+                                Consumer<Component> tooltip, TooltipFlag flag) {
+        Identifier symbolId = stack.get(Rivencraft.SYMBOL_PAGE_ID.get());
+        if (symbolId != null) {
+            PortSymbolPages.Entry entry = PortSymbolPages.find(symbolId);
+            if (entry != null) {
+                Component description = Component.translatableWithFallback(
+                        entry.descriptionKey(), PortSymbolPages.fallbackName(symbolId));
+                tooltip.accept(isCorrupted(symbolId)
+                        ? description.copy().withStyle(ChatFormatting.GRAY, ChatFormatting.OBFUSCATED)
+                        : description.copy().withStyle(ChatFormatting.GRAY));
+            }
+            boolean implemented = PortAuthoredWriting.isPageImplemented(symbolId);
+            tooltip.accept(Component.translatable(implemented
+                    ? "item.rivencraft.page.symbol.implemented" : "item.rivencraft.page.symbol.unimplemented")
+                    .withStyle(implemented ? ChatFormatting.DARK_GRAY : ChatFormatting.RED));
+            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"));
+    }
+
+    private static boolean isCorrupted(Identifier id) {
+        return id.getNamespace().equals(Rivencraft.MOD_ID) && id.getPath().startsWith("corrupted/");
+    }
+}

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

@@ -0,0 +1,158 @@
+package net.dnorberg.rivencraft.menu;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.entity.InkMixerBlockEntity;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.world.Container;
+import net.minecraft.world.SimpleContainer;
+import net.minecraft.world.entity.player.Inventory;
+import net.minecraft.world.entity.player.Player;
+import net.minecraft.world.inventory.AbstractContainerMenu;
+import net.minecraft.world.inventory.ContainerInput;
+import net.minecraft.world.inventory.DataSlot;
+import net.minecraft.world.inventory.Slot;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.world.item.Items;
+
+/** Server-owned virtual output; taking it spends paper and the configured ink cost once. */
+public final class InkMixerMenu extends AbstractContainerMenu {
+    public static final int MODIFIER = InkMixerBlockEntity.SIZE;
+    public static final int RESULT = MODIFIER + 1;
+    private static final int PLAYER_START = RESULT + 1;
+    private final InkMixerBlockEntity mixer;
+    private final Container inputs;
+    private final SimpleContainer result = new SimpleContainer(1);
+    private final boolean clientSide;
+    private int inkRemaining;
+    private final int[] modifierChances = new int[3];
+
+    public InkMixerMenu(int id, Inventory inventory, RegistryFriendlyByteBuf data) {
+        this(id, inventory, inventory.player.level().getBlockEntity(data.readBlockPos())
+                instanceof InkMixerBlockEntity found ? found : null);
+    }
+
+    public InkMixerMenu(int id, Inventory inventory, InkMixerBlockEntity mixer) {
+        super(Rivencraft.INK_MIXER_MENU.get(), id);
+        this.mixer = mixer;
+        inputs = mixer == null ? new SimpleContainer(InkMixerBlockEntity.SIZE) : mixer;
+        clientSide = inventory.player.level().isClientSide();
+        addDataSlot(new DataSlot() {
+            @Override public int get() { return clientSide ? inkRemaining : mixer.inkRemaining(); }
+            @Override public void set(int value) { inkRemaining = value; }
+        });
+        for (int index = 0; index < modifierChances.length; index++) {
+            final int chanceIndex = index;
+            addDataSlot(new DataSlot() {
+                @Override public int get() {
+                    return clientSide ? modifierChances[chanceIndex] : mixer.modifierChancePermille(chanceIndex);
+                }
+                @Override public void set(int value) { modifierChances[chanceIndex] = value; }
+            });
+        }
+        addSlot(new MixerSlot(InkMixerBlockEntity.INK, 8, 27));
+        addSlot(new MixerSlot(InkMixerBlockEntity.PAPER, 8, 48));
+        addSlot(new MixerSlot(InkMixerBlockEntity.BOTTLES, 152, 27));
+        addSlot(new ModifierSlot(79, 40));
+        addSlot(new ResultSlot(152, 48));
+        for (int row = 0; row < 3; row++)
+            for (int column = 0; column < 9; column++)
+                addSlot(new Slot(inventory, column + row * 9 + 9, 8 + column * 18, 99 + row * 18));
+        for (int column = 0; column < 9; column++)
+            addSlot(new Slot(inventory, column, 8 + column * 18, 157));
+        refreshResult();
+    }
+
+    public int inkRemaining() { return inkRemaining; }
+    public int modifierChancePermille(int index) { return modifierChances[index]; }
+
+    @Override public void clicked(int slotId, int button, ContainerInput clickType, Player player) {
+        if (slotId == MODIFIER) {
+            if (!clientSide && stillValid(player) && clickType == ContainerInput.PICKUP
+                    && (button == 0 || button == 1)) {
+                ItemStack carried = getCarried();
+                int amount = button == 1 ? 1 : carried.getCount();
+                if (mixer.addModifier(carried, amount)) {
+                    setCarried(carried);
+                    refreshResult();
+                    broadcastChanges();
+                }
+            }
+            return;
+        }
+        super.clicked(slotId, button, clickType, player);
+        // In 26.3, recompute the virtual result in the same packet that changes
+        // paper or ink. Waiting for a later menu update can require a second click.
+        if (!clientSide) refreshResult();
+    }
+
+    @Override public boolean stillValid(Player player) {
+        return mixer != null && mixer.stillValid(player);
+    }
+
+    @Override public void broadcastChanges() {
+        refreshResult();
+        super.broadcastChanges();
+    }
+
+    private void refreshResult() {
+        if (clientSide) return;
+        ItemStack preview = mixer == null ? ItemStack.EMPTY : mixer.previewLinkPanel();
+        if (!ItemStack.matches(result.getItem(0), preview)) result.setItem(0, preview);
+    }
+
+    @Override public ItemStack quickMoveStack(Player player, int index) {
+        if (!stillValid(player) || index < 0 || index >= slots.size()) return ItemStack.EMPTY;
+        if (index == RESULT) {
+            refreshResult();
+            if (!mixer.canCreateLinkPanel()) return ItemStack.EMPTY;
+            ItemStack output = result.getItem(0).copy();
+            ItemStack remainder = output.copy();
+            if (!moveItemStackTo(remainder, PLAYER_START, slots.size(), true) || !remainder.isEmpty())
+                return ItemStack.EMPTY;
+            if (!mixer.consumeLinkPanelMaterials()) return ItemStack.EMPTY;
+            refreshResult();
+            return output;
+        }
+        Slot slot = slots.get(index);
+        if (!slot.hasItem()) return ItemStack.EMPTY;
+        ItemStack source = slot.getItem();
+        ItemStack original = source.copy();
+        boolean moved;
+        if (index < MODIFIER) moved = moveItemStackTo(source, PLAYER_START, slots.size(), true);
+        else if (source.is(Rivencraft.INK_VIAL.get()))
+            moved = moveItemStackTo(source, InkMixerBlockEntity.INK, InkMixerBlockEntity.INK + 1, false);
+        else if (source.is(Items.PAPER))
+            moved = moveItemStackTo(source, InkMixerBlockEntity.PAPER, InkMixerBlockEntity.PAPER + 1, false);
+        else moved = false;
+        if (!moved) return ItemStack.EMPTY;
+        if (source.isEmpty()) slot.setByPlayer(ItemStack.EMPTY);
+        else slot.setChanged();
+        refreshResult();
+        return original;
+    }
+
+    private final class MixerSlot extends Slot {
+        MixerSlot(int index, int x, int y) { super(inputs, index, x, y); }
+        @Override public boolean mayPlace(ItemStack stack) { return inputs.canPlaceItem(getContainerSlot(), stack); }
+    }
+
+    private static final class ModifierSlot extends Slot {
+        ModifierSlot(int x, int y) { super(new SimpleContainer(1), 0, x, y); }
+        @Override public boolean mayPlace(ItemStack stack) { return false; }
+        @Override public boolean mayPickup(Player player) { return false; }
+    }
+
+    private final class ResultSlot extends Slot {
+        ResultSlot(int x, int y) { super(result, 0, x, y); }
+        @Override public boolean mayPlace(ItemStack stack) { return false; }
+        @Override public boolean mayPickup(Player player) {
+            return clientSide ? hasItem() : stillValid(player) && mixer.canCreateLinkPanel();
+        }
+        @Override public void onTake(Player player, ItemStack stack) {
+            if (!clientSide && mixer.consumeLinkPanelMaterials()) {
+                refreshResult();
+            }
+            super.onTake(player, stack);
+        }
+    }
+}

