diff --git a/.github/actions/rust-setup/action.yml b/.github/actions/rust-setup/action.yml
index f50e1873..6e4e244c 100644
--- a/.github/actions/rust-setup/action.yml
+++ b/.github/actions/rust-setup/action.yml
@@ -34,12 +34,12 @@ runs:
     # `@master`, which floats the ACTION's own implementation and can change CI behavior out from
     # under the pinned Rust toolchain input below without warning — caught in PR review). The
     # `toolchain:` input still wins over whatever default this ref's snapshot implies.
-    - uses: dtolnay/rust-toolchain@1.96
+    - uses: dtolnay/rust-toolchain@2fe4ca74464c5902a4f6e302d0a619b4ea911ccc # 1.96
       with:
         toolchain: ${{ inputs.toolchain }}
         components: ${{ inputs.components }}
         targets: ${{ inputs.targets }}
-    - uses: Swatinem/rust-cache@v2
+    - uses: Swatinem/rust-cache@e18b497796c12c097a38f9edb9d0641fb99eee32 # v2
       with:
         key: ${{ inputs.cache-key-suffix }}
     - name: Install Linux frontend system deps
diff --git a/.github/workflows/antigravity-review.yml b/.github/workflows/antigravity-review.yml
index fa3d9d0a..32ba8cf4 100644
--- a/.github/workflows/antigravity-review.yml
+++ b/.github/workflows/antigravity-review.yml
@@ -63,7 +63,7 @@ jobs:
       # branch throughout. Consequence worth knowing: a PR that edits the reviewer or the
       # style guide is reviewed by the version already on the default branch until it merges.
       - name: Check out repo (for the style guide + scripts)
-        uses: actions/checkout@v7
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
         with:
           ref: ${{ github.event.repository.default_branch }}
           # Not `fetch-depth: 0`: the large-diff fallback fetches exactly the two refs it
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b8713ffb..a9388d45 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -29,8 +29,10 @@ jobs:
     outputs:
       code: ${{ steps.filter.outputs.code }}
     steps:
-      - uses: actions/checkout@v7
-      - uses: dorny/paths-filter@v3
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
+      - uses: dorny/paths-filter@d1c1ffe0248fe513906c8e24db8ea791d46f8590 # v3
         id: filter
         with:
           filters: |
@@ -88,7 +90,9 @@ jobs:
       CARGO_HTTP_MULTIPLEXING: "false"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       # fmt/clippy only ever check the HOST target here (no `--target` is ever passed to either
       # command in this job) — installing the wasm32/thumbv7em cross targets bought nothing but
       # setup time on every single PR push. Only `no_std` (which actually cross-compiles) needs
@@ -184,7 +188,9 @@ jobs:
       CARGO_HTTP_MULTIPLEXING: "false"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       - uses: ./.github/actions/rust-setup
         with:
           cache-key-suffix: test-light
@@ -206,7 +212,9 @@ jobs:
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       # Same rationale as `lint`: neither fmt nor clippy nor `cargo test` cross-compiles here, so
       # no extra targets are installed.
       - uses: ./.github/actions/rust-setup
@@ -265,7 +273,9 @@ jobs:
           - rustysnes-cart
           - rustysnes-core
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       - uses: ./.github/actions/rust-setup
         with:
           targets: thumbv7em-none-eabihf
@@ -285,7 +295,9 @@ jobs:
       CARGO_HTTP_MULTIPLEXING: "false"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       # The `rustysnes-core` `headless_frame` bench is chip-stack-only (no wgpu/winit/egui), so
       # no Linux frontend system deps are needed here (unlike `lint`/`full-test`).
       - uses: ./.github/actions/rust-setup
@@ -301,7 +313,9 @@ jobs:
     if: needs.setup.outputs.mode != 'skip'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       - uses: ./.github/actions/rust-setup
         with:
           cache-key-suffix: accuracysnes
diff --git a/.github/workflows/ios.yml b/.github/workflows/ios.yml
index 6b177d95..50415b1d 100644
--- a/.github/workflows/ios.yml
+++ b/.github/workflows/ios.yml
@@ -40,7 +40,9 @@ jobs:
       CARGO_NET_RETRY: "10"
       CARGO_HTTP_MULTIPLEXING: "false"
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       - uses: ./.github/actions/rust-setup
         with:
           # `dtolnay/rust-toolchain` ignores its OWN `toolchain:`/`components:`/`targets:` inputs
diff --git a/.github/workflows/pgo.yml b/.github/workflows/pgo.yml
index 86a7a32b..4610d6eb 100644
--- a/.github/workflows/pgo.yml
+++ b/.github/workflows/pgo.yml
@@ -73,7 +73,9 @@ jobs:
       promotable: ${{ steps.gate.outputs.promotable }}
       speedup_pct: ${{ steps.gate.outputs.speedup_pct }}
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
 
