---
phase: 04
slug: harden-clean-up-optional
plan: 08
type: auto
wave: 5.5
depends_on:
  - 01
  - 02
  - 03
  - 04
  - 05
  - 06
files_modified:
  - tests/uat/fixtures/synthetic-display-source.webm
  - src/test-hooks/offscreen-hooks.ts
  - globals.d.ts
  - manifest.json
  - vite.config.ts
  - vite.test.config.ts
  - tests/uat/extension-page-harness.ts
  - tests/uat/lib/harness-page-driver.ts
  - tests/uat/harness.test.ts
  - tests/uat/spike-a33-sw-persistence.ts
  - tests/background/no-test-hooks-in-prod-bundle.test.ts
autonomous: true
requirements: []
tags:
  - uat-harness
  - a33
  - methodology-reframe
  - video-file-source
  - htmlvideoelement-capturestream
  - canvas-throttling-fix
  - chrome-bug-653548
  - charter-d-p4-01
  - roadmap-sc-1-closes
  - post-debug-session-2
  - planner-iter-2-revision
user_setup: []
revision_history:
  - iter: 1
    plan_commit: 504d9dc
    checker_commit: 051813e
    verdict: ITERATE-NEEDED
    blockers_addressed:
      - "BLOCKER 1: Vite ?url -> dist-test/assets/<hash>.webm web_accessible_resources strategy now pre-decided (per checker Option B + user objective Option A) — explicit WAR entry for assets/*.webm in manifest.json + chrome.runtime.getURL() not needed because Vite's ?url import resolves to the chrome-extension://<id>/assets/<hash>.webm form already (verified by Plan 01-10 mokosh-mark.svg precedent for SVG; differs only by extension). The WAR entry covers production (zero *.webm assets — entry is inert) AND test bundle (offscreen reaches the asset via direct ?url import; the WAR entry just authorizes chrome-extension:// scheme access from the offscreen document context). No executor improvisation."
      - "BLOCKER 2: installFakeDisplayMedia() remains SYNCHRONOUS at module load — preserves eager-install contract at lines 533-537. The HTMLVideoElement creation + DOM append + monkey-patch installation happen synchronously. The canplay wait + .play() + first captureStream call are deferred INTO the fakeGetDisplayMedia closure (lazy first-frame pattern). First getDisplayMedia call awaits readyState >= HAVE_FUTURE_DATA; subsequent calls reuse the now-ready video element. Zero race window with recorder.ts:46-48 top-level await chain."
    warnings_addressed:
      - "WARNING 1: headless autoplay fallback documented — if videoEl.play() rejects with NotAllowedError, the closure throws with explicit 'autoplay-blocked' error class so the spike surfaces the precise root cause (not a mysterious 0-frames)."
      - "WARNING 2: patchDisplaySurface compatibility check — added explicit sub-verify gate that tests track.getSettings().displaySurface === 'monitor' on a fresh mintStream() call BEFORE the spike re-run."
      - "WARNING 3: spike probe-value asserts surfaced as explicit grep gates in Task 2 <verify> block (POST-PRIME=0, PRE-KILL≥3, POST-KILL≥3)."
      - "WARNING 4: ROADMAP.md edit pre-specified — exact sed-replace target documented; grep gate enforces post-edit invariant."
      - "WARNING 5: synthetic-display-source filename leak gate added as Tier-2 invariant in tests/background/no-test-hooks-in-prod-bundle.test.ts (dist/ grep for 'synthetic-display-source' returns 0)."
    cosmetics_addressed:
      - "advisory 1: Task 3 mis-reference in commit message corrected (Task 1 + Task 2 only)."
      - "advisory 2: recorder.ts:91 segments invariant gated by grep in Task 1 verify."
      - "advisory 3: dual-fixture-location note added to Task 1 Step 1."
must_haves:
  truths:
    - "installFakeDisplayMedia() at src/test-hooks/offscreen-hooks.ts is SYNCHRONOUS at module load — preserves the eager-install contract at lines 533-537 (the monkey-patch on navigator.mediaDevices.getDisplayMedia is in place BEFORE recorder.ts:46-48 top-level await resolves)"
    - "fakeGetDisplayMedia closure performs the lazy first-frame wait — first invocation awaits videoEl.readyState >= 3 (HAVE_FUTURE_DATA) + .play(); subsequent invocations reuse the cached ready video element; mint a fresh MediaStream each call (matching the existing canvas.captureStream-per-call contract)"
    - "installFakeDisplayMedia() at src/test-hooks/offscreen-hooks.ts mints its MediaStream from an HTMLVideoElement playing a bundled WebM (NOT from canvas.captureStream); the video element loops a >=30s VP9 source so the MediaRecorder sees real frame data across the full 5-min spike window"
    - "tests/uat/fixtures/synthetic-display-source.webm exists as a CC0/internal-owned >=1MB VP9 WebM with duration >=30s; bundled into the test-config build via Vite ?url import (per Plan 01-10 mokosh-mark.svg precedent); chrome-extension:// scheme access from offscreen document is authorized via the explicit web_accessible_resources entry for assets/*.webm in manifest.json"
    - "manifest.json web_accessible_resources block contains an explicit entry for assets/*.webm — pre-decided per planner iter-2 (no executor improvisation; the entry is inert in production where dist/ has zero *.webm assets, and load-bearing in test build where dist-test/assets/<hash>.webm needs chrome-extension:// authorization)"
    - "tests/uat/spike-a33-sw-persistence.ts re-runs end-to-end and produces videoSize > 100_000 (canonical run with worker.close()) — empirically refutes the previous 8505-byte 0-frames methodology failure and confirms ROADMAP SC #1 architectural integrity per debug session-2 verdict; spike probe values shift from (POST-PRIME=0, PRE-KILL=3, POST-KILL=3 but 0 frames) -> (POST-PRIME=0, PRE-KILL>=3, POST-KILL>=3 with NON-ZERO frames; videoSize > 100_000)"
    - "assertA33 / driveA33 / orchestrator wiring land per the original Plan 04-04 Pattern 4 verbatim (cs-injection-world precedent NOT applicable — A33 is host-side CDP-driven, not page-side rrweb-driven)"
    - "stopServiceWorker(browser, extensionId) helper at tests/uat/lib/harness-page-driver.ts is reused verbatim from Plan 04-04 (already committed at 3726eee); no new helper symbol needed"
    - "A33 env-gated by SKIP_LONG_UAT (default RUN for closure + alpha gate; SKIP_LONG_UAT=1 to skip per-commit iteration); 95s baseline preserved when skipped"
    - "UAT harness count flips 33 -> 34 (A33 added); 34/34 GREEN when SKIP_LONG_UAT unset; vitest 183/183 GREEN preserved"
    - "ROADMAP SC #1 (SW state persistence) GREEN — A33 empirical evidence that a 5-min idle + Puppeteer worker.close() + SAVE_ARCHIVE produces video/last_30sec.webm with size > 100 KB; ROADMAP.md row flipped from 'STATUS 2026-05-21: OPEN' to 'STATUS 2026-05-22: CLOSED via Plan 04-08'"
    - "Tier-1 FORBIDDEN_HOOK_STRINGS inventory unchanged at 12 entries (lockstep across tests/uat/harness.test.ts + tests/background/no-test-hooks-in-prod-bundle.test.ts) — Plan 04-08 introduces NO new __MOKOSH_UAT__-gated symbols on production bundle; the bundled WebM ships only in test build per Vite ?url + test-config gating"
    - "Tier-2 production-bundle filename leak gate added: 'synthetic-display-source' string returns 0 hits across dist/ — codified in tests/background/no-test-hooks-in-prod-bundle.test.ts as a new sub-invariant (canary for future regressions that might accidentally inline test-hooks into the production chunk)"
    - "Pre-checkpoint bundle gates 6/6 PASS unchanged from Plan 04-03 baseline (new Function=0 + eval=0 + Buffer.=1 pre-existing JSZip + window./document.=0 in SW + Tier-1 inventory=12 + en/ru parity preserved) — production source delta is zero (only src/test-hooks/* changes; tree-shaken in production per __MOKOSH_UAT__ gate)"
    - "Architecture integrity preserved per debug session-2 verdict — src/offscreen/recorder.ts:91 `let segments: Blob[] = []` RAM-only architecture is canonically correct (verified by grep gate); no IndexedDB persistence work, no chrome.storage migration, no offscreen-document lifecycle changes"
    - "patchDisplaySurface monkey-patch survives HTMLVideoElement.captureStream — verified by an explicit sub-test in Task 1 verify block (a synthetic mintStream() call + track.getSettings().displaySurface === 'monitor' assertion BEFORE the spike re-run)"
  artifacts:
    - path: "tests/uat/fixtures/synthetic-display-source.webm"
      provides: "Bundled CC0/internal VP9 WebM source for HTMLVideoElement.captureStream — replaces canvas-captureStream invisible-source throttling. Size 1-3 MB; duration >=30s; loopable (autoplay+loop+muted). License: internal capture by this project's MediaRecorder pipeline (CC0-equivalent project-owned). Note: tests/fixtures/last_30sec.webm (the original Plan 01-07 regression fixture) remains in place; this is a SECOND copy at tests/uat/fixtures/ for the Vite ?url import to resolve cleanly without crossing the test-vs-fixtures dir boundary."
      min_size_bytes: 1000000
    - path: "src/test-hooks/offscreen-hooks.ts"
      provides: "installFakeDisplayMedia() rewritten — SYNCHRONOUS module-load function; mints MediaStream from HTMLVideoElement.captureStream(30) on first getDisplayMedia call (lazy first-frame wait inside fakeGetDisplayMedia closure); displaySurface monkey-patch preserved; lifecycle (idempotent install + idempotent uninstall) preserved; A23 constraints capture preserved; all 6 existing bridge ops (install-fake-display-media + dispatch-ended + has-stream + get-display-surface + get-segment-count + get-last-getDisplayMedia-constraints) preserved with their original sync return contract"
      contains: "videoEl.captureStream"
    - path: "globals.d.ts"
      provides: "Ambient declaration for `*.webm?url` Vite asset import (mirrors existing `*.svg?url` block at lines 34-37)"
      contains: "webm?url"
    - path: "manifest.json"
      provides: "Explicit web_accessible_resources entry for assets/*.webm — pre-decided per planner iter-2 BLOCKER 1 remediation; production dist/ has zero *.webm assets so the entry is inert there; test dist-test/ has the hashed asset and the entry authorizes chrome-extension://<id>/assets/<hash>.webm access from the offscreen document context."
      contains: "assets/*.webm"
    - path: "tests/background/no-test-hooks-in-prod-bundle.test.ts"
      provides: "Tier-2 invariant: 'synthetic-display-source' filename returns 0 hits across dist/ — canary for accidental test-hook inlining into production chunk. Tier-1 inventory at 12 entries UNCHANGED; this is a NEW Tier-2 entry alongside (does not count against the 12 lockstep)."
      contains: "synthetic-display-source"
    - path: "tests/uat/extension-page-harness.ts"
      provides: "NO EDIT NEEDED per Plan 04-04 REVISION iter-2 Option B — assertA2 is reused as the canonical prime entrypoint; A33 logic lives entirely in driveA33 (host-side) + the inline page.evaluate dispatch. The Plan 04-04 SUMMARY post-debug amendment confirms this is the canonical pattern."
      contains: "__mokoshHarness"
    - path: "tests/uat/lib/harness-page-driver.ts"
      provides: "driveA33(page, browser, extensionId, downloadsDir) host-side driver implementing the 5-min idle + stopServiceWorker + SAVE_ARCHIVE + JSZip video-size check (Plan 04-04 Pattern 4 verbatim; REVISION iter-2 Option B inline SAVE_ARCHIVE dispatch)"
      contains: "driveA33"
    - path: "tests/uat/harness.test.ts"
      provides: "driveA33 import + driveA33Wrapped wrapped-driver const + drivers-array push entry with SKIP_LONG_UAT env-gate (per Plan 04-04 Wave 1 spec verbatim)"
      contains: "driveA33Wrapped"
  key_links:
    - from: "src/test-hooks/offscreen-hooks.ts installFakeDisplayMedia (sync top-level + lazy closure)"
      to: "tests/uat/fixtures/synthetic-display-source.webm via Vite ?url import"
      via: "import syntheticDisplaySourceUrl from '../../tests/uat/fixtures/synthetic-display-source.webm?url' (resolves to chrome-extension://<id>/assets/<hash>.webm at test bundle time; chrome-extension:// scheme authorized via manifest.json web_accessible_resources assets/*.webm entry)"
      pattern: "synthetic-display-source\\.webm\\?url"
    - from: "manifest.json web_accessible_resources"
      to: "dist-test/assets/<hash>.webm (test bundle only; production has zero *.webm assets)"
      via: "explicit resources: ['assets/*.webm'] entry alongside the existing src/welcome/welcome.html entry"
      pattern: "assets/\\*\\.webm"
    - from: "src/test-hooks/offscreen-hooks.ts fakeGetDisplayMedia closure"
      to: "videoEl readiness gate (readyState >= HAVE_FUTURE_DATA + .play()) + videoEl.captureStream(30) + displaySurface monkey-patch"
      via: "first-call lazy path awaits canplay/error + .play(); subsequent calls fast-path the cached-ready videoEl; mintStream(); patchDisplaySurface(stream); return stream"
      pattern: "readyState.*HAVE_FUTURE_DATA|videoEl\\.captureStream"
    - from: "tests/uat/harness.test.ts driveA33Wrapped"
      to: "tests/uat/lib/harness-page-driver.ts driveA33(page, browser, extensionId, downloadsDir)"
      via: "(page) => driveA33(page, handles.browser, handles.extensionId, handles.downloadsDir)"
      pattern: "handles\\.browser.*handles\\.extensionId"
    - from: "tests/uat/lib/harness-page-driver.ts driveA33 video-size check"
      to: "zip.file('video/last_30sec.webm') -> byteLength > 100_000"
      via: "JSZip.loadAsync + entry.async('uint8array')"
      pattern: "video/last_30sec\\.webm"
---

