Merge origin/main; a fallback pool's guaranteed elements are tried too

Main's YUNG rules (#3bc38cebb: priority, min_required_depth, ignore_bounds,
the start not counted) stay as they are in `Rules`; Lithostitched's limited
and guaranteed elements keep their own `Limit` beside them, checked by both
vanilla and YUNG draws, and `Pick` carries either one's key.

rdbtCVS's review: the vanilla candidates listed only the target pool's
guaranteed entries and filtered every pool's out of the draw, so a fallback's
guaranteed elements were never tried, at the most depth either. Each pool now
lists its own guaranteed entries first when it is reached
(`a_fallbacks_guaranteed_entries_are_tried`). docs/mods.md says so.

The structure layout harness keeps main's yung-probe profiles beside
lithostitched-probe.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

.claude/skills/vanilla-parity/SKILL.md

@@ -0,0 +1,76 @@
+---
+name: vanilla-parity
+description: Fix a Horizon bug or gap so it behaves 1:1 like vanilla 26.3, starting from the port ledger (tools/port_ledger.py) instead of grepping. Use for any issue, Discord report or PR that makes Horizon match vanilla: "X doesn't work like in Java", a missing sound, particle, animation, mob behaviour, block rule, screen or packet.
+---
+
+# Vanilla parity with the port ledger
+
+The port ledger pairs every vanilla method with the Rust fn that ports it (or says it is missing, or needs
+no port) and lists where a port isn't wired like vanilla. Ask it first; grep only for what it can't answer.
+Full reference: `docs/port-ledger.md`.
+
+## 0. Have a fresh ledger
+
+```sh
+python3 tools/port_ledger.py build          # ~20 s; again after pulling main
+```
+
+It needs the vanilla jar (the launcher's `versions/26.3/26.3.jar`, or `--jar`) and/or the lab's decompiled
+sources (`python3 tools/lab.py decompile`, or `--sources DIR`). If `build` says it has no vanilla code, run
+the lab first; don't guess vanilla from memory.
+
+## 1. From the report to the code
+
+```sh
+python3 tools/port_ledger.py issue 3236                      # a GitHub issue number
+python3 tools/port_ledger.py issue "mooshroom stays red after lightning"   # or the report's text
+```
+
+It ranks the vanilla classes the report names and lists, per class, its Rust home files, where each method is
+ported, and the known gaps (`missing` rows from the verdict map, seam/client/drift gaps). Often the cause is
+already written there ("Type is not saved"). Then drill in:
+
+```sh
+python3 tools/port_ledger.py where MushroomCow.readAdditionalSaveData   # ports, callers, callees, gaps
+python3 tools/port_ledger.py class MushroomCow                          # every method: where, or missing
+python3 tools/port_ledger.py what crates/horizon-client/src/mobs/farm.rs:120   # which vanilla method a fn ports
+```
+
+A ledger answer is a lead, not a verdict: about 1 in 12 map rows is wrong. Read the vanilla method (path and
+line are in the output) and the Rust fn before changing anything.
+
+## 2. Port it the vanilla way
+
+- Translate the vanilla method, don't reinvent it: same order of operations, same constants, the same random
+  draws in the same order (`horizon_core::random`), Java `Math` through `horizon_core::jmath`.
+- Open the fn's doc with the vanilla method it ports: `` /// `MushroomCow.readAdditionalSaveData`: ... ``.
+  That one line is what makes the next agent find it.
+- Fix the path players run: single player is a client of the integrated server, so server logic lives in
+  `game/lan*.rs` and `src/lan/`, and what only the client's copy shows (particles, local sounds, hand
+  animation) must be reached from `game/remote*.rs`. A fix on the old in-frame path alone fixes nothing.
+- Look at the neighbours the ledger lists for the same class: a `client` or `seam` gap next to your fix is
+  usually the same bug on the other path.
+
+## 3. Before the PR
+
+```sh
+python3 tools/port_ledger.py check --base origin/main
+```
+
+It lists the ports your branch touches with their open gaps, citations to add, stale citations, and (against
+the base) the gaps the branch closes and opens. Close what belongs to your fix, cite what you ported, leave
+no new stale citation. If you ported a method the verdict map called `missing`, change its row in
+`tools/port_map/*.tsv` to `port` with the fn (`file.rs::Owner::fn`) and run
+`python3 tools/port_ledger.py map-check tools/port_map/<file>.tsv`.
+
+Then the usual: the harness for the area (`docs/architecture.md`), `cargo check`/tests per `AGENTS.md`, and
+a small PR that says which vanilla method it now matches.
+
+## Finding work
+
+```sh
+python3 tools/port_ledger.py gaps --kind seam      # ported on two paths, wired on one: the best leads
+python3 tools/port_ledger.py gaps --kind client    # client-only effects the server path never reaches
+python3 tools/port_ledger.py gaps --kind drift     # a port missing a sound, particle, item or constant
+rg -n "player:" tools/port_map/*.tsv               # missing behaviour a player would see
+```

.dockerignore

@@ -2,7 +2,6 @@
 target/
 .local/
 **/node_modules/
-website/
 benchmarks/
 packs/
 mods/

.gitattributes

@@ -2,5 +2,5 @@
 # where Git for Windows' core.autocrlf would check them out with CRLF.
 docs/launcher-commands.md text eol=lf
 docs/horizon-ctl-commands.md text eol=lf
-website/src/tokens.css text eol=lf
+crates/horizon-theme/tokens.css text eol=lf
 docs/api/*-reference.md text eol=lf

.githooks/pre-commit

@@ -1,2 +1,11 @@
 #!/bin/sh
-exec python3 tools/check_public_tree.py
+# Git for Windows puts a `python3` on PATH that is only the Microsoft Store
+# stub: it prints "Python" and exits non-zero, so the hook fails with no other
+# output. Use the first name that actually runs Python 3.
+for py in python3 python py; do
+    if "$py" -c "import sys; sys.exit(sys.version_info < (3,))" >/dev/null 2>&1; then
+        exec "$py" tools/check_public_tree.py
+    fi
+done
+echo "check_public_tree: no working Python 3 found" >&2
+exit 1

.githooks/pre-push

@@ -1,2 +1,11 @@
 #!/bin/sh
-exec python3 tools/check_public_tree.py --history
+# Git for Windows puts a `python3` on PATH that is only the Microsoft Store
+# stub: it prints "Python" and exits non-zero, so the hook fails with no other
+# output. Use the first name that actually runs Python 3.
+for py in python3 python py; do
+    if "$py" -c "import sys; sys.exit(sys.version_info < (3,))" >/dev/null 2>&1; then
+        exec "$py" tools/check_public_tree.py --pre-push
+    fi
+done
+echo "check_public_tree: no working Python 3 found" >&2
+exit 1

.github/pull_request_template.md

@@ -1,7 +1,21 @@
+<!-- Opened by an AI agent? First line: "> 🤖 Opened by <your GitHub login>'s AI agent (<tool, model>), not by <your GitHub login> personally." Use your own login, not someone else's. -->
+
 ## What and why
 
 <!-- What this changes, and why. Link the issue it fixes ("Fixes #123"). -->
 
+## Kind
+
+<!-- Tick one: it sets the pull request's label (CONTRIBUTING.md "Pull requests"). -->
+
+- [ ] parity: Horizon now does what vanilla 26.3 does
+- [ ] bug: a crash or a breakage
+- [ ] perf: faster, or less memory
+- [ ] feature: something new for players (listed under New in the release notes)
+- [ ] extra: Horizon-only, off by default
+- [ ] tooling: tools, CI, tests, harnesses
+- [ ] docs
+
 ## Vanilla reference
 
 <!-- The vanilla classes and methods this follows (tools/rea_vanilla.py), and the harness that checks it.

.github/trusted-reviewers.txt

@@ -0,0 +1,9 @@
+# Trusted reviewers: one list for two things (docs/release-flow.md "Trusted reviewers").
+# - `/nightly 2640 2642` picks the pull requests the Nightly holds (tools/ci/nightly_set.py);
+# - `/close`, `/reopen`, `/label`, `/unlabel` triage issues and pull requests (tools/ci/triage_command.py).
+# Ludovic is always allowed and isn't listed. One GitHub login per line, with who added it and when. Removing a
+# line revokes that login at once. A line with only `paused` stops both for every reviewer (Ludovic's still work).
+kacpherek    # added by Ludovic, 2026-10-27
+rdbtCVS      # added by Ludovic, 2026-10-27
+Online5277   # added by Ludovic, 2026-10-27 (his top three by merged pull requests)
+levzzz5154   # added by Ludovic, 2026-10-28 (Horizon Team; author of horizon-mixins)

.github/workflows/cancel-on-close.yml

@@ -16,12 +16,14 @@ jobs:
           GH_TOKEN: ${{ github.token }}
           REPO: ${{ github.repository }}
           BRANCH: ${{ github.event.pull_request.head.ref }}
-          SHA: ${{ github.event.pull_request.head.sha }}
+          HEAD_REPO: ${{ github.event.pull_request.head.repo.full_name }}
         run: |
+          # Every head the pull request had, not only its last: a run-parity label added on an older head left that
+          # run queued after the merge (#3104, 2026-10-29). Its branch in its own repository names its runs (another
+          # fork can have a branch of the same name).
           for status in queued in_progress waiting pending requested; do
-            gh run list -R "$REPO" --branch "$BRANCH" --status "$status" --limit 100 \
-              --json databaseId,event,headSha \
-              -q ".[] | select(.event == \"pull_request\" and .headSha == \"$SHA\") | .databaseId"
+            gh api -X GET "repos/$REPO/actions/runs" -f branch="$BRANCH" -f event=pull_request -f status="$status" \
+              -f per_page=100 --jq ".workflow_runs[] | select(.head_repository.full_name == \"$HEAD_REPO\") | .id"
           done | sort -u | while read -r id; do
             gh run cancel -R "$REPO" "$id" || true
           done

.github/workflows/ci.yml

@@ -3,7 +3,8 @@ name: checks
 # check main requires, so it never has a condition: a skipped job counts as passed, and every run of this workflow
 # must report a real verify (a pull request that changes no Rust finishes it in seconds instead).
 # parity: the vanilla harnesses a pull request's changes can affect, on the Mac mini's runner, which holds the
-# maintainer's own Minecraft files (Horizon never downloads the game); .github/workflows/parity.yml. A fork's pull
+# maintainer's own Minecraft files (Horizon never downloads the game); .github/workflows/parity.yml. Only for a pull
+# request that changes a harness, oracle, probe or the runner: the rest are checked on main by parity-main. A fork's pull
 # request runs it only when a maintainer adds the run-parity label (.github/workflows/run-parity.yml), so labels
 # never start this workflow. See docs/release-flow.md.
 on:
@@ -50,7 +51,7 @@ jobs:
         if: steps.rust.outputs.required != 'false'
         run: |
           sudo apt-get update && sudo apt-get install -y --no-install-recommends libasound2-dev libudev-dev
-          rustup toolchain install stable --profile minimal --component rustfmt --component clippy --target wasm32-unknown-unknown
+          rustup toolchain install stable --profile minimal --component rustfmt --component clippy
       # Dependencies and the workspace's own build, saved from main's runs (pull requests read main's cache).
       - uses: Swatinem/rust-cache@v2
         if: steps.rust.outputs.required != 'false'
@@ -61,8 +62,7 @@ jobs:
         if: steps.rust.outputs.required != 'false'
         run: |
           cargo +stable fmt --all -- --check
-          # With the game's code mods (on in every release build, off by default).
-          cargo +stable clippy --workspace --all-targets --features horizon-client/mods -- -D warnings
+          cargo +stable clippy --workspace --all-targets -- -D warnings
           # The server build (released as horizon-engine): the game without sound or controllers.
           cargo +stable clippy -p horizon-client --all-targets --no-default-features -- -D warnings
       # Libraries, binaries and integration tests, then doc tests: not the ~275 examples, which clippy above already
@@ -70,14 +70,83 @@ jobs:
       - name: Test Rust core and voxel kernel correctness
         if: steps.rust.outputs.required != 'false'
         run: |
-          cargo +stable test --workspace --lib --bins --tests --features horizon-client/mods,horizon-mods/pack
-          cargo +stable test --workspace --doc --features horizon-client/mods,horizon-mods/pack
-  parity:
+          cargo +stable test --workspace --lib --bins --tests
+          # The full content-root tests (#[ignore]d: minutes each on a laptop). The same build as above; they need the
+          # prepared vanilla data, so without it they pass at once.
+          cargo +stable test --workspace --lib mod_content::tests:: -- --ignored
+          cargo +stable test --workspace --doc
+  # The launcher is its own workspace (launcher/Cargo.toml), so verify's cargo runs never build it. A pull request that
+  # changes it or a crate it builds is checked here, and so is every push to main: two pull requests can each pass
+  # alone and break it together (#2059 and the registry ratings did, 2026-10-26).
+  launcher:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: Does this pull request change the launcher or a crate it builds?
+        if: github.event_name == 'pull_request'
+        id: launcher
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha }}
+        run: python3 tools/ci/rust_changes.py --launcher "$BASE_SHA" "$HEAD_SHA" >> "$GITHUB_OUTPUT"
+      - name: Install Rust and the headers GPUI links against
+        if: steps.launcher.outputs.required != 'false'
+        run: |
+          sudo apt-get update && sudo apt-get install -y --no-install-recommends libxkbcommon-x11-dev libwayland-dev \
+            libx11-xcb-dev libfontconfig-dev libvulkan-dev libasound2-dev libudev-dev
+          rustup toolchain install stable --profile minimal --component rustfmt --component clippy
+      - uses: Swatinem/rust-cache@v2
+        if: steps.launcher.outputs.required != 'false'
+        with:
+          workspaces: launcher
+          shared-key: launcher
+          save-if: ${{ github.ref == 'refs/heads/main' }}
+      - name: Check the launcher's formatting, lint and tests
+        if: steps.launcher.outputs.required != 'false'
+        working-directory: launcher
+        run: |
+          cargo +stable fmt --check
+          cargo +stable clippy --all-targets --locked -- -D warnings
+          cargo +stable test --locked --lib
+  # Most pull requests leave the harnesses to parity-main, which runs them on main a batch of merges at a time
+  # (.github/workflows/parity-main.yml; releases wait for it). A pull request still runs them itself when it changes
+  # a harness, an oracle, a probe or the runner, or carries the run-parity label (run-parity.yml, when it is added).
+  parity-scope:
     if: github.event_name == 'pull_request' && github.event.pull_request.head.repo.full_name == github.repository
+    runs-on: ubuntu-latest
+    outputs:
+      run: ${{ steps.scope.outputs.run }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+          persist-credentials: false
+      - id: scope
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha }}
+          LABELS: ${{ join(github.event.pull_request.labels.*.name, ' ') }}
+        run: |
+          changed=$(git diff --name-only "$(git merge-base "$BASE_SHA" HEAD)" HEAD)
+          harness=$(grep -E '^(tools/test_[a-z0-9_]+_parity\.py|tools/(parity[a-z_]*|lab)\.py|tools/parity_hosts\.json|mods/horizon/src/test/|crates/[^/]+/examples/|crates/horizon-client/src/game/[a-z_]*(fixture|harness)\.rs|\.github/workflows/parity[a-z-]*\.yml)' <<< "$changed" || true)
+          if [ -n "$harness" ] || [[ " $LABELS " == *" run-parity "* ]]; then
+            echo "run=true" >> "$GITHUB_OUTPUT"
+            echo "The pull request runs its harnesses: ${harness:-label run-parity}"
+          else
+            echo "run=false" >> "$GITHUB_OUTPUT"
+            echo "No harness, oracle, probe or runner change: parity-main checks this on main"
+          fi
+  parity:
+    needs: parity-scope
+    if: needs.parity-scope.outputs.run == 'true'
     uses: ./.github/workflows/parity.yml
     with:
       base: ${{ github.event.pull_request.base.sha }}
       head: ${{ github.event.pull_request.head.sha }}
+      full: ${{ contains(github.event.pull_request.labels.*.name, 'full-parity') }}
   # Horizon never downloads the game. These jobs need a self-hosted Linux runner
   # (label horizon-game) holding the maintainer's own copy: the official launcher's
   # game directory in HORIZON_MINECRAFT_DIR and the pinned server jar in

.github/workflows/claim-command.yml

@@ -0,0 +1,76 @@
+name: claim command
+# `/claim` and `/unclaim` comments: anyone takes an issue before working on it, and a daily run releases the claims
+# older than 5 days that no open pull request links (CONTRIBUTING.md "Claim before you start",
+# tools/ci/claim_command.py).
+#
+# Why no pull request's code runs here, though the token can write:
+# - `issue_comment` and `schedule` always run this file from main, whoever comments and wherever.
+# - It checks out main's script and list only, never a pull request; it reads threads through the API.
+# - The comment's text and author reach the script as env vars, never in a shell line. The token stays in the step
+#   and can only write issues (assignees, comments, reactions).
+on:
+  issue_comment:
+    types: [created]
+  schedule:
+    - cron: "23 5 * * *"
+  workflow_dispatch:
+permissions:
+  contents: read
+jobs:
+  command:
+    # Every other comment skips here, before a runner starts. Pull requests are answered by the script.
+    if: >-
+      github.event_name == 'issue_comment' && github.event.comment.user.type != 'Bot' && (
+      startsWith(github.event.comment.body, '/claim') ||
+      startsWith(github.event.comment.body, '/unclaim') ||
+      startsWith(github.event.comment.body, '🤖 Agent: /claim') ||
+      startsWith(github.event.comment.body, '🤖 Agent: /unclaim'))
+    # One command per issue at a time, so two `/claim`s can't both find it free. On the job, not the workflow:
+    # the skipped runs of ordinary comments must not cancel a waiting one.
+    concurrency:
+      group: claim-${{ github.event.issue.number }}
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      contents: read
+      issues: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+          persist-credentials: false
+          sparse-checkout: |
+            .github/trusted-reviewers.txt
+            tools/ci/nightly_set.py
+            tools/ci/claim_command.py
+          sparse-checkout-cone-mode: false
+      - name: Run the command
+        env:
+          GH_TOKEN: ${{ github.token }}
+          BODY: ${{ github.event.comment.body }}
+          AUTHOR: ${{ github.event.comment.user.login }}
+          ISSUE: ${{ github.event.issue.number }}
+          COMMENT_ID: ${{ github.event.comment.id }}
+          REPO: ${{ github.repository }}
+        run: python3 tools/ci/claim_command.py command
+  release:
+    if: github.event_name != 'issue_comment' && github.repository == 'horizon-rust/horizon'
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: read
+      issues: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+          persist-credentials: false
+          sparse-checkout: |
+            tools/ci/nightly_set.py
+            tools/ci/claim_command.py
+          sparse-checkout-cone-mode: false
+      - name: Release stale claims
+        env:
+          GH_TOKEN: ${{ github.token }}
+          REPO: ${{ github.repository }}
+        run: python3 tools/ci/claim_command.py release

.github/workflows/game-build.yml

@@ -0,0 +1,290 @@
+name: game build
+# Builds the game for every platform from `ref`: the Java exporters, then Linux and the Linux server and Windows on
+# GitHub, macOS on the Mac mini's runner with a 1500-frame offscreen run of a new world (smoke-test.json). Called by
+# release.yml (the releases) and nightly-build.yml (the opt-in Nightly), always from main's copy of this file: the
+# caller's commit, never the one being built. It holds no secrets: signing the checksums is the callers' own job,
+# which never runs what this one built. See docs/release-flow.md.
+on:
+  workflow_call:
+    inputs:
+      ref:
+        description: The commit to build
+        type: string
+        required: true
+      version:
+        description: The version built in (HORIZON_VERSION), e.g. 0.2.81 or nightly-2026-10-28
+        type: string
+        required: true
+      nightly:
+        description: A nightly's "<date> <short sha>" (HORIZON_NIGHTLY), shown by the game; empty for a release
+        type: string
+        default: ''
+      trusted:
+        # Only release.yml says true: it builds main. A nightly can hold pull requests nobody reviewed yet, whose
+        # build scripts and tests run here and could rewrite target/, the cargo home or a compiler cache. So an
+        # untrusted build never runs on the release runner, never saves the Rust cache (its key is its own anyway),
+        # and a trusted one never reads the machine's shared sccache, which pull requests' jobs write
+        # (tests/test_nightly.py pins all of it).
+        description: The source is main (a release); false for anything else (a nightly)
+        type: boolean
+        default: false
+      developer_id:
+        description: Sign the macOS programs with Developer ID and notarize the zip (the runner's keychain)
+        type: boolean
+        default: true
+permissions:
+  contents: read
+jobs:
+  exporters:
+    # This runner holds the maintainer's own pinned Minecraft jars. Only our classes leave it. An untrusted build
+    # goes to the Mac mini's nightly runner (macOS + horizon-nightly: ludovics-mac-mini-nightly, beside the one that
+    # runs pull requests' parity jobs, so a nightly never waits behind their queue), never the release runner
+    # (MAC_RUNNER: ludovics-mac-mini-release) nor parity-main's.
+    runs-on: ${{ inputs.trusted && vars.MAC_RUNNER || fromJSON('["self-hosted", "macOS", "horizon-nightly"]') }}
+    # Three full preparations (two isolated, one batched) besides the compile.
+    timeout-minutes: 60
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.ref }}
+          persist-credentials: false
+          clean: true
+      - uses: dtolnay/rust-toolchain@stable
+      - run: bash tools/ci/runner-env.sh
+        env:
+          HORIZON_NO_SCCACHE: ${{ inputs.trusted && '1' || '' }}
+      - run: bash tools/ci/vanilla-data.sh
+      - name: Compile and validate original exporters against the pinned jars
+        shell: bash
+        run: |
+          set -euo pipefail
+          # target/ is gone after the clean checkout, and vanilla-data.sh builds the preparer only when it
+          # prepares afresh.
+          cargo build --release --locked -p horizon-prepare
+          # Compiled here, never taken from the runner's shared preparations: pull requests' parity jobs
+          # write those (vanilla-data.sh links .local/exporters to them).
+          rm -rf .local/exporters
+          bundle=$(target/release/horizon-prepare compile-exporters --root "$PWD" | tail -1)
+          mkdir -p exporters
+          cp -R "$bundle/server" "$bundle/client" "$bundle/manifest.json" exporters/
+          # Only our classes and their manifest leave this runner.
+          stray=$(find exporters -type f ! -path exporters/manifest.json \
+            ! \( -name '*.class' \( -path 'exporters/server/dev/horizonlab/parity/*' -o -path 'exporters/client/dev/horizonlab/parity/*' \) \))
+          [ -z "$stray" ] || { echo "::error::not one of our classes: $stray"; exit 1; }
+          python3 tools/check_prepare_exporters.py --binary target/release/horizon-prepare
+      - uses: actions/upload-artifact@v4
+        with:
+          name: original-exporters
+          path: exporters/
+          if-no-files-found: error
+          retention-days: 3
+
+  build:
+    needs: exporters
+    name: build ${{ matrix.name }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: linux
+            os: ubuntu-22.04
+            dir: horizon-linux-x86_64
+            asset: horizon-linux-x86_64.tar.gz
+            # The server build too: packaging/server/install.sh installs it on Linux.
+            server_dir: horizon-server-linux-x86_64
+            server_asset: horizon-server-linux-x86_64.tar.gz
+          - name: windows
+            os: windows-latest
+            dir: horizon-windows-x64
+            asset: horizon-windows-x64.zip
+            exe: .exe
+            # The C runtime linked in, so the game runs without the Visual C++ redistributable.
+            rustflags: -C target-feature=+crt-static
+          - name: macos
+            mac: true
+            dir: horizon-macos-arm64
+            asset: horizon-macos-arm64.zip
+    runs-on: ${{ matrix.mac && (inputs.trusted && vars.MAC_RUNNER || fromJSON('["self-hosted", "macOS", "horizon-nightly"]')) || matrix.os }}
+    # Notarizing the zip can take a few minutes.
+    timeout-minutes: ${{ matrix.mac && 60 || 40 }}
+    env:
+      RUSTFLAGS: ${{ matrix.rustflags }}
+      # The release's version, built in (horizon_core::release): --version, user agents, crash reports and
+      # telemetry say it. No version-bump commits.
+      HORIZON_VERSION: ${{ inputs.version }}
+      # A nightly's date and commit ("2026-10-28 0c02067"), which the game shows; empty for a release.
+      HORIZON_NIGHTLY: ${{ inputs.nightly }}
+    defaults:
+      run:
+        shell: bash
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.ref }}
+          persist-credentials: false
+          # Always from a clean checkout, the Mac mini's runner too: its work folder is shared with pull requests'
+          # parity jobs, and nothing they leave (target/, an untracked .cargo/config.toml, a build script's output)
+          # may end up in a release. target/ is rebuilt from scratch; .local/ is relinked by vanilla-data.sh, which
+          # keeps its preparations outside the checkout.
+          clean: true
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+        if: runner.environment == 'github-hosted'
+        with:
+          # A release restores only what a release saved: an untrusted build has its own key and saves nothing.
+          shared-key: ${{ inputs.trusted && 'release' || 'nightly' }}-${{ matrix.name }}
+          save-if: ${{ inputs.trusted }}
+      - name: ALSA and udev headers
+        if: runner.os == 'Linux'
+        run: sudo apt-get update && sudo apt-get install -y --no-install-recommends libasound2-dev libudev-dev
+      - name: Build the client, horizon-ctl, horizon-prepare and horizon-server
+        run: cargo build --release --locked -p horizon-client --bin horizon-client --bin horizon-ctl -p horizon-prepare --bin horizon-prepare -p horizon-server --bin horizon-server
+      - name: Every program the release folder takes was built
+        run: |
+          for binary in horizon-client horizon-ctl horizon-prepare horizon-server; do
+            test -f "target/release/$binary${{ matrix.exe }}" || { echo "::error::target/release/$binary${{ matrix.exe }} is missing"; exit 1; }
+          done
+      - name: The signing keychain, unlocked
+        if: runner.os == 'macOS' && vars.MACOS_SIGN_IDENTITY != '' && inputs.developer_id
+        env:
+          MACOS_SIGN_IDENTITY: ${{ vars.MACOS_SIGN_IDENTITY }}
+        run: packaging/macos/keychain.sh unlock
+      - name: Signed with Developer ID and the hardened runtime
+        # Before the checks below, so they run the programs as players will.
+        if: runner.os == 'macOS' && vars.MACOS_SIGN_IDENTITY != '' && inputs.developer_id
+        env:
+          MACOS_SIGN_IDENTITY: ${{ vars.MACOS_SIGN_IDENTITY }}
+        run: |
+          for binary in horizon-client horizon-ctl horizon-prepare horizon-server; do
+            codesign --force --options runtime --timestamp --keychain "$MACOS_SIGN_KEYCHAIN" \
+              --identifier "dev.horizon.${binary#horizon-}" --sign "$MACOS_SIGN_IDENTITY" "target/release/$binary"
+            codesign --verify --strict --verbose=2 "target/release/$binary"
+          done
+      - name: Only system libraries
+        # Windows: no non-system DLL (a "DLL not found" dialog on some players' machines). Linux: the standard
+        # loader and libraries every desktop distribution has. macOS: only the system's own libraries.
+        run: |
+          for binary in horizon-client horizon-ctl horizon-prepare horizon-server; do
+            file="target/release/$binary${{ matrix.exe }}"
+            if [[ "$RUNNER_OS" == macOS ]]; then
+              others=$(otool -L "$file" | tail -n +2 | awk '{print $1}' | grep -v -E '^(/usr/lib/|/System/Library/)' || true)
+              [[ -z "$others" ]] || { echo "::error::$binary links $others"; exit 1; }
+            else
+              ${{ runner.os == 'Windows' && 'python' || 'python3' }} tools/check_imports.py "$file"
+            fi
+          done
+      - name: Every program starts
+        run: |
+          set -euo pipefail
+          bin=target/release
+          "$bin/horizon-client${{ matrix.exe }}" --help | grep -q -- '--resources'
+          "$bin/horizon-ctl${{ matrix.exe }}" --help > /dev/null
+          "$bin/horizon-prepare${{ matrix.exe }}" --help | grep -q -- '--minecraft-dir'
+          # The version is the release's.
+          for binary in horizon-prepare horizon-server; do
+            out=$("$bin/$binary${{ matrix.exe }}" --version | tr -d '\r')
+            echo "$out"
+            [[ "$out" == "$binary $HORIZON_VERSION" ]] || { echo "::error::expected $binary $HORIZON_VERSION"; exit 1; }
+          done
+      - name: Tools from the runner
+        if: runner.environment == 'self-hosted'
+        env:
+          HORIZON_NO_SCCACHE: ${{ inputs.trusted && '1' || '' }}
+        run: bash tools/ci/runner-env.sh
+      - name: Resources prepared from the runner's own Minecraft
+        if: runner.environment == 'self-hosted'
+        run: bash tools/ci/vanilla-data.sh
+      - name: The game runs (offscreen, a new world, 1500 frames)
+        if: runner.environment == 'self-hosted'
+        run: |
+          set -euo pipefail
+          # From a scratch folder: the game keeps its saves and options in the folder it starts in.
+          home="$RUNNER_TEMP/horizon-smoke"
+          rm -rf "$home" && mkdir -p "$home"
+          version=$(sed -n 's/.*"version": *"\([^"]*\)".*/\1/p' research-lock.json | head -1)
+          client="$PWD/target/release/horizon-client"
+          resources="$PWD/.local/horizon-client/$version"
+          (cd "$home" && HORIZON_HOME="$home" HORIZON_NO_AUDIO=1 "$client" --resources "$resources" --offscreen \
+            --world smoke --seed 1 --render-distance 4 --world-frames 1500 --timeout-seconds 180 \
+            --smoke-report "$home/smoke.json" > "$home/client.log" 2>&1) || { tail -40 "$home/client.log"; exit 1; }
+          python3 - "$home/smoke.json" <<'EOF'
+          import json, sys
+          report = json.load(open(sys.argv[1]))
+          print(json.dumps(report))
+          if report.get("error") is not None or report.get("frames", 0) < 1500 or not report.get("chunks") \
+                  or not report.get("meshed_sections") or not report.get("player"):
+              sys.exit("the smoke run did not draw a world")
+          EOF
+          # Published with the release; the publish job checks it again before it publishes anything.
+          cp "$home/smoke.json" "$RUNNER_TEMP/smoke-test.json"
+      - uses: actions/upload-artifact@v4
+        if: runner.environment == 'self-hosted'
+        with:
+          name: smoke-test.json
+          path: ${{ runner.temp }}/smoke-test.json
+          if-no-files-found: error
+          retention-days: 3
+      - uses: actions/download-artifact@v4
+        with:
+          name: original-exporters
+          path: exporters
+      - name: Package
+        run: |
+          set -euo pipefail
+          cargo run --locked -p xtask -- package "target/release/horizon-client${{ matrix.exe }}" "dist/${{ matrix.dir }}"
+          cd dist
+          rm -f "${{ matrix.asset }}"
+          case "${{ matrix.asset }}" in
+            *.tar.gz) tar czf "${{ matrix.asset }}" "${{ matrix.dir }}" ;;
+            *) if [[ "$RUNNER_OS" == Windows ]]; then 7z a -tzip "${{ matrix.asset }}" "${{ matrix.dir }}" > /dev/null
+               else
+                 # Without resource forks and extended attributes: plain ditto adds an
+                 # AppleDouble `._` file beside every file that has any.
+                 ditto -c -k --norsrc --noextattr --noqtn --keepParent "${{ matrix.dir }}" "${{ matrix.asset }}"
+                 if unzip -Z1 "${{ matrix.asset }}" | grep -E '(^|/)(\._|__MACOSX/)'; then
+                   echo "::error::macOS metadata files in ${{ matrix.asset }}"; exit 1
+                 fi
+               fi ;;
+          esac
+          ls -l "${{ matrix.asset }}"
+      - name: Notarized
+        # A zip of programs can't be stapled: Gatekeeper asks Apple the first time each one runs.
+        if: runner.os == 'macOS' && vars.MACOS_SIGN_IDENTITY != '' && inputs.developer_id
+        run: |
+          for binary in horizon-client horizon-ctl horizon-prepare horizon-server; do
+            codesign --verify --strict "dist/${{ matrix.dir }}/$binary"
+          done
+          packaging/macos/notarize.sh "dist/${{ matrix.asset }}"
+      - uses: actions/upload-artifact@v4
+        with:
+          name: ${{ matrix.asset }}
+          path: dist/${{ matrix.asset }}
+          if-no-files-found: error
+          retention-days: 3
+      - name: The server build (the game without sound or controllers, as horizon-engine)
+        if: matrix.server_asset
+        run: |
+          set -euo pipefail
+          # After the client is packaged: target/release/horizon-client is rebuilt without the audio and
+          # controllers features, so it needs neither libasound nor libudev (minimal server images lack them).
+          cargo build --release --locked -p horizon-client --no-default-features --bin horizon-client
+          cargo run --locked -p xtask -- package-server target/release/horizon-client "dist/${{ matrix.server_dir }}"
+          folder="dist/${{ matrix.server_dir }}"
+          python3 tools/check_imports.py --server "$folder/horizon-engine" "$folder/horizon-server" "$folder/horizon-prepare"
+          "$folder/horizon-engine" --help | grep -q -- '--resources'
+          [[ "$("$folder/horizon-server" --version)" == "horizon-server $HORIZON_VERSION" ]]
+          cd dist
+          rm -f "${{ matrix.server_asset }}"
+          tar czf "${{ matrix.server_asset }}" "${{ matrix.server_dir }}"
+          ls -l "${{ matrix.server_asset }}"
+      - uses: actions/upload-artifact@v4
+        if: matrix.server_asset
+        with:
+          name: ${{ matrix.server_asset }}
+          path: dist/${{ matrix.server_asset }}
+          if-no-files-found: error
+          retention-days: 3
+      - name: The signing keychain, locked again
+        if: always() && runner.os == 'macOS' && vars.MACOS_SIGN_IDENTITY != '' && inputs.developer_id
+        run: packaging/macos/keychain.sh lock
+

.github/workflows/launcher.yml

@@ -192,9 +192,11 @@ jobs:
           retry "$launcher" install latest
           "$launcher" versions --installed
           "$launcher" links --json
-          clients=("$HORIZON_LAUNCHER_HOME"/versions/v*/horizon-client*)
+          # `install latest` is the Nightly since #3342 (versions/nightly-<date>-<commit>), a vX.Y.Z before.
+          clients=("$HORIZON_LAUNCHER_HOME"/versions/*/horizon-client*)
           client="${clients[0]}"
           echo "installed client: $client"
+          [[ -f "$client" ]] || { echo "::error::no game installed under versions/"; exit 1; }
           # The game's Linux build is the game's to keep portable (release.yml checks it): a
           # release linked to a Nix store is a warning here, not a broken launcher.
           soft() { if [[ "$RUNNER_OS" == "Linux" ]]; then "$@" || echo "::warning::$* failed"; else "$@"; fi; }

.github/workflows/mod-registry.yml

@@ -0,0 +1,34 @@
+name: mod-registry
+# The submission service is its own workspace (crates/horizon-mod-registry), so the checks job doesn't build
+# it: this one does, when it or horizon-mods (the checks it shares with the launcher and the game) changes.
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'crates/horizon-mods/**'
+      - 'crates/horizon-mod-registry/**'
+      - '.github/workflows/mod-registry.yml'
+  pull_request:
+    paths:
+      - 'crates/horizon-mods/**'
+      - 'crates/horizon-mod-registry/**'
+      - '.github/workflows/mod-registry.yml'
+permissions:
+  contents: read
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    defaults:
+      run:
+        working-directory: crates/horizon-mod-registry
+    steps:
+      - uses: actions/checkout@v4
+      - run: rustup toolchain install stable --profile minimal --component rustfmt --component clippy
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: crates/horizon-mod-registry
+          save-if: ${{ github.ref == 'refs/heads/main' }}
+      - run: cargo +stable fmt --check
+      - run: cargo +stable clippy --all-targets --locked -- -D warnings
+      - run: cargo +stable test --locked

.github/workflows/nightly-build.yml

@@ -0,0 +1,278 @@
+name: nightly build
+run-name: nightly build${{ inputs.request && format(' (request {0})', inputs.request) || '' }}
+# The Nightly, the only build Horizon ships since 2026-10-28 (docs/release-flow.md "Nightly"; Ludovic). When the batch
+# train decides (release.yml, with the commit as `base`), once a night, and when a trusted
+# reviewer asks (`/nightly 2640 2642`, nightly-command.yml), it builds main plus the pull requests the reviewers
+# picked, merged in order (tools/ci/nightly_set.py), or main alone with none picked. Main is its newest commit where
+# checks and parity-main passed (or the `base` input), as for a release, and no Nightly is published while a
+# release-blocker is open. It publishes the result as the `nightly` pre-release, which every launcher and
+# `horizon-server update` install. The previous nightly stays a week as nightly-<date>.
+#
+# Why the signing key never meets the pull requests' code:
+# - `pick` merges the picked heads onto main with `git merge-tree --write-tree`: git objects only, no working tree,
+#   so none of their files reaches the disk and no hook, filter or script of theirs runs. It refuses any pull
+#   request that changes a path CODEOWNERS gives to Ludovic (this folder, tools/ci/, the signing and update code),
+#   pushes the merge as nightly/build-<date>-<n> and saves the set on the nightly-state branch.
+# - This file, game-build.yml and every script below run from main's copy: a schedule runs the default branch, and
+#   `uses: ./…` takes the caller's commit. A picked pull request's own .github/ is never read.
+# - `build` (game-build.yml, `trusted: false`) never reaches a release's tools: its macOS jobs run on the runner
+#   that already runs pull requests' parity jobs, never the release runner; its Rust cache has its own key and is
+#   never saved; and releases don't read the machine's shared sccache.
+# - `build` (game-build.yml) checks out and compiles the merge with no secrets: its token reads contents only and
+#   isn't kept in the checkout; the macOS programs are signed ad hoc (Developer ID needs the runner's keychain,
+#   which stays locked for nightlies).
+# - `sign` is the only job with RELEASE_SIGNING_KEY. It checks out nothing but main's tools/ci/sign_release.sh, which
+#   runs the runner's sha256sum and OpenSSL over the archives: it hashes them, never runs them. The signed message
+#   names the channel ("horizon release nightly"), so a nightly's signature can't pass for a release's.
+# - `publish` verifies the signature with main's horizon-release-sign, checks the smoke test, and only then moves
+#   the tag. Like sign, it never executes what build produced.
+# - The source ships with the build: `pick` writes horizon-source.tar.gz with `git archive` (git objects again, nothing
+#   run), `sign` signs it with the builds, and `publish` attaches it and tags the commit nightly-source/<date>-<short>
+#   for good (the dated release and the build branch go after 7 days; native mods pin the commit: docs/native-mods.md).
+#   gh workflow run "nightly build"                     # now (skips when the pick is the same commit as last night's)
+#   gh workflow run "nightly build" -f force=true       # build and publish even if unchanged
+#   gh workflow run "nightly build" -f dry_run=true     # build and sign with a throwaway key, publish nothing
+on:
+  schedule:
+    - cron: '17 20 * * *'  # 20:17 UTC: after the day's waves, before the 03:07 Paris parity audit takes the Mac mini
+  workflow_dispatch:
+    inputs:
+      force:
+        description: Build and publish even if tonight's pick is the commit already published
+        type: boolean
+        default: false
+      dry_run:
+        description: Build and sign with a throwaway key, publish nothing
+        type: boolean
+        default: false
+      issue:
+        description: The issue or pull request whose `/nightly` comment asked for this build (answered there)
+        type: string
+        default: ''
+      request:
+        description: The command's id, in the run's name so it can link the run
+        type: string
+        default: ''
+      prs:
+        description: A dry run's own set, `2640@<head> 2642@<head>` (the saved set stays)
+        type: string
+        default: ''
+      base:
+        description: The commit of main to build on (default main's newest with green checks and parity-main)
+        type: string
+        default: ''
+      urgent:
+        description: Past the day's cap of 12 builds (the train, for a release-now pull request or a forced run)
+        type: boolean
+        default: false
+permissions:
+  contents: read
+concurrency:
+  # One build at a time. A newer request replaces one still waiting: it builds the set as it is by then, so no pick
+  # is lost.
+  group: nightly-build
+  cancel-in-progress: false
+jobs:
+  pick:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: write       # nightly/build-<date>-<n> and the nightly-state branch (main is protected)
+      issues: write         # says in the thread when the picked pull requests conflict
+      pull-requests: write
+      actions: read         # main's newest green checks and parity-main runs (the base)
+    outputs:
+      build: ${{ steps.pick.outputs.build }}
+      sha: ${{ steps.pick.outputs.sha }}
+      short: ${{ steps.pick.outputs.short }}
+      source: ${{ steps.pick.outputs.source }}
+      date: ${{ steps.pick.outputs.date }}
+      version: ${{ steps.pick.outputs.version }}
+      nightly: ${{ steps.pick.outputs.nightly }}
+      source_tag: ${{ steps.pick.outputs.source_tag }}
+      dry_run: ${{ steps.mode.outputs.dry_run }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+      - id: mode
+        # A dry run never publishes; a hand-started run off main is always one.
+        run: echo "dry_run=${{ github.event_name == 'workflow_dispatch' && (inputs.dry_run || github.ref != 'refs/heads/main') }}" >> "$GITHUB_OUTPUT"
+      - id: pick
+        env:
+          GH_TOKEN: ${{ github.token }}
+          FORCE: ${{ (inputs.force || steps.mode.outputs.dry_run == 'true') && 'yes' || '' }}
+          DRY_RUN: ${{ steps.mode.outputs.dry_run }}
+          NIGHTLY_ISSUE: ${{ inputs.issue }}
+          NIGHTLY_PRS: ${{ inputs.prs }}
+          NIGHTLY_BASE: ${{ inputs.base }}
+          NIGHTLY_URGENT: ${{ inputs.urgent }}
+        run: |
+          python3 tools/ci/nightly.py pick ${FORCE:+--force} | tee -a "$GITHUB_STEP_SUMMARY"
+          { echo; cat nightly-notes.md; } >> "$GITHUB_STEP_SUMMARY"
+      - name: Old nightly/build-* branches deleted (scheduled runs only)
+        # Ludovic, 2026-10-27: older than 7 days, but never the newest build or one a published nightly points to;
+        # nothing but nightly/build-* (nightly.py stale_builds, tests/test_nightly.py).
+        if: github.event_name == 'schedule'
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          { echo "### nightly/build-* branches"; python3 tools/ci/nightly.py prune-builds --days 7; } | tee -a "$GITHUB_STEP_SUMMARY"
+      - name: The source of the build (horizon-source.tar.gz)
+        if: steps.pick.outputs.build == 'true'
+        env:
+          SHA: ${{ steps.pick.outputs.sha }}
+        run: git archive --format=tar.gz --prefix="horizon-${SHA:0:7}/" -o horizon-source.tar.gz "$SHA"
+      - uses: actions/upload-artifact@v4
+        if: steps.pick.outputs.build == 'true'
+        with:
+          name: horizon-source
+          path: horizon-source.tar.gz
+          if-no-files-found: error
+          retention-days: 3
+      - uses: actions/upload-artifact@v4
+        with:
+          name: nightly-notes
+          path: nightly-notes.md
+          retention-days: 3
+
+  build:
+    needs: pick
+    if: needs.pick.outputs.build == 'true'
+    uses: ./.github/workflows/game-build.yml
+    with:
+      ref: ${{ needs.pick.outputs.sha }}
+      version: ${{ needs.pick.outputs.version }}
+      nightly: ${{ needs.pick.outputs.nightly }}
+      developer_id: false
+      trusted: false  # it can hold unreviewed pull requests: their own cache key, never saved, not the release runner
+
+  sign:
+    needs: [pick, build]
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    # The key's only job: main's sign_release.sh hashes the archives and signs with the runner's OpenSSL.
+    environment: ${{ needs.pick.outputs.dry_run != 'true' && 'release' || '' }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          sparse-checkout: tools/ci/sign_release.sh
+          sparse-checkout-cone-mode: false
+          persist-credentials: false
+      - uses: actions/download-artifact@v4
+        with:
+          path: dist
+          pattern: horizon-*
+          merge-multiple: true
+      - name: Sign the checksums (SHA256SUMS, SHA256SUMS.sig) for the nightly channel
+        env:
+          RELEASE_SIGNING_KEY: ${{ secrets.RELEASE_SIGNING_KEY }}
+          RELEASE_SIGNING_KEY_NEXT: ${{ secrets.RELEASE_SIGNING_KEY_NEXT }}
+          EPHEMERAL: ${{ needs.pick.outputs.dry_run == 'true' && 'yes' || '' }}
+        run: |
+          bash tools/ci/sign_release.sh nightly dist/horizon-linux-x86_64.tar.gz dist/horizon-windows-x64.zip \
+            dist/horizon-macos-arm64.zip dist/horizon-server-linux-x86_64.tar.gz dist/horizon-source.tar.gz
+      - uses: actions/upload-artifact@v4
+        with:
+          name: signature
+          path: dist/SHA256SUMS*
+          if-no-files-found: error
+          retention-days: 3
+      - uses: actions/upload-artifact@v4
+        if: needs.pick.outputs.dry_run == 'true'
+        with:
+          name: ephemeral.pub
+          path: dist/ephemeral.pub
+          retention-days: 3
+
+  publish:
+    needs: [pick, build, sign]
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    permissions:
+      contents: write
+      issues: read          # the open release-blocker issues (gate)
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: false
+      - uses: actions/download-artifact@v4
+        with:
+          path: dist
+          merge-multiple: true
+      - name: The signature, checked as launchers check it
+        env:
+          EPHEMERAL: ${{ needs.pick.outputs.dry_run == 'true' && 'yes' || '' }}
+        run: |
+          key=(); [[ -n "$EPHEMERAL" ]] && key=(--key "$(cat dist/ephemeral.pub)")
+          cargo run --locked --quiet -p horizon-release-sign -- verify --tag nightly --publishing "${key[@]}" dist
+      - name: Ready to publish (the smoke test drew a world, no release-blocker is open)
+        # Right before publishing, as for a release: an issue labelled while the builds ran still holds it. A dry run
+        # only reports what a real run would do (that is how a blocker's fix is tried).
+        env:
+          GH_TOKEN: ${{ github.token }}
+          DRY_RUN: ${{ needs.pick.outputs.dry_run }}
+        run: |
+          if ! python3 tools/release_train.py gate --kind game --smoke dist/smoke-test.json --blockers; then
+            [[ "$DRY_RUN" == true ]] || { echo "::error::Nothing published"; exit 1; }
+            echo "::warning::A real run would publish nothing"
+          fi
+      - name: Publish as the `nightly` pre-release
+        if: needs.pick.outputs.dry_run != 'true'
+        env:
+          GH_TOKEN: ${{ github.token }}
+          SHA: ${{ needs.pick.outputs.sha }}
+          DATE: ${{ needs.pick.outputs.date }}
+          SOURCE_TAG: ${{ needs.pick.outputs.source_tag }}
+        run: |
+          set -euo pipefail
+          python3 tools/ci/nightly.py rotate
+          signature=(); [[ -f dist/SHA256SUMS.sig ]] && signature=(dist/SHA256SUMS.sig)
+          # A pre-release, never GitHub's latest: the latest stays the last vX.Y.Z, which launchers and servers from
+          # before the Nightly-only switch keep (they don't read Nightlies).
+          gh release create nightly --prerelease --latest=false --target "$SHA" \
+            --title "Nightly $DATE · ${SHA:0:7}" --notes-file dist/nightly-notes.md \
+            "dist/horizon-linux-x86_64.tar.gz#Game files the launcher installs (Nightly): Linux (horizon-linux-x86_64.tar.gz)" \
+            "dist/horizon-windows-x64.zip#Game files the launcher installs (Nightly): Windows (horizon-windows-x64.zip)" \
+            "dist/horizon-macos-arm64.zip#Game files the launcher installs (Nightly): macOS (horizon-macos-arm64.zip)" \
+            "dist/horizon-server-linux-x86_64.tar.gz#Nightly dedicated server for Linux (horizon-server-linux-x86_64.tar.gz)" \
+            "dist/horizon-source.tar.gz#Source of this Nightly, commit ${SHA:0:7} (horizon-source.tar.gz; kept for good as the tag $SOURCE_TAG)" \
+            dist/SHA256SUMS "${signature[@]}" dist/smoke-test.json
+          python3 tools/ci/nightly.py keep-source "$SHA" "$DATE"
+          python3 tools/ci/nightly.py prune --days 7
+      - name: Dry run, the nightly that would be published
+        if: needs.pick.outputs.dry_run == 'true'
+        run: |
+          echo "Would publish nightly at ${{ needs.pick.outputs.sha }} (${{ needs.pick.outputs.source }})"
+          ls -l dist
+
+  answer:
+    # Tells the thread that asked for this build how it ended. A conflict `pick` already explained there.
+    needs: [pick, build, sign, publish]
+    if: always() && inputs.issue != '' && needs.pick.result == 'success'
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      issues: write
+      pull-requests: write
+    steps:
+      - env:
+          GH_TOKEN: ${{ github.token }}
+          ISSUE: ${{ inputs.issue }}
+          BUILD: ${{ needs.pick.outputs.build }}
+          PUBLISHED: ${{ needs.publish.result }}
+          DRY_RUN: ${{ needs.pick.outputs.dry_run }}
+          NAME: Nightly ${{ needs.pick.outputs.date }} · ${{ needs.pick.outputs.short }}
+          RUN: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
+        run: |
+          if [[ "$BUILD" != true ]]; then
+            text="nothing new: the published Nightly is already this build."
+          elif [[ "$PUBLISHED" == success && "$DRY_RUN" == true ]]; then
+            text="the dry run built and signed $NAME; nothing was published. $RUN"
+          elif [[ "$PUBLISHED" == success ]]; then
+            text="published $NAME: https://github.com/$GITHUB_REPOSITORY/releases/tag/nightly. Launchers install it at their next check."
+          else
+            text="the build failed, nothing was published: $RUN"
+          fi
+          gh api "repos/$GITHUB_REPOSITORY/issues/$ISSUE/comments" -f body="🤖 Nightly: $text"

.github/workflows/nightly-command.yml

@@ -0,0 +1,46 @@
+name: nightly command
+# `/nightly …` comments: the trusted reviewers in .github/trusted-reviewers.txt (and Ludovic) pick the pull requests
+# the Nightly holds (docs/release-flow.md "Nightly channel", tools/ci/nightly_set.py). This job only checks who asked,
+# saves the set on the nightly-state branch, starts `nightly build` and answers in the thread.
+#
+# Why no pull request's code runs here, though the token can write:
+# - `issue_comment` always runs this file from main, whoever comments and wherever; a pull request's own copy of it
+#   is never read.
+# - It checks out main and runs main's nightly_set.py. The comment's text and author reach it as env vars, never in
+#   a shell line.
+# - It never checks out, fetches or merges a pull request: it reads their file lists through the API. The merge
+#   happens in nightly-build.yml's `pick`, with git objects only; their code runs in its `build`, without secrets.
+on:
+  issue_comment:
+    types: [created]
+permissions:
+  contents: read
+jobs:
+  command:
+    # Every other comment skips here, before a runner starts.
+    if: startsWith(github.event.comment.body, '/nightly') && github.event.comment.user.type != 'Bot'
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      contents: write       # the nightly-state branch (main is protected)
+      actions: write        # starts `nightly build`
+      issues: write         # answers in the thread
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+          persist-credentials: false
+          sparse-checkout: |
+            .github/CODEOWNERS
+            .github/trusted-reviewers.txt
+            tools/ci/nightly_set.py
+          sparse-checkout-cone-mode: false
+      - name: Run the command
+        env:
+          GH_TOKEN: ${{ github.token }}
+          BODY: ${{ github.event.comment.body }}
+          AUTHOR: ${{ github.event.comment.user.login }}
+          ISSUE: ${{ github.event.issue.number }}
+          COMMENT_URL: ${{ github.event.comment.html_url }}
+        run: python3 tools/ci/nightly_set.py command