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

@@ -0,0 +1,161 @@
+package net.dnorberg.rivencraft.menu;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.block.entity.PortBookBinderBlockEntity;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.network.PortBookNetworking;
+import net.dnorberg.rivencraft.writing.PortAuthoredWriting;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.RegistryFriendlyByteBuf;
+import net.minecraft.network.chat.Component;
+import net.minecraft.server.level.ServerPlayer;
+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;
+import net.minecraft.world.item.Items;
+
+/** Binder inputs persist in the block; assembling places the finished book on the cursor. */
+public final class PortBookBinderMenu extends AbstractContainerMenu {
+    public static final int STRIP_CLICK_BASE = 3000;
+    private final Container binder;
+    private final PortBookBinderBlockEntity blockEntity;
+    private final String initialTitle;
+
+    public PortBookBinderMenu(int id, Inventory inventory, RegistryFriendlyByteBuf data) {
+        this(id, inventory, inventory.player.level().getBlockEntity(data.readBlockPos())
+                instanceof PortBookBinderBlockEntity found ? found : null, data.readUtf(32));
+    }
+
+    public PortBookBinderMenu(int id, Inventory inventory, PortBookBinderBlockEntity blockEntity) {
+        this(id, inventory, blockEntity, blockEntity == null ? "" : blockEntity.title());
+    }
+
+    private PortBookBinderMenu(int id, Inventory inventory, PortBookBinderBlockEntity blockEntity, String title) {
+        super(Rivencraft.BOOK_BINDER_MENU.get(), id);
+        this.blockEntity = blockEntity;
+        initialTitle = title;
+        binder = blockEntity == null ? new SimpleContainer(PortBookBinderBlockEntity.SIZE) : blockEntity;
+        addSlot(new Slot(binder, PortBookBinderBlockEntity.COVER, 8, 27) {
+            @Override public boolean mayPlace(ItemStack stack) { return stack.is(Items.LEATHER); }
+        });
+        addSlot(new Slot(binder, PortBookBinderBlockEntity.PANEL, -1000, -1000) {
+            @Override public boolean mayPlace(ItemStack stack) { return PageItem.isLinkPanel(stack); }
+            @Override public int getMaxStackSize() { return 1; }
+        });
+        addSlot(new Slot(binder, PortBookBinderBlockEntity.OUTPUT, 152, 27) {
+            @Override public boolean mayPlace(ItemStack stack) { return false; }
+        });
+        for (int page = 0; page < PortBookBinderBlockEntity.PAGE_COUNT; page++) {
+            addSlot(new Slot(binder, PortBookBinderBlockEntity.FIRST_PAGE + page, -1000, -1000) {
+                @Override public boolean mayPlace(ItemStack stack) {
+                    return binder.canPlaceItem(getContainerSlot(), stack);
+                }
+                @Override public int getMaxStackSize() { return 1; }
+            });
+        }
+        addStandardInventorySlots(inventory, 8, 99);
+    }
+
+    @Override public boolean stillValid(Player player) {
+        return blockEntity != null && blockEntity.stillValid(player);
+    }
+
+    public String title() { return initialTitle; }
+
+    @Override public boolean clickMenuButton(Player player, int id) {
+        if (id < STRIP_CLICK_BASE || id > STRIP_CLICK_BASE + PortBookBinderBlockEntity.PAGE_COUNT
+                || !stillValid(player)) return false;
+        if (player.level().isClientSide()) return true;
+        int index = id - STRIP_CLICK_BASE;
+        ItemStack carried = getCarried();
+        if (!carried.isEmpty()) {
+            if (index == 0) {
+                if (!PageItem.isLinkPanel(carried)
+                        || !binder.getItem(PortBookBinderBlockEntity.PANEL).isEmpty()) return false;
+                binder.setItem(PortBookBinderBlockEntity.PANEL, carried.copyWithCount(1));
+            } else if (!blockEntity.insertPage(index - 1, carried.copyWithCount(1))) return false;
+            ItemStack remainder = carried.copy();
+            remainder.shrink(1);
+            setCarried(remainder);
+        } else {
+            ItemStack removed = index == 0
+                    ? binder.removeItem(PortBookBinderBlockEntity.PANEL, 1)
+                    : blockEntity.takePage(index - 1);
+            if (removed.isEmpty()) return false;
+            setCarried(removed);
+        }
+        broadcastChanges();
+        return true;
+    }
+
+    public void setTitle(ServerPlayer player, String value) {
+        if (stillValid(player) && value != null && value.length() <= PortBookNetworking.MAX_BOOK_TITLE_LENGTH)
+            blockEntity.setTitle(value);
+    }
+
+    public void assemble(ServerPlayer player, String title) {
+        if (!stillValid(player) || title.isBlank() || title.length() > PortBookNetworking.MAX_BOOK_TITLE_LENGTH
+                || !binder.getItem(PortBookBinderBlockEntity.OUTPUT).isEmpty()
+                || !PortAuthoredWriting.supports(blockEntity.symbolPages())
+                || !getCarried().isEmpty()) return;
+        ItemStack cover = binder.getItem(PortBookBinderBlockEntity.COVER);
+        ItemStack panel = binder.getItem(PortBookBinderBlockEntity.PANEL);
+        if (!cover.is(Items.LEATHER) || !PageItem.isLinkPanel(panel)) return;
+        blockEntity.setTitle(title);
+        ItemStack book = new ItemStack(Rivencraft.DESCRIPTIVE_BOOK.get());
+        var id = PortBookNetworking.createAge(player, title, blockEntity.symbolPages());
+        if (id == null) return;
+        book.set(Rivencraft.AGE_BOOK_ID.get(), id);
+        book.set(DataComponents.CUSTOM_NAME, Component.literal(title));
+        if (blockEntity.hasSymbolPages())
+            book.set(Rivencraft.BOOK_SYMBOLS.get(), blockEntity.symbolPages());
+        var modifiers = panel.get(Rivencraft.LINK_PROPERTIES.get());
+        if (modifiers != null) book.set(Rivencraft.LINK_PROPERTIES.get(), modifiers);
+        cover.shrink(1);
+        panel.shrink(1);
+        binder.setItem(PortBookBinderBlockEntity.COVER, cover);
+        binder.setItem(PortBookBinderBlockEntity.PANEL, panel);
+        blockEntity.clearSymbolPages();
+        setCarried(book);
+        broadcastChanges();
+    }
+
+    @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;
+        if (index >= PortBookBinderBlockEntity.FIRST_PAGE && index < PortBookBinderBlockEntity.SIZE) {
+            ItemStack page = slot.getItem().copy();
+            ItemStack remainder = page.copy();
+            if (!moveItemStackTo(remainder, PortBookBinderBlockEntity.SIZE, slots.size(), true)
+                    || !remainder.isEmpty()) return ItemStack.EMPTY;
+            blockEntity.takePage(index - PortBookBinderBlockEntity.FIRST_PAGE);
+            broadcastChanges();
+            return page;
+        }
+        ItemStack stack = slot.getItem();
+        ItemStack original = stack.copy();
+        boolean moved;
+        if (index < PortBookBinderBlockEntity.SIZE) {
+            moved = moveItemStackTo(stack, PortBookBinderBlockEntity.SIZE, slots.size(), true);
+        } else if (stack.is(Items.LEATHER)) {
+            moved = moveItemStackTo(stack, PortBookBinderBlockEntity.COVER,
+                    PortBookBinderBlockEntity.COVER + 1, false);
+        } else if (PageItem.isLinkPanel(stack)) {
+            moved = moveItemStackTo(stack, PortBookBinderBlockEntity.PANEL,
+                    PortBookBinderBlockEntity.PANEL + 1, false);
+        } else if (stack.is(Rivencraft.PAGE.get()) && stack.has(Rivencraft.SYMBOL_PAGE_ID.get())) {
+            moved = moveItemStackTo(stack, PortBookBinderBlockEntity.FIRST_PAGE,
+                    PortBookBinderBlockEntity.SIZE, false);
+        } else return ItemStack.EMPTY;
+        if (!moved) return ItemStack.EMPTY;
+        if (stack.isEmpty()) slot.setByPlayer(ItemStack.EMPTY);
+        else slot.setChanged();
+        slot.onTake(player, stack);
+        return original;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/mixin/AgeAmbientLightMixin.java