<objective>
**Methodology reframe for ROADMAP SC #1.** Per debug session-2 (`.planning/debug/sw-offscreen-persistence-investigation-session-2.md`, commit `4ea1bbb`), the Plan 04-04 SPIKE FAILED outcome (8505 bytes) is empirically REFUTED as an architectural failure. Three independent probes converged on the canonical NO answer:

1. **Segment-count probes** at POST-PRIME/PRE-KILL/POST-KILL: count=0 / count=3 / count=3 — segments accumulated correctly AND survived the SW kill. The `let segments: Blob[] = []` RAM-only architecture (src/offscreen/recorder.ts:91) is NOT broken.
2. **Step C variant** (SPIKE_SKIP_SW_KILL=1; no worker.close()): IDENTICAL 8505-byte failure — Puppeteer CDP `worker.close()` is NOT the cause.
3. **Direct Remux logs** (visible because SW respawn was skipped in Step C): `Segment ts=1..3: 0 frames, duration=0ms, trackInfo=320x180`; `Remux complete: 0 frames, total timeline=0ms, output=8505 bytes`.

**Root cause:** `installFakeDisplayMedia()` at `src/test-hooks/offscreen-hooks.ts:139-264` mints a `canvas.captureStream(30)` from a hidden -9999px-offset 320x180 canvas. Despite the existing `setInterval(drawFrame, 33ms)` belt-and-suspenders against RAF throttling, **headless-Chromium aggressively throttles MediaRecorder on invisible-canvas sources** (Chrome bug 653548; chromium auto-throttled-screen-capture design doc; sendrec.eu "Why Canvas Breaks Your Screen Recorder"). The MediaRecorder emits structurally-valid WebM with valid V_VP9 track metadata (320x180) but **zero VP9 frames per segment** across the 5-min idle window.

**Fix:** Replace the canvas.captureStream source with an `HTMLVideoElement` playing a bundled WebM (Option 2 from session-2 recommendations). Video-file-backed `videoEl.captureStream(30)` is not subject to invisible-canvas throttling — the source is a real media element with a real decoded frame timeline. The displaySurface monkey-patch (production code's monitor-only gate) is preserved verbatim; the lifecycle (idempotent install + uninstall) is preserved; the existing bridge ops (install-fake-display-media + dispatch-ended + has-stream + get-display-surface + get-segment-count + get-last-getDisplayMedia-constraints) are preserved.

**Iter-2 revision (per checker iter-1 findings at `.planning/phases/04-harden-clean-up-optional/04-08-CHECKER-iter-1.md`, commit `051813e`):**

- **BLOCKER 1 resolution — bundling strategy pre-decided.** Vite `?url` import emits the 1.9 MB WebM as `dist-test/assets/<hash>.webm` (extracted-asset path; not inlined because the size is three orders of magnitude above `assetsInlineLimit: 4096`). The `@crxjs/vite-plugin` auto-WAR behavior for extracted media assets in offscreen-document context is empirically untested in this codebase. **Pre-emptive remediation: add an explicit `web_accessible_resources` entry for `assets/*.webm`** in `manifest.json`. Production `dist/` has zero `*.webm` assets so the entry is inert there (no production attack surface); test `dist-test/` has the hashed asset and the entry authorizes the `chrome-extension://<id>/assets/<hash>.webm` URL form from the offscreen document context. No executor improvisation; the bundling strategy is locked-in BEFORE Task 1 begins.

- **BLOCKER 2 resolution — eager-install contract preserved.** `installFakeDisplayMedia()` remains **SYNCHRONOUS** at module load (matching the existing eager call at lines 533-537). The video element creation + `document.body.appendChild(videoEl)` + monkey-patch assignment to `navigator.mediaDevices.getDisplayMedia` all execute synchronously. The first-frame readiness await (canplay + `.play()`) is **deferred INTO the fakeGetDisplayMedia closure** (lazy first-frame pattern). The first time `getDisplayMedia()` is called (which happens inside `recorder.startRecording` AFTER recorder.ts:46-48 top-level await resolves and AFTER recorder.bootstrap), the closure awaits `videoEl.readyState >= HAVE_FUTURE_DATA` if not already ready, then calls `videoEl.captureStream(30)`, applies `patchDisplaySurface`, and returns the MediaStream. Subsequent `getDisplayMedia` calls fast-path the cached-ready video element. Zero race window with the eager-install contract.

**Revival path:** Once methodology produces real frames, re-run `tests/uat/spike-a33-sw-persistence.ts` — it MUST exit 0 with `videoSize > 100_000`. Then land the A33 harness assertion per the original Plan 04-04 Pattern 4 verbatim: `driveA33` host-side driver + orchestrator wiring + `SKIP_LONG_UAT` env-gate. The `stopServiceWorker(browser, extensionId)` helper from Plan 04-04 (committed at `3726eee`) is REUSED verbatim — no new test-only symbols introduced; FORBIDDEN_HOOK_STRINGS inventory unchanged at 12. A new Tier-2 sub-invariant ('synthetic-display-source' filename = 0 hits in dist/) lands alongside, codifying the production-bundle leak canary.

Purpose: Closes ROADMAP SC #1 ("After running the extension idle for >5 minutes, then exporting, the archive still contains a non-empty video buffer") within v1 by reframing the verification methodology (NOT the architecture). Honors the spike-FAILED-but-architecture-OK verdict from debug session-2; rejects the previously-proposed IndexedDB persistence plan-fix (which would not have closed SC #1 — the spike would STILL produce 8505 bytes after IDB lands because the failure is in the test's fake stream, not in segment persistence).

Output: 1 NEW bundled fixture (`tests/uat/fixtures/synthetic-display-source.webm`); rewrite of `installFakeDisplayMedia()` (canvas -> HTMLVideoElement; SYNC install + LAZY first-frame); 1 ambient module declaration for `*.webm?url`; 1 explicit `web_accessible_resources` entry for `assets/*.webm`; 1 NEW harness assertion (A33; harness count 33->34); driveA33 + orchestrator wiring; spike script re-runs PASSED; 1 NEW Tier-2 filename-leak gate. ROADMAP SC #1 flips OPEN -> GREEN.
</objective>

<execution_context>
@$HOME/.claude/get-shit-done/workflows/execute-plan.md
@$HOME/.claude/get-shit-done/templates/summary.md
</execution_context>

<context>
@.planning/PROJECT.md
@.planning/ROADMAP.md
@.planning/STATE.md
@.planning/phases/04-harden-clean-up-optional/04-CONTEXT.md
@.planning/phases/04-harden-clean-up-optional/04-PATTERNS.md
@.planning/phases/04-harden-clean-up-optional/04-04-PLAN.md
@.planning/phases/04-harden-clean-up-optional/04-04-SUMMARY.md
@.planning/phases/04-harden-clean-up-optional/04-08-CHECKER-iter-1.md
@.planning/debug/sw-offscreen-persistence-investigation-session-2.md

# Source files — locus of the methodology reframe
@src/test-hooks/offscreen-hooks.ts
@src/offscreen/recorder.ts
@tests/uat/extension-page-harness.ts
@tests/uat/lib/harness-page-driver.ts
@tests/uat/harness.test.ts
@tests/uat/lib/launch.ts
@tests/uat/spike-a33-sw-persistence.ts
@tests/background/no-test-hooks-in-prod-bundle.test.ts

# Vite ?url import precedent (Plan 01-10 mokosh-mark.svg pattern)
@src/welcome/welcome.ts
@globals.d.ts
@manifest.json
@vite.config.ts
@vite.test.config.ts

# Prior plan SUMMARYs — direct ancestors
@.planning/phases/01-stabilize-video-pipeline/01-10-SUMMARY.md
@.planning/phases/03-spec-10-smoke-verification-dom-event-log-verification/03-04-SUMMARY.md

<interfaces>
<!-- Key shapes the executor consumes directly. Extracted from codebase + debug session-2 + checker iter-1 2026-05-22. -->

From src/test-hooks/offscreen-hooks.ts:139-264 (CURRENT installFakeDisplayMedia — the methodology failure locus, SYNCHRONOUS):
```typescript
// CURRENT (broken under 5-min headless idle per debug session-2 verdict):
// CRITICAL: this is SYNCHRONOUS — the monkey-patch on
// navigator.mediaDevices.getDisplayMedia is in place BEFORE the
// recorder.ts:46-48 await import('../test-hooks/offscreen-hooks')
// resolves. This is the eager-install contract.
export function installFakeDisplayMedia(): void {  // SYNC — no Promise return
  if (fakeInstalled) return;
  fakeInstalled = true;
  const canvas = document.createElement('canvas');
  canvas.width = 320; canvas.height = 180;
  // ... -9999px style + appendChild + drawFrame + setInterval ...
  const mintStream = (): MediaStream => {
    const stream = canvas.captureStream(30);  // <- THE THROTTLING SOURCE
    patchDisplaySurface(stream);
    return stream;
  };
  const fakeGetDisplayMedia = async (
    constraints?: DisplayMediaStreamOptions,
  ): Promise<MediaStream> => {
    lastGetDisplayMediaConstraints = constraints ?? null;
    return mintStream();  // SYNC body; async only for the contract shape
  };
  (navigator.mediaDevices as unknown as {
    getDisplayMedia: typeof fakeGetDisplayMedia;
  }).getDisplayMedia = fakeGetDisplayMedia;  // SYNC monkey-patch — pre-resolve point
}
```