.github/workflows/nightly.yml

@@ -8,7 +8,7 @@ name: nightly audit
 #   gh workflow run "nightly audit" -f dry_run=true    # the audit, without touching issues
 on:
   schedule:
-    # GitHub's schedules are in UTC: both, and the first step keeps the one that is 03:00 in Paris.
+    # GitHub's schedules are in UTC: both, and the first step keeps the one that is 03:07 in Paris today.
     - cron: '7 1 * * *'
     - cron: '7 2 * * *'
   workflow_dispatch:
@@ -29,15 +29,21 @@ env:
 
 jobs:
   audit:
-    runs-on: [self-hosted, horizon-game]
-    timeout-minutes: 150
+    # The Mac mini's runners only: the audit compares with the previous one, so it stays on one platform.
+    runs-on: [self-hosted, horizon-game, macOS]
+    timeout-minutes: 240  # every harness (~80 min) plus lan_integration (~40 min an attempt under load, retried)
     steps:
-      - name: 03:00 in Paris
+      - name: 03:07 in Paris
         id: when
+        env:
+          SCHEDULE: ${{ github.event.schedule }}
         run: |
-          hour=$(TZ=Europe/Paris date +%H)
-          if [[ "${{ github.event_name }}" == schedule && "$hour" != 03 ]]; then
-            echo "It is ${hour}:00 in Paris: the other schedule runs the audit."
+          # Which cron is 03:07 in Paris, from Paris's offset today: GitHub can start a schedule hours late, so the
+          # clock at start time can't tell (on 2026-10-26 both started after 04:00 Paris and both skipped).
+          offset=$(TZ=Europe/Paris date +%z)
+          ours=$([ "$offset" = +0200 ] && echo '7 1 * * *' || echo '7 2 * * *')
+          if [[ "${{ github.event_name }}" == schedule && "$SCHEDULE" != "$ours" ]]; then
+            echo "Paris is at UTC${offset} today: the '$ours' schedule runs the audit."
             echo "run=false" >> "$GITHUB_OUTPUT"
           else
             echo "run=true" >> "$GITHUB_OUTPUT"
@@ -65,7 +71,8 @@ jobs:
         run: |
           echo "since=$(date +%Y-%m-%dT%H:%M:%S)" >> "$GITHUB_OUTPUT"
           set +e
-          python3 tools/parity.py --all --timeout 1800 2>&1 | tee "$RUNNER_TEMP/audit.log"
+          # lan_integration (the whole lan_e2e suite) takes ~2,400 s under load, past the usual 1,800.
+          python3 tools/parity.py --all --timeout 3000 2>&1 | tee "$RUNNER_TEMP/audit.log"
           echo "exit=${PIPESTATUS[0]}" >> "$GITHUB_OUTPUT"
           { echo '```'; tail -40 "$RUNNER_TEMP/audit.log"; echo '```'; } >> "$GITHUB_STEP_SUMMARY"
       - name: Issues for the harnesses that regressed

.github/workflows/overlap-note.yml

@@ -0,0 +1,41 @@
+name: overlap note
+# One comment on a pull request naming the other open pull requests that close the same issue or change the same
+# functions, edited on every push (tools/ci/overlap_note.py, issue #3859).
+#
+# Why no pull request's code runs here, though `pull_request_target` gives a token that can write:
+# - `pull_request_target` runs this file and the script from main, never the pull request's copy.
+# - The checkout is main's (`ref: main`), blobless, with the script alone on disk. The pull requests' heads are fetched
+#   as git objects and only diffed, never checked out; git runs with hooks, fsmonitor, external diff and textconv off.
+# - The rest comes from the API. The token writes the comment only.
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronize, ready_for_review]
+permissions:
+  contents: read
+jobs:
+  note:
+    if: github.event.pull_request.base.ref == 'main'
+    # A newer push replaces the note being computed.
+    concurrency:
+      group: overlap-note-${{ github.event.pull_request.number }}
+      cancel-in-progress: true
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: read
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+          fetch-depth: 0
+          filter: blob:none
+          persist-credentials: false
+          sparse-checkout: |
+            tools/ci/overlap_note.py
+          sparse-checkout-cone-mode: false
+      - name: Note
+        env:
+          GH_TOKEN: ${{ github.token }}
+          REPO: ${{ github.repository }}
+        run: python3 tools/ci/overlap_note.py event

.github/workflows/parity-main.yml

@@ -0,0 +1,77 @@
+name: parity-main
+# The vanilla harnesses on main, a batch of merges at a time (docs/release-flow.md#parity-on-main), on the Mac mini's
+# runner. One run at a time: merges that land while a run goes on wait in one pending run (GitHub keeps only the
+# newest), which checks every merge since main's last green parity-main (tools/parity_main.py base). On a failure it
+# bisects the failing harnesses over those merges and comments on the pull request that broke them. Releases ship
+# only a commit whose parity-main passed (tools/release_train.py), so nothing a harness catches reaches players.
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+permissions:
+  contents: read
+  # The comment on the merge that broke a harness.
+  pull-requests: write
+  # tools/parity_main.py base reads earlier runs.
+  actions: read
+concurrency:
+  group: parity-main
+  cancel-in-progress: false
+env:
+  # Test runs never reach the telemetry server: no live-count ping, no uploads (docs/telemetry.md).
+  HORIZON_TELEMETRY_URL: "off"
+
+jobs:
+  parity-main:
+    # A Mac mini runner of its own (ludovics-mac-mini-2 holds only this label since 2026-10-26): behind PR parity jobs
+    # this run waited 2 h while every merge replaced the pending one, and on the release runner a release then waited
+    # behind the next run. PR parity jobs have ludovics-mac-mini and playhorizon. Not playhorizon: its 4 CPUs
+    # make a core-crate run several times longer, and a failure here bisects and comments on merges.
+    runs-on: [self-hosted, macOS, horizon-parity-main]
+    timeout-minutes: 240  # a core-crate batch reruns ~300 harnesses (~60-90 min), a bisect a few rounds of the failures
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.sha }}
+          fetch-depth: 0
+          persist-credentials: false
+          # Keeps .local/ (parity state, probe builds, oracle results) and target/ between runs.
+          clean: false
+      - uses: dtolnay/rust-toolchain@stable
+      - name: Tools from the runner
+        run: bash tools/ci/runner-env.sh
+      - name: Vanilla data, and resources prepared by this preparer
+        run: bash tools/ci/vanilla-data.sh
+      - name: Main's last green parity-main
+        id: base
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: echo "sha=$(python3 tools/parity_main.py base)" >> "$GITHUB_OUTPUT"
+      - name: The harnesses the merges since then can affect
+        id: harnesses
+        # A failure here is judged by the next step: the run passes when every failed harness passes again at HEAD.
+        continue-on-error: true
+        env:
+          PARITY_HOSTS: ''
+          BASE_SHA: ${{ steps.base.outputs.sha }}
+        run: |
+          echo "Merges since ${BASE_SHA}:"
+          git log --first-parent --format='  %h %s' "$BASE_SHA..HEAD"
+          python3 tools/parity.py --changed "$BASE_SHA" --timeout 2400
+      - name: A flake, or the merge that broke them
+        if: steps.harnesses.outcome == 'failure'
+        env:
+          GH_TOKEN: ${{ github.token }}
+          PARITY_HOSTS: ''
+          BASE_SHA: ${{ steps.base.outputs.sha }}
+        run: |
+          rm -rf .local/parity-main-logs && cp -R .local/parity-runner/logs .local/parity-main-logs 2>/dev/null || true
+          python3 tools/parity_main.py bisect "$BASE_SHA" --comment
+      - name: Logs of the failed harnesses
+        if: steps.harnesses.outcome == 'failure'
+        uses: actions/upload-artifact@v4
+        with:
+          name: parity-main-logs
+          path: .local/parity-main-logs/
+          if-no-files-found: ignore
+          retention-days: 7

.github/workflows/parity.yml

@@ -1,6 +1,6 @@
 name: parity
-# The vanilla harnesses a pull request's changes can affect, on the Mac mini's runner, which holds the maintainer's
-# own Minecraft files (Horizon never downloads the game). Called by ci.yml for pull requests from this repository
+# The vanilla harnesses a pull request's changes can affect, on the Mac mini's runner or playhorizon's, which hold the
+# maintainer's own Minecraft files (Horizon never downloads the game). Called by ci.yml for pull requests from this repository
 # and by run-parity.yml when a maintainer labels a fork's pull request run-parity. See docs/release-flow.md.
 on:
   workflow_call:
@@ -13,6 +13,13 @@ on:
         description: The commit to check out and test
         type: string
         required: true
+      full:
+        description: >-
+          The pull request carries the full-parity label (a change every harness reaches, such as a crate split): it
+          runs on playhorizon's runner only, so the Mac mini's runners stay free for the others. While that runner is
+          busy the job waits for it.
+        type: boolean
+        default: false
 permissions:
   contents: read
 env:
@@ -21,28 +28,64 @@ env:
 
 jobs:
   parity:
-    runs-on: [self-hosted, horizon-game]
-    timeout-minutes: 120  # a change to core crates reruns ~300 harnesses: ~60-90 min on the Mac mini
+    runs-on: ${{ inputs.full && fromJSON('["self-hosted", "horizon-game", "playhorizon"]') || fromJSON('["self-hosted", "horizon-game"]') }}
+    # A change to core crates reruns ~350 harnesses: ~60-90 min on the Mac mini; on playhorizon (4 of its 8 vCPUs, 4
+    # harnesses at a time) up to a few hours, and any pull request's job may land there.
+    timeout-minutes: ${{ inputs.full && 360 || 180 }}
     steps:
       - uses: actions/checkout@v4
         with:
-          # The commit the event names: a fork's later pushes need another run-parity label.
+          # The commit the event names: a fork's later pushes need another run-parity label. The next step merges
+          # main into it.
           ref: ${{ inputs.head }}
           fetch-depth: 0
           persist-credentials: false
           # Keeps .local/ (parity state, probe builds, oracle results) and target/ between runs.
           clean: false
+      - name: The head merged into main (what merging it would land)
+        id: merge
+        env:
+          BASE_SHA: ${{ inputs.base }}
+          HEAD_SHA: ${{ inputs.head }}
+        run: |
+          # Harness fixes and game fixes that reached main since the branch was made then apply here too: a head
+          # tested alone failed harnesses already fixed on main (server_knockback before #2114, mob_ai's heap before
+          # #2270, save_roundtrip before #2212). Selection then compares with this main, so it sees only the pull
+          # request's own changes. A head that conflicts with main is tested alone.
+          set -euo pipefail
+          git merge --abort 2>/dev/null || true
+          git fetch -q --no-tags origin +refs/heads/main:refs/remotes/origin/main
+          main=$(git rev-parse origin/main)
+          if git -c user.name=parity -c user.email=parity@localhost merge -q --no-edit --no-ff "$main" >/dev/null 2>&1; then
+            echo "base=$main" >> "$GITHUB_OUTPUT"
+            echo "Tested: head ${HEAD_SHA:0:9} merged into main ${main:0:9}" | tee -a "$GITHUB_STEP_SUMMARY"
+          else
+            git merge --abort
+            echo "base=$BASE_SHA" >> "$GITHUB_OUTPUT"
+            echo "::warning::head ${HEAD_SHA:0:9} conflicts with main ${main:0:9}: tested alone, without main's fixes"
+            echo "Tested: head ${HEAD_SHA:0:9} alone (it conflicts with main ${main:0:9})" | tee -a "$GITHUB_STEP_SUMMARY"
+          fi
       - uses: dtolnay/rust-toolchain@stable
       - name: Tools from the runner
         run: bash tools/ci/runner-env.sh
       - name: Vanilla data, and resources prepared by this preparer
         run: bash tools/ci/vanilla-data.sh
+      - name: The prepared output is the one the preparer's OUTPUT_VERSION says
+        env:
+          BASE_SHA: ${{ steps.merge.outputs.base }}
+        run: |
+          # A head made before OUTPUT_VERSION (#1947) that conflicts with main has neither the tool nor the number.
+          if [ ! -f tools/prepare_output.py ] || ! grep -q OUTPUT_VERSION crates/horizon-prepare/src/lib.rs; then
+            echo "This head's preparer has no OUTPUT_VERSION: nothing to check"
+            exit 0
+          fi
+          python3 tools/prepare_output.py check --cache --base "$BASE_SHA"
       - name: The version constants are the pinned jar's
         run: python3 tools/gen_version_consts.py --check
       - name: The harnesses this change can affect
         env:
           PARITY_HOSTS: ''
-          BASE_SHA: ${{ inputs.base }}
+          BASE_SHA: ${{ steps.merge.outputs.base }}
         run: python3 tools/parity.py --changed "$BASE_SHA" --timeout 2400  # world_spawn takes ~1480 s on a busy runner
       - name: Logs of the failed harnesses
         if: failure()

.github/workflows/pr-labels.yml

@@ -0,0 +1,36 @@
+name: pr labels
+# A pull request's kind label (the box ticked in the template) and area labels (the paths it changes):
+# tools/ci/pr_labels.py, CONTRIBUTING.md "Pull requests".
+#
+# Why no pull request's code runs here, though `pull_request_target` gives a token that can write to fork PRs:
+# - `pull_request_target` runs this file and the script from main, never the pull request's copy.
+# - It checks out main's script only (`ref: main`), never the pull request's head or merge commit.
+# - The script reads the event file (the description is data in JSON, never in a shell line) and the API's list of
+#   changed file names; it runs, builds and imports nothing of theirs. The token writes labels only.
+on:
+  pull_request_target:
+    types: [opened, reopened, synchronize, edited, ready_for_review]
+permissions:
+  contents: read
+jobs:
+  label:
+    # Title-only edits change nothing: skip them before a runner starts.
+    if: github.event.action != 'edited' || github.event.changes.body != null
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      contents: read
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+          persist-credentials: false
+          sparse-checkout: |
+            tools/ci/pr_labels.py
+          sparse-checkout-cone-mode: false
+      - name: Label
+        env:
+          GH_TOKEN: ${{ github.token }}
+          REPO: ${{ github.repository }}
+        run: python3 tools/ci/pr_labels.py event

.github/workflows/release.yml

@@ -1,24 +1,19 @@
 name: release
-# Automatic game releases (docs/release-flow.md). After every green `checks` run on main, every 10 minutes (so a
-# release waiting for merges to settle goes out without another merge) and by hand, tools/release_train.py decides:
-# a release when 5 pull requests merged since the last one changed what players run and the newest merged 5 minutes
-# ago, or when the oldest has waited 6 hours, or at once for a pull request labelled release-now.
-# RELEASES_PAUSED=1 (repository variable) stops them; so does an open issue labelled release-blocker, forced runs too.
-# Builds Linux (an older Ubuntu, so the binary runs on any recent distribution and on NixOS through nix-ld) and
-# Windows on GitHub, macOS on the Mac mini's runner (MAC_RUNNER=macos-latest sends it to GitHub), then
-# publishes vX.Y.Z on the release line in .github/release-line.txt (docs/versioning.md; without it, the dated
-# vYYYY.MM.DD[.N] from before 0.2) with notes from the merged pull requests, as the release and GitHub's latest: one
-# channel, which launchers, `horizon-server update` and install.sh follow at once. So it is published only after the
-# checks that used to gate a promotion pass in this run: the Mac mini's smoke test drew a world, and no release-blocker
-# is open (tools/release_train.py gate); otherwise nothing is published. macOS: with the repository variable
-# MACOS_SIGN_IDENTITY set, the programs are signed with
-# Developer ID and the hardened runtime and the zip is notarized, from the runner's signing keychain
-# (packaging/macos/README.md); unset (forks), ad hoc.
-#   gh workflow run release --ref <branch>                       # dry run: builds and notes, publishes nothing
-#   gh workflow run release -f dry_run=false -f force=true       # on main: release now, whatever the rules say
+# Automatic game releases (docs/release-flow.md). Horizon ships only the Nightly since 2026-10-28 (Ludovic): this
+# workflow is the batch train that decides when a new Nightly goes out, and `nightly build` (nightly-build.yml) builds,
+# signs and publishes it. After every green `checks` run on main, every 10 minutes (so a batch waiting for merges to
+# settle goes out without another merge) and by hand, tools/release_train.py decides, for a commit whose checks and
+# parity-main (the vanilla harnesses on main) both passed: a Nightly when 5 pull requests merged since the published
+# Nightly changed what players run and the newest merged 5 minutes ago, or when the oldest has waited 6 hours, or at
+# once for a pull request labelled release-now. RELEASES_PAUSED=1 (repository variable) stops it; so does an open issue
+# labelled release-blocker, forced runs too (nightly-build.yml checks again before publishing). One Nightly build at a
+# time, at most 12 a day (release-now and force=true pass the cap). No `vX.Y.Z` game release is made any more.
+#   gh workflow run release --ref <branch>                       # dry run: decides, starts nothing
+#   gh workflow run release -f dry_run=false -f force=true       # on main: a Nightly now, whatever the rules say
 on:
   workflow_run:
-    workflows: [checks]
+    # A game release ships a commit both passed on (parity-main runs on batches: the newest commit it passed on).
+    workflows: [checks, parity-main]
     types: [completed]
     branches: [main]
   schedule:
@@ -26,19 +21,24 @@ on:
   workflow_dispatch:
     inputs:
       dry_run:
-        description: Build everything and write the notes, but publish nothing
+        description: Decide only; start no Nightly build
         type: boolean
         default: true
       force:
-        description: Release even without player-facing changes, before merges settle or while paused
+        description: A Nightly even without player-facing changes, before merges settle, while paused or past the day's cap
         type: boolean
         default: false
 permissions:
   contents: read
   # The open release-blocker issues (decide).
   issues: read
+  # The checks, parity-main and nightly build runs (decide).
+  actions: read
 concurrency:
-  group: game-release
+  # One release at a time. A hand-started dry run publishes nothing, so it can't race a real release: it gets a
+  # group of its own. In the shared group, a release queued behind it replaced it as the pending run and GitHub
+  # cancelled it (#2779's dry run, 2026-10-27), which happens all day while releases go out in batches.
+  group: game-release${{ github.event_name == 'workflow_dispatch' && inputs.dry_run && '-dry-run' || '' }}
   cancel-in-progress: false
 jobs:
   decide:
@@ -49,9 +49,8 @@ jobs:
     timeout-minutes: 10
     outputs:
       release: ${{ steps.decide.outputs.release }}
-      tag: ${{ steps.decide.outputs.tag }}
-      version: ${{ steps.decide.outputs.version }}
       head: ${{ steps.decide.outputs.head }}
+      urgent: ${{ steps.decide.outputs.urgent }}
       dry_run: ${{ steps.mode.outputs.dry_run }}
     steps:
       - uses: actions/checkout@v4
@@ -64,326 +63,28 @@ jobs:
         env:
           GH_TOKEN: ${{ github.token }}
           RELEASES_PAUSED: ${{ vars.RELEASES_PAUSED }}
-          # The commit whose checks just passed; a dry run builds the branch it was started on; otherwise
-          # main's newest commit with green checks.
+          # The commit whose checks or parity-main just passed; a dry run builds the branch it was started on;
+          # otherwise main's newest commit with green checks and parity-main.
           HEAD_SHA: ${{ github.event.workflow_run.head_sha || (steps.mode.outputs.dry_run == 'true' && github.sha) || '' }}
           FORCE: ${{ inputs.force && 'yes' || '' }}
         run: |
           python3 tools/release_train.py decide --kind game ${HEAD_SHA:+--head "$HEAD_SHA"} ${FORCE:+--force} | tee decision.json
           echo "### $(jq -r '.reason' decision.json)" >> "$GITHUB_STEP_SUMMARY"
-          # The version the programs are built with (docs/versioning.md): the tag without its v.
-          tag=$(jq -r '.tag' decision.json)
-          echo "version=${tag#v}" >> "$GITHUB_OUTPUT"
-          # A dry run builds whatever the decision, to test the builds.
-          if [[ "${{ steps.mode.outputs.dry_run }}" == true ]]; then echo "release=true" >> "$GITHUB_OUTPUT"; fi
 
-  build:
+  nightly:
+    # The Nightly is the release: nightly-build.yml builds the decided commit plus the reviewers' picks, signs it for
+    # the Nightly channel and publishes it once its smoke test passed and no release-blocker is open.
     needs: decide
-    if: needs.decide.outputs.release == 'true'
-    name: build ${{ matrix.name }}
-    strategy:
-      fail-fast: false
-      matrix:
-        include:
-          - name: linux
-            os: ubuntu-22.04
-            dir: horizon-linux-x86_64
-            asset: horizon-linux-x86_64.tar.gz
-            # The server build too: packaging/server/install.sh installs it on Linux.
-            server_dir: horizon-server-linux-x86_64
-            server_asset: horizon-server-linux-x86_64.tar.gz
-          - name: windows
-            os: windows-latest
-            dir: horizon-windows-x64
-            asset: horizon-windows-x64.zip
-            exe: .exe
-            # The C runtime linked in, so the game runs without the Visual C++ redistributable.
-            rustflags: -C target-feature=+crt-static
-          - name: macos
-            mac: true
-            dir: horizon-macos-arm64
-            asset: horizon-macos-arm64.zip
-    runs-on: ${{ matrix.mac && (vars.MAC_RUNNER || 'ludovics-mac-mini') || matrix.os }}
-    # Notarizing the zip can take a few minutes.
-    timeout-minutes: ${{ matrix.mac && 60 || 40 }}
-    env:
-      RUSTFLAGS: ${{ matrix.rustflags }}
-      # The release's version, built in (horizon_core::release): --version, user agents, crash reports and
-      # telemetry say it. No version-bump commits.
-      HORIZON_VERSION: ${{ needs.decide.outputs.version }}
-    defaults:
-      run:
-        shell: bash
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          ref: ${{ needs.decide.outputs.head }}
-          persist-credentials: false
-          # Always from a clean checkout, the Mac mini's runner too: its work folder is shared with pull requests'
-          # parity jobs, and nothing they leave (target/, an untracked .cargo/config.toml, a build script's output)
-          # may end up in a release. target/ is rebuilt from scratch; .local/ is relinked by vanilla-data.sh, which
-          # keeps its preparations outside the checkout.
-          clean: true
-      - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
-        if: runner.environment == 'github-hosted'
-        with:
-          shared-key: release-${{ matrix.name }}
-      - name: ALSA and udev headers
-        if: runner.os == 'Linux'
-        run: sudo apt-get update && sudo apt-get install -y --no-install-recommends libasound2-dev libudev-dev
-      - name: Build the client, horizon-ctl, horizon-prepare and horizon-server
-        # `horizon-client/mods`: every released game runs code mods (the feature is off in dev builds).
-        run: cargo build --release --locked --features horizon-client/mods -p horizon-client --bin horizon-client --bin horizon-ctl -p horizon-prepare --bin horizon-prepare -p horizon-server --bin horizon-server
-      - name: Every program the release folder takes was built
-        run: |
-          for binary in horizon-client horizon-ctl horizon-prepare horizon-server; do
-            test -f "target/release/$binary${{ matrix.exe }}" || { echo "::error::target/release/$binary${{ matrix.exe }} is missing"; exit 1; }
-          done
-      - name: The signing keychain, unlocked
-        if: runner.os == 'macOS' && vars.MACOS_SIGN_IDENTITY != ''
-        env:
-          MACOS_SIGN_IDENTITY: ${{ vars.MACOS_SIGN_IDENTITY }}
-        run: packaging/macos/keychain.sh unlock
-      - name: Signed with Developer ID and the hardened runtime
-        # Before the checks below, so they run the programs as players will.
-        if: runner.os == 'macOS' && vars.MACOS_SIGN_IDENTITY != ''
-        env:
-          MACOS_SIGN_IDENTITY: ${{ vars.MACOS_SIGN_IDENTITY }}
-        run: |
-          for binary in horizon-client horizon-ctl horizon-prepare horizon-server; do
-            codesign --force --options runtime --timestamp --keychain "$MACOS_SIGN_KEYCHAIN" \
-              --identifier "dev.horizon.${binary#horizon-}" --sign "$MACOS_SIGN_IDENTITY" "target/release/$binary"
-            codesign --verify --strict --verbose=2 "target/release/$binary"
-          done
-      - name: Only system libraries
-        # Windows: no non-system DLL (a "DLL not found" dialog on some players' machines). Linux: the standard
-        # loader and libraries every desktop distribution has. macOS: only the system's own libraries.
-        run: |
-          for binary in horizon-client horizon-ctl horizon-prepare horizon-server; do
-            file="target/release/$binary${{ matrix.exe }}"
-            if [[ "$RUNNER_OS" == macOS ]]; then
-              others=$(otool -L "$file" | tail -n +2 | awk '{print $1}' | grep -v -E '^(/usr/lib/|/System/Library/)' || true)
-              [[ -z "$others" ]] || { echo "::error::$binary links $others"; exit 1; }
-            else
-              ${{ runner.os == 'Windows' && 'python' || 'python3' }} tools/check_imports.py "$file"
-            fi
-          done
-      - name: Every program starts
-        run: |
-          set -euo pipefail
-          bin=target/release
-          "$bin/horizon-client${{ matrix.exe }}" --help | grep -q -- '--resources'
-          "$bin/horizon-ctl${{ matrix.exe }}" --help > /dev/null
-          "$bin/horizon-prepare${{ matrix.exe }}" --help | grep -q -- '--minecraft-dir'
-          # The version is the release's.
-          for binary in horizon-prepare horizon-server; do
-            out=$("$bin/$binary${{ matrix.exe }}" --version | tr -d '\r')
-            echo "$out"
-            [[ "$out" == "$binary $HORIZON_VERSION" ]] || { echo "::error::expected $binary $HORIZON_VERSION"; exit 1; }
-          done
-      - name: Tools from the runner
-        if: runner.environment == 'self-hosted'
-        run: bash tools/ci/runner-env.sh
-      - name: Resources prepared from the runner's own Minecraft
-        if: runner.environment == 'self-hosted'
-        run: bash tools/ci/vanilla-data.sh
-      - name: The game runs (offscreen, a new world, 1500 frames)
-        if: runner.environment == 'self-hosted'
-        run: |
-          set -euo pipefail
-          # From a scratch folder: the game keeps its saves and options in the folder it starts in.
-          home="$RUNNER_TEMP/horizon-smoke"
-          rm -rf "$home" && mkdir -p "$home"
-          version=$(sed -n 's/.*"version": *"\([^"]*\)".*/\1/p' research-lock.json | head -1)
-          client="$PWD/target/release/horizon-client"
-          resources="$PWD/.local/horizon-client/$version"
-          (cd "$home" && HORIZON_HOME="$home" HORIZON_NO_AUDIO=1 "$client" --resources "$resources" --offscreen \
-            --world smoke --seed 1 --render-distance 4 --world-frames 1500 --timeout-seconds 180 \
-            --smoke-report "$home/smoke.json" > "$home/client.log" 2>&1) || { tail -40 "$home/client.log"; exit 1; }
-          python3 - "$home/smoke.json" <<'EOF'
-          import json, sys
-          report = json.load(open(sys.argv[1]))
-          print(json.dumps(report))
-          if report.get("error") is not None or report.get("frames", 0) < 1500 or not report.get("chunks") \
-                  or not report.get("meshed_sections") or not report.get("player"):
-              sys.exit("the smoke run did not draw a world")
-          EOF
-          # Published with the release; the publish job checks it again before it publishes anything.
-          cp "$home/smoke.json" "$RUNNER_TEMP/smoke-test.json"
-      - uses: actions/upload-artifact@v4
-        if: runner.environment == 'self-hosted'
-        with:
-          name: smoke-test.json
-          path: ${{ runner.temp }}/smoke-test.json
-          if-no-files-found: error
-          retention-days: 3
-      - name: Package
-        run: |
-          set -euo pipefail
-          cargo run --locked -p xtask -- package "target/release/horizon-client${{ matrix.exe }}" "dist/${{ matrix.dir }}"
-          cd dist
-          rm -f "${{ matrix.asset }}"
-          case "${{ matrix.asset }}" in
-            *.tar.gz) tar czf "${{ matrix.asset }}" "${{ matrix.dir }}" ;;
-            *) if [[ "$RUNNER_OS" == Windows ]]; then 7z a -tzip "${{ matrix.asset }}" "${{ matrix.dir }}" > /dev/null
-               else
-                 # Without resource forks and extended attributes: plain ditto adds an
-                 # AppleDouble `._` file beside every file that has any.
-                 ditto -c -k --norsrc --noextattr --noqtn --keepParent "${{ matrix.dir }}" "${{ matrix.asset }}"
-                 if unzip -Z1 "${{ matrix.asset }}" | grep -E '(^|/)(\._|__MACOSX/)'; then
-                   echo "::error::macOS metadata files in ${{ matrix.asset }}"; exit 1
-                 fi
-               fi ;;
-          esac
-          ls -l "${{ matrix.asset }}"
-      - name: Notarized
-        # A zip of programs can't be stapled: Gatekeeper asks Apple the first time each one runs.
-        if: runner.os == 'macOS' && vars.MACOS_SIGN_IDENTITY != ''
-        run: |
-          for binary in horizon-client horizon-ctl horizon-prepare horizon-server; do
-            codesign --verify --strict "dist/${{ matrix.dir }}/$binary"
-          done
-          packaging/macos/notarize.sh "dist/${{ matrix.asset }}"
-      - uses: actions/upload-artifact@v4
-        with:
-          name: ${{ matrix.asset }}
-          path: dist/${{ matrix.asset }}
-          if-no-files-found: error
-          retention-days: 3
-      - name: The server build (the game without sound or controllers, as horizon-engine)
-        if: matrix.server_asset
-        run: |
-          set -euo pipefail
-          # After the client is packaged: target/release/horizon-client is rebuilt without the audio and
-          # controllers features, so it needs neither libasound nor libudev (minimal server images lack them),
-          # and with code mods like the client.
-          cargo build --release --locked -p horizon-client --no-default-features --features mods --bin horizon-client
-          cargo run --locked -p xtask -- package-server target/release/horizon-client "dist/${{ matrix.server_dir }}"
-          folder="dist/${{ matrix.server_dir }}"
-          python3 tools/check_imports.py --server "$folder/horizon-engine" "$folder/horizon-server" "$folder/horizon-prepare"
-          "$folder/horizon-engine" --help | grep -q -- '--resources'
-          [[ "$("$folder/horizon-server" --version)" == "horizon-server $HORIZON_VERSION" ]]
-          cd dist
-          rm -f "${{ matrix.server_asset }}"
-          tar czf "${{ matrix.server_asset }}" "${{ matrix.server_dir }}"
-          ls -l "${{ matrix.server_asset }}"
-      - uses: actions/upload-artifact@v4
-        if: matrix.server_asset
-        with:
-          name: ${{ matrix.server_asset }}
-          path: dist/${{ matrix.server_asset }}
-          if-no-files-found: error
-          retention-days: 3
-      - name: The signing keychain, locked again
-        if: always() && runner.os == 'macOS' && vars.MACOS_SIGN_IDENTITY != ''
-        run: packaging/macos/keychain.sh lock
-
-  sign:
-    needs: [decide, build]
+    if: needs.decide.outputs.release == 'true' && needs.decide.outputs.dry_run != 'true'
     runs-on: ubuntu-latest
-    timeout-minutes: 10
-    # The only job that holds the release signing key, a secret of the `release` environment, which only main's real
-    # releases enter (dry runs sign with a throwaway key). It runs no code from the repository but
-    # tools/ci/sign_release.sh, which calls only the runner's sha256sum and OpenSSL (docs/release-flow.md).
-    environment: ${{ needs.decide.outputs.dry_run != 'true' && 'release' || '' }}
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          sparse-checkout: tools/ci/sign_release.sh
-          sparse-checkout-cone-mode: false
-          persist-credentials: false
-      - uses: actions/download-artifact@v4
-        with:
-          path: dist
-          pattern: horizon-*
-          merge-multiple: true
-      - name: Sign the checksums (SHA256SUMS, SHA256SUMS.sig)
-        env:
-          RELEASE_SIGNING_KEY: ${{ secrets.RELEASE_SIGNING_KEY }}
-          RELEASE_SIGNING_KEY_NEXT: ${{ secrets.RELEASE_SIGNING_KEY_NEXT }}
-          EPHEMERAL: ${{ needs.decide.outputs.dry_run == 'true' && 'yes' || '' }}
-          TAG: ${{ needs.decide.outputs.tag }}
-        run: |
-          bash tools/ci/sign_release.sh "$TAG" dist/horizon-linux-x86_64.tar.gz dist/horizon-windows-x64.zip \
-            dist/horizon-macos-arm64.zip dist/horizon-server-linux-x86_64.tar.gz
-      - uses: actions/upload-artifact@v4
-        with:
-          name: signature
-          path: dist/SHA256SUMS*
-          if-no-files-found: error
-          retention-days: 3
-      - uses: actions/upload-artifact@v4
-        if: needs.decide.outputs.dry_run == 'true'
-        with:
-          name: ephemeral.pub
-          path: dist/ephemeral.pub
-          retention-days: 3
-
-  publish:
-    needs: [decide, build, sign]
-    runs-on: ubuntu-latest
-    timeout-minutes: 15
+    timeout-minutes: 5
     permissions:
-      contents: write
-      issues: read
+      actions: write  # starts `nightly build`
     steps:
-      - uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-      - name: Notes
-        env:
+      - env:
           GH_TOKEN: ${{ github.token }}
+          HEAD_SHA: ${{ needs.decide.outputs.head }}
+          URGENT: ${{ needs.decide.outputs.urgent }}
         run: |
-          python3 tools/release_train.py notes --kind game --tag "${{ needs.decide.outputs.tag }}" \
-            --head "${{ needs.decide.outputs.head }}" --out notes > /dev/null
-          { echo "## $(cat notes/title.txt)"; echo; cat notes/body.md; } >> "$GITHUB_STEP_SUMMARY"
-      - uses: actions/download-artifact@v4
-        with:
-          path: dist
-          merge-multiple: true
-      - name: The signature, checked as launchers check it
-        env:
-          TAG: ${{ needs.decide.outputs.tag }}
-          EPHEMERAL: ${{ needs.decide.outputs.dry_run == 'true' && 'yes' || '' }}
-        run: |
-          key=(); [[ -n "$EPHEMERAL" ]] && key=(--key "$(cat dist/ephemeral.pub)")
-          cargo run --locked --quiet -p horizon-release-sign -- verify --tag "$TAG" --publishing "${key[@]}" dist
-      - name: Ready to publish (the smoke test passed, no release-blocker is open)
-        # Right before publishing: an issue labelled while the builds ran still holds this release. A dry run only
-        # reports what a real run would do.
-        env:
-          GH_TOKEN: ${{ github.token }}
-          DRY_RUN: ${{ needs.decide.outputs.dry_run }}
-        run: |
-          if ! python3 tools/release_train.py gate --kind game --smoke dist/smoke-test.json --blockers; then
-            [[ "$DRY_RUN" == true ]] || { echo "::error::Nothing published"; exit 1; }
-            echo "::warning::A real run would publish nothing"
-          fi
-      - name: Publish ${{ needs.decide.outputs.tag }}
-        if: needs.decide.outputs.dry_run != 'true'
-        env:
-          GH_TOKEN: ${{ github.token }}
-          TAG: ${{ needs.decide.outputs.tag }}
-        run: |
-          signature=(); [[ -f dist/SHA256SUMS.sig ]] && signature=(dist/SHA256SUMS.sig)
-          # The release and the latest at once: there is one channel (docs/release-flow.md). Each archive gets a
-          # label (file#label), which GitHub's page shows instead of the file name, so nobody takes the game's
-          # files for the download (#1647). Launchers, servers and install.sh match the name, which stays.
-          gh release create "$TAG" --target "${{ needs.decide.outputs.head }}" --title "$(cat notes/title.txt)" \
-            --notes-file notes/body.md --latest \
-            "dist/horizon-linux-x86_64.tar.gz#Game files the launcher installs: Linux (horizon-linux-x86_64.tar.gz)" \
-            "dist/horizon-windows-x64.zip#Game files the launcher installs: Windows (horizon-windows-x64.zip)" \
-            "dist/horizon-macos-arm64.zip#Game files the launcher installs: macOS (horizon-macos-arm64.zip)" \
-            "dist/horizon-server-linux-x86_64.tar.gz#Dedicated server for Linux (horizon-server-linux-x86_64.tar.gz)" \
-            dist/SHA256SUMS "${signature[@]}" dist/smoke-test.json
-      - name: Dry run, the release that would be published
-        if: needs.decide.outputs.dry_run == 'true'
-        run: |
-          echo "Would publish ${{ needs.decide.outputs.tag }} at ${{ needs.decide.outputs.head }} as the release and latest: $(cat notes/title.txt)"
-          ls -l dist
-      - uses: actions/upload-artifact@v4
-        with:
-          name: release-notes
-          path: notes/
-          retention-days: 3
+          gh workflow run nightly-build.yml --repo "$GITHUB_REPOSITORY" --ref main -f base="$HEAD_SHA" -f urgent="$URGENT"
+          echo "### Started \`nightly build\` on ${HEAD_SHA:0:9}" >> "$GITHUB_STEP_SUMMARY"

.github/workflows/run-parity.yml

@@ -5,11 +5,15 @@ name: run-parity
 # skipped `verify`, and GitHub counts a skipped required check as passed.
 on:
   pull_request:
-    types: [labeled]
+    # A push starts a run only to cancel the old head's (see concurrency): the job runs on the label alone.
+    types: [labeled, synchronize]
 permissions:
   contents: read
 concurrency:
-  group: run-parity-${{ github.event.pull_request.number }}
+  # The run-parity label and pushes share one group per pull request, so the newest run cancels the one before: a
+  # pushed pull request's run tested a head the merge would no longer land. Any other label gets a group of its own:
+  # in the shared one, adding needs-proof cancelled the parity run queued seconds before (run 40766180150).
+  group: run-parity-${{ github.event.pull_request.number }}${{ github.event.action == 'labeled' && github.event.label.name != 'run-parity' && format('-{0}', github.run_id) || '' }}
   cancel-in-progress: true
 env:
   # Test runs never reach the telemetry server: no live-count ping, no uploads (docs/telemetry.md).
@@ -22,3 +26,4 @@ jobs:
     with:
       base: ${{ github.event.pull_request.base.sha }}
       head: ${{ github.event.pull_request.head.sha }}
+      full: ${{ contains(github.event.pull_request.labels.*.name, 'full-parity') }}

.github/workflows/triage-command.yml

@@ -0,0 +1,48 @@
+name: triage command
+# `/close`, `/reopen`, `/label`, `/unlabel` comments: the trusted reviewers in .github/trusted-reviewers.txt (and
+# Ludovic) triage issues and pull requests without any repository role (docs/release-flow.md "Trusted reviewers",
+# tools/ci/triage_command.py).
+#
+# Why no pull request's code runs here, though the token can write:
+# - `issue_comment` always runs this file from main, whoever comments and wherever.
+# - It checks out main's script and list only, never a pull request; it reads threads through the API.
+# - The comment's text and author reach the script as env vars, never in a shell line. The token stays in the step.
+on:
+  issue_comment:
+    types: [created]
+permissions:
+  contents: read
+jobs:
+  command:
+    # Every other comment skips here, before a runner starts.
+    if: >-
+      github.event.comment.user.type != 'Bot' && (
+      startsWith(github.event.comment.body, '/close') ||
+      startsWith(github.event.comment.body, '/reopen') ||
+      startsWith(github.event.comment.body, '/label') ||
+      startsWith(github.event.comment.body, '/unlabel'))
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    permissions:
+      contents: read
+      issues: write
+      pull-requests: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: main
+          persist-credentials: false
+          sparse-checkout: |
+            .github/trusted-reviewers.txt
+            tools/ci/nightly_set.py
+            tools/ci/triage_command.py
+          sparse-checkout-cone-mode: false
+      - name: Run the command
+        env:
+          GH_TOKEN: ${{ github.token }}
+          BODY: ${{ github.event.comment.body }}
+          AUTHOR: ${{ github.event.comment.user.login }}
+          ISSUE: ${{ github.event.issue.number }}
+          REPO: ${{ github.repository }}
+          COMMENT_URL: ${{ github.event.comment.html_url }}
+        run: python3 tools/ci/triage_command.py command

.gitignore

@@ -31,3 +31,6 @@
 /.horizon-cache/
 /crash-reports/
 /debug/
+
+# Release-only compiled original exporter bundle.
+/exporters/

AGENTS.md

@@ -10,15 +10,18 @@ Feature → files → harness for the most-changed areas: [docs/architecture.md]
   `tools/check_public_tree.py` rejects them; `git config core.hooksPath .githooks` runs it on commit.
 - **Keep your runs away from real player data.** Any game or launcher you start gets fresh `mktemp -d`
   folders in `HORIZON_HOME` (the game's data), `HORIZON_LAUNCHER_HOME`, `XDG_DATA_HOME` and
-  `XDG_CONFIG_HOME`, plus `HORIZON_LAUNCHER_NO_SELF_UPDATE=1` and `HORIZON_NO_AUDIO=1`. Never write to
+  `XDG_CONFIG_HOME`, plus `HORIZON_LAUNCHER_NO_SELF_UPDATE=1` and `HORIZON_NO_AUDIO=1`, and, for the
+  launcher, `HORIZON_LAUNCHER_TRASH`, `HORIZON_LAUNCHER_CLIPBOARD` and `HORIZON_LAUNCHER_DESKTOP` pointing into the scratch home. Never write to
   `~/.local/share/{applications,horizon,horizon-launcher}` or `~/.local/bin`.
-- **Mark what an agent posts.** A PR body starts with a line naming whose agent opened it and with what.
-  Ludovic's agents write `> 🤖 Opened by Ludovic's AI agent (Claude), not by Ludovic himself.`, and a
-  contributor's agent names its own person and tool (issues: "Filed by", reviews: "Review by"). Every
-  comment starts with `🤖 Agent:`. Never write as Ludovic or as anyone else.
+- **Mark what an agent posts.** A PR body starts with a line naming the person whose agent opened it and
+  the tool: `> 🤖 Opened by <login>'s AI agent (<tool, model>), not by <login> personally.`, where `<login>`
+  is the GitHub account the PR is opened from (`gh api user --jq .login`). Issues say "Filed by", reviews
+  "Review by". Every comment starts with `🤖 Agent:`. Write only as the person you work for: the lines on
+  this page that name Ludovic are for his own agents (account `ludovic111`), never for anyone else's.
 - **Attribution.** Commits end with a `Co-Authored-By:` line for the agent that wrote them, and PR bodies
-  with that agent's own "Generated with" line. Ludovic's agents use
-  `Co-Authored-By: Claude <model> <[email protected]>` and
+  with that agent's own "Generated with" line. Example, Ludovic's agents (Claude Code on `ludovic111`):
+  first line `> 🤖 Opened by Ludovic's AI agent (Claude), not by Ludovic himself.`, commits
+  `Co-Authored-By: Claude <model> <[email protected]>`, last line
   `🤖 Generated with [Claude Code](https://claude.com/claude-code)`.
 - Everything players run is Rust. Python/Java only for dev tools and harness drivers in `tools/`.
 - Horizon-only features follow [docs/design-system.md](docs/design-system.md) and are off by default where
@@ -27,6 +30,8 @@ Feature → files → harness for the most-changed areas: [docs/architecture.md]
   change), none for a fix. Agents never add `release-now`: the maintainer decides it. Merges ship in batches of 5, or after
   6 hours ([docs/release-flow.md](docs/release-flow.md)).
 - Contributors first: `gh pr list --state open --search <area>` before you start; never duplicate theirs.
+- **Claim before you start**: comment `/claim` on the issue (no issue yet: open one, then claim it). An assigned
+  issue is taken: pick another. `/unclaim` when you stop; a claim with no open PR linking it is released after 5 days.
 
 ## Crates
 
@@ -34,7 +39,12 @@ Game workspace (root `Cargo.toml`); `launcher/` and `crates/horizon-telemetry-se
 
 | Crate | Owns |
 |---|---|
-| `horizon-client` | The game: a lib (`src/lib.rs`, ~190 flat modules) and the bin (`src/main.rs` → `game.rs` + `game/`), plus `horizon-ctl` (`src/bin/horizon-ctl/`). Also the dedicated server (`--dedicated`) |
+| `horizon-client` | The game: a lib (`src/lib.rs`, ~100 flat modules: gameplay, networking, title screens) and the bin (`src/main.rs` → `game.rs` + `game/`), plus `horizon-ctl` (`src/bin/horizon-ctl/`). Also the dedicated server (`--dedicated`) |
+| `horizon-items` | Blocks and items below gameplay: `blocks.rs` (block facts), `items.rs`, `item_data.rs` (components), `enchant.rs`, `cooldowns.rs`, `bundle.rs`, `item_nbt.rs`. Re-exported as `horizon_client::items`... |
+| `horizon-command` | Command parsing (Brigadier): the vanilla tree, argument types, selectors, suggestions, the tree's network form. Re-exported as `horizon_client::command` |
+| `horizon-client-core` | The client lib's bottom layer: `text.rs`, `lang.rs`, `snbt.rs`, `nbt_path.rs`, `component.rs`, `scoreboard.rs`, `bossbar.rs`, `gamerules.rs`, `block_entity_nbt.rs`, registry/particle/sound tables. Re-exported under the old paths (`horizon_client::text`...) |
+| `horizon-client-input` | Key bindings and key names, toggle keys, mouse options, controller settings and glyphs, the clipboard, window options (`keybinds.rs`, `gamepad.rs`, `mouse.rs`, `window.rs`...). Re-exported under the old paths |
+| `horizon-client-render` | The client's world data, rendering and screens (chunks, meshing, light, streaming, `gfx`, HUD, menus, settings): ~80 modules that horizon-client re-exports under the same paths. Nothing in it reaches gameplay |
 | `horizon-world` | Vanilla world data with no gameplay loop: NBT, regions, chunks, `datafix/`, `worldgen/`, `level/` (server-side block behaviour, ticks, redstone), entity physics, items, effects, food, damage |
 | `horizon-core` | Simulation primitives: Java `Random`s, `jmath` (HotSpot-exact `Math`), positions, noise, density, paletted storage, `version.rs` (the pinned version) |
 | `horizon-protocol` | Network protocol 777: codecs, framing, encryption, `packets/{handshake,status,login,configuration,play}.rs`, `entity_data.rs` |
@@ -42,9 +52,11 @@ Game workspace (root `Cargo.toml`); `launcher/` and `crates/horizon-telemetry-se
 | `horizon-prepare` | Builds `.local/horizon-client/26.3` from the player's own Minecraft install (runs the Java exporters) |
 | `horizon-server` | `horizon-server`: `server.toml`, CLI, supervisor of the headless game ([docs/hosting.md](docs/hosting.md)) |
 | `horizon-server-files` | `server.properties`, eula, ops/whitelist/bans, usercache |
+| `horizon-anticheat` | The dedicated server's anticheat, off by default: `[anticheat]` settings, violation levels, the checks' rules; the hub runs them (`lan/anticheat.rs`) ([docs/anticheat.md](docs/anticheat.md)) |
 | `horizon-friends`, `horizon-relay` | Play with Friends: invite codes, encrypted tunnel, the relay ([docs/play-with-friends.md](docs/play-with-friends.md)) |
-| `horizon-mods`, `horizon-mod-sdk`, `cargo-horizon-mod` | Sandboxed WebAssembly mods: runtime, SDK + WIT, `cargo horizon-mod` ([docs/mods.md](docs/mods.md)) |
+| `horizon-mods`, `cargo-horizon-mod` | Content mods (`.hmod`: manifest, content fence, no code), the registry index and `.hpack`, and `cargo horizon-mod` (`new`, `build`, `run`, `check`, `registry`) ([docs/mods.md](docs/mods.md)). Code mods are native, built by the launcher ([docs/native-mods.md](docs/native-mods.md)) |
 | `horizon-port-pack` | Porting Java modpacks ([docs/modpacks.md](docs/modpacks.md)) |
+| `horizon-shader-api` | Horizon's own WGSL shader packs ([docs/api/shaders.md](docs/api/shaders.md)): `horizon-shaders.toml`, the `.hshader` package; shared by the game, the launcher and the registry |
 | `horizon-shaders` | Shader packs (the `shaders/` folder format), rebuilt clean-room from a written spec of the format; no wgpu |
 | `horizon-theme` | Design tokens and fonts for the launcher, the game's own menus and the website |
 | `horizon-telemetry`, `horizon-telemetry-server`, `horizon-bench` | Opt-in data collection, its ingest server, the benchmark report format |
@@ -53,7 +65,8 @@ Game workspace (root `Cargo.toml`); `launcher/` and `crates/horizon-telemetry-se
 
 Other top-level folders: `tools/` (harnesses and dev scripts), `tests/` (Python unit tests: `python3 -m
 unittest discover -s tests`), `mods/horizon/src/test/java/dev/horizonlab/parity/` (Java oracles),
-`website/` (playhorizon.dev; its paths are relative to `website/`), `docs/`, `.github/workflows/`.
+`docs/`, `.github/workflows/`. The website (playhorizon.dev) is the private horizon-rust/horizon-site: its build
+reads `README.md`, `launcher/links.json`, `docs/api/`, `roadmap/roadmap.json` and `crates/horizon-theme/tokens.css` from main.
 
