ci: lock the dependency set, verify the build inputs on PRs, harden the jobs

- `--locked` on every cargo invocation (ci.yml clippy/test/build, both
  Dockerfile builds). The version bump edits Cargo.lock by hand, so a stale
  lock must fail loudly instead of being silently re-resolved: CI would
  otherwise test a different dependency set than the one committed — and than
  the one the released image is built from.
- docker.yml: build the image (no push, no registry login, read-only build
  cache) on pull requests touching the build inputs. The Dockerfile's
  stub-source machinery, the ffmpeg download and the entrypoint previously
  only ran at release time. Also: a release tag must equal both crate versions
  before anything is built (the binary carries no version, so `v1.5.1` with
  manifests at 1.5.0 used to publish silently wrong tags), `FFMPEG_URL`/
  `FFMPEG_SHA256` are taken from repository variables when set, and the
  unused `setup-qemu-action` step is gone (single-arch build; the comment says
  what arm64 would need).
- ci.yml: `concurrency` cancels superseded runs, `permissions: contents: read`,
  `RUST_BACKTRACE=1`, job timeouts, and a release-profile build of the same
  package the Dockerfile builds (the profile was otherwise never compiled
  before a merge). The `live` job narrows to `-p x-media`: every network- or
  secret-gated test lives there, and the bot crate's offline suite already ran
  in the `test` job. Timeout is 45 min because the release build is cold on
  the first run — a timeout there would kill the job before rust-cache could
  save its cache, leaving every later run cold too.
- Actions pinned to commit SHAs (Dependabot keeps them current);
  `dtolnay/rust-toolchain` stays on its channel ref by design.
- .github/dependabot.yml: crates (patch bumps grouped), action pins, Docker
  base images — the audit gate reports advisories, this is what moves them.
- tokio's `sync` feature is now declared instead of arriving transitively via
  teloxide; `.dockerignore` drops docs and markdown.

Verified locally: `cargo fmt --check`, `cargo clippy --workspace
--all-targets --locked`, `cargo test --workspace --locked` (70 + 69 pass),
`cargo build --release --locked` (6m03s cold, the 15.9 MB stripped binary
starts and registers 10 commands), the tag/version gate against both a
matching and a mismatching tag, and YAML parsing of all three workflow files.

.dockerignore

@@ -26,6 +26,10 @@
 *.db
 LICENSE
 README.md
+# Documentation and scratch files: the build only ever reads the manifests,
+# `crates/` and the entrypoint script.
+docs/
+*.md
 data/
 cert/
 nginx-certs/

.github/dependabot.yml

@@ -0,0 +1,32 @@
+version: 2
+
+# Pairs with the `actions-rust-lang/audit` gate in ci.yml: the gate reports
+# advisories in Cargo.lock, this is what actually moves the dependencies.
+# Patch bumps are batched into one PR; minor/major stay separate so they get
+# reviewed and tested individually.
+updates:
+  - package-ecosystem: cargo
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    groups:
+      cargo-patch:
+        applies-to: version-updates
+        patterns: ['*']
+        update-types: ['patch']
+
+  # The workflow actions are pinned to commit SHAs; that pin is what makes
+  # bumping them a manual chore, so let the bot do it.
+  - package-ecosystem: github-actions
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+
+  # The Dockerfile's base images (rust:1-bookworm, debian:bookworm-slim).
+  - package-ecosystem: docker
+    directory: /
+    schedule:
+      interval: monthly
+    open-pull-requests-limit: 3

.github/workflows/ci.yml

@@ -4,15 +4,19 @@ name: CI
 # job that exercises the real source sites and the token-gated pixiv tests.
 #
 # Layering:
-#   test  — fmt + clippy + the full offline unit suite + cargo-audit
+#   test  — fmt + clippy + the full offline unit suite + a release-profile
-#           dependency gate. Runs on every push and PR, including forks
+#           build + cargo-audit dependency gate. Runs on every push and PR,
-#           (it needs no secrets).
+#           including forks (it needs no secrets).
 #   live  — the #[ignore]d live-network tests plus the pixiv tests that are
 #           gated on PIXIV_REFRESH_TOKEN. Runs on schedule / manual dispatch
 #           / tag pushes only, because pull requests from forks cannot read
 #           repository secrets. continue-on-error keeps a flaky external site
 #           from blocking, while the run still records the outcome.
 #
+# Every action is pinned to a commit SHA (Dependabot keeps the pins current);
+# `dtolnay/rust-toolchain` deliberately stays on its channel ref, because the
+# ref itself is what selects the toolchain (`@stable` = install stable).
+#
 # Test gating convention (keep in sync with AGENTS.md "Testing & QA"):
 #   - pure unit tests: plain #[test] / #[tokio::test], always run.
 #   - live-network tests: #[ignore = "live network: ..."], only run here.
@@ -28,44 +32,75 @@ on:
     - cron: '0 3 * * 1'
   workflow_dispatch:
 