REPLACEMENT pattern (HTMLVideoElement.captureStream — Plan 04-08, SYNC install + LAZY first-frame closure):
```typescript
// Plan 04-08 methodology reframe — video-file-backed MediaStream.
// canvas.captureStream(30) on a hidden -9999px canvas is throttled to
// near-zero frames per second under headless Chromium 5-min idle
// (Chrome bug 653548; debug session-2 2026-05-22). An HTMLVideoElement
// playing a real WebM source is NOT subject to invisible-canvas
// throttling because the source has a real decoded frame timeline
// independent of canvas pixel mutations.
//
// CRITICAL CONTRACT (iter-2 BLOCKER 2 fix): installFakeDisplayMedia()
// remains SYNCHRONOUS. The video element creation + DOM append +
// monkey-patch on navigator.mediaDevices.getDisplayMedia execute
// synchronously at function call time. The canplay wait + .play() are
// deferred INTO the fakeGetDisplayMedia closure so the eager module-
// load call at lines 533-537 still installs the monkey-patch BEFORE
// recorder.ts:46-48 top-level await resolves. No race window with the
// recorder.startRecording call.
//
// References:
//   - debug session-2 verdict at .planning/debug/sw-offscreen-persistence-investigation-session-2.md
//   - HTMLVideoElement.captureStream:
//     https://developer.mozilla.org/docs/Web/API/HTMLMediaElement/captureStream
//   - Chrome bug 653548 (auto-throttled canvas captureStream):
//     https://bugs.chromium.org/p/chromium/issues/detail?id=653548
//   - HTMLMediaElement.readyState (HAVE_FUTURE_DATA == 3):
//     https://developer.mozilla.org/docs/Web/API/HTMLMediaElement/readyState
//   - iter-2 BLOCKER 2 remediation: .planning/phases/04-harden-clean-up-optional/04-08-CHECKER-iter-1.md

import syntheticDisplaySourceUrl from '../../tests/uat/fixtures/synthetic-display-source.webm?url';

// Module-level cell — populated by the SYNC install; consumed by the
// LAZY closure. Mutable because the closure may need to await readiness
// across multiple calls before the cached state stabilizes.
let fakeVideoEl: HTMLVideoElement | null = null;
let fakeVideoReadyPromise: Promise<void> | null = null;

export function installFakeDisplayMedia(): void {  // SYNC — return type unchanged from current
  if (fakeInstalled) return;
  fakeInstalled = true;

  // SYNC: create + append + style — these complete on the same tick.
  const videoEl = document.createElement('video');
  videoEl.src = syntheticDisplaySourceUrl;
  videoEl.loop = true;       // loop indefinitely so 5-min idle has source frames
  videoEl.muted = true;      // muted required for autoplay per Chrome policy
  videoEl.autoplay = true;   // ensure playback starts without user gesture
  videoEl.playsInline = true;
  videoEl.preload = 'auto';  // start fetching/decoding immediately
  videoEl.style.position = 'fixed';
  videoEl.style.top = '-9999px';
  videoEl.style.left = '-9999px';
  document.body.appendChild(videoEl);
  fakeVideoEl = videoEl;

  // SYNC: start the readiness Promise NOW so it has the maximum head
  // start before the first getDisplayMedia call. The Promise resolves
  // when readyState reaches HAVE_FUTURE_DATA (canplay event). If the
  // video is already ready by the time fakeGetDisplayMedia is invoked,
  // the closure's `await fakeVideoReadyPromise` resolves immediately.
  //
  // The .play() call is fire-and-forget here — we don't await it at
  // install time (that would block the SYNC contract). We DO chain it
  // off the canplay resolution inside the Promise body so the closure
  // can rely on "ready AND playing" once the Promise resolves.
  fakeVideoReadyPromise = new Promise<void>((resolve, reject) => {
    const onCanPlay = (): void => {
      videoEl.removeEventListener('canplay', onCanPlay);
      videoEl.removeEventListener('error', onError);
      // Chain .play() — required because autoplay attr is best-effort.
      videoEl.play().then(() => resolve()).catch((err) => {
        reject(new Error(
          `synthetic-display-source.webm play() rejected: ${
            err instanceof Error ? err.message : String(err)
          } (autoplay-blocked or codec-unsupported in headless context)`
        ));
      });
    };
    const onError = (): void => {
      videoEl.removeEventListener('canplay', onCanPlay);
      videoEl.removeEventListener('error', onError);
      reject(new Error(
        'synthetic-display-source.webm failed to load (media error; verify WAR entry + dist-test/assets/<hash>.webm reachable)'
      ));
    };
    videoEl.addEventListener('canplay', onCanPlay);
    videoEl.addEventListener('error', onError);
  });

  // SYNC: monkey-patch — the eager-install contract requires this assignment
  // to happen synchronously at module load (before recorder.ts:46-48 top-
  // level await resolves). The closure body is async (matches the real
  // getDisplayMedia signature) but the assignment itself is synchronous.
  const fakeGetDisplayMedia = async (
    constraints?: DisplayMediaStreamOptions,
  ): Promise<MediaStream> => {
    // Plan 01-14 A23 capture (preserved verbatim).
    lastGetDisplayMediaConstraints = constraints ?? null;

    // LAZY FIRST-FRAME: await the readiness Promise. First call may
    // block ~50-500ms while the video decodes its first frame. Cached
    // resolution thereafter — subsequent calls observe the resolved
    // Promise and proceed immediately.
    if (fakeVideoReadyPromise !== null) {
      await fakeVideoReadyPromise;
    }
    if (fakeVideoEl === null) {
      // Defensive — module-level state was nulled by uninstall. Reject
      // explicitly so callers see a clear error rather than NPE.
      throw new Error('fake getDisplayMedia called after uninstall');
    }
    return mintStream();
  };
  (navigator.mediaDevices as unknown as {
    getDisplayMedia: typeof fakeGetDisplayMedia;
  }).getDisplayMedia = fakeGetDisplayMedia;
}

const mintStream = (): MediaStream => {
  if (fakeVideoEl === null) {
    throw new Error('mintStream called before fakeVideoEl initialized');
  }
  // captureStream(30) — request 30 fps; the actual cadence is driven
  // by the source video's frame timeline.
  const stream = (fakeVideoEl as HTMLVideoElement & {
    captureStream: (fps?: number) => MediaStream;
  }).captureStream(30);
  patchDisplaySurface(stream);  // preserve existing monkey-patch
  return stream;
};
```

From src/test-hooks/offscreen-hooks.ts:528-537 (CURRENT eager-install at module load — UNCHANGED in iter-2):
```typescript
// PROTOTYPE: install the fake getDisplayMedia eagerly so production
// recorder.startRecording will use the synthetic stream on its first
// call — no chicken-and-egg with the bridge install op. Wrap in a
// try so any DOM-not-ready edge case does not block module init.
try {
  installFakeDisplayMedia();  // STILL SYNC — eager-install contract preserved
} catch (e) {
  console.warn("[offscreen-hooks] eager installFakeDisplayMedia failed:", e);
}
```

From src/offscreen/recorder.ts:46-48 (the top-level await resume point — eager-install contract dependent):
```typescript
let testHooks: typeof import('../test-hooks/offscreen-hooks') | null = null;
if (__MOKOSH_UAT__) {
  testHooks = await import('../test-hooks/offscreen-hooks');
}
// By the time the await resolves, offscreen-hooks's module-load eager
// call has already executed installFakeDisplayMedia() SYNCHRONOUSLY,
// which means navigator.mediaDevices.getDisplayMedia is ALREADY patched
// to the fakeGetDisplayMedia closure. recorder.startRecording's
// `await navigator.mediaDevices.getDisplayMedia(...)` resolves with the
// synthetic stream — the lazy first-frame wait happens inside the closure,
// not at install time.
```

From src/welcome/welcome.ts:46 (Plan 01-10 Vite ?url precedent — direct analog for SVG):
```typescript
import markUrl from '../shared/brand/mokosh-mark.svg?url';
```

From globals.d.ts:34-37 (Plan 01-10 ambient module decl — direct analog to copy):
```typescript
declare module '*.svg?url' {
  const url: string;
  export default url;
}
// Plan 04-08 adds the parallel block:
declare module '*.webm?url' {
  const url: string;
  export default url;
}
```

From manifest.json:20-25 (CURRENT web_accessible_resources block — Plan 04-08 appends one entry):
```json
"web_accessible_resources": [
  {
    "resources": ["src/welcome/welcome.html"],
    "matches": ["<all_urls>"]
  }
],
```

Plan 04-08 iter-2 BLOCKER 1 fix — append a second resources entry:
```json
"web_accessible_resources": [
  {
    "resources": ["src/welcome/welcome.html"],
    "matches": ["<all_urls>"]
  },
  {
    "resources": ["assets/*.webm"],
    "matches": ["<all_urls>"]
  }
],
```

From src/test-hooks/offscreen-hooks.ts:271-291 (uninstallFakeDisplayMedia — preserve idempotent teardown; adapted for videoEl):
```typescript
export function uninstallFakeDisplayMedia(): void {
  if (!fakeInstalled) return;
  fakeInstalled = false;
  if (fakeVideoEl !== null) {
    try { fakeVideoEl.pause(); } catch { /* ignore */ }
    fakeVideoEl.remove();
    fakeVideoEl = null;
  }
  fakeVideoReadyPromise = null;  // drop the Promise reference
  // We deliberately do NOT restore the original getDisplayMedia — the
  // offscreen document is throwaway and gets a fresh navigator on the
  // next createDocument() anyway.
}
```

From tests/uat/lib/harness-page-driver.ts:68-80 (stopServiceWorker helper — REUSED verbatim from Plan 04-04):
```typescript
// Already committed at 3726eee; Plan 04-08 reuses without modification.
export async function stopServiceWorker(browser: Browser, extensionId: string): Promise<void> {
  const host = `chrome-extension://${extensionId}`;
  const target = await browser.waitForTarget(
    (t) => t.type() === 'service_worker' && t.url().startsWith(host),
  );
  const worker = await target.worker();
  if (worker !== null) {
    await worker.close();
  }
}
```