 ## Build and test fast
 
@@ -61,11 +74,12 @@ unittest discover -s tests`), `mods/horizon/src/test/java/dev/horizonlab/parity/
 python3 tools/pr_ready.py                  # the self-check: fmt, clippy -D warnings, touched crates' tests, harnesses; paste its block in the PR
 python3 tools/pr_ready.py --quick          # same without harnesses
 cargo test -p horizon-client --lib --bins --tests   # skips the 104 examples (pr_ready does this); `--doc` separately
+cargo test -p horizon-client --lib mod_content::tests:: -- --ignored   # the 5 slow content-root tests, #[ignore]d; pr_ready runs them when mod content, assets, blocks or items change
 cargo build --profile fast -p horizon-client        # optimized, quick to link: use it to play or run lan_e2e
 python3 tools/parity.py --changed origin/main       # the harnesses your branch can affect (CI's parity job)
 python3 tools/parity.py --changed-files paths.txt --list   # which harnesses cover these files, without running them
 python3 tools/parity.py mob_ai sculk       # named harnesses
-python3 tools/lan_e2e.py --check chest     # two real games over LAN (host in-frame); --server-thread for the host on its server thread
+python3 tools/lan_e2e.py --check chest     # two real games over LAN (server-thread host)
 python3 tools/agent_control_e2e.py         # horizon-ctl / MCP end to end
 ```
 
@@ -80,9 +94,6 @@ python3 tools/agent_control_e2e.py         # horizon-ctl / MCP end to end
 - What a change reruns (of 329 harnesses, measured 2026-10-23): a file of the game binary (`game.rs`, `game/`)
   ~25, a file of the client lib ~103, of `horizon-world` ~103–109, of `horizon-core` ~119. Plan for it.
 - Rust integration tests: `crates/horizon-client/tests/` (`lan_bot.rs`, `generation_saves.rs`, `streaming_meshes.rs`).
-- **macOS:** `cargo build/test --workspace` may fail to link the two wasm guest cdylibs (undefined
-  `horizon:mods/events` symbols) until #1446 lands: add `--exclude coords-hud --exclude horizon-mods-test-guest`.
-  Their real check is `cargo test -p horizon-mods` (builds them for `wasm32-unknown-unknown`).
 - Linux needs `libasound2-dev libudev-dev`; `--no-default-features` drops audio and controllers (the server build).
 - Run and drive the game (starts the `horizon-client` beside `horizon-ctl`; other arguments go to the game):
   `target/fast/horizon-ctl --socket $PWD/ctl.sock launch --world W --creative --offscreen --wait --resources $PWD/.local/horizon-client/26.3`,
@@ -91,6 +102,9 @@ python3 tools/agent_control_e2e.py         # horizon-ctl / MCP end to end
 
 ## Vanilla reference
 
+- Start parity work from the port ledger, not grep: `python3 tools/port_ledger.py issue N` (or `where
+  Class.method`, `what file:line`), and `check --base origin/main` before the PR. How:
+  [.claude/skills/vanilla-parity/SKILL.md](.claude/skills/vanilla-parity/SKILL.md), [docs/port-ledger.md](docs/port-ledger.md).
 - Decompiled sources: `.local/minecraft/26.3/sources/{client,server}/` (`python3 tools/lab.py decompile`).
 - Bytecode queries (callers through lambdas, every overload):
   `python3 tools/rea_vanilla.py method net.minecraft.world.level.block.DispenserBlock dispenseFrom`
@@ -102,30 +116,31 @@ python3 tools/agent_control_e2e.py         # horizon-ctl / MCP end to end
 
 ## horizon-client: where things live
 
-`L:` = lib (`crates/horizon-client/src/`), `G:` = bin (`crates/horizon-client/src/game/`). The lib can't see
+`L:` = lib (`crates/horizon-client/src/`, or `crates/horizon-client-render/src/` for the modules that crate holds, under
+the same `horizon_client::<module>` paths), `G:` = bin (`crates/horizon-client/src/game/`). The lib can't see
 `Game`; bin code reaches the lib as `horizon_client::<module>`.
 
 | Subsystem | Files |
 |---|---|
-| Game loop, tick, frame | `game.rs`: `fn run`, `impl ApplicationHandler for Game` (`window_event`, `about_to_wait`), `fn tick`, `fn tick_world`, `fn render`; L: `clock.rs`, `window.rs`, `spans.rs` |
+| Game loop, tick, frame | `game.rs`: `fn run`, `impl ApplicationHandler for Game` (`window_event`, `about_to_wait`), `fn tick`, `fn tick_world`, `fn render`; L: `clock.rs`, `spans.rs`; `horizon-client-input/src/window.rs` |
 | Rendering | L: `gfx.rs` (`Renderer::new`, `Renderer::render`), `gfx/` (cull, occlusion, translucency, upload, timing, lod, weather, stars, end_sky), `*.wgsl`, `particles.rs`, `block_entity_render.rs`, `item_render.rs`, `fog.rs`, `clouds.rs`, `camera.rs`, `first_person.rs`; G: `render_tick.rs`, `item_draw.rs` |
 | Chunks, streaming, light | L: `streaming.rs` (worker pool: generate, light, mesh), `world.rs`, `chunk.rs`, `chunk_map.rs`, `light.rs`, `mesher.rs` + `mesher/`, `vanillagen.rs` (binds horizon-world's generator), `lod.rs` + `lod/`, `ticket_levels.rs`; G: `world_loading.rs`, `postprocess.rs`; game.rs `fn update_world` |
 | World generation | `crates/horizon-world/src/worldgen/` (`generator*.rs`, `feature_graph.rs`, `structure/`, `carver/`) |
 | Block behaviour | `crates/horizon-world/src/level/` (`mod.rs`, `tick.rs`, `hooks.rs`, `redstone.rs`, `place.rs`, `interact.rs`); game.rs `fn tick_blocks`, `fn process_level_events` |
 | Mobs | L: `mobs.rs` (types), `mobs/` (`ai.rs`, `goals.rs`, `brain.rs`, `*_brain.rs`, `nav.rs`, `path.rs`, `species.rs`, `spawning.rs`, `render.rs`, `anim.rs`); G: `creatures.rs` (ticking, spawning, mob events), one file per mob family (`dragon.rs`, `wither.rs`, `villagers.rs`, `piglins.rs`, `golems.rs`...), `natural_spawning.rs` |
 | Other entities | L: `entities.rs`, `projectiles.rs`, `arrows.rs`; G: `boats.rs`, `minecarts.rs`, `mounts.rs`, `armor_stands.rs`, `paintings.rs`, `frames.rs`, `fireworks.rs`, `tnt.rs`, `explosion.rs` |
-| Player actions | game.rs (`fn use_hand`, `fn use_item`, `fn attack`, `fn tick_mining`, `fn break_block`); G: `hand.rs`, `combat.rs`, `consume.rs`, `potions.rs`, `shield.rs`, `crossbow.rs`, `trident.rs`, `fishing.rs`; L: `motion.rs` + `motion/` (movement), `collisions.rs`, `items.rs`, `item_data.rs` |
+| Player actions | game.rs (`fn use_hand`, `fn use_item`, `fn attack`, `fn tick_mining`, `fn break_block`); G: `hand.rs`, `combat.rs`, `consume.rs`, `potions.rs`, `shield.rs`, `crossbow.rs`, `trident.rs`, `fishing.rs`; L: `motion.rs` + `motion/` (movement), `collisions.rs`; crate `horizon-items`: `items.rs`, `item_data.rs`, `enchant.rs`, `blocks.rs` |
 | Inventory and containers | L: `menu.rs` (`AbstractContainerMenu.clicked`), `container_screen.rs`, `containers.rs`, `creative.rs`, `crafting.rs`, `recipe_book*.rs`, `stations.rs`, `merchant.rs`; game.rs `fn menu_ops`, `fn click_inventory`; G: `stations.rs`, `trading.rs`, `recipe_book.rs`, `machines.rs` |
-| Commands | parse: L: `command/` (`args.rs`, `selector.rs`, `tree_*.rs`, `vanilla.rs`); run: G: `commands.rs` (dispatch) + `commands/*.rs` (`admin`, `execute`, `items`, `players`, `world_cmds`...); L: `scoreboard_cmd.rs`, `data_cmd.rs`, `nbt_path.rs`; G: `functions.rs`, `command_blocks.rs` |
+| Commands | parse: crate `horizon-command` (`args.rs`, `selector.rs`, `tree_*.rs`, `vanilla.rs`); run: G: `commands.rs` (dispatch) + `commands/*.rs` (`admin`, `execute`, `items`, `players`, `world_cmds`...); L: `scoreboard_cmd.rs`, `data_cmd.rs`; `horizon-client-core`: `nbt_path.rs`, `scoreboard.rs`; G: `functions.rs`, `command_blocks.rs` |
 | UI screens | `Screen` enum in game.rs; L: `title.rs` + `title/`, `options_ui.rs`, `multiplayer.rs`, `pack_screen.rs`, `graphics_ui.rs`, `screen_draw.rs`, `ui.rs` (widgets), `hud.rs`, `hud_layout.rs`, `hud_overlays.rs`, `chat.rs`, `tab_list.rs`; G: `startup_menu.rs`, `screens.rs` (pause, death), `options.rs`, `lan_screen.rs`, `chat.rs`, `sign_edit.rs`, `books.rs` |
 | Multiplayer client | L: `net.rs` (network thread); G: `remote.rs` (`fn handle_packet`, `fn tick_remote`), `remote_*.rs` (mob data, objects, projectiles, vehicles, stations) |
 | LAN host / server side | L: `lan/` (`conn.rs` handshake + login threads, `hub.rs` + `hub/` play state, `chunks.rs`, `entity.rs`, `tracking.rs`, `guest.rs`, `playerdata.rs`); G: `lan.rs` (`LanHost`), `lan_actions.rs` (`fn as_guest`, `fn tick_guests`), `lan_*.rs` per feature, `lan_entities.rs` (tracked entities) |
 | Integrated server | G: `integrated.rs` (the server thread), `levels.rs` (one level per dimension, `fn tick_server`), `server_travel.rs` |
-| Dedicated server | G: `dedicated.rs`, `dedicated/status.rs`; crates `horizon-server-files`, `horizon-server` |
-| Save and load | L: `save.rs` (level.dat, regions, playerdata), `entity_nbt.rs`, `block_entity_nbt.rs`, `options_file.rs`; G: `saving.rs`, `persist.rs` (entities); `crates/horizon-world/src/{region.rs,nbt.rs,datafix/}` |
-| Input | game.rs `fn window_event`, `fn key_pressed`, `fn play_mouse`; L: `keybinds.rs`, `keymapping.rs`, `key_names.rs`, `mouse.rs`, `input.rs`, `interaction_input.rs`, `gamepad.rs`, `osk.rs`, `clipboard.rs`; G: `pad.rs`, `pad_menu.rs` |
+| Dedicated server | G: `dedicated.rs`, `dedicated/status.rs`; crates `horizon-server-files`, `horizon-server`, `horizon-anticheat` (L: `lan/anticheat.rs`) |
+| Save and load | L: `save.rs` (level.dat, regions, playerdata), `entity_nbt.rs`, `options_file.rs`; `horizon-client-core/src/block_entity_nbt.rs`; G: `saving.rs`, `persist.rs` (entities); `crates/horizon-world/src/{region.rs,nbt.rs,datafix/}` |
+| Input | game.rs `fn window_event`, `fn key_pressed`, `fn play_mouse`; crate `horizon-client-input` (`keybinds.rs`, `keymapping.rs`, `key_names.rs`, `mouse.rs`, `input.rs`, `interaction_input.rs`, `gamepad.rs`, `clipboard.rs`); L: `osk.rs`; G: `pad.rs`, `pad_menu.rs` |
 | Audio | L: `audio.rs` (mixer), `sound_engine.rs`, `sound_events.rs`, `music.rs`, `ambience.rs`; G: `music.rs`, `subtitle_hud.rs` |
-| Resource packs | L: `packs.rs` + `packs/`, `pack_screen.rs`, `atlas_sources.rs`, `sprites.rs`, `mipmap.rs`, `model_library.rs`, `font.rs`, `lang.rs`; crate `horizon-assets`; G: `packs.rs` |
+| Resource packs | L: `packs.rs` + `packs/`, `pack_screen.rs`, `atlas_sources.rs`, `sprites.rs`, `mipmap.rs`, `model_library.rs`, `font.rs`; `horizon-client-core/src/lang.rs`; crate `horizon-assets`; G: `packs.rs` |
 | Agent control | L: `control.rs` (socket), `bin/horizon-ctl/`; G: `control.rs`, `agent.rs`, `events.rs`, `ui_control.rs` ([docs/agent-control.md](docs/agent-control.md)) |
 | Mods | crate `horizon-mods`; G: `mods.rs`; L: `mod_content.rs`, `mod_list.rs` |
 | Horizon extras, settings | L: `extras.rs`, `graphics.rs`, `settings.rs`, `minimap.rs`; G: `extras.rs`, `tweaks.rs`, `options.rs` |
@@ -154,17 +169,18 @@ python3 tools/agent_control_e2e.py         # horizon-ctl / MCP end to end
    "Server thread" with one level per dimension; the window joins it as a client through memory (`remote`),
    exactly as a LAN guest or a dedicated server's player does. This is what players run. Open
    `[server-thread]` issues list the gaps left.
-2. **In-frame (`--in-frame`, `--no-server-thread` or `HORIZON_SERVER_THREAD=0`):** the window's `Game` ticks
-   the world itself, one level that follows the player (`fn enter_dimension`). Most harnesses test this path.
+2. **In-frame (`--in-frame`, `--no-server-thread` or `HORIZON_SERVER_THREAD=0`): DEPRECATED, never use it, it
+   will be removed soon.** The window's `Game` ticks the world itself, one level that follows the player
+   (`fn enter_dimension`). Compatibility does not matter: don't add features or fixes for it, don't write new
+   tests against it, and move code off it when you touch it. The deterministic rule fixtures still run on it
+   until they are ported.
 
-LAN guests and dedicated servers always use the server code, so a fix there serves both. Test both paths
-when you touch player-facing gameplay:
+LAN guests and dedicated servers always use the server code, so a fix there serves both. Test the server
+thread when you touch player-facing gameplay:
 
 ```sh
 cargo run --profile fast -p horizon-client -- --resources .local/horizon-client/26.3 --world T               # server thread
-cargo run --profile fast -p horizon-client -- --resources .local/horizon-client/26.3 --world T --in-frame    # in-frame
-python3 tools/lan_e2e.py --check <name>                  # host in-frame, guest is a server client
-python3 tools/lan_e2e.py --server-thread --check <name>  # host on its server thread (portals, levels, distance, lava need it)
+python3 tools/lan_e2e.py --check <name>                  # host on its server thread, guest is a server client
 python3 tools/parity.py dedicated_server server_entities server_player_damage
 ```
 

CONTRIBUTING.md

@@ -4,8 +4,13 @@ Thanks for helping. Horizon is Minecraft: Java Edition 26.3 rewritten in Rust, a
 everything is that **it plays exactly like vanilla**. This page is the short version of how we work; questions are
 welcome on [Discord](https://discord.gg/HcTeMZxe5E).
 
-This repository holds the game, the launcher and the website, plus the tools, tests and docs that build, check and
-release them. Anything else (videos, Discord and other community material) lives elsewhere.
+This repository holds the game and the launcher, plus the tools, tests and docs that build, check and release them.
+The website (playhorizon.dev) is built in a separate repository from this one's README, `docs/api/` and roadmap. Anything else (videos, Discord and other community material) lives elsewhere.
+
+**Where to start: [playhorizon.dev/hub](https://playhorizon.dev/hub).** It shows what is being done now and next
+([ROADMAP.md](ROADMAP.md) in the repository), the work board, good first tasks, and the forms to report a bug or
+suggest something. A pull request for a roadmap item carries its `roadmap:<id>` label; ideas go to the suggestion
+queue (the hub, or `/suggest` on Discord) rather than to issues, which are for bugs.
 
 ## Build it
 
@@ -39,6 +44,8 @@ probe against Horizon, and compares their outputs. There are about 290 of them.
 
 Never commit game files, decompiled source or prepared resources (`.local/`): `tools/check_public_tree.py` rejects
 them (`git config core.hooksPath .githooks` runs it before every commit).
+The pre-push hook checks the full history reachable from the branches and tags being pushed. Run
+`python3 tools/check_public_tree.py --history` to audit the history of all local refs.
 
 ## Only original code
 
@@ -67,6 +74,19 @@ including examples. The dependency scope includes optional, platform, build and
 Tests run library, binary, integration and doc tests without building unrelated example executables. Shared Cargo
 configuration and toolchain changes select the whole workspace; CI also keeps its workspace-wide checks.
 
+## Claim before you start
+
+Work is tracked in GitHub issues, and an issue that is assigned is taken (so is one with the `in progress` label:
+claimed on Discord with Kira's `/claim`): pick another, or ask its holder in the thread. Before you start, comment
+**`/claim`** on the issue; you are assigned at once, no role needed. No issue for your work yet? Open one (a line is
+enough), then claim it. `/unclaim` gives it back.
+
+A claim with no open pull request linking the issue (`Fixes #123` in the description, or a draft) is released after
+5 days, with a comment: open a draft early. You can hold 5 open issues at a time. Agents claim the same way.
+
+When your pull request changes the same functions as another open one, or closes the same issue, a bot comment names
+it (edited on every push, never repeated): talk to its author in the thread before you both finish the same work.
+
 ## Pull requests
 
 - **Small.** One change per pull request, under about 500 lines of code where you can; split bigger work into
@@ -75,10 +95,17 @@ configuration and toolchain changes select the whole workspace; CI also keeps it
   can see.
 - **Tick "Allow edits by maintainers".** When something small is left (a lint, a rebase, a nit) we push the fixup
   ourselves instead of sending it back to you; only design questions come back.
-- **Labels** (we set them if you can't): `feature` when players get something new (it appears under "New" in the
-  release notes), `skip-release` when players see no change (tooling, docs, tests), nothing for a fix.
+- **Tick its kind** in the template: `parity` (Horizon now does what vanilla does), `bug` (a crash or breakage),
+  `perf`, `feature` (new for players), `extra` (Horizon-only, off by default), `tooling` or `docs`. A workflow sets
+  that label, and area labels (`launcher`, `mobs`, `worldgen`, `rendering`...) from the paths you change.
+  `label:parity` is the list of real progress toward vanilla.
+- **Release labels** (we set them if you can't): `feature` also puts it under "New" in the release notes,
+  `skip-release` when players see no change (tooling, docs, tests), nothing for a fix.
   `release-now` is for crash fixes that shouldn't wait. pr_ready suggests one.
 
+Who reviews and merges: the Horizon Team, on CI for ordinary pull requests; risky ones (saves, network, world
+generation, the launcher's updates) wait for a local proof first ([merging](docs/release-flow.md#merging)).
+
 Every merge to main is released automatically ([release flow](docs/release-flow.md)), so main always stays playable.
 How agents, checks, releases and signed updates keep this safe: [security](docs/security.md).
 
@@ -91,5 +118,5 @@ new pushes, we add it again.
 
 ## Talk to us
 
-[Discord](https://discord.gg/HcTeMZxe5E) for questions and ideas, [issues](https://github.com/ludovic111/horizon/issues)
-for bugs. If you want to take something on, say so in its issue so nobody else starts the same work.
+[Discord](https://discord.gg/HcTeMZxe5E) for questions and ideas, [issues](https://github.com/horizon-rust/horizon/issues)
+for bugs. To take something on, `/claim` its issue ([above](#claim-before-you-start)).

Cargo.toml

@@ -1,6 +1,37 @@
 [workspace]
-exclude = ["launcher", "crates/horizon-telemetry-server", "third_party/wgpu-hal"]
-members = ["crates/horizon-core", "crates/horizon-dualsense", "crates/horizon-threads", "crates/horizon-world", "crates/horizon-client", "crates/horizon-server-files", "crates/horizon-server", "crates/horizon-bots", "crates/horizon-assets", "crates/horizon-protocol", "crates/horizon-theme", "crates/horizon-prepare", "crates/horizon-telemetry", "crates/horizon-bench", "crates/horizon-friends", "crates/horizon-relay", "crates/horizon-mod-sdk", "crates/horizon-mods", "crates/horizon-mods/tests/guest", "crates/cargo-horizon-mod", "crates/horizon-port-pack", "crates/horizon-shaders", "crates/horizon-release-sign", "crates/horizon-mod-sdk/examples/coords-hud", "xtask"]
+exclude = ["launcher", "crates/horizon-telemetry-server", "crates/horizon-mod-registry", "third_party/wgpu-hal"]
+members = [
+    "crates/horizon-core",
+    "crates/horizon-dualsense",
+    "crates/horizon-threads",
+    "crates/horizon-hdr",
+    "crates/horizon-world",
+    "crates/horizon-client",
+    "crates/horizon-client-core",
+    "crates/horizon-client-input",
+    "crates/horizon-client-render",
+    "crates/horizon-command",
+    "crates/horizon-items",
+    "crates/horizon-server-files",
+    "crates/horizon-anticheat",
+    "crates/horizon-server",
+    "crates/horizon-bots",
+    "crates/horizon-assets",
+    "crates/horizon-protocol",
+    "crates/horizon-theme",
+    "crates/horizon-prepare",
+    "crates/horizon-telemetry",
+    "crates/horizon-bench",
+    "crates/horizon-friends",
+    "crates/horizon-relay",
+    "crates/horizon-mods",
+    "crates/cargo-horizon-mod",
+    "crates/horizon-port-pack",
+    "crates/horizon-shaders",
+    "crates/horizon-shader-api",
+    "crates/horizon-release-sign",
+    "xtask",
+]
 resolver = "2"
 
 [workspace.package]
@@ -19,8 +50,10 @@ large_enum_variant = "allow"
 # wgpu-hal 30.0.1 with gfx-rs/wgpu#10124: wgpu 30 creates a Vulkan descriptor
 # pool with no pool sizes while it creates the device, which Vulkan allows only
 # since 1.3.215, and Intel's Windows driver for 6th-10th gen iGPUs (HD 520/530,
-# UHD 620/630) crashes on it with an access violation (#746). Drop this and the
-# folder once a wgpu release has the fix.
+# UHD 620/630) crashes on it with an access violation (#746). It also fixes the
+# Metal backend's lookup of the CoreGraphics HDR colour space names, which handed
+# CoreGraphics a symbol's address as the string and crashed HDR output on macOS.
+# Drop this and the folder once a wgpu release has both fixes.
 [patch.crates-io]
 wgpu-hal = { path = "third_party/wgpu-hal" }
 

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2026 Ludovic
+Copyright (c) 2026 Ludovic Marie and the Horizon contributors
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -1,12 +1,13 @@
 <p align="center">
-  <img src="docs/media/banner.webp" alt="Horizon: Minecraft: Java Edition 26.3, rewritten in Rust and checked against vanilla by 281 differential harnesses" width="100%">
+  <img src="docs/media/banner.webp" alt="Horizon: Minecraft: Java Edition 26.3, rewritten in Rust and checked against vanilla by more than 300 differential harnesses" width="100%">
 </p>
 
 <p align="center">
-  <a href="https://github.com/ludovic111/horizon/actions/workflows/ci.yml"><img src="https://github.com/ludovic111/horizon/actions/workflows/ci.yml/badge.svg?branch=main" alt="CI"></a>
+  <a href="https://github.com/horizon-rust/horizon/actions/workflows/ci.yml"><img src="https://github.com/horizon-rust/horizon/actions/workflows/ci.yml/badge.svg?branch=main" alt="CI"></a>
   <img src="https://img.shields.io/badge/Minecraft-Java%2026.3-5D9C3F" alt="Minecraft Java 26.3">
   <img src="https://img.shields.io/badge/Rust-stable-B7410E?logo=rust&logoColor=white" alt="Rust">
   <img src="https://img.shields.io/badge/vanilla%20parity-100%25-F0795A" alt="Vanilla parity 100%">
+  <a href="#project-status"><img src="https://img.shields.io/badge/player--visible%20gaps-833%20open-F0795A" alt="Player-visible gaps open"></a>
   <img src="https://img.shields.io/badge/platform-Linux%20%7C%20macOS%20%7C%20Windows-2A2470" alt="Linux, macOS and Windows">
   <a href="LICENSE"><img src="https://img.shields.io/badge/license-MIT-3B2F7E" alt="MIT license"></a>
 </p>
@@ -15,22 +16,23 @@
   <a href="https://playhorizon.dev"><b>Website</b></a> ·
   <a href="#download"><b>Download</b></a> ·
   <a href="https://playhorizon.dev/docs/"><b>Documentation</b></a> ·
-  <a href="https://github.com/ludovic111/horizon/releases"><b>Release notes</b></a> ·
+  <a href="https://github.com/horizon-rust/horizon/releases"><b>Release notes</b></a> ·
+  <a href="ROADMAP.md"><b>Roadmap</b></a> ·
   <a href="#project-status"><b>Project status</b></a> ·
   <a href="#contributing"><b>Contributing</b></a>
 </p>
 
 # Horizon
 
-Horizon is Minecraft: Java Edition 26.3 rewritten in Rust: a native game that reads the same worlds, follows the same rules and generates the same terrain as the Java game, and is checked against it by 281 differential harnesses. You play it through a small launcher, on the files from your own copy of Minecraft. It is free, open source and unofficial.
+Horizon is Minecraft: Java Edition 26.3 rewritten in Rust: a native game that reads the same worlds, follows the same rules and generates the same terrain as the Java game, and is checked against it by more than 300 differential harnesses. You play it through a small launcher, on the files from your own copy of Minecraft. It is free, open source and unofficial.
 
 > Not an official Minecraft product. Not approved by or associated with Mojang or Microsoft. Horizon contains no Minecraft code, assets or data: you need your own legally obtained copy of Minecraft: Java Edition 26.3.
 
 ## Download
 
-Horizon is installed through **the Horizon launcher**. Get it from [playhorizon.dev](https://playhorizon.dev) (the Download button picks your system) or from [the launcher releases](https://github.com/ludovic111/horizon/releases?q=launcher-v&expanded=true), for Linux x86-64, macOS on Apple Silicon or Windows x64. The launcher installs and updates the game, prepares its files from your own copy of Minecraft, and updates itself.
+Horizon is installed through **the Horizon launcher**. Get it from [playhorizon.dev](https://playhorizon.dev) (the Download button picks your system) or from [the launcher releases](https://github.com/horizon-rust/horizon/releases?q=launcher-v&expanded=true), for Linux x86-64, macOS on Apple Silicon or Windows x64. The launcher installs the game and keeps it up to date with each new build (Horizon ships on one channel, the Nightly), prepares its files from your copy of Minecraft (your own install, or downloaded from Mojang for your account), and updates itself.
 
-**You need** Minecraft: Java Edition 26.3, played once (the official launcher, Prism, MultiMC and other launchers all work); a Java 25 JDK, for the one-time preparation; and a GPU with Vulkan on Linux and Windows, or any Apple Silicon Mac. Step by step, with macOS's first-open prompt and the first launch: [Install and first launch](https://playhorizon.dev/docs/install).
+**You need** a Microsoft account that owns Minecraft: Java Edition (the launcher signs in with it, as other launchers do; see [Microsoft account](docs/microsoft-account.md)) and a GPU with Vulkan or OpenGL 3.3 on Linux, Vulkan or DirectX 12 on Windows, or any Apple Silicon Mac. Nothing else: with no Minecraft on your computer, Play downloads 26.3 and the Java it needs from Mojang for your account, as the official launcher does, then prepares it once. An install you already have (the official launcher, Prism, MultiMC and other launchers all work) is used instead. Step by step, with macOS's first-open prompt and the first launch: [Install and first launch](https://playhorizon.dev/docs/install).
 
 <table>
   <tr>
@@ -45,9 +47,9 @@ The [documentation](https://playhorizon.dev/docs/) covers each of these.
 
 - **The game:** singleplayer with vanilla's world generation, mobs, villagers, raids, redstone, every command, the HUD and the recipe book, on saves in vanilla's format. Worlds from 1.8 to 26.2 are upgraded as vanilla does. [Status table](#project-status).
 - **Horizon's own extras:** new menus (vanilla's are one setting away), graphics presets, distant terrain up to 1024 chunks, controller support, optional zoom, minimap and more, all off by default where they would change the vanilla look. See [Settings](https://playhorizon.dev/docs/settings).
-- **Resource packs and data packs:** resource packs work, and data packs load functions, predicates and item modifiers.
-- **Playing with others:** invite friends from the pause menu's Friends button with a code, Open to LAN, and joining offline-mode servers. Horizon cannot sign in to a Microsoft account yet, so it cannot join servers that check accounts. See [Multiplayer](https://playhorizon.dev/docs/multiplayer).
-- **Mods:** Horizon has its own mod system (Rust compiled to WebAssembly). Java mod jars do not run. See [Mods and data packs](https://playhorizon.dev/docs/mods).
+- **Resource packs and data packs:** resource packs work, and data packs load functions, predicates, item modifiers and world generation, taller levels included (vanilla's biomes for now).
+- **Playing with others:** invite friends from the pause menu's Friends button with a code, Open to LAN, and joining servers, online-mode ones with the Microsoft account the launcher signs in with. See [Multiplayer](https://playhorizon.dev/docs/multiplayer).
+- **Mods:** content mods add blocks, items and data, and native mods change the game's own Rust code, built by the launcher on your copy, with no Rust to install. Horizon's own (Zoom, FPS Counter, Keystrokes, Minimap, Recipes and Coordinates HUD) are native mods. Java mod jars do not run in Horizon. See [Mods and data packs](https://playhorizon.dev/docs/mods).
 
 Screenshots, captured in the Rust client itself with vanilla assets and no mods or shaders:
 
@@ -92,13 +94,13 @@ Commands block until the action is done and reply with what happened; errors are
 
 For developers. Requirements: Rust 1.90 or newer, Python 3.10 or newer, JDK 25, and on Linux the ALSA and udev development headers (`libasound2-dev libudev-dev` on Debian and Ubuntu). Development and the vanilla harnesses run on Linux.
 
-Horizon contains no game files and never downloads them. It builds its resources from **your own copy** of Minecraft: Java Edition 26.3, verified against the checksums in `research-lock.json`:
+Horizon contains no game files, and `horizon-prepare` never downloads them (the launcher downloads them from Mojang only for a signed-in account that owns the game). It builds its resources from **your own copy** of Minecraft: Java Edition 26.3, verified against the checksums in `research-lock.json`:
 
 1. **Client:** install Java Edition with the official launcher and play 26.3 once. Horizon reads `versions/26.3/`, `libraries/` and `assets/` from the launcher's game directory (`~/.minecraft` on Linux). If yours lives elsewhere, pass `--minecraft-dir` or set `HORIZON_MINECRAFT_DIR`.
 2. **Server jar:** the 26.3 server jar, from the `downloads.server.url` in your launcher's `versions/26.3/26.3.json` (or [minecraft.net/download/server](https://www.minecraft.net/en-us/download/server) while 26.3 is the current release). Pass it with `--server-jar` or set `HORIZON_SERVER_JAR`. It is only needed the first time.
 
 ```sh
-git clone https://github.com/ludovic111/horizon.git
+git clone https://github.com/horizon-rust/horizon.git
 cd horizon
 cargo run --release -p horizon-prepare -- --prepare --server-jar ~/Downloads/server.jar   # needs JDK 25
 cargo run --release -p horizon-prepare -- sounds   # optional: sounds from your launcher install
@@ -109,6 +111,10 @@ Everything prepared lands in the gitignored `.local/`. It is derived from the ga
 
 The client starts on the title screen. Command-line options (`--world`, `--seed`, `--creative`, `--render-distance`, `--dedicated`), controls, scripting through `horizon-ctl` and the architecture are described in [the native client guide](docs/native-client.md). The rest of the developer documentation is indexed in [docs/README.md](docs/README.md), including [the parity workflow](docs/parity-workflow.md).
 
+## Roadmap
+
+What is being done now, what comes next and where you can help, in plain words and in technical detail: [ROADMAP.md](ROADMAP.md). [playhorizon.dev/hub](https://playhorizon.dev/hub) shows it with the work board, the journal of what shipped and how to help.
+
 ## Contributing
 
 Issues and pull requests are welcome: see [CONTRIBUTING.md](CONTRIBUTING.md) for how we work (vanilla first, small pull requests, labels), or [the contributing guide](https://playhorizon.dev/docs/contributing) on the site. Questions and ideas: [Discord](https://discord.gg/HcTeMZxe5E). Before opening a pull request, run the self-check and paste the block it prints:
@@ -122,6 +128,8 @@ It runs rustfmt, clippy with warnings denied, the tests of the crates you touche
 
 ## Project status
 
+**Player-visible gaps: 833 open** of the 833 the [port ledger](tools/port_ledger.py) found, reading every vanilla 26.3 method against Horizon's code: vanilla behaviour a player would notice that Horizon doesn't have yet. By area: Screens, HUD and client packets [197](https://github.com/horizon-rust/horizon/issues/3518); Entity and block rendering, models [129](https://github.com/horizon-rust/horizon/issues/3519); Animals [110](https://github.com/horizon-rust/horizon/issues/3512); Server and players on the server [106](https://github.com/horizon-rust/horizon/issues/3520); Blocks, redstone and fluids [86](https://github.com/horizon-rust/horizon/issues/3516); Entities, projectiles, vehicles and decorations [64](https://github.com/horizon-rust/horizon/issues/3514); Monsters and bosses [53](https://github.com/horizon-rust/horizon/issues/3513); Mob AI, villagers and raids [35](https://github.com/horizon-rust/horizon/issues/3521); World, world generation and saves [32](https://github.com/horizon-rust/horizon/issues/3517); Items, enchantments and inventories [21](https://github.com/horizon-rust/horizon/issues/3515). This number goes down as gaps close (`tools/parity_gaps.py`); the harness results below say that what is tested matches.
+
 The table below is the project's own audit of each subsystem. Every subsystem now matches vanilla in every harness that compares it. 100% means 100% of what the harnesses compare, not proof that nothing else differs. The remaining known differences are listed below.
 
 ### Java parity: 100%
@@ -134,6 +142,11 @@ average; `tests/test_parity.py` keeps it in sync with this table. Last audited
 rerun whenever one of its inputs changed, and the Mac mini now runs every one of
 them too (Rust uses Java's own float maths on each platform).
 
+The harnesses measure behaviour. A second measure is method by method: the [port ledger](tools/port_ledger.py)
+lists every method of vanilla 26.3 next to the Rust functions that port it, with a verdict for each one
+(ported, folded into another function, missing, or needing no port), and the untested ports. Run
+`python3 tools/port_ledger.py build`, then `coverage`, with the vanilla data in `.local/`.
+
 | Subsystem | Score | Main gaps |
 | --- | ---: | --- |
 | Window, input and game loop | 1 | None: the game loop, options, camera, auto-jump, toggle sprint/sneak, local input and the frame limiter match vanilla |
@@ -153,7 +166,7 @@ them too (Rust uses Java's own float maths on each platform).
 
 ### Known issues
 
-Horizon can't sign in to a Microsoft account yet, so it can't join online-mode servers (it joins offline-mode ones); skins served over https show the default skin unless already cached; pack icons show the unknown-pack texture in game; the creative hotbar keys (C/X) aren't wired to the hotbar loader; item tooltips lack attribute lines.
+Skins served over https show the default skin unless already cached; pack icons show the unknown-pack texture in game; item tooltips lack attribute lines.
 