+permissions:
+  contents: read
+
+# A newer push to the same ref supersedes the older run; without this every
+# intermediate commit of a PR branch keeps a runner busy to completion.
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+env:
+  # Panicking tests print their backtrace; free when nothing fails.
+  RUST_BACKTRACE: 1
+
 jobs:
   test:
     runs-on: ubuntu-latest
+    # Generous on purpose: the release-profile build below is cold on the very
+    # first run (thin LTO + codegen-units = 1 across every dependency), and a
+    # timeout there would kill the job *before* rust-cache saves its cache —
+    # leaving every later run cold again.
+    timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
       - uses: dtolnay/rust-toolchain@stable
         with:
           components: clippy, rustfmt
-      - uses: Swatinem/rust-cache@v2
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2
+      # `--locked` on every cargo invocation: the version bump edits
+      # Cargo.lock by hand (AGENTS.md), so a stale lock must fail here instead
+      # of being silently re-resolved — otherwise CI tests a different
+      # dependency set than the one committed, and than the one the released
+      # image is built from.
       - name: Check formatting
         run: cargo fmt --check
       - name: Lint (deny warnings)
-        run: cargo clippy --workspace --all-targets -- -D warnings
+        run: cargo clippy --workspace --all-targets --locked -- -D warnings
       - name: Run offline tests
-        run: cargo test --workspace
+        run: cargo test --workspace --locked
+      # The release profile (lto/strip/codegen-units=1, overflow checks off)
+      # was otherwise only exercised by the Docker build on master/tag. Same
+      # package the Dockerfile builds; the cache keeps it cheap after the
+      # first run.
+      - name: Build release profile
+        run: cargo build --release --locked -p xmedia-bot
       # Dependency vulnerability gate: fails the build when a crate in
       # Cargo.lock has an unfixed security advisory. Unmaintained/unsound
       # *warnings* (dotenv, proc-macro-error2, anyhow transitive) do not fail
       # the build by default; the advisory DB is cached across runs.
       - name: Audit dependencies
-        uses: actions-rust-lang/audit@v1
+        uses: actions-rust-lang/audit@72c09e02f132669d52284a3323acdb503cfc1a24 # v1
 
   live:
     needs: test
     if: github.event_name == 'schedule' || github.event_name == 'workflow_dispatch' || startsWith(github.ref, 'refs/tags/v')
     runs-on: ubuntu-latest
+    timeout-minutes: 30
     continue-on-error: true
     env:
       PIXIV_REFRESH_TOKEN: ${{ secrets.PIXIV_REFRESH_TOKEN }}
       TWITTER_AUTH_TOKEN: ${{ secrets.TWITTER_AUTH_TOKEN }}
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
       - uses: dtolnay/rust-toolchain@stable
-      - uses: Swatinem/rust-cache@v2
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2
-      # Full suite: with the secret present, the pixiv token-gated tests run;
+      # Everything network- or secret-gated lives in x-media, and the bot
-      # without it they skip themselves. Live tests stay #[ignore]d here.
+      # crate's suite (MockSender + tempdir stores, no network) already ran in
+      # the `test` job — rebuilding it here bought nothing.
       - name: Run token-gated tests
-        run: cargo test --workspace
+        run: cargo test -p x-media --locked
       # The live-network tests, by the "live" name filter (all #[ignore]d).
       - name: Run live-network tests
-        run: cargo test --workspace -- --ignored live
+        run: cargo test -p x-media --locked -- --ignored live