@@ -0,0 +1,23 @@
+package net.dnorberg.rivencraft.mixin;
+
+import com.llamalad7.mixinextras.injector.ModifyReturnValue;
+import net.dnorberg.rivencraft.age.PortLighting;
+import net.minecraft.world.level.Level;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.lighting.LevelLightEngine;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.injection.At;
+
+/** Ambient light contributes to effective brightness, not fake block/sky propagation. */
+@Mixin(LevelLightEngine.class)
+public abstract class AgeAmbientLightMixin {
+    @Shadow @Final protected LevelHeightAccessor levelHeightAccessor;
+
+    @ModifyReturnValue(method = "getRawBrightness", at = @At("RETURN"))
+    private int rivencraft$ambientBrightness(int brightness) {
+        return levelHeightAccessor instanceof Level level && PortLighting.isBright(level)
+                ? Math.max(brightness, 15) : brightness;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/mixin/AgeCarversMixin.java

@@ -0,0 +1,36 @@
+package net.dnorberg.rivencraft.mixin;
+
+import com.llamalad7.mixinextras.sugar.Local;
+import net.dnorberg.rivencraft.age.PortCarverPages;
+import net.dnorberg.rivencraft.age.PortFeatureChunkGenerator;
+import net.minecraft.server.level.WorldGenRegion;
+import net.minecraft.world.level.biome.BiomeManager;
+import net.minecraft.world.level.chunk.CarvingMask;
+import net.minecraft.world.level.chunk.ChunkAccess;
+import net.minecraft.world.level.levelgen.NoiseBasedChunkGenerator;
+import net.minecraft.world.level.levelgen.NoiseChunk;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.blending.Blender;
+import net.minecraft.world.level.levelgen.material.rule.MaterialRule;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+/** Merge authored geometry before vanilla consumes its mask with aquifer/surface rules. */
+@Mixin(NoiseBasedChunkGenerator.class)
+public abstract class AgeCarversMixin {
+    @Inject(method = "generateCarvers", at = @At(value = "INVOKE",
+            target = "Lnet/minecraft/world/level/chunk/CarvingMask;isEmpty()Z"))
+    private void rivencraft$authoredCarvers(ChunkAccess chunk, Blender blender, NoiseChunk noise,
+            RandomState random, BiomeManager biomes, WorldGenRegion region, MaterialRule material,
+            CallbackInfo ci, @Local CarvingMask mask) {
+        if (region == null) return;
+        var level = region.getLevel();
+        if (level.getChunkSource().getGenerator() instanceof PortFeatureChunkGenerator generator
+                && generator.base() == (Object) this && generator.terrainFeatures() != null) {
+            PortCarverPages.carve((NoiseBasedChunkGenerator) (Object) this, chunk, random,
+                    region.registryAccess(), generator.terrainFeatures().carvers(), level.getSeed(), mask);
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/mixin/AgeStructureBiomeMixin.java

@@ -0,0 +1,42 @@
+package net.dnorberg.rivencraft.mixin;
+
+import java.util.function.Predicate;
+import net.dnorberg.rivencraft.age.PortFeatureChunkGenerator;
+import net.dnorberg.rivencraft.age.PortStructurePages;
+import net.minecraft.core.Holder;
+import net.minecraft.core.RegistryAccess;
+import net.minecraft.world.level.ChunkPos;
+import net.minecraft.world.level.LevelHeightAccessor;
+import net.minecraft.world.level.biome.Biome;
+import net.minecraft.world.level.biome.BiomeSource;
+import net.minecraft.world.level.biome.Climate;
+import net.minecraft.world.level.chunk.ChunkGenerator;
+import net.minecraft.world.level.levelgen.RandomState;
+import net.minecraft.world.level.levelgen.structure.Structure;
+import net.minecraft.world.level.levelgen.structure.templatesystem.StructureTemplateManager;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
+
+/** Matches 1.21.1's explicit-page biome override, scoped only to authored Age structures. */
+@Mixin(Structure.class)
+public abstract class AgeStructureBiomeMixin {
+    // 26.3 jigsaw placement checks biome columns inside findGenerationPoint,
+    // before the final isValidBiome test. Set the predicate when constructing
+    // the context so both checks see the explicit-page override.
+    @ModifyArg(method = "generate", at = @At(value = "INVOKE",
+            target = "Lnet/minecraft/world/level/levelgen/structure/Structure$GenerationContext;<init>(Lnet/minecraft/core/RegistryAccess;Lnet/minecraft/world/level/chunk/ChunkGenerator;Lnet/minecraft/world/level/biome/BiomeSource;Lnet/minecraft/world/level/biome/Climate$Sampler;Lnet/minecraft/world/level/levelgen/RandomState;Lnet/minecraft/world/level/levelgen/structure/templatesystem/StructureTemplateManager;JLnet/minecraft/world/level/ChunkPos;Lnet/minecraft/world/level/LevelHeightAccessor;Ljava/util/function/Predicate;)V"),
+            index = 9)
+    private Predicate<Holder<Biome>> rivencraft$authoredBiome(
+            RegistryAccess registries, ChunkGenerator chunkGenerator, BiomeSource biomes,
+            Climate.Sampler sampler, RandomState random, StructureTemplateManager templates,
+            long seed, ChunkPos chunk, LevelHeightAccessor height, Predicate<Holder<Biome>> original) {
+        if (chunkGenerator instanceof PortFeatureChunkGenerator generator
+                && generator.terrainFeatures() != null
+                && PortStructurePages.authored((Structure) (Object) this, registries,
+                        generator.terrainFeatures().structures())) {
+            return biome -> true;
+        }
+        return original;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/mixin/StaticSkyRendererMixin.java

