diff --git a/.github/workflows/required-quality-gate.yml b/.github/workflows/required-quality-gate.yml
index 6d903e7..3f0a9d0 100644
--- a/.github/workflows/required-quality-gate.yml
+++ b/.github/workflows/required-quality-gate.yml
@@ -13,11 +13,63 @@ concurrency:
 
 jobs:
   quality-gate:
-    name: quality-gate
-    uses: HMG-AI/.github/.github/workflows/reusable-commitlint.yml@978d6d08d6bfc1e8a3662c1f9b0daab8bfa0e557
-    with:
-      base_sha: ${{ github.event.pull_request.base.sha || github.event.merge_group.base_sha }}
-      head_sha: ${{ github.event.pull_request.head.sha || github.event.merge_group.head_sha }}
+    name: quality-gate / commitlint
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    container:
+      image: node:24.11.1-bookworm@sha256:9a2ed90cd91b1f3412affe080b62e69b057ba8661d9844e143a6bbd76a23260f
+      options: --security-opt=no-new-privileges
+    steps:
+      - name: Validate commit SHA inputs
+        shell: bash
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha || github.event.merge_group.base_sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha || github.event.merge_group.head_sha }}
+        run: |
+          set -Eeuo pipefail
+          readonly sha_pattern='^[0-9a-f]{40}$'
+
+          for sha_name in BASE_SHA HEAD_SHA; do
+            sha_value="${!sha_name}"
+            if [[ ! "${sha_value}" =~ ${sha_pattern} ]]; then
+              echo "::error::${sha_name} must be a full 40-character lowercase hexadecimal commit SHA"
+              exit 2
+            fi
+          done
+
+      - name: Check out caller repository history
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha || github.event.merge_group.head_sha }}
+          path: caller
+          persist-credentials: false
+
+      - name: Check out immutable organization commit policy
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
+        with:
+          repository: HMG-AI/.github
+          ref: ${{ github.workflow_sha }}
+          path: governance-source
+          sparse-checkout: governance/commitlint
+          persist-credentials: false
+
+      - name: Install locked commitlint dependencies
+        shell: bash
+        working-directory: governance-source/governance/commitlint
+        run: npm ci --ignore-scripts --no-audit --no-fund
+
+      - name: Lint every commit in base..head
+        shell: bash
+        env:
+          BASE_SHA: ${{ github.event.pull_request.base.sha || github.event.merge_group.base_sha }}
+          HEAD_SHA: ${{ github.event.pull_request.head.sha || github.event.merge_group.head_sha }}
+        run: |
+          set -Eeuo pipefail
+          bash "${GITHUB_WORKSPACE}/governance-source/governance/commitlint/lint-range.sh" \
+            "${GITHUB_WORKSPACE}/caller" \
+            "${BASE_SHA}" \
+            "${HEAD_SHA}"
 
   workflow-security-policy:
     name: workflow-security-policy
diff --git a/governance/commitlint/commitlint.config.mjs b/governance/commitlint/commitlint.config.mjs
index 78470f5..e22e22a 100644
--- a/governance/commitlint/commitlint.config.mjs
+++ b/governance/commitlint/commitlint.config.mjs
@@ -7,6 +7,26 @@ const noHan = (field) => (parsed) => [
   `${field} must not contain Unicode Han script characters`,
 ];
 
+const canonicalLongProvenanceTrailers = [
+  /^HMG-Provenance-Key-ID: ed25519-spki-sha256-[0-9a-f]{64}$/,
+  /^HMG-Provenance-Signature-Ed25519: [A-Za-z0-9+/]{86}==$/,
+];
+
+const boundedFooterLines = (parsed, _when, limit = 100) => {
+  const invalidLines = (parsed.footer ?? '')
+    .split('\n')
+    .filter(
+      (line) =>
+        line.length > limit &&
+        !canonicalLongProvenanceTrailers.some((pattern) => pattern.test(line)),
+    );
+
+  return [
+    invalidLines.length === 0,
+    `footer lines must not exceed ${limit} characters unless they are canonical HMG provenance trailers`,
+  ];
+};
+
 export default {
   ...conventional,
   plugins: [
@@ -15,11 +35,17 @@ export default {
         'subject-no-han': noHan('subject'),
         'body-no-han': noHan('body'),
         'footer-no-han': noHan('footer'),
+        'footer-bounded-lines': boundedFooterLines,
       },
     },
   ],
   rules: {
     ...conventional.rules,
+    // The two canonical cryptographic trailers exceed the conventional
+    // 100-character limit. Disable the broad built-in rule and replace it
+    // with a strict shape-aware exception.
+    'footer-max-line-length': [0],
+    'footer-bounded-lines': [2, 'always', 100],
     'subject-no-han': [2, 'always'],
     'body-no-han': [2, 'always'],
     'footer-no-han': [2, 'always'],
diff --git a/governance/commitlint/test/commitlint.test.mjs b/governance/commitlint/test/commitlint.test.mjs
index 09e894c..46ebe0a 100644
--- a/governance/commitlint/test/commitlint.test.mjs
+++ b/governance/commitlint/test/commitlint.test.mjs
@@ -39,6 +39,32 @@ test('accepts a conventional English commit message', () => {
   assert.equal(result.status, 0, result.stdout || result.stderr);
 });
 
+test('accepts canonical cryptographic provenance trailers', () => {
+  const message = [
+    'chore(public): promote HMG v1.7.7',
+    '',
+    `HMG-Provenance-Key-ID: ed25519-spki-sha256-${'a'.repeat(64)}`,
+    `HMG-Provenance-Signature-Ed25519: ${'A'.repeat(86)}==`,
+    '',
+  ].join('\n');
+  const result = lint(message);
+  assert.equal(result.status, 0, result.stdout || result.stderr);
+});
+
+test('rejects an ordinary footer line longer than 100 characters', () => {
+  assertLintFailure(
+    `chore: reject an oversized footer\n\nAudit-Value: ${'a'.repeat(130)}\n`,
+    'footer-bounded-lines',
+  );
+});
+
+test('rejects a long provenance-shaped trailer with a malformed value', () => {
+  assertLintFailure(
+    `chore(public): reject malformed provenance\n\nHMG-Provenance-Signature-Ed25519: ${'A'.repeat(85)}===\n`,
+    'footer-bounded-lines',
+  );
+});
+
 test('rejects Unicode Han script in subject, body, and footer', () => {
   assertLintFailure('fix: 修复 tenant lookup\n', 'subject-no-han');
   assertLintFailure(