.github/workflows/docker.yml

@@ -1,28 +1,75 @@
 name: Build Docker Image
 
+# Release builds (master / v* tags) plus a build-only check on pull requests
+# that touch anything the image depends on — the Dockerfile's stub-source
+# machinery, the ffmpeg download and the entrypoint are exactly the parts that
+# would otherwise break only at release time.
+#
+# Actions are pinned to commit SHAs (Dependabot keeps the pins current).
+
 on:
   push:
     tags:
       - v*
     branches:
       - master
+  pull_request:
+    paths:
+      - Dockerfile
+      - docker-entrypoint.sh
+      - .dockerignore
+      - Cargo.toml
+      - Cargo.lock
+      - .github/workflows/docker.yml
+      - 'crates/**/Cargo.toml'
 
 env:
   APP_NAME: telegram-twitter-media-bot
   DOCKERHUB_REPO: yoursfunny/telegram-twitter-media-bot
 
+permissions:
+  contents: read
+
+# Serialize runs per ref. Never cancel in progress: a killed run would drop a
+# half-finished image push.
+concurrency:
+  group: docker-${{ github.ref }}
+  cancel-in-progress: false
+
 jobs:
   # A tag push and a branch push to the same commit fire two workflow runs;
   # build only once. Tag runs always build; master runs build only when the
   # pushed commit is not already tagged (the tag run covers it).
   should-build:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
     outputs:
       build: ${{ steps.check.outputs.build }}
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
         with:
           fetch-depth: 0
+      # A release tag is the version claim: the manifests are bumped by hand,
+      # so `v1.5.1` with `Cargo.toml` still at 1.5.0 would publish an image
+      # whose tag lies about what is inside it (the binary carries no version).
+      - name: Verify the tag matches both crate versions
+        if: startsWith(github.ref, 'refs/tags/v')
+        shell: bash
+        run: |
+          tag="${GITHUB_REF_NAME#v}"
+          status=0
+          for manifest in crates/x-media/Cargo.toml crates/xmedia-bot/Cargo.toml; do
+            # tr -d '\r': a CRLF checkout (core.autocrlf on Windows) would
+            # otherwise yield "1.5.0\r" and false-fail every tag.
+            version="$(sed -n 's/^version = "\(.*\)"/\1/p' "$manifest" | head -1 | tr -d '\r')"
+            if [ "$version" != "$tag" ]; then
+              echo "::error file=$manifest::$manifest is at $version but the tag is v$tag"
+              status=1
+            else
+              echo "$manifest: $version matches v$tag"
+            fi
+          done
+          exit "$status"
       - id: check
         shell: bash
         run: |
@@ -37,10 +84,11 @@ jobs:
     needs: should-build
     if: needs.should-build.outputs.build == 'true'
     runs-on: ubuntu-latest
+    timeout-minutes: 60
     steps:
       - name: Docker meta
         id: meta
-        uses: docker/metadata-action@v6
+        uses: docker/metadata-action@dc802804100637a589fabce1cb79ff13a1411302 # v6
         with:
           images: ${{ env.DOCKERHUB_REPO }}
           tags: |
@@ -49,15 +97,15 @@ jobs:
             type=semver,pattern={{major}}.{{minor}}
             type=semver,pattern={{major}}
             type=sha
-      -
-        name: Set up QEMU
-        uses: docker/setup-qemu-action@v4
       -
         name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v4
+        uses: docker/setup-buildx-action@f87e5991a6d7451dcb8d9637bfbc97413f497069 # v4
+      # Pull requests build the image to prove the Dockerfile still works, but
+      # must not read registry credentials (fork PRs have none).
       -
         name: Login to Docker Hub
-        uses: docker/login-action@v4
+        if: github.event_name != 'pull_request'
+        uses: docker/login-action@dbcb813823bdd20940b903addbd779551569679f # v4
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
@@ -66,15 +114,26 @@ jobs:
       # stage's layers so the cargo-deps and ffmpeg layers are restored
       # instead of re-downloaded/recompiled. The scope must be pinned to a
       # fixed string: the gha backend defaults to the current git ref, which
-      # would give every new tag a cold cache on release builds.
+      # would give every new tag a cold cache on release builds. PR runs only
+      # read it (cache-to is empty) so they cannot evict the release cache.
+      #
+      # FFMPEG_URL/FFMPEG_SHA256 come from repository variables when set, so a
+      # release can pin an exact ffmpeg build (the Dockerfile default follows
+      # the project's `/redirect/latest/` URL, which has no sha256 sidecar).
+      #
+      # Single-arch (amd64) on purpose: adding arm64 means re-adding
+      # `docker/setup-qemu-action`, `platforms: linux/amd64,linux/arm64`, and
+      # parameterizing FFMPEG_URL by $TARGETARCH in the Dockerfile.
       -
         name: Build and push
-        uses: docker/build-push-action@v7
+        uses: docker/build-push-action@c3c9e263c25d99ce0380d002d59b67737d91b0dc # v7
         with:
-          push: true
+          push: ${{ github.event_name != 'pull_request' }}
           build-args: |
             APP_NAME=${{ env.APP_NAME }}
+            FFMPEG_URL=${{ vars.FFMPEG_URL || 'https://ffmpeg.martin-riedl.de/redirect/latest/linux/amd64/release/ffmpeg.zip' }}
+            FFMPEG_SHA256=${{ vars.FFMPEG_SHA256 }}
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha,scope=tgxmb-build
-          cache-to: type=gha,mode=max,scope=tgxmb-build
+          cache-to: ${{ github.event_name != 'pull_request' && 'type=gha,mode=max,scope=tgxmb-build' || '' }}