       # `components: llvm-tools-preview` is listed for documentation, but the EFFECTIVE source is
       # `rust-toolchain.toml` (which now includes it) -- `dtolnay/rust-toolchain` silently ignores
@@ -173,7 +175,7 @@ jobs:
 
       - name: Upload promoted PGO binary
         if: steps.gate.outputs.promotable == 'true'
-        uses: actions/upload-artifact@v7
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
         with:
           name: rustysnes-pgo-${{ steps.triple.outputs.triple }}
           path: target/${{ steps.triple.outputs.triple }}/release/rustysnes
@@ -194,7 +196,9 @@ jobs:
     permissions:
       contents: read
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       - uses: ./.github/actions/rust-setup
         with:
           components: llvm-tools-preview
@@ -282,7 +286,7 @@ jobs:
 
       - name: Upload BOLT binary
         if: steps.bolt_probe.outputs.have_bolt == 'true'
-        uses: actions/upload-artifact@v7
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
         with:
           name: rustysnes-bolt-${{ steps.triple.outputs.triple }}
           path: target/${{ steps.triple.outputs.triple }}/release/rustysnes
diff --git a/.github/workflows/release-auto.yml b/.github/workflows/release-auto.yml
index e1c88818..477b72ba 100644
--- a/.github/workflows/release-auto.yml
+++ b/.github/workflows/release-auto.yml
@@ -53,17 +53,34 @@ jobs:
       should_release: ${{ steps.decide.outputs.should_release }}
       tag: ${{ steps.decide.outputs.tag }}
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
         with:
           # Build the release from the exact commit CI went green on. Full history so the
-          # annotated-tag creation and the `git ls-remote` existence check both have what they
-          # need (a shallow clone's tag/ref visibility isn't reliable here).
+          # annotated-tag creation and the tag-existence check both have what they need (a shallow
+          # clone's tag/ref visibility isn't reliable here).
           ref: ${{ github.event.workflow_run.head_sha }}
           fetch-depth: 0
+          # DELIBERATELY NOT `persist-credentials: false`, and the only checkout in the repository
+          # that keeps the token. Every other one was hardened in `v1.26.0` because checkout writes
+          # the workflow `GITHUB_TOKEN` into `.git/config`, where anything the job then executes
+          # from the tree can read it.
+          #
+          # This job is the exception because it genuinely needs it: it creates an annotated tag and
+          # `git push origin "$TAG"` (below), which authenticates through exactly that credential.
+          # The sibling project's audit concluded no job needed the token; that conclusion does NOT
+          # transfer here, which is why this was audited per-site rather than applied blanket.
+          #
+          # The exposure is bounded by the trigger: `workflow_run` on a completed CI run of `main`,
+          # never a pull request, so the tree this job executes is already-reviewed code.
 