 ## Licence
 

ROADMAP.md

@@ -0,0 +1,916 @@
+# Horizon roadmap
+
+<!-- Generated by tools/roadmap.py from roadmap/roadmap.toml: edit that file, then run `python3 tools/roadmap.py build`. -->
+
+What is being done on Horizon, what comes next and where you can help. There are no dates: things are Now, Next or Later. Each item is said in plain words, with the technical picture folded under it. The same roadmap, with a Simple / Technical switch, the board, the journal and how to help, is on [playhorizon.dev/hub](https://playhorizon.dev/hub). Pull requests carry the `roadmap:<id>` label of their item.
+
+## At a glance
+
+Horizon is Minecraft: Java Edition 26.3 rewritten from scratch in Rust, so it runs faster on the same computer. Single player, LAN, servers, resource packs and Horizon's own mods work today, on your own copy of the game.
+
+**Being done now**
+
+- **Steady frames at long render distances**: Making Horizon faster than vanilla on every computer, with smooth camera movement even at 32 chunks, by spreading the work better over the processor's cores.
+- **Modpacks' world generation, natively**: Making the world-generation mods of popular modpacks (new structures, YUNG's dungeons and mineshafts, packs built on Lithostitched) generate their worlds in Horizon, natively and fast.
+- **Single player as a server: the last differences**: Single player now runs a small server in the background, as vanilla does. We are fixing what still behaves differently there; every fix also works for LAN and server players.
+- **Vanilla parity: the player-visible gaps, closed**: Every method of the Java game is tracked with where Horizon does it, and the differences players can see are being closed, list by list: mobs, blocks, items, screens, rendering, servers.
+- **Mods**: Mods for Horizon, as one line of work led by the modding team: native mods the launcher builds into your game, mods on servers, mod screens and settings, tools for mod makers, the registry and machines.
+
+**Next**: Fresh benchmarks against vanilla; Faster world creation and entry on small CPUs; Low-end computers: Steam Deck, old Macs, 8 GB; Native upscaling; Server console, bans and a full admin API; Hosting polish: Windows service, safe updates; One single-player path: remove the in-frame world; Faster block lookups; Playing on servers: everything shows as it should; Shader packs, written again from scratch; A new launcher design; Splitscreen.
+
+**How to help**: Play it and tell us what differs from vanilla (Discord or GitHub), run the benchmark on your computer, vote for what you want next, or pick one of the Help wanted items.
+
+**Developers**: Read CONTRIBUTING.md, pick a Help wanted item or a To do card, check vanilla's code for the behaviour, and paste the block `python3 tools/pr_ready.py` prints in your pull request.
+
+## Now
+
+### Performance
+
+#### Steady frames at long render distances
+
+Making Horizon faster than vanilla on every computer, with smooth camera movement even at 32 chunks, by spreading the work better over the processor's cores.
+
+Owner: [ludovic111](https://github.com/ludovic111) · Tracking: [#3909](https://github.com/horizon-rust/horizon/issues/3909)
+
+<details><summary>Technical</summary>
+
+Frame pacing at render distance 32 ([#678](https://github.com/horizon-rust/horizon/issues/678)): long frames come from work competing with the render thread. In review: no main-thread tick stutter at high render distances ([#3827](https://github.com/horizon-rust/horizon/issues/3827)), each proto chunk's light view built once ([#3815](https://github.com/horizon-rust/horizon/issues/3815)), video memory handed back by the vertex arena ([#3466](https://github.com/horizon-rust/horizon/issues/3466)), chunk batches assembled on helper threads ([#3036](https://github.com/horizon-rust/horizon/issues/3036)), free structure starts in the generation workers ([#1760](https://github.com/horizon-rust/horizon/issues/1760)). Still open: far terrain at 48 to 64 chunks ([#718](https://github.com/horizon-rust/horizon/issues/718)) and CPU-bound fields of block entities ([#717](https://github.com/horizon-rust/horizon/issues/717)). Every change shows before and after numbers from `tools/perf_bench.py` against vanilla 26.3 ([docs/benchmark.md](docs/benchmark.md)).
+
+</details>
+
+#### Servers that hold 20 TPS with 50 to 100 players
+
+Servers that keep 20 ticks per second with 50 to 100 players. Today Horizon holds it up to 50 bots and drops to about 10 at 100.
+
+Owner: [ludovic111](https://github.com/ludovic111) · Tracking: [#3910](https://github.com/horizon-rust/horizon/issues/3910)
+
+<details><summary>Technical</summary>
+
+Measured against vanilla on equal work ([docs/server.md](docs/server.md), Scale): Horizon is ahead with few players and when exploring, but vanilla's tick is shorter with 25 to 50 players near spawn. Ideas on the list: send entity changes instead of rebuilding every entity each tick (about 15 percent), fewer memory reads in random ticks and collision scans, cheaper item collision checks, mob AI and natural spawning. The bot benchmark (`horizon-bots`) is the proof.
+
+More: [#3847](https://github.com/horizon-rust/horizon/issues/3847) · [#2608](https://github.com/horizon-rust/horizon/issues/2608)
+
+</details>
+
+### Modpacks
+
+#### Modpacks' world generation, natively
+
+Making the world-generation mods of popular modpacks (new structures, YUNG's dungeons and mineshafts, packs built on Lithostitched) generate their worlds in Horizon, natively and fast.
+
+Owner: [ThatCakeIsAPie](https://github.com/ThatCakeIsAPie) · Tracking: [#3913](https://github.com/horizon-rust/horizon/issues/3913)
+
+<details><summary>Technical</summary>
+
+`horizon-port-pack` carries a pack's data-driven content over, and 26.2 data packs are upgraded to 26.3's format ([#3369](https://github.com/horizon-rust/horizon/issues/3369)). In review: worlds taller than 32 sections and each level's shape from its dimension type ([#3480](https://github.com/horizon-rust/horizon/issues/3480), [#3488](https://github.com/horizon-rust/horizon/issues/3488)), data-pack biomes in local and remote worlds ([#3491](https://github.com/horizon-rust/horizon/issues/3491)), block state providers ([#3802](https://github.com/horizon-rust/horizon/issues/3802)), surface rules by biome id ([#3366](https://github.com/horizon-rust/horizon/issues/3366)), Lithostitched's pool and processor modifiers ([#1777](https://github.com/horizon-rust/horizon/issues/1777)). Mods whose Java code does more than world generation don't run ([docs/modpacks.md](docs/modpacks.md)).
+
+</details>
+
+### Mods and API
+
+#### Mods
+
+Mods for Horizon, as one line of work led by the modding team: native mods the launcher builds into your game, mods on servers, mod screens and settings, tools for mod makers, the registry and machines.
+
+Owner: [levzzz5154](https://github.com/levzzz5154) · Tracking: [#3911](https://github.com/horizon-rust/horizon/issues/3911)
+
+<details><summary>Technical</summary>
+
+One item for all modding work ([#3911](https://github.com/horizon-rust/horizon/issues/3911)), led by levzzz5154 with vladislav_hagen; the order between the parts is theirs. Native mods on stable hook points (game/native_hooks.rs, [#3345](https://github.com/horizon-rust/horizon/issues/3345), [#3346](https://github.com/horizon-rust/horizon/issues/3346), [#3434](https://github.com/horizon-rust/horizon/issues/3434), [#3435](https://github.com/horizon-rust/horizon/issues/3435)) built by the launcher ([#3388](https://github.com/horizon-rust/horizon/issues/3388), [#3855](https://github.com/horizon-rust/horizon/issues/3855)); server-side hooks ([#3878](https://github.com/horizon-rust/horizon/issues/3878), [#3706](https://github.com/horizon-rust/horizon/issues/3706)); mod-owned screens, input and drawing; tools for mod makers (templates, `native.py check`); the registry ([#1634](https://github.com/horizon-rust/horizon/issues/1634), [#1642](https://github.com/horizon-rust/horizon/issues/1642), [#1659](https://github.com/horizon-rust/horizon/issues/1659)); machines with inventories and menus ([#1189](https://github.com/horizon-rust/horizon/issues/1189)); mods that read and change the world through the server. [docs/native-mods.md](docs/native-mods.md).
+
+More: [#3351](https://github.com/horizon-rust/horizon/issues/3351) · [#3353](https://github.com/horizon-rust/horizon/issues/3353) · [#3360](https://github.com/horizon-rust/horizon/issues/3360) · [#1596](https://github.com/horizon-rust/horizon/issues/1596) · [#1635](https://github.com/horizon-rust/horizon/issues/1635)
+
+</details>
+
+### Gameplay parity
+
+#### Single player as a server: the last differences
+
+Single player now runs a small server in the background, as vanilla does. We are fixing what still behaves differently there; every fix also works for LAN and server players.
+
+Owner: [ludovic111](https://github.com/ludovic111) · Tracking: [#3914](https://github.com/horizon-rust/horizon/issues/3914)
+
+<details><summary>Technical</summary>
+
+Since [#1514](https://github.com/horizon-rust/horizon/issues/1514) single player runs on the server thread (`game/integrated.rs`) and the window joins it as a client; `--in-frame` keeps the old path. The open `[server-thread]` issues list the gaps. In review: breeding's advancement and statistic ([#3873](https://github.com/horizon-rust/horizon/issues/3873)), the client's menu when the server replaces the player ([#3841](https://github.com/horizon-rust/horizon/issues/3841)), splashes when falling in water ([#3621](https://github.com/horizon-rust/horizon/issues/3621)). [docs/server-levels.md](docs/server-levels.md).
+
+</details>
+
+### Launcher
+
+#### Minecraft Java instances in the launcher
+
+Play the real Java game from the Horizon launcher too: vanilla and modded instances, any version, mods from Modrinth filtered to what fits, and your instances imported from other launchers.
+
+Owner: [ludovic111](https://github.com/ludovic111) · Tracking: [#3915](https://github.com/horizon-rust/horizon/issues/3915)
+
+<details><summary>Technical</summary>
+
+For an account that owns the game: any version downloaded with the Java it needs ([#3406](https://github.com/horizon-rust/horizon/issues/3406)), Java instances, the version list and the CLI ([#3395](https://github.com/horizon-rust/horizon/issues/3395)), the start command read from the version JSON ([#3419](https://github.com/horizon-rust/horizon/issues/3419)). Next: Play for a Java instance, Fabric and Quilt, then NeoForge and Forge; Modrinth with compatibility filtering and dependencies; imports from Prism, MultiMC, the CurseForge app, the Modrinth App, ATLauncher and the official launcher, each from its documented on-disk format.
+
+More: [#3506](https://github.com/horizon-rust/horizon/issues/3506)
+
+</details>
+
+### Code and tools
+
+#### A leaner codebase that builds faster
+
+Cleaning up Horizon's code: removing what nothing uses and making it quicker to build, so fixes and new features land faster.
+
+Owner: [ludovic111](https://github.com/ludovic111) · Tracking: [#3916](https://github.com/horizon-rust/horizon/issues/3916)
+
+<details><summary>Technical</summary>
+
+A review of the whole tree: dead code and stubs removed ([#1432](https://github.com/horizon-rust/horizon/issues/1432), [#1658](https://github.com/horizon-rust/horizon/issues/1658)), one probe binary per crate ([#1453](https://github.com/horizon-rust/horizon/issues/1453), [#1454](https://github.com/horizon-rust/horizon/issues/1454)), shared harness helpers ([#1448](https://github.com/horizon-rust/horizon/issues/1448)), clippy clean on the whole tree ([#1707](https://github.com/horizon-rust/horizon/issues/1707)). [docs/architecture.md](docs/architecture.md) maps each feature to its files and harnesses.
+
+</details>
+
+#### Vanilla parity: the player-visible gaps, closed
+
+Every method of the Java game is tracked with where Horizon does it, and the differences players can see are being closed, list by list: mobs, blocks, items, screens, rendering, servers.
+
+Owner: [kacpherek](https://github.com/kacpherek) · Tracking: [#3912](https://github.com/horizon-rust/horizon/issues/3912)
+
+<details><summary>Technical</summary>
+
+The port ledger ([tools/port_ledger.py](tools/port_ledger.py), tools/port_map/, [#3139](https://github.com/horizon-rust/horizon/issues/3139)) gives every 26.3 method a verdict and links the harnesses that cover it ([#3526](https://github.com/horizon-rust/horizon/issues/3526)). The player-visible gaps are ten lists, one per area ([#3512](https://github.com/horizon-rust/horizon/issues/3512) to [#3521](https://github.com/horizon-rust/horizon/issues/3521)); a fix translates the vanilla method, ticks its row and carries the `parity` label. Start from .claude/skills/vanilla-parity.
+
+More: [#3513](https://github.com/horizon-rust/horizon/issues/3513) · [#3514](https://github.com/horizon-rust/horizon/issues/3514) · [#3515](https://github.com/horizon-rust/horizon/issues/3515) · [#3516](https://github.com/horizon-rust/horizon/issues/3516) · [#3517](https://github.com/horizon-rust/horizon/issues/3517) · [#3518](https://github.com/horizon-rust/horizon/issues/3518) · [#3519](https://github.com/horizon-rust/horizon/issues/3519) · [#3520](https://github.com/horizon-rust/horizon/issues/3520)
+
+</details>
+
+## Next
+
+### Performance
+
+#### Fresh benchmarks against vanilla
+
+New public numbers comparing Horizon with vanilla on many kinds of computers, measured the same way every time, with a history that shows what each release changed.
+
+<details><summary>Technical</summary>
+
+Redo the comparison after the current performance work ([#1073](https://github.com/horizon-rust/horizon/issues/1073)); reliability, coverage and presentation ([#1346](https://github.com/horizon-rust/horizon/issues/1346)); a scene must count as loaded only once its first chunk arrives ([#1749](https://github.com/horizon-rust/horizon/issues/1749)). Next: a performance history across releases (an automatic comparison of each release with the last, on a timeline), more report fields (server TPS and MSPT, power, battery drain, temperature, throttling) and more hardware (a MacBook on battery, low-end laptops, community reports). Players' reports come in through `--benchmark` and `horizon-launcher data benchmark` ([docs/benchmark.md](docs/benchmark.md)).
+
+</details>
+
+#### Faster world creation and entry on small CPUs
+
+Creating a world and joining it should be quick even on a four-thread laptop, where a fresh world at 32 chunks can make you wait minutes for the first terrain.
+
+<details><summary>Technical</summary>
+
+Cut the per-column generation cost (noise sampling, surface rules, aquifers) and the lock convoy on structure starts, and leave one core free for the rest of the game as vanilla does ([#1760](https://github.com/horizon-rust/horizon/issues/1760) and [#1778](https://github.com/horizon-rust/horizon/issues/1778), in review, are listed under 'Steady frames at long render distances'). Still to profile on small CPUs: the first seconds of a fresh world deliver no chunk, and fluids remesh for about a minute after loading. Measured with `tools/perf_bench.py` ([docs/benchmark.md](docs/benchmark.md), [docs/profiling.md](docs/profiling.md)).
+
+</details>
+
+#### Low-end computers: Steam Deck, old Macs, 8 GB
+
+Horizon should run well on small machines: integrated graphics, the Steam Deck, older Macs and 8 GB of memory, with a battery mode that saves power on laptops.
+
+<details><summary>Technical</summary>
+
+Partly done: an opt-in 60 FPS cap with fewer workers on battery, Far Detail Reduced for integrated GPUs and animated textures on the GPU (both shipped). Left: measured targets and fixes per class of machine (memory use, worker counts, startup) on a Steam Deck, old Intel and Apple Silicon Macs and 8 GB computers, reported on the Benchmarks page.
+
+More: [docs/benchmark.md](docs/benchmark.md) · [https://playhorizon.dev/docs/performance](https://playhorizon.dev/docs/performance)
+
+</details>
+
+#### Native upscaling
+
+Draw the game at a lower resolution and sharpen it to your screen's size, in the way of FSR or DLSS, to gain frames on weaker graphics cards. An optional graphics setting.
+
+<details><summary>Technical</summary>
+
+A render-scale setting below the window size with an upscaler of our own that runs on every wgpu backend. Proof: frame time against native resolution on integrated GPUs, and screenshots for image quality. Issue [#1403](https://github.com/horizon-rust/horizon/issues/1403).
+
+More: [#3762](https://github.com/horizon-rust/horizon/issues/3762) · [#3763](https://github.com/horizon-rust/horizon/issues/3763) · [#3764](https://github.com/horizon-rust/horizon/issues/3764)
+
+</details>
+
+#### Faster block lookups
+
+Speeding up the code that reads and writes the blocks of the world, which almost everything in the game goes through: generation, lighting, meshing and ticking.
+
+<details><summary>Technical</summary>
+
+`PalettedContainer` and `PackedStorage` find an entry's word by multiply and shift instead of an integer division ([#1790](https://github.com/horizon-rust/horizon/issues/1790), [#1794](https://github.com/horizon-rust/horizon/issues/1794)); meshing looks up baked models by index, not by name ([#1747](https://github.com/horizon-rust/horizon/issues/1747)). Each change keeps the paletted storage harnesses identical and shows its microbenchmark ([docs/performance/paletted-container-access-results.md](docs/performance/paletted-container-access-results.md)).
+
+</details>
+
+### Servers and multiplayer
+
+#### Server console, bans and a full admin API
+
+Manage a server from a console, ban and pardon players, and drive it from other tools through a full admin API and an MCP server for AI agents.
+
+<details><summary>Technical</summary>
+
+`horizon-server console` (a text interface), `ban`, `pardon`, `ban-ip` and `mcp` over stdio. Admin API additions: the player list, kick, ban, op and whitelist, an SSE stream of logs and events, a text metrics endpoint, config GET and PATCH, backup delete and download. The panel's later features (bans, worlds, server.properties import, logs and crash reports, modpacks) and vanilla's management protocol (the JSON-RPC over WebSocket that the `management-server-*` keys configure), so vanilla's tools can manage a Horizon server. [docs/server.md](docs/server.md), [docs/api/server.md](docs/api/server.md).
+
+</details>
+
+#### Hosting polish: Windows service, safe updates
+
+Smoother hosting: a real Windows service, a backup before every update, backups that keep the world and each player's state, and a changed view distance or message without a restart.
+
+<details><summary>Technical</summary>
+
+A Windows service wrapper instead of the logon scheduled task; `backups.before_update`; hot reload of config for view distance and the message of the day (needs engine support); backups that keep world and player state ([#1808](https://github.com/horizon-rust/horizon/issues/1808), a contributor's draft, in review). [docs/hosting.md](docs/hosting.md), docs/server.md.
+
+</details>
+
+#### Playing on servers: everything shows as it should
+
+When you play on a server, other players, mobs, items and menus look and behave as in vanilla: skins, poses, item names, inventories and server networks.
+
+<details><summary>Technical</summary>
+
+Client-of-a-server fixes in `game/remote*.rs` and `horizon-protocol`: mobs' aggressive and item-use flags ([#1802](https://github.com/horizon-rust/horizon/issues/1802), [#1798](https://github.com/horizon-rust/horizon/issues/1798)), ghost items after a remote menu ([#1795](https://github.com/horizon-rust/horizon/issues/1795)), skins ([#1652](https://github.com/horizon-rust/horizon/issues/1652)), cookies and transfer packets for proxy networks ([#1650](https://github.com/horizon-rust/horizon/issues/1650)), firework boosts ([#1671](https://github.com/horizon-rust/horizon/issues/1671)), living-entity attributes and simulation distance ([#1731](https://github.com/horizon-rust/horizon/issues/1731)), styled item names ([#1702](https://github.com/horizon-rust/horizon/issues/1702)), primed TNT between updates ([#1710](https://github.com/horizon-rust/horizon/issues/1710)).
+
+</details>
+
+### Gameplay parity
+
+#### One single-player path: remove the in-frame world
+
+Single player will have one way to run, the server thread, so every fix works everywhere and there are fewer bugs. The older in-frame mode goes once everything passes without it.
+
+<details><summary>Technical</summary>
+
+`--in-frame` (also `--no-server-thread` and `HORIZON_SERVER_THREAD=0`) still ticks the world inside the window's `Game`, and most harnesses test that path. Delete it once `lan_e2e --server-thread` and the parity harnesses pass on the server thread, which also halves the bug surface. See also 'Single player as a server' and [docs/server-levels.md](docs/server-levels.md).
+
+</details>
+
+#### Splitscreen
+
+Play with a friend on the same screen, each with a controller.
+
+Owner: [martipops](https://github.com/martipops)
+
+<details><summary>Technical</summary>
+
+Issue [#2054](https://github.com/horizon-rust/horizon/issues/2054), built by martipops as a series: up to 16 local players on the server thread's multiplayer ([#3541](https://github.com/horizon-rust/horizon/issues/3541)), each controller driving its own player ([#3794](https://github.com/horizon-rust/horizon/issues/3794)), joining with a controller ([#3801](https://github.com/horizon-rust/horizon/issues/3801)), players in windows of their own ([#3825](https://github.com/horizon-rust/horizon/issues/3825)) and the profile page ([#3826](https://github.com/horizon-rust/horizon/issues/3826)).
+
+More: [#3777](https://github.com/horizon-rust/horizon/issues/3777)
+
+</details>
+
+### Rendering
+
+#### Shader packs, written again from scratch
+
+Shader packs were removed and are being rebuilt from scratch. They come back, off by default, once the best-known packs draw properly.
+
+<details><summary>Technical</summary>
+
+A clean-room rewrite in `horizon-shaderpack`, from the packs' public format documentation only: reading packs, the preprocessor and `.properties` files are merged ([#1584](https://github.com/horizon-rust/horizon/issues/1584), [#1585](https://github.com/horizon-rust/horizon/issues/1585), [#1586](https://github.com/horizon-rust/horizon/issues/1586)); translating programs to WGSL through naga, buffers, uniforms and the terrain, entity, sky, weather and hand stages are in review ([#1698](https://github.com/horizon-rust/horizon/issues/1698) to [#1801](https://github.com/horizon-rust/horizon/issues/1801)).
+
+More: [#1561](https://github.com/horizon-rust/horizon/issues/1561) · [#1771](https://github.com/horizon-rust/horizon/issues/1771) · [#1786](https://github.com/horizon-rust/horizon/issues/1786)
+
+</details>
+
+### Launcher
+
+#### A new launcher design
+
+A redesigned launcher: every button where you expect it, the fewest clicks to play, add an instance or add mods, smooth animations, and instant startup.
+
+Owner: [ludovic111](https://github.com/ludovic111)
+
+<details><summary>Technical</summary>
+
+Based on the site concept by the Team (Bricolage Grotesque, a night sky and an animated pixel sunset). Screens and flows are designed first, then small PRs; tokens in [crates/horizon-theme](crates/horizon-theme) and rules in [docs/design-system.md](docs/design-system.md), the game's vanilla look unchanged. Measured before and after: startup, frame time and idle CPU/GPU, reduced motion honoured. Mods screens separate Horizon native mods from Java mods; a running instance can be stopped from the launcher.
+
+More: [#3635](https://github.com/horizon-rust/horizon/issues/3635) · [#3636](https://github.com/horizon-rust/horizon/issues/3636) · [#3637](https://github.com/horizon-rust/horizon/issues/3637)
+
+</details>
+
+## Later
+
+### Performance
+
+#### Exact far terrain from real chunks
+
+Far terrain drawn from the world you really built and explored, caves and builds included, not only a preview from the seed.
+
+<details><summary>Technical</summary>
+
+Keep a 3D mip store on disk built from real chunks, drawn by the GPU beside the seed preview for areas nobody has visited. Written from scratch and measured before it is kept. Builds on Far Detail and the far-terrain levels of detail already shipped; the open work on them is [#718](https://github.com/horizon-rust/horizon/issues/718).
+
+</details>
+
+#### A batch of targeted optimisations
+
+Several smaller speed-ups, each measured: idle block entities that sleep, cheaper particles, faster structure placement, high-rate mice and very large texture packs.
+
+<details><summary>Technical</summary>
+
+Block entities and hoppers that skip work when idle (the hopper item scan is already skipped when no item is near); a particle frustum test first (also a parity gap), then particle quads built on the GPU; jigsaw shortcuts that skip blocked connectors and pool elements known not to fit, with layouts unchanged (trial chambers and ancient cities first); batched raw mouse input on Windows for 8000 Hz mice; a better atlas packer for huge resource packs (a 64x pack builds a 704 MiB atlas for 452 MiB of textures); sign-heavy scenes ([#1461](https://github.com/horizon-rust/horizon/issues/1461)). Profile first, keep what pays, show before and after numbers.
+
+More: [docs/profiling.md](docs/profiling.md)
+
+</details>
+
+### Modpacks
+
+#### Older Fabric and Forge mods
+
+Recognise mods built for versions before 26.1 in the mod browser, so they can be checked and carried over like newer ones.
+
+<details><summary>Technical</summary>
+
+A mapping table from intermediary and SRG names so pre-26.1 jars can be classified, and a rename for mod ids with dashes (`fabric-api`); the port step then treats them like newer jars ([docs/mod-browser.md](docs/mod-browser.md)).
+
+</details>
+
+#### A modpack's own resource and shader packs
+
+Importing a modpack also brings the resource packs and shader packs it ships with, where Horizon can use them.
+
+<details><summary>Technical</summary>
+
+Porting a pack carries data, assets and worldgen today; the resource packs and shader packs bundled with it are left out. Resource packs can be carried as they are; shader packs go through the converter ([docs/modpacks.md](docs/modpacks.md)).
+
+</details>
+
+#### Whole modpacks, such as ATM10, rewritten
+
+Rewriting a complete big modpack for Horizon so it runs far better than the original. Not a priority now: the work above comes first.
+
+<details><summary>Technical</summary>
+
+The project's first goal for modpacks: support them ten times better than vanilla and port any of them. It was set aside in favour of compatibility through the browser. What exists: ATM10's world generates and 42 of its 496 mods are carried at least in part ([docs/modpacks.md](docs/modpacks.md)). It depends on 'Mods with code' and the native mod API.
+
+</details>
+
+#### Running Java mods that aren't rewritten
+
+Run Java mods that nobody has rewritten for Horizon yet, through a bridge or a converter. Hard and not started: the Convert button and native rewrites come first.
+
+<details><summary>Technical</summary>
+
+Earlier research ([#527](https://github.com/horizon-rust/horizon/issues/527), closed) found that Java mods can't simply run, because they call Minecraft's own classes. Option to look at again: a bridge for simple Fabric mods.
+
+</details>
+
+#### CurseForge in the mod browser (coming soon)
+
+Coming soon: search and download CurseForge mods and modpacks from the launcher, as you can with Modrinth today.
+
+<details><summary>Technical</summary>
+
+The mod browser lists CurseForge as coming soon ([docs/mod-browser.md](docs/mod-browser.md)): it needs CurseForge API access. Meanwhile packs import from a CurseForge zip or instance folder, and jars only CurseForge hosts come from the player's own instance ([docs/modpacks.md](docs/modpacks.md)).
+
+</details>
+
+#### A Convert to Rust button for what isn't rewritten yet
+
+When a mod, shader pack or modpack hasn't been rewritten for Horizon, one button converts what can be converted, so you don't have to wait for the rewrite.
+
+<details><summary>Technical</summary>
+
+Generalise the mod browser's Port step (`horizon-port-pack`: the data, assets, worldgen and block and item definitions of Java mods, .mrpack and CurseForge zips) to every kind of content: code mods as native mods (see 'Mods with code') and shader packs, converting an Iris/OptiFine pack into Horizon's format. The browser says what works before the install. Java code itself does not run ([docs/modpacks.md](docs/modpacks.md), [docs/mod-browser.md](docs/mod-browser.md)).
+
+</details>
+
+#### Mods with code: machines, magic, mobs
+
+Making mods that add machines, magic and mobs work in Horizon, in steps, starting with machines. They are most of what a big modpack is made of.
+
+<details><summary>Technical</summary>
+
+333 of the 496 mods in a big pack (ATM10) contain code. Issue [#1854](https://github.com/horizon-rust/horizon/issues/1854) ranks the gaps (ticking block entities, networking, rendering, menus, inventories) that unlock them in tiers, with machines first as the recommended path. Code mods are native mods now ([docs/native-mods.md](docs/native-mods.md)): each port is a horizon-mixins bundle. The path isn't started yet ([docs/modpacks.md](docs/modpacks.md)).
+
+</details>
+
+#### Data packs in the mod browser
+
+Search and install data packs from the launcher's mod browser, for the world you choose, as you do mods and resource packs.
+
+<details><summary>Technical</summary>
+
+A Datapacks tab beside Mods and Resource packs: install into a chosen world's datapacks folder, with the same checks and 'works in Horizon' notes as the other kinds ([docs/mod-browser.md](docs/mod-browser.md)).
+
+</details>
+
+### Servers and multiplayer
+
+#### Ely.by and other sign-in providers
+
+Sign in with other account providers, such as Ely.by or any Yggdrasil-compatible one, beside Microsoft.
+
+<details><summary>Technical</summary>
+
+Issue [#1270](https://github.com/horizon-rust/horizon/issues/1270) asks for Ely.by and Yggdrasil-compatible servers with an account selector in the launcher. It builds on the Microsoft sign-in ([docs/microsoft-account.md](docs/microsoft-account.md)).
+
+</details>
+
+#### Join servers on older versions
+
+Join servers that run older Minecraft versions, such as 1.21 or 1.8 PvP servers, from Horizon.
+
+<details><summary>Technical</summary>
+
+Asked often in the suggestion queue. Horizon speaks 26.3's protocol; the path is a native protocol adapter in Rust that translates older versions' packets, not a downloaded Java proxy. Java instances in the launcher already play any version with the real game.
+
+More: [#3023](https://github.com/horizon-rust/horizon/issues/3023)
+
+</details>
+
+#### Online-mode checks for Play with Friends
+
+Friends who join through an invite code could prove who they are with their Microsoft account, as on online-mode servers.
+
+<details><summary>Technical</summary>
+
+Play with Friends joins over an encrypted tunnel with an invite code ([docs/play-with-friends.md](docs/play-with-friends.md), 'Identity'). Online-mode checks against Mojang's session servers can be added on top of the same tunnel; they need Microsoft sign-in first, which is coming soon. Play with Friends stays self-hosted between players, with no relay run by the project.
+
+</details>
+
+#### Prepare a version without Java
+
+Set up Horizon, a server first, without Java on your computer: published tables are combined with your own copy of the game.
+
+<details><summary>Technical</summary>
+
+Today `horizon-prepare` runs Mojang's exporters with Java. Issue [#1750](https://github.com/horizon-rust/horizon/issues/1750) proposes publishing the computed version tables once from CI and assembling the rest locally from the player's own jar and assets, provided the tables hold no Mojang content; a contributor offered a pull request, and it would help phones too. A server-only prepare from `server.jar` alone is the first step ([docs/server.md](docs/server.md)).
+
+</details>
+
+#### Guided hosting with Tailscale and an invite button
+
+In the launcher, a guide and a button to host a server and invite friends over Tailscale, so nobody has to open ports on a router.
+
+<details><summary>Technical</summary>
+
+On the Servers page (create, start, back up, update and invite are shipped) add a Tailscale setup that explains and checks each step, and an invite button that hands friends what they need to join over the tailnet. Buttons first, no docs needed, with the details in an Advanced section. Remote access over Tailscale is already described in [docs/server.md](docs/server.md).
+
+More: [docs/hosting.md](docs/hosting.md)
+
+</details>
+
+#### An official Docker image for servers
+
+An official image to run a Horizon dedicated server in Docker with one command, your own copy of the game files mounted in.
+
+<details><summary>Technical</summary>
+
+The repository has the Dockerfile (`packaging/server/Dockerfile`: a multi-stage build on Debian bookworm-slim, user `horizon`, volume `/data`, port 25565, game files mounted read-only, `HORIZON_EULA` and friends answering the first-start questions), and anyone can build it ([docs/hosting.md](docs/hosting.md), section 9). Left: publish the image to a public registry from the release workflow, tagged per release, so it follows the same checks, and update the docs and the launcher. The image never holds Mojang's files.
+
+More: [docs/server.md](docs/server.md)
+
+</details>
+
+#### A server you install with one command
+
+Install and run a Horizon dedicated server from a terminal with a single command, no launcher needed, for VPSes and headless machines.
+
+<details><summary>Technical</summary>
+
+A player's idea (#horizon-ideas). `horizon-server` already runs headless; left: an install script (Linux/macOS shell, Windows PowerShell) that fetches the signed release, checks it, asks for or points at the player's own game files and starts the server, documented in [docs/hosting.md](docs/hosting.md).
+
+</details>
+
+#### Ready-made setups for hosting panels
+
+Install a Horizon server from the panels hosts use, such as Pterodactyl and AMP, the usual way for each panel.
+
+<details><summary>Technical</summary>
+
+Asked in the suggestion queue for Pterodactyl eggs and AMP templates. Builds on the one-command install ('A server you install with one command') and horizon-server's server.toml ([docs/hosting.md](docs/hosting.md)).
+
+</details>
+
+### Mods and API
+
+#### Scripts for mods
+
+Small mods written as scripts, in the style of KubeJS, with no compiler.
+
+<details><summary>Technical</summary>
+
+Waits for native mods to settle: a script layer over the native hook points is to be designed.
+
+More: [docs/native-mods.md](docs/native-mods.md)
+
+</details>
+
+#### Orbital Laser on the normal game
+
+The community mod Orbital Laser, made for a fork of Horizon, running on the normal game as a native mod and listed in the registry.
+
+<details><summary>Technical</summary>
+
+A native port (a horizon-mixins bundle, docs/native-mods.md) of [https://github.com/Stink-O/orbital-laser](https://github.com/Stink-O/orbital-laser) (MIT), which today runs through its author's fork. Tested in the game, and listed in the registry.
+
+</details>
+
+#### Native versions of popular client mods
+
+Built-in versions of the client mods players ask for: block info on hover, a world map, inventory tweaks and schematic overlays.
+
+<details><summary>Technical</summary>
+
+Done: a mod list and menu, minimap, zoom, keystrokes, an FPS counter and a recipe viewer, as native mods (horizon-mods/native/). Asked for: an angled world map that shows hills, overhangs and caves, inventory tweaks (drag and scroll to move items), block info tooltips and schematic overlays.
+
+More: [docs/extras.md](docs/extras.md) · [docs/native-mods.md](docs/native-mods.md)
+
+</details>
+
+#### Create-style physics as a native mod
+
+Contraptions and physics like the Create and Aeronautics mods, as a mod for Horizon rather than part of the base game.
+
+<details><summary>Technical</summary>
+
+Issue [#805](https://github.com/horizon-rust/horizon/issues/805) (porting QOL mods) closed with this answer: it would come as a native Horizon mod.
+
+</details>
+
+#### Proximity voice chat as a native mod
+
+Hear nearby players talk, as with the voice chat mods of other Minecraft versions, as a Horizon mod.
+
+<details><summary>Technical</summary>
+
+A native mod ([docs/native-mods.md](docs/native-mods.md)). It needs a way to carry voice between players and an audio path in the game before anything can be built.
+
+</details>
+
+### Gameplay parity
+
+#### Every Minecraft version, prepared automatically
+
+Every past and future Minecraft version prepared for Horizon automatically. When Mojang releases one, Horizon follows it, and every system is checked against it again.
+
+<details><summary>Technical</summary>
+
+The port pipeline ([docs/version-ports.md](docs/version-ports.md), `tools/version_port.py`) detects a release, prepares it, diffs its classes against the pinned 26.3, regenerates the data-driven tables, runs every parity harness on it and writes a port report that becomes issues. The goal is as little human work as possible for any version, past or future. Detection and the first slices are merged; the scheduled agent that runs it every day isn't installed yet. Two versions in one build are out of scope.
+
+</details>
+
+#### Controllers: tested on real pads, and in the launcher
+
+Make controller support solid: tested with real PlayStation and Xbox pads and a Steam Deck, and usable in the launcher too.
+
+<details><summary>Technical</summary>
+
+The game side is merged ([docs/controllers.md](docs/controllers.md)): pads read with gilrs, menus, rumble, glyphs, remapping and DualSense adaptive triggers, lightbar and haptics, but not yet confirmed on real pads or a Steam Deck (DualSense haptics stay behind a switch until then). Left: a test pass on real hardware, and the same focus navigation in the GPUI launcher.
+
+</details>
+
+#### The full debug screen
+
+Vanilla's complete F3 screen: debug options, a profiler chart, ten-second captures and an atlas dump.
+
+<details><summary>Technical</summary>
+
+Today F3 shows position, chunk, light, biome and FPS ([docs/native-client.md](docs/native-client.md)). Vanilla also has F3+F6 debug options with profiles, F3+1 the profiler pie, F3+L a ten-second capture and F3+S the atlas dump ([#562](https://github.com/horizon-rust/horizon/issues/562) asked for the F3 editor).
+
+</details>
+
+#### Pistons push players and mobs
+
+Pistons and slime blocks will push players, mobs and items as in vanilla. Today moving blocks pass through them.
+
+<details><summary>Technical</summary>
+
+Port `PistonMovingBlockEntity.moveCollidedEntities` and `moveStuckEntities` (honey), the slime bounce and `Entity.limitPistonMovement` for `MoverType.PISTON`, in single player and for a server's players. Issues [#1496](https://github.com/horizon-rust/horizon/issues/1496), [#1609](https://github.com/horizon-rust/horizon/issues/1609), [#1608](https://github.com/horizon-rust/horizon/issues/1608), [#1704](https://github.com/horizon-rust/horizon/issues/1704), [#1758](https://github.com/horizon-rust/horizon/issues/1758).
+
+</details>
+
+#### Villages and combat, exactly as in vanilla
+
+Villages and fights behaving as in vanilla: iron golems defending villages, villagers remembering their homes, mace smashes and knockback.
+
+<details><summary>Technical</summary>
+
+Villages: iron golem village goals, villager memories across saves, villager age, job-site claiming on dedicated servers, flower offers ([#1639](https://github.com/horizon-rust/horizon/issues/1639) is one report). Combat: the mobs' `attack_knockback` attribute, mace smash logic, the hit knockback source on the host, the fire burnout biome tag. Each is checked against vanilla by a harness ([docs/rust-parity.md](docs/rust-parity.md)).
+
+</details>
+
+#### Choose the audio output device
+
+Pick the speakers or headphones Horizon plays through, in Music & Sounds.
+
+<details><summary>Technical</summary>
+
+An output device list in Music & Sounds, falling back to the system default. [#1035](https://github.com/horizon-rust/horizon/issues/1035) started it: a player on an older Windows computer had no sound at all, and a device choice is how such cases are found and fixed.
+
+</details>
+
+#### Play in your language
+
+Item names, container titles and server messages follow the language you pick, as in vanilla. Today parts of the game stay in English.
+
+<details><summary>Technical</summary>
+
+Translatable components resolved through the selected language for items, containers and server text ([#1806](https://github.com/horizon-rust/horizon/issues/1806)), on top of the bundled languages the prepared resources carry ([#1594](https://github.com/horizon-rust/horizon/issues/1594)). Left: the client's own screens ([#1672](https://github.com/horizon-rust/horizon/issues/1672)) and the main menu with zh_cn.
+
+</details>
+
+### Rendering
+
+#### A light default shader pack
+
+A small built-in look (tone mapping, colour grade, a cheap vignette) that costs almost nothing, for players who want a nicer picture without a heavy pack.
+
+<details><summary>Technical</summary>
+
+An opt-in, composite-only pack on the native shader API, under about 0.3 ms at 1080p, shown on the Shader Packs page. Pack option sliders and profiles, and a Failed row with the full error, belong with it.
+
+More: [docs/shaders.md](docs/shaders.md)
+
+</details>
+
+#### Optional ray tracing
+
+An optional ray-tracing mode for graphics cards that support it (RTX and recent AMD): shadows, water reflections and global lighting on top of the vanilla look.
+
+<details><summary>Technical</summary>
+
+A spike with ray-traced sun shadows, off by default, is a draft ([#1180](https://github.com/horizon-rust/horizon/issues/1180)). Reflections, global illumination, Apple M3 and newer if it is cheap, and a performance report per card come after.
+
+</details>
+
+#### HDR monitors
+
+Output for HDR monitors: brighter highlights and richer colour where your screen supports it.
+
+<details><summary>Technical</summary>
+
+Issue [#1441](https://github.com/horizon-rust/horizon/issues/1441). Needs a surface format and a tone-mapping path per backend, and tests on real HDR screens on Windows, macOS and Linux.
+
+</details>
+
+#### MSAA, anisotropic filtering, exclusive fullscreen
+
+More graphics options: multisample anti-aliasing, anisotropic filtering and an exclusive fullscreen mode. Today Horizon has FXAA and borderless fullscreen.
+
+<details><summary>Technical</summary>
+
+Not implemented ([docs/graphics.md](docs/graphics.md)). Anisotropic filtering needs linear magnification in wgpu, which blurs close blocks, so close-up sharpness has to be kept first; MSAA would sit beside FXAA, and SMAA or TAA are asked for too; exclusive fullscreen where the backend supports it.
+
+</details>
+
+#### Well-known shader looks, rewritten for Horizon
+
+Popular shader packs rewritten in Horizon's format, so good packs exist from the start. Only packs whose licence is open source and compatible with ours are rewritten, never anything else.
+
+<details><summary>Technical</summary>
+
+The first candidates are Photon, Chocapic13 and MakeUp Ultra Fast, each only after its licence is read and recorded: a pack is rewritten only if it is open source and compatible with Horizon's licence, and the rewrite is written from the shader format's documentation and the look on screen, not from anyone's code. Today only the Golden Hour example exists (`[crates/horizon-shader-api/packs/golden_hour](crates/horizon-shader-api/packs/golden_hour)`).
+
+More: [docs/shaders.md](docs/shaders.md)
+
+</details>
+
+### Launcher
+
+#### Lean installs that use less disk
+
+Smaller installs: Horizon keeps one shared copy of the prepared game files and removes what only the preparation needed.
+
+<details><summary>Technical</summary>
+
+A shared resource store keyed by the preparer's digest, no prepare intermediates left behind, the current and the previous version kept, and an automatic clean-up. Not started.
+
+</details>
+
+#### A visible beta label
+
+A clear 'beta' label in the launcher and the game, so nobody is surprised that Horizon is still being built.
+
+<details><summary>Technical</summary>
+
+Show Beta in the launcher's header and about page, on the game's title screen and on the website, beside the version number ([docs/versioning.md](docs/versioning.md)).
+
+</details>
+
+### Platforms
+
+#### Horizon on Linux ARM64
+
+Game and launcher builds for 64-bit ARM Linux computers.
+
+<details><summary>Technical</summary>
+
+Issue [#1709](https://github.com/horizon-rust/horizon/issues/1709): aarch64 builds of the game and the launcher in the release workflow, tested on a real ARM machine with its Vulkan driver. The server build already drops audio and controllers (`--no-default-features`).
+
+</details>
+
+#### Horizon on Windows ARM64
+
+A native Horizon for Windows on ARM computers, such as Snapdragon laptops.
+
+<details><summary>Technical</summary>
+
+Releases are x64 for Windows and Linux and arm64 for macOS. Needs an aarch64-pc-windows-msvc build in the release workflow and a machine to test on.
+
+More: [docs/release-flow.md](docs/release-flow.md)
+
+</details>
+
+#### Android, iOS and the browser
+
+Versions of Horizon for Android, iOS and web browsers. Nothing official yet; contributors have started the first pieces.
+
+<details><summary>Technical</summary>
+
+No official build. Android was first closed as not planned, with touch controls, a mobile interface, packaging and loading the player's own assets all missing; the roadmap now includes it, iOS and a build for the browser as long-term goals. First pieces from contributors: `horizon-dualsense` compiling on iOS ([#1813](https://github.com/horizon-rust/horizon/issues/1813)) and helper-thread limits on Android ([#1751](https://github.com/horizon-rust/horizon/issues/1751)). Preparing without Java ([#1750](https://github.com/horizon-rust/horizon/issues/1750)) matters here too. Horizon ships none of Mojang's files on any platform.
+
+</details>
+
+#### Horizon on Intel Macs
+
+Builds of the game and the launcher for Macs with an Intel processor.
+
+<details><summary>Technical</summary>
+
+x86_64 game and launcher builds, picked per processor ([#1171](https://github.com/horizon-rust/horizon/issues/1171)). Before it ships it needs a run on a real Intel Mac: Rosetta on Apple Silicon only proves the CPU code. Requests: [#1161](https://github.com/horizon-rust/horizon/issues/1161), [#1792](https://github.com/horizon-rust/horizon/issues/1792).
+
+</details>
+
+#### Wayland and Hyprland polish
+
+Fixes for Linux desktops that use Wayland and Hyprland: fullscreen, the clipboard, the GUI scale after a restart and the like.
+
+<details><summary>Technical</summary>
+
+Open: the GUI Scale is clamped to 2 after a restart under Hyprland, while XWayland keeps it ([#1866](https://github.com/horizon-rust/horizon/issues/1866)). Earlier reports covered fullscreen dropping on menu clicks, the clipboard and a white overlay ([#1007](https://github.com/horizon-rust/horizon/issues/1007), closed). Checked on a real Wayland session.
+
+</details>
+
+#### AppImage and a Nix flake
+
+Install Horizon on any Linux distribution as an AppImage, and on NixOS through a Nix flake.
+
+<details><summary>Technical</summary>
+
+A player's idea (#horizon-ideas). An AppImage of the launcher and game from the release workflow, and a flake.nix packaging the release binaries with their runtime libraries (Vulkan loader, X11/Wayland, ALSA), the way horizon-parity's NixOS setup runs them today.
+
+</details>
+
+### Horizon extras
+
+#### A complete video studio inside the game
+
+Record, replay and edit videos without leaving the game: record in a keypress, replay a session, cut and finish the video. One of Horizon's original goals.
+
+<details><summary>Technical</summary>
+
+Three stages. Recording: capture gameplay in a keypress with an encoder thread and little frame-time cost. Replay: a replay mode for recorded sessions. Editing: cuts, camera paths, titles and export. None of it exists yet; the agent-control socket ([docs/agent-control.md](docs/agent-control.md)) already lets tools drive the game for scripted shots.
+
+</details>
+
+#### Game menus in the launcher's style
+
+An optional look for the game's own menus and options that matches the Horizon launcher. Off by default: the vanilla menus stay as they are.
+
+<details><summary>Technical</summary>
+
+A player's idea (#horizon-ideas). A built-in resource pack or a Horizon setting that restyles the title, pause and options screens with the launcher's design tokens (crates/horizon-theme), following [docs/design-system.md](docs/design-system.md); off by default because it changes the vanilla look.
+
+</details>
+
+### AI and agents
+
+#### An optional AI teammate
+
+An optional AI teammate you can talk to by voice. It plays beside you, helps or finishes the game with you, runs on your computer first, and exists only if you turn it on. The No AI switch hides it.
+
+<details><summary>Technical</summary>
+
+Draft pull requests: the companion ([#1068](https://github.com/horizon-rust/horizon/issues/1068)), its safety modes and their evaluation ([#1069](https://github.com/horizon-rust/horizon/issues/1069)) and a route that finishes the game ([#1070](https://github.com/horizon-rust/horizon/issues/1070)). In the drafts: a companion that follows, fights, mines, crafts, sleeps and respawns; chat and push-to-talk voice, with speech recognition and a choice of voices; presets (very strong, helper, beat the game); a guard model with Clean, Kid and Salty modes; perception levels from Fair to All-knowing; hardware detection with a simple mode and an Advanced tab; local models first, cloud keys optional. The No AI switch is already in the game. Left: the speedrun route doesn't finish the game reliably yet, voices for more languages, and the safety evaluation, which must pass before it ships.
+
+</details>
+
+#### A versioned agent-control protocol
+
+A stable, documented way for AI agents and scripts to drive the game and the launcher, with versions and an event stream so tools keep working as Horizon changes.
+
+<details><summary>Technical</summary>
+
+`hello` answers with the API version, the release and the features; `horizon-ctl --api`; MCP serverInfo; reply schemas generated into the reference; a `test.` namespace for hooks; transcript compatibility tests; `subscribe` as a stream of events on one connection; Horizon option files by key and saved-server commands. Agent control itself (`horizon-ctl`, both MCP servers, the No AI switch) is done: [docs/agent-control.md](docs/agent-control.md), [docs/api/agent-control.md](docs/api/agent-control.md).
+
+More: [docs/api/stability.md](docs/api/stability.md)
+
+</details>
+
+#### Port mods with your own AI agent
+
+You can port a mod to Horizon with your own AI agent on your own computer. Horizon documents how and gives you the tools, but provides no hosted agents.
+
+<details><summary>Technical</summary>
+
+A player runs their own agent locally with `horizon-ctl` and the MCP servers ([docs/agent-control.md](docs/agent-control.md)), `cargo horizon-mod`, `horizon-port-pack` and the parity harnesses as the check. Horizon writes the guide (playhorizon.dev/docs/agents, [docs/modpacks.md](docs/modpacks.md)) and runs no agents, accounts or keys for players. The No AI switch turns all of it off.
+
+More: [https://playhorizon.dev/docs/agents](https://playhorizon.dev/docs/agents)
+
+</details>
+
+### Community
+
+#### A video series about Horizon
+
+A series of videos about how Horizon is made and what is new, with each upload announced on Discord.
+
+<details><summary>Technical</summary>
+
+Kira already shows new uploads in a read-only Discord channel (done). The series follows each stage of the project: a script, edits, titles and a thumbnail per video.
+
+</details>
+
+#### Horizon on X (coming soon)
+
+Coming soon: an official Horizon account on X, used to announce releases and the weekly summary.
+
+<details><summary>Technical</summary>
+
+Kira already posts the roadmap items marked `announce = true` when they ship, and the weekly summary, as soon as the account's credentials exist ([roadmap/README.md](roadmap/README.md), 'The journal'). Waiting for the account itself.
+
+</details>
+
+### Code and tools
+
+#### Pipeline protection and a GitHub App for agents
+
+Safer releases: changes to the release machinery need the owner's review, and AI agents use a smaller identity of their own instead of a personal account.
+
+<details><summary>Technical</summary>
+
+`.github/CODEOWNERS` lists the workflows, the release and signing tools, the update-checking code and the installers ([#1015](https://github.com/horizon-rust/horizon/issues/1015)); the branch protection that makes it count waits for the `horizon-agent` GitHub App, which reads and writes code, pull requests and issues but can't change settings, workflows, secrets or members, and whose tokens last an hour. It needs the owner to create the App and switch the protection on ([docs/security.md](docs/security.md)).
+
+</details>
+
+#### Signed updates everywhere, installers included
+
+Every download Horizon makes is checked against the project's signature, including the first install with install.sh and install.ps1.
+
+<details><summary>Technical</summary>
+
+Releases carry signed checksums, and the launcher and `horizon-server update` refuse anything unsigned ([#1011](https://github.com/horizon-rust/horizon/issues/1011), [#1014](https://github.com/horizon-rust/horizon/issues/1014)). Left: the first install through `install.sh` and `install.ps1` still trusts only the checksum GitHub publishes, because verifying Ed25519 signatures needs OpenSSL 3, which macOS doesn't ship ([docs/security.md](docs/security.md)).
+
+</details>
+
+## Help wanted
+
+### Performance
+
+#### Benchmark your computer
+
+Run Horizon's built-in benchmark and share the report: every new computer makes the performance work more accurate. No coding needed.
+
+<details><summary>Technical</summary>
+
+`horizon-launcher play --arg=--benchmark --arg=standard` writes a JSON report; `horizon-launcher data benchmark <report>` shows what would be sent and uploads it (playhorizon.dev/docs/performance). Results from three installs with the same hardware appear on the Benchmarks page. Example: [#1711](https://github.com/horizon-rust/horizon/issues/1711).
+
+More: [https://playhorizon.dev/docs/performance](https://playhorizon.dev/docs/performance)
+
+</details>
+
+### Gameplay parity
+
+#### End city banners keep their pattern
+
+Banners in End cities show as plain magenta instead of with their pattern.
+
+<details><summary>Technical</summary>
+
+Compare the banner block entities the End city templates place with vanilla's (`EndCityPieces`, the templates' block entity NBT, `BannerBlockEntity`'s patterns), in `crates/horizon-world/src/worldgen/structure/`. Issue [#1438](https://github.com/horizon-rust/horizon/issues/1438); possibly related: [#526](https://github.com/horizon-rust/horizon/issues/526).
+
+</details>
+
+#### Enchanted loot in End cities
+
+Armour and tools in End city chests should come enchanted, as in vanilla.
+
+<details><summary>Technical</summary>
+
+`loot.rs` implements `enchant_with_levels`: find why the End city chest table's rolls come out bare, and compare them with vanilla's for a few seeds. Issues [#1437](https://github.com/horizon-rust/horizon/issues/1437), [#1660](https://github.com/horizon-rust/horizon/issues/1660).
+
+</details>
+
+## Recently shipped
+
+- **Chickens flap while they fall** (v0.2.67): Chickens should flap their wings while they fall, not stand still in the air. [#1706](https://github.com/horizon-rust/horizon/issues/1706) · [#1892](https://github.com/horizon-rust/horizon/issues/1892)
+- **Ctrl+Backspace and scroll bars in menus** (v0.2.67): Ctrl+Backspace should delete a whole word in the creative search, and every list's scroll bar should be draggable. [#1764](https://github.com/horizon-rust/horizon/issues/1764) · [#1782](https://github.com/horizon-rust/horizon/issues/1782) · [#1884](https://github.com/horizon-rust/horizon/issues/1884) · [#1931](https://github.com/horizon-rust/horizon/issues/1931)
+- **A pointing hand over buttons** (v0.2.67): The mouse pointer should turn into a pointing hand over menu buttons, as in vanilla 26.3. [#1347](https://github.com/horizon-rust/horizon/issues/1347) · [#1897](https://github.com/horizon-rust/horizon/issues/1897)
+- **Chat settings and team prefixes** (v0.2.67): The Hidden and Commands Only chat settings should hide chat, and team prefixes should appear before names in chat. [#1376](https://github.com/horizon-rust/horizon/issues/1376) · [#1378](https://github.com/horizon-rust/horizon/issues/1378) · [#1932](https://github.com/horizon-rust/horizon/issues/1932) · [#1841](https://github.com/horizon-rust/horizon/issues/1841)
+- **Cooldowns drawn on items** (v0.2.67): After you throw an ender pearl, its slot should show the cooldown sweeping away, as in vanilla. [#1763](https://github.com/horizon-rust/horizon/issues/1763) · [#1933](https://github.com/horizon-rust/horizon/issues/1933)
+- **Pre-generate an area with /pregen** (v0.2.67): A /pregen command that builds an area of the world ahead of time, so players don't wait for new terrain when they explore. [#1805](https://github.com/horizon-rust/horizon/issues/1805)
+- **Horizon's own shader format and kit** (v0.2.70): Horizon's own way to make shader packs, with tools to write and test them. Every pack is checked before it runs, and the registry will list them. [#1820](https://github.com/horizon-rust/horizon/issues/1820) · [#1822](https://github.com/horizon-rust/horizon/issues/1822) · [#1861](https://github.com/horizon-rust/horizon/issues/1861) · [#1863](https://github.com/horizon-rust/horizon/issues/1863) · [#1855](https://github.com/horizon-rust/horizon/issues/1855) · [docs/shaders.md](docs/shaders.md) · [docs/api/shaders.md](docs/api/shaders.md)
+- **Discord Rich Presence** (v0.2.58): Your Discord profile can show that you are playing Horizon, with a switch to turn it off. [#1787](https://github.com/horizon-rust/horizon/issues/1787) · [#1788](https://github.com/horizon-rust/horizon/issues/1788)
+- **Server dialogs and login screens** (v0.2.67): Servers that show dialogs, such as the register and login screens of AuthMe, will work in Horizon. [#1720](https://github.com/horizon-rust/horizon/issues/1720) · [#1734](https://github.com/horizon-rust/horizon/issues/1734) · [#1735](https://github.com/horizon-rust/horizon/issues/1735)
+- **Microsoft sign-in** (launcher@0.2.17): Sign in with your Microsoft account in the launcher to play on online-mode servers. [docs/microsoft-account.md](docs/microsoft-account.md) · [#2879](https://github.com/horizon-rust/horizon/issues/2879)
+- **OpenGL for old computers** (v0.2.63): Horizon now starts on old PCs whose graphics card has no Vulkan or DirectX 12 driver: it switches to OpenGL by itself, and Options > Graphics can pick OpenGL by hand. [#1917](https://github.com/horizon-rust/horizon/issues/1917) · [#1920](https://github.com/horizon-rust/horizon/issues/1920) · [#1936](https://github.com/horizon-rust/horizon/issues/1936)
+- **Server resource packs** (v0.2.48): Servers can send you their resource pack: Horizon asks, downloads it and applies it, like vanilla. [#1562](https://github.com/horizon-rust/horizon/issues/1562) · [#1569](https://github.com/horizon-rust/horizon/issues/1569) · [#1570](https://github.com/horizon-rust/horizon/issues/1570)
+- **Single player on its own server thread** (v0.2.39): Single player runs on a server thread, as vanilla does, so the world keeps ticking smoothly while the window draws. [#1514](https://github.com/horizon-rust/horizon/issues/1514) · [docs/server-levels.md](docs/server-levels.md)
+- **GPU occlusion culling on Macs** (v0.2.17): On Macs the GPU now skips terrain hidden behind hills and caves: 8 to 48% more frames per second at 32 chunks on an M4 Pro. [#1434](https://github.com/horizon-rust/horizon/issues/1434)
+- **Animated textures on the GPU** (v0.2.5): Water, lava and other animated blocks are now animated by the graphics card: 1.7 to 2.4 times better 1% lows on Intel graphics. [#1239](https://github.com/horizon-rust/horizon/issues/1239)
+- **Far Detail for integrated graphics** (v0.2.5): An optional Reduced setting for far terrain, suggested on integrated graphics, that saves 2 to 4 ms of GPU time per frame. [#1199](https://github.com/horizon-rust/horizon/issues/1199) · [#1029](https://github.com/horizon-rust/horizon/issues/1029)
+- **The launcher's mod browser** (launcher@0.2.0): Search Modrinth for mods, modpacks and resource packs from the launcher; it says before installing what works in Horizon. [#1154](https://github.com/horizon-rust/horizon/issues/1154) · [#1242](https://github.com/horizon-rust/horizon/issues/1242) · [#1243](https://github.com/horizon-rust/horizon/issues/1243) · [#1246](https://github.com/horizon-rust/horizon/issues/1246) · [docs/mod-browser.md](docs/mod-browser.md)
+- **A blocky, Minecraft-like launcher** (launcher@0.2.0): The launcher got a new blocky look in Horizon's purple, in dark and light. [#1269](https://github.com/horizon-rust/horizon/issues/1269) · [docs/design-system.md](docs/design-system.md)
+- **Dynamic lights** (v2026.10.22): An optional extra: torches you hold, drop or set on fire light up what is around them. [#1162](https://github.com/horizon-rust/horizon/issues/1162)
+- **Host a server from the launcher** (launcher-v0.15.0): The launcher's Servers page creates, starts, backs up and updates a Horizon server with buttons, and invites friends. [#1026](https://github.com/horizon-rust/horizon/issues/1026) · [docs/hosting.md](docs/hosting.md)

THIRD_PARTY_NOTICES.md

@@ -17,4 +17,16 @@ by The Pixelify Sans Project Authors, licensed under the SIL Open Font License 1
 
 `crates/horizon-theme/icons/pixel/*.svg` are icons from
 [Pixelarticons](https://github.com/halfmage/pixelarticons) by Gerrit Halfmann, under the MIT
-license (`crates/horizon-theme/icons/pixel/LICENSE-pixelarticons.txt`).
+license (`crates/horizon-theme/icons/pixel/LICENSE-pixelarticons.txt`). `star.svg` is Horizon's own, drawn on
+the same grid.
+
+## AMD FidelityFX SDK (FSR 3.1 frame generation)
+
+`crates/horizon-client-render/src/gfx/frame_gen/optical_flow.wgsl` is a port to WGSL of the
+optical flow shaders of the [AMD FidelityFX SDK](https://github.com/GPUOpen-LibrariesAndSDKs/FidelityFX-SDK)
+1.1.4 (`sdk/include/FidelityFX/gpu/opticalflow`, at commit
+[c6efa6bf7f20](https://github.com/GPUOpen-LibrariesAndSDKs/FidelityFX-SDK/tree/c6efa6bf7f2027b3ec94f28578bb5965eabb9e55)),
+and `optical_flow.rs` follows the SDK's `sdk/src/components/opticalflow/ffx_opticalflow.cpp`
+(its passes, their order and their dispatch sizes). Copyright (C) 2024 Advanced Micro Devices,
+Inc., under the MIT license, whose text heads both files. AMD and FidelityFX are AMD's
+trademarks; Horizon is not affiliated with AMD.

benchmarks/perf/horizon-win-9800x3d-5080-rd16.json

@@ -0,0 +1,773 @@
+{
+ "format": "horizon-benchmark-report",
+ "version": 1,
+ "kind": "game",
+ "created": "2026-10-29T01:13:01Z",
+ "app": {
+  "name": "horizon-client",
+  "version": "v0.2.97",
+  "commit": null
+ },
+ "hardware": {
+  "os": "windows",
+  "arch": "x86_64",
+  "cpu_threads": 16,
+  "os_version": "Microsoft Windows [Version 10.0.26200.8037]",
+  "cpu": "AMD Ryzen 7 9800X3D 8-Core Processor",
+  "ram_mb": 95943,
+  "gpu": {
+   "name": "NVIDIA GeForce RTX 5080",
+   "vendor": "nvidia",
+   "driver": "NVIDIA 617.42",
+   "backend": "vulkan",
+   "kind": "discrete"
+  }
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benchmarks/perf/horizon-win-9800x3d-5080-rd32.json

@@ -0,0 +1,773 @@
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benchmarks/perf/horizon-win-9800x3d-5080-rd8.json

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benchmarks/perf/vanilla-mods-win-9800x3d-5080-rd16.json

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benchmarks/perf/vanilla-mods-win-9800x3d-5080-rd32.json

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benchmarks/perf/vanilla-win-9800x3d-5080-rd8.json

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+    0,
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+    0,
+    0,
+    0,
+    0,
+    0
+   ]
+  },
+  {
+   "phase": "forest",
+   "repeat": 0,
+   "frames": 31855,
+   "seconds": 12.0,
+   "avg_fps": 2654.549,
+   "low_1pct_fps": 667.966,
+   "low_01pct_fps": 257.945,
+   "p50_ms": 0.341,
+   "p95_ms": 0.519,
+   "p99_ms": 0.932,
+   "p999_ms": 1.761,
+   "max_ms": 10.944,
+   "histogram": [
+    31558,
+    275,
+    6,
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+   ]
+  },
+  {
+   "phase": "forest",
+   "repeat": 1,
+   "frames": 31763,
+   "seconds": 12.0,
+   "avg_fps": 2646.916,
+   "low_1pct_fps": 685.008,
+   "low_01pct_fps": 270.233,
+   "p50_ms": 0.344,
+   "p95_ms": 0.52,
+   "p99_ms": 0.94,
+   "p999_ms": 1.685,
+   "max_ms": 11.406,
+   "histogram": [
+    31474,
+    272,
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+  },
+  {
+   "phase": "forest",
+   "repeat": 2,
+   "frames": 24818,
+   "seconds": 12.0,
+   "avg_fps": 2068.162,
+   "low_1pct_fps": 521.303,
+   "low_01pct_fps": 229.228,
+   "p50_ms": 0.439,
+   "p95_ms": 0.767,
+   "p99_ms": 1.284,
+   "p999_ms": 2.351,
+   "max_ms": 11.468,
+   "histogram": [
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+  },
+  {
+   "phase": "ocean",
+   "repeat": 0,
+   "frames": 32039,
+   "seconds": 12.0,
+   "avg_fps": 2669.9,
+   "low_1pct_fps": 741.491,
+   "low_01pct_fps": 294.727,
+   "p50_ms": 0.345,
+   "p95_ms": 0.501,
+   "p99_ms": 0.86,
+   "p999_ms": 1.431,
+   "max_ms": 9.257,
+   "histogram": [
+    31771,
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+    0
+   ]
+  },
+  {
+   "phase": "ocean",
+   "repeat": 1,
+   "frames": 31854,
+   "seconds": 12.0,
+   "avg_fps": 2654.471,
+   "low_1pct_fps": 747.759,
+   "low_01pct_fps": 302.422,
+   "p50_ms": 0.347,
+   "p95_ms": 0.503,
+   "p99_ms": 0.853,
+   "p999_ms": 1.404,
+   "max_ms": 13.925,
+   "histogram": [
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+   ]
+  },
+  {
+   "phase": "ocean",
+   "repeat": 2,
+   "frames": 25022,
+   "seconds": 12.0,
+   "avg_fps": 2085.121,
+   "low_1pct_fps": 576.803,
+   "low_01pct_fps": 262.183,
+   "p50_ms": 0.428,
+   "p95_ms": 0.758,
+   "p99_ms": 1.214,
+   "p999_ms": 2.109,
+   "max_ms": 9.206,
+   "histogram": [
+    24600,
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+   ]
+  },
+  {
+   "phase": "mountain",
+   "repeat": 0,
+   "frames": 33745,
+   "seconds": 12.0,
+   "avg_fps": 2812.075,
+   "low_1pct_fps": 736.0,
+   "low_01pct_fps": 258.279,
+   "p50_ms": 0.327,
+   "p95_ms": 0.471,
+   "p99_ms": 0.808,
+   "p999_ms": 1.689,
+   "max_ms": 10.07,
+   "histogram": [
+    33516,
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+   ]
+  },
+  {
+   "phase": "mountain",
+   "repeat": 1,
+   "frames": 33294,
+   "seconds": 12.0,
+   "avg_fps": 2774.461,
+   "low_1pct_fps": 763.45,
+   "low_01pct_fps": 295.503,
+   "p50_ms": 0.334,
+   "p95_ms": 0.471,
+   "p99_ms": 0.813,
+   "p999_ms": 1.63,
+   "max_ms": 8.512,
+   "histogram": [
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+    3,
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+    0,
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+    0,
+    0,
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+    0
+   ]
+  },
+  {
+   "phase": "mountain",
+   "repeat": 2,
+   "frames": 26747,
+   "seconds": 12.0,
+   "avg_fps": 2228.824,
+   "low_1pct_fps": 599.44,
+   "low_01pct_fps": 239.602,
+   "p50_ms": 0.403,
+   "p95_ms": 0.678,
+   "p99_ms": 1.107,
+   "p999_ms": 2.054,
+   "max_ms": 9.178,
+   "histogram": [
+    26418,
+    298,
+    13,
+    6,
+    2,
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+    0,
+    0,
+    0,
+    0,
+    0,
+    0,
+    0
+   ]
+  }
+ ],
+ "label": "vanilla-win-9800x3d-5080"
+}

benchmarks/perf/windows-9800x3d-5080-2026-10-29.md

@@ -0,0 +1,106 @@
+# Horizon v0.2.97 vs vanilla 26.3 on Windows 11: Ryzen 7 9800X3D + RTX 5080 (2026-10-29, RD 8 and 32 rerun 2026-10-30)
+
+The first `tools/perf_bench.py` run on Windows ([docs/benchmark.md](../../docs/benchmark.md)): Horizon, vanilla 26.3 and
+vanilla with performance mods, render distances 8, 16 and 32, 1280x720, three games each, every game from a fresh
+world. The reports are the `*-win-9800x3d-5080-rd*.json` files next to this page.
+
+```sh
+python tools/perf_bench.py --table horizon-win-9800x3d-5080 vanilla-win-9800x3d-5080 vanilla-mods-win-9800x3d-5080
+```
+
+## Setup
+
+- **Machine:** AMD Ryzen 7 9800X3D (8 cores, 16 threads), 94 GB RAM (DDR5, EXPO off), NVIDIA GeForce RTX 5080
+  (driver 617.42), Windows 11 Pro 26200, Balanced power plan, desktop. One 1920x1080 120 Hz display. The game windows
+  were on the desktop of an unlocked session.
+- **Horizon:** release v0.2.97 as the launcher installs it (`--build %APPDATA%\horizon-launcher\versions\v0.2.97`,
+  `--resources` its `.local\horizon-client\26.3`), Vulkan.
+- **Vanilla:** the 26.3 client jar with Fabric Loader 0.19.5 and the driver mod, Java 25.0.5 (Temurin), `-Xmx2G`
+  with the launcher's G1 flags and the manifest's `-XX:StackShadowPages=32`, OpenGL 3.3.
+- **Vanilla + mods:** the same with Sodium mc26.3-0.9.2, Lithium mc26.3-0.26.2, FerriteCore 9.0.0 and
+  ImmediatelyFast 1.17.1 (`tools/benchmark-deps/mods.lock.json`).
+- **Commands:** `python tools/perf_bench.py --game <game> --label <game>-win-9800x3d-5080 --distances <d>
+  --sizes 1280x720 --repeats 3` (plus `--build` and `--resources` for Horizon), with the games taking turns at
+  each distance.
+- **Memory** is the working set on Windows (what Task Manager shows), sampled from outside the process. Horizon's
+  GPU figure is its own Vulkan allocator total. `nvidia-smi` gives no per-process figure under WDDM, so vanilla has
+  none.
+
+## Load
+
+Windows has no load average, so the reports have no `load_avg_1m`. Every game ran on an otherwise idle machine:
+
+- **RD 8 and RD 32** (rerun on 2026-10-30, after the first pass had builds running alongside): a script started each
+  game only once no `rustc`, `cargo`, `link` (or other compiler) process and no other game (`horizon-client`, `java`,
+  `javaw`, Minecraft) was running, and the machine's CPU load had stayed under 15 % in every 5-second sample for
+  30 seconds. During each game it sampled every 2 seconds the machine's CPU load and the CPU of everything outside the
+  benchmark's own processes. A game during which a compiler or another game ran, or other processes used over 15 % of
+  the machine for 10 seconds, was discarded and run again: two of the 20 games were (vanilla + mods at RD 32, a
+  build started during one, background processes during the other).
+- **RD 16** (2026-10-29): no `rustc`, `cargo` or `link` process at any point, the load logged every 5 seconds.
+
+| Game | RD | Mean / max CPU load (machine, the game included) | Other processes' CPU, mean / max | Compiler processes |
+|---|---|---|---|---|
+| Horizon | 8 | 18 % / 49 % | 6 % / 12 % | 0 |
+| Vanilla | 8 | 28 % / 75 % | 7 % / 20 % | 0 |
+| Vanilla + mods | 8 | 30 % / 81 % | 7 % / 20 % | 0 |
+| Horizon | 16 | 29 % / 80 % | – | 0 |
+| Vanilla | 16 | 41 % / 91 % | – | 0 |
+| Vanilla + mods | 16 | 51 % / 90 % | – | 0 |
+| Horizon | 32 | 36 % / 100 % | 5 % / 15 % | 0 |
+| Vanilla | 32 | 39 % / 73 % | 6 % / 18 % | 0 |
+| Vanilla + mods | 32 | 42 % / 88 % | 6 % / 21 % | 0 |
+
+"Other processes" is the machine's load minus the benchmark's own processes (the game and `perf_bench.py`), in
+2-second samples. Most of it is the system's share of the game's own drawing (the graphics driver and the
+compositor), which no process of the benchmark is charged for; the desktop apps left open (a browser, chat apps)
+briefly reached 5 % at most. RD 16's load was logged from outside every 5 seconds, so it has no such split, and its mean includes the time between
+games. Compared with the first pass, the idle RD 8 runs give Horizon about 10 % higher averages and about 50 % higher
+1% lows, and vanilla up to 10 % higher averages.
+
+## Results
+
+Mean of 3 games ± 95% confidence interval. FPS over the 12-second flight at 16 blocks/s (average / 1% low /
+0.1% low):
+
+| RD | scene | Horizon v0.2.97 | Vanilla 26.3 | Vanilla + mods |
+| --- | --- | --- | --- | --- |
+| 8 | forest | 3495 ±276 / 1295 ±397 / 859 ±298 | 2457 ±836 / 625 ±224 / 252 ±52 | 2425 ±65 / 733 ±30 / 250 ±22 |
+| 8 | mountain | 3376 ±67 / 1384 ±168 / 850 ±256 | 2605 ±811 / 700 ±218 / 264 ±71 | 2538 ±167 / 760 ±34 / 241 ±44 |
+| 8 | ocean | 3346 ±147 / 1358 ±237 / 912 ±235 | 2470 ±828 / 689 ±241 / 286 ±53 | 2432 ±82 / 764 ±37 / 262 ±37 |
+| 8 | village | 2942 ±197 / 1271 ±146 / 839 ±94 | 2217 ±112 / 545 ±37 / 215 ±14 | 2104 ±101 / 577 ±84 / 196 ±47 |
+| 16 | forest | 2424 ±138 / 709 ±165 / 401 ±100 | 1912 ±324 / 402 ±89 / 149 ±25 | 1746 ±32 / 461 ±27 / 179 ±9 |
+| 16 | mountain | 1961 ±99 / 537 ±96 / 297 ±75 | 1653 ±153 / 332 ±27 / 113 ±8 | 1500 ±55 / 408 ±40 / 140 ±10 |
+| 16 | ocean | 2201 ±183 / 554 ±251 / 325 ±326 | 1861 ±289 / 446 ±142 / 165 ±29 | 1815 ±119 / 514 ±142 / 192 ±58 |
+| 16 | village | 1712 ±192 / 593 ±80 / 358 ±69 | 1218 ±65 / 318 ±16 / 127 ±5 | 1282 ±162 / 343 ±25 / 132 ±12 |
+| 32 | forest | 1389 ±70 / 504 ±33 / 330 ±118 | 1203 ±51 / 228 ±13 / 108 ±12 | 929 ±8 / 313 ±41 / 129 ±32 |
+| 32 | mountain | 1086 ±34 / 258 ±78 / 108 ±37 | 815 ±61 / 55 ±13 / 8 ±3 | 645 ±10 / 166 ±12 / 86 ±21 |
+| 32 | ocean | 1189 ±27 / 155 ±9 / 68 ±8 | 1223 ±33 / 236 ±17 / 99 ±21 | 1017 ±14 / 325 ±38 / 117 ±28 |
+| 32 | village | 1164 ±9 / 416 ±39 / 216 ±86 | 882 ±48 / 184 ±12 / 83 ±17 | 926 ±17 / 250 ±5 / 93 ±11 |
+
+Startup, loading and memory (means of 3 games):
+
+| RD | | Horizon v0.2.97 | Vanilla 26.3 | Vanilla + mods |
+| --- | --- | --- | --- | --- |
+| 8 | start to title / in-world | 3.0 s / 6.1 s | 7.7 s / 13.9 s | 11.1 s / 17.6 s |
+| 8 | mean scene load | 1.3 s | 4.0 s | 3.6 s |
+| 8 | working set, steady / peak | 1082 / 1172 MB | 1913 / 2120 MB | 1904 / 2053 MB |
+| 16 | start to title / in-world | 3.2 s / 7.2 s | 7.7 s / 19.9 s | 10.8 s / 23.5 s |
+| 16 | mean scene load | 2.4 s | 9.2 s | 9.0 s |
+| 16 | working set, steady / peak | 1236 / 1459 MB | 2300 / 2540 MB | 2327 / 2496 MB |
+| 32 | start to title / in-world | 2.9 s / 10.5 s | 7.5 s / 35.4 s | 11.0 s / 39.2 s |
+| 32 | mean scene load | 5.7 s | 21.1 s | 19.9 s |
+| 32 | working set, steady / peak | 1730 / 2045 MB | 2799 / 2892 MB | 2895 / 2965 MB |
+
+## What it shows
+
+- At RD 8 and 16, Horizon's average FPS is 18–42 % above vanilla's in every scene. Its 1% lows are 1.2–2.3 times
+  vanilla's and its 0.1% lows 2.0–3.9 times. On this CPU and GPU the performance mods leave vanilla's averages
+  level or slightly lower, and raise its 1% lows by 6–23 %.
+- At RD 32, Horizon's average is 15–33 % above vanilla's over the forest, the mountain and the village, with 1% lows
+  2.2–4.7 times vanilla's. Over the ocean its average is level with vanilla's, but its lows are lower than vanilla's
+  and the modded client's (155 vs 236 and 325 FPS 1% low, 68 vs 99 and 117 FPS 0.1% low), on an idle machine too.
+  That scene is worth a closer look.
+- Horizon reaches the title screen 2.4–2.6 times faster than vanilla (3.4–3.8 times faster than the modded client)
+  and loads a scene's chunks 3–4 times faster. Its steady working set is 38–46 % smaller.
+- Each game uses its own graphics API: Horizon Vulkan, vanilla OpenGL. That difference is part of what's compared.

benchmarks/server-equal-mixed-2026-10-18/README.md

@@ -119,7 +119,7 @@ machines during the runs.
 