From Plan 04-04 PLAN.md Pattern 4 (driveA33 host-side body — REVIVED VERBATIM under valid methodology):
```typescript
const A33_IDLE_WAIT_MS = 5 * 60 * 1000;
const A33_NEW_SW_BOOT_MS = 500;
const A33_OVERALL_TIMEOUT_MS = A33_IDLE_WAIT_MS + 60_000;
const A33_SAVE_ARCHIVE_TIMEOUT_MS = 15_000;
const A33_DOWNLOAD_SETTLE_MS = 5_000;
const A33_VIDEO_SIZE_FLOOR_BYTES = 100_000;

export async function driveA33(
  page: Page,
  browser: Browser,
  extensionId: string,
  downloadsDir: string,
): Promise<AssertionRecord> {
  const r: AssertionRecord = { name: 'A33', passed: false, checks: [], diagnostics: [] };

  // Step 1: prime via __mokoshHarness.assertA2 (canonical fresh-recording bootstrap;
  // Plan 04-04 REVISION iter-2 Option B; verified via existing harness surface).
  await page.evaluate(async () => {
    const harness = (window as unknown as {
      __mokoshHarness: { assertA2: () => Promise<{ passed: boolean; error?: string }> };
    }).__mokoshHarness;
    const a2 = await harness.assertA2();
    if (!a2.passed) {
      throw new Error(`assertA2 priming failed: ${a2.error ?? '(no error)'}`);
    }
  });
  r.diagnostics.push('Step 1 OK: assertA2 prime -> REC');

  // Step 2: 5-min wall-clock idle.
  r.diagnostics.push(`Step 2: waiting ${A33_IDLE_WAIT_MS}ms for SW idle window`);
  await new Promise((res) => setTimeout(res, A33_IDLE_WAIT_MS));

  // Step 3: force SW termination via CDP.
  await stopServiceWorker(browser, extensionId);
  r.diagnostics.push('Step 3 OK: SW terminated via worker.close()');

  // Step 4: brief settle for SW teardown.
  await new Promise((res) => setTimeout(res, A33_NEW_SW_BOOT_MS));

  // Step 5: SAVE_ARCHIVE inline dispatch from harness-page realm
  // (Plan 04-04 REVISION iter-2 Option B; wakes SW event-driven).
  const saveResult = await page.evaluate(
    (timeoutMs: number) =>
      new Promise<{ success: boolean; error?: string }>((resolve) => {
        const timer = setTimeout(() => {
          resolve({ success: false, error: `SAVE_ARCHIVE timed out after ${timeoutMs}ms` });
        }, timeoutMs);
        chrome.runtime.sendMessage({ type: 'SAVE_ARCHIVE' }, (response: unknown) => {
          clearTimeout(timer);
          if (chrome.runtime.lastError !== undefined) {
            resolve({ success: false, error: String(chrome.runtime.lastError.message) });
            return;
          }
          resolve(response as { success: boolean; error?: string });
        });
      }),
    A33_SAVE_ARCHIVE_TIMEOUT_MS,
  );
  r.checks.push({
    name: 'A33.1: SAVE_ARCHIVE ack success after 5-min idle + SW kill',
    expected: true,
    actual: saveResult.success,
    passed: saveResult.success === true,
  });

  // Step 6: settle for chrome.downloads to finish.
  await new Promise((res) => setTimeout(res, A33_DOWNLOAD_SETTLE_MS));

  // Step 7: locate zip + measure video entry.
  const zipPath = findLatestZip(downloadsDir);
  if (zipPath === null) {
    r.checks.push({ name: 'A33.0: zip present', expected: '>=1 zip', actual: 'none', passed: false });
    r.passed = false;
    return r;
  }
  const zip = await JSZip.loadAsync(readFileSync(zipPath));
  const videoEntry = zip.file('video/last_30sec.webm');
  const videoSize = videoEntry !== null
    ? (await videoEntry.async('uint8array')).byteLength
    : 0;
  r.checks.push({
    name: 'A33.2: video/last_30sec.webm size > 0 (buffer survived SW eviction)',
    expected: '>0',
    actual: String(videoSize),
    passed: videoSize > 0,
  });
  r.checks.push({
    name: 'A33.3: video size > 100 KB (sanity floor; real archives 1-3 MB)',
    expected: `>${A33_VIDEO_SIZE_FLOOR_BYTES}`,
    actual: String(videoSize),
    passed: videoSize > A33_VIDEO_SIZE_FLOOR_BYTES,
  });

  r.passed = r.checks.every((c) => c.passed);
  return r;
}
```

From tests/uat/harness.test.ts:486 (orchestrator drivers-array — append site for A33):
```typescript
// Plan 04-08 — driveA33 lands HERE, after the existing A32 entry at line 486.
{
  name: 'A33',
  drive: process.env.SKIP_LONG_UAT === '1'
    ? async (): Promise<AssertionRecord> => ({
        name: 'A33',
        passed: true,
        checks: [],
        diagnostics: ['A33 SKIPPED (SKIP_LONG_UAT=1; unset to run 5-min idle test)'],
      })
    : driveA33Wrapped,
},
```

From tests/fixtures/last_30sec.webm (existing internal project artifact — REMAINS IN PLACE per advisory 3; the new tests/uat/fixtures/synthetic-display-source.webm is a SECOND copy at a different location):
- size: 1.9 MB (1888636 bytes verified via ls)
- codec: VP9
- dimensions: 1142x1044
- license: internal project capture (CC0-equivalent project-owned)
- A direct copy to `tests/uat/fixtures/synthetic-display-source.webm` is the baseline (zero-cost; already proven to play in Chrome via Plan 01-07).

From tests/background/no-test-hooks-in-prod-bundle.test.ts (CURRENT Tier-1 inventory at 12 entries; iter-2 adds 1 NEW Tier-2 sub-invariant):
```typescript
// Tier-1: 12-entry FORBIDDEN_HOOK_STRINGS lockstep with tests/uat/harness.test.ts.
// Plan 04-08 leaves this UNCHANGED.
//
// Tier-2 NEW (Plan 04-08 iter-2 — WARNING 5 remediation): single canary
// gate that 'synthetic-display-source' does not leak into dist/. Test-only
// fixture filename — the gated import in offscreen-hooks.ts is tree-shaken
// in production per __MOKOSH_UAT__; this gate catches any future regression
// that accidentally inlines test-hooks into the production chunk.
```
</interfaces>
</context>

<tasks>

<task type="auto">
  <name>Task 1: Bundle WebM fixture + pre-emptive WAR entry + replace canvas.captureStream with HTMLVideoElement.captureStream (SYNC install + LAZY first-frame)</name>
  <files>tests/uat/fixtures/synthetic-display-source.webm, src/test-hooks/offscreen-hooks.ts, globals.d.ts, manifest.json, vite.config.ts, vite.test.config.ts, tests/background/no-test-hooks-in-prod-bundle.test.ts</files>
  <read_first>src/test-hooks/offscreen-hooks.ts (full file — installFakeDisplayMedia at lines 139-264 + uninstallFakeDisplayMedia at 271-291 + eager-install at 528-537), src/offscreen/recorder.ts:40-60 (the top-level await import resume point that depends on eager-install contract), src/welcome/welcome.ts:30-50 (Vite ?url import precedent), globals.d.ts (full — ambient module declaration pattern), manifest.json (full — web_accessible_resources block at line 20), vite.config.ts (full — rollupOptions.input + nodePolyfills config), vite.test.config.ts (full — test-build entry mirror), tests/background/no-test-hooks-in-prod-bundle.test.ts (full — Tier-1 invariant + the Tier-2 add site), tests/fixtures/last_30sec.webm (verify file exists + VP9 codec + ~1.9 MB), tests/uat/spike-a33-sw-persistence.ts (full — to understand the exact prime + SAVE flow the new methodology will be tested against), .planning/debug/sw-offscreen-persistence-investigation-session-2.md (Resolution section — fix recommendations), .planning/phases/04-harden-clean-up-optional/04-08-CHECKER-iter-1.md (BLOCKER 1 + BLOCKER 2 + WARNING 1/2/5 — the specific remediation guidance)</read_first>
  <action>
**Step 1 — Bundle the WebM fixture (advisory 3 dual-location note).**
- Create directory: `mkdir -p tests/uat/fixtures/`.
- Copy `tests/fixtures/last_30sec.webm` to `tests/uat/fixtures/synthetic-display-source.webm`. The existing artifact is a 1.9 MB VP9 WebM internally captured by this project's MediaRecorder pipeline — CC0-equivalent project-owned per the "internal capture" provenance documented in `.planning/STATE.md` Phase 1 Closure Notes. Verify codec via `ffprobe -v error -show_entries stream=codec_name,width,height -of default=nw=1 tests/uat/fixtures/synthetic-display-source.webm` reports `codec_name=vp9`.
- The fixture must be >=1 MB AND >=30 seconds duration (loopable). The existing 1.9 MB capture satisfies size; duration is `N/A` per ffprobe (live-capture WebM lacks a duration tag), BUT the 1.9 MB VP9 at 400 kbps yields ~38s of decoded timeline — sufficient for the 5-min spike via `videoEl.loop = true`. If the executor wants a stricter contract, regenerate via `ffmpeg -f lavfi -i testsrc=duration=35:size=320x180:rate=30 -c:v libvpx-vp9 -b:v 400k tests/uat/fixtures/synthetic-display-source.webm` (this is OPTIONAL — the copy baseline works; only regenerate if the copy's duration tag is load-bearing for the chosen tests).
- **advisory 3 note**: `tests/fixtures/last_30sec.webm` remains in place (Plan 01-07 regression fixture; not affected). The new path at `tests/uat/fixtures/synthetic-display-source.webm` is a SECOND copy under the UAT subtree — this is intentional because the Vite ?url import in `src/test-hooks/offscreen-hooks.ts` resolves cleanly from `../../tests/uat/fixtures/...` without crossing a non-bundled subtree (the `tests/fixtures/` directory is excluded from the test bundle's input set; the `tests/uat/fixtures/` directory is implicitly included as a transitive import of the offscreen-hooks module).
- Decision (per `feedback-no-unilateral-scope-reduction.md`): the executor's default is the COPY path (zero-cost, project-owned, already proven to play in Chrome per Plan 01-07). Regeneration is an OPTIONAL upgrade if the baseline fails to loop cleanly in headless captureStream.

**Step 2 — Add ambient module declaration for `*.webm?url`.**
- Edit `globals.d.ts`. After the existing `declare module '*.svg?url' { ... }` block at lines 34-37, append:
  ```typescript
  // Plan 04-08 — Vite `?url` import for bundled test-only WebM fixture
  // (tests/uat/fixtures/synthetic-display-source.webm). Mirrors the
  // Plan 01-10 mokosh-mark.svg precedent; only gated test builds resolve
  // the import (offscreen-hooks.ts is tree-shaken in production per
  // `__MOKOSH_UAT__`).
  declare module '*.webm?url' {
    const url: string;
    export default url;
  }
  ```

**Step 3 — Rewrite `installFakeDisplayMedia()` to use HTMLVideoElement.captureStream — SYNCHRONOUS install + LAZY first-frame closure (iter-2 BLOCKER 2 fix).**

**Critical contract:** `installFakeDisplayMedia()` MUST remain SYNCHRONOUS (no `async`/`await` in the function declaration). The eager-install at `src/test-hooks/offscreen-hooks.ts:528-537` calls it synchronously at module load; the `await import('../test-hooks/offscreen-hooks')` chain at `src/offscreen/recorder.ts:46-48` depends on the monkey-patch being in place BEFORE the await resolves. Converting `installFakeDisplayMedia()` to async would introduce a race window where `recorder.startRecording` could call the REAL `navigator.mediaDevices.getDisplayMedia` (the picker would hang in headless mode). DO NOT convert to async. DO NOT change the function's return type.

**Sub-step 3a — Add top-of-module import (after existing imports at line 49):**
```typescript
// Plan 04-08 — bundled WebM source for HTMLVideoElement-backed MediaStream.
// Replaces the prior canvas.captureStream(30) source which was throttled
// to 0 frames/segment under 5-min headless Chromium idle (Chrome bug
// 653548; debug session-2 verdict 2026-05-22). The video file's real
// decoded frame timeline is not subject to invisible-canvas throttling.
//
// The `?url` import resolves to a Vite-emitted hashed asset URL only in
// test builds (offscreen-hooks.ts is gated by `__MOKOSH_UAT__` in
// src/offscreen/recorder.ts and tree-shaken in production). The asset
// emission path is dist-test/assets/<hash>.webm; the chrome-extension://
// scheme access from the offscreen document is authorized by the explicit
// web_accessible_resources entry for assets/*.webm in manifest.json
// (iter-2 BLOCKER 1 remediation; pre-decided to avoid executor improvisation).
//
// References:
//   - .planning/debug/sw-offscreen-persistence-investigation-session-2.md
//   - .planning/phases/04-harden-clean-up-optional/04-08-CHECKER-iter-1.md
//   - https://developer.mozilla.org/docs/Web/API/HTMLMediaElement/captureStream
//   - Chrome bug 653548: https://bugs.chromium.org/p/chromium/issues/detail?id=653548
//   - HTMLMediaElement.readyState: https://developer.mozilla.org/docs/Web/API/HTMLMediaElement/readyState
import syntheticDisplaySourceUrl from '../../tests/uat/fixtures/synthetic-display-source.webm?url';
```

**Sub-step 3b — Update module-level state declarations (lines ~97-100). Replace canvas-specific cells with video-specific cells:**
```typescript
// REPLACE:
// let fakeCanvas: HTMLCanvasElement | null = null;
// let fakeAnimationHandle: number | null = null;
// let fakeDrawInterval: ReturnType<typeof setInterval> | null = null;
//
// WITH:
let fakeVideoEl: HTMLVideoElement | null = null;
// Plan 04-08 BLOCKER 2 (iter-2): lazy first-frame Promise. SYNC install
// kicks off the readiness chain (canplay + .play()); the Promise resolves
// when the video element is ready to captureStream. The fakeGetDisplayMedia
// closure awaits this Promise on each call — first call may block ~50-500ms;
// subsequent calls observe the already-resolved Promise and proceed
// immediately. Nulled by uninstallFakeDisplayMedia.
let fakeVideoReadyPromise: Promise<void> | null = null;
```

**Sub-step 3c — Replace the `installFakeDisplayMedia` body (lines 139-264). Keep the function signature SYNCHRONOUS — `export function installFakeDisplayMedia(): void`. Preserve:**
- Idempotency guard (`if (fakeInstalled) return;`).
- `fakeInstalled = true` early assignment (matches existing contract).
- The `lastGetDisplayMediaConstraints` capture (A23 contract).
- The `patchDisplaySurface(stream)` helper (defined inside the function as in current source; survives the rewrite).
- The `mintStream()` factory pattern (fresh MediaStream per `getDisplayMedia` call).
- The fakeGetDisplayMedia closure shape (`async` callable; cast-through-unknown for navigator.mediaDevices.getDisplayMedia assignment).
- The eager-install try/catch at lines 528-537 unchanged.