AGENTS.md

@@ -81,7 +81,7 @@ Docker: `docker build -t tgxmb .` then `docker run --rm -d --name tgxmb --env-fi
 | `Dockerfile` | Multi-stage: cached dep layer via stub sources + `touch *.rs` mtime bump (cargo's freshness is mtime-based and `cargo clean -p` removes 0 files — the touch is what forces the real sources to rebuild while deps stay cached), static ffmpeg from ffmpeg.martin-riedl.de (`FFMPEG_URL` arg, optional `FFMPEG_SHA256` checksum, `unzip -t` integrity check), `debian:bookworm-slim` runtime, entrypoint. Runtime ships **no libssl/libcrypto/CA bundle** — rustls webpki-roots handles all TLS, and the static ffmpeg only processes local files (downloads go through reqwest) |
 | `docker-entrypoint.sh` | Privilege drop: `useradd` with `LOCAL_USER_ID` (default 9001) + `setpriv` (no gosu on bookworm-slim) |
 | `docker-compose.yml.example` | Deployment env reference (real `docker-compose.yml` is gitignored). Ships nginx-proxy + acme-companion: webhook mode needs TLS termination in front (teloxide's axum listener is HTTP-only; `WEBHOOK_CERT` only feeds `set_webhook`), bot exposes `VIRTUAL_HOST`/`VIRTUAL_PORT` on the shared `proxy` network, no host port; container names `nginx-proxy`/`acme-companion`/`tgxmb`, start order via `depends_on` (proxy → acme → bot) |
-| `.github/workflows/docker.yml` | CI: build+push to Docker Hub on tag `v*`/master; **no test step**; buildx gha cache (`cache-from`/`cache-to`, scope `tgxmb-build`, `mode=max`) so cargo deps + ffmpeg layers are restored across runs |
+| `.github/workflows/docker.yml` | CI: build+push to Docker Hub on tag `v*`/master, plus a build-only check on PRs touching the build inputs; **no test step**; verifies a release tag matches both crate versions; buildx gha cache (`cache-from` always, `cache-to` except on PRs, scope `tgxmb-build`, `mode=max`) so cargo deps + ffmpeg layers are restored across runs; `FFMPEG_URL`/`FFMPEG_SHA256` come from repo variables when set |
 | `README.md` | Feature docs + command table (Chinese) |
 