@@ -0,0 +1,53 @@
+package net.dnorberg.rivencraft.mixin;
+
+import com.mojang.blaze3d.pipeline.RenderTarget;
+import com.mojang.renderpearl.api.buffers.GpuBufferSlice;
+import net.dnorberg.rivencraft.client.PortStaticSky;
+import net.dnorberg.rivencraft.client.StaticSkyState;
+import net.minecraft.client.Camera;
+import net.minecraft.client.multiplayer.ClientLevel;
+import net.minecraft.client.renderer.SkyRenderer;
+import net.minecraft.client.renderer.state.level.SkyRenderState;
+import net.minecraft.world.level.dimension.DimensionType;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(SkyRenderer.class)
+public class StaticSkyRendererMixin {
+    @Shadow @Final private RenderTarget renderTarget;
+    @Unique private PortStaticSky rivencraft$staticSky;
+
+    @Inject(method = "extractRenderState", at = @At("TAIL"))
+    private void rivencraft$extract(ClientLevel level, float partialTicks, Camera camera,
+                                    SkyRenderState state, CallbackInfo ci) {
+        boolean enabled = level.dimensionTypeRegistration().unwrapKey().map(key ->
+                key.identifier().getNamespace().equals("rivencraft")
+                && key.identifier().getPath().endsWith("_sky_static")).orElse(false);
+        ((StaticSkyState) state).rivencraft$staticFrame(enabled ? level.getGameTime() / 2 : Long.MIN_VALUE);
+        // Only the extracted presentation uses END to schedule the sky pass. The actual
+        // dimension has NONE, so it never acquires End flashes or End gameplay behavior.
+        if (enabled) state.skybox = DimensionType.Skybox.END;
+    }
+
+    @Inject(method = "render", at = @At("HEAD"), cancellable = true)
+    private void rivencraft$render(GpuBufferSlice fog, SkyRenderState state, CallbackInfo ci) {
+        long frame = ((StaticSkyState) state).rivencraft$staticFrame();
+        if (frame == Long.MIN_VALUE) return;
+        if (rivencraft$staticSky == null) rivencraft$staticSky = new PortStaticSky();
+        rivencraft$staticSky.render(renderTarget, fog, frame);
+        ci.cancel();
+    }
+
+    @Inject(method = "close", at = @At("HEAD"))
+    private void rivencraft$close(CallbackInfo ci) {
+        if (rivencraft$staticSky != null) {
+            rivencraft$staticSky.close();
+            rivencraft$staticSky = null;
+        }
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/mixin/StaticSkyStateMixin.java

@@ -0,0 +1,19 @@
+package net.dnorberg.rivencraft.mixin;
+
+import net.dnorberg.rivencraft.client.StaticSkyState;
+import net.minecraft.client.renderer.state.level.SkyRenderState;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+@Mixin(SkyRenderState.class)
+public class StaticSkyStateMixin implements StaticSkyState {
+    @Unique private long rivencraft$frame = Long.MIN_VALUE;
+    public long rivencraft$staticFrame() { return rivencraft$frame; }
+    public void rivencraft$staticFrame(long frame) { rivencraft$frame = frame; }
+
+    @Inject(method = "reset", at = @At("TAIL"))
+    private void rivencraft$reset(CallbackInfo ci) { rivencraft$frame = Long.MIN_VALUE; }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/mixin/StructurePlacementAccessor.java

@@ -0,0 +1,17 @@
+package net.dnorberg.rivencraft.mixin;
+
+import java.util.Optional;
+import net.minecraft.world.level.levelgen.structure.placement.AbstractSpreadingStructurePlacement;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.gen.Accessor;
+
+/** Read-only placement settings for Age-local copies, never edits global placements. */
+@Mixin(AbstractSpreadingStructurePlacement.class)
+public interface StructurePlacementAccessor {
+    @Accessor("frequencyReductionMethod")
+    AbstractSpreadingStructurePlacement.FrequencyReductionMethod rivencraft$frequencyReductionMethod();
+    @Accessor("frequency") float rivencraft$frequency();
+    @Accessor("salt") int rivencraft$salt();
+    @Accessor("exclusionZone")
+    Optional<AbstractSpreadingStructurePlacement.ExclusionZone> rivencraft$exclusionZone();
+}

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

@@ -0,0 +1,17 @@
+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 AssembleBinderPayload(String title) implements CustomPacketPayload {
+    public static final Type<AssembleBinderPayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "assemble_binder"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, AssembleBinderPayload> STREAM_CODEC =
+            StreamCodec.composite(ByteBufCodecs.stringUtf8(32), AssembleBinderPayload::title,
+                    AssembleBinderPayload::new);
+    @Override public Type<AssembleBinderPayload> type() { return TYPE; }
+}