**New body (SYNC install + LAZY first-frame, code-snippet form per checker iter-1 BLOCKER 2 Option A):**
```typescript
export function installFakeDisplayMedia(): void {
  if (fakeInstalled) {
    return;
  }
  fakeInstalled = true;

  // SYNC PHASE — execute synchronously so the monkey-patch on
  // navigator.mediaDevices.getDisplayMedia is in place BEFORE
  // recorder.ts:46-48 top-level await resolves. Per debug session-2 +
  // iter-2 BLOCKER 2 — must NOT block on canplay or .play() here.

  // Build a hidden HTMLVideoElement playing the bundled WebM source.
  // The element stays off-screen (-9999px) so it has zero visual side
  // effect; loop=true ensures source frames never run out across the
  // 5-min spike window; muted=true is required for autoplay per the
  // Chrome autoplay policy (audio policy doesn't gate muted video).
  const videoEl = document.createElement('video');
  videoEl.src = syntheticDisplaySourceUrl;
  videoEl.loop = true;
  videoEl.muted = true;
  videoEl.autoplay = true;
  videoEl.playsInline = true;
  videoEl.preload = 'auto';
  videoEl.style.position = 'fixed';
  videoEl.style.top = '-9999px';
  videoEl.style.left = '-9999px';
  document.body.appendChild(videoEl);
  fakeVideoEl = videoEl;

  // Start the readiness Promise NOW so it has the maximum head start
  // before the first getDisplayMedia call. The Promise resolves when
  // canplay fires AND .play() resolves; rejects on error or play() reject
  // (autoplay blocked / codec unsupported). Stored in the module-level
  // cell so the closure can await it.
  //
  // WARNING 1 remediation (iter-2): autoplay reject path produces an
  // explicit error class identifier ('autoplay-blocked or codec-unsupported
  // in headless context') so a misconfigured fixture / hostile autoplay
  // policy surfaces as a clear failure signal — NOT a mysterious 0-frames
  // downstream. The spike's gating check on `videoSize > 100_000` will
  // fail with this error visible in the offscreen console capture (or in
  // the harness diagnostics), making the root cause unambiguous.
  fakeVideoReadyPromise = new Promise<void>((resolve, reject) => {
    const onCanPlay = (): void => {
      videoEl.removeEventListener('canplay', onCanPlay);
      videoEl.removeEventListener('error', onError);
      // Chain .play() — required because autoplay attr is best-effort.
      videoEl.play().then(() => resolve()).catch((err: unknown) => {
        reject(new Error(
          `synthetic-display-source.webm play() rejected: ${
            err instanceof Error ? err.message : String(err)
          } (autoplay-blocked or codec-unsupported in headless context)`
        ));
      });
    };
    const onError = (): void => {
      videoEl.removeEventListener('canplay', onCanPlay);
      videoEl.removeEventListener('error', onError);
      reject(new Error(
        'synthetic-display-source.webm failed to load (media error; '
        + 'verify WAR entry for assets/*.webm in manifest.json + '
        + 'dist-test/assets/<hash>.webm reachable via chrome-extension://)'
      ));
    };
    videoEl.addEventListener('canplay', onCanPlay);
    videoEl.addEventListener('error', onError);
  });

  /**
   * Apply the displaySurface monkey-patch to a freshly-minted stream's
   * video track. Production code's post-grant validation reads
   * `getSettings().displaySurface` and tears down + throws
   * 'wrong-display-surface' on anything but 'monitor' — the patch makes
   * the synthetic video stream satisfy that gate. WARNING 2 (iter-2):
   * this patch is verified to work with HTMLVideoElement.captureStream
   * tracks via the explicit sub-test in Task 1 verify block; the MDN-
   * documented contract on the returned track is the same writable
   * `getSettings` reference (per HTMLMediaElement.captureStream §Return
   * Value: "A new MediaStream object").
   */
  const patchDisplaySurface = (stream: MediaStream): void => {
    const videoTrack = stream.getVideoTracks()[0];
    if (videoTrack !== undefined) {
      const originalGetSettings = videoTrack.getSettings.bind(videoTrack);
      videoTrack.getSettings = ((): MediaTrackSettings => {
        const real = originalGetSettings();
        return {
          ...real,
          displaySurface: 'monitor',
        };
      }) as typeof videoTrack.getSettings;
    }
  };

  /**
   * Mint a FRESH MediaStream from the HTMLVideoElement. Each invocation
   * generates new tracks in 'live' state — required for the multi-
   * recording-lifecycle pattern (A6 stops the first stream's tracks via
   * dispatchEvent('ended'); A7 starts a new recording which calls
   * getDisplayMedia → must get a live stream, NOT the dead one A6
   * teardown left behind). The videoEl persists across calls; track refs
   * do not. This contract is preserved verbatim from the canvas variant.
   */
  const mintStream = (): MediaStream => {
    if (fakeVideoEl === null) {
      throw new Error('mintStream called before fakeVideoEl initialized — should be unreachable');
    }
    // captureStream(30) — request 30 fps; the actual cadence is driven
    // by the source video's frame timeline (HTMLMediaElement.captureStream
    // spec; non-standard but widely-implemented in Chrome since 2017).
    //
    // TypeScript cast through `&` intersection because HTMLMediaElement.
    // captureStream is non-standard and not in default lib.dom.d.ts at
    // all TS versions. The runtime surface is stable in Chrome MV3 target
    // (≥88 per manifest).
    const stream = (fakeVideoEl as HTMLVideoElement & {
      captureStream: (fps?: number) => MediaStream;
    }).captureStream(30);
    patchDisplaySurface(stream);
    return stream;
  };

  // LAZY ASYNC PHASE — fakeGetDisplayMedia awaits readiness on first call.
  // Subsequent calls observe the already-resolved Promise and proceed
  // immediately. The closure is async-shaped to match the real
  // getDisplayMedia signature; recorder.startRecording's
  // `await navigator.mediaDevices.getDisplayMedia(...)` is fully compatible.
  const fakeGetDisplayMedia = async (
    constraints?: DisplayMediaStreamOptions,
  ): Promise<MediaStream> => {
    // Plan 01-14 A23: capture the production call's constraints object
    // so the harness can verify `monitorTypeSurfaces: 'include'` reached
    // the call site. Default to null on undefined-args so the bridge op
    // reports an unambiguous "no args" signal rather than `undefined`.
    lastGetDisplayMediaConstraints = constraints ?? null;

    // LAZY FIRST-FRAME WAIT (iter-2 BLOCKER 2). The Promise was kicked
    // off synchronously at install time; by the time the production
    // recorder.startRecording reaches this call site (after recorder.ts
    // bootstrap + START_RECORDING handler dispatch), the video has had
    // a head start of ~50ms+ on its decode. Most calls observe a
    // resolved Promise here and proceed immediately. First call on a
    // cold offscreen may block ~50-500ms while canplay fires.
    if (fakeVideoReadyPromise !== null) {
      await fakeVideoReadyPromise;
    }
    if (fakeVideoEl === null) {
      // Defensive — module-level state was nulled by uninstall.
      throw new Error('fake getDisplayMedia called after uninstall');
    }
    return mintStream();
  };

  // SYNC MONKEY-PATCH — the eager-install contract requires this assignment
  // to happen synchronously at function call time. Cast through `unknown`
  // because MediaDevices.getDisplayMedia has multiple overloads.
  (navigator.mediaDevices as unknown as {
    getDisplayMedia: typeof fakeGetDisplayMedia;
  }).getDisplayMedia = fakeGetDisplayMedia;
}
```

**Sub-step 3d — Delete the canvas-specific code block (current lines ~160-199 in source: `const canvas = document.createElement('canvas')` + drawFrame + requestAnimationFrame + setInterval). The video-file source provides frames inherently — no synthetic frame driver needed. Remove all references to: `fakeCanvas`, `fakeAnimationHandle`, `fakeDrawInterval`, `drawFrame`, `frameCount`, `ctx`, `canvas.captureStream`.**

**Sub-step 3e — Update `uninstallFakeDisplayMedia()` (current lines 271-291) to teardown the video element instead of canvas. Keep function SYNCHRONOUS (return `void`, not `Promise<void>`):**
```typescript
export function uninstallFakeDisplayMedia(): void {
  if (!fakeInstalled) {
    return;
  }
  fakeInstalled = false;
  if (fakeVideoEl !== null) {
    try {
      fakeVideoEl.pause();
    } catch {
      // ignore pause errors during teardown (e.g., already paused)
    }
    fakeVideoEl.remove();
    fakeVideoEl = null;
  }
  // Drop the Promise reference so a subsequent install creates a fresh one.
  fakeVideoReadyPromise = null;
  // We deliberately do NOT restore the original getDisplayMedia — the
  // offscreen document is throwaway and gets a fresh navigator on the
  // next createDocument() anyway.
}
```

**Sub-step 3f — Verify the eager-install at lines 528-537 is UNCHANGED. The existing sync void call still works because `installFakeDisplayMedia()` remains a sync void function:**
```typescript
// UNCHANGED — preserves the eager-install contract per iter-2 BLOCKER 2 fix.
try {
  installFakeDisplayMedia();  // SYNC — monkey-patch installed before recorder.ts await resolves
} catch (e) {
  console.warn("[offscreen-hooks] eager installFakeDisplayMedia failed:", e);
}
```

**Sub-step 3g — Verify the bridge handler at lines 408-418 is UNCHANGED. The existing `try { installFakeDisplayMedia(); sendResponse({ok: true}); } ... return false;` pattern still works because the function remains sync. The `return false` (sync sendResponse signal) stays — no async dispatcher conversion needed:**
```typescript
// UNCHANGED from current source — the bridge op stays sync because
// installFakeDisplayMedia() stays sync. The async first-frame wait is
// inside fakeGetDisplayMedia, not at install time, so the bridge
// dispatcher doesn't need to await anything.
if (op === 'install-fake-display-media') {
  try {
    installFakeDisplayMedia();  // SYNC; returns immediately
    sendResponse({ ok: true });
  } catch (err) {
    sendResponse({
      ok: false,
      error: err instanceof Error ? err.message : String(err),
    });
  }
  return false;  // sync sendResponse signal — unchanged
}
```

**Step 4 — Add the explicit web_accessible_resources entry (iter-2 BLOCKER 1 fix).**
- Edit `manifest.json`. Modify the `web_accessible_resources` array to append a second entry for the WebM assets. Final array (with the existing welcome entry preserved):
  ```json
  "web_accessible_resources": [
    {
      "resources": ["src/welcome/welcome.html"],
      "matches": ["<all_urls>"]
    },
    {
      "resources": ["assets/*.webm"],
      "matches": ["<all_urls>"]
    }
  ],
  ```
- **Rationale (locked in iter-2; no executor decision):**
  - Production `dist/` has zero `*.webm` assets (verified by `find dist -name '*.webm' | wc -l` returning 0 post-prod-build); the entry is **inert** in production — costs only the diff in the production manifest, costs nothing at runtime.
  - Test `dist-test/` has the hashed asset at `dist-test/assets/<hash>.webm` (verified by `find dist-test -name '*.webm' | wc -l` returning ≥1 post-test-build); the entry **authorizes** `chrome-extension://<id>/assets/<hash>.webm` URL access from the offscreen document context.
  - The `@crxjs/vite-plugin` auto-WAR behavior for extracted media assets in offscreen-document context is empirically untested in this codebase (per checker iter-1 BLOCKER 1 — Plan 01-10 mokosh-mark.svg was 877 bytes and was inlined as data URI; `dist/manifest.json` shows it was NEVER auto-WAR'd because the SVG was never emitted as a file). Pre-emptive explicit entry sidesteps the question entirely.
  - Threat surface: the entry exposes `assets/*.webm` URLs to all origins. Production has zero `*.webm` assets so the exposure surface is null in production. Test bundle is sandboxed in Puppeteer; no user-facing impact.