       - name: Decide whether a closed-out version needs releasing
         id: decide
         shell: bash
+        env:
+          # Required by the `gh api` tag-existence check below. `gh` errors out without it rather
+          # than falling back to the ambient credential, and this step previously used only plain
+          # `git`, so it had no token of its own. Same form as the release steps further down.
+          GH_TOKEN: ${{ github.token }}
         run: |
           set -euo pipefail
           # ANY non-blank content under [Unreleased] (not just a "- " bullet -- a stray heading
@@ -93,7 +110,26 @@ jobs:
           echo "tag=${tag}" >> "$GITHUB_OUTPUT"
           echo "version=${version}" >> "$GITHUB_OUTPUT"
           echo "header=${header}" >> "$GITHUB_OUTPUT"
-          if git ls-remote --exit-code --tags origin "refs/tags/${tag}" >/dev/null 2>&1; then
+          # FAIL CLOSED. This was `git ls-remote --exit-code --tags origin "refs/tags/${tag}"`,
+          # which collapses THREE outcomes into two: tag present (0), tag absent (2), and lookup
+          # failed (non-zero, various). Reading any non-zero as "absent" means a transient network
+          # blip, an auth hiccup, or a rate limit sends an ALREADY-RELEASED version down the
+          # `should_release=true` path — re-tagging a published release, which
+          # `to-dos/ROADMAP.md`'s release ceremony treats as immutable.
+          #
+          # `git/matching-refs` is chosen over `git/ref/tags/<tag>` deliberately: it answers
+          # "absent" with HTTP 200 and an empty array, so a genuine miss can never be confused with
+          # an error and no error-body parsing is needed. It matches by PREFIX, though, so the exact
+          # ref is compared in `jq` — that is not theoretical, `v1.2` prefix-matches several real
+          # tags while exact-matching none.
+          #
+          # Every failure path aborts the job (the script runs under `set -euo pipefail`) rather
+          # than resolving to a release decision.
+          if ! matching="$(gh api "repos/${GITHUB_REPOSITORY}/git/matching-refs/tags/${tag}")"; then
+            echo "::error::Tag lookup for ${tag} failed. Refusing to guess whether it exists."
+            exit 1
+          fi
+          if printf '%s' "$matching" | jq -e --arg ref "refs/tags/${tag}" 'any(.[]; .ref == $ref)' >/dev/null; then
             echo "Tag ${tag} already exists -- nothing to release."
             echo "should_release=false" >> "$GITHUB_OUTPUT"
           else
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index cc4b2878..15527b20 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -43,13 +43,14 @@ jobs:
       # `push` trigger, where `github.ref_name` is already the pushed tag).
       TAG: ${{ inputs.tag || github.ref_name }}
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
         with:
+          persist-credentials: false
           ref: ${{ env.TAG }}
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: dtolnay/rust-toolchain@4cda84d5c5c54efe2404f9d843567869ab1699d4 # stable
         with:
           targets: ${{ matrix.target }}
-      - uses: Swatinem/rust-cache@v2
+      - uses: Swatinem/rust-cache@e18b497796c12c097a38f9edb9d0641fb99eee32 # v2
         with:
           key: release-${{ matrix.target }}
       - name: Install Linux frontend system deps
diff --git a/.github/workflows/security.yml b/.github/workflows/security.yml
index 33b65ead..138433a1 100644
--- a/.github/workflows/security.yml
+++ b/.github/workflows/security.yml
@@ -51,12 +51,14 @@ jobs:
     name: Dependency Audit
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       # Install the PREBUILT binary, never `cargo install` (build-from-source): the repo pins
       # rustc 1.96, but a from-source cargo-audit build can need a newer toolchain than that to
       # COMPILE. The prebuilt binary runs fine under any toolchain -- it only parses Cargo.lock,
       # it never compiles this project.
-      - uses: taiki-e/install-action@v2
+      - uses: taiki-e/install-action@6a1bd70eaac3c8bdf093356838d7ee09fda951cf # v2
         with:
           tool: cargo-audit
       - run: cargo audit
@@ -74,10 +76,12 @@ jobs:
     name: Cargo Deny Check
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       # Same rationale as the audit job: the prebuilt binary avoids needing a newer toolchain
       # than the repo's pinned 1.96 just to build the checker itself. Policy lives in `deny.toml`.
-      - uses: taiki-e/install-action@v2
+      - uses: taiki-e/install-action@6a1bd70eaac3c8bdf093356838d7ee09fda951cf # v2
         with:
           tool: cargo-deny
       - run: cargo deny check
@@ -112,12 +116,14 @@ jobs:
     # indistinguishably from a real finding.
     timeout-minutes: 180
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       # cargo-fuzz needs nightly (`-Z sanitizer=address`); the project pins 1.96 stable in
       # `rust-toolchain.toml`. Installing nightly alongside it, and invoking it explicitly as
       # `+nightly`, keeps the pin authoritative for every other job.
-      - uses: dtolnay/rust-toolchain@nightly
-      - uses: taiki-e/install-action@v2
+      - uses: dtolnay/rust-toolchain@4fd1da8b0805d2d2e936788875a7d65dbd677dc2 # nightly
+      - uses: taiki-e/install-action@6a1bd70eaac3c8bdf093356838d7ee09fda951cf # v2
         with:
           tool: cargo-fuzz
       # `fuzz/` depends on `rustysnes-frontend` (the patch/preset/config/symbols boundaries live
@@ -162,7 +168,7 @@ jobs:
       #   cargo +nightly fuzz run <target> <artifact>
       - name: Upload crashing inputs
         if: failure()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a # v7
         with:
           name: fuzz-artifacts
           path: |
diff --git a/.github/workflows/web.yml b/.github/workflows/web.yml
index fa3d1fed..b465ed32 100644
--- a/.github/workflows/web.yml
+++ b/.github/workflows/web.yml
@@ -65,7 +65,9 @@ jobs:
     name: build demo + docs
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v7
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+        with:
+          persist-credentials: false
       # GOTCHA: keep crates/rustysnes-frontend/web/Trunk.toml's wasm-bindgen pin == Cargo.lock
       # library version. `linux-frontend-deps: "true"` because the rustdoc build below compiles
       # the whole workspace (incl. rustysnes-frontend) for the host, which needs the native
@@ -81,7 +83,7 @@ jobs:
       # + its whole dependency tree from source on every single run — minutes of pure setup cost
       # for a tool whose own source never changes here).
       - name: Install trunk
-        uses: taiki-e/install-action@v2
+        uses: taiki-e/install-action@6a1bd70eaac3c8bdf093356838d7ee09fda951cf # v2
         with:
           tool: trunk
 