 ## Reproduce
 
-    curl -fsSL https://raw.githubusercontent.com/ludovic111/horizon/main/packaging/server/install.sh | sh
+    curl -fsSL https://raw.githubusercontent.com/horizon-rust/horizon/main/packaging/server/install.sh | sh
     horizon-prepare --prepare --server-jar /path/to/server.jar      # your own copy
     cargo build --release -p horizon-bots                            # on the machine that runs the bots
     # in a checkout whose .local/minecraft holds the pinned vanilla jars (tools/lab.py prepare):

benchmarks/server-four-way-2026-10-19/README.md

@@ -148,7 +148,7 @@ early, wrote no report. Its lines come from its output.
 
 ## Reproduce
 
-    curl -fsSL https://raw.githubusercontent.com/ludovic111/horizon/main/packaging/server/install.sh | sh
+    curl -fsSL https://raw.githubusercontent.com/horizon-rust/horizon/main/packaging/server/install.sh | sh
     horizon-prepare --prepare --server-jar /path/to/server.jar      # your own copy
     cargo build --release -p horizon-bots                            # on the machine that runs the bots
     # in a checkout whose .local/minecraft holds the pinned vanilla jars (tools/lab.py prepare):

benchmarks/server-mixed-2026-10-18/README.md

@@ -103,7 +103,7 @@ the Nix store, so the run set `LD_LIBRARY_PATH` to them (see #898).
 
 ## Reproduce
 
-    curl -fsSL https://raw.githubusercontent.com/ludovic111/horizon/main/packaging/server/install.sh | sh
+    curl -fsSL https://raw.githubusercontent.com/horizon-rust/horizon/main/packaging/server/install.sh | sh
     horizon-prepare --prepare --server-jar /path/to/server.jar      # your own copy
     cargo build --release -p horizon-bots                            # on the machine that runs the bots
     # in a checkout whose .local/minecraft holds the pinned vanilla jars (tools/lab.py prepare):

crates/cargo-horizon-mod/Cargo.toml

@@ -4,10 +4,10 @@ version = "0.1.0"
 edition.workspace = true
 license.workspace = true
 rust-version = "1.86"
-description = "cargo horizon-mod new/build/run: make Horizon mods in Rust (docs/mods.md)"
+description = "cargo horizon-mod new/build/run/check: make Horizon content mods (docs/mods.md)"
 
 [dependencies]
-horizon-mods = { path = "../horizon-mods", default-features = false, features = ["pack"] }
+horizon-mods = { path = "../horizon-mods", default-features = false, features = ["index"] }
 serde_json = "1.0.151"
 
 [lints]

crates/cargo-horizon-mod/src/check.rs

@@ -0,0 +1,192 @@
+//! `cargo horizon-mod check <file>`: what the registry checks of a submission,
+//! run anywhere: its kind's own checks (docs/api/mod-index.md), its signature
+//! when given a key, and for a `.hmod` that it is content only.
+use horizon_mods::{
+    Package,
+    index::{self, Facts, Kind},
+};
+use serde_json::{Value, json};
+use std::path::Path;
+
+pub struct Report {
+    pub kind: Kind,
+    pub facts: Facts,
+    pub sha256: String,
+    pub size: u64,
+    pub signed: bool,
+}
+
+impl Report {
+    pub fn json(&self) -> Value {
+        let requires: Vec<Value> = self
+            .facts
+            .requires
+            .iter()
+            .map(|r| json!({"id": r.id, "version": r.version, "sha256": r.sha256}))
+            .collect();
+        json!({
+            "kind": self.kind.name(),
+            "id": self.facts.id,
+            "version": self.facts.version,
+            "api": self.facts.api,
+            "side": self.facts.side,
+            "capabilities": self.facts.capabilities,
+            "api_level": self.facts.api_level,
+            "game": self.facts.game,
+            "requires": requires,
+            "sha256": self.sha256,
+            "size": self.size,
+            "signed": self.signed,
+        })
+    }
+
+    pub fn text(&self) -> String {
+        let f = &self.facts;
+        let mut out = format!(
+            "{} {} ({}",
+            f.id.as_deref().unwrap_or("resource pack"),
+            f.version.as_deref().unwrap_or(""),
+            self.kind.name()
+        );
+        if let Some(side) = f.side {
+            let side = serde_json::to_value(side).unwrap_or_default();
+            out += &format!(", API {}, {}", f.api, side.as_str().unwrap_or("?"));
+        } else if self.kind == Kind::Shader {
+            out += &format!(", shader API {}", f.api);
+        } else if !f.api.is_empty() {
+            out += &format!(", format {}", f.api);
+        }
+        if let Some(game) = &f.game {
+            out += &format!(", for {game}");
+        }
+        let signed = if self.signed {
+            "signature verified"
+        } else {
+            "unsigned"
+        };
+        out += &format!(
+            ")\n  {} bytes, SHA-256 {}, {signed}\n",
+            self.size, self.sha256
+        );
+        if let Some(level) = f.api_level {
+            out += &format!("  needs mod API level {level} or newer\n");
+        }
+        for c in &f.capabilities {
+            out += &format!("  may {}\n", c.describe());
+        }
+        for r in &f.requires {
+            out += &format!("  needs {} {} ({})\n", r.id, r.version, &r.sha256[..12]);
+        }
+        if self.kind == Kind::NativeMod {
+            out += "  native source: unsandboxed; not executed by the registry check. Compile and test against the exact pinned Horizon and Mixins revisions before review.\n";
+        }
+        if self.kind == Kind::Mod {
+            out += "  no code: content only, nothing to run\n";
+        }
+        out
+    }
+}
+
+/// The kind a file's extension says.
+pub fn kind_of(path: &Path) -> Option<Kind> {
+    match path.extension()?.to_str()? {
+        "hmod" => Some(Kind::Mod),
+        "hnmod" => Some(Kind::NativeMod),
+        "hpack" => Some(Kind::Modpack),
+        "zip" => Some(Kind::ResourcePack),
+        "hshader" => Some(Kind::Shader),
+        _ => None,
+    }
+}
+
+/// Checks the file at `path` as `kind`; `key` and `signature` (the
+/// `.minisig` text) check its signature.
+pub fn check(
+    path: &Path,
+    kind: Kind,
+    key: Option<&str>,
+    signature: Option<&str>,
+) -> Result<Report, String> {
+    let size = std::fs::metadata(path)
+        .map_err(|e| format!("{}: {e}", path.display()))?
+        .len();
+    if size > index::MAX_FILE {
+        return Err(format!("over {} MiB", index::MAX_FILE >> 20));
+    }
+    index::open(&kind)?;
+    let facts = index::inspect(&kind, path)?;
+    let signed = match (key, signature) {
+        (Some(key), Some(sig)) => {
+            index::verify_signature(key, sig, path)?;
+            true
+        }
+        (None, None) => false,
+        _ => return Err("--key and --signature go together".into()),
+    };
+    if kind == Kind::Mod {
+        content_only(path)?;
+    }
+    Ok(Report {
+        kind,
+        facts,
+        sha256: index::sha256_file(path)?,
+        size,
+        signed,
+    })
+}
+
+/// A mod is content only: WebAssembly code mods don't run any more, code mods are native
+/// (`.hnmod`, docs/native-mods.md). `inspect` already read its content as the game does.
+fn content_only(path: &Path) -> Result<(), String> {
+    match Package::read(path)?.wasm {
+        Some(_) => Err(
+            "it has WebAssembly code, which Horizon doesn't run any more: make it a native mod (docs/native-mods.md)"
+                .into(),
+        ),
+        None => Ok(()),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn fixture(name: &str) -> std::path::PathBuf {
+        Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("../horizon-mods/tests/index")
+            .join(name)
+    }
+
+    #[test]
+    fn checks_each_kind_its_own_way() {
+        let pack = fixture("cozy-1.0.0.hpack");
+        let report = check(&pack, kind_of(&pack).unwrap(), None, None).unwrap();
+        assert_eq!(report.facts.requires[0].id, "coords_hud");
+        assert!(
+            report
+                .text()
+                .contains("cozy 1.0.0 (modpack, format 1, for 26.3)")
+        );
+        // A mod with WebAssembly code is refused: code mods are native.
+        let hmod = fixture("coords_hud-0.1.0.hmod");
+        let key = std::fs::read_to_string(fixture("test.pub")).unwrap();
+        let sig = std::fs::read_to_string(fixture("coords_hud-0.1.0.hmod.minisig")).unwrap();
+        let key = key.lines().last().unwrap();
+        let e = check(&hmod, Kind::Mod, Some(key), Some(&sig))
+            .err()
+            .unwrap();
+        assert!(e.contains("native mod"), "{e}");
+        let e = check(
+            &hmod,
+            Kind::Mod,
+            Some(key),
+            Some("untrusted comment: x\nRUQ=\n"),
+        )
+        .err()
+        .unwrap();
+        assert!(e.contains("signature"), "{e}");
+        let e = check(&pack, Kind::Shader, None, None).err().unwrap();
+        assert!(e.contains("horizon-shaders.toml"), "{e}");
+        assert!(check(&pack, Kind::Mod, None, None).is_err());
+    }
+}

crates/cargo-horizon-mod/src/main.rs

@@ -1,21 +1,23 @@
-//! `cargo horizon-mod`: make Horizon mods in Rust (`docs/mods.md`).
+//! `cargo horizon-mod`: make Horizon content mods (`docs/modpacks.md`): blocks,
+//! items, data and assets, no code. Code mods are native (docs/native-mods.md).
 //!
-//! - `new <path> [--name "Name"] [--sdk-path <dir>]`: a mod crate from the template.
-//! - `build [--debug]`: the `.hmod` in `target/horizon-mod/`.
+//! - `new <path> [--name "Name"]`: a content mod from the template.
+//! - `build`: the `.hmod` in `target/horizon-mod/`, with the mod's `assets/`
+//!   and `data/`.
 //! - `run [--game <horizon-client>] [-- <game args>]`: build, then play with
-//!   the mod; run `build` again and the game reloads it.
-use horizon_mods::{
-    Manifest, Package,
-    manifest::{MANIFEST, component_imports, componentize},
-};
+//!   the mod.
+//! - `check <file> [--json]`: what the registry checks of a submission
+//!   (`.hmod`, `.hnmod`, `.hpack`, resource pack `.zip`, `.hshader`).
+//! - `registry build|review|check|list`: the registry repository's CI.
+use horizon_mods::{Capability, Content, Manifest, Package, manifest::MANIFEST};
+mod check;
+mod registry;
+
 use std::{
     path::{Path, PathBuf},
-    process::{Command, ExitCode, Stdio},
+    process::{Command, ExitCode},
 };
 
-const TARGET: &str = "wasm32-unknown-unknown";
-const SDK_GIT: &str = "{ git = \"https://github.com/ludovic111/horizon\" }";
-
 fn main() -> ExitCode {
     // Cargo runs `cargo-horizon-mod horizon-mod <args>`.
     let mut args: Vec<String> = std::env::args().skip(1).collect();
@@ -24,11 +26,13 @@ fn main() -> ExitCode {
     }
     let result = match args.first().map(String::as_str) {
         Some("new") => new(&args[1..]),
-        Some("build") => build(!args.iter().any(|a| a == "--debug")).map(|p| {
+        Some("build") => build().map(|p| {
             println!("Built {}", p.display());
         }),
         Some("run") => run(&args[1..]),
-        _ => Err("usage: cargo horizon-mod new <path> | build [--debug] | run [--game <horizon-client>] [-- <game args>]".into()),
+        Some("check") => check(&args[1..]),
+        Some("registry") => registry::main(&args[1..]),
+        _ => Err("usage: cargo horizon-mod new <path> [--name \"Name\"] | build | run [--game <horizon-client>] [-- <game args>] | check <file> [--kind <kind>] [--key <public key> --signature <file.minisig>] [--json] | registry build|review|check|list".into()),
     };
     match result {
         Ok(()) => ExitCode::SUCCESS,
@@ -69,32 +73,63 @@ fn new(args: &[String]) -> Result<(), String> {
         })
         .collect();
     let name = flag(args, "--name").map_or_else(|| base.replace(['-', '_'], " "), str::to_string);
-    let sdk = match flag(args, "--sdk-path") {
-        Some(p) => {
-            let p = std::fs::canonicalize(p).map_err(|e| format!("--sdk-path {p}: {e}"))?;
-            format!("{{ path = {:?} }}", p.display().to_string())
-        }
-        None => SDK_GIT.to_string(),
-    };
-    let fill = |t: &str| {
-        t.replace("{crate}", &id.replace('_', "-"))
-            .replace("{id}", &id)
-            .replace("{name}", &name)
-            .replace("{sdk}", &sdk)
-    };
+    let fill = |t: &str| t.replace("{id}", &id).replace("{name}", &name);
+    // A block copying a vanilla one, with its model, name, loot, recipe and tag.
     let files = [
-        ("Cargo.toml", include_str!("../template/Cargo.toml.in")),
-        (MANIFEST, include_str!("../template/horizon-mod.toml")),
-        ("src/lib.rs", include_str!("../template/src/lib.rs")),
+        (
+            MANIFEST,
+            include_str!("../template/content/horizon-mod.toml"),
+        ),
+        (
+            "data/{id}/horizon/block/glowing_amethyst.json",
+            include_str!("../template/content/block.json"),
+        ),
+        (
+            "assets/{id}/blockstates/glowing_amethyst.json",
+            include_str!("../template/content/blockstate.json"),
+        ),
+        (
+            "assets/{id}/models/block/glowing_amethyst.json",
+            include_str!("../template/content/model.json"),
+        ),
+        (
+            "assets/{id}/items/glowing_amethyst.json",
+            include_str!("../template/content/item.json"),
+        ),
+        (
+            "assets/{id}/lang/en_us.json",
+            include_str!("../template/content/lang.json"),
+        ),
+        (
+            "data/{id}/loot_table/blocks/glowing_amethyst.json",
+            include_str!("../template/content/loot.json"),
+        ),
+        (
+            "data/{id}/recipe/glowing_amethyst.json",
+            include_str!("../template/content/recipe.json"),
+        ),
+        (
+            "data/minecraft/tags/block/mineable/pickaxe.json",
+            include_str!("../template/content/pickaxe.json"),
+        ),
         (".gitignore", include_str!("../template/gitignore")),
     ];
+    if flag(args, "--template").is_some_and(|t| t != "content") {
+        return Err(
+            "only content mods are made here: code mods are native (docs/native-mods.md)".into(),
+        );
+    }
     for (file, text) in files {
+        let file = fill(file);
+        let file = file.as_str();
         let to = dir.join(file);
         std::fs::create_dir_all(to.parent().expect("a file in the mod"))
             .map_err(|e| e.to_string())?;
         std::fs::write(&to, fill(text)).map_err(|e| format!("{}: {e}", to.display()))?;
     }
-    Manifest::parse(&std::fs::read_to_string(dir.join(MANIFEST)).map_err(|e| e.to_string())?)?;
+    let manifest =
+        Manifest::parse(&std::fs::read_to_string(dir.join(MANIFEST)).map_err(|e| e.to_string())?)?;
+    Content::read(dir, &manifest)?;
     println!(
         "Created {} (mod id {id}). Next: cd {path} && cargo horizon-mod run",
         dir.display()
@@ -102,65 +137,82 @@ fn new(args: &[String]) -> Result<(), String> {
     Ok(())
 }
 
-/// Builds the crate in the current folder and packs `target/horizon-mod/<id>.hmod`.
-fn build(release: bool) -> Result<PathBuf, String> {
-    let manifest_text = std::fs::read_to_string(MANIFEST)
+/// Packs the content mod in the current folder into `target/horizon-mod/<id>.hmod`: the
+/// manifest and the files in `assets/` and `data/`.
+fn build() -> Result<PathBuf, String> {
+    build_in(Path::new("."))
+}
+
+fn build_in(root: &Path) -> Result<PathBuf, String> {
+    let manifest_text = std::fs::read_to_string(root.join(MANIFEST))
         .map_err(|e| format!("{MANIFEST}: {e} (run this in a mod's folder)"))?;
     let manifest = Manifest::parse(&manifest_text)?;
-    let cargo = std::env::var("CARGO").unwrap_or_else(|_| "cargo".into());
-    let mut cmd = Command::new(cargo);
-    cmd.args([
-        "build",
-        "--lib",
-        "--target",
-        TARGET,
-        "--message-format=json-render-diagnostics",
-    ]);
-    if release {
-        cmd.arg("--release");
+    if root.join("Cargo.toml").exists() {
+        return Err("a Cargo.toml: code mods are native now (docs/native-mods.md)".into());
     }
-    let out = cmd
-        .stderr(Stdio::inherit())
-        .output()
-        .map_err(|e| e.to_string())?;
-    if !out.status.success() {
+    if !manifest.capabilities.contains(&Capability::Registries) {
         return Err(format!(
-            "cargo build failed (is the target installed? rustup target add {TARGET})"
+            "a content mod has capability registries in {MANIFEST}"
         ));
     }
-    let core = String::from_utf8_lossy(&out.stdout)
-        .lines()
-        .filter_map(|l| serde_json::from_str::<serde_json::Value>(l).ok())
-        .filter(|m| m["reason"] == "compiler-artifact")
-        .flat_map(|m| m["filenames"].as_array().cloned().unwrap_or_default())
-        .filter_map(|f| f.as_str().map(PathBuf::from))
-        .rfind(|f| f.extension().is_some_and(|e| e == "wasm"))
-        .ok_or("the build made no .wasm: is the crate a cdylib?")?;
-    let wasm = componentize(&std::fs::read(&core).map_err(|e| e.to_string())?)?;
-    // The game refuses a component importing capabilities the manifest lacks.
-    manifest.check_imports(component_imports(&wasm)?.iter().map(String::as_str))?;
-    let target_dir = core.ancestors().nth(3).ok_or("unexpected target folder")?;
-    let dir = target_dir.join("horizon-mod");
+    // The same checks as the game's, and the files in the order it lists them.
+    let content = Content::read(root, &manifest)?;
+    let mut reader = content.reader()?;
+    let mut files = Vec::with_capacity(content.files.len());
+    for name in &content.files {
+        files.push((name.as_str(), reader.read(name)?));
+    }
+    let files: Vec<(&str, &[u8])> = files.iter().map(|(n, b)| (*n, b.as_slice())).collect();
+    let dir = root.join("target/horizon-mod");
     std::fs::create_dir_all(&dir).map_err(|e| e.to_string())?;
     let path = dir.join(format!("{}.hmod", manifest.id));
     // Write then rename, so a running game never reads half a file.
     let partial = path.with_extension("hmod.partial");
-    std::fs::write(&partial, Package::write(&manifest_text, &wasm)?).map_err(|e| e.to_string())?;
+    let bytes = Package::write_files(&manifest_text, None, &files)?;
+    std::fs::write(&partial, bytes).map_err(|e| e.to_string())?;
     std::fs::rename(&partial, &path).map_err(|e| e.to_string())?;
     Ok(path)
 }
 
+/// `check <file>`: the registry's checks of a submission, printed; fails
+/// when one does.
+fn check(args: &[String]) -> Result<(), String> {
+    let file = args
+        .first()
+        .filter(|a| !a.starts_with("--"))
+        .ok_or("cargo horizon-mod check <file>")?;
+    let path = Path::new(file);
+    let kind = match flag(args, "--kind") {
+        Some(k) => horizon_mods::index::Kind::from(k.to_string()),
+        None => check::kind_of(path)
+            .ok_or("pass --kind mod|modpack|resourcepack: the extension doesn't say")?,
+    };
+    let signature = flag(args, "--signature")
+        .map(|p| std::fs::read_to_string(p).map_err(|e| format!("{p}: {e}")))
+        .transpose()?;
+    let report = check::check(path, kind, flag(args, "--key"), signature.as_deref());
+    if args.iter().any(|a| a == "--json") {
+        let json = match &report {
+            Ok(r) => serde_json::json!({"ok": true, "report": r.json()}),
+            Err(e) => serde_json::json!({"ok": false, "error": e}),
+        };
+        println!("{json}");
+    }
+    let report = report?;
+    if !args.iter().any(|a| a == "--json") {
+        print!("{}", report.text());
+    }
+    Ok(())
+}
+
 fn run(args: &[String]) -> Result<(), String> {
-    let path = build(true)?;
+    let path = build()?;
     let game = flag(args, "--game")
         .map(str::to_string)
         .or_else(|| std::env::var("HORIZON_CLIENT").ok())
         .unwrap_or_else(|| "horizon-client".into());
     let extra = args.iter().skip_while(|a| *a != "--").skip(1);
-    println!(
-        "Starting {game} with {} (rebuild with `cargo horizon-mod build` to reload it)",
-        path.display()
-    );
+    println!("Starting {game} with {}", path.display());
     let status = Command::new(&game)
         .arg("--dev-mod")
         .arg(&path)
@@ -180,21 +232,43 @@ mod tests {
     use super::*;
 
     #[test]
-    fn the_template_is_a_valid_mod() {
-        let dir = std::env::temp_dir().join(format!("horizon-mod-new-{}", std::process::id()));
-        let path = dir.join("My-Mod");
-        new(&[path.display().to_string(), "--name".into(), "My Mod".into()]).unwrap();
-        let manifest =
-            Manifest::parse(&std::fs::read_to_string(path.join(MANIFEST)).unwrap()).unwrap();
-        assert_eq!(
-            (manifest.id.as_str(), manifest.name.as_str()),
-            ("my_mod", "My Mod")
-        );
-        let cargo = std::fs::read_to_string(path.join("Cargo.toml")).unwrap();
-        assert!(cargo.contains("name = \"my-mod\"") && cargo.contains(SDK_GIT));
+    fn the_content_template_builds_and_checks_with_no_code() {
+        let dir = std::env::temp_dir().join(format!("horizon-mod-content-{}", std::process::id()));
+        let path = dir.join("gems");
+        let new_args = [
+            path.display().to_string(),
+            "--template".into(),
+            "content".into(),
+        ];
+        new(&new_args).unwrap();
+        assert!(!path.join("Cargo.toml").exists());
+        let hmod = build_in(&path).unwrap();
+        assert_eq!(hmod, path.join("target/horizon-mod/gems.hmod"));
+        let package = Package::read(&hmod).unwrap();
+        assert!(package.wasm.is_none());
+        let content = Content::read(&hmod, &package.manifest).unwrap();
         assert!(
-            new(&[path.display().to_string()]).is_err(),
-            "never overwrites"
+            content
+                .files
+                .contains(&"data/gems/horizon/block/glowing_amethyst.json".into())
+        );
+        assert_eq!(content.files.len(), 8, "{:?}", content.files);
+        let report = check::check(&hmod, check::kind_of(&hmod).unwrap(), None, None).unwrap();
+        assert!(
+            report.text().contains("no code: content only"),
+            "{}",
+            report.text()
+        );
+        // Code is native now.
+        std::fs::write(path.join("Cargo.toml"), "").unwrap();
+        assert!(build_in(&path).unwrap_err().contains("native"));
+        assert!(
+            new(&[
+                dir.join("x").display().to_string(),
+                "--template".into(),
+                "lua".into()
+            ])
+            .is_err()
         );
         std::fs::remove_dir_all(&dir).unwrap();
     }

crates/cargo-horizon-mod/src/registry.rs

@@ -0,0 +1,229 @@
+//! `cargo horizon-mod registry build|review|check|list`: the registry repository's CI
+//! (`horizon-rust/horizon-mods`, docs/api/mod-index.md). Network-free: the
+//! workflow downloads the files and publishes what this writes.
+use horizon_mods::index::{
+    FILE_HOST,
+    registry::{self, Sources},
+};
+use std::path::Path;
+
+/// Where the registry's site is published (its icons).
+const SITE: &str = "https://horizon-rust.github.io/horizon-mods/";
+
+const USAGE: &str = "usage: cargo horizon-mod registry build <checkout> --files <dir> --out <index.json> [--release <url>] [--site <url>] [--generated <time>]
+       cargo horizon-mod registry review <base checkout> <head checkout> --author <login> [--json]
+       cargo horizon-mod registry check <base checkout> <head checkout> --files <dir>
+       cargo horizon-mod registry list <checkout>
+       cargo horizon-mod registry release <checkout> <id> <file> --tag <tag> --published <YYYY-MM-DD> [--notes <file>] [--signature <file>] [--game <version>]
+       cargo horizon-mod registry page <checkout> <id> <horizon-registry.toml>";
+
+fn flag<'a>(args: &'a [String], name: &str) -> Option<&'a str> {
+    super::flag(args, name)
+}
+
+fn positional(args: &[String]) -> Vec<&str> {
+    let mut out = Vec::new();
+    let mut skip = false;
+    for a in args {
+        if skip {
+            skip = false;
+        } else if a == "--json" {
+        } else if a.starts_with("--") {
+            skip = true;
+        } else {
+            out.push(a.as_str());
+        }
+    }
+    out
+}
+
+fn lines(errors: Vec<String>) -> String {
+    format!("{} problem(s):\n  {}", errors.len(), errors.join("\n  "))
+}
+
+pub fn main(args: &[String]) -> Result<(), String> {
+    let rest = args.get(1..).unwrap_or_default();
+    let pos = positional(rest);
+    match args.first().map(String::as_str) {
+        Some("build") => {
+            let [checkout] = pos[..] else {
+                return Err(USAGE.into());
+            };
+            let (files, out) = (flag(rest, "--files"), flag(rest, "--out"));
+            let (Some(files), Some(out)) = (files, out) else {
+                return Err(USAGE.into());
+            };
+            let generated = flag(rest, "--generated")
+                .map(str::to_owned)
+                .or_else(|| std::env::var("REGISTRY_GENERATED").ok())
+                .unwrap_or_default();
+            let index = registry::build(&Sources {
+                registry: Path::new(checkout),
+                files: Path::new(files),
+                release: flag(rest, "--release").unwrap_or(FILE_HOST),
+                site: flag(rest, "--site").unwrap_or(SITE),
+                generated,
+            })
+            .map_err(lines)?;
+            let text = serde_json::to_string_pretty(&index).map_err(|e| e.to_string())?;
+            std::fs::write(out, text + "\n").map_err(|e| format!("{out}: {e}"))?;
+            println!(
+                "Wrote {out}: {} project(s), {} taken down",
+                index.projects.len(),
+                index.revoked.len()
+            );
+            Ok(())
+        }
+        Some("review") => {
+            let [base, head] = pos[..] else {
+                return Err(USAGE.into());
+            };
+            let author = flag(rest, "--author").ok_or(USAGE)?;
+            let (base, _) = registry::load(Path::new(base)).map_err(lines)?;
+            let (head, _) = registry::load(Path::new(head)).map_err(lines)?;
+            let review = registry::review(&base, &head, author);
+            if rest.iter().any(|a| a == "--json") {
+                let json = serde_json::json!({"errors": review.errors, "notes": review.notes});
+                println!("{json}");
+            } else {
+                for n in &review.notes {
+                    println!("note: {n}");
+                }
+                for e in &review.errors {
+                    println!("error: {e}");
+                }
+            }
+            if review.errors.is_empty() {
+                Ok(())
+            } else {
+                Err(format!(
+                    "{} change(s) the registry refuses",
+                    review.errors.len()
+                ))
+            }
+        }
+        // `check` (and its trial run) on each file `head` lists and `base`
+        // doesn't: a pull request's new files.
+        Some("check") => {
+            let [base, head] = pos[..] else {
+                return Err(USAGE.into());
+            };
+            let files = Path::new(flag(rest, "--files").ok_or(USAGE)?);
+            let old: Vec<String> = match registry::load(Path::new(base)) {
+                Ok((entries, _)) => entries
+                    .iter()
+                    .flat_map(|e| e.versions.iter().map(|v| v.sha256.clone()))
+                    .collect(),
+                // The first pull request has no entries to compare with.
+                Err(_) => Vec::new(),
+            };
+            let (entries, _) = registry::load(Path::new(head)).map_err(lines)?;
+            let mut failed = 0;
+            for e in &entries {
+                for v in e.versions.iter().filter(|v| !old.contains(&v.sha256)) {
+                    println!("{} {} ({}):", e.id, v.version, v.file);
+                    let report = crate::check::check(
+                        &files.join(&v.sha256),
+                        e.kind.clone(),
+                        e.key.as_deref(),
+                        v.signature.as_deref(),
+                    );
+                    match report {
+                        Ok(r) => print!("{}", r.text()),
+                        Err(err) => {
+                            failed += 1;
+                            println!("  error: {err}");
+                        }
+                    }
+                }
+            }
+            if failed == 0 {
+                Ok(())
+            } else {
+                Err(format!("{failed} file(s) failed their check"))
+            }
+        }
+        // The files CI must download for `build`: `<sha256> <id> <version> <file>`.
+        Some("list") => {
+            let [checkout] = pos[..] else {
+                return Err(USAGE.into());
+            };
+            let (entries, _) = registry::load(Path::new(checkout)).map_err(lines)?;
+            for e in &entries {
+                for v in &e.versions {
+                    println!("{} {} {} {}", v.sha256, e.id, v.version, v.file);
+                }
+            }
+            Ok(())
+        }
+        // A release of a project's repository, downloaded: the checks of a submission, then the
+        // version as the index lists it (JSON on stdout), for the registry's release sync.
+        Some("release") => {
+            let [checkout, id, file] = pos[..] else {
+                return Err(USAGE.into());
+            };
+            let (tag, published) = (
+                flag(rest, "--tag").ok_or(USAGE)?,
+                flag(rest, "--published").ok_or(USAGE)?,
+            );
+            let read = |name: &str| {
+                flag(rest, name)
+                    .map(|p| std::fs::read_to_string(p).map_err(|e| format!("{p}: {e}")))
+                    .transpose()
+            };
+            let (notes, signature) = (read("--notes")?, read("--signature")?);
+            let entry = entry_of(checkout, id)?;
+            let path = Path::new(file);
+            let cache = registry::Cache::read(Path::new(checkout), id)?;
+            let entry = entry.resolved(&cache.page);
+            let name = path.file_name().and_then(|n| n.to_str()).unwrap_or("");
+            crate::check::check(
+                path,
+                entry.kind.clone(),
+                entry.key.as_deref(),
+                signature.as_deref(),
+            )?;
+            let version = registry::release_version(
+                &entry,
+                &registry::Release {
+                    tag,
+                    published,
+                    notes: notes.as_deref().unwrap_or(""),
+                    asset: flag(rest, "--name").unwrap_or(name),
+                    game: flag(rest, "--game").unwrap_or("26.3"),
+                    signature: signature.as_deref(),
+                },
+                path,
+            )?;
+            println!(
+                "{}",
+                serde_json::to_string(&version).map_err(|e| e.to_string())?
+            );
+            Ok(())
+        }
+        // The page file of a project's repository, checked against its entry: the page as JSON.
+        Some("page") => {
+            let [checkout, id, file] = pos[..] else {
+                return Err(USAGE.into());
+            };
+            let entry = entry_of(checkout, id)?;
+            let text = std::fs::read_to_string(file).map_err(|e| format!("{file}: {e}"))?;
+            let page = registry::page(&entry, &text)?;
+            println!(
+                "{}",
+                serde_json::to_string(&page).map_err(|e| e.to_string())?
+            );
+            Ok(())
+        }
+        _ => Err(USAGE.into()),
+    }
+}
+
+/// `mods/<id>.toml` of the checkout, which must name a repository.
+fn entry_of(checkout: &str, id: &str) -> Result<registry::Entry, String> {
+    let (entries, _) = registry::load(Path::new(checkout)).map_err(lines)?;
+    entries
+        .into_iter()
+        .find(|e| e.id == id && e.repo.is_some())
+        .ok_or_else(|| format!("{id}: no entry with a repo"))
+}

crates/cargo-horizon-mod/template/Cargo.toml.in

@@ -1,14 +0,0 @@
-[package]
-name = "{crate}"
-version = "0.1.0"
-edition = "2024"
-
-[lib]
-crate-type = ["cdylib"]
-
-[dependencies]
-horizon-mod-sdk = {sdk}
-
-[profile.release]
-opt-level = "s"
-lto = true

crates/cargo-horizon-mod/template/content/block.json

@@ -0,0 +1,4 @@
+{
+  "template": "minecraft:amethyst_block",
+  "properties": { "hardness": 2.0, "light": 7 }
+}

crates/cargo-horizon-mod/template/content/blockstate.json

@@ -0,0 +1,5 @@
+{
+  "variants": {
+    "": { "model": "{id}:block/glowing_amethyst" }
+  }
+}

crates/cargo-horizon-mod/template/content/horizon-mod.toml

@@ -0,0 +1,10 @@
+id = "{id}"
+name = "{name}"
+version = "0.1.0"
+description = ""
+authors = []
+# A content mod: blocks and items from data/ and assets/, no code (API 0.2).
+api = "0.2"
+side = "both"
+# registries: "May add blocks and items to your worlds".
+capabilities = ["registries"]

crates/cargo-horizon-mod/template/content/item.json

@@ -0,0 +1,3 @@
+{
+  "model": { "type": "minecraft:model", "model": "{id}:block/glowing_amethyst" }
+}

crates/cargo-horizon-mod/template/content/lang.json

@@ -0,0 +1,3 @@
+{
+  "block.{id}.glowing_amethyst": "Glowing Amethyst"
+}

crates/cargo-horizon-mod/template/content/loot.json

@@ -0,0 +1,11 @@
+{
+  "type": "minecraft:block",
+  "pools": [
+    {
+      "condition": { "type": "minecraft:survives_explosion" },
+      "entries": [{ "type": "minecraft:item", "name": "{id}:glowing_amethyst" }],
+      "rolls": 1
+    }
+  ],
+  "random_sequence": "{id}:blocks/glowing_amethyst"
+}

crates/cargo-horizon-mod/template/content/model.json

@@ -0,0 +1,4 @@
+{
+  "parent": "minecraft:block/cube_all",
+  "textures": { "all": "minecraft:block/amethyst_block" }
+}

crates/cargo-horizon-mod/template/content/pickaxe.json

@@ -0,0 +1,3 @@
+{
+  "values": ["{id}:glowing_amethyst"]
+}

crates/cargo-horizon-mod/template/content/recipe.json

@@ -0,0 +1,6 @@
+{
+  "type": "minecraft:crafting_shapeless",
+  "category": "building",
+  "ingredients": ["minecraft:amethyst_block", "minecraft:glowstone_dust"],
+  "result": { "id": "{id}:glowing_amethyst" }
+}

crates/cargo-horizon-mod/template/horizon-mod.toml

@@ -1,12 +0,0 @@
-id = "{id}"
-name = "{name}"
-version = "0.1.0"
-description = ""
-authors = []
-# The Horizon mod API the SDK targets.
-api = "0.1"
-# client: runs in the player's game.
-side = "client"
-# What the mod may do, shown to players before they turn it on:
-# game-read (position, health, time), chat (show messages), hud (draw text).
-capabilities = ["chat"]

crates/cargo-horizon-mod/template/src/lib.rs

@@ -1,19 +0,0 @@
-use horizon_mod_sdk::{Mod, Registration, chat};
-
-struct MyMod {
-    greeted: u32,
-}
-
-impl Mod for MyMod {
-    fn init() -> Result<(Self, Registration), String> {
-        Ok((MyMod { greeted: 0 }, Registration::new().command("hello")))
-    }
-
-    fn command(&mut self, _name: &str, args: &str) -> Result<Option<String>, String> {
-        self.greeted += 1;
-        chat::show(&format!("Hello {args}! ({} so far)", self.greeted));
-        Ok(None)
-    }
-}
-
-horizon_mod_sdk::export_mod!(MyMod);

crates/horizon-anticheat/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "horizon-anticheat"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+rust-version = "1.85"
+description = "The dedicated server's anticheat: its [anticheat] settings, violation levels and the checks' rules, with no game state (docs/anticheat.md)"
+
+[dependencies]
+serde = { version = "1", features = ["derive"] }
+toml = "1.1"
+
+[lints]
+workspace = true

crates/horizon-anticheat/src/lib.rs

@@ -0,0 +1,295 @@
+//! The dedicated server's anticheat (docs/anticheat.md), without the game: the `[anticheat]` section of
+//! `server.toml`, each player's violation levels, and the rules of the checks. The server's hub
+//! (`horizon_client::lan`) feeds it what players send and carries out what it decides.
+//!
+//! It is off unless the owner turns it on. A check that fails *flags* the player: its violation level
+//! (VL) rises by the flag's weight and falls back by `decay` a second. From `setback` on, the move or
+//! action is cancelled (the player is sent back where the server last had them); from `alert` on,
+//! online operators and the console are told; from `kick` on, the player is disconnected. Nothing bans.
+//! Any threshold at 0 turns that action off.
+//!
+//! The checks are written from vanilla 26.3's own rules and from what cheats are publicly described to
+//! do, never from another anticheat's code.
+
+use serde::{Deserialize, Serialize};
+
+pub mod timer;
+
+/// What one check's violation level leads to.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct Actions {
+    pub setback: f32,
+    pub alert: f32,
+    pub kick: f32,
+    /// Violation level lost each second.
+    pub decay: f32,
+}
+
+macro_rules! checks {
+    ($(
+        $(#[$doc:meta])*
+        $field:ident: $Check:ident => $Config:ident [$setback:expr, $alert:expr, $kick:expr, $decay:expr] {
+            $( $(#[$xdoc:meta])* $extra:ident: $ty:ty = $default:expr, )*
+        }
+    )*) => {
+        /// Every check, in the order of the players' violation levels.
+        #[derive(Clone, Copy, Debug, PartialEq, Eq)]
+        pub enum Check { $($Check,)* }
+
+        impl Check {
+            pub const ALL: &[Check] = &[$(Check::$Check,)*];
+            /// Its name in `server.toml` and in alerts.
+            pub fn name(self) -> &'static str {
+                match self { $(Check::$Check => stringify!($field),)* }
+            }
+        }
+
+        $(
+            $(#[$doc])*
+            #[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+            #[serde(default, deny_unknown_fields)]
+            pub struct $Config {
+                pub enabled: bool,
+                pub setback: f32,
+                pub alert: f32,
+                pub kick: f32,
+                pub decay: f32,
+                $( $(#[$xdoc])* pub $extra: $ty, )*
+            }
+
+            impl Default for $Config {
+                fn default() -> Self {
+                    Self {
+                        enabled: true,
+                        setback: $setback,
+                        alert: $alert,
+                        kick: $kick,
+                        decay: $decay,
+                        $($extra: $default,)*
+                    }
+                }
+            }
+        )*
+
+        /// `server.toml`'s `[anticheat]`: off by default.
+        #[derive(Clone, Debug, PartialEq, Serialize, Deserialize)]
+        #[serde(default, deny_unknown_fields)]
+        pub struct Config {
+            pub enabled: bool,
+            /// Tell online operators of an alert in their chat (the console and the log always are).
+            pub alerts: bool,
+            /// The permission level a player needs to see alerts.
+            pub alert_level: u8,
+            /// Every flag, one line each, relative to the server's folder; empty: no file.
+            pub log: String,
+            $(pub $field: $Config,)*
+        }
+
+        impl Default for Config {
+            fn default() -> Self {
+                Self {
+                    enabled: false,
+                    alerts: true,
+                    alert_level: 2,
+                    log: "logs/anticheat.log".into(),
+                    $($field: $Config::default(),)*
+                }
+            }
+        }
+
+        impl Config {
+            /// Whether `check` runs: the anticheat and the check both on.
+            pub fn runs(&self, check: Check) -> bool {
+                self.enabled && match check { $(Check::$Check => self.$field.enabled,)* }
+            }
+
+            pub fn actions(&self, check: Check) -> Actions {
+                match check {
+                    $(Check::$Check => {
+                        let c = &self.$field;
+                        Actions { setback: c.setback, alert: c.alert, kick: c.kick, decay: c.decay }
+                    })*
+                }
+            }
+        }
+    };
+}
+
+checks! {
+    /// Timer: more client ticks than the server's clock allows (a sped-up game). Vanilla's client ends
+    /// every tick with ServerboundClientTickEndPacket, at the server's tick rate; each one spends a tick's
+    /// time from a balance that wall-clock time fills, capped so a pause can't be saved up for a burst.
+    timer: Timer => TimerConfig [2.0, 5.0, 20.0, 0.02] {
+        /// How far ahead of the clock, in milliseconds, a client may get before it is flagged.
+        tolerance_ms: f64 = 300.0,
+        /// The most time, in milliseconds, a quiet connection banks for the ticks that follow (a lag
+        /// spike's backlog arrives at once).
+        max_lag_ms: f64 = 1000.0,
+    }
+}
+
+/// How many checks there are.
+pub const CHECKS: usize = Check::ALL.len();
+
+impl Config {
+    /// The `[anticheat]` section of a whole `server.toml`; the default (off) when it has none.
+    pub fn from_server_toml(text: &str) -> Result<Self, String> {
+        #[derive(Deserialize)]
+        struct File {
+            #[serde(default)]
+            anticheat: Config,
+        }
+        // Other sections are the supervisor's to check: only this one is read here.
+        let mut table: toml::Table = toml::from_str(text).map_err(|e| e.to_string())?;
+        let mut only = toml::Table::new();
+        if let Some(section) = table.remove("anticheat") {
+            only.insert("anticheat".into(), section);
+        }
+        let file: File = only
+            .try_into()
+            .map_err(|e: toml::de::Error| format!("[anticheat]: {e}"))?;
+        file.anticheat.check()?;
+        Ok(file.anticheat)
+    }
+
+    /// Thresholds can't be negative.
+    pub fn check(&self) -> Result<(), String> {
+        for &c in Check::ALL {
+            let a = self.actions(c);
+            if [a.setback, a.alert, a.kick, a.decay]
+                .iter()
+                .any(|v| !v.is_finite() || *v < 0.0)
+            {
+                return Err(format!(
+                    "anticheat.{}: setback, alert, kick and decay are numbers from 0 up",
+                    c.name()
+                ));
+            }
+        }
+        Ok(())
+    }
+}
+
+/// What a flag leads to.
+#[derive(Clone, Copy, Debug, Default, PartialEq)]
+pub struct Verdict {
+    /// The check's violation level after the flag.
+    pub vl: f32,
+    /// Cancel the move or action.
+    pub setback: bool,
+    /// Tell operators and the console (at most once a second per check).
+    pub alert: bool,
+    pub kick: bool,
+}
+
+/// One player's anticheat state. Clean players cost nothing: levels only change when a check flags.
+#[derive(Clone, Debug, Default)]
+pub struct Player {
+    vl: [f32; CHECKS],
+    /// The server tick of each check's last flag (its decay runs from there).
+    flagged: [u64; CHECKS],
+    /// The server tick of each check's last alert.
+    alerted: [Option<u64>; CHECKS],
+    pub timer: timer::Balance,
+}
+
+impl Player {
+    /// The check's violation level at `tick`, with its decay since the last flag.
+    pub fn vl(&self, config: &Config, check: Check, tick: u64) -> f32 {
+        let i = check as usize;
+        let seconds = tick.saturating_sub(self.flagged[i]) as f32 / 20.0;
+        (self.vl[i] - config.actions(check).decay * seconds).max(0.0)
+    }
+
+    /// `check` failed with this weight at server tick `tick`.
+    pub fn flag(&mut self, config: &Config, check: Check, weight: f32, tick: u64) -> Verdict {
+        let i = check as usize;
+        let a = config.actions(check);
+        let vl = self.vl(config, check, tick) + weight;
+        self.vl[i] = vl;
+        self.flagged[i] = tick;
+        let reached = |threshold: f32| threshold > 0.0 && vl >= threshold;
+        let alert = reached(a.alert) && self.alerted[i].is_none_or(|t| tick >= t + 20);
+        if alert {
+            self.alerted[i] = Some(tick);
+        }
+        Verdict {
+            vl,
+            setback: reached(a.setback),
+            alert,
+            kick: reached(a.kick),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn on() -> Config {
+        Config {
+            enabled: true,
+            ..Config::default()
+        }
+    }
+
+    #[test]
+    fn off_by_default_and_without_a_section() {
+        assert!(!Config::default().enabled);
+        let c = Config::from_server_toml("[server]\nport = 25565\n").unwrap();
+        assert_eq!(c, Config::default());
+        assert!(!c.runs(Check::Timer));
+    }
+
+    #[test]
+    fn reads_its_section() {
+        let text = "[server]\nport = 1\n[anticheat]\nenabled = true\n[anticheat.timer]\nkick = 0\ntolerance_ms = 500\n";
+        let c = Config::from_server_toml(text).unwrap();
+        assert!(c.runs(Check::Timer));
+        assert_eq!(c.timer.kick, 0.0);
+        assert_eq!(c.timer.tolerance_ms, 500.0);
+        assert_eq!(c.timer.alert, TimerConfig::default().alert);
+        let off = "[anticheat]\nenabled = true\n[anticheat.timer]\nenabled = false\n";
+        assert!(!Config::from_server_toml(off).unwrap().runs(Check::Timer));
+    }
+
+    #[test]
+    fn refuses_unknown_keys_and_negative_levels() {
+        assert!(Config::from_server_toml("[anticheat]\nenable = true\n").is_err());
+        assert!(Config::from_server_toml("[anticheat.timer]\nkick = -1\n").is_err());
+    }
+
+    #[test]
+    fn levels_rise_decay_and_act_in_order() {
+        let mut c = on();
+        c.timer = TimerConfig {
+            setback: 2.0,
+            alert: 3.0,
+            kick: 5.0,
+            decay: 1.0,
+            ..TimerConfig::default()
+        };
+        let mut p = Player::default();
+        let v = p.flag(&c, Check::Timer, 1.0, 100);
+        assert_eq!((v.setback, v.alert, v.kick), (false, false, false));
+        let v = p.flag(&c, Check::Timer, 1.0, 100);
+        assert_eq!((v.vl, v.setback, v.alert), (2.0, true, false));
+        let v = p.flag(&c, Check::Timer, 1.0, 100);
+        assert!(v.alert && !v.kick);
+        // At most one alert a second.
+        assert!(!p.flag(&c, Check::Timer, 0.5, 110).alert);
+        // 3 at tick 110 (half a level gone, half added); two seconds later two more are gone.
+        assert_eq!(p.vl(&c, Check::Timer, 150), 1.0);
+        assert_eq!(p.vl(&c, Check::Timer, 10_000), 0.0);
+        let v = p.flag(&c, Check::Timer, 5.0, 10_000);
+        assert!(v.kick && v.alert);
+    }
+
+    #[test]
+    fn zero_turns_an_action_off() {
+        let mut c = on();
+        c.timer.kick = 0.0;
+        let mut p = Player::default();
+        assert!(!p.flag(&c, Check::Timer, 1000.0, 1).kick);
+    }
+}

crates/horizon-anticheat/src/timer.rs

@@ -0,0 +1,111 @@
+//! The timer check's balance: how far a client's ticks are behind (positive) or ahead (negative) of the
+//! server's clock, in milliseconds.
+//!
+//! The server adds the wall-clock time of each of its ticks, and every ServerboundClientTickEndPacket
+//! takes away the length of one tick at the server's tick rate (vanilla's client ticks at that rate,
+//! `TickRateManager.millisecondsPerTick`). The balance is capped at `max_lag_ms` *after* the tick's
+//! packets are counted: a slow server tick that handles a second of packets at once also added that
+//! second, and a quiet connection banks at most `max_lag_ms` for the burst that ends a lag spike.
+
+use crate::TimerConfig;
+
+#[derive(Clone, Debug, Default)]
+pub struct Balance {
+    pub ms: f64,
+}
+
+impl Balance {
+    /// The start of a server tick that came `elapsed_ms` after the previous one.
+    pub fn elapse(&mut self, elapsed_ms: f64, config: &TimerConfig) {
+        self.ms = self.ms.min(config.max_lag_ms) + elapsed_ms;
+    }
+
+    /// One client tick ended, at a tick rate of `tick_rate` a second. Some(how far ahead, in ms) when the
+    /// client is further ahead than the tolerance; the balance starts again from zero then, so a
+    /// sustained speed-up is flagged again each time it gets that far ahead.
+    pub fn tick_end(&mut self, tick_rate: f32, config: &TimerConfig) -> Option<f64> {
+        self.ms -= 1000.0 / f64::from(tick_rate.max(1.0));
+        if self.ms < -config.tolerance_ms {
+            let ahead = -self.ms;
+            self.ms = 0.0;
+            return Some(ahead);
+        }
+        None
+    }
+
+    /// The tick rate changed or the player arrived: start again.
+    pub fn reset(&mut self) {
+        self.ms = 0.0;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// `seconds` of server ticks of `server_ms` each, with `per_tick` client ticks handled in each.
+    fn run(b: &mut Balance, server_ms: f64, per_tick: f64, seconds: f64) -> usize {
+        let c = TimerConfig::default();
+        let mut owed = 0.0;
+        let mut flags = 0;
+        for _ in 0..(seconds * 1000.0 / server_ms) as usize {
+            b.elapse(server_ms, &c);
+            owed += per_tick;
+            while owed >= 1.0 {
+                owed -= 1.0;
+                flags += usize::from(b.tick_end(20.0, &c).is_some());
+            }
+        }
+        flags
+    }
+
+    #[test]
+    fn a_vanilla_client_is_never_flagged() {
+        let mut b = Balance::default();
+        assert_eq!(run(&mut b, 50.0, 1.0, 600.0), 0);
+        // A server that runs at 10 ticks a second handles two client ticks in each.
+        assert_eq!(run(&mut b, 100.0, 2.0, 600.0), 0);
+    }
+
+    #[test]
+    fn a_slow_server_tick_with_its_backlog_is_not_flagged() {
+        let (mut b, c) = (Balance::default(), TimerConfig::default());
+        b.elapse(3000.0, &c);
+        for _ in 0..60 {
+            assert_eq!(b.tick_end(20.0, &c), None);
+        }
+    }
+
+    #[test]
+    fn a_short_network_stall_is_not_flagged() {
+        let (mut b, c) = (Balance::default(), TimerConfig::default());
+        // 800 ms with nothing arriving, then the 16 ticks sent meanwhile.
+        for _ in 0..16 {
+            b.elapse(50.0, &c);
+        }
+        b.elapse(50.0, &c);
+        for _ in 0..17 {
+            assert_eq!(b.tick_end(20.0, &c), None);
+        }
+    }
+
+    #[test]
+    fn a_sped_up_client_is_flagged_again_and_again() {
+        let mut b = Balance::default();
+        // 10 % faster: 5 ms ahead each tick, 300 ms after 3 s, so close to 20 flags a minute.
+        let flags = run(&mut b, 50.0, 1.1, 60.0);
+        assert!((15..=20).contains(&flags), "{flags}");
+        // Twice as fast: a flag every 7 ticks.
+        assert!(run(&mut Balance::default(), 50.0, 2.0, 10.0) >= 25);
+    }
+
+    #[test]
+    fn a_pause_cant_be_saved_for_a_burst() {
+        let (mut b, c) = (Balance::default(), TimerConfig::default());
+        for _ in 0..200 {
+            b.elapse(50.0, &c);
+        }
+        let flagged = (0..60).any(|_| b.tick_end(20.0, &c).is_some());
+        assert!(flagged);
+    }
+}

crates/horizon-assets/src/blockstate/choice.rs

@@ -4,15 +4,15 @@ use crate::json::{Result, error};
 use horizon_core::random::RandomSource;
 