**Step 5 — Vite config verification (no edits needed; locked in iter-2).**
- `vite.config.ts`: production build — `?url` import is reachable only from `src/test-hooks/offscreen-hooks.ts`, which is gated by `__MOKOSH_UAT__` in `src/offscreen/recorder.ts:46-48` and tree-shaken to dead branch in production builds. NO config changes needed.
- `vite.test.config.ts`: test build — the offscreen entry is already present per Plan 01-13; the `?url` import resolves as a side-effect of the offscreen-hooks.ts module being included via the gated dynamic import. NO config changes needed.
- **assertion (verified by `npm run build:test` in Step 7):** `dist-test/assets/<hash>.webm` exists after test build; `dist/` has zero `*.webm` files after production build.

**Step 6 — Add Tier-2 production-bundle filename leak gate (iter-2 WARNING 5 remediation).**
- Edit `tests/background/no-test-hooks-in-prod-bundle.test.ts`. After the existing Tier-1 FORBIDDEN_HOOK_STRINGS test block, add a new sub-test:
  ```typescript
  // Plan 04-08 iter-2 WARNING 5 — Tier-2 production-bundle filename leak canary.
  //
  // The test-only WebM fixture filename ('synthetic-display-source')
  // appears in the TEST bundle as the resolved Vite hash URL but MUST
  // NOT appear in the PRODUCTION dist/ bundle. The offscreen-hooks
  // module that imports it is tree-shaken in production per
  // __MOKOSH_UAT__; this gate catches any future regression that
  // accidentally inlines test-hooks into the production chunk.
  //
  // The Tier-1 FORBIDDEN_HOOK_STRINGS inventory above tests __mokoshTest-
  // family symbols; this Tier-2 gate tests the orthogonal axis of
  // test-only ASSET filenames. Total inventory:
  //   Tier-1 (symbols): 12 entries (unchanged from Plan 01-14)
  //   Tier-2 (asset filenames): 1 entry (Plan 04-08 — synthetic-display-source)
  test('Tier-2: synthetic-display-source filename does not leak into production dist/', () => {
    // Walk dist/ files (skip the binary asset extensions in IGNORED_EXTENSIONS).
    // Grep for the literal string 'synthetic-display-source'. Expected: 0 hits.
    const distFiles = collectDistFiles();  // existing helper from the Tier-1 test
    const offendingFiles: string[] = [];
    for (const filePath of distFiles) {
      const content = readFileSync(filePath, 'utf-8');
      if (content.includes('synthetic-display-source')) {
        offendingFiles.push(filePath);
      }
    }
    expect(offendingFiles).toEqual([]);
  });
  ```
- **Note**: the executor should READ the existing test file first to identify:
  - The exact name of the helper that walks dist/ files (the snippet above calls it `collectDistFiles` — verify the actual name and adapt).
  - The exact location to insert the new test block (after the Tier-1 inventory test, before the file's final close).
  - The exact import shape (the snippet uses `readFileSync` — verify already imported).

**Step 7 — Verify TypeScript + production build clean + test build emits asset + Tier-2 gate passes.**
- `npx tsc --noEmit` exits 0.
- `npm run build` exits 0 (production build; test-hooks tree-shake verified — `find dist -name '*.webm' | wc -l` returns 0 + `grep -r "synthetic-display-source" dist/ 2>/dev/null | wc -l` returns 0).
- `npm run build:test` exits 0 (test build; ?url import resolves to hashed asset in dist-test/; `find dist-test -name '*.webm' | wc -l` returns ≥1; the chunk that contains the offscreen-hooks module includes a string match for the synthetic-display-source filename or its hashed URL).
- `wc -c tests/uat/fixtures/synthetic-display-source.webm` reports ≥ 1_000_000 bytes.
- `grep -c "canvas.captureStream\|fakeCanvas\|fakeAnimationHandle\|fakeDrawInterval" src/test-hooks/offscreen-hooks.ts | head -1` returns 0 (all canvas symbols excised — filtered to code only via `grep -v '^//'` if needed to skip comment refs):
  - Use `grep -v '^[[:space:]]*\(//\|\*\)' src/test-hooks/offscreen-hooks.ts | grep -c "canvas\.captureStream\|fakeCanvas\b\|fakeAnimationHandle\|fakeDrawInterval"` to filter out comment matches; expected count = 0.
- `grep -v '^[[:space:]]*\(//\|\*\)' src/test-hooks/offscreen-hooks.ts | grep -c "fakeVideoEl\|videoEl\.captureStream\|fakeVideoReadyPromise"` returns ≥ 3 (replacement symbols present in code, not just comments).
- `grep -c "installFakeDisplayMedia(): void" src/test-hooks/offscreen-hooks.ts` returns ≥ 1 (sync signature preserved; iter-2 BLOCKER 2 verification — function does NOT return Promise).
- `grep -c "export function installFakeDisplayMedia(): Promise" src/test-hooks/offscreen-hooks.ts` returns 0 (verifies the function was NOT converted to async).
- `grep -c "await installFakeDisplayMedia" src/test-hooks/offscreen-hooks.ts` returns 0 (verifies the bridge handler + eager-install were NOT converted to await).
- **Sub-verify gate for displaySurface monkey-patch compatibility (WARNING 2 remediation):** create a one-shot inline node script that loads dist-test (via Puppeteer's `enableExtensions`) + executes a snippet in the offscreen document that mints a stream + asserts `stream.getVideoTracks()[0].getSettings().displaySurface === 'monitor'`. If this fails, the production `displaySurface !== 'monitor'` gate at `src/offscreen/recorder.ts:294` would tear down the stream + throw `'wrong-display-surface'` — the spike would fail at Step 2 (assertA2 prime), not at Step 7 (videoSize check). Implementation: append to the existing `tests/uat/spike-a33-sw-persistence.ts` script a `--check-display-surface-only` mode that runs only Steps 1-2 (prime + 5s post-prime probe), invokes `__mokoshOffscreenQuery` op='get-display-surface', asserts result is 'monitor', exits. Run via `HEADLESS=1 SKIP_PROD_REBUILD=1 npx tsx tests/uat/spike-a33-sw-persistence.ts --check-display-surface-only 2>&1 | tee /tmp/04-08-display-surface-check.log` and grep `'DISPLAY-SURFACE-CHECK: PASSED'` in the log. The full spike re-run (Step 1 of Task 2) is a superset of this check, but running it as a fast sub-gate in Task 1 catches the WARNING 2 risk in <10s of wall-clock instead of waiting 6+ min into the spike.
  - Alternative if the executor finds the spike-script-augmentation overhead too high: skip the dedicated sub-gate and rely on the spike re-run in Task 2 Step 1 (the displaySurface failure would manifest as 'wrong-display-surface' Error in the offscreen console capture; the spike's gating condition would still fail). The dedicated sub-gate is the LOW-LATENCY path; the spike re-run is the HIGH-LATENCY path; both gate the same invariant.
- **Sub-verify gate for segments invariant (advisory 2 remediation):** `grep -cE 'let segments: Blob\[\] = \[\];' src/offscreen/recorder.ts` returns 1 (architectural invariant per debug session-2; Plan 04-08 does NOT modify recorder.ts).
  </action>
  <verify>
    <automated>mkdir -p tests/uat/fixtures && test -s tests/uat/fixtures/synthetic-display-source.webm && wc -c tests/uat/fixtures/synthetic-display-source.webm | awk '$1 > 1000000 {exit 0} {exit 1}' && npx tsc --noEmit && npm run build 2>&1 | tail -5 && npm run build:test 2>&1 | tail -5 && find dist -name '*.webm' | wc -l | awk '$1 == 0 {exit 0} {exit 1}' && find dist-test -name '*.webm' | wc -l | awk '$1 >= 1 {exit 0} {exit 1}' && grep -r "synthetic-display-source" dist/ 2>/dev/null | wc -l | awk '$1 == 0 {exit 0} {exit 1}' && grep -v '^[[:space:]]*\(//\|\*\)' src/test-hooks/offscreen-hooks.ts | grep -c "canvas\.captureStream\|fakeCanvas\b\|fakeAnimationHandle\|fakeDrawInterval" | awk '$1 == 0 {exit 0} {exit 1}' && grep -v '^[[:space:]]*\(//\|\*\)' src/test-hooks/offscreen-hooks.ts | grep -c "fakeVideoEl\|videoEl\.captureStream\|fakeVideoReadyPromise" | awk '$1 >= 3 {exit 0} {exit 1}' && grep -c "installFakeDisplayMedia(): void" src/test-hooks/offscreen-hooks.ts | awk '$1 >= 1 {exit 0} {exit 1}' && grep -c "export function installFakeDisplayMedia(): Promise" src/test-hooks/offscreen-hooks.ts | awk '$1 == 0 {exit 0} {exit 1}' && grep -c "await installFakeDisplayMedia" src/test-hooks/offscreen-hooks.ts | awk '$1 == 0 {exit 0} {exit 1}' && grep -cE 'let segments: Blob\[\] = \[\];' src/offscreen/recorder.ts | awk '$1 == 1 {exit 0} {exit 1}' && grep -c '"assets/\*\.webm"' manifest.json | awk '$1 >= 1 {exit 0} {exit 1}' && grep -c "synthetic-display-source" tests/background/no-test-hooks-in-prod-bundle.test.ts | awk '$1 >= 1 {exit 0} {exit 1}' && npm test -- tests/background/no-test-hooks-in-prod-bundle.test.ts 2>&1 | tail -10 | grep -E '(passed|PASS)'</automated>
  </verify>
  <acceptance_criteria>
    - `tests/uat/fixtures/synthetic-display-source.webm` exists, is VP9, >= 1 MB.
    - `tests/fixtures/last_30sec.webm` remains in place (NOT moved).
    - `globals.d.ts` contains the `declare module '*.webm?url'` block.
    - `manifest.json` web_accessible_resources contains an `assets/*.webm` resources entry (iter-2 BLOCKER 1 fix).
    - `src/test-hooks/offscreen-hooks.ts` imports `syntheticDisplaySourceUrl` via Vite `?url` suffix.
    - **`installFakeDisplayMedia()` remains SYNCHRONOUS** (return type `: void`; no `async` keyword; iter-2 BLOCKER 2 verification — function signature preserved).
    - `installFakeDisplayMedia()` body creates videoEl + appendChild + monkey-patch ASSIGNMENT all synchronously; the canplay wait + .play() are deferred INTO the `fakeGetDisplayMedia` closure.
    - `fakeGetDisplayMedia` closure awaits `fakeVideoReadyPromise` on each call (first call may block ~50-500ms; subsequent calls fast-path).
    - `mintStream()` calls `videoEl.captureStream(30)` (NOT `canvas.captureStream`).
    - `uninstallFakeDisplayMedia()` is SYNCHRONOUS (return type `: void`); pauses + removes the video element + nulls `fakeVideoReadyPromise`.
    - All 6 existing bridge ops remain functional + remain in their sync `return false` form (the install-fake-display-media op stays sync — does NOT switch to `return true` because the install itself stays sync).
    - The eager-install try/catch at lines 528-537 is UNCHANGED.
    - `npx tsc --noEmit` exits 0.
    - `npm run build` exits 0; production bundle has zero `*.webm` files; zero references to `synthetic-display-source` in any dist/ file.
    - `npm run build:test` exits 0; test bundle resolves the `?url` import; dist-test/assets/<hash>.webm exists.
    - `grep -c "canvas.captureStream" src/test-hooks/offscreen-hooks.ts` (code only, comments stripped) returns 0.
    - The displaySurface monkey-patch (`patchDisplaySurface(stream)` call) is preserved.
    - The A23 `lastGetDisplayMediaConstraints` capture is preserved.
    - The idempotent install/uninstall contract is preserved.
    - **Architectural invariant preserved:** `src/offscreen/recorder.ts:91 let segments: Blob[] = []` is UNCHANGED (advisory 2 fix; grep gate enforces).
    - **Tier-2 gate (WARNING 5 fix):** `tests/background/no-test-hooks-in-prod-bundle.test.ts` contains a new test that greps dist/ for 'synthetic-display-source' and asserts 0 hits; the test PASSES.
    - **Tier-1 inventory UNCHANGED at 12** (verified by line count of both inventories — Plan 04-08 introduces zero new __mokoshTest-family symbols).
  </acceptance_criteria>
  <done>Methodology fix landed; bundled WebM source replaces canvas.captureStream throttling; eager-install contract preserved; explicit WAR entry locks in chrome-extension:// scheme access. Atomic commit: `feat(04-08): video-file MediaStream + sync-install/lazy-first-frame + explicit WAR — methodology reframe per debug session-2 + iter-2 BLOCKER fixes`.</done>
</task>

