diff --git a/.github/workflows/pr-review-fix-scheduler.yml b/.github/workflows/pr-review-fix-scheduler.yml
index cc7875bc8..df68848ca 100644
--- a/.github/workflows/pr-review-fix-scheduler.yml
+++ b/.github/workflows/pr-review-fix-scheduler.yml
@@ -26,7 +26,7 @@ on:
       retry_hours:
         description: Minimum hours before redispatching autofix for the same head
         required: false
-        default: "24"
+        default: "1"
         type: string
       autofix_workflow:
         description: Autofix workflow file to dispatch
@@ -44,14 +44,16 @@ on:
         default: ""
         type: string
       canonical_ref:
-        description: Ref of ContextualWisdomLab/.github to use for scheduler code
+        description: Deprecated compatibility input; accepted and ignored because privileged source is bound to the called workflow SHA
         required: false
-        default: "main"
+        default: ""
         type: string
   repository_dispatch:
     types: [pr-review-fix-scheduler]
   schedule:
-    - cron: "23 */2 * * *"
+    # Run away from minute zero, where scheduled GitHub Actions are more likely
+    # to be delayed, while preserving a bounded one-dispatch-per-run repair loop.
+    - cron: "23 * * * *"
 
 concurrency:
   group: central-pr-review-fix-scheduler-${{ github.event.client_payload.target_repository || inputs.target_repository || vars.PR_REVIEW_FIX_TARGET_REPOSITORY || github.repository }}
@@ -80,16 +82,19 @@ jobs:
       DRY_RUN: ${{ github.event.client_payload.dry_run == true || github.event.client_payload.dry_run == 'true' || inputs.dry_run == true }}
       MAX_PRS: ${{ github.event.client_payload.max_prs || inputs.max_prs || '50' }}
       MAX_DISPATCHES: ${{ github.event.client_payload.max_dispatches || inputs.max_dispatches || '1' }}
-      RETRY_HOURS: ${{ github.event.client_payload.retry_hours || inputs.retry_hours || '24' }}
+      RETRY_HOURS: ${{ github.event.client_payload.retry_hours || inputs.retry_hours || '1' }}
       AUTOFIX_WORKFLOW: pr-review-autofix.yml
       AUTOFIX_REPOSITORY: ContextualWisdomLab/.github
-      CANONICAL_REF: main
     steps:
-      - name: Checkout canonical scheduler
+      - name: Checkout immutable called-workflow source
         uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
-          repository: ContextualWisdomLab/.github
-          ref: ${{ env.CANONICAL_REF }}
+          # In a reusable workflow the ordinary github context belongs to the
+          # caller. The job workflow context identifies the called workflow's
+          # repository and immutable resolved SHA, preventing a caller input or
+          # mutable branch from selecting the privileged scheduler code.
+          repository: ${{ job.workflow_repository }}
+          ref: ${{ job.workflow_sha }}
           fetch-depth: 1
           persist-credentials: false
 
diff --git a/tests/test_pr_review_fix_hourly_contract.py b/tests/test_pr_review_fix_hourly_contract.py
new file mode 100644
index 000000000..f55408fc8
--- /dev/null
+++ b/tests/test_pr_review_fix_hourly_contract.py
@@ -0,0 +1,45 @@
+"""Static contract for the central hourly PR review-fix scheduler."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+
+_WORKFLOW = Path(".github/workflows/pr-review-fix-scheduler.yml")
+
+
+def _workflow_text() -> str:
+    """Return the canonical scheduler workflow text."""
+    return _WORKFLOW.read_text(encoding="utf-8")
+
+
+def test_review_fix_scheduler_runs_once_each_hour() -> None:
+    """The bounded repair dispatcher uses the requested hourly heartbeat."""
+    text = _workflow_text()
+
+    assert 'cron: "23 * * * *"' in text
+    assert 'cron: "23 */2 * * *"' not in text
+
+
+def test_review_fix_scheduler_retries_same_head_after_one_hour() -> None:
+    """A blocked head can be retried on the next hourly cycle, not a day later."""
+    text = _workflow_text()
+
+    retry_block = text.split("retry_hours:", maxsplit=1)[1].split(
+        "autofix_workflow:", maxsplit=1
+    )[0]
+    assert 'default: "1"' in retry_block
+    assert "inputs.retry_hours || '1'" in text
+    assert "inputs.retry_hours || '24'" not in text
+
+
+def test_review_fix_scheduler_remains_bounded_and_single_flight() -> None:
+    """Higher cadence never expands mutation volume or parallel execution."""
+    text = _workflow_text()
+
+    dispatch_block = text.split("max_dispatches:", maxsplit=1)[1].split(
+        "target_repository:", maxsplit=1
+    )[0]
+    assert 'default: "1"' in dispatch_block
+    assert "cancel-in-progress: true" in text
+    assert "MAX_DISPATCHES" in text
diff --git a/tests/test_pr_review_fix_scheduler_source_pin.py b/tests/test_pr_review_fix_scheduler_source_pin.py
new file mode 100644
index 000000000..3e1db72ed
--- /dev/null
+++ b/tests/test_pr_review_fix_scheduler_source_pin.py
@@ -0,0 +1,54 @@
+"""Supply-chain contract for the reusable PR-review autofix scheduler."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+
+_REPO_ROOT = Path(__file__).resolve().parents[1]
+_WORKFLOW = _REPO_ROOT / ".github" / "workflows" / "pr-review-fix-scheduler.yml"
+
+
+def _workflow_text() -> str:
+    """Read the reusable scheduler workflow as UTF-8 text."""
+    return _WORKFLOW.read_text(encoding="utf-8")
+
+
+def test_reusable_scheduler_checks_out_the_called_workflow_sha() -> None:
+    """Privileged scheduler code comes from the immutable called-workflow revision."""
+    workflow = _workflow_text()
+    assert "repository: ${{ job.workflow_repository }}" in workflow
+    assert "ref: ${{ job.workflow_sha }}" in workflow
+    assert "persist-credentials: false" in workflow
+
+
+def test_reusable_scheduler_source_is_not_caller_input_controlled() -> None:
+    """No caller-supplied ref or ordinary caller GitHub SHA selects trusted code."""
+    workflow = _workflow_text()
+    assert "inputs.canonical_ref" not in workflow
+    assert "github.event.client_payload.canonical_ref" not in workflow
+    assert "ref: ${{ env.CANONICAL_REF }}" not in workflow
+    assert "ref: ${{ github.sha }}" not in workflow
+
+
+def test_deprecated_canonical_ref_input_is_accepted_but_never_consumed() -> None:
+    """Existing callers can upgrade pins without controlling privileged source."""
+    workflow = _workflow_text()
+    declaration = workflow.split("canonical_ref:", 1)[1].split(
+        "repository_dispatch:", 1
+    )[0]
+
+    assert "Deprecated compatibility input" in declaration
+    assert "ignored" in declaration
+    assert 'default: ""' in declaration
+    assert workflow.count("canonical_ref") == 1
+
+
+def test_reusable_scheduler_retains_least_privilege_and_bounded_dispatch() -> None:
+    """Source pinning does not broaden token scope or queue fan-out."""
+    workflow = _workflow_text()
+    assert "contents: write" not in workflow
+    assert "pull-requests: write" not in workflow
+    assert "MAX_DISPATCHES:" in workflow
+    assert "RETRY_HOURS:" in workflow
+    assert "cancel-in-progress: true" in workflow