 #[derive(Clone, Debug)]
-enum Choice {
-    Single(Variant),
+enum Choice<T> {
+    Single(T),
     Weighted {
-        variants: Vec<Variant>,
+        variants: Vec<T>,
         ends: Vec<i32>,
         total: i32,
     },
 }
-impl Choice {
+impl Choice<Variant> {
     fn new(value: &VariantSet) -> Result<Self> {
         match value {
             VariantSet::Single(value) => Ok(Self::Single(value.clone())),
@@ -41,7 +41,23 @@ impl Choice {
             }
         }
     }
-    fn select(&self, random: &mut impl RandomSource) -> &Variant {
+}
+impl<T> Choice<T> {
+    fn map<U>(&self, f: &mut impl FnMut(&T) -> U) -> Choice<U> {
+        match self {
+            Self::Single(value) => Choice::Single(f(value)),
+            Self::Weighted {
+                variants,
+                ends,
+                total,
+            } => Choice::Weighted {
+                variants: variants.iter().map(&mut *f).collect(),
+                ends: ends.clone(),
+                total: *total,
+            },
+        }
+    }
+    fn select(&self, random: &mut impl RandomSource) -> &T {
         match self {
             Self::Single(value) => value,
             Self::Weighted {
@@ -60,10 +76,11 @@ impl Choice {
 }
 /// Compile once per definition and share across its bound block states. Prefix
 /// sums avoid rebuilding weight totals or scanning all entries during selection.
+/// `map` swaps each variant for what it stands for (its baked model).
 #[derive(Clone, Debug)]
-pub struct CompiledChoices {
-    variants: Vec<Choice>,
-    multipart: Vec<Choice>,
+pub struct CompiledChoices<T = Variant> {
+    variants: Vec<Choice<T>>,
+    multipart: Vec<Choice<T>>,
 }
 impl CompiledChoices {
     pub fn new(definition: &BlockStateDefinition) -> Result<Self> {
@@ -82,10 +99,19 @@ impl CompiledChoices {
                 .collect::<Result<_>>()?,
         })
     }
+}
+impl<T> CompiledChoices<T> {
+    /// The same choices, with `f` of each variant in its place.
+    pub fn map<U>(&self, mut f: impl FnMut(&T) -> U) -> CompiledChoices<U> {
+        CompiledChoices {
+            variants: self.variants.iter().map(|c| c.map(&mut f)).collect(),
+            multipart: self.multipart.iter().map(|c| c.map(&mut f)).collect(),
+        }
+    }
     /// The variant `particleMaterial` comes from: the first entry of a weighted
     /// list (`WeightedVariants`) and, for a multipart root, of its first
     /// selector whether or not that selector applies (`MultiPartModel`).
-    pub fn particle_variant(&self, selected: &SelectedModels) -> Option<&Variant> {
+    pub fn particle_variant(&self, selected: &SelectedModels) -> Option<&T> {
         let choice = match selected {
             SelectedModels::Variant(index) => self.variants.get(*index)?,
             SelectedModels::Multipart(_) => self.multipart.first()?,
@@ -95,14 +121,23 @@ impl CompiledChoices {
             Choice::Weighted { variants, .. } => variants.first()?,
         })
     }
-    /// Append selected variants without allocating intermediate part lists. A
-    /// multipart root consumes nextLong even for an empty selected subset, then
-    /// resets the same random source to that seed before each selected part.
+    /// Append selected variants without allocating intermediate part lists.
     pub fn collect<'a>(
         &'a self,
         selected: &SelectedModels,
         random: &mut impl RandomSource,
-        output: &mut Vec<&'a Variant>,
+        output: &mut Vec<&'a T>,
+    ) -> Result<()> {
+        self.for_each(selected, random, |v| output.push(v))
+    }
+    /// Each selected variant, in order. A multipart root consumes nextLong
+    /// even for an empty selected subset, then resets the same random source
+    /// to that seed before each selected part.
+    pub fn for_each<'a>(
+        &'a self,
+        selected: &SelectedModels,
+        random: &mut impl RandomSource,
+        mut f: impl FnMut(&'a T),
     ) -> Result<()> {
         match selected {
             SelectedModels::Variant(index) => {
@@ -110,7 +145,7 @@ impl CompiledChoices {
                     .variants
                     .get(*index)
                     .ok_or_else(|| error("invalid variant selection"))?;
-                output.push(choice.select(random));
+                f(choice.select(random));
             }
             SelectedModels::Multipart(indices) => {
                 if indices.iter().any(|index| *index >= self.multipart.len()) {
@@ -119,7 +154,7 @@ impl CompiledChoices {
                 let seed = random.next_long();
                 for index in indices {
                     random.set_seed(seed);
-                    output.push(self.multipart[*index].select(random));
+                    f(self.multipart[*index].select(random));
                 }
             }
         }

crates/horizon-assets/src/item_model.rs

@@ -1031,19 +1031,22 @@ pub struct ItemModels {
 }
 
 impl ItemModels {
-    pub fn components(&self, stack: &StackView) -> Components {
-        let mut out = self
-            .prototypes
-            .get(&stack.item)
-            .cloned()
-            .unwrap_or_default();
+    /// The stack's components: its item's defaults with the stack's patch on top. A stack
+    /// with no patch (most stacks a screen draws) borrows the defaults instead of copying them.
+    pub fn components(&self, stack: &StackView) -> std::borrow::Cow<'_, Components> {
+        static NONE: Components = BTreeMap::new();
+        let prototype = self.prototypes.get(&stack.item).unwrap_or(&NONE);
+        if stack.patch.is_empty() {
+            return std::borrow::Cow::Borrowed(prototype);
+        }
+        let mut out = prototype.clone();
         for (key, value) in &stack.patch {
             match value {
                 Some(v) => out.insert(key.clone(), v.clone()),
                 None => out.remove(key),
             };
         }
-        out
+        std::borrow::Cow::Owned(out)
     }
     /// `ItemModelResolver.updateForTopItem`.
     pub fn resolve(&self, stack: &StackView, ctx: &Context, env: &dyn ItemEnv) -> ResolvedItem {

crates/horizon-bots/src/main.rs

@@ -21,18 +21,19 @@ use horizon_protocol::{
     connection::{ConnWriter, Connection},
     crypto::offline_uuid,
     ids,
+    item::Stack,
     packets::{
         Empty, configuration,
         handshake::{self, Intention},
         login::{self, ServerHello},
-        play,
+        play, recipes,
     },
 };
 use serde_json::json;
 use std::{
     collections::HashSet,
     sync::{
-        Arc, Mutex,
+        Arc, LazyLock, Mutex,
         atomic::{AtomicBool, AtomicU64, Ordering},
     },
     thread,
@@ -44,29 +45,72 @@ horizon-bots: load-test bots for a Minecraft Java Edition 26.3 server (offline m
 
   --server HOST:PORT     default 127.0.0.1:25565
   --bots N               default 10
-  --behaviour B          idle, walk, explore or mixed (60 % walk, 20 % explore, 20 % idle); default mixed
+  --behaviour B          idle, walk, explore or mixed (60 % walk, 20 % explore, 20 % idle); default mixed.
+                         stand: stays on the ground where the server puts it (/tp), for a survival test.
+                         One abusive client, to test a server's limits (run it beside a normal crowd):
+                         flood-move (--flood moves a tick, each 64 to 256 blocks away, ignoring chunks),
+                         flood-acks (--flood chunk batch acks asking for 64 chunks a tick, while exploring),
+                         flood-packets (--flood rotations a tick),
+                         flood-chunks (one move a tick, 9.9 blocks straight ahead: as fast as the
+                         moved-too-quickly check allows, never waiting for chunks),
+                         and --flood a tick of packets that cost the server work:
+                         flood-use (place and break stone around itself), flood-click (inventory
+                         clicks with a stale state), flood-suggest (command suggestions, every
+                         other one 30 000 characters long), flood-book (100 pages of 1024 characters
+                         into a writable book), flood-sign (four 384-character lines on the block
+                         below), flood-recipe (recipe book placements)
+  --flood N              packets a tick for the flood behaviours; default 100
+  --attack NAME          attack the player NAME twice a second, from wherever the bot is (a reach test);
+                         the report gives each bot's last health
+  --attack-after S       start attacking S seconds after joining; default 5
+  --no-read              stop reading from the server once spawned (a client that lets the
+                         server's replies pile up)
   --join-every SECONDS   default 1
   --seconds N            how long to run after the first bot joins; default 60
   --view-distance N      what the bots ask for; default 10
   --seed N               default 12345
   --explore-speed B      blocks a second an explore bot flies; default 22 (as fast as chunks come)
   --name PREFIX          bot names: PREFIX0, PREFIX1...; default Bot
+  --brand B              the client brand sent in configuration (minecraft:brand); default none
+  --timer F              cheat, to test an anticheat: tick F times as fast as vanilla's client (1.5: 30 Hz)
   --report FILE          a JSON summary at the end (- prints it after the per-second lines)
 ";
 
 #[derive(Clone, Copy, Debug, PartialEq)]
 enum Behaviour {
     Idle,
+    Stand,
     Walk,
     Explore,
+    FloodMove,
+    FloodAcks,
+    FloodPackets,
+    FloodChunks,
+    FloodUse,
+    FloodClick,
+    FloodSuggest,
+    FloodBook,
+    FloodSign,
+    FloodRecipe,
 }
 
 impl Behaviour {
     fn name(self) -> &'static str {
         match self {
             Self::Idle => "idle",
+            Self::Stand => "stand",
             Self::Walk => "walk",
             Self::Explore => "explore",
+            Self::FloodMove => "flood-move",
+            Self::FloodAcks => "flood-acks",
+            Self::FloodPackets => "flood-packets",
+            Self::FloodChunks => "flood-chunks",
+            Self::FloodUse => "flood-use",
+            Self::FloodClick => "flood-click",
+            Self::FloodSuggest => "flood-suggest",
+            Self::FloodBook => "flood-book",
+            Self::FloodSign => "flood-sign",
+            Self::FloodRecipe => "flood-recipe",
         }
     }
 }
@@ -81,8 +125,17 @@ struct Options {
     view_distance: i8,
     seed: u64,
     explore_speed: f64,
+    /// The player to attack, and how long after joining to start.
+    attack: Option<String>,
+    attack_after: f64,
+    flood: usize,
+    no_read: bool,
     name: String,
+    /// The `minecraft:brand` to send, if any.
+    brand: Option<String>,
     report: Option<String>,
+    /// How many times as fast as vanilla's 20 Hz the bots tick (a timer cheat above 1).
+    timer: f64,
 }
 
 fn options() -> Result<Options, String> {
@@ -96,8 +149,14 @@ fn options() -> Result<Options, String> {
         view_distance: 10,
         seed: 12345,
         explore_speed: 22.0,
+        attack: None,
+        attack_after: 5.0,
+        flood: 100,
+        no_read: false,
         name: "Bot".into(),
         report: None,
+        brand: None,
+        timer: 1.0,
     };
     let mut args = std::env::args().skip(1);
     while let Some(arg) = args.next() {
@@ -105,6 +164,10 @@ fn options() -> Result<Options, String> {
             print!("{HELP}");
             std::process::exit(0);
         }
+        if arg == "--no-read" {
+            o.no_read = true;
+            continue;
+        }
         let value = args.next().ok_or(format!("{arg} needs a value"))?;
         let number = |what: &str| format!("{arg} needs {what}, not {value:?}");
         match arg.as_str() {
@@ -122,14 +185,41 @@ fn options() -> Result<Options, String> {
             "--explore-speed" => {
                 o.explore_speed = value.parse().map_err(|_| number("blocks a second"))?;
             }
+            "--flood" => o.flood = value.parse().map_err(|_| number("packets a tick"))?,
+            "--attack" => o.attack = Some(value),
+            "--attack-after" => o.attack_after = value.parse().map_err(|_| number("seconds"))?,
             "--name" => o.name = value,
             "--report" => o.report = Some(value),
+            "--brand" => o.brand = Some(value),
+            "--timer" => {
+                o.timer = value.parse().map_err(|_| number("a speed, like 1.5"))?;
+                if !(o.timer >= 0.1 && o.timer <= 20.0) {
+                    return Err(format!("--timer {value}: use 0.1 to 20"));
+                }
+            }
             _ => return Err(format!("unknown option {arg}; --help lists them")),
         }
     }
-    if !["idle", "walk", "explore", "mixed"].contains(&o.behaviour.as_str()) {
+    const BEHAVIOURS: [&str; 15] = [
+        "idle",
+        "walk",
+        "explore",
+        "mixed",
+        "stand",
+        "flood-move",
+        "flood-acks",
+        "flood-packets",
+        "flood-chunks",
+        "flood-use",
+        "flood-click",
+        "flood-suggest",
+        "flood-book",
+        "flood-sign",
+        "flood-recipe",
+    ];
+    if !BEHAVIOURS.contains(&o.behaviour.as_str()) {
         return Err(format!(
-            "--behaviour {}: use idle, walk, explore or mixed",
+            "--behaviour {}: use idle, walk, explore, mixed or a flood behaviour (--help lists them)",
             o.behaviour
         ));
     }
@@ -156,6 +246,13 @@ struct Bot {
     teleport: Mutex<Option<[f64; 3]>>,
     error: Mutex<Option<String>>,
     joined_after_ms: AtomicU64,
+    /// The bot stopped reading (--no-read).
+    deaf: AtomicBool,
+    /// `--attack`: the target's UUID and, once AddEntity showed it, its entity id.
+    target: Mutex<(Option<u128>, Option<i32>)>,
+    attacks: AtomicU64,
+    /// The last SetHealth.
+    health: Mutex<Option<f32>>,
 }
 
 /// A small deterministic generator (SplitMix64), so every run moves the bots the same way.
@@ -173,6 +270,11 @@ impl Random {
     }
 }
 
+/// One bot thread that panics poisons the locks it held; the others and the report go on.
+fn lock<T>(m: &Mutex<T>) -> std::sync::MutexGuard<'_, T> {
+    m.lock().unwrap_or_else(std::sync::PoisonError::into_inner)
+}
+
 fn raw(id: i32, write: impl FnOnce(&mut Writer)) -> Vec<u8> {
     let mut w = Writer::new();
     w.varint(id);
@@ -180,6 +282,89 @@ fn raw(id: i32, write: impl FnOnce(&mut Writer)) -> Vec<u8> {
     w.data
 }
 
+/// Item ids of the pinned version (26.3's item registry).
+const STONE: i32 = 1;
+const WRITABLE_BOOK: i32 = 1371;
+
+/// The `i`th packet of a costly flood this tick, the bot at `pos`; none for other behaviours.
+fn costly(
+    behaviour: Behaviour,
+    i: usize,
+    sequence: i32,
+    pos: [f64; 3],
+    random: &mut Random,
+) -> Option<Vec<u8>> {
+    use ids::play::serverbound as sb;
+    static LONG_COMMAND: LazyLock<String> =
+        LazyLock::new(|| format!("/msg {}", "x".repeat(30_000)));
+    static BOOK: LazyLock<Vec<u8>> = LazyLock::new(|| {
+        play::Serverbound::EditBook(play::EditBook {
+            slot: 0,
+            pages: vec!["a".repeat(1024); 100],
+            title: None,
+        })
+        .encode()
+    });
+    let block = pos.map(|v| v.floor() as i32);
+    let packet = match behaviour {
+        Behaviour::FloodUse => {
+            // A block within reach: place stone there, or break what is there.
+            let at = [0, 1, 2].map(|k| block[k] + (random.unit() * 7.0) as i32 - 3);
+            if i % 2 == 0 {
+                play::Serverbound::UseItemOn(play::UseItemOn {
+                    hand: 0,
+                    pos: at,
+                    face: 1,
+                    cursor: [0.5, 1.0, 0.5],
+                    inside: false,
+                    world_border: false,
+                    sequence,
+                })
+            } else {
+                play::Serverbound::PlayerAction(play::PlayerAction {
+                    action: 0,
+                    pos: at,
+                    direction: 1,
+                    sequence,
+                })
+            }
+        }
+        Behaviour::FloodClick => play::Serverbound::ContainerClick(play::ContainerClick {
+            container: 0,
+            state: 0,
+            slot: 36 + (i % 9) as i16,
+            button: 0,
+            input: 0,
+            changed: Vec::new(),
+            carried: None,
+        }),
+        Behaviour::FloodSuggest => {
+            let text = if i % 2 == 0 {
+                "/"
+            } else {
+                LONG_COMMAND.as_str()
+            };
+            return Some(raw(sb::COMMAND_SUGGESTION, |w| {
+                w.varint(sequence);
+                w.string(text);
+            }));
+        }
+        Behaviour::FloodBook => return Some(BOOK.clone()),
+        Behaviour::FloodSign => play::Serverbound::SignUpdate(play::SignUpdate {
+            pos: [block[0], block[1] - 1, block[2]],
+            lines: std::array::from_fn(|_| "a".repeat(384)),
+            front: true,
+        }),
+        Behaviour::FloodRecipe => play::Serverbound::PlaceRecipe(recipes::PlaceRecipe {
+            container: 0,
+            recipe: (i % 2042) as i32,
+            use_max: true,
+        }),
+        _ => return None,
+    };
+    Some(packet.encode())
+}
+
 fn err(e: impl std::fmt::Display) -> String {
     e.to_string()
 }
@@ -247,6 +432,19 @@ fn join(o: &Options, name: &str) -> Result<Connection, String> {
         .encode(),
     )
     .map_err(err)?;
+    // ClientBrandRetriever: vanilla's client says "vanilla", Horizon's "horizon".
+    if let Some(brand) = &o.brand {
+        let mut w = Writer::new();
+        w.string(brand);
+        c.send(
+            &configuration::Serverbound::CustomPayload(configuration::CustomPayload {
+                channel: "minecraft:brand".into(),
+                data: w.data,
+            })
+            .encode(),
+        )
+        .map_err(err)?;
+    }
     loop {
         let (id, body) = c.recv().map_err(err)?;
         let reply = match id {
@@ -274,8 +472,9 @@ fn join(o: &Options, name: &str) -> Result<Connection, String> {
                             payload: None,
                         })
                     }
-                    configuration::Clientbound::Disconnect(_) => {
-                        return Err("disconnected during configuration".into());
+                    configuration::Clientbound::Disconnect(p) => {
+                        let reason = horizon_protocol::text::plain(&p.reason, &Default::default());
+                        return Err(format!("disconnected during configuration: {reason}"));
                     }
                     configuration::Clientbound::FinishConfiguration(_) => {
                         c.send(&configuration::Serverbound::FinishConfiguration(Empty).encode())
@@ -329,16 +528,22 @@ fn read(
 ) {
     use ids::play::clientbound as cb;
     use ids::play::serverbound as sb;
-    let send = |body: Vec<u8>| writer.lock().unwrap().send(&body);
+    let send = |body: Vec<u8>| lock(&writer).send(&body);
     let mut seen = HashSet::new();
     let mut batch = BatchSize::new();
     let mut teleports = 0u64;
     loop {
+        if bot.deaf.load(Ordering::Relaxed) {
+            while bot.online.load(Ordering::SeqCst) {
+                thread::sleep(Duration::from_millis(100));
+            }
+            return;
+        }
         let (id, body) = match reader.recv() {
             Ok(packet) => packet,
             Err(e) => {
                 if bot.online.swap(false, Ordering::SeqCst) {
-                    *bot.error.lock().unwrap() = Some(e.to_string());
+                    *lock(&bot.error) = Some(e.to_string());
                 }
                 return;
             }
@@ -356,7 +561,7 @@ fn read(
             cb::LEVEL_CHUNK_WITH_LIGHT => {
                 bot.chunks.fetch_add(1, Ordering::Relaxed);
                 if let (Ok(x), Ok(z)) = (r.i32(), r.i32()) {
-                    if !bot.held.lock().unwrap().insert((x, z)) {
+                    if !lock(&bot.held).insert((x, z)) {
                         bot.resent.fetch_add(1, Ordering::Relaxed);
                     }
                     if seen.insert((x, z)) {
@@ -368,12 +573,27 @@ fn read(
             cb::FORGET_LEVEL_CHUNK => {
                 if let Ok(play::Clientbound::ForgetLevelChunk(p)) =
                     play::Clientbound::decode(id, &body)
-                    && bot.held.lock().unwrap().remove(&(p.pos[0], p.pos[1]))
+                    && lock(&bot.held).remove(&(p.pos[0], p.pos[1]))
                 {
                     bot.forgotten.fetch_add(1, Ordering::Relaxed);
                 }
                 Ok(())
             }
+            cb::ADD_ENTITY => {
+                if let Ok(play::Clientbound::AddEntity(p)) = play::Clientbound::decode(id, &body) {
+                    let mut target = lock(&bot.target);
+                    if target.0 == Some(p.uuid) {
+                        target.1 = Some(p.id);
+                    }
+                }
+                Ok(())
+            }
+            cb::SET_HEALTH => {
+                if let Ok(play::Clientbound::SetHealth(p)) = play::Clientbound::decode(id, &body) {
+                    *lock(&bot.health) = Some(p.health);
+                }
+                Ok(())
+            }
             cb::CHUNK_BATCH_START => {
                 batch.started = Instant::now();
                 Ok(())
@@ -389,7 +609,7 @@ fn read(
             }
             cb::PLAYER_POSITION => match play::Clientbound::decode(id, &body) {
                 Ok(play::Clientbound::PlayerPosition(p)) => {
-                    let mut at = bot.teleport.lock().unwrap();
+                    let mut at = lock(&bot.teleport);
                     let previous = at.unwrap_or([0.0; 3]);
                     // Relative flags: X 1, Y 2, Z 4.
                     let pos: [f64; 3] = std::array::from_fn(|i| {
@@ -420,7 +640,7 @@ fn read(
             },
             cb::DISCONNECT | cb::START_CONFIGURATION => {
                 bot.online.store(false, Ordering::SeqCst);
-                *bot.error.lock().unwrap() = Some(if id == cb::DISCONNECT {
+                *lock(&bot.error) = Some(if id == cb::DISCONNECT {
                     format!(
                         "disconnected: {}",
                         String::from_utf8_lossy(&body)
@@ -455,12 +675,13 @@ fn run_bot(
     let connection = match join(&o, &name) {
         Ok(c) => c,
         Err(e) => {
-            *bot.error.lock().unwrap() = Some(e);
+            *lock(&bot.error) = Some(e);
             return;
         }
     };
     let (reader, writer) = connection.split();
     let writer = Arc::new(Mutex::new(writer));
+    lock(&bot.target).0 = o.attack.as_deref().map(offline_uuid);
     bot.online.store(true, Ordering::SeqCst);
     {
         let (writer, bot) = (writer.clone(), bot.clone());
@@ -469,12 +690,12 @@ fn run_bot(
     use ids::play::serverbound as sb;
     // Wait for the spawn position.
     let spawn = loop {
-        if let Some(at) = *bot.teleport.lock().unwrap() {
+        if let Some(at) = *lock(&bot.teleport) {
             break at;
         }
         if !bot.online.load(Ordering::SeqCst) || asked.elapsed() > Duration::from_secs(60) {
-            if bot.error.lock().unwrap().is_none() {
-                *bot.error.lock().unwrap() = Some("no spawn position within 60 s".into());
+            if lock(&bot.error).is_none() {
+                *lock(&bot.error) = Some("no spawn position within 60 s".into());
             }
             return;
         }
@@ -482,32 +703,82 @@ fn run_bot(
     };
     bot.joined_after_ms
         .store(asked.elapsed().as_millis() as u64, Ordering::SeqCst);
-    let send = |body: Vec<u8>| writer.lock().unwrap().send(&body).is_ok();
+    let send = |body: Vec<u8>| lock(&writer).send(&body).is_ok();
     send(raw(sb::PLAYER_LOADED, |_| {}));
+    bot.deaf.store(o.no_read, Ordering::Relaxed);
+    // What the costly floods need in hand (creative: the server takes the bot's word for it).
+    let tool = match behaviour {
+        Behaviour::FloodUse => Some(Stack::new(STONE, 64)),
+        Behaviour::FloodBook => Some(Stack::new(WRITABLE_BOOK, 1)),
+        _ => None,
+    };
+    if tool.is_some() {
+        send(
+            play::Serverbound::SetCreativeModeSlot(play::SetCreativeModeSlot {
+                slot: 36,
+                item: tool,
+            })
+            .encode(),
+        );
+        send(play::Serverbound::SetCarriedItem(play::SetCarriedItem { slot: 0 }).encode());
+    }
+    let mut sequence = 0;
     let mut random = Random(o.seed ^ (index as u64).wrapping_mul(0x2545_F491_4F6C_DD1D));
     let mut pos = spawn;
     let cruise = spawn[1] + 24.0;
     let heading = random.unit() * std::f64::consts::TAU;
     let mut target = pos;
     let mut next = Instant::now();
+    let (joined, mut tick) = (Instant::now(), 0u64);
     loop {
-        if until.lock().unwrap().is_some_and(|u| Instant::now() >= u)
-            || !bot.online.load(Ordering::SeqCst)
-        {
+        if lock(&until).is_some_and(|u| Instant::now() >= u) || !bot.online.load(Ordering::SeqCst) {
             break;
         }
         // A teleport from the server wins over where the bot thought it was.
-        if let Some(at) = bot.teleport.lock().unwrap().take() {
+        if let Some(at) = lock(&bot.teleport).take() {
             pos = at;
         }
         let here = ((pos[0].floor() as i32) >> 4, (pos[2].floor() as i32) >> 4);
-        if !bot.held.lock().unwrap().contains(&here) {
+        // The abusive client doesn't wait for its chunk, as a real client must.
+        if behaviour == Behaviour::Stand {
+            // Where the server put it, on the ground.
+        } else if behaviour == Behaviour::FloodMove {
+            // The last of these moves goes out below, with the tick's end.
+            pos[1] = cruise;
+            for _ in 1..o.flood.max(1) {
+                let angle = random.unit() * std::f64::consts::TAU;
+                let reach = 64.0 + random.unit() * 192.0;
+                pos[0] += angle.cos() * reach;
+                pos[2] += angle.sin() * reach;
+                send(
+                    play::Serverbound::MovePlayerPos(play::MovePlayerPos {
+                        x: pos[0],
+                        y: pos[1],
+                        z: pos[2],
+                        flags: 0,
+                    })
+                    .encode(),
+                );
+            }
+            let angle = random.unit() * std::f64::consts::TAU;
+            pos[0] += angle.cos() * 128.0;
+            pos[2] += angle.sin() * 128.0;
+        } else if behaviour == Behaviour::FloodChunks {
+            // Up to cruising height first, then just under the server's 10 blocks a tick:
+            // every tick asks for new chunks.
+            if pos[1] < cruise {
+                pos[1] = (pos[1] + 0.5).min(cruise);
+            } else {
+                pos[0] += heading.cos() * 9.9;
+                pos[2] += heading.sin() * 9.9;
+            }
+        } else if !lock(&bot.held).contains(&here) {
             bot.waited.fetch_add(1, Ordering::Relaxed);
         } else if pos[1] < cruise {
             pos[1] = (pos[1] + 0.5).min(cruise);
         } else {
             match behaviour {
-                Behaviour::Idle => {}
+                Behaviour::Idle | Behaviour::Stand => {}
                 Behaviour::Walk => {
                     let (dx, dz) = (target[0] - pos[0], target[2] - pos[2]);
                     let distance = dx.hypot(dz);
@@ -526,7 +797,37 @@ fn run_bot(
                         pos[2] += dz / distance * step;
                     }
                 }
-                Behaviour::Explore => {
+                Behaviour::FloodMove
+                | Behaviour::FloodChunks
+                | Behaviour::FloodUse
+                | Behaviour::FloodClick
+                | Behaviour::FloodSuggest
+                | Behaviour::FloodBook
+                | Behaviour::FloodSign
+                | Behaviour::FloodRecipe => {}
+                Behaviour::FloodPackets => {
+                    for i in 0..o.flood {
+                        send(
+                            play::Serverbound::MovePlayerRot(play::MovePlayerRot {
+                                yaw: (i % 360) as f32,
+                                pitch: 0.0,
+                                flags: 0,
+                            })
+                            .encode(),
+                        );
+                    }
+                }
+                Behaviour::FloodAcks | Behaviour::Explore => {
+                    if behaviour == Behaviour::FloodAcks {
+                        for _ in 0..o.flood {
+                            send(
+                                play::Serverbound::ChunkBatchReceived(play::ChunkBatchReceived {
+                                    chunks_per_tick: 64.0,
+                                })
+                                .encode(),
+                            );
+                        }
+                    }
                     // Flying in creative, by default about 22 blocks a second, which keeps new
                     // chunks coming as fast as the server sends them.
                     let step = o.explore_speed / 20.0;
@@ -535,12 +836,28 @@ fn run_bot(
                 }
             }
         }
+        // The costly floods go out wherever the bot is, chunks or not (--no-read gets none).
+        for i in 0..o.flood {
+            sequence += 1;
+            if let Some(body) = costly(behaviour, i, sequence, pos, &mut random) {
+                send(body);
+            }
+        }
+        let target = lock(&bot.target).1;
+        if let Some(id) = target
+            && joined.elapsed().as_secs_f64() >= o.attack_after
+            && tick % 10 == 0
+        {
+            send(play::Serverbound::Attack(play::Attack { id }).encode());
+            bot.attacks.fetch_add(1, Ordering::Relaxed);
+        }
+        tick += 1;
         let ok = send(
             play::Serverbound::MovePlayerPos(play::MovePlayerPos {
                 x: pos[0],
                 y: pos[1],
                 z: pos[2],
-                flags: 0,
+                flags: u8::from(behaviour == Behaviour::Stand),
             })
             .encode(),
         ) && send(raw(sb::CLIENT_TICK_END, |_| {}));
@@ -548,7 +865,7 @@ fn run_bot(
             bot.online.store(false, Ordering::SeqCst);
             break;
         }
-        next += Duration::from_millis(50);
+        next += Duration::from_secs_f64(0.05 / o.timer);
         let now = Instant::now();
         if next > now {
             thread::sleep(next - now);
@@ -558,14 +875,25 @@ fn run_bot(
     }
     // Offline first, so the reader doesn't count the closed connection as a failure.
     bot.online.store(false, Ordering::SeqCst);
-    writer.lock().unwrap().shutdown();
+    lock(&writer).shutdown();
 }
 
 fn behaviour_of(mode: &str, index: usize) -> Behaviour {
     match mode {
         "idle" => Behaviour::Idle,
+        "stand" => Behaviour::Stand,
         "walk" => Behaviour::Walk,
         "explore" => Behaviour::Explore,
+        "flood-move" => Behaviour::FloodMove,
+        "flood-acks" => Behaviour::FloodAcks,
+        "flood-packets" => Behaviour::FloodPackets,
+        "flood-chunks" => Behaviour::FloodChunks,
+        "flood-use" => Behaviour::FloodUse,
+        "flood-click" => Behaviour::FloodClick,
+        "flood-suggest" => Behaviour::FloodSuggest,
+        "flood-book" => Behaviour::FloodBook,
+        "flood-sign" => Behaviour::FloodSign,
+        "flood-recipe" => Behaviour::FloodRecipe,
         // mixed: of every five bots, three walk, one explores, one stands.
         _ => match index % 5 {
             0 | 2 | 4 => Behaviour::Walk,
@@ -612,13 +940,10 @@ fn main() {
         let total = |f: fn(&Bot) -> &AtomicU64| -> u64 {
             bots.iter().map(|b| f(b).load(Ordering::Relaxed)).sum()
         };
-        let failed = bots
-            .iter()
-            .filter(|b| b.error.lock().unwrap().is_some())
-            .count();
+        let failed = bots.iter().filter(|b| lock(&b.error).is_some()).count();
         if first.is_none() && online > 0 {
             first = Some(Instant::now());
-            *until.lock().unwrap() = Some(Instant::now() + Duration::from_secs(o.seconds));
+            *lock(&until) = Some(Instant::now() + Duration::from_secs(o.seconds));
         }
         println!(
             "{}",
@@ -636,10 +961,10 @@ fn main() {
             })
         );
         previous_chunks = chunks;
-        let over = until.lock().unwrap().is_some_and(|u| Instant::now() >= u);
+        let over = lock(&until).is_some_and(|u| Instant::now() >= u);
         let all_failed = failed == o.bots;
         if over || all_failed || (first.is_none() && start.elapsed() > Duration::from_secs(120)) {
-            *until.lock().unwrap() = Some(Instant::now());
+            *lock(&until) = Some(Instant::now());
             break;
         }
     }
@@ -669,7 +994,9 @@ fn main() {
             "forgotten": b.forgotten.load(Ordering::Relaxed),
             "pulled_back": b.pulled_back.load(Ordering::Relaxed),
             "waited_ticks": b.waited.load(Ordering::Relaxed),
-            "error": *b.error.lock().unwrap(),
+            "error": *lock(&b.error),
+            "attacks": b.attacks.load(Ordering::Relaxed),
+            "health": *lock(&b.health),
         })).collect::<Vec<_>>(),
     });
     if o.report.as_deref() == Some("-") {

crates/horizon-client-core/Cargo.toml

@@ -0,0 +1,14 @@
+[package]
+name = "horizon-client-core"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+rust-version = "1.90"
+description = "The client's lowest layer: chat text and translations, SNBT and NBT paths, the scoreboard, boss bars, game rules and the registry and particle tables commands name"
+
+[dependencies]
+horizon-world = { path = "../horizon-world" }
+serde_json = { version = "1.0.151", features = ["raw_value"] }
+
+[lints]
+workspace = true

crates/horizon-client-core/src/block_entity_nbt.rs

@@ -61,6 +61,16 @@ fn f32_tag(v: f32) -> Tag {
     Tag::Float(v.to_bits())
 }
 
+/// `TheEndGatewayBlockEntity.loadAdditional`: BlockPos.CODEC and Level.isInSpawnableBounds.
+pub fn gateway_exit(tag: &Tag) -> Option<[i32; 3]> {
+    let Tag::IntArray(v) = tag else { return None };
+    let p: [i32; 3] = v.as_slice().try_into().ok()?;
+    ((-30_000_000..30_000_000).contains(&p[0])
+        && (-20_000_000..20_000_000).contains(&p[1])
+        && (-30_000_000..30_000_000).contains(&p[2]))
+    .then_some(p)
+}
+
 /// What a block entity reads and writes, in `saveAdditional` order.
 struct Fields<'a> {
     input: &'a Tag,
@@ -259,7 +269,7 @@ fn is_pos(tag: &Tag) -> bool {
     matches!(tag, Tag::IntArray(v) if v.len() == 3)
 }
 /// The loaded `SignText` of one side, or the empty text.
-pub(crate) fn sign_side(tag: Option<&Tag>) -> Tag {
+pub fn sign_side(tag: Option<&Tag>) -> Tag {
     let empty = || string("");
     let mut messages: Vec<Tag> = match tag.and_then(|t| t.get("messages")) {
         Some(Tag::List(list)) => list.iter().filter_map(component).collect(),
@@ -424,10 +434,7 @@ pub fn canonical(tag: &Tag) -> Option<Tag> {
         }
         "minecraft:end_gateway" => {
             f.long("Age", 0);
-            f.keep("exit_portal", |t| {
-                is_pos(t)
-                    && matches!(t, Tag::IntArray(v) if v[1].abs() <= 30_000_000 && v[0].abs() <= 30_000_000 && v[2].abs() <= 30_000_000)
-            });
+            f.keep("exit_portal", |t| gateway_exit(t).is_some());
             if flag(tag.get("ExactTeleport")) == Some(true) {
                 f.put("ExactTeleport", boolean(true));
             }
@@ -487,7 +494,11 @@ pub fn canonical(tag: &Tag) -> Option<Tag> {
                     _ => string("minecraft:air"),
                 },
             );
-            f.put("facing", Tag::Int(int(tag.get("facing")).unwrap_or(0)));
+            // Direction.LEGACY_ID_CODEC: the 3D data value as a byte.
+            f.put(
+                "facing",
+                Tag::Byte(int(tag.get("facing")).unwrap_or(0) as i8),
+            );
             f.float("progress", 0.0);
             f.flag("extending", false);
             f.flag("source", false);
@@ -664,7 +675,9 @@ pub fn canonical(tag: &Tag) -> Option<Tag> {
         }
         "minecraft:trial_spawner" => {
             // `TrialSpawnerStateData.Packed` and `FullConfig`: every key is optional
-            // and defaulted by vanilla; they are kept as loaded.
+            // and defaulted by vanilla; they are kept as loaded. No `spawn_data` is
+            // added: an absent one loads as Optional.empty and is not stored, and
+            // an empty entity would keep the spawner from ever picking a mob.
             if let Tag::Compound(c) = tag {
                 for (k, v) in c {
                     let key = k.to_string_lossy();
@@ -676,12 +689,6 @@ pub fn canonical(tag: &Tag) -> Option<Tag> {
                     }
                 }
             }
-            if !f.out.contains_key(&"spawn_data".into()) {
-                f.put(
-                    "spawn_data",
-                    Tag::compound([("entity", Tag::Compound(Compound::new()))]),
-                );
-            }
         }
         "minecraft:vault" => {
             // `VaultConfig.DEFAULT` (when the config is absent): the trial key and the
@@ -827,6 +834,21 @@ mod tests {
         canonical(&snbt(s)).expect("known type")
     }
 
+    #[test]
+    fn a_trial_spawner_without_spawn_data_saves_none() {
+        let fresh = canon(
+            r#"{id:"minecraft:trial_spawner",x:1,y:2,z:3,normal_config:"minecraft:trial_chamber/ranged/skeleton/normal"}"#,
+        );
+        assert_eq!(fresh.get("spawn_data"), None);
+        let picked = canon(
+            r#"{id:"minecraft:trial_spawner",x:1,y:2,z:3,spawn_data:{entity:{id:"minecraft:skeleton"}}}"#,
+        );
+        assert_eq!(
+            picked.get("spawn_data"),
+            Some(&snbt(r#"{entity:{id:"minecraft:skeleton"}}"#))
+        );
+    }
+
     #[test]
     fn every_type_has_defaults() {
         for id in TYPES.iter().chain(NEWEST.iter()) {
@@ -855,6 +877,23 @@ mod tests {
         );
     }
 
+    /// `PistonMovingBlockEntity.saveAdditional`: `facing` through
+    /// `Direction.LEGACY_ID_CODEC` (a byte), `progress` a float.
+    #[test]
+    fn moving_piston_fields_match_vanilla() {
+        let out = canon(
+            "{id:\"minecraft:piston\",x:1,y:2,z:3,blockState:{Name:\"minecraft:stone\"},\
+             facing:5,progress:0.5f,extending:1b,source:0b}",
+        );
+        assert_eq!(out.get("facing"), Some(&Tag::Byte(5)));
+        assert_eq!(out.get("progress"), Some(&f32_tag(0.5)));
+        assert_eq!(out.get("extending"), Some(&Tag::Byte(1)));
+        assert_eq!(out.get("source"), Some(&Tag::Byte(0)));
+        let fresh = canon("{id:\"minecraft:piston\",x:1,y:2,z:3}");
+        assert_eq!(fresh.get("facing"), Some(&Tag::Byte(0)));
+        assert_eq!(fresh.get("blockState"), Some(&string("minecraft:air")));
+    }
+
     #[test]
     fn loot_table_replaces_items_and_zero_seed_is_omitted() {
         let out = canon(

crates/horizon-client-core/src/bossbar.rs

@@ -14,40 +14,64 @@ pub const STYLES: [&str; 5] = [
     "notched_12",
     "notched_20",
 ];
-/// `BossBarColor.getFormatting`.
+/// `BossBarColor.getFormatting`. Purple is dark blue in 26.3.
 pub fn color_rgb(color: &str) -> u32 {
     let name = match color {
         "pink" => "red",
         "red" => "dark_red",
-        "purple" => "dark_purple",
+        "purple" => "dark_blue",
         other => other,
     };
     text::named_color(name).unwrap_or(text::WHITE)
 }
 
+/// A version-4 shaped id from a resource id. Saved boss events do not keep
+/// their UUID (`CustomBossEvents` mints a new one on load).
+pub fn stable_uuid(id: &str) -> u128 {
+    let mut h = 0xcbf29ce484222325u64;
+    for b in id.as_bytes() {
+        h ^= u64::from(*b);
+        h = h.wrapping_mul(0x100000001b3);
+    }
+    let most = (h as i64) & -61441 | 16384;
+    let least = (h.rotate_left(17) as i64) & 4_611_686_018_427_387_903 | i64::MIN;
+    ((most as u64 as u128) << 64) | (least as u64 as u128)
+}
+
 #[derive(Clone, Debug, PartialEq)]
 pub struct BossBar {
     pub id: String,
+    /// The `ServerBossEvent` UUID. Not saved.
+    pub uuid: u128,
     pub name: Comp,
     pub color: String,
     pub style: String,
     pub value: i32,
     pub max: i32,
+    /// `ServerBossEvent.visible`. A new bar is visible; nobody sees it until
+    /// a player is added.
     pub visible: bool,
-    /// Whether the (single) local player is in the bar's player set.
-    pub player: bool,
+    pub darken: bool,
+    pub music: bool,
+    pub fog: bool,
+    /// `CustomBossEvent.players`, the UUIDs told about the bar.
+    pub players: Vec<[i32; 4]>,
 }
 impl BossBar {
     pub fn new(id: &str, name: Comp) -> Self {
         Self {
             id: id.to_owned(),
+            uuid: stable_uuid(id),
             name,
             color: "white".into(),
             style: "progress".into(),
             value: 0,
             max: 100,
             visible: true,
-            player: false,
+            darken: false,
+            music: false,
+            fog: false,
+            players: Vec::new(),
         }
     }
     /// `CustomBossEvent.getDisplayName`.
@@ -91,31 +115,34 @@ impl BossBars {
     pub fn ids(&self) -> Vec<String> {
         self.bars.iter().map(|b| b.id.clone()).collect()
     }
-    /// The saved compound; the player's UUID stands for "the local player".
-    pub fn pack(&self, player: Option<[i32; 4]>) -> Tag {
+    /// The saved compound (`CustomBossEvent.Packed`).
+    pub fn pack(&self) -> Tag {
         let mut c = Compound::new();
         for b in &self.bars {
-            let mut e = vec![
-                ("Name", json_to_tag(&b.name)),
-                ("Visible", Tag::Byte(i8::from(b.visible))),
-                ("Value", Tag::Int(b.value)),
-                ("Max", Tag::Int(b.max)),
-                ("Color", Tag::String(b.color.as_str().into())),
-                ("Overlay", Tag::String(b.style.as_str().into())),
-                ("DarkenScreen", Tag::Byte(0)),
-                ("PlayBossMusic", Tag::Byte(0)),
-                ("CreateWorldFog", Tag::Byte(0)),
-            ];
-            let players = match (b.player, player) {
-                (true, Some(u)) => vec![Tag::IntArray(u.to_vec())],
-                _ => Vec::new(),
-            };
-            e.push(("Players", Tag::List(players)));
-            c.insert(b.id.as_str().into(), Tag::compound(e));
+            let players = b
+                .players
+                .iter()
+                .map(|u| Tag::IntArray(u.to_vec()))
+                .collect();
+            c.insert(
+                b.id.as_str().into(),
+                Tag::compound([
+                    ("Name", json_to_tag(&b.name)),
+                    ("Visible", Tag::Byte(i8::from(b.visible))),
+                    ("Value", Tag::Int(b.value)),
+                    ("Max", Tag::Int(b.max)),
+                    ("Color", Tag::String(b.color.as_str().into())),
+                    ("Overlay", Tag::String(b.style.as_str().into())),
+                    ("DarkenScreen", Tag::Byte(i8::from(b.darken))),
+                    ("PlayBossMusic", Tag::Byte(i8::from(b.music))),
+                    ("CreateWorldFog", Tag::Byte(i8::from(b.fog))),
+                    ("Players", Tag::List(players)),
+                ]),
+            );
         }
         Tag::Compound(c)
     }
-    pub fn unpack(data: &Tag, player: Option<[i32; 4]>) -> Self {
+    pub fn unpack(data: &Tag) -> Self {
         let mut bars = Vec::new();
         if let Tag::Compound(c) = data {
             for (id, e) in c {
@@ -130,21 +157,30 @@ impl BossBars {
                     Some(Tag::Byte(v)) => i32::from(*v),
                     _ => d,
                 };
-                let in_players = match (get("Players"), player) {
-                    (Some(Tag::List(l)), Some(u)) => l
+                let players = match get("Players") {
+                    Some(Tag::List(l)) => l
                         .iter()
-                        .any(|t| matches!(t, Tag::IntArray(a) if a.as_slice() == u)),
-                    _ => false,
+                        .filter_map(|t| match t {
+                            Tag::IntArray(a) if a.len() == 4 => Some([a[0], a[1], a[2], a[3]]),
+                            _ => None,
+                        })
+                        .collect(),
+                    _ => Vec::new(),
                 };
+                let id = id.to_string_lossy();
                 bars.push(BossBar {
-                    id: id.to_string_lossy(),
+                    uuid: stable_uuid(&id),
+                    id,
                     name: get("Name").map_or_else(|| literal(""), tag_to_json),
                     color: text("Color", "white"),
                     style: text("Overlay", "progress"),
                     value: num("Value", 0),
                     max: num("Max", 100),
                     visible: num("Visible", 0) != 0,
-                    player: in_players,
+                    darken: num("DarkenScreen", 0) != 0,
+                    music: num("PlayBossMusic", 0) != 0,
+                    fog: num("CreateWorldFog", 0) != 0,
+                    players,
                 });
             }
         }
@@ -167,17 +203,15 @@ mod tests {
         bar.value = 25;
         bar.max = 50;
         bar.visible = true;
-        bar.player = true;
-        let uuid = Some([1, 2, 3, 4]);
-        let back = BossBars::unpack(&b.pack(uuid), uuid);
+        bar.darken = true;
+        bar.players = vec![[1, 2, 3, 4]];
+        let back = BossBars::unpack(&b.pack());
         assert_eq!(back, b);
-        // Another player's UUID does not include the local player.
-        assert!(!BossBars::unpack(&b.pack(uuid), Some([9, 9, 9, 9])).bars[0].player);
         let bar = b.get("test:x").unwrap();
         assert_eq!(bar.progress(), 0.5);
         assert_eq!(bar.display_name().plain(), "chat.square_brackets");
         assert_eq!(color_rgb("pink"), text::RED);
-        assert_eq!(color_rgb("purple"), 0xAA00AA);
+        assert_eq!(color_rgb("purple"), text::named_color("dark_blue").unwrap());
         b.remove("test:x");
         assert!(b.bars.is_empty());
     }