<task type="auto">
  <name>Task 2: Re-run spike-a33-sw-persistence.ts + land A33 harness assertion + orchestrator wiring + ROADMAP SC #1 flip</name>
  <files>tests/uat/extension-page-harness.ts, tests/uat/lib/harness-page-driver.ts, tests/uat/harness.test.ts, tests/uat/spike-a33-sw-persistence.ts, .planning/ROADMAP.md, .planning/STATE.md, .planning/phases/04-harden-clean-up-optional/04-08-SUMMARY.md</files>
  <read_first>tests/uat/spike-a33-sw-persistence.ts (full — re-run target), tests/uat/extension-page-harness.ts:3517-3700 (assertA30 — cs-injection-world precedent for reference; A33 does NOT use this pattern but reading clarifies the harness assertion shape), tests/uat/extension-page-harness.ts:3878-3917 (assertA31 — most-recent chrome.runtime.sendMessage SAVE_ARCHIVE pattern; copy this), tests/uat/extension-page-harness.ts:3932-4021 (__mokoshHarness global registration block — verify assertA2 is the canonical "prime fresh recording" entrypoint per Plan 04-04 REVISION iter-2 Option B), tests/uat/lib/harness-page-driver.ts:48-80 (stopServiceWorker helper — REUSED from Plan 04-04 3726eee), tests/uat/lib/harness-page-driver.ts:2039-2148 (driveA30 — host-side filter pattern for shape reference), tests/uat/lib/harness-page-driver.ts:1434-1480 (findLatestZip exported function — REUSED from Plan 04-04), tests/uat/harness.test.ts:100-110 (import block), tests/uat/harness.test.ts:340-360 (wrapped-driver block), tests/uat/harness.test.ts:459-487 (drivers-array push block; A32 is the most-recent entry), tests/uat/harness.test.ts:225-240 (SKIP_PROD_REBUILD env-gate pattern — analog for SKIP_LONG_UAT), .planning/ROADMAP.md:250-262 (SC #1 row text — exact pre-edit string), .planning/phases/04-harden-clean-up-optional/04-08-CHECKER-iter-1.md (WARNING 3 + WARNING 4 — specific grep gates for spike probe values + ROADMAP edit)</read_first>
  <action>
**Step 0 — GATING CONDITION (Task 1 complete + methodology valid).**
- Verify Task 1 acceptance criteria all met. If any fail (TS error, missing fixture, sync signature violated, etc.), STOP and fix before proceeding.
- Verify the displaySurface sub-gate from Task 1 Step 7 PASSED. If skipped, the spike re-run in Step 1 below catches it but with 6+ min latency.

**Step 1 — Re-run the spike script.**
- Run: `HEADLESS=1 SKIP_PROD_REBUILD=0 npx tsx tests/uat/spike-a33-sw-persistence.ts 2>&1 | tee /tmp/04-08-spike-rerun.log`
- Total wall-clock: ~6-7 min (5 min idle + ~1-2 min orchestration).
- **Expected outcome:** `SPIKE OUTCOME: PASSED` with `videoSize > 100_000` (typical 1-3 MB).
- **GATING CONDITION for landing A33:** `grep -c 'SPIKE OUTCOME: PASSED' /tmp/04-08-spike-rerun.log` returns ≥ 1 AND extracted videoSize > 100_000.
- **WARNING 3 remediation (iter-2): probe-value grep gates surfaced as explicit verify-block commands** — the spike script already emits `SPIKE PROBE [POST-PRIME]: segments.length=N`, `SPIKE PROBE [PRE-KILL]: segments.length=N`, `SPIKE PROBE [POST-KILL]: segments.length=N` lines (per debug session-2 Step B addition). The verify block below greps each value to confirm the methodology is healthy:
  - `POST-PRIME=0` — no segment rotation has happened yet (the prime just established REC state).
  - `PRE-KILL >= 3` — 5-min idle drove the rotation cadence to MAX_SEGMENTS (3 × 10s self-contained segments accumulated).
  - `POST-KILL >= 3` — segments structurally survived the SW kill (per debug session-2 verdict: architecture is sound; this should match PRE-KILL).
- If the re-run still FAILS (videoSize ≤ 100_000): STOP execution; document failure in SUMMARY; flag for further debug session. This branch is unlikely per session-2 verdict (canvas throttling is the only identified root cause; HTMLVideoElement source bypasses it definitively per MDN + Chrome bug 653548 design doc) but the spike-first contract requires explicit acknowledgement of the FAIL branch.

**Step 2 — Update the spike script if needed (sync-install/lazy-first-frame compatibility).**
- The spike script's prime step uses `__mokoshHarness.assertA2` (canonical fresh-recording bootstrap; Plan 04-04 REVISION iter-2 Option B). Under the new methodology, `assertA2` triggers `recorder.startRecording` which calls `navigator.mediaDevices.getDisplayMedia` — this is now the patched closure that lazy-waits for video readiness. First call may take an extra ~50-500ms; the existing assertA2 timeout (per Plan 01-13 default ~15s) absorbs this comfortably. NO edit to the spike script's logic is needed.
- **IF** Task 1 Sub-step 3g's sub-gate (`--check-display-surface-only` mode) was implemented, that mode is preserved as a forensic helper. Otherwise the spike script is unchanged.

**Step 3 — Land A33 in the harness (3-file lockstep per Plan 04-04 Wave 1 spec verbatim).**

**File A: `tests/uat/extension-page-harness.ts`** — no edits needed (per Plan 04-04 REVISION iter-2 Option B). The `__mokoshHarness` surface stays at `assertA1..A31 + getManifestVersion`. SAVE_ARCHIVE dispatch happens inline in driveA33 via `page.evaluate` + `chrome.runtime.sendMessage`. The Task 2 read_first MUST verify this; if a different prime-recording method is more appropriate than assertA2, document in SUMMARY but DO NOT add new __mokoshHarness methods (FORBIDDEN_HOOK_STRINGS lockstep at 12 entries).

**File B: `tests/uat/lib/harness-page-driver.ts`** — append `driveA33` per the body in `<interfaces>` above.
- Place AFTER the existing `driveA32` function definition (the most-recent Phase 3 addition).
- Verify the `stopServiceWorker` helper (lines 68-80) is already in scope — it is, per Plan 04-04 commit `3726eee`.
- Verify `findLatestZip` is in scope (exported at line 1434) — it is, per Plan 04-04 commit `3726eee`.
- Verify `JSZip` + `readFileSync` are imported (lines 37 + 41) — they are.
- Type signature: `(page: Page, browser: Browser, extensionId: string, downloadsDir: string) => Promise<AssertionRecord>`.
- Filter-pipeline form; no `continue`; explicit named callbacks per project style.

**File C: `tests/uat/harness.test.ts`** — 3 sites edit:

  (1) Import block at line 107 — add `driveA33,` after `driveA32,`:
  ```typescript
  // Plan 04-08 — driveA33 SW state persistence (ROADMAP SC #1; methodology
  // reframe per debug session-2 verdict; needs Browser + extensionId for
  // CDP-based SW kill + downloadsDir for host-side JSZip parse).
  driveA33,
  ```

  (2) Wrapped-driver block after line 357 (after `driveA31Wrapped`):
  ```typescript
  // Plan 04-08 — driveA33 needs Browser + extensionId for CDP-based SW kill
  //             AND downloadsDir for host-side JSZip parse of post-restart zip.
  const driveA33Wrapped: (page: import('puppeteer').Page) => Promise<AssertionRecord> =
    (page) => driveA33(page, handles.browser, handles.extensionId, handles.downloadsDir);
  ```

  (3) Drivers-array push at line 487 (after the existing A32 entry):
  ```typescript
  // Plan 04-08 A33: SW state persistence 5-min idle (ROADMAP SC #1).
  // Methodology reframe per debug session-2 — video-file MediaStream
  // replaces the canvas.captureStream invisible-source throttling that
  // produced 8505-byte 0-frames archives under the previous Plan 04-04
  // spike methodology. Architecture (offscreen-RAM segments: Blob[]) is
  // unchanged and canonically correct per debug session-2 segment-count
  // probe evidence (POST-KILL count=3 confirms structural persistence).
  // Forces SW eviction via Puppeteer CDP worker.close() per the canonical
  // Chrome devrel pattern (stopServiceWorker helper from Plan 04-04).
  // Env-gated by SKIP_LONG_UAT for fast per-commit iteration; defaults
  // to RUN for Phase 4 closure + alpha gate.
  {
    name: 'A33',
    drive: process.env.SKIP_LONG_UAT === '1'
      ? async (): Promise<AssertionRecord> => ({
          name: 'A33',
          passed: true,
          checks: [],
          diagnostics: ['A33 SKIPPED (SKIP_LONG_UAT=1; unset to run 5-min idle test)'],
        })
      : driveA33Wrapped,
  },
  ```

**Step 4 — Run the UAT harness verification gates.**
- `npx tsc --noEmit` exits 0.
- `npm run build:test` exits 0.
- **Skip-mode UAT (fast preserve):** `HEADLESS=1 SKIP_PROD_REBUILD=1 SKIP_LONG_UAT=1 npm run test:uat 2>&1 | tail -5 | tee /tmp/04-08-uat-skip.log` — expect `34/34` GREEN in ~95s; A33 SKIPPED placeholder counts as PASS.
- **Full-mode UAT (closure gate):** `HEADLESS=1 SKIP_PROD_REBUILD=1 npm run test:uat 2>&1 | tail -5 | tee /tmp/04-08-uat-full.log` — expect `34/34` GREEN in ~6.5 min; A33 actually runs and passes A33.1 + A33.2 + A33.3.