 ## Runtime/Tooling Preferences
@@ -89,7 +89,7 @@ Docker: `docker build -t tgxmb .` then `docker run --rm -d --name tgxmb --env-fi
 - **Rust, stable, edition 2024**, workspace resolver 3. No `rust-version`/MSRV pin, no `rust-toolchain.toml` — recent stable is assumed. No nightly features.
 - Package manager: **Cargo** (workspace with path dep `x-media` ← `xmedia-bot`). No `[workspace.package]`/shared deps — each crate lists deps independently.
 - **TLS is rustls end-to-end** (no native-tls/openssl in the tree, no libssl in the Docker runtime image): `teloxide` is declared `default-features = false` with `["webhooks-axum", "macros", "rustls", "ctrlc_handler"]` (the removed `default` also carried `native-tls` and `ctrlc_handler` — the latter must stay); x-media's reqwest is `default-features = false` with `["json", "rustls-tls"]` (webpki-roots baked in, so the image ships no CA bundle). One reqwest 0.12.28 in the lock.
-- **Versioning**: bump the version in all three places (`crates/x-media/Cargo.toml`, `crates/xmedia-bot/Cargo.toml`, `Cargo.lock`) and **keep `README.md`, `README.en.md` and `AGENTS.md` in sync with the code on every bump**, then commit (`chore: bump version to X.Y.Z`), create an annotated tag `vX.Y.Z`, and push branch + tag (the tag push triggers the Docker Hub build).
+- **Versioning**: bump the version in all three places (`crates/x-media/Cargo.toml`, `crates/xmedia-bot/Cargo.toml`, `Cargo.lock`) and **keep `README.md`, `README.en.md` and `AGENTS.md` in sync with the code on every bump**, then commit (`chore: bump version to X.Y.Z`), create an annotated tag `vX.Y.Z`, and push branch + tag (the tag push triggers the Docker Hub build). The tag must equal both crate versions: `.github/workflows/docker.yml` verifies that before building, and `--locked` verifies the lock file.
 - Config is **environment-variable driven** (dotenv loads `.env`, gitignored; no `.env.example` exists). Key vars: `TELOXIDE_TOKEN` (required), `PIXIV_REFRESH_TOKEN`, `TWITTER_AUTH_TOKEN` (optional; x.com `auth_token` cookie — enables the logged-in GraphQL fallback that fetches NSFW tweets syndication withholds), `BOT_ADMIN` (comma-separated ids), `EDIT_MESSAGE_TTL_SECONDS` (default 86400), `LINK_CACHE_TTL_SECONDS` (default 604800), `DATA_DIR` (default `data`, CWD-relative; the SQLite dir, auto-created), `WEBHOOK`/`WEBHOOK_URL`/`WEBHOOK_LISTEN`/`WEBHOOK_PORT`/`WEBHOOK_CERT`/`WEBHOOK_SECRET_TOKEN` (webhook mode requires URL/listen/port, `.expect`ed; `WEBHOOK_CERT` is Telegram-facing self-signed validation only — TLS must be terminated by a reverse proxy), `RUST_LOG`, `TELOXIDE_PROXY`, `LOCAL_USER_ID` (entrypoint only).
 - SQLite via `rusqlite` with `bundled` feature (no system libsqlite needed). DB file `$DATA_DIR/task_queue.db` (default `data/task_queue.db`, CWD-relative — run from the workspace root, or `/app` in Docker; set `DATA_DIR` to pin state anywhere). Mount `./data` and `./cert` volumes.
 - `.gitattributes` enforces LF for `*.sh` (CRLF breaks shebangs in containers). `.gitignore`: `.env`, `data/`, `cert/`, `docker-compose.yml`, `/target`, `.idea/`.
@@ -101,6 +101,6 @@ Docker: `docker build -t tgxmb .` then `docker run --rm -d --name tgxmb --env-fi
 - No mocking framework anywhere (no mockito/wiremock/mockall). Conventions: pure-function units (regex parsing, serde round-trips, chunking, retry math) tested synchronously; async tests use real dependencies — file-backed SQLite via `tempfile` (`queue.rs::new_queue()` helper), live network fetches.
 - Live-network tests exist in `site/twitter/interface.rs` (5), `site/bsky/interface.rs` (2), `site/misskey/interface.rs` (1), `site/pixiv/api.rs` (1); `photo.rs` adds one `#[ignore = "heavy: …"]` test. `site/mod.rs` also has a **token-gated but not `#[ignore]`d** pixiv download test (`download_media_pixiv_original_with_referer`): it hits `i.pximg.net` whenever `PIXIV_REFRESH_TOKEN` is set, so a local `cargo test --workspace` is not fully offline and can flake on a pixiv CDN body timeout. Test gating convention (enforced by `.github/workflows/ci.yml`): pure unit tests always run; live-network tests carry `#[ignore = "live network: ..."]` (run via `cargo test --workspace -- --ignored live`); token-gated pixiv tests early-return when `PIXIV_REFRESH_TOKEN` is absent **or empty** (an unset GitHub secret arrives as `""` — `is_err()` alone would run them tokenless and fail). Run the full offline suite with `cargo test --workspace`.
 - Fixtures are inline `serde_json::json!` builder fns (`fixture()`, `thread_json()`, `illust_json()`), not files. The shared `CLIENT` sets `pool_max_idle_per_host(0)` under `#[cfg(test)]` to avoid cross-runtime `DispatchGone`.
-- **CI** — `.github/workflows/ci.yml` runs `cargo fmt --check` + `cargo clippy --workspace --all-targets -- -D warnings` + `cargo test --workspace` + a `actions-rust-lang/audit` dependency-vulnerability gate (offline, no secrets, on every push/PR) and a `live` job (schedule/manual/tag only, `PIXIV_REFRESH_TOKEN`/`TWITTER_AUTH_TOKEN` from secrets, `continue-on-error`) for the `#[ignore]`d live + token tests. `.github/workflows/docker.yml` builds/pushes the image only.
+- **CI** — `.github/workflows/ci.yml` (actions pinned to commit SHAs, `--locked` on every cargo invocation, `concurrency` cancels superseded runs, `RUST_BACKTRACE=1`) runs `cargo fmt --check` + `cargo clippy --workspace --all-targets --locked -- -D warnings` + `cargo test --workspace --locked` + a release-profile `cargo build --release --locked` + an `actions-rust-lang/audit` dependency-vulnerability gate (offline, no secrets, on every push/PR) and a `live` job (schedule/manual/tag only, `-p x-media` since every network/secret-gated test lives there, `continue-on-error`) for the `#[ignore]`d live + token tests. `.github/workflows/docker.yml` builds and pushes the image on master/tag and runs a **build-only check on pull requests touching the build inputs** (`Dockerfile`, entrypoint, manifests, `.dockerignore`); a release tag must match both crate versions or the build stops, and `FFMPEG_URL`/`FFMPEG_SHA256` are taken from repository variables when set (a release can pin an exact ffmpeg build). `.github/dependabot.yml` keeps crates, the pinned actions and the Docker base images current.
 - Untested and hard to test without a mock seam: `main.rs`, `config.rs`, `db.rs`, `handlers/statics.rs`, `media_sender.rs` (holds the `MockSender` itself); in `x-media`: `media.rs`, `lib.rs`, all `model.rs`. The `commands.rs` *executor* needs a real `Bot` (only its pure report builder is tested). Everything else — `handlers/{mod,callback,inline,urls}.rs`, `send/*`, `ctx.rs`, `state.rs`, `queue.rs`, `link_cache.rs`, `rate_limit.rs` — is driven through `TestStores`/`ctx::test_support` and the scripted `MockSender`.
 - No coverage tracking.