crates/horizon-client-core/src/component.rs

@@ -0,0 +1,552 @@
+//! Text components from commands: `ComponentArgument` reads an SNBT (or JSON)
+//! value, `ComponentSerialization` turns it into styled text.
+use crate::text::{InlineObject, Style, Text, named_color};
+use horizon_world::nbt::Tag;
+use serde_json::{Map, Value};
+
+/// `SnbtGrammar`, enough for components: compounds, lists, quoted and
+/// unquoted strings, numbers (with type suffixes) and booleans. Returns the
+/// value and the bytes consumed.
+pub fn parse_snbt(input: &str) -> Result<(Value, usize), String> {
+    let mut p = Parser {
+        s: input.as_bytes(),
+        i: 0,
+        depth: 0,
+    };
+    let v = p.value()?;
+    Ok((v, p.i))
+}
+/// Nesting deeper than NBT's own limit (`NbtAccounter`'s 512) is refused
+/// rather than overflowing the stack.
+const SNBT_MAX_DEPTH: usize = 512;
+struct Parser<'a> {
+    s: &'a [u8],
+    i: usize,
+    depth: usize,
+}
+impl Parser<'_> {
+    fn ws(&mut self) {
+        while self.i < self.s.len() && self.s[self.i].is_ascii_whitespace() {
+            self.i += 1;
+        }
+    }
+    fn peek(&self) -> Option<u8> {
+        self.s.get(self.i).copied()
+    }
+    fn expect(&mut self, c: u8) -> Result<(), String> {
+        self.ws();
+        if self.peek() == Some(c) {
+            self.i += 1;
+            Ok(())
+        } else {
+            Err(format!("expected '{}'", c as char))
+        }
+    }
+    fn value(&mut self) -> Result<Value, String> {
+        self.ws();
+        match self.peek() {
+            Some(b'{') => {
+                if self.depth >= SNBT_MAX_DEPTH {
+                    return Err(format!("tag nesting too deep at {}", self.i));
+                }
+                self.depth += 1;
+                let v = self.object();
+                self.depth -= 1;
+                v
+            }
+            Some(b'[') => {
+                if self.depth >= SNBT_MAX_DEPTH {
+                    return Err(format!("tag nesting too deep at {}", self.i));
+                }
+                self.depth += 1;
+                let v = self.array();
+                self.depth -= 1;
+                v
+            }
+            Some(b'"' | b'\'') => Ok(Value::String(self.string()?)),
+            Some(_) => {
+                let word = self.unquoted();
+                if word.is_empty() {
+                    return Err("expected a value".into());
+                }
+                Ok(match word.as_str() {
+                    "true" => Value::Bool(true),
+                    "false" => Value::Bool(false),
+                    _ => {
+                        let digits = word
+                            .trim_end_matches(['b', 'B', 's', 'S', 'l', 'L', 'f', 'F', 'd', 'D']);
+                        // Only digits (and an exponent) make a number: `nan`
+                        // or `Infinity`, which Rust's parse would take, stays
+                        // a string.
+                        if digits
+                            .bytes()
+                            .any(|c| c.is_ascii_alphabetic() && c != b'e' && c != b'E')
+                        {
+                            Value::String(word)
+                        } else {
+                            match (digits.parse::<i64>(), digits.parse::<f64>()) {
+                                (Ok(n), _) if digits.len() + 1 >= word.len() => Value::from(n),
+                                (_, Ok(f)) if digits.len() + 1 >= word.len() => Value::from(f),
+                                _ => Value::String(word),
+                            }
+                        }
+                    }
+                })
+            }
+            None => Err("expected a value".into()),
+        }
+    }
+    fn object(&mut self) -> Result<Value, String> {
+        self.i += 1;
+        let mut map = Map::new();
+        self.ws();
+        if self.peek() == Some(b'}') {
+            self.i += 1;
+            return Ok(Value::Object(map));
+        }
+        loop {
+            self.ws();
+            let key = self.string()?;
+            self.expect(b':')?;
+            map.insert(key, self.value()?);
+            self.ws();
+            match self.peek() {
+                Some(b',') => self.i += 1,
+                Some(b'}') => {
+                    self.i += 1;
+                    return Ok(Value::Object(map));
+                }
+                _ => return Err("expected ',' or '}'".into()),
+            }
+        }
+    }
+    fn array(&mut self) -> Result<Value, String> {
+        self.i += 1;
+        let mut list = Vec::new();
+        self.ws();
+        // Typed arrays [B;...], [I;...], [L;...].
+        if matches!(
+            self.s.get(self.i..self.i + 2),
+            Some([b'B' | b'I' | b'L', b';'])
+        ) {
+            self.i += 2;
+        }
+        self.ws();
+        if self.peek() == Some(b']') {
+            self.i += 1;
+            return Ok(Value::Array(list));
+        }
+        loop {
+            list.push(self.value()?);
+            self.ws();
+            match self.peek() {
+                Some(b',') => self.i += 1,
+                Some(b']') => {
+                    self.i += 1;
+                    return Ok(Value::Array(list));
+                }
+                _ => return Err("expected ',' or ']'".into()),
+            }
+        }
+    }
+    fn unquoted(&mut self) -> String {
+        let start = self.i;
+        while let Some(c) = self.peek() {
+            if c.is_ascii_alphanumeric() || matches!(c, b'_' | b'-' | b'.' | b'+') {
+                self.i += 1;
+            } else {
+                break;
+            }
+        }
+        String::from_utf8_lossy(&self.s[start..self.i]).into_owned()
+    }
+    fn string(&mut self) -> Result<String, String> {
+        self.ws();
+        let Some(q @ (b'"' | b'\'')) = self.peek() else {
+            return Ok(self.unquoted());
+        };
+        self.i += 1;
+        let mut out = Vec::new();
+        while let Some(c) = self.peek() {
+            self.i += 1;
+            match c {
+                b'\\' => {
+                    let Some(e) = self.peek() else { break };
+                    self.i += 1;
+                    out.push(match e {
+                        b'n' => b'\n',
+                        b't' => b'\t',
+                        other => other,
+                    });
+                }
+                c if c == q => return Ok(String::from_utf8_lossy(&out).into_owned()),
+                c => out.push(c),
+            }
+        }
+        Err("unterminated string".into())
+    }
+}
+/// The style fields of a component object.
+fn object_style(o: &serde_json::Map<String, Value>) -> Style {
+    let mut style = Style::default();
+    if let Some(c) = o.get("color").and_then(Value::as_str) {
+        style.color = named_color(c).or_else(|| {
+            c.strip_prefix('#')
+                .and_then(|h| u32::from_str_radix(h, 16).ok())
+        });
+    }
+    style.shadow_color = o.get("shadow_color").and_then(shadow_color);
+    let flag = |k: &str| o.get(k).and_then(Value::as_bool);
+    style.bold = flag("bold");
+    style.italic = flag("italic");
+    style.underlined = flag("underlined");
+    style.strikethrough = flag("strikethrough");
+    style.obfuscated = flag("obfuscated");
+    style.font = o.get("font").and_then(crate::text::font_id);
+    // ClickEvent.CODEC: the actions a chat line acts on here. A component
+    // from a server never opens a file.
+    if let Some(e) = o.get("click_event").and_then(Value::as_object) {
+        let text = |k: &str| e.get(k).and_then(Value::as_str).map(str::to_owned);
+        style.click = match e.get("action").and_then(Value::as_str) {
+            // ClickEvent.OpenUrl.CODEC: ExtraCodecs.UNTRUSTED_URI allows http and
+            // https only, the scheme in any case (Util.parseAndValidateUntrustedUri).
+            Some("open_url") => text("url")
+                .filter(|u| {
+                    u.split_once(':').is_some_and(|(scheme, _)| {
+                        scheme.eq_ignore_ascii_case("http") || scheme.eq_ignore_ascii_case("https")
+                    })
+                })
+                .map(crate::text::ClickEvent::OpenUrl),
+            // ClickEvent.ChangePage.CODEC: ExtraCodecs.POSITIVE_INT.
+            Some("change_page") => e
+                .get("page")
+                .and_then(Value::as_i64)
+                .and_then(|p| i32::try_from(p).ok())
+                .filter(|p| *p >= 1)
+                .map(crate::text::ClickEvent::ChangePage),
+            Some("suggest_command") => text("command").map(crate::text::ClickEvent::SuggestCommand),
+            Some("run_command") => text("command").map(crate::text::ClickEvent::RunCommand),
+            Some("copy_to_clipboard") => {
+                text("value").map(crate::text::ClickEvent::CopyToClipboard)
+            }
+            // ClickEvent.ShowDialog.CODEC: a `minecraft:dialog` registry id or
+            // the dialog itself; the server may send it (isAllowedFromServer).
+            Some("show_dialog") => e.get("dialog").map(|dialog| {
+                crate::text::ClickEvent::ShowDialog(crate::scoreboard::json_to_tag(dialog))
+            }),
+            _ => None,
+        };
+    }
+    // HoverEvent.ShowText, ShowItem and ShowEntity.
+    if let Some(e) = o.get("hover_event").and_then(Value::as_object) {
+        match e.get("action").and_then(Value::as_str) {
+            Some("show_text") => {
+                if let Some(value) = e.get("value") {
+                    style.hover = Some(Box::new(to_text(value, &mut |s| Text::literal(s))));
+                }
+            }
+            Some("show_item") if e.get("id").is_some_and(Value::is_string) => {
+                style.hover_item = Some(Box::new(Value::Object(e.clone())));
+            }
+            Some("show_entity") if e.get("id").is_some_and(Value::is_string) => {
+                style.hover_entity = Some(Box::new(Value::Object(e.clone())));
+            }
+            _ => {}
+        }
+    }
+    style.insertion = o
+        .get("insertion")
+        .and_then(Value::as_str)
+        .map(str::to_owned);
+    style
+}
+
+/// `Style.shadow_color`: a packed ARGB int or normalized RGBA array.
+pub(crate) fn shadow_color(value: &Value) -> Option<u32> {
+    if let Some(packed) = value.as_i64() {
+        return i32::try_from(packed).ok().map(|n| n as u32);
+    }
+    let rgba = value.as_array()?;
+    if rgba.len() != 4 {
+        return None;
+    }
+    let channels = rgba
+        .iter()
+        .map(|channel| {
+            // ExtraCodecs.ARGB_COLOR_CODEC reads floats; ARGB.as8BitChannel
+            // floors each normalized channel multiplied by 255.
+            let value = channel.as_f64()? as f32;
+            (value.is_finite() && (0.0..=1.0).contains(&value))
+                .then_some((value * 255.0_f32).floor() as u32)
+        })
+        .collect::<Option<Vec<_>>>()?;
+    Some(channels[3] << 24 | channels[0] << 16 | channels[1] << 8 | channels[2])
+}
+/// `ComponentSerialization.CODEC` decoding into text. `selector` components
+/// are resolved by `resolve` (ComponentUtils.updateForEntity).
+pub fn to_text(v: &Value, resolve: &mut dyn FnMut(&str) -> Text) -> Text {
+    to_text_with(v, resolve, &mut |_| None)
+}
+/// `to_text` with a hook resolving other contents (`nbt`) from the object.
+pub fn to_text_with(
+    v: &Value,
+    resolve: &mut dyn FnMut(&str) -> Text,
+    contents: &mut dyn FnMut(&serde_json::Map<String, Value>) -> Option<Text>,
+) -> Text {
+    match v {
+        Value::String(s) => Text::literal(s.clone()),
+        Value::Number(n) => Text::literal(n.to_string()),
+        Value::Bool(b) => Text::literal(b.to_string()),
+        // A list is its first element with the rest as siblings.
+        Value::Array(list) => {
+            let Some((first, rest)) = list.split_first() else {
+                return Text::empty();
+            };
+            let mut base = to_text_with(first, resolve, contents);
+            // The siblings take the first component's own style, even when
+            // its text is empty.
+            let style = match first {
+                Value::Object(o) => object_style(o),
+                _ => base
+                    .spans
+                    .first()
+                    .map(|s| s.style.clone())
+                    .unwrap_or_default(),
+            };
+            for sibling in rest {
+                base.push(to_text_with(sibling, resolve, contents).with_style(&style));
+            }
+            base
+        }
+        Value::Object(o) => {
+            let style = object_style(o);
+            let content = if let Some(t) = contents(o) {
+                t
+            } else if let Some(object) = inline_object(o, resolve, contents) {
+                let mut text = Text::literal("\u{fffc}");
+                text.spans[0].style.inline_object = Some(object);
+                text
+            } else if let Some(t) = o.get("text") {
+                match t {
+                    Value::String(s) => Text::literal(s.clone()),
+                    other => Text::literal(other.to_string()),
+                }
+            } else if let Some(key) = o.get("translate").and_then(Value::as_str) {
+                let args: Vec<Text> = o
+                    .get("with")
+                    .and_then(Value::as_array)
+                    .map(|a| {
+                        a.iter()
+                            .map(|x| to_text_with(x, resolve, contents))
+                            .collect()
+                    })
+                    .unwrap_or_default();
+                let translated = Text::translate(key, &args);
+                match o.get("fallback").and_then(Value::as_str) {
+                    Some(fallback) if translated.plain() == key => Text::translate(fallback, &args),
+                    _ => translated,
+                }
+            } else if let Some(sel) = o.get("selector").and_then(Value::as_str) {
+                resolve(sel)
+            } else if let Some(key) = o.get("keybind").and_then(Value::as_str) {
+                crate::key_display::display_name(key)
+            } else {
+                Text::empty()
+            };
+            let mut out = content.with_style(&style);
+            for extra in o
+                .get("extra")
+                .and_then(Value::as_array)
+                .into_iter()
+                .flatten()
+            {
+                out.push(to_text_with(extra, resolve, contents).with_style(&style));
+            }
+            if o.contains_key("object") || o.contains_key("player") || o.contains_key("sprite") {
+                out.with_component(Value::Object(o.clone()))
+            } else {
+                out
+            }
+        }
+        Value::Null => Text::empty(),
+    }
+}
+
+fn inline_object(
+    object: &serde_json::Map<String, Value>,
+    resolve: &mut dyn FnMut(&str) -> Text,
+    contents: &mut dyn FnMut(&serde_json::Map<String, Value>) -> Option<Text>,
+) -> Option<InlineObject> {
+    let kind = object.get("object").and_then(Value::as_str);
+    let fallback = object
+        .get("fallback")
+        .map(|value| to_text_with(value, resolve, contents).plain());
+    match kind {
+        Some("player") | None if object.contains_key("player") => {
+            let profile = object.get("player")?.clone();
+            // PlayerSprite.defaultFallback.
+            let fallback = fallback.unwrap_or_else(|| {
+                match profile
+                    .as_str()
+                    .or_else(|| profile.get("name").and_then(Value::as_str))
+                {
+                    Some(name) => format!("[{name} head]"),
+                    None => "[unknown player head]".to_owned(),
+                }
+            });
+            Some(InlineObject::Player {
+                profile,
+                hat: object.get("hat").and_then(Value::as_bool).unwrap_or(true),
+                fallback,
+            })
+        }
+        Some("atlas") | None if object.contains_key("sprite") => {
+            let atlas = object
+                .get("atlas")
+                .and_then(Value::as_str)
+                .unwrap_or("minecraft:blocks")
+                .to_owned();
+            let sprite = object.get("sprite")?.as_str()?.to_owned();
+            // AtlasSprite.defaultFallback: short names, the atlas unless blocks.
+            let fallback = fallback.unwrap_or_else(|| {
+                let short = |id: &str| match id.split_once(':') {
+                    Some(("minecraft", path)) => path.to_owned(),
+                    Some(_) => id.to_owned(),
+                    None => id.to_owned(),
+                };
+                if short(&atlas) == "blocks" {
+                    format!("[{}]", short(&sprite))
+                } else {
+                    format!("[{}@{}]", short(&sprite), short(&atlas))
+                }
+            });
+            Some(InlineObject::Atlas {
+                atlas,
+                sprite,
+                fallback,
+            })
+        }
+        _ => None,
+    }
+}
+
+/// `CustomName` as text: a string keeps its legacy formatting codes, anything
+/// else is a component (`ComponentSerialization`).
+pub fn name_text(tag: &Tag) -> Text {
+    match tag {
+        Tag::String(s) => Text::legacy(&s.to_string_lossy()),
+        t => crate::scoreboard::comp_text(&crate::scoreboard::tag_to_json(t)),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn shadow_color_accepts_packed_and_rgba_styles() {
+        let packed = serde_json::json!({"text": "A", "shadow_color": -16711936});
+        let text = to_text(&packed, &mut |_| Text::empty());
+        assert_eq!(text.spans[0].style.shadow_color, Some(0xff00ff00));
+        assert_eq!(text.component()["shadow_color"], -16711936);
+        let rgba = serde_json::json!({"text": "A", "shadow_color": [1, 0, 0.5, 1]});
+        let text = to_text(&rgba, &mut |_| Text::empty());
+        assert_eq!(text.spans[0].style.shadow_color, Some(0xffff007f));
+        let translucent = serde_json::json!({"text": "A", "shadow_color": [1, 0, 0.5, 0.5]});
+        let text = to_text(&translucent, &mut |_| Text::empty());
+        assert_eq!(text.spans[0].style.shadow_color, Some(0x7fff007f));
+        let no_shadow = serde_json::json!({"text": "A", "shadow_color": 0});
+        let text = to_text(&no_shadow, &mut |_| Text::empty());
+        assert_eq!(text.spans[0].style.shadow_color, Some(0));
+    }
+
+    #[test]
+    fn player_object_survives_text_parsing_and_keeps_its_siblings() {
+        let component = serde_json::json!({
+            "text": "<",
+            "extra": [
+                {"object": "player", "player": {"name": "elyapluggin"}, "hat": false,
+                 "fallback": "[head]"},
+                {"text": " >", "color": "gold"}
+            ]
+        });
+        let text = to_text(&component, &mut |_| Text::empty());
+        assert_eq!(text.plain(), "<[head] >");
+        assert!(matches!(
+            &text.spans[1].style.inline_object,
+            Some(InlineObject::Player { hat: false, .. })
+        ));
+        assert!(text.spans[2].style.inline_object.is_none());
+        assert_eq!(text.component(), component);
+        let sprite = serde_json::json!({"object": "atlas", "sprite": "minecraft:item/porkchop"});
+        let text = to_text(&sprite, &mut |_| Text::empty());
+        assert!(matches!(
+            &text.spans[0].style.inline_object,
+            Some(InlineObject::Atlas { sprite, .. }) if sprite == "minecraft:item/porkchop"
+        ));
+        // ObjectContents.visit without a fallback: the sprite's defaultFallback.
+        assert_eq!(text.plain(), "[item/porkchop]");
+        let head = serde_json::json!({"object": "player", "player": {"name": "Steve"}});
+        assert_eq!(
+            to_text(&head, &mut |_| Text::empty()).plain(),
+            "[Steve head]"
+        );
+        let gui = serde_json::json!({"atlas": "gui", "sprite": "hud/heart/full"});
+        assert_eq!(
+            to_text(&gui, &mut |_| Text::empty()).plain(),
+            "[hud/heart/full@gui]"
+        );
+    }
+
+    #[test]
+    fn snbt_and_json_components() {
+        let input = "{text:'Hi ',color:red,extra:[{text:\"there\",bold:1b}]} rest";
+        let (v, n) = parse_snbt(input).unwrap();
+        assert_eq!(&input[n..], " rest");
+        let t = to_text(&v, &mut |_| Text::empty());
+        assert_eq!(t.plain(), "Hi there");
+        assert_eq!(t.spans[1].style.color, named_color("red"));
+        let (v, _) = parse_snbt("[\"a\",{\"text\":\"b\"}]").unwrap();
+        assert_eq!(to_text(&v, &mut |_| Text::empty()).plain(), "ab");
+    }
+
+    #[test]
+    fn the_font_is_inherited_and_kept() {
+        let (v, _) =
+            parse_snbt(r#"{text:"a",font:"alt",extra:["b",{text:"c",font:"minecraft:uniform"}]}"#)
+                .unwrap();
+        let t = to_text(&v, &mut |_| Text::empty());
+        let fonts: Vec<_> = t.chars().map(|(_, s)| s.font.clone()).collect();
+        let (alt, uniform) = (
+            Some("minecraft:alt".into()),
+            Some("minecraft:uniform".into()),
+        );
+        assert_eq!(fonts, [alt.clone(), alt, uniform]);
+        // Back to JSON with the field, which a re-read keeps.
+        let again = to_text(&t.component(), &mut |_| Text::empty());
+        let kept: Vec<_> = again.chars().map(|(_, s)| s.font.clone()).collect();
+        assert_eq!(kept, fonts);
+        // Not an identifier: no font.
+        let (v, _) = parse_snbt(r#"{text:"a",font:"Bad Font"}"#).unwrap();
+        let t = to_text(&v, &mut |_| Text::empty());
+        assert_eq!(t.spans[0].style.font, None);
+    }
+
+    #[test]
+    fn snbt_nesting_is_bounded() {
+        let nest = |n: usize| format!("{}1{}", "[".repeat(n), "]".repeat(n));
+        assert!(parse_snbt(&nest(512)).is_ok());
+        assert!(parse_snbt(&nest(513)).is_err());
+        assert!(parse_snbt(&nest(100_000)).is_err());
+    }
+
+    #[test]
+    fn bare_words_that_look_numeric_stay_strings() {
+        let (v, _) = parse_snbt("{text:nan}").unwrap();
+        assert_eq!(v["text"], Value::String("nan".into()));
+        let (v, _) = parse_snbt("{text:Infinity}").unwrap();
+        assert_eq!(v["text"], Value::String("Infinity".into()));
+        let (v, _) = parse_snbt("{n:1.5}").unwrap();
+        assert_eq!(v["n"], Value::from(1.5));
+    }
+}

crates/horizon-client-core/src/gamerules.rs

@@ -292,27 +292,4 @@ mod tests {
         assert_eq!(GameRules::load(&dir), rules);
         let _ = fs::remove_dir_all(dir);
     }
-    /// The world's save (Level.write) writes the rules as they are now, and a
-    /// world opened again reads them back (#74).
-    #[test]
-    fn level_save_keeps_changed_rules() {
-        let dir =
-            std::env::temp_dir().join(format!("horizon-gamerules-level-{}", std::process::id()));
-        let _ = fs::remove_dir_all(&dir);
-        let mut level = crate::save::Level::default();
-        level.write(&dir).unwrap();
-        // Rules changed while playing, then saved and loaded again.
-        let mut rules = GameRules::load(&dir);
-        assert_eq!(rules, GameRules::default());
-        assert!(rules.set("advance_time", Value::Bool(false)));
-        assert!(rules.set("advance_weather", Value::Bool(false)));
-        assert!(rules.set("random_tick_speed", Value::Int(0)));
-        level.game_rules = rules.by_name();
-        level.write(&dir).unwrap();
-        assert_eq!(GameRules::load(&dir), rules);
-        let read = crate::save::Level::read(&dir).unwrap();
-        assert_eq!(read.game_rules, rules.by_name());
-        assert_eq!(read.game_rule("advance_time"), 0);
-        let _ = fs::remove_dir_all(dir);
-    }
 }

crates/horizon-client-core/src/identifier.rs

@@ -0,0 +1,35 @@
+//! Resource identifiers (`Identifier`).
+
+/// Identifier.parse: `ns:path` or `path`, validated.
+pub fn parse_identifier(raw: &str) -> Option<String> {
+    let (ns, path) = match raw.split_once(':') {
+        Some(("", path)) => ("minecraft", path),
+        Some((ns, path)) => (ns, path),
+        None => ("minecraft", raw),
+    };
+    let ns_ok = ns != ".."
+        && ns
+            .chars()
+            .all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || matches!(c, '_' | '.' | '-'));
+    let path_ok = path.chars().all(|c| {
+        c.is_ascii_lowercase() || c.is_ascii_digit() || matches!(c, '_' | '.' | '-' | '/')
+    });
+    (ns_ok && path_ok).then(|| format!("{ns}:{path}"))
+}
+
+/// `Identifier.CODEC` parsing an entity id: lowercase namespace and path
+/// characters, `minecraft` when the namespace is left out.
+pub fn normalize_id(s: &str) -> Option<String> {
+    let (ns, path) = match s.split_once(':') {
+        Some((ns, path)) => (if ns.is_empty() { "minecraft" } else { ns }, path),
+        None => ("minecraft", s),
+    };
+    let ok = |c: char, slash: bool| {
+        c.is_ascii_lowercase()
+            || c.is_ascii_digit()
+            || matches!(c, '_' | '-' | '.')
+            || slash && c == '/'
+    };
+    (ns.chars().all(|c| ok(c, false)) && path.chars().all(|c| ok(c, true)))
+        .then(|| format!("{ns}:{path}"))
+}

crates/horizon-client-core/src/key_display.rs

@@ -0,0 +1,107 @@
+//! Key display names (`InputConstants.Key.getDisplayName`), shared by key
+//! mappings and `keybind` text components.
+use crate::text::Text;
+use std::{collections::BTreeMap, sync::RwLock};
+
+/// The keys that write a symbol, with what they write on a US layout.
+const SYMBOLS: [(&str, &str); 11] = [
+    ("key.keyboard.minus", "-"),
+    ("key.keyboard.equal", "="),
+    ("key.keyboard.left.bracket", "["),
+    ("key.keyboard.right.bracket", "]"),
+    ("key.keyboard.backslash", "\\"),
+    ("key.keyboard.semicolon", ";"),
+    ("key.keyboard.apostrophe", "'"),
+    ("key.keyboard.grave.accent", "`"),
+    ("key.keyboard.comma", ","),
+    ("key.keyboard.period", "."),
+    ("key.keyboard.slash", "/"),
+];
+
+/// What the player's keyboard layout writes on each key that writes
+/// something, by key name, as the window reported it (`learn_layout`).
+static LAYOUT: RwLock<BTreeMap<String, String>> = RwLock::new(BTreeMap::new());
+
+/// The keyboard layout writes `text` on the key `key` (`key.keyboard.q`):
+/// its name from now on, as `SDL_GetKeyFromScancode` names it with SDL's
+/// default keycode options. Only letter and symbol keys take it; a letter
+/// key keeps its Latin letter on a non-Latin layout (`latin_letters`), and
+/// the number row keeps its digits (`french_numbers`).
+pub fn learn_layout(key: &str, text: &str) {
+    let Some(rest) = key.strip_prefix("key.keyboard.") else {
+        return;
+    };
+    let mut chars = text.chars();
+    let (Some(c), None) = (chars.next(), chars.next()) else {
+        return;
+    };
+    let letter_key = rest.len() == 1 && rest.as_bytes()[0].is_ascii_lowercase();
+    let latin = c.is_ascii() || ('\u{C0}'..='\u{24F}').contains(&c);
+    if c.is_control()
+        || c.is_whitespace()
+        || !(letter_key || SYMBOLS.iter().any(|(k, _)| *k == key))
+        || (letter_key && c.is_alphabetic() && !latin)
+    {
+        return;
+    }
+    if let Ok(mut layout) = LAYOUT.write() {
+        layout.insert(key.to_owned(), c.to_uppercase().collect());
+    }
+}
+
+/// InputConstants.Key.getDisplayName: what the layout writes on the key,
+/// upper-case, else the US layout's character, else by translation.
+pub fn display_name(key: &str) -> Text {
+    if let Some(label) = LAYOUT.read().ok().and_then(|l| l.get(key).cloned()) {
+        return Text::literal(label);
+    }
+    if let Some(rest) = key.strip_prefix("key.keyboard.")
+        && rest.chars().count() == 1
+    {
+        let c = rest.to_uppercase();
+        return Text::literal(c);
+    }
+    if let Some((_, s)) = SYMBOLS.iter().find(|(k, _)| *k == key) {
+        return Text::literal(*s);
+    }
+    if let Some(n) = key.strip_prefix("key.mouse.")
+        && n.parse::<u32>().is_ok()
+        && !crate::lang::has(key)
+    {
+        return Text::translate("key.mouse", &[Text::literal(n)]);
+    }
+    Text::translate(key, &[])
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn keys_show_what_the_layout_writes() {
+        // The layout table is shared: these keys are this test's alone.
+        assert_eq!(display_name("key.keyboard.q").plain(), "Q");
+        // AZERTY: A on the Q key, M on the semicolon key, a dead ^ on the
+        // left bracket, a comma on the M key.
+        learn_layout("key.keyboard.q", "a");
+        learn_layout("key.keyboard.semicolon", "m");
+        learn_layout("key.keyboard.left.bracket", "^");
+        learn_layout("key.keyboard.m", ",");
+        assert_eq!(display_name("key.keyboard.q").plain(), "A");
+        assert_eq!(display_name("key.keyboard.semicolon").plain(), "M");
+        assert_eq!(display_name("key.keyboard.left.bracket").plain(), "^");
+        assert_eq!(display_name("key.keyboard.m").plain(), ",");
+        // The number row keeps its digits; a Cyrillic letter, nothing
+        // printable and keys that write nothing are left alone.
+        learn_layout("key.keyboard.1", "&");
+        learn_layout("key.keyboard.f", "а");
+        learn_layout("key.keyboard.g", "\u{8}");
+        learn_layout("key.keyboard.tab", "\t");
+        learn_layout("key.keyboard.h", "ab");
+        assert_eq!(display_name("key.keyboard.1").plain(), "1");
+        assert_eq!(display_name("key.keyboard.f").plain(), "F");
+        assert_eq!(display_name("key.keyboard.g").plain(), "G");
+        assert_eq!(display_name("key.keyboard.h").plain(), "H");
+        assert_eq!(display_name("key.keyboard.slash").plain(), "/");
+    }
+}

crates/horizon-client-core/src/lang.rs

@@ -4,7 +4,10 @@
 //! language used by every screen.
 use std::{
     collections::{BTreeMap, HashMap},
-    sync::{Arc, RwLock},
+    sync::{
+        Arc, RwLock,
+        atomic::{AtomicBool, Ordering},
+    },
 };
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -23,24 +26,61 @@ impl LanguageInfo {
 #[derive(Default)]
 pub struct Language {
     pub code: String,
+    /// `LanguageInfo.bidirectional`: text without a strong character reads
+    /// right to left (`ClientLanguage.defaultRightToLeft`).
+    bidirectional: bool,
     map: HashMap<String, String>,
 }
 pub const DEFAULT: &str = "en_us";
 
 static CURRENT: RwLock<Option<Arc<Language>>> = RwLock::new(None);
+/// The current language's `bidirectional`, read for every drawn string.
+static BIDIRECTIONAL: AtomicBool = AtomicBool::new(false);
 
 /// A source of resource files: the prepared root plus packs, highest priority last.
 pub trait ResourceSource {
     fn read(&self, path: &str) -> Option<Vec<u8>>;
+    /// Whether `path` is there, without reading it where the source can tell.
+    fn exists(&self, path: &str) -> bool {
+        self.read(path).is_some()
+    }
     /// The namespaces under `assets/` (resource packs may add their own).
     fn namespaces(&self) -> Vec<String> {
         vec!["minecraft".into()]
     }
 }
+/// Horizon's own strings, compiled in so they need no prepared resources.
+struct Bundled;
+impl ResourceSource for Bundled {
+    fn read(&self, path: &str) -> Option<Vec<u8>> {
+        let body = match path {
+            "assets/horizon/lang/en_us.json" => {
+                include_str!("../../horizon-client/assets/horizon/lang/en_us.json")
+            }
+            "assets/horizon/lang/ru_ru.json" => {
+                include_str!("../../horizon-client/assets/horizon/lang/ru_ru.json")
+            }
+            "assets/horizon/lang/pl_pl.json" => {
+                include_str!("../../horizon-client/assets/horizon/lang/pl_pl.json")
+            }
+            "assets/horizon/lang/uk_ua.json" => {
+                include_str!("../../horizon-client/assets/horizon/lang/uk_ua.json")
+            }
+            _ => return None,
+        };
+        Some(body.as_bytes().to_vec())
+    }
+    fn namespaces(&self) -> Vec<String> {
+        vec!["horizon".into()]
+    }
+}
 impl ResourceSource for std::path::PathBuf {
     fn read(&self, path: &str) -> Option<Vec<u8>> {
         std::fs::read(self.join(path)).ok()
     }
+    fn exists(&self, path: &str) -> bool {
+        self.join(path).is_file()
+    }
     fn namespaces(&self) -> Vec<String> {
         std::fs::read_dir(self.join("assets"))
             .into_iter()
@@ -86,6 +126,12 @@ impl Language {
         if code != DEFAULT {
             codes.push(code);
         }
+        // Horizon's own strings first, so a pack or the prepared root can still
+        // override them. Vanilla has no key for "Controller vibration".
+        let bundled = Bundled;
+        let mut all: Vec<&dyn ResourceSource> = vec![&bundled];
+        all.extend_from_slice(sources);
+        let sources = all.as_slice();
         let namespaces: std::collections::BTreeSet<String> =
             sources.iter().flat_map(|s| s.namespaces()).collect();
         for c in codes {
@@ -109,14 +155,23 @@ impl Language {
         {
             apply_deprecated(&mut map, &bytes);
         }
+        let bidirectional = available(sources)
+            .iter()
+            .any(|info| info.code == code && info.bidirectional);
         Self {
             code: code.to_owned(),
+            bidirectional,
             map,
         }
     }
     pub fn get(&self, key: &str) -> Option<&str> {
         self.map.get(key).map(String::as_str)
     }
+    /// The resolved map, for `horizon_protocol::text::plain`: a server's
+    /// components carry keys, and the network layer resolves them with this.
+    pub fn map(&self) -> &HashMap<String, String> {
+        &self.map
+    }
     pub fn len(&self) -> usize {
         self.map.len()
     }
@@ -148,7 +203,7 @@ pub fn available(sources: &[&dyn ResourceSource]) -> Vec<LanguageInfo> {
             for (code, info) in value["language"].as_object().into_iter().flatten() {
                 // Only languages whose file exists somewhere are selectable.
                 let file = format!("assets/minecraft/lang/{code}.json");
-                if code != DEFAULT && !sources.iter().any(|s| s.read(&file).is_some()) {
+                if code != DEFAULT && !sources.iter().any(|s| s.exists(&file)) {
                     continue;
                 }
                 found.insert(
@@ -167,11 +222,16 @@ pub fn available(sources: &[&dyn ResourceSource]) -> Vec<LanguageInfo> {
 }
 
 pub fn set(language: Language) {
+    BIDIRECTIONAL.store(language.bidirectional, Ordering::Relaxed);
     *CURRENT.write().unwrap_or_else(|e| e.into_inner()) = Some(Arc::new(language));
 }
 pub fn current() -> Option<Arc<Language>> {
     CURRENT.read().unwrap_or_else(|e| e.into_inner()).clone()
 }
+/// `ClientLanguage.defaultRightToLeft` of the current language.
+pub fn bidirectional() -> bool {
+    BIDIRECTIONAL.load(Ordering::Relaxed)
+}
 pub fn code() -> String {
     current().map_or_else(|| DEFAULT.to_owned(), |l| l.code.clone())
 }
@@ -204,6 +264,31 @@ mod tests {
             self.0.get(path).cloned()
         }
     }
+    #[test]
+    fn bundled_horizon_strings_follow_the_language() {
+        // No prepared resources at all: the namespace is compiled in.
+        let empty = Mem(HashMap::new());
+        let en = Language::load(&[&empty], "en_us");
+        assert_eq!(en.get("horizon.options.controller"), Some("Controller"));
+        let ru = Language::load(&[&empty], "ru_ru");
+        assert_eq!(ru.get("horizon.options.controller"), Some("Геймпад"));
+        // Every bundled string carries both languages: a key added to one file
+        // and forgotten in the other shows as a key name on screen.
+        for key in en.map().keys() {
+            assert!(ru.get(key).is_some(), "{key} has no ru_ru value");
+        }
+        assert_eq!(en.get("horizon.pages.mods"), Some("Mods"));
+        assert_eq!(ru.get("horizon.pages.mods"), Some("Моды"));
+        let pl = Language::load(&[&empty], "pl_pl");
+        assert_eq!(pl.get("horizon.options.controller"), Some("Kontroler"));
+        assert_eq!(pl.get("horizon.options.vibration"), Some("Wibracje"));
+        let uk = Language::load(&[&empty], "uk_ua");
+        assert_eq!(
+            uk.get("horizon.options.on_screen_keyboard"),
+            Some("Екранна клавіатура")
+        );
+    }
+
     #[test]
     fn layers_selected_language_over_english() {
         let base = Mem(HashMap::from([
@@ -227,4 +312,26 @@ mod tests {
         );
         assert_eq!(langs[1].label(), "Français (France)");
     }
+
+    #[test]
+    fn languages_are_listed_without_reading_their_files() {
+        struct NoLangReads;
+        impl ResourceSource for NoLangReads {
+            fn read(&self, path: &str) -> Option<Vec<u8>> {
+                assert!(!path.contains("/lang/"), "read {path}");
+                (path == "assets/pack.mcmeta").then(|| {
+                    br#"{"language":{"fr_fr":{"name":"French"},"de_de":{"name":"German"}}}"#
+                        .to_vec()
+                })
+            }
+            fn exists(&self, path: &str) -> bool {
+                path == "assets/minecraft/lang/fr_fr.json"
+            }
+        }
+        let langs = available(&[&NoLangReads]);
+        assert_eq!(
+            langs.iter().map(|l| l.code.as_str()).collect::<Vec<_>>(),
+            ["en_us", "fr_fr"]
+        );
+    }
 }

crates/horizon-client-core/src/lib.rs

@@ -0,0 +1,28 @@
+//! The client's lowest layer, below commands and gameplay: chat text and
+//! translations, SNBT and NBT paths, text components, the scoreboard, boss
+//! bars, game rules, block entity NBT tables, and the registry, particle and
+//! sound source tables commands name, and the `pack.mcmeta` filter regex.
+//! horizon-client re-exports each module under its old path
+//! (`horizon_client::text`, ...).
+#![forbid(unsafe_code)]
+pub mod block_entity_nbt;
+pub mod bossbar;
+pub mod component;
+pub mod fastutil_order;
+pub mod gamerules;
+pub mod identifier;
+pub mod key_display;
+pub mod lang;
+pub mod nbt_path;
+pub mod nbt_value;
+pub mod particle_type;
+pub mod pattern;
+pub mod potions;
+pub mod registries;
+pub mod scoreboard;
+pub mod snbt;
+pub mod sound_source;
+pub mod text;
+pub mod uuid;
+pub mod who;
+pub type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;

crates/horizon-client-core/src/nbt_value.rs

@@ -0,0 +1,32 @@
+//! Reading and writing single NBT values the way vanilla's codecs accept them.
+use horizon_world::nbt::Tag;
+
+pub fn string(s: &str) -> Tag {
+    Tag::String(s.into())
+}
+pub fn text(tag: Option<&Tag>) -> Option<String> {
+    match tag {
+        Some(Tag::String(s)) => Some(s.to_string_lossy()),
+        _ => None,
+    }
+}
+/// Any numeric tag as i64 (vanilla's `getIntOr` etc. accept every number type).
+pub fn number(tag: Option<&Tag>) -> Option<i64> {
+    Some(match tag? {
+        Tag::Byte(v) => i64::from(*v),
+        Tag::Short(v) => i64::from(*v),
+        Tag::Int(v) => i64::from(*v),
+        Tag::Long(v) => *v,
+        Tag::Float(b) => f32::from_bits(*b) as i64,
+        Tag::Double(b) => f64::from_bits(*b) as i64,
+        _ => return None,
+    })
+}
+/// Any numeric tag as f64, keeping a float's or double's fraction.
+pub fn float(tag: Option<&Tag>) -> Option<f64> {
+    Some(match tag? {
+        Tag::Float(b) => f64::from(f32::from_bits(*b)),
+        Tag::Double(b) => f64::from_bits(*b),
+        other => number(Some(other))? as f64,
+    })
+}

crates/horizon-client-core/src/particle_type.rs

@@ -0,0 +1,221 @@
+//! Particle types (`ParticleTypes`): the vanilla particle types with a client
+//! implementation, by registry name, and their per-type flags.
+
+macro_rules! particle_types {
+    ($($variant:ident = $name:literal),* $(,)?) => {
+        /// Vanilla particle types with a client implementation here.
+        #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+        pub enum ParticleType { $($variant),* }
+        impl ParticleType {
+            pub const ALL: &'static [ParticleType] = &[$(ParticleType::$variant),*];
+            /// Registry path (`minecraft:<name>`), also the sprite-set file name.
+            pub fn name(self) -> &'static str {
+                match self { $(ParticleType::$variant => $name),* }
+            }
+            pub fn from_name(name: &str) -> Option<Self> {
+                let name = name.strip_prefix("minecraft:").unwrap_or(name);
+                match name { $($name => Some(ParticleType::$variant),)* _ => None }
+            }
+        }
+    };
+}
+particle_types! {
+    Block = "block",
+    BlockCrumble = "block_crumble",
+    Trail = "trail",
+    DustPillar = "dust_pillar",
+    FallingDust = "falling_dust",
+    Smoke = "smoke",
+    LargeSmoke = "large_smoke",
+    WhiteSmoke = "white_smoke",
+    Flame = "flame",
+    SoulFireFlame = "soul_fire_flame",
+    CopperFireFlame = "copper_fire_flame",
+    SmallFlame = "small_flame",
+    Lava = "lava",
+    DrippingWater = "dripping_water",
+    FallingWater = "falling_water",
+    DrippingLava = "dripping_lava",
+    FallingLava = "falling_lava",
+    LandingLava = "landing_lava",
+    DrippingHoney = "dripping_honey",
+    FallingHoney = "falling_honey",
+    LandingHoney = "landing_honey",
+    FallingNectar = "falling_nectar",
+    FallingSporeBlossom = "falling_spore_blossom",
+    SporeBlossomAir = "spore_blossom_air",
+    DrippingObsidianTear = "dripping_obsidian_tear",
+    FallingObsidianTear = "falling_obsidian_tear",
+    LandingObsidianTear = "landing_obsidian_tear",
+    DrippingDripstoneWater = "dripping_dripstone_water",
+    FallingDripstoneWater = "falling_dripstone_water",
+    DrippingDripstoneLava = "dripping_dripstone_lava",
+    FallingDripstoneLava = "falling_dripstone_lava",
+    Splash = "splash",
+    Rain = "rain",
+    Bubble = "bubble",
+    SulfurBubbles = "sulfur_bubbles",
+    NoxiousGas = "noxious_gas",
+    NoxiousGasCloud = "noxious_gas_cloud",
+    Geyser = "geyser",
+    GeyserBase = "geyser_base",
+    GeyserPoof = "geyser_poof",
+    GeyserPlume = "geyser_plume",
+    BubblePop = "bubble_pop",
+    BubbleColumnUp = "bubble_column_up",
+    CurrentDown = "current_down",
+    Underwater = "underwater",
+    Portal = "portal",
+    ReversePortal = "reverse_portal",
+    Enchant = "enchant",
+    Nautilus = "nautilus",
+    VaultConnection = "vault_connection",
+    Crit = "crit",
+    EnchantedHit = "enchanted_hit",
+    DamageIndicator = "damage_indicator",
+    Heart = "heart",
+    AngryVillager = "angry_villager",
+    HappyVillager = "happy_villager",
+    Composter = "composter",
+    Mycelium = "mycelium",
+    Dolphin = "dolphin",
+    EggCrack = "egg_crack",
+    Poof = "poof",
+    Explosion = "explosion",
+    ExplosionEmitter = "explosion_emitter",
+    CampfireCosySmoke = "campfire_cosy_smoke",
+    CampfireSignalSmoke = "campfire_signal_smoke",
+    Note = "note",
+    Dust = "dust",
+    TotemOfUndying = "totem_of_undying",
+    Firework = "firework",
+    EndRod = "end_rod",
+    Ash = "ash",
+    WhiteAsh = "white_ash",
+    CrimsonSpore = "crimson_spore",
+    WarpedSpore = "warped_spore",
+    CherryLeaves = "cherry_leaves",
+    PaleOakLeaves = "pale_oak_leaves",
+    TintedLeaves = "tinted_leaves",
+    Effect = "effect",
+    InstantEffect = "instant_effect",
+    EntityEffect = "entity_effect",
+    Witch = "witch",
+    Infested = "infested",
+    Cloud = "cloud",
+    Sneeze = "sneeze",
+    Snowflake = "snowflake",
+    Soul = "soul",
+    SculkSoul = "sculk_soul",
+    DragonBreath = "dragon_breath",
+    Gust = "gust",
+    SmallGust = "small_gust",
+    GustEmitterLarge = "gust_emitter_large",
+    GustEmitterSmall = "gust_emitter_small",
+    DustColorTransition = "dust_color_transition",
+    SculkCharge = "sculk_charge",
+    SculkChargePop = "sculk_charge_pop",
+    Shriek = "shriek",
+    SonicBoom = "sonic_boom",
+    Vibration = "vibration",
+    SweepAttack = "sweep_attack",
+    Glow = "glow",
+    WaxOn = "wax_on",
+    WaxOff = "wax_off",
+    ElectricSpark = "electric_spark",
+    Scrape = "scrape",
+    SquidInk = "squid_ink",
+    GlowSquidInk = "glow_squid_ink",
+    Item = "item",
+    ItemSlime = "item_slime",
+    ItemSnowball = "item_snowball",
+    ItemCobweb = "item_cobweb",
+    SulfurCubeGoo = "sulfur_cube_goo",
+    Flash = "flash",
+    Firefly = "firefly",
+    TrialSpawnerDetection = "trial_spawner_detection",
+    TrialSpawnerDetectionOminous = "trial_spawner_detection_ominous",
+    TrialOmen = "trial_omen",
+    RaidOmen = "raid_omen",
+    OminousSpawning = "ominous_spawning",
+    Spit = "spit",
+    Fishing = "fishing",
+    DustPlume = "dust_plume",
+    RedPoplarLeaves = "red_poplar_leaves",
+    OrangePoplarLeaves = "orange_poplar_leaves",
+    YellowPoplarLeaves = "yellow_poplar_leaves",
+    PauseMobGrowth = "pause_mob_growth",
+    ResetMobGrowth = "reset_mob_growth",
+    BlockMarker = "block_marker",
+}
+impl ParticleType {
+    /// `ParticleType.getOverrideLimiter` (`ParticleTypes.register(name, true)`):
+    /// spawned regardless of distance.
+    pub fn override_limiter(self) -> bool {
+        matches!(
+            self,
+            Self::BlockMarker
+                | Self::Geyser
+                | Self::GeyserBase
+                | Self::GeyserPoof
+                | Self::GeyserPlume
+                | Self::DamageIndicator
+                | Self::ExplosionEmitter
+                | Self::Explosion
+                | Self::Gust
+                | Self::GustEmitterLarge
+                | Self::GustEmitterSmall
+                | Self::SonicBoom
+                | Self::SculkCharge
+                | Self::SculkChargePop
+                | Self::Vibration
+                | Self::Poof
+                | Self::Spit
+                | Self::SquidInk
+                | Self::SweepAttack
+                | Self::CampfireCosySmoke
+                | Self::CampfireSignalSmoke
+                | Self::GlowSquidInk
+                | Self::Glow
+                | Self::WaxOn
+                | Self::WaxOff
+                | Self::ElectricSpark
+                | Self::Scrape
+                | Self::TrialSpawnerDetection
+                | Self::TrialSpawnerDetectionOminous
+                | Self::VaultConnection
+                | Self::OminousSpawning
+        )
+    }
+    /// `SingleQuadParticle.Layer.translucent`: types whose vanilla particle class
+    /// hardcodes the translucent layer, drawn after translucent terrain.
+    /// `TerrainParticle`, `BreakingItemParticle` and `BlockMarker` resolve their
+    /// layer from the sprite instead (`Layer.bySprite`); see the `translucent`
+    /// sprite set on the engine.
+    pub fn translucent_layer(self) -> bool {
+        match self {
+            // CampfireSmokeParticle.
+            Self::CampfireCosySmoke | Self::CampfireSignalSmoke
+            // PlayerCloudParticle.
+            | Self::Cloud | Self::Sneeze
+            // SpellParticle.
+            | Self::Effect | Self::InstantEffect | Self::EntityEffect
+            | Self::Witch | Self::Infested | Self::TrialOmen | Self::RaidOmen
+            // NoxiousGasParticle.
+            | Self::NoxiousGas
+            // EmissiveRisingParticle.
+            | Self::Soul | Self::SculkSoul
+            // SculkChargeParticle, SculkChargePopParticle, ShriekParticle,
+            // VibrationSignalParticle, FireflyParticle, OverlayParticle.
+            | Self::SculkCharge | Self::SculkChargePop | Self::Shriek
+            | Self::Vibration | Self::Firefly | Self::Flash
+            // SimpleAnimatedParticle and its subclasses: EndRodParticle,
+            // SparkParticle (firework), SquidInkParticle, TotemParticle.
+            | Self::EndRod | Self::Firework | Self::SquidInk | Self::GlowSquidInk
+            | Self::TotemOfUndying
+            // FlyTowardsPositionParticle: its LifetimeAlpha(0, 0.6, 0.25, 1) is not opaque.
+            | Self::VaultConnection => true,
+            _ => false,
+        }
+    }
+}

crates/horizon-client-core/src/potions.rs

@@ -0,0 +1,250 @@
+//! The `MobEffects` and `Potions` registries (code in vanilla, ported as
+//! tables): each effect's colour and category, each potion's effects, and the
+//! potion colour mix. horizon-client re-exports them from `brewing`.
+use std::{collections::HashMap, sync::OnceLock};
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Category {
+    Beneficial,
+    Harmful,
+    Neutral,
+}
+/// A `MobEffect`: id (without namespace), colour, category, instantaneous.
+#[derive(Clone, Copy, Debug)]
+pub struct EffectDef {
+    pub id: &'static str,
+    pub color: u32,
+    pub category: Category,
+    pub instant: bool,
+}
+const fn fx(id: &'static str, color: u32, category: Category) -> EffectDef {
+    EffectDef {
+        id,
+        color,
+        category,
+        instant: false,
+    }
+}
+use Category::{Beneficial as B, Harmful as H, Neutral as N};
+/// `MobEffects` in registration order.
+pub const EFFECTS: &[EffectDef] = &[
+    fx("speed", 3402751, B),
+    fx("slowness", 9154528, H),
+    fx("haste", 14270531, B),
+    fx("mining_fatigue", 4866583, H),
+    fx("strength", 16762624, B),
+    EffectDef {
+        id: "instant_health",
+        color: 16262179,
+        category: B,
+        instant: true,
+    },
+    EffectDef {
+        id: "instant_damage",
+        color: 11101546,
+        category: H,
+        instant: true,
+    },
+    fx("jump_boost", 16646020, B),
+    fx("nausea", 5578058, H),
+    fx("regeneration", 13458603, B),
+    fx("resistance", 9520880, B),
+    fx("fire_resistance", 16750848, B),
+    fx("water_breathing", 10017472, B),
+    fx("invisibility", 16185078, B),
+    fx("blindness", 2039587, H),
+    fx("night_vision", 12779366, B),
+    fx("hunger", 5797459, H),
+    fx("weakness", 4738376, H),
+    fx("poison", 8889187, H),
+    fx("wither", 7561558, H),
+    fx("health_boost", 16284963, B),
+    fx("absorption", 2445989, B),
+    EffectDef {
+        id: "saturation",
+        color: 16262179,
+        category: B,
+        instant: true,
+    },
+    fx("glowing", 9740385, N),
+    fx("levitation", 13565951, H),
+    fx("luck", 5882118, B),
+    fx("unluck", 12624973, H),
+    fx("slow_falling", 15978425, B),
+    fx("conduit_power", 1950417, B),
+    fx("dolphins_grace", 8954814, B),
+    fx("bad_omen", 745784, N),
+    fx("hero_of_the_village", 4521796, B),
+    fx("darkness", 2696993, H),
+    fx("trial_omen", 1484454, N),
+    fx("raid_omen", 14565464, N),
+    fx("wind_charged", 12438015, H),
+    fx("weaving", 7891290, H),
+    fx("oozing", 10092451, H),
+    fx("infested", 9214860, H),
+    fx("breath_of_the_nautilus", 65518, B),
+];
+pub fn effect(id: &str) -> Option<&'static EffectDef> {
+    let id = id.trim_start_matches("minecraft:");
+    EFFECTS.iter().find(|e| e.id == id)
+}
+/// Namespaced effect ids for mob effect storage.
+pub fn namespaced(id: &'static str) -> &'static str {
+    static IDS: OnceLock<HashMap<&'static str, &'static str>> = OnceLock::new();
+    let key = id.strip_prefix("minecraft:").unwrap_or(id);
+    IDS.get_or_init(|| {
+        EFFECTS
+            .iter()
+            .map(|e| {
+                (
+                    e.id,
+                    &*Box::leak(format!("minecraft:{}", e.id).into_boxed_str()),
+                )
+            })
+            .collect()
+    })
+    .get(key)
+    .copied()
+    .unwrap_or(id)
+}
+/// A `Potion`: id, name suffix (`item.minecraft.potion.effect.<name>`) and
+/// effects as (effect, duration ticks, amplifier).
+#[derive(Clone, Copy, Debug)]
+pub struct PotionDef {
+    pub id: &'static str,
+    pub name: &'static str,
+    pub effects: &'static [(&'static str, i32, i32)],
+}
+const fn p(
+    id: &'static str,
+    name: &'static str,
+    effects: &'static [(&'static str, i32, i32)],
+) -> PotionDef {
+    PotionDef { id, name, effects }
+}
+/// `Potions` in registration order.
+pub const POTIONS: &[PotionDef] = &[
+    p("water", "water", &[]),
+    p("mundane", "mundane", &[]),
+    p("thick", "thick", &[]),
+    p("awkward", "awkward", &[]),
+    p("night_vision", "night_vision", &[("night_vision", 3600, 0)]),
+    p(
+        "long_night_vision",
+        "night_vision",
+        &[("night_vision", 9600, 0)],
+    ),
+    p("invisibility", "invisibility", &[("invisibility", 3600, 0)]),
+    p(
+        "long_invisibility",
+        "invisibility",
+        &[("invisibility", 9600, 0)],
+    ),
+    p("leaping", "leaping", &[("jump_boost", 3600, 0)]),
+    p("long_leaping", "leaping", &[("jump_boost", 9600, 0)]),
+    p("strong_leaping", "leaping", &[("jump_boost", 1800, 1)]),
+    p(
+        "fire_resistance",
+        "fire_resistance",
+        &[("fire_resistance", 3600, 0)],
+    ),
+    p(
+        "long_fire_resistance",
+        "fire_resistance",
+        &[("fire_resistance", 9600, 0)],
+    ),
+    p("swiftness", "swiftness", &[("speed", 3600, 0)]),
+    p("long_swiftness", "swiftness", &[("speed", 9600, 0)]),
+    p("strong_swiftness", "swiftness", &[("speed", 1800, 1)]),
+    p("slowness", "slowness", &[("slowness", 1800, 0)]),
+    p("long_slowness", "slowness", &[("slowness", 4800, 0)]),
+    p("strong_slowness", "slowness", &[("slowness", 400, 3)]),
+    p(
+        "turtle_master",
+        "turtle_master",
+        &[("slowness", 400, 3), ("resistance", 400, 2)],
+    ),
+    p(
+        "long_turtle_master",
+        "turtle_master",
+        &[("slowness", 800, 3), ("resistance", 800, 2)],
+    ),
+    p(
+        "strong_turtle_master",
+        "turtle_master",
+        &[("slowness", 400, 5), ("resistance", 400, 3)],
+    ),
+    p(
+        "water_breathing",
+        "water_breathing",
+        &[("water_breathing", 3600, 0)],
+    ),
+    p(
+        "long_water_breathing",
+        "water_breathing",
+        &[("water_breathing", 9600, 0)],
+    ),
+    p("healing", "healing", &[("instant_health", 1, 0)]),
+    p("strong_healing", "healing", &[("instant_health", 1, 1)]),
+    p("harming", "harming", &[("instant_damage", 1, 0)]),
+    p("strong_harming", "harming", &[("instant_damage", 1, 1)]),
+    p("poison", "poison", &[("poison", 900, 0)]),
+    p("long_poison", "poison", &[("poison", 1800, 0)]),
+    p("strong_poison", "poison", &[("poison", 432, 1)]),
+    p("regeneration", "regeneration", &[("regeneration", 900, 0)]),
+    p(
+        "long_regeneration",
+        "regeneration",
+        &[("regeneration", 1800, 0)],
+    ),
+    p(
+        "strong_regeneration",
+        "regeneration",
+        &[("regeneration", 450, 1)],
+    ),
+    p("strength", "strength", &[("strength", 3600, 0)]),
+    p("long_strength", "strength", &[("strength", 9600, 0)]),
+    p("strong_strength", "strength", &[("strength", 1800, 1)]),
+    p("weakness", "weakness", &[("weakness", 1800, 0)]),
+    p("long_weakness", "weakness", &[("weakness", 4800, 0)]),
+    p("luck", "luck", &[("luck", 6000, 0)]),
+    p("slow_falling", "slow_falling", &[("slow_falling", 1800, 0)]),
+    p(
+        "long_slow_falling",
+        "slow_falling",
+        &[("slow_falling", 4800, 0)],
+    ),
+    p("wind_charged", "wind_charged", &[("wind_charged", 3600, 0)]),
+    p("weaving", "weaving", &[("weaving", 3600, 0)]),
+    p("oozing", "oozing", &[("oozing", 3600, 0)]),
+    p("infested", "infested", &[("infested", 3600, 0)]),
+];
+pub fn potion(id: &str) -> Option<&'static PotionDef> {
+    let id = id.trim_start_matches("minecraft:");
+    POTIONS.iter().find(|p| p.id == id)
+}
+/// `PotionContents.BASE_POTION_COLOR` (ARGB -13083194) as RGB.
+pub const BASE_POTION_COLOR: u32 = 0x385DC6;
+/// `PotionContents.getColor`: amplifier-weighted mix of visible effect colours.
+pub fn potion_color(id: Option<&str>) -> u32 {
+    let Some(def) = id.and_then(potion) else {
+        return BASE_POTION_COLOR;
+    };
+    let (mut r, mut g, mut b, mut total) = (0u32, 0u32, 0u32, 0u32);
+    for (e, _, amp) in def.effects {
+        let Some(e) = effect(e) else { continue };
+        let w = *amp as u32 + 1;
+        r += w * (e.color >> 16 & 255);
+        g += w * (e.color >> 8 & 255);
+        b += w * (e.color & 255);
+        total += w;
+    }
+    match (
+        r.checked_div(total),
+        g.checked_div(total),
+        b.checked_div(total),
+    ) {
+        (Some(r), Some(g), Some(b)) => (r << 16) | (g << 8) | b,
+        _ => BASE_POTION_COLOR,
+    }
+}

