diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 210bbdb8..954d5e16 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -4,7 +4,6 @@ on:
   push:
     branches: [main]
   pull_request:
-    branches: [main]
 
 permissions:
   contents: read
@@ -19,11 +18,18 @@ env:
 jobs:
   build-and-test:
     runs-on: ubuntu-24.04
+    timeout-minutes: 30
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
         with:
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
           persist-credentials: false
+      - name: Verify exact checkout
+        env:
+          INKSPAN_EXPECTED_HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+        run: |
+          actual_head="$(git rev-parse HEAD)"
+          test "$actual_head" = "$INKSPAN_EXPECTED_HEAD_SHA"
       # pnpm version comes from the package.json "packageManager" field
       # (pnpm 10+), which is required to read `overrides` from
       # pnpm-workspace.yaml consistently with the committed lockfile.
@@ -47,7 +53,7 @@ jobs:
   browser-release-evidence:
     name: Cross-engine Clipboard / Playwright 1.62.0
     runs-on: ubuntu-24.04
-    timeout-minutes: 30
+    timeout-minutes: 60
     env:
       PLAYWRIGHT_BROWSERS_PATH: /tmp/inkspan-playwright-browsers
     steps:
@@ -55,6 +61,12 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
           persist-credentials: false
+      - name: Verify exact checkout
+        env:
+          INKSPAN_EXPECTED_HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+        run: |
+          actual_head="$(git rev-parse HEAD)"
+          test "$actual_head" = "$INKSPAN_EXPECTED_HEAD_SHA"
       - uses: pnpm/action-setup@0977fd99725f1db4007ccb2928dbb4e90d06cc86 # v6.0.10
       - uses: actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0
         with:
@@ -74,6 +86,7 @@ jobs:
   office:
     name: Office / Python ${{ matrix.python-version }}
     runs-on: ubuntu-24.04
+    timeout-minutes: 30
     strategy:
       fail-fast: false
       matrix:
@@ -88,6 +101,12 @@ jobs:
         with:
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
           persist-credentials: false
+      - name: Verify exact checkout
+        env:
+          INKSPAN_EXPECTED_HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}
+        run: |
+          actual_head="$(git rev-parse HEAD)"
+          test "$actual_head" = "$INKSPAN_EXPECTED_HEAD_SHA"
       - uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0
         with:
           python-version: ${{ matrix.python-version }}
diff --git a/src/workflowExactHead.test.ts b/src/workflowExactHead.test.ts
index 8da26fe4..d1f05310 100644
--- a/src/workflowExactHead.test.ts
+++ b/src/workflowExactHead.test.ts
@@ -19,18 +19,102 @@ const VULNERABLE_PNPM_ACTION_SETUP_PIN =
   'pnpm/action-setup@0e279bb959325dab635dd2c09392533439d90093 # v6.0.8';
 const SETUP_NODE_PIN =
   'actions/setup-node@820762786026740c76f36085b0efc47a31fe5020 # v7.0.0';
+const SETUP_PYTHON_PIN =
+  'actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5.6.0';
+const EXPECTED_HEAD_REF =
+  'ref: ${{ github.event.pull_request.head.sha || github.sha }}';
+const VERIFY_EXACT_CHECKOUT_STEP = [
+  '- name: Verify exact checkout',
+  '        env:',
+  '          INKSPAN_EXPECTED_HEAD_SHA: ${{ github.event.pull_request.head.sha || github.sha }}',
+  '        run: |',
+  '          actual_head="$(git rev-parse HEAD)"',
+  '          test "$actual_head" = "$INKSPAN_EXPECTED_HEAD_SHA"',
+].join('\n');
+
+/** Return one top-level workflow job without borrowing assertions from siblings. */
+function workflowJob(source: string, name: string, nextName?: string): string {
+  const startMarker = `  ${name}:\n`;
+  const start = source.indexOf(startMarker);
+  expect(start).toBeGreaterThan(-1);
+  if (nextName === undefined) {
+    return source.slice(start);
+  }
+  const end = source.indexOf(`\n  ${nextName}:\n`, start + startMarker.length);
+  expect(end).toBeGreaterThan(start);
+  return source.slice(start, end);
+}
+
+/** Require checkout -> exact-SHA verification -> first consumer in one job. */
+function expectExactCheckoutBeforeConsumer(job: string, consumer: string): void {
+  const checkout = job.indexOf(`- uses: ${CHECKOUT_PIN}`);
+  const verification = job.indexOf(VERIFY_EXACT_CHECKOUT_STEP);
+  const consumerIndex = job.indexOf(consumer);
+
+  expect(checkout).toBeGreaterThan(-1);
+  expect(verification).toBeGreaterThan(checkout);
+  expect(consumerIndex).toBeGreaterThan(verification);
+  expect(job.match(new RegExp(CHECKOUT_PIN, 'g'))).toHaveLength(1);
+  expect(job.match(new RegExp(EXPECTED_HEAD_REF.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'), 'g'))).toHaveLength(1);
+  expect(job.match(/persist-credentials: false/g)).toHaveLength(1);
+  expect(job.split(VERIFY_EXACT_CHECKOUT_STEP)).toHaveLength(2);
+
+  const checkoutStep = job.slice(checkout, verification);
+  expect(checkoutStep).not.toContain('\n      - ');
+}
+
+const buildJob = workflowJob(workflow, 'build-and-test', 'browser-release-evidence');
+const browserJob = workflowJob(workflow, 'browser-release-evidence', 'office');
+const officeJob = workflowJob(workflow, 'office');
 