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

@@ -0,0 +1,22 @@
+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 BindDescriptiveBookPayload(boolean offhand, String title) implements CustomPacketPayload {
+    public static final Type<BindDescriptiveBookPayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "bind_descriptive_book"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, BindDescriptiveBookPayload> STREAM_CODEC =
+            StreamCodec.composite(ByteBufCodecs.BOOL, BindDescriptiveBookPayload::offhand,
+                    ByteBufCodecs.stringUtf8(32), BindDescriptiveBookPayload::title,
+                    BindDescriptiveBookPayload::new);
+
+    @Override
+    public Type<BindDescriptiveBookPayload> type() {
+        return TYPE;
+    }
+}

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

@@ -0,0 +1,22 @@
+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 BindLinkingBookPayload(boolean offhand, String title) implements CustomPacketPayload {
+    public static final Type<BindLinkingBookPayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "bind_linking_book"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, BindLinkingBookPayload> STREAM_CODEC = StreamCodec.composite(
+            ByteBufCodecs.BOOL, BindLinkingBookPayload::offhand,
+            ByteBufCodecs.stringUtf8(32), BindLinkingBookPayload::title,
+            BindLinkingBookPayload::new);
+
+    @Override
+    public Type<BindLinkingBookPayload> type() {
+        return TYPE;
+    }
+}