**Step 5 — Lockstep + bundle-gate invariant verification.**
- Tier-1 FORBIDDEN_HOOK_STRINGS inventory unchanged at 12 — verify by counting code-only entries (comment-stripped) in both arrays:
  ```bash
  # tests/uat/harness.test.ts FORBIDDEN_HOOK_STRINGS array entries (12 expected)
  # tests/background/no-test-hooks-in-prod-bundle.test.ts the same array (12 expected, lockstep)
  ```
  Confirm zero new entries added (no new __MOKOSH_UAT__-gated symbols).
- Tier-2 sub-invariant (Plan 04-08 iter-2): `npm test -- tests/background/no-test-hooks-in-prod-bundle.test.ts 2>&1 | grep -E '(passed|PASS)'` — both the Tier-1 inventory test AND the new Tier-2 filename-leak test pass.
- Pre-checkpoint bundle gates (per `feedback-pre-checkpoint-bundle-gates.md`) — 6/6 PASS unchanged from Plan 04-03 baseline:
  - `grep -v '^#\|^//' dist/assets/index-*.js | grep -c 'new Function'` returns 0 (Plan 04-02 polarity preserved)
  - `grep -v '^#\|^//' dist/assets/index-*.js | grep -c '\beval\b'` returns 0
  - `grep -v '^#\|^//' dist/assets/index-*.js | grep -c 'Buffer\.'` returns 1 (pre-existing JSZip polyfill; Plan 04-02 deferred)
  - SW chunk `window.`/`document.` references = 0
  - Manifest validation + en/ru parity preserved (unchanged from Plan 04-03)
- vitest baseline preserved: `npm test 2>&1 | tail -5` — expect 184/184 GREEN (was 183 baseline + 1 new Tier-2 test from Plan 04-08), or 181/184 with the 3 documented pre-existing parallel-vitest flakes per 04-CONTEXT items 9-10; flakes pass in isolation.

**Step 6 — Write Plan 04-08 SUMMARY.**
- Create `.planning/phases/04-harden-clean-up-optional/04-08-SUMMARY.md`:
  - Methodology reframe rationale (cite debug session-2 verdict verbatim)
  - **iter-2 revision summary** (cite checker iter-1 + BLOCKER 1 + BLOCKER 2 + WARNING resolutions)
  - Bundled WebM fixture decision (copy vs regenerate; size + codec evidence; dual-location note)
  - installFakeDisplayMedia diff summary (canvas -> HTMLVideoElement; SYNC install + LAZY first-frame; 6 bridge ops preserved sync; A23 capture preserved; eager-install contract preserved)
  - manifest.json WAR entry decision (BLOCKER 1 rationale: pre-emptive explicit entry; production inert; test bundle authorized)
  - displaySurface compatibility evidence (sub-gate result; WARNING 2 closure)
  - Spike re-run evidence (videoSize before/after; segment-count probe values; elapsed time)
  - A33 land evidence (driveA33 + orchestrator wiring; FORBIDDEN_HOOK_STRINGS at 12; pre-checkpoint gates 6/6; Tier-2 gate added)
  - UAT before/after (33/33 -> 34/34 GREEN)
  - ROADMAP SC #1 closure with commit ref
  - Plan 04-04 SUMMARY post-debug amendment cross-reference
  - Persisting artifacts (stopServiceWorker + spike script + canonical methodology pattern + Tier-2 invariant)
  - Architectural integrity statement (offscreen-RAM segments: Blob[] is UNCHANGED and canonically correct; grep gate enforces)

**Step 7 — Update STATE.md + ROADMAP.md markers (Phase 4 partial closure) — WARNING 4 remediation: exact edit specified + grep gate.**

**STATE.md edit:**
- Append to "Decisions" section: `[Phase 04-08]: Methodology reframe complete — video-file MediaStream replaces canvas.captureStream throttling per debug session-2 verdict; A33 harness assertion landed; UAT 33 -> 34 GREEN; ROADMAP SC #1 (SW state persistence) CLOSED 2026-05-22.`

**ROADMAP.md edit (exact pre-edit string + replacement; WARNING 4 fix):**
- Open `.planning/ROADMAP.md`. Locate the SC #1 prose at lines 250-262 (the existing OPEN status block).
- The current text (verified during planning) contains:
  ```
       **STATUS 2026-05-21: OPEN.** Plan 04-04 Wave 0 SPIKE empirically refuted
       the prior hypothesis that the current offscreen-document RAM-only
       `segments: Blob[]` architecture would survive idle: measured 8505 bytes
       vs 100 KB floor after 5 min idle + Puppeteer CDP `worker.close()`. The
       architecture requires a persistence layer (canonical recommendation
       per 04-RESEARCH.md Q2 sub-question b Option C: IndexedDB persistence
       in offscreen). Plan-fix ceremony queued ahead of Plans 04-05/04-06/
       04-07. Reproducible verification gate: tests/uat/spike-a33-sw-persistence.ts.
  ```
- Replace the entire block (from `**STATUS 2026-05-21: OPEN.**` through the line ending with `spike-a33-sw-persistence.ts.`) with:
  ```
       **STATUS 2026-05-22: CLOSED via Plan 04-08 — see .planning/phases/04-harden-clean-up-optional/04-08-SUMMARY.md.**
       The prior Plan 04-04 SPIKE FAILED outcome (8505 bytes; 2026-05-21) was
       empirically REFUTED by debug session-2 (commit `4ea1bbb`): the
       offscreen-RAM `segments: Blob[]` architecture is sound (POST-KILL probe
       count=3 confirms structural persistence); the failure was test
       methodology (canvas.captureStream invisible-source throttling per
       Chrome bug 653548). Plan 04-08 replaced the canvas source with
       HTMLVideoElement.captureStream backed by a bundled WebM (preserving
       eager-install contract via SYNC-install + LAZY first-frame pattern);
       spike re-run produces videoSize > 100_000 (typical 1-3 MB); A33
       harness assertion lands per Plan 04-04 Pattern 4 verbatim under
       SKIP_LONG_UAT env-gate. Reproducible verification gate:
       tests/uat/spike-a33-sw-persistence.ts (now PASSES under valid
       methodology).
  ```
- Update the Plans list block at line ~277 — find `04-04-PLAN.md` entry and append a sibling line after it for Plan 04-08:
  ```
  - [x] 04-08-PLAN.md — A33 methodology reframe + harness assertion: **CLOSED 2026-05-22** via debug session-2 verdict (canvas-captureStream invisible-source throttling root cause); HTMLVideoElement.captureStream replaces canvas.captureStream in installFakeDisplayMedia() with SYNC install + LAZY first-frame contract; spike re-run produces videoSize > 100_000 (vs 8505 baseline); A33 lands per original Plan 04-04 Wave 1 spec under SKIP_LONG_UAT env-gate; UAT 33 -> 34 GREEN. ROADMAP SC #1 CLOSED.
  ```
- Update the phase tracker table at line ~292: find the row for Phase 4 and update completion count + status note:
  ```
  | 4. Harden + clean up (optional) | 5/8 | In Progress (Plan 04-08 closed ROADMAP SC #1 via methodology reframe; Plans 04-05/04-06/04-07 remain for build hygiene + visual polish + closure aggregator) |  |
  ```
- **WARNING 4 grep gate (post-edit verify):**
  ```bash
  grep -c 'CLOSED via Plan 04-08' .planning/ROADMAP.md   # MUST return >= 1
  grep -c 'STATUS 2026-05-21: OPEN' .planning/ROADMAP.md  # MUST return 0 (the old status removed)
  grep -c 'STATUS 2026-05-22: CLOSED' .planning/ROADMAP.md  # MUST return >= 1
  ```

**Step 8 — Atomic commit (advisory 1 — corrected commit message; Task 1 + Task 2 only, no Task 3).**
- Single atomic commit for Task 2 with all Task 2 artifacts + SUMMARY + STATE/ROADMAP markers: `feat(04-08): A33 SW state persistence harness assertion — methodology reframe (34/34 GREEN; ROADMAP SC #1 CLOSED)`.
- Task 1 was committed separately at the close of Task 1 per its own done line: `feat(04-08): video-file MediaStream + sync-install/lazy-first-frame + explicit WAR — methodology reframe per debug session-2 + iter-2 BLOCKER fixes`.
  </action>
  <verify>
    <automated>npx tsc --noEmit && npm run build:test && HEADLESS=1 SKIP_PROD_REBUILD=1 SKIP_LONG_UAT=1 npm run test:uat 2>&1 | tail -5 | tee /tmp/04-08-uat-skip.log; grep -c '34/34\|34 passed' /tmp/04-08-uat-skip.log | awk '$1 >= 1 {exit 0} {exit 1}' && grep -c 'driveA33' tests/uat/harness.test.ts | awk '$1 >= 3 {exit 0} {exit 1}' && grep -c 'SKIP_LONG_UAT' tests/uat/harness.test.ts | awk '$1 >= 2 {exit 0} {exit 1}' && grep -c 'dispatchSaveArchive' tests/uat/lib/harness-page-driver.ts tests/uat/extension-page-harness.ts tests/uat/harness.test.ts 2>/dev/null | grep -v ":0$" | wc -l | awk '$1 == 0 {exit 0} {exit 1}' && grep -cE 'SPIKE PROBE \[POST-PRIME\]: segments\.length=0' /tmp/04-08-spike-rerun.log 2>/dev/null | awk '$1 >= 1 {exit 0} {exit 1}' && grep -cE 'SPIKE PROBE \[PRE-KILL\]: segments\.length=([3-9]|[1-9][0-9]+)' /tmp/04-08-spike-rerun.log 2>/dev/null | awk '$1 >= 1 {exit 0} {exit 1}' && grep -cE 'SPIKE PROBE \[POST-KILL\]: segments\.length=([3-9]|[1-9][0-9]+)' /tmp/04-08-spike-rerun.log 2>/dev/null | awk '$1 >= 1 {exit 0} {exit 1}' && grep -c 'SPIKE OUTCOME: PASSED' /tmp/04-08-spike-rerun.log 2>/dev/null | awk '$1 >= 1 {exit 0} {exit 1}' && grep -c 'CLOSED via Plan 04-08' .planning/ROADMAP.md | awk '$1 >= 1 {exit 0} {exit 1}' && grep -c 'STATUS 2026-05-21: OPEN' .planning/ROADMAP.md | awk '$1 == 0 {exit 0} {exit 1}'</automated>
  </verify>
  <acceptance_criteria>
    - Spike re-run output contains `SPIKE OUTCOME: PASSED` AND `videoSize > 100_000`. (If FAILED branch fires, STOP and document; A33 land is BLOCKED.)
    - **WARNING 3 (iter-2):** Spike log contains `SPIKE PROBE [POST-PRIME]: segments.length=0` (post-prime baseline; no rotations yet).
    - **WARNING 3 (iter-2):** Spike log contains `SPIKE PROBE [PRE-KILL]: segments.length=X` where X ≥ 3 (5-min idle drove rotation cadence to MAX_SEGMENTS).
    - **WARNING 3 (iter-2):** Spike log contains `SPIKE PROBE [POST-KILL]: segments.length=X` where X ≥ 3 (architecture preserved across SW kill per debug session-2).
    - `npx tsc --noEmit` exits 0.
    - `npm run build:test` exits 0.
    - `tests/uat/lib/harness-page-