Dockerfile

@@ -11,6 +11,8 @@ ARG APP_NAME=telegram-twitter-media-bot
 # runners. `/redirect/latest/` floats to the newest release build; each build
 # also ships a .sha256. Swap `amd64` for `arm64` when building arm64 images.
 ARG FFMPEG_URL=https://ffmpeg.martin-riedl.de/redirect/latest/linux/amd64/release/ffmpeg.zip
+# Arm64 images need this URL swapped for the `linux/arm64` build (currently
+# hardcoded amd64; the workflow builds amd64 only — see docker.yml).
 # Optional sha256 of ffmpeg.zip (pinned releases only): set to verify the
 # download. The mirror publishes .sha256 sidecars next to pinned builds, e.g.
 # https://ffmpeg.martin-riedl.de/download/linux/amd64/<id>_9.0/ffmpeg.zip.sha256
@@ -28,7 +30,7 @@ COPY crates/xmedia-bot/Cargo.toml crates/xmedia-bot/Cargo.toml
 RUN mkdir -p crates/x-media/src crates/xmedia-bot/src \
     && printf 'fn main() {}\n' > crates/xmedia-bot/src/main.rs \
     && : > crates/x-media/src/lib.rs \
-    && cargo build --release -p xmedia-bot
+    && cargo build --release --locked -p xmedia-bot
 
 # 2. Static ffmpeg next (cached unless FFMPEG_URL changes), so source edits
 #    never re-download it. The zip contains a single `ffmpeg` binary at the
@@ -51,7 +53,7 @@ RUN wget -q -O /tmp/ffmpeg.zip "$FFMPEG_URL" \
 #    removes 0 files and the stub binary silently ships.)
 COPY crates/ ./crates/
 RUN find crates -type f -name '*.rs' -exec touch {} + \
-    && cargo build --release -p xmedia-bot
+    && cargo build --release --locked -p xmedia-bot
 
 # ---------- runtime stage ----------
 FROM debian:bookworm-slim

crates/xmedia-bot/Cargo.toml

@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 teloxide = { version = "0.17", default-features = false, features = ["webhooks-axum", "macros", "rustls", "ctrlc_handler"] }
-tokio = { version = "1.40", features = ["rt-multi-thread", "macros", "time"] }
+tokio = { version = "1.40", features = ["rt-multi-thread", "macros", "time", "sync"] }
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 log = "0.4"