crates/horizon-client-core/src/registries.rs

@@ -0,0 +1,246 @@
+//! Registry contents and source state that commands validate and complete
+//! arguments against (what the server's registry access holds).
+use std::collections::BTreeMap;
+
+/// Registry contents and source state used to validate and complete arguments.
+#[derive(Clone, Debug, Default)]
+pub struct Registries {
+    /// Permission level of the command source.
+    pub permission: u8,
+    pub items: Vec<String>,
+    pub item_tags: Vec<String>,
+    /// Block id -> (property, allowed values).
+    pub blocks: BTreeMap<String, Vec<(String, Vec<String>)>>,
+    pub block_tags: Vec<String>,
+    /// Entity types that `summon` can create.
+    pub summonable: Vec<String>,
+    /// Every entity type (selector `type=`).
+    pub entity_types: Vec<String>,
+    pub effects: Vec<String>,
+    pub enchantments: Vec<String>,
+    pub structures: Vec<String>,
+    pub biomes: Vec<String>,
+    pub dimensions: Vec<String>,
+    pub clocks: Vec<String>,
+    pub timelines: Vec<String>,
+    pub time_markers: Vec<String>,
+    pub advancements: Vec<String>,
+    /// Game rule name -> integer-valued.
+    pub game_rules: Vec<(String, bool)>,
+    pub players: Vec<String>,
+    /// `ClientSuggestionProvider.customCompletionSuggestions`: the extra chat
+    /// completions the server sent (ClientboundCustomChatCompletionsPacket),
+    /// each once.
+    pub custom_completions: std::collections::BTreeSet<String>,
+    /// Scoreboard objective names, team names and tracked score holders.
+    pub objectives: Vec<String>,
+    pub teams: Vec<String>,
+    pub tracked: Vec<String>,
+    /// Loaded datapack functions (`ns:path`) and function tags (`ns:path`).
+    pub functions: Vec<String>,
+    /// `/data ... storage` ids.
+    pub storages: Vec<String>,
+    /// Boss bar ids and datapack predicate ids.
+    pub bossbars: Vec<String>,
+    pub predicates: Vec<String>,
+    pub item_modifiers: Vec<String>,
+    pub schedules: Vec<String>,
+    pub stopwatches: Vec<String>,
+    pub recipes: Vec<String>,
+    pub sounds: Vec<String>,
+    pub damage_types: Vec<String>,
+    pub attributes: Vec<String>,
+    pub loot_tables: Vec<String>,
+    pub templates: Vec<String>,
+    pub random_sequences: Vec<String>,
+    pub datapacks_enabled: Vec<String>,
+    pub datapacks_disabled: Vec<String>,
+    pub function_tags: Vec<String>,
+    /// The block the source is looking at (relevant coordinates).
+    pub target_block: Option<[i32; 3]>,
+    /// `ClientSuggestionProvider.getSelectedEntities`: the UUID of the
+    /// entity under the crosshair (`Entity.getStringUUID`), if any.
+    pub selected_entities: Vec<String>,
+    /// `ClientSuggestionProvider.getAbsoluteCoordinates`: the exact point of
+    /// that block hit, each coordinate as `%.2f` (`Locale.ROOT`).
+    pub target_point: Option<[String; 3]>,
+    /// Every registry's element and tag ids (`minecraft:item` -> ...), as
+    /// the server's registry access and reloadable registries hold them.
+    pub by_registry: BTreeMap<String, RegistryIds>,
+    /// Blocks whose default state has a block entity.
+    pub block_entities: std::collections::BTreeSet<String>,
+    /// Block tag -> member blocks.
+    pub block_tag_members: BTreeMap<String, Vec<String>>,
+    /// Data component types with a codec (not transient).
+    pub persistent_components: Vec<String>,
+    /// Recipes `/recipe` can give (not special).
+    pub learnable_recipes: Vec<String>,
+    /// Advancement id -> criterion names.
+    pub advancement_criteria: BTreeMap<String, Vec<String>>,
+    /// World clock -> time markers shown in commands.
+    pub clock_time_markers: BTreeMap<String, Vec<String>>,
+    /// Trigger objectives the source may use (`/trigger` suggestions).
+    pub trigger_objectives: Vec<String>,
+    /// Objectives with the `trigger` criterion -> holder -> whether its score is locked.
+    pub trigger_scores: BTreeMap<String, BTreeMap<String, bool>>,
+}
+/// The ids and tag ids of one registry.
+#[derive(Clone, Debug, Default)]
+pub struct RegistryIds {
+    pub ids: Vec<String>,
+    pub tags: Vec<String>,
+}
+const EMPTY: &[String] = &[];
+/// ClientboundCustomChatCompletionsPacket.Action.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum CustomCompletionAction {
+    Add,
+    Remove,
+    Set,
+}
+impl CustomCompletionAction {
+    /// `Action.BY_ID`: `ByIdMap.continuous` with `OutOfBoundsStrategy.ZERO`,
+    /// so an unknown id is `ADD`.
+    pub fn from_id(id: i32) -> Self {
+        match id {
+            1 => Self::Remove,
+            2 => Self::Set,
+            _ => Self::Add,
+        }
+    }
+}
+/// `ClientSuggestionProvider.modifyCustomCompletions`: the server adds,
+/// removes or replaces the extra chat completions.
+pub fn modify_custom_completions(
+    set: &mut std::collections::BTreeSet<String>,
+    action: CustomCompletionAction,
+    entries: &[String],
+) {
+    match action {
+        CustomCompletionAction::Add => set.extend(entries.iter().cloned()),
+        CustomCompletionAction::Remove => {
+            for e in entries {
+                set.remove(e);
+            }
+        }
+        CustomCompletionAction::Set => {
+            set.clear();
+            set.extend(entries.iter().cloned());
+        }
+    }
+}
+impl Registries {
+    /// `ClientSuggestionProvider.getCustomTabSuggestions`: what chat (not a
+    /// command) completes, the online players' names with the server's custom
+    /// completions, each once.
+    pub fn custom_tab_suggestions(&self) -> std::collections::BTreeSet<&str> {
+        self.players
+            .iter()
+            .chain(&self.custom_completions)
+            .map(String::as_str)
+            .collect()
+    }
+    /// Fill what the game did not build itself from vanilla's exported
+    /// registries (`command-registries.json`, written by
+    /// `VanillaCommandParseOracle registries`): built-in registries such as
+    /// mob effects, data component types and dialogs, block entities and tag
+    /// members. Registries that data packs reload stay with the game.
+    pub fn fill_from_export(&mut self, r: &serde_json::Value) {
+        fn strings(v: &serde_json::Value) -> Vec<String> {
+            v.as_array()
+                .map(|a| {
+                    a.iter()
+                        .filter_map(|x| x.as_str().map(str::to_owned))
+                        .collect()
+                })
+                .unwrap_or_default()
+        }
+        let fill = |field: &mut Vec<String>, key: &str| {
+            if field.is_empty() {
+                *field = strings(&r[key]);
+            }
+        };
+        fill(&mut self.effects, "effects");
+        fill(&mut self.enchantments, "enchantments");
+        fill(&mut self.attributes, "attributes");
+        fill(&mut self.damage_types, "damage_types");
+        fill(&mut self.templates, "templates");
+        fill(&mut self.persistent_components, "persistent_components");
+        fill(&mut self.learnable_recipes, "learnable_recipes");
+        const RELOADED: [&str; 5] = [
+            "minecraft:advancement",
+            "minecraft:recipe",
+            "minecraft:loot_table",
+            "minecraft:predicate",
+            "minecraft:item_modifier",
+        ];
+        for (name, entry) in r["by_registry"].as_object().into_iter().flatten() {
+            if RELOADED.contains(&name.as_str()) || self.by_registry.contains_key(name) {
+                continue;
+            }
+            self.by_registry.insert(
+                name.clone(),
+                RegistryIds {
+                    ids: strings(&entry["ids"]),
+                    tags: strings(&entry["tags"]),
+                },
+            );
+        }
+        if self.block_entities.is_empty() {
+            self.block_entities = strings(&r["block_entities"]).into_iter().collect();
+        }
+        if self.block_tag_members.is_empty() {
+            for (tag, members) in r["block_tag_members"].as_object().into_iter().flatten() {
+                self.block_tag_members.insert(tag.clone(), strings(members));
+            }
+        }
+        if self.clock_time_markers.is_empty() {
+            for (clock, markers) in r["clock_time_markers"].as_object().into_iter().flatten() {
+                self.clock_time_markers
+                    .insert(clock.clone(), strings(markers));
+            }
+        }
+        if self.advancement_criteria.is_empty() {
+            for (id, criteria) in r["advancement_criteria"].as_object().into_iter().flatten() {
+                self.advancement_criteria
+                    .insert(id.clone(), strings(criteria));
+            }
+        }
+    }
+    /// The element ids of a registry (sorted).
+    pub fn ids(&self, registry: &str) -> &[String] {
+        if let Some(r) = self.by_registry.get(registry) {
+            return &r.ids;
+        }
+        match registry {
+            "minecraft:item" => &self.items,
+            "minecraft:entity_type" => &self.entity_types,
+            "minecraft:mob_effect" => &self.effects,
+            "minecraft:enchantment" => &self.enchantments,
+            "minecraft:worldgen/structure" => &self.structures,
+            "minecraft:worldgen/biome" => &self.biomes,
+            "minecraft:world_clock" => &self.clocks,
+            "minecraft:timeline" => &self.timelines,
+            "minecraft:attribute" => &self.attributes,
+            "minecraft:damage_type" => &self.damage_types,
+            "minecraft:sound_event" => &self.sounds,
+            "minecraft:predicate" => &self.predicates,
+            "minecraft:item_modifier" => &self.item_modifiers,
+            "minecraft:loot_table" => &self.loot_tables,
+            "minecraft:recipe" => &self.recipes,
+            "minecraft:advancement" => &self.advancements,
+            _ => EMPTY,
+        }
+    }
+    /// The tag ids of a registry (sorted).
+    pub fn tags(&self, registry: &str) -> &[String] {
+        if let Some(r) = self.by_registry.get(registry) {
+            return &r.tags;
+        }
+        match registry {
+            "minecraft:item" => &self.item_tags,
+            "minecraft:block" => &self.block_tags,
+            _ => EMPTY,
+        }
+    }
+}

crates/horizon-client-core/src/scoreboard.rs

@@ -2,9 +2,9 @@
 //! `ObjectiveCriteria`, `NumberFormat`) and its saved data
 //! (`data/minecraft/scoreboard.dat`, `ScoreboardSaveData.Packed`).
 use crate::{
-    command::Registries,
     component,
     fastutil_order::{HashSetOrder, OpenOrder},
+    registries::Registries,
     text::{self, Style, Text},
 };
 use horizon_world::nbt::Tag;
@@ -112,6 +112,7 @@ pub fn style_from_json(v: &Value) -> Style {
                 .and_then(|h| u32::from_str_radix(h, 16).ok())
         });
     }
+    s.shadow_color = o.get("shadow_color").and_then(component::shadow_color);
     let flag = |k: &str| o.get(k).and_then(Value::as_bool);
     s.bold = flag("bold");
     s.italic = flag("italic");
@@ -662,10 +663,22 @@ pub fn name_shown(own: Option<&Team>, viewer: Option<&Team>, v: NameView) -> boo
     }
     !v.hud_hidden && !v.is_camera && visible && !v.is_vehicle
 }
-/// `ServerPlayer.die`: whether a player's death message reaches the player
-/// themselves (the team broadcasts leave out the dying player).
-pub fn own_death_message_shown(team: Option<&Team>) -> bool {
-    team.is_none_or(|t| t.death_message_visibility == Visibility::Always)
+/// `ServerPlayer.die`: whether `other` hears the death message of `dying`
+/// (`broadcastSystemMessage`, `broadcastSystemToTeam` or
+/// `broadcastSystemToAllExceptTeam`, by the team's death message visibility).
+pub fn death_message_reaches(board: &Scoreboard, dying: &str, other: &str) -> bool {
+    let Some(team) = board.players_team(dying) else {
+        return true;
+    };
+    let same_team = board
+        .players_team(other)
+        .is_some_and(|t| t.name == team.name);
+    match team.death_message_visibility {
+        Visibility::Always => true,
+        Visibility::Never => false,
+        Visibility::HideForOtherTeams => same_team && other != dying,
+        Visibility::HideForOwnTeam => !same_team,
+    }
 }
 
 // ---- objectives and scores ---------------------------------------------
@@ -1266,7 +1279,7 @@ fn entity_uuids(tag: &mut Tag) {
                             })
                             .collect::<Option<Vec<i32>>>(),
                         Tag::String(s) => {
-                            crate::save::uuid_from_text(&s.to_string_lossy()).map(Vec::from)
+                            crate::uuid::uuid_from_text(&s.to_string_lossy()).map(Vec::from)
                         }
                         _ => None,
                     };
@@ -1551,3 +1564,49 @@ mod tests {
         );
     }
 }
+
+/// `DamageSource.getLocalizedDeathMessage`: the cause's item with a custom
+/// name gets the `<id>.item` message, with the item's name as a third
+/// argument.
+pub fn death_message_args(
+    key: &str,
+    victim: &Text,
+    cause: &Text,
+    item: Option<&Text>,
+) -> (String, Vec<Text>) {
+    match item {
+        Some(item) => (
+            format!("{key}.item"),
+            vec![victim.clone(), cause.clone(), item.clone()],
+        ),
+        None => (key.to_owned(), vec![victim.clone(), cause.clone()]),
+    }
+}
+
+#[cfg(test)]
+mod death_message_tests {
+    use super::*;
+
+    #[test]
+    fn the_death_message_names_the_causes_item_when_it_has_a_custom_name() {
+        let victim = Text::literal("Steve");
+        let cause = Text::literal("Zombie");
+        // DamageSource.getLocalizedDeathMessage: the item variant, with the
+        // item's name as the third argument.
+        let (key, args) = death_message_args(
+            "death.attack.arrow",
+            &victim,
+            &cause,
+            Some(&Text::literal("My Sword")),
+        );
+        assert_eq!(key, "death.attack.arrow.item");
+        assert_eq!(args.len(), 3);
+        assert_eq!(args[0].plain(), "Steve");
+        assert_eq!(args[1].plain(), "Zombie");
+        assert_eq!(args[2].plain(), "My Sword");
+        // Without a custom name the message keeps its two arguments.
+        let (key, args) = death_message_args("death.attack.arrow", &victim, &cause, None);
+        assert_eq!(key, "death.attack.arrow");
+        assert_eq!(args.len(), 2);
+    }
+}

crates/horizon-client-core/src/sound_source.rs

@@ -0,0 +1,7 @@
+//! Sound sources (`SoundSource`), by name.
+
+/// SoundSource names in vanilla order.
+pub const SOUND_SOURCES: [&str; 11] = [
+    "master", "music", "record", "weather", "block", "hostile", "neutral", "player", "ambient",
+    "voice", "ui",
+];

crates/horizon-client-core/src/text.rs

@@ -42,17 +42,50 @@ pub fn named_color(name: &str) -> Option<u32> {
 /// Click actions carried by locally constructed text components.
 #[derive(Clone, Debug, PartialEq, Eq)]
 pub enum ClickEvent {
+    /// `ClickEvent.OpenUrl`: an http or https link.
+    OpenUrl(String),
+    /// `ClickEvent.ChangePage`: a book's page, counted from 1.
+    ChangePage(i32),
     SuggestCommand(String),
+    /// `ClickEvent.RunCommand`: the command, with or without its `/`.
+    RunCommand(String),
     CopyToClipboard(String),
+    /// `ClickEvent.ShowDialog`: a `minecraft:dialog` registry id, or the
+    /// dialog itself as the component carried it.
+    ShowDialog(horizon_world::nbt::Tag),
     /// A local file to open with the system handler.
     /// Only allow this in locally constructed messages, never server/LAN text.
     OpenFile(String),
 }
 
+/// A non-character `minecraft:object` embedded in a text component.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum InlineObject {
+    Player {
+        profile: Value,
+        hat: bool,
+        fallback: String,
+    },
+    Atlas {
+        atlas: String,
+        sprite: String,
+        fallback: String,
+    },
+}
+impl InlineObject {
+    pub fn fallback(&self) -> &str {
+        match self {
+            Self::Player { fallback, .. } | Self::Atlas { fallback, .. } => fallback,
+        }
+    }
+}
+
 /// Text style; `None` fields inherit from the enclosing style.
 #[derive(Clone, Debug, Default, PartialEq, Eq)]
 pub struct Style {
     pub color: Option<u32>,
+    /// Text component `shadow_color` as packed ARGB. Zero suppresses shadows.
+    pub shadow_color: Option<u32>,
     pub bold: Option<bool>,
     pub italic: Option<bool>,
     pub underlined: Option<bool>,
@@ -61,13 +94,21 @@ pub struct Style {
     pub click: Option<ClickEvent>,
     /// Hover text.
     pub hover: Option<Box<Text>>,
+    /// `HoverEvent.ShowItem`: the event's `{id, count?, components?}` object.
+    pub hover_item: Option<Box<Value>>,
+    /// `HoverEvent.ShowEntity`: the event's `{id, uuid, name?}` object.
+    pub hover_entity: Option<Box<Value>>,
+    /// `Style.insertion`: the text a Shift-click puts in the chat box.
+    pub insertion: Option<String>,
     /// The font (`FontDescription.Resource`), a full id like
     /// `minecraft:alt`; the default font when unset.
     pub font: Option<String>,
+    /// Content metadata for a single U+FFFC object span; never inherited.
+    pub inline_object: Option<InlineObject>,
 }
 /// A style's `font` field: an identifier (`alt` is `minecraft:alt`).
 pub fn font_id(v: &Value) -> Option<String> {
-    crate::command::args::parse_identifier(v.as_str()?)
+    crate::identifier::parse_identifier(v.as_str()?)
 }
 impl Style {
     pub fn color(c: u32) -> Self {
@@ -79,6 +120,7 @@ impl Style {
     /// Fill unset fields from `base` (Style.applyTo).
     pub fn inherit(&mut self, base: &Style) {
         self.color = self.color.or(base.color);
+        self.shadow_color = self.shadow_color.or(base.shadow_color);
         self.bold = self.bold.or(base.bold);
         self.italic = self.italic.or(base.italic);
         self.underlined = self.underlined.or(base.underlined);
@@ -87,8 +129,15 @@ impl Style {
         if self.click.is_none() {
             self.click.clone_from(&base.click);
         }
-        if self.hover.is_none() {
+        // One HoverEvent: its three kinds are inherited together, so a style
+        // with its own event never picks up another kind from `base`.
+        if self.hover.is_none() && self.hover_item.is_none() && self.hover_entity.is_none() {
             self.hover.clone_from(&base.hover);
+            self.hover_item.clone_from(&base.hover_item);
+            self.hover_entity.clone_from(&base.hover_entity);
+        }
+        if self.insertion.is_none() {
+            self.insertion.clone_from(&base.insertion);
         }
         if self.font.is_none() {
             self.font.clone_from(&base.font);
@@ -318,7 +367,13 @@ impl Text {
     }
     /// Component.getString: the plain characters.
     pub fn plain(&self) -> String {
-        self.spans.iter().map(|s| s.text.as_str()).collect()
+        self.spans
+            .iter()
+            .map(|s| match &s.style.inline_object {
+                Some(object) if s.text == "\u{fffc}" => object.fallback(),
+                _ => s.text.as_str(),
+            })
+            .collect()
     }
     pub fn is_empty(&self) -> bool {
         self.spans.iter().all(|s| s.text.is_empty())
@@ -384,31 +439,7 @@ impl Text {
                     continue;
                 }
                 let Some(code) = chars.next() else { break };
-                let code = code.to_ascii_lowercase();
-                let next = if let Some(c) = COLORS.iter().find(|c| c.0 == code) {
-                    // Style.applyLegacyFormat: a colour clears the decorations.
-                    Style {
-                        color: Some(c.2),
-                        bold: Some(false),
-                        italic: Some(false),
-                        underlined: Some(false),
-                        strikethrough: Some(false),
-                        obfuscated: Some(false),
-                        ..style.clone()
-                    }
-                } else {
-                    let mut s = style.clone();
-                    match code {
-                        'k' => s.obfuscated = Some(true),
-                        'l' => s.bold = Some(true),
-                        'm' => s.strikethrough = Some(true),
-                        'n' => s.underlined = Some(true),
-                        'o' => s.italic = Some(true),
-                        'r' => s = span.style.clone(),
-                        _ => {}
-                    }
-                    s
-                };
+                let next = legacy_format(&style, code, &span.style);
                 if next != style {
                     if !current.is_empty() {
                         out.spans.push(Span {
@@ -428,6 +459,15 @@ impl Text {
         }
         out
     }
+    /// `resolve_legacy` borrowing `self` when no span holds a `§` code (the
+    /// common case).
+    pub fn resolved(&self) -> std::borrow::Cow<'_, Text> {
+        if self.spans.iter().any(|s| s.text.contains('§')) {
+            std::borrow::Cow::Owned(self.resolve_legacy())
+        } else {
+            std::borrow::Cow::Borrowed(self)
+        }
+    }
     /// The text without its legacy `§` codes (ChatFormatting.stripFormatting:
     /// a `§` and a code character, `0`-`9`, `a`-`f`, `k`-`o` or `r`).
     pub fn strip_legacy(&self) -> Text {
@@ -486,8 +526,9 @@ impl Text {
 }
 
 /// The style fields of a component's JSON.
-const STYLE_KEYS: [&str; 9] = [
+const STYLE_KEYS: [&str; 11] = [
     "color",
+    "shadow_color",
     "bold",
     "italic",
     "underlined",
@@ -495,6 +536,7 @@ const STYLE_KEYS: [&str; 9] = [
     "obfuscated",
     "click_event",
     "hover_event",
+    "insertion",
     "font",
 ];
 /// Style.Serializer: the fields a style sets.
@@ -507,6 +549,9 @@ fn style_json(style: &Style) -> Vec<(String, Value)> {
             .map_or_else(|| format!("#{c:06X}"), |n| n.1.to_owned());
         out.push(("color".to_owned(), name.into()));
     }
+    if let Some(shadow) = style.shadow_color {
+        out.push(("shadow_color".to_owned(), Value::from(shadow as i32)));
+    }
     for (key, flag) in [
         ("bold", style.bold),
         ("italic", style.italic),
@@ -520,12 +565,22 @@ fn style_json(style: &Style) -> Vec<(String, Value)> {
     }
     if let Some(click) = &style.click {
         let event = match click {
+            ClickEvent::OpenUrl(url) => json!({ "action": "open_url", "url": url }),
+            ClickEvent::ChangePage(page) => json!({ "action": "change_page", "page": page }),
             ClickEvent::SuggestCommand(command) => {
                 json!({ "action": "suggest_command", "command": command })
             }
             ClickEvent::CopyToClipboard(value) => {
                 json!({ "action": "copy_to_clipboard", "value": value })
             }
+            ClickEvent::RunCommand(command) => {
+                json!({ "action": "run_command", "command": command })
+            }
+            // ClickEvent.ShowDialog.CODEC: the dialog the server sent it with.
+            ClickEvent::ShowDialog(dialog) => json!({
+                "action": "show_dialog",
+                "dialog": crate::scoreboard::tag_to_json(dialog),
+            }),
             ClickEvent::OpenFile(path) => json!({ "action": "open_file", "path": path }),
         };
         out.push(("click_event".to_owned(), event));
@@ -535,6 +590,17 @@ fn style_json(style: &Style) -> Vec<(String, Value)> {
             "hover_event".to_owned(),
             json!({ "action": "show_text", "value": hover.component() }),
         ));
+    } else if let Some(Value::Object(item)) = style.hover_item.as_deref() {
+        let mut event = item.clone();
+        event.insert("action".into(), "show_item".into());
+        out.push(("hover_event".to_owned(), Value::Object(event)));
+    } else if let Some(Value::Object(entity)) = style.hover_entity.as_deref() {
+        let mut event = entity.clone();
+        event.insert("action".into(), "show_entity".into());
+        out.push(("hover_event".to_owned(), Value::Object(event)));
+    }
+    if let Some(insertion) = &style.insertion {
+        out.push(("insertion".to_owned(), insertion.clone().into()));
     }
     if let Some(font) = &style.font {
         out.push(("font".to_owned(), font.clone().into()));
@@ -542,6 +608,35 @@ fn style_json(style: &Style) -> Vec<(String, Value)> {
     out
 }
 
+/// `Style.applyLegacyFormat` for the code after a `§`, `§r` going back to
+/// `reset` (`StringDecomposer.iterateFormatted`); an unknown code changes nothing.
+pub fn legacy_format(style: &Style, code: char, reset: &Style) -> Style {
+    let code = code.to_ascii_lowercase();
+    if let Some(c) = COLORS.iter().find(|c| c.0 == code) {
+        // A colour clears the decorations.
+        return Style {
+            color: Some(c.2),
+            bold: Some(false),
+            italic: Some(false),
+            underlined: Some(false),
+            strikethrough: Some(false),
+            obfuscated: Some(false),
+            ..style.clone()
+        };
+    }
+    let mut s = style.clone();
+    match code {
+        'k' => s.obfuscated = Some(true),
+        'l' => s.bold = Some(true),
+        'm' => s.strikethrough = Some(true),
+        'n' => s.underlined = Some(true),
+        'o' => s.italic = Some(true),
+        'r' => s = reset.clone(),
+        _ => {}
+    }
+    s
+}
+
 /// TranslatableContents.decomposeTemplate: `%s` takes the next argument,
 /// `%n$s` a numbered one and `%%` is a percent sign. Malformed templates are
 /// shown verbatim.
@@ -695,4 +790,20 @@ mod tests {
         assert_eq!(t.spans[1].style.color, Some(GOLD));
         assert_eq!(t.slice(1, 2).plain(), "y");
     }
+    #[test]
+    fn resolved_borrows_clean_text_and_restyles_codes() {
+        let clean = Text::colored("Steve", GOLD);
+        assert!(matches!(clean.resolved(), std::borrow::Cow::Borrowed(_)));
+        // A colour code inside a span clears its decorations (a bold
+        // "§cSteve" draws "Steve" red, not bold).
+        let styled = Style {
+            bold: Some(true),
+            ..Style::default()
+        };
+        let styled = Text::styled("§cSteve", styled);
+        let resolved = styled.resolved();
+        assert_eq!(resolved.plain(), "Steve");
+        assert_eq!(resolved.spans[0].style.color, Some(RED));
+        assert_eq!(resolved.spans[0].style.bold, Some(false));
+    }
 }

crates/horizon-client-core/src/uuid.rs

@@ -0,0 +1,24 @@
+//! UUIDs as vanilla's four-int form, to and from their text form.
+
+pub fn uuid_text(u: [i32; 4]) -> String {
+    let hex: String = u.iter().map(|v| format!("{:08x}", *v as u32)).collect();
+    format!(
+        "{}-{}-{}-{}-{}",
+        &hex[0..8],
+        &hex[8..12],
+        &hex[12..16],
+        &hex[16..20],
+        &hex[20..32]
+    )
+}
+pub fn uuid_from_text(s: &str) -> Option<[i32; 4]> {
+    let hex: String = s.chars().filter(|c| *c != '-').collect();
+    if hex.len() != 32 {
+        return None;
+    }
+    let mut out = [0i32; 4];
+    for (i, v) in out.iter_mut().enumerate() {
+        *v = u32::from_str_radix(&hex[i * 8..i * 8 + 8], 16).ok()? as i32;
+    }
+    Some(out)
+}

crates/horizon-client-core/src/who.rs

@@ -0,0 +1,8 @@
+//! Who an action came from or is aimed at: the player or a mob by id.
+
+/// Who caused damage or is being targeted.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub enum Who {
+    Player,
+    Mob(u32),
+}

crates/horizon-client-input/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "horizon-client-input"
+version = "0.1.0"
+edition.workspace = true
+license.workspace = true
+rust-version = "1.90"
+description = "The client's input layer: key bindings and their names, mouse, controllers, clipboard and window options"
+
+[dependencies]
+horizon-client-core = { path = "../horizon-client-core" }
+winit = "0.30.13"
+# The window icon.
+horizon-theme = { path = "../horizon-theme" }
+png = "0.18"
+arboard = { version = "3.6.1", default-features = false, features = ["wayland-data-control"] }
+# The DualSense's trigger effects (the `controllers` feature).
+horizon-dualsense = { path = "../horizon-dualsense", optional = true }
+
+[features]
+controllers = ["dep:horizon-dualsense"]
+
+[lints]
+workspace = true

crates/horizon-client-input/src/clipboard.rs

@@ -60,6 +60,19 @@ pub fn edit_shortcut(
     })
 }
 
+/// Windows reports AltGr as Ctrl plus Alt: the system presses a left Control
+/// in front of the right Alt.
+pub const ALTGR_IS_CTRL_ALT: bool = cfg!(windows);
+
+/// Whether a key's text reaches the screen (`KeyboardHandler.textInput`, then
+/// `charTyped` per code point). The edit modifier's shortcuts type nothing,
+/// but `textInput` takes no modifiers: with AltGr held (Ctrl plus Alt where
+/// `altgr_is_ctrl_alt`) the layout's third-level characters are text, as `/`
+/// on ABNT2, `@`, `{` and `[` on German or the Polish letters.
+pub fn types_text(edit_modifier: bool, alt: bool, altgr_is_ctrl_alt: bool) -> bool {
+    !edit_modifier || (altgr_is_ctrl_alt && alt)
+}
+
 /// `StringUtil.isAllowedChatCharacter`.
 pub fn is_allowed_chat_character(c: char) -> bool {
     c != '§' && c >= ' ' && c != '\u{7f}'
@@ -303,6 +316,22 @@ pub fn append_limited(value: &mut String, text: &str, max_chars: usize) -> bool
 mod tests {
     use super::*;
 
+    #[test]
+    fn altgr_types_text_where_it_is_ctrl_alt() {
+        // Plain keys and Shift type.
+        assert!(types_text(false, false, true));
+        assert!(types_text(false, false, false));
+        // Ctrl (Cmd) shortcuts do not.
+        assert!(!types_text(true, false, true));
+        assert!(!types_text(true, false, false));
+        // AltGr on Windows is Ctrl+Alt: ABNT2 `/`, German `@` type.
+        assert!(types_text(true, true, true));
+        // Where AltGr is its own modifier, Ctrl+Alt is a shortcut.
+        assert!(!types_text(true, true, false));
+        // Alt alone (macOS Option, Linux AltGr) types.
+        assert!(types_text(false, true, false));
+    }
+
     #[test]
     fn shortcuts_need_the_edit_modifier_alone() {
         let c = Some('c');
@@ -346,6 +375,11 @@ mod tests {
         assert_eq!(filter_text(s, true), "abc\nde\u{80}");
         assert_eq!(strip_formatting("§aRed§r §zx§"), "Red §zx§");
         assert_eq!(helper_clipboard_contents("§lone\r\ntwo"), "one\ntwo");
+        // TextFieldHelper.getClipboardContents runs before insertText's filter.
+        assert_eq!(
+            filter_text(&helper_clipboard_contents("§aHello"), false),
+            "Hello"
+        );
     }
 
     struct Field {

crates/horizon-client-input/src/input.rs

@@ -2,6 +2,9 @@
 //! Item-use and sneak multipliers come from the player's current state; this
 //! module does not implement sprint eligibility, poses or the input lifecycle.
 
+use std::collections::HashSet;
+use winit::keyboard::{KeyCode, ModifiersState};
+
 fn length(v: [f32; 2]) -> f32 {
     f64::from(v[0] * v[0] + v[1] * v[1]).sqrt() as f32
 }
@@ -65,3 +68,45 @@ fn square_movement(v: [f32; 2]) -> [f32; 2] {
         },
     )
 }
+
+/// `InputQuirks.isQuitShortcutDown`: checks whether the platform's window-closing
+/// keyboard shortcut is held.
+/// - On macOS: Command (`super_key()`) + `Q`.
+/// - On Windows / Linux / other: Alt (`alt_key()`) + `F4`.
+pub fn is_quit_shortcut_down(modifiers: ModifiersState, keys: &HashSet<KeyCode>) -> bool {
+    if cfg!(target_os = "macos") {
+        modifiers.super_key() && keys.contains(&KeyCode::KeyQ)
+    } else {
+        modifiers.alt_key() && keys.contains(&KeyCode::F4)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn quit_shortcut_follows_platform_modifiers_and_keys() {
+        let mut keys = HashSet::new();
+        let alt = ModifiersState::ALT;
+        let super_key = ModifiersState::SUPER;
+
+        assert!(!is_quit_shortcut_down(ModifiersState::empty(), &keys));
+
+        keys.insert(KeyCode::F4);
+        if cfg!(target_os = "macos") {
+            assert!(!is_quit_shortcut_down(alt, &keys));
+            keys.remove(&KeyCode::F4);
+            keys.insert(KeyCode::KeyQ);
+            assert!(is_quit_shortcut_down(super_key, &keys));
+            assert!(!is_quit_shortcut_down(alt, &keys));
+        } else {
+            assert!(is_quit_shortcut_down(alt, &keys));
+            assert!(!is_quit_shortcut_down(super_key, &keys));
+            keys.remove(&KeyCode::F4);
+            keys.insert(KeyCode::KeyQ);
+            assert!(!is_quit_shortcut_down(alt, &keys));
+            assert!(!is_quit_shortcut_down(super_key, &keys));
+        }
+    }
+}

crates/horizon-client-input/src/interaction_input.rs

@@ -13,6 +13,12 @@ pub enum Button {
 }
 
 pub trait InteractionWorld {
+    /// Minecraft.pick before handleKeybinds: the tick's `hitResult`, which
+    /// every click of the tick reads, even after one of them changed the
+    /// block it names (a creative break, then a use that replaces it).
+    fn pick_hit_result(&mut self);
+    /// The tick's clicks are done: later picks follow the crosshair again.
+    fn release_hit_result(&mut self);
     fn using_item(&self) -> bool;
     fn release_using(&mut self);
     fn start_attack(&mut self) -> bool;
@@ -48,6 +54,7 @@ impl InteractionInput {
 
     pub fn tick(&mut self, world: &mut impl InteractionWorld, attack_down: bool, use_down: bool) {
         let [attack, use_item, pick] = std::mem::take(&mut self.clicks);
+        world.pick_hit_result();
         let mut instant = false;
         if world.using_item() {
             if !use_down {
@@ -70,6 +77,7 @@ impl InteractionInput {
             world.start_use();
         }
         world.continue_attack(!instant && attack_down);
+        world.release_hit_result();
     }
 }
 
@@ -86,6 +94,8 @@ mod tests {
         events: Vec<&'static str>,
     }
     impl InteractionWorld for World {
+        fn pick_hit_result(&mut self) {}
+        fn release_hit_result(&mut self) {}
         fn using_item(&self) -> bool {
             self.using
         }
@@ -183,4 +193,67 @@ mod tests {
         input.tick(&mut world, false, false);
         assert_eq!(world.events, ["release", "continue"]);
     }
+
+    /// A floating block in front of the crosshair, nothing behind it, and a
+    /// block item in the hand of a creative player.
+    #[derive(Default)]
+    struct Column {
+        block: bool,
+        hit: Option<Option<()>>,
+        placed: bool,
+    }
+    impl Column {
+        /// Minecraft.hitResult: the tick's pick, or a fresh one outside it.
+        fn target(&self) -> Option<()> {
+            self.hit.unwrap_or(self.block.then_some(()))
+        }
+    }
+    impl InteractionWorld for Column {
+        fn pick_hit_result(&mut self) {
+            self.hit = Some(self.target());
+        }
+        fn release_hit_result(&mut self) {
+            self.hit = None;
+        }
+        fn using_item(&self) -> bool {
+            false
+        }
+        fn release_using(&mut self) {}
+        fn start_attack(&mut self) -> bool {
+            // MultiPlayerGameMode.startDestroyBlock in creative: the
+            // predicted break leaves air.
+            if self.target().is_some() {
+                self.block = false;
+            }
+            !self.block
+        }
+        fn start_use(&mut self) {
+            // BlockItem.place: the clicked block, now air, can be replaced.
+            if self.target().is_some() && !self.block {
+                self.block = true;
+                self.placed = true;
+            }
+        }
+        fn pick(&mut self) {}
+        fn use_delay(&self) -> u32 {
+            0
+        }
+        fn continue_attack(&mut self, _: bool) {}
+    }
+
+    #[test]
+    fn attack_and_use_in_one_tick_share_the_hit_result() {
+        // #3006: both buttons at once replace the block the crosshair is on.
+        let mut input = InteractionInput::default();
+        let mut world = Column {
+            block: true,
+            ..Default::default()
+        };
+        input.press(Button::Attack);
+        input.press(Button::Use);
+        input.tick(&mut world, false, false);
+        assert!(world.placed, "the use acts on the block the attack broke");
+        assert!(world.block);
+        assert!(world.hit.is_none(), "the next pick follows the crosshair");
+    }
 }

crates/horizon-client-input/src/keybinds.rs

@@ -2,7 +2,6 @@
 //! defaults, `key_<name>:key.keyboard.x` persistence, display names, and the
 //! translation of rebound physical keys back to the default keys the game
 //! logic listens for.
-use crate::text::Text;
 use std::collections::BTreeMap;
 use winit::{event::MouseButton, keyboard::KeyCode};
 
@@ -146,6 +145,22 @@ const KEYS: &[(&str, KeyCode)] = &[
     ("key.keyboard.period", KeyCode::Period),
     ("key.keyboard.slash", KeyCode::Slash),
     ("key.keyboard.caps.lock", KeyCode::CapsLock),
+    ("key.keyboard.world.1", KeyCode::IntlBackslash),
+    ("key.keyboard.international1", KeyCode::IntlRo),
+    ("key.keyboard.international3", KeyCode::IntlYen),
+    ("key.keyboard.lang1", KeyCode::Lang1),
+    ("key.keyboard.lang2", KeyCode::Lang2),
+    ("key.keyboard.lang3", KeyCode::Lang3),
+    ("key.keyboard.lang4", KeyCode::Lang4),
+    ("key.keyboard.lang5", KeyCode::Lang5),
+    ("key.keyboard.help", KeyCode::Help),
+    ("key.keyboard.select", KeyCode::Select),
+    ("key.keyboard.again", KeyCode::Again),
+    ("key.keyboard.undo", KeyCode::Undo),
+    ("key.keyboard.cut", KeyCode::Cut),
+    ("key.keyboard.copy", KeyCode::Copy),
+    ("key.keyboard.paste", KeyCode::Paste),
+    ("key.keyboard.find", KeyCode::Find),
     ("key.keyboard.f1", KeyCode::F1),
     ("key.keyboard.f2", KeyCode::F2),
     ("key.keyboard.f3", KeyCode::F3),
@@ -158,6 +173,18 @@ const KEYS: &[(&str, KeyCode)] = &[
     ("key.keyboard.f10", KeyCode::F10),
     ("key.keyboard.f11", KeyCode::F11),
     ("key.keyboard.f12", KeyCode::F12),
+    ("key.keyboard.f13", KeyCode::F13),
+    ("key.keyboard.f14", KeyCode::F14),
+    ("key.keyboard.f15", KeyCode::F15),
+    ("key.keyboard.f16", KeyCode::F16),
+    ("key.keyboard.f17", KeyCode::F17),
+    ("key.keyboard.f18", KeyCode::F18),
+    ("key.keyboard.f19", KeyCode::F19),
+    ("key.keyboard.f20", KeyCode::F20),
+    ("key.keyboard.f21", KeyCode::F21),
+    ("key.keyboard.f22", KeyCode::F22),
+    ("key.keyboard.f23", KeyCode::F23),
+    ("key.keyboard.f24", KeyCode::F24),
     ("key.keyboard.print.screen", KeyCode::PrintScreen),
     ("key.keyboard.scroll.lock", KeyCode::ScrollLock),
     ("key.keyboard.pause", KeyCode::Pause),
@@ -189,6 +216,36 @@ const KEYS: &[(&str, KeyCode)] = &[
     ("key.keyboard.keypad.0", KeyCode::Numpad0),
     ("key.keyboard.keypad.period", KeyCode::NumpadDecimal),
     ("key.keyboard.keypad.equal", KeyCode::NumpadEqual),
+    ("key.keyboard.keypad.comma", KeyCode::NumpadComma),
+    ("key.keyboard.keypad.backspace", KeyCode::NumpadBackspace),
+    (
+        "key.keyboard.keypad.left.parenthesis",
+        KeyCode::NumpadParenLeft,
+    ),
+    (
+        "key.keyboard.keypad.right.parenthesis",
+        KeyCode::NumpadParenRight,
+    ),
+    ("key.keyboard.keypad.hash", KeyCode::NumpadHash),
+    (
+        "key.keyboard.keypad.memory.store",
+        KeyCode::NumpadMemoryStore,
+    ),
+    (
+        "key.keyboard.keypad.memory.recall",
+        KeyCode::NumpadMemoryRecall,
+    ),
+    (
+        "key.keyboard.keypad.memory.clear",
+        KeyCode::NumpadMemoryClear,
+    ),
+    ("key.keyboard.keypad.memory.add", KeyCode::NumpadMemoryAdd),
+    (
+        "key.keyboard.keypad.memory.subtract",
+        KeyCode::NumpadMemorySubtract,
+    ),
+    ("key.keyboard.keypad.clear", KeyCode::NumpadClear),
+    ("key.keyboard.keypad.clear.entry", KeyCode::NumpadClearEntry),
     ("key.keyboard.menu", KeyCode::ContextMenu),
     ("key.keyboard.left.control", KeyCode::ControlLeft),
     ("key.keyboard.left.shift", KeyCode::ShiftLeft),
@@ -225,39 +282,26 @@ pub fn mouse_button(name: &str) -> Option<MouseButton> {
         _ => return None,
     })
 }
-/// InputConstants.Key.getDisplayName: one-character keys as the upper-case
-/// character, others by translation.
-pub fn display_name(key: &str) -> Text {
-    if let Some(rest) = key.strip_prefix("key.keyboard.")
-        && rest.chars().count() == 1
-    {
-        let c = rest.to_uppercase();
-        return Text::literal(c);
-    }
-    let symbol = match key {
-        "key.keyboard.minus" => Some("-"),
-        "key.keyboard.equal" => Some("="),
-        "key.keyboard.left.bracket" => Some("["),
-        "key.keyboard.right.bracket" => Some("]"),
-        "key.keyboard.backslash" => Some("\\"),
-        "key.keyboard.semicolon" => Some(";"),
-        "key.keyboard.apostrophe" => Some("'"),
-        "key.keyboard.grave.accent" => Some("`"),
-        "key.keyboard.comma" => Some(","),
-        "key.keyboard.period" => Some("."),
-        "key.keyboard.slash" => Some("/"),
-        _ => None,
+pub use horizon_client_core::key_display::display_name;
+
+/// A key event: what the layout writes on its key, without modifiers, names
+/// that key from now on (`key_display::learn_layout`), so an AZERTY player's
+/// Q key shows A.
+pub fn learn_layout(event: &winit::event::KeyEvent) {
+    use winit::keyboard::{Key, PhysicalKey};
+    use winit::platform::modifier_supplement::KeyEventExtModifierSupplement;
+    let PhysicalKey::Code(code) = event.physical_key else {
+        return;
     };
-    if let Some(s) = symbol {
-        return Text::literal(s);
+    let Some(name) = key_name(code) else {
+        return;
+    };
+    let learn = horizon_client_core::key_display::learn_layout;
+    match event.key_without_modifiers() {
+        Key::Character(text) => learn(name, &text),
+        Key::Dead(Some(c)) => learn(name, c.encode_utf8(&mut [0; 4])),
+        _ => {}
     }
-    if let Some(n) = key.strip_prefix("key.mouse.")
-        && n.parse::<u32>().is_ok()
-        && !crate::lang::has(key)
-    {
-        return Text::translate("key.mouse", &[Text::literal(n)]);
-    }
-    Text::translate(key, &[])
 }
 
 /// Current bindings by mapping name.
@@ -275,6 +319,19 @@ impl Default for KeyBinds {
         }
     }
 }
+/// Each default key once, in order: two mappings that share a default key
+/// (Pick Block and the spectator hotbar both on the middle button) are one
+/// press of it, not two.
+fn distinct<T: PartialEq>(keys: Vec<T>) -> Vec<T> {
+    let mut out = Vec::with_capacity(keys.len());
+    for k in keys {
+        if !out.contains(&k) {
+            out.push(k);
+        }
+    }
+    out
+}
+
 impl KeyBinds {
     pub fn get(&self, name: &str) -> &str {
         self.keys
@@ -320,49 +377,93 @@ impl KeyBinds {
     }
     /// The mapping a physical input triggers (first in list order).
     pub fn mapping_for(&self, key: &str) -> Option<&'static str> {
-        MAPPINGS.iter().map(|m| m.0).find(|n| self.get(n) == key)
+        self.mappings_for(key).next()
+    }
+    /// Every mapping a physical input triggers, in list order: like
+    /// `KeyMapping.set`/`click`, one key drives all the mappings bound to it.
+    pub fn mappings_for<'a>(&'a self, key: &'a str) -> impl Iterator<Item = &'static str> + 'a {
+        MAPPINGS
+            .iter()
+            .map(|m| m.0)
+            .filter(move |n| self.get(n) == key)
+    }
+    /// The mappings bound to `key` that [`KeyBinds::translate_all`] follows:
+    /// all but the debug keys. Those act only with F3 held
+    /// (`KeyboardHandler.handleDebugKeys`, `debug_keys.rs` reads the physical
+    /// key and the binding itself); their defaults (A, S, D, T, L, 1 to 4...)
+    /// would otherwise turn the key back into its old gameplay meaning.
+    fn translated_mappings<'a>(&'a self, key: &'a str) -> impl Iterator<Item = &'static str> + 'a {
+        MAPPINGS
+            .iter()
+            .filter(|m| m.2 != "debug")
+            .map(|m| m.0)
+            .filter(move |n| self.get(n) == key)
+    }
+    /// Whether a mapping (other than a debug key) whose default is `key` was
+    /// bound elsewhere.
+    fn default_moved(&self, key: &str) -> bool {
+        MAPPINGS
+            .iter()
+            .any(|(n, d, c)| *d == key && *c != "debug" && !self.is_default(n))
     }
     /// Translate a physical key into the default key of the mapping it is
     /// bound to, so game code written against vanilla defaults follows the
     /// player's bindings. `None` means the key now does nothing; mouse
-    /// mappings bound to keys come back as `Err(button)`.
+    /// mappings bound to keys come back as `Err(button)`. The first of
+    /// [`KeyBinds::translate_all`].
     pub fn translate(&self, key: KeyCode) -> Option<Result<KeyCode, MouseButton>> {
+        self.translate_all(key).into_iter().next()
+    }
+    /// The default keys of every mapping `key` is bound to (empty when it
+    /// now does nothing), so a key bound to two mappings (forward and
+    /// sprint) drives both, as `KeyMapping.set` does.
+    pub fn translate_all(&self, key: KeyCode) -> Vec<Result<KeyCode, MouseButton>> {
         let Some(name) = key_name(key) else {
-            return Some(Ok(key));
+            return vec![Ok(key)];
         };
-        if let Some(mapping) = self.mapping_for(name) {
-            let default = Self::default_of(mapping);
-            if let Some(code) = key_code(default) {
-                return Some(Ok(code));
-            }
-            return mouse_button(default).map(Err);
+        let bound: Vec<_> = self
+            .translated_mappings(name)
+            .filter_map(|mapping| {
+                let default = Self::default_of(mapping);
+                match key_code(default) {
+                    Some(code) => Some(Ok(code)),
+                    None => mouse_button(default).map(Err),
+                }
+            })
+            .collect();
+        if !bound.is_empty() {
+            return distinct(bound);
         }
         // An unbound key whose default meaning was moved elsewhere is inert.
-        if MAPPINGS
-            .iter()
-            .any(|(n, d, _)| *d == name && !self.is_default(n))
-        {
-            return None;
+        if self.default_moved(name) {
+            return Vec::new();
         }
-        Some(Ok(key))
+        vec![Ok(key)]
     }
     /// Translate a mouse button the same way (keys bound to mouse buttons).
     pub fn translate_mouse(&self, button: MouseButton) -> Option<Result<KeyCode, MouseButton>> {
+        self.translate_mouse_all(button).into_iter().next()
+    }
+    /// [`KeyBinds::translate_all`] for a mouse button.
+    pub fn translate_mouse_all(&self, button: MouseButton) -> Vec<Result<KeyCode, MouseButton>> {
         let name = mouse_name(button);
-        if let Some(mapping) = self.mapping_for(&name) {
-            let default = Self::default_of(mapping);
-            if let Some(b) = mouse_button(default) {
-                return Some(Err(b));
-            }
-            return key_code(default).map(Ok);
+        let bound: Vec<_> = self
+            .translated_mappings(&name)
+            .filter_map(|mapping| {
+                let default = Self::default_of(mapping);
+                match mouse_button(default) {
+                    Some(b) => Some(Err(b)),
+                    None => key_code(default).map(Ok),
+                }
+            })
+            .collect();
+        if !bound.is_empty() {
+            return distinct(bound);
         }
-        if MAPPINGS
-            .iter()
-            .any(|(n, d, _)| *d == name && !self.is_default(n))
-        {
-            return None;
+        if self.default_moved(&name) {
+            return Vec::new();
         }
-        Some(Err(button))
+        vec![Err(button)]
     }
     /// `AbstractContainerScreen.checkHotbarMouseClicked`: off hand, then hotbar.
     pub fn container_mouse_key(&self, button: MouseButton, creative: bool) -> Option<KeyCode> {
@@ -439,6 +540,29 @@ mod tests {
         assert_eq!(k.conflicts("key.forward"), ["key.jump"]);
     }
     #[test]
+    fn a_moved_key_keeps_no_default_action() {
+        // #3158: the debug keys (F3+A, F3+1...) share these keys' defaults,
+        // and must not hand them back their gameplay meaning.
+        let mut k = KeyBinds::default();
+        k.set("key.hotbar.1", "key.keyboard.q");
+        assert_eq!(k.translate_all(KeyCode::Digit1), []);
+        assert_eq!(
+            k.translate_all(KeyCode::KeyQ),
+            [Ok(KeyCode::KeyQ), Ok(KeyCode::Digit1)]
+        );
+        k.set("key.inventory", "key.keyboard.a");
+        k.set("key.left", "key.keyboard.e");
+        assert_eq!(k.translate_all(KeyCode::KeyA), [Ok(KeyCode::KeyE)]);
+        assert_eq!(k.translate_all(KeyCode::KeyE), [Ok(KeyCode::KeyA)]);
+        k.set("key.back", "key.keyboard.down");
+        assert_eq!(k.translate_all(KeyCode::KeyS), []);
+        // Keys left alone still act, and a moved debug key changes nothing.
+        k.set("key.debug.fpsCharts", "key.keyboard.9");
+        assert_eq!(k.translate_all(KeyCode::Digit2), [Ok(KeyCode::Digit2)]);
+        assert_eq!(k.translate_all(KeyCode::Digit9), [Ok(KeyCode::Digit9)]);
+        assert_eq!(k.translate_all(KeyCode::F3), [Ok(KeyCode::F3)]);
+    }
+    #[test]
     fn display_names() {
         assert_eq!(display_name("key.keyboard.w").plain(), "W");
         assert_eq!(display_name("key.keyboard.slash").plain(), "/");

crates/horizon-client-input/src/lib.rs

@@ -0,0 +1,14 @@
+//! The client's input layer, below gameplay and screens: key bindings and their
+//! names, toggle keys, mouse settings, controllers, the clipboard and window
+//! options. horizon-client re-exports each module under its old path
+//! (`horizon_client::keybinds`, ...).
+#![forbid(unsafe_code)]
+pub mod clipboard;
+pub mod gamepad;
+pub mod input;
+pub mod interaction_input;
+pub mod key_names;
+pub mod keybinds;
+pub mod keymapping;
+pub mod mouse;
+pub mod window;

crates/horizon-client-input/src/mouse.rs

@@ -324,6 +324,46 @@ pub fn ease_in_out(t: f64) -> f64 {
     0.5 - 0.5 * (std::f64::consts::PI * t).cos()
 }
 
+/// `MouseHandler.grabMouse` / `releaseMouse`: the mouse position is the
+/// window's centre whenever the pointer's grab state changes, so a screen
+/// opened from gameplay starts with the cursor in the middle. A release of
+/// an already free pointer (or a grab of an already grabbed one) leaves the
+/// position where it is, as vanilla does.
+pub fn mouse_position_after_grab_change(
+    grab: bool,
+    was_grabbed: bool,
+    size: [u32; 2],
+    scale: f32,
+) -> Option<(f32, f32)> {
+    if grab == was_grabbed {
+        None
+    } else {
+        Some((size[0] as f32 / 2.0 / scale, size[1] as f32 / 2.0 / scale))
+    }
+}
+
+/// `MacosUtil.setCtrlClickEmulatesRightClick`: with the option on (and only on
+/// macOS), a left click made with Control held is a right click, and so is
+/// its release, whatever Control does in between.
+#[derive(Clone, Copy, Debug, Default)]
+pub struct RightClickEmulation {
+    emulating: bool,
+}
+impl RightClickEmulation {
+    /// Whether the left button's `pressed` or released event is a right click.
+    /// `enabled` is the option on macOS.
+    pub fn is_right_click(&mut self, pressed: bool, control: bool, enabled: bool) -> bool {
+        if pressed {
+            self.emulating = enabled && control;
+        }
+        let right = self.emulating;
+        if !pressed {
+            self.emulating = false;
+        }
+        right
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -485,4 +525,44 @@ mod tests {
         assert_eq!(look.on_scroll(0.0, 0.4, false, 1.0), None);
         assert_eq!(look.on_scroll(0.0, 0.7, false, 1.0), Some((1, (0, 1))));
     }
+    #[test]
+    fn the_mouse_position_is_the_centre_when_the_grab_changes() {
+        // A grab of a free pointer and a release of a grabbed one both put
+        // the position at the window's centre (`MouseHandler.grabMouse`,
+        // `MouseHandler.releaseMouse`).
+        assert_eq!(
+            mouse_position_after_grab_change(true, false, [1920, 1080], 1.0),
+            Some((960.0, 540.0))
+        );
+        assert_eq!(
+            mouse_position_after_grab_change(false, true, [1920, 1080], 2.0),
+            Some((480.0, 270.0))
+        );
+        // Without a change of the grab state the position stays where it is.
+        assert_eq!(
+            mouse_position_after_grab_change(false, false, [1920, 1080], 1.0),
+            None
+        );
+        assert_eq!(
+            mouse_position_after_grab_change(true, true, [1920, 1080], 1.0),
+            None
+        );
+    }
+
+    #[test]
+    fn control_click_is_a_right_click_until_released() {
+        let mut e = RightClickEmulation::default();
+        // The option off, or no Control: a left click stays one.
+        assert!(!e.is_right_click(true, true, false));
+        assert!(!e.is_right_click(false, true, false));
+        assert!(!e.is_right_click(true, false, true));
+        assert!(!e.is_right_click(false, true, true));
+        // Control held at the press: the press and the release are right clicks,
+        // even when Control was let go before the release.
+        assert!(e.is_right_click(true, true, true));
+        assert!(e.is_right_click(false, false, true));
+        // The next left click is its own.
+        assert!(!e.is_right_click(true, false, true));
+        assert!(!e.is_right_click(false, false, true));
+    }
 }