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

@@ -0,0 +1,171 @@
+package net.dnorberg.rivencraft.network;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.age.PortAgeTravel;
+import net.dnorberg.rivencraft.age.PortAgeTerrain;
+import net.dnorberg.rivencraft.age.RuntimeAgeBackend;
+import net.dnorberg.rivencraft.age.PortRandomAgeSelection;
+import net.dnorberg.rivencraft.item.LinkBookTarget;
+import net.dnorberg.rivencraft.item.LinkProperties;
+import net.dnorberg.rivencraft.item.LinkingBookItem;
+import net.dnorberg.rivencraft.menu.PortBookBinderMenu;
+import net.dnorberg.rivencraft.writing.PortAuthoredWriting;
+import net.minecraft.core.component.DataComponents;
+import net.minecraft.network.chat.Component;
+import net.minecraft.resources.Identifier;
+import net.minecraft.server.level.ServerPlayer;
+import net.minecraft.sounds.SoundEvents;
+import net.minecraft.sounds.SoundSource;
+import net.minecraft.world.InteractionHand;
+import net.minecraft.world.item.ItemStack;
+import net.minecraft.server.level.ServerLevel;
+import net.minecraft.world.phys.Vec3;
+import net.neoforged.neoforge.network.event.RegisterPayloadHandlersEvent;
+import java.util.Locale;
+import java.util.List;
+
+/** Server-authoritative handheld Linking Book binding and travel. */
+public final class PortBookNetworking {
+    public static final int MAX_BOOK_TITLE_LENGTH = 32;
+
+    private PortBookNetworking() {
+    }
+
+    public static void registerPayloads(RegisterPayloadHandlersEvent event) {
+        var registrar = event.registrar("1");
+        registrar.playToServer(BindLinkingBookPayload.TYPE, BindLinkingBookPayload.STREAM_CODEC,
+                (payload, context) -> {
+                    if (context.player() instanceof ServerPlayer player) bind(player, payload);
+                });
+        registrar.playToServer(UseLinkingBookPayload.TYPE, UseLinkingBookPayload.STREAM_CODEC,
+                (payload, context) -> {
+                    if (context.player() instanceof ServerPlayer player) use(player, payload);
+                });
+        registrar.playToServer(BindDescriptiveBookPayload.TYPE, BindDescriptiveBookPayload.STREAM_CODEC,
+                (payload, context) -> {
+                    if (context.player() instanceof ServerPlayer player) bindAge(player, payload);
+                });
+        registrar.playToServer(UseDescriptiveBookPayload.TYPE, UseDescriptiveBookPayload.STREAM_CODEC,
+                (payload, context) -> {
+                    if (context.player() instanceof ServerPlayer player) enterAge(player, payload);
+                });
+        registrar.playToServer(AssembleBinderPayload.TYPE, AssembleBinderPayload.STREAM_CODEC,
+                (payload, context) -> {
+                    if (context.player() instanceof ServerPlayer player
+                            && player.containerMenu instanceof PortBookBinderMenu menu) {
+                        menu.assemble(player, payload.title().strip());
+                    }
+                });
+        registrar.playToServer(SetBinderTitlePayload.TYPE, SetBinderTitlePayload.STREAM_CODEC,
+                (payload, context) -> {
+                    if (context.player() instanceof ServerPlayer player
+                            && player.containerMenu instanceof PortBookBinderMenu menu
+                            && menu.containerId == payload.containerId()) {
+                        menu.setTitle(player, payload.title());
+                    }
+                });
+    }
+
+    private static void bind(ServerPlayer player, BindLinkingBookPayload payload) {
+        ItemStack stack = player.getItemInHand(hand(payload.offhand()));
+        if (!stack.is(Rivencraft.LINKING_BOOK.get()) || stack.has(Rivencraft.LINK_BOOK_TARGET.get())) return;
+        String title = payload.title().strip();
+        if (title.isEmpty() || title.length() > MAX_BOOK_TITLE_LENGTH) return;
+        stack.set(Rivencraft.LINK_BOOK_TARGET.get(), LinkBookTarget.at(player));
+        stack.set(DataComponents.CUSTOM_NAME, Component.literal(title));
+        player.level().playSound(null, player.blockPosition(), SoundEvents.BOOK_PAGE_TURN,
+                SoundSource.PLAYERS, 1.0F, 1.0F);
+        player.sendOverlayMessage(Component.literal("Bound Linking Book: " + title));
+        player.containerMenu.broadcastChanges();
+    }
+
+    private static void use(ServerPlayer player, UseLinkingBookPayload payload) {
+        ItemStack stack = player.getItemInHand(hand(payload.offhand()));
+        if (!stack.is(Rivencraft.LINKING_BOOK.get())) return;
+        String failure = LinkingBookItem.travel(player, stack);
+        if (failure != null) player.sendOverlayMessage(Component.literal(failure));
+    }
+
+    private static void bindAge(ServerPlayer player, BindDescriptiveBookPayload payload) {
+        ItemStack stack = player.getItemInHand(hand(payload.offhand()));
+        if (!stack.is(Rivencraft.DESCRIPTIVE_BOOK.get()) || stack.has(Rivencraft.AGE_BOOK_ID.get())) return;
+        String title = payload.title().strip();