@@ -112,7 +114,7 @@ jobs:
         run: cargo doc --workspace --exclude rustysnes-android --no-deps
 
       - name: Set up Python for MkDocs
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
         with:
           python-version: "3.12"
 
@@ -148,11 +150,11 @@ jobs:
 
       - name: Configure Pages
         if: github.event_name != 'pull_request'
-        uses: actions/configure-pages@v5
+        uses: actions/configure-pages@983d7736d9b0ae728b81ab479565c72886d7745b # v5
 
       - name: Upload Pages artifact (demo + docs)
         if: github.event_name != 'pull_request'
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@56afc609e74202658d3ffba0e8f6dda462b719fa # v3
         with:
           path: _site
 
@@ -168,4 +170,4 @@ jobs:
     steps:
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v4
+        uses: actions/deploy-pages@d6db90164ac5ed86f2b6aed7e0febac5b3c0c03e # v4
diff --git a/CHANGELOG.md b/CHANGELOG.md
index aa2eab49..d6c3b52f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,47 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Security
+
+- **CI supply-chain hardening — every workflow credential, action pin, and the release gate.**
+  Three items, the first two carried over from the sibling project's `v2.2.2` audit and the third
+  raised in review of the fuzzing PR.
+
+  **`persist-credentials: false` on 15 of 17 checkouts.** `actions/checkout` writes the workflow
+  `GITHUB_TOKEN` into `.git/config`, where anything the job then executes from the tree — build
+  scripts, proc macros, test binaries, `scripts/*.sh`, the MkDocs build — can read it. On a pull
+  request that tree is by definition unreviewed code, and nearly every job here compiles or runs
+  it. Highest exposure was `web.yml`'s `build`, which holds `pages: write` + `id-token: write`
+  while running `trunk`, `cargo doc`, `pip install`, and `mkdocs build`.
+
+  Audited per site rather than applied blanket, and that mattered: **`release-auto.yml`'s `prepare`
+  job genuinely needs the credential** — it creates an annotated tag and `git push origin "$TAG"`,
+  which authenticates through exactly that token. The sibling's audit concluded no job needed it;
+  that conclusion does not transfer, and a blanket sweep would have broken every future release.
+  It is now the only checkout in the repository that keeps the token, with the reason recorded
+  inline, and its exposure is bounded by its trigger (`workflow_run` on a completed CI run of
+  `main`, never a pull request).
+
+  **The release-tag existence check now fails closed.** It was
+  `git ls-remote --exit-code --tags origin "refs/tags/${tag}"`, which collapses three outcomes into
+  two — tag present, tag absent, and *lookup failed* — reading any non-zero exit as "absent". A
+  transient network blip, auth hiccup, or rate limit therefore sent an already-released version
+  down the `should_release=true` path, re-tagging a release the ceremony treats as immutable. Now a
+  `gh api git/matching-refs/tags/<tag>` call, chosen over `git/ref/tags/<tag>` because it answers
+  "absent" with HTTP 200 and an empty array, so a genuine miss can never be confused with an error.
+  That endpoint matches by **prefix**, so the exact ref is compared in `jq` — verified necessary,
+  not theoretical: `v1.2` prefix-matches **7** real tags while exact-matching none, and a naive
+  `length > 0` would have reported it as already released. Every failure path aborts the job.
+
+  **All 34 third-party action references pinned to immutable commit SHAs**, across all 8 workflows
+  plus the composite `rust-setup` action. An upstream tag move could previously change what CI
+  executes without any repository review. Each pin carries its original tag as a trailing comment
+  so the intent stays readable. Also aligned one `actions/upload-artifact@v4` (introduced with the
+  fuzz job) to the `@v7` the rest of the repo already used.
+
+  Verified: `actionlint` reports the same three findings before and after (a self-hosted runner
+  label and two pre-existing shellcheck notes) — no new lint surface; all nine files parse.
+
 ### Added
 
 - **Fuzzing infrastructure (`fuzz/`) — fourteen `cargo-fuzz` targets, one per untrusted-input