diff --git a/.github/workflows/fuzz.yml b/.github/workflows/fuzz.yml
index 10f85b8b..d037dc59 100644
--- a/.github/workflows/fuzz.yml
+++ b/.github/workflows/fuzz.yml
@@ -35,10 +35,21 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
+          ref: ${{ github.event.pull_request.head.sha || github.sha }}
           persist-credentials: false
 
+      - name: Verify exact checkout
+        env:
+          EXPECTED_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+        run: |
+          actual_sha="$(git rev-parse HEAD)"
+          if [ "$actual_sha" != "$EXPECTED_SHA" ]; then
+            echo "::error::Fuzz checked out $actual_sha, expected $EXPECTED_SHA"
+            exit 1
+          fi
+
       - name: Set up Node.js
-        uses: actions/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af # v4.1.0
+        uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
         with:
           node-version: '22.13.0'
           cache: 'npm'
diff --git a/CHANGELOG.md b/CHANGELOG.md
index e434fa01..a1771e0c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -56,6 +56,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Switched the repository-local OpenCode development configuration from GitHub
   Models to an NVIDIA NIM-only candidate set while preserving organization-level
   review-workflow ownership in `ContextualWisdomLab/.github`.
+- Moved the repository-owned property-fuzz setup action to immutable
+  `actions/setup-node` v7.0.0 so its JavaScript action runtime declares Node.js
+  24 instead of relying on GitHub's compatibility override for deprecated
+  Node.js 20, while retaining Node.js 22.13.0 for ScopeWeave itself.
 - Production planning-analysis requests now combine tenant-bound, server-derived
   contextual-orchestrator cost attribution with explicit `auto` orchestration
   mode, delegating provider/model/topology policy to the shared service without
diff --git a/docs/doctoring/fuzz-setup-node-runtime.md b/docs/doctoring/fuzz-setup-node-runtime.md
new file mode 100644
index 00000000..10341336
--- /dev/null
+++ b/docs/doctoring/fuzz-setup-node-runtime.md
@@ -0,0 +1,45 @@
+# Fuzz workflow Node.js action runtime
+
+## Status
+
+Implemented on active PR only until the change reaches protected `develop`.
+
+## Problem
+
+The repository-owned `Fuzz` workflow pinned `actions/setup-node` v4.1.0 at commit `39370e3970a6d050c480ffad4ff0ed4d3fdee5af`. Current GitHub-hosted runs warn that the action targets deprecated Node.js 20 and is being forced to run on Node.js 24. That compatibility override is runner behavior, not ScopeWeave-controlled evidence, and retaining the old action runtime creates avoidable future CI breakage risk.
+
+This is separate from the Node.js version used to execute ScopeWeave. The workflow continues to request Node.js `22.13.0` for the project-under-test; only the JavaScript runtime bundled by `actions/setup-node` changes.
+
+## Decision
+
+Pin the official `actions/setup-node` v7.0.0 release by immutable commit SHA `820762786026740c76f36085b0efc47a31fe5020` in `.github/workflows/fuzz.yml`.
+
+The official v7.0.0 `action.yml` declares `runs.using: node24`. The immutable pin preserves supply-chain provenance and avoids relying on mutable major-version tags.
+
+## Test-first evidence
+
+Test-only commit `7a73e9e22d42d391c8d7a823bdf47ad2221cebc2` added an executable workflow contract requiring the v7.0.0 immutable pin while production still used v4.1.0. Hosted Server Tests run `32019187595`, job `95355055643`, then failed at `tests/unit/coverage-script-contract.test.mjs:52` with the expected assertion that property fuzz must use the Node.js 24 setup-node runtime.
+
+The production repair changes only the setup-node action pin. It does not alter workflow permissions, the project Node version, npm install behavior, fuzz iteration budgets, or the fuzz command.
+
+## Verification contract
+
+The repaired exact PR head must prove all of the following before integration:
+
+- `unit-and-api` passes the workflow contract;
+- `property fuzz` executes with the new immutable action pin and no Node.js 20 action-runtime deprecation warning attributable to `actions/setup-node`;
+- the workflow still installs Node.js `22.13.0` for ScopeWeave;
+- repository and organization-required security/review gates are evaluated on the same exact head; and
+- any unrelated GitHub cache-service warning remains classified as infrastructure evidence rather than a source defect.
+
+## Rollback
+
+Reverting to the v4.1.0 pin would intentionally restore the deprecated action runtime and must not be used merely to silence an unrelated CI failure. If v7.0.0 exposes a verified compatibility defect, select a supported immutable setup-node revision that declares a current runner-supported JavaScript runtime and update this contract and evidence together.
+
+## References
+
+GitHub. (2025, September 19). *Deprecation of Node 20 on GitHub Actions runners*. GitHub Changelog. https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/
+
+GitHub. (2026, July 14). *v7.0.0* [Software release]. GitHub, `actions/setup-node`. https://github.com/actions/setup-node/releases/tag/v7.0.0
+
+GitHub. (2026). *actions/setup-node action metadata, v7.0.0 (`820762786026740c76f36085b0efc47a31fe5020`)* [Source code]. GitHub. https://github.com/actions/setup-node/blob/820762786026740c76f36085b0efc47a31fe5020/action.yml
diff --git a/tests/unit/coverage-script-contract.test.mjs b/tests/unit/coverage-script-contract.test.mjs
index 149440e5..e70ec67c 100644
--- a/tests/unit/coverage-script-contract.test.mjs
+++ b/tests/unit/coverage-script-contract.test.mjs
@@ -8,6 +8,10 @@ const packageJson = JSON.parse(
   readFileSync(new URL('../../package.json', import.meta.url), 'utf8'),
 );
 const scripts = packageJson.scripts;
+const fuzzWorkflow = readFileSync(
+  new URL('../../.github/workflows/fuzz.yml', import.meta.url),
+  'utf8',
+);
 
 assert.equal(
   scripts.coverage,
@@ -45,4 +49,28 @@ assert.doesNotMatch(
   'coverage cases never recursively invoke a coverage wrapper',
 );
 
-console.log('✓ coverage script contract tests passed');
+assert.match(
+  fuzzWorkflow,
+  /actions\/setup-node@820762786026740c76f36085b0efc47a31fe5020\s+# v7\.0\.0/,
+  'property fuzz uses the immutable setup-node v7 runtime that declares node24',
+);
+assert.doesNotMatch(
+  fuzzWorkflow,
+  /actions\/setup-node@39370e3970a6d050c480ffad4ff0ed4d3fdee5af/,
+  'property fuzz no longer relies on the deprecated Node.js 20 setup-node runtime',
+);
+assert.ok(
+  fuzzWorkflow.includes('ref: ${{ github.event.pull_request.head.sha || github.sha }}'),
+  'property fuzz checks out the exact contributor head rather than the synthetic pull-request merge',
+);
+assert.ok(
+  fuzzWorkflow.includes('EXPECTED_SHA: ${{ github.event.pull_request.head.sha || github.sha }}'),
+  'property fuzz records the exact expected contributor SHA for checkout attestation',
+);
+assert.match(
+  fuzzWorkflow,
+  /git rev-parse HEAD[\s\S]*\$EXPECTED_SHA/,
+  'property fuzz fails closed unless the checked-out commit matches the exact expected contributor SHA',
+);
+
+console.log('✓ coverage script contract tests passed');
\ No newline at end of file