+        if (title.isEmpty() || title.length() > MAX_BOOK_TITLE_LENGTH) return;
+        Identifier id = createAge(player, title);
+        if (id == null) return;
+        stack.set(Rivencraft.AGE_BOOK_ID.get(), id);
+        stack.set(DataComponents.CUSTOM_NAME, Component.literal(title));
+        player.level().playSound(null, player.blockPosition(), SoundEvents.BOOK_PAGE_TURN,
+                SoundSource.PLAYERS, 1.0F, 1.0F);
+        player.sendOverlayMessage(Component.literal("Bound Descriptive Book: " + title));
+        player.containerMenu.broadcastChanges();
+    }
+
+    /** Shared name resolution and Age creation for handheld books and the Binder. */
+    public static Identifier createAge(ServerPlayer player, String title) {
+        return createAge(player, title, List.of());
+    }
+
+    public static Identifier createAge(ServerPlayer player, String title, List<Identifier> pages) {
+        if (title == null || title.isBlank() || title.length() > MAX_BOOK_TITLE_LENGTH) return null;
+        net.dnorberg.rivencraft.age.PortBiomePlan biomePlan;
+        try {
+            biomePlan = PortAuthoredWriting.biomePlan(pages, player.registryAccess());
+        } catch (IllegalArgumentException exception) {
+            player.sendOverlayMessage(Component.literal("Age writing unavailable: " + exception.getMessage()));
+            return null;
+        }
+        String base = title.toLowerCase(Locale.ROOT).replaceAll("[^a-z0-9._-]+", "_")
+                .replaceAll("^[_\\.-]+|[_\\.-]+$", "");
+        if (base.isEmpty()) base = "age";
+        var server = player.level().getServer();
+        String name = base;
+        int suffix = 2;
+        Identifier id = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age/" + name);
+        while (RuntimeAgeBackend.isNameTaken(server, id)) {
+            name = base + "_" + suffix++;
+            id = Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "age/" + name);
+        }
+        try {
+            long seed = player.getRandom().nextLong();
+            PortAgeTerrain terrain = PortAuthoredWriting.terrain(pages);
+            if (pages.isEmpty()) {
+                PortRandomAgeSelection.Selection random = PortRandomAgeSelection.select(server, seed);
+                terrain = random.terrain();
+                biomePlan = random.biomes();
+            }
+            var environment = net.dnorberg.rivencraft.age.PortEnvironmentSelection.resolve(pages, seed, terrain);
+            RuntimeAgeBackend.create(server, id, seed, biomePlan, terrain,
+                    PortAuthoredWriting.rockPlan(pages, seed),
+                    PortAuthoredWriting.vegetationPlan(pages),
+                    PortAuthoredWriting.dungeonCount(pages),
+                    PortAuthoredWriting.lakePlan(pages, seed),
+                    PortAuthoredWriting.terrainFeaturePlan(pages, seed),
+                    environment.weather(), environment.lighting(),
+                    net.dnorberg.rivencraft.age.PortSkyStyle.fromPages(pages));
+        } catch (IllegalArgumentException | IllegalStateException exception) {
+            player.sendOverlayMessage(Component.literal("Age creation failed: " + exception.getMessage()));
+            return null;
+        }
+        return id;
+    }
+
+    private static void enterAge(ServerPlayer player, UseDescriptiveBookPayload payload) {
+        ItemStack stack = player.getItemInHand(hand(payload.offhand()));
+        if (!stack.is(Rivencraft.DESCRIPTIVE_BOOK.get())) return;
+        Identifier id = stack.get(Rivencraft.AGE_BOOK_ID.get());
+        if (id == null) return;
+        ServerLevel source = player.level();
+        Vec3 departure = player.position();
+        Vec3 incoming = player.getDeltaMovement();
+        String failure = PortAgeTravel.enter(player, id);
+        if (failure != null) player.sendOverlayMessage(Component.literal(failure));
+        else LinkingBookItem.applySuccessfulLink(player,
+                stack.getOrDefault(Rivencraft.LINK_PROPERTIES.get(), LinkProperties.NONE),
+                source, departure, incoming, player.getYRot());
+    }
+
+    private static InteractionHand hand(boolean offhand) {
+        return offhand ? InteractionHand.OFF_HAND : InteractionHand.MAIN_HAND;
+    }
+}

ports/mc263/src/main/java/net/dnorberg/rivencraft/network/SetBinderTitlePayload.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 SetBinderTitlePayload(int containerId, String title) implements CustomPacketPayload {
+    public static final Type<SetBinderTitlePayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "set_binder_title"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, SetBinderTitlePayload> STREAM_CODEC =
+            StreamCodec.composite(ByteBufCodecs.VAR_INT, SetBinderTitlePayload::containerId,
+                    ByteBufCodecs.stringUtf8(32), SetBinderTitlePayload::title,
+                    SetBinderTitlePayload::new);
+    @Override public Type<SetBinderTitlePayload> type() { return TYPE; }
+}