 describe('exact-head CI workflow contract', () => {
-  it('uses a fixed runner and checks out the immutable current PR head', () => {
+  it('uses a fixed runner and checks out the immutable current PR head in every job', () => {
     expect(workflow).not.toContain('ubuntu-latest');
-    expect(workflow.match(/runs-on: ubuntu-24\.04/g)).toHaveLength(3);
-    expect(workflow.match(new RegExp(CHECKOUT_PIN, 'g'))).toHaveLength(3);
-    expect(
-      workflow.match(
-        /ref: \$\{\{ github\.event\.pull_request\.head\.sha \|\| github\.sha \}\}/g,
-      ),
-    ).toHaveLength(3);
-    expect(workflow.match(/persist-credentials: false/g)).toHaveLength(3);
+    for (const job of [buildJob, browserJob, officeJob]) {
+      expect(job.match(/runs-on: ubuntu-24\.04/g)).toHaveLength(1);
+      expect(job).toContain(`- uses: ${CHECKOUT_PIN}`);
+      expect(job).toContain(EXPECTED_HEAD_REF);
+      expect(job).toContain('persist-credentials: false');
+    }
+  });
+
+  it('runs exact-head CI for pull requests regardless of stacked base branch', () => {
+    const triggerStart = workflow.indexOf('on:\n');
+    const triggerEnd = workflow.indexOf('\npermissions:', triggerStart);
+    expect(triggerStart).toBeGreaterThan(-1);
+    expect(triggerEnd).toBeGreaterThan(triggerStart);
+    const triggerBlock = workflow.slice(triggerStart, triggerEnd);
+
+    expect(triggerBlock).toContain('  push:\n    branches: [main]');
+    const pullRequestLines = triggerBlock
+      .split('\n')
+      .filter((line) => line.startsWith('  pull_request:'));
+    expect(pullRequestLines).toEqual(['  pull_request:']);
+    expect(triggerBlock).not.toMatch(/  pull_request:\n(?:    .*\n)*?    branches:/u);
+  });
+
+  it('binds timeout policy to the intended job instead of global counts', () => {
+    expect(buildJob.match(/timeout-minutes:/g)).toHaveLength(1);
+    expect(buildJob).toContain('timeout-minutes: 30');
+    expect(browserJob.match(/timeout-minutes:/g)).toHaveLength(1);
+    expect(browserJob).toContain('timeout-minutes: 60');
+    expect(officeJob.match(/timeout-minutes:/g)).toHaveLength(1);
+    expect(officeJob).toContain('timeout-minutes: 30');
+  });
+
+  it('verifies each runtime checkout immediately before repository-consuming setup', () => {
+    expectExactCheckoutBeforeConsumer(
+      buildJob,
+      `- uses: ${PNPM_ACTION_SETUP_PIN}`,
+    );
+    expectExactCheckoutBeforeConsumer(
+      browserJob,
+      `- uses: ${PNPM_ACTION_SETUP_PIN}`,
+    );
+    expectExactCheckoutBeforeConsumer(
+      officeJob,
+      `- uses: ${SETUP_PYTHON_PIN}`,
+    );
   });
 
   it('keeps the workflow read-only and hash-pins every third-party action', () => {
@@ -51,12 +135,16 @@ describe('exact-head CI workflow contract', () => {
   });
 
   it('does not bootstrap pnpm through the vulnerable action release', () => {
-    expect(workflow.match(new RegExp(PNPM_ACTION_SETUP_PIN, 'g'))).toHaveLength(2);
+    expect(buildJob).toContain(PNPM_ACTION_SETUP_PIN);
+    expect(browserJob).toContain(PNPM_ACTION_SETUP_PIN);
+    expect(officeJob).not.toContain(PNPM_ACTION_SETUP_PIN);
     expect(workflow).not.toContain(VULNERABLE_PNPM_ACTION_SETUP_PIN);
   });
 
   it('uses the current native-Node-24 setup-node release in every JavaScript job', () => {
-    expect(workflow.match(new RegExp(SETUP_NODE_PIN, 'g'))).toHaveLength(2);
+    expect(buildJob).toContain(SETUP_NODE_PIN);
+    expect(browserJob).toContain(SETUP_NODE_PIN);
+    expect(officeJob).not.toContain(SETUP_NODE_PIN);
     expect(workflow).not.toContain(
       'actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0',
     );