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

@@ -0,0 +1,21 @@
+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 UseDescriptiveBookPayload(boolean offhand) implements CustomPacketPayload {
+    public static final Type<UseDescriptiveBookPayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "use_descriptive_book"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, UseDescriptiveBookPayload> STREAM_CODEC =
+            StreamCodec.composite(ByteBufCodecs.BOOL, UseDescriptiveBookPayload::offhand,
+                    UseDescriptiveBookPayload::new);
+
+    @Override
+    public Type<UseDescriptiveBookPayload> type() {
+        return TYPE;
+    }
+}

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

@@ -0,0 +1,20 @@
+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 UseLinkingBookPayload(boolean offhand) implements CustomPacketPayload {
+    public static final Type<UseLinkingBookPayload> TYPE = new Type<>(
+            Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, "use_linking_book"));
+    public static final StreamCodec<RegistryFriendlyByteBuf, UseLinkingBookPayload> STREAM_CODEC = StreamCodec.composite(
+            ByteBufCodecs.BOOL, UseLinkingBookPayload::offhand, UseLinkingBookPayload::new);
+
+    @Override
+    public Type<UseLinkingBookPayload> type() {
+        return TYPE;
+    }
+}

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

@@ -0,0 +1,71 @@
+package net.dnorberg.rivencraft.registry;
+
+import net.dnorberg.rivencraft.Rivencraft;
+import net.dnorberg.rivencraft.item.PageItem;
+import net.dnorberg.rivencraft.item.LinkProperties;
+import net.dnorberg.rivencraft.writing.PortSymbolPages;
+import net.minecraft.core.registries.Registries;
+import net.minecraft.network.chat.Component;
+import net.minecraft.world.item.CreativeModeTab;
+import net.neoforged.bus.api.IEventBus;
+import net.neoforged.neoforge.registries.DeferredRegister;
+
+/** Only items already ported to 26.3 appear here. */
+public final class ModCreativeTabs {
+    private static final DeferredRegister<CreativeModeTab> TABS =
+            DeferredRegister.create(Registries.CREATIVE_MODE_TAB, Rivencraft.MOD_ID);
+
+    static {
+        TABS.register("rivencraft", () -> CreativeModeTab.builder()
+                .title(Component.translatable("itemGroup.rivencraft"))
+                .icon(() -> Rivencraft.DESCRIPTIVE_BOOK.get().getDefaultInstance())
+                .displayItems((parameters, output) -> {
+                    output.accept(Rivencraft.DESCRIPTIVE_BOOK.get());
+                    output.accept(Rivencraft.LINKING_BOOK.get());
+                    output.accept(Rivencraft.CRYSTAL_BLOCK_ITEM.get());
+                    output.accept(Rivencraft.BUDDING_CRYSTAL_ITEM.get());
+                    output.accept(Rivencraft.SMALL_CRYSTAL_BUD_ITEM.get());
+                    output.accept(Rivencraft.MEDIUM_CRYSTAL_BUD_ITEM.get());
+                    output.accept(Rivencraft.LARGE_CRYSTAL_BUD_ITEM.get());
+                    output.accept(Rivencraft.CRYSTAL_CLUSTER_ITEM.get());
+                    output.accept(Rivencraft.CRYSTAL_SHARD.get());
+                    output.accept(Rivencraft.INK_VIAL.get());
+                    output.accept(Rivencraft.BOOK_BINDER_ITEM.get());
+                    output.accept(Rivencraft.INK_MIXER_ITEM.get());
+                })
+                .build());
+        TABS.register("rivencraft_link_pages", () -> CreativeModeTab.builder()
+                .title(Component.translatable("itemGroup.rivencraft.pages.link"))
+                .icon(PageItem::createLinkPanelPage)
+                .displayItems((parameters, output) -> {
+                    int[] flags = {LinkProperties.DISARM, LinkProperties.MAINTAIN_MOMENTUM,
+                            LinkProperties.INTRA_LINKING};
+                    for (int combination = 0; combination < 8; combination++) {
+                        int selected = 0;
+                        for (int bit = 0; bit < flags.length; bit++)
+                            if ((combination & (1 << bit)) != 0) selected |= flags[bit];
+                        output.accept(PageItem.createLinkPanelPage(selected));
+                    }
+                })
+                .build());
+        for (String category : PortSymbolPages.categories()) {
+            String path = category.substring(category.indexOf(':') + 1);
+            TABS.register("rivencraft_pages_" + path, () -> CreativeModeTab.builder()
+                    .title(Component.translatableWithFallback("itemGroup.rivencraft.pages." + path,
+                            "Rivencraft " + PortSymbolPages.fallbackName(
+                                    net.minecraft.resources.Identifier.fromNamespaceAndPath(Rivencraft.MOD_ID, path))
+                                    + " Pages"))
+                    .icon(() -> PortSymbolPages.icon(category))
+                    .displayItems((parameters, output) ->
+                            PortSymbolPages.pages(category, parameters.holders()).forEach(output::accept))
+                    .build());
+        }
+    }
+
+    private ModCreativeTabs() {
+    }
+
+    public static void register(IEventBus modEventBus) {
+        TABS.register(modEventBus);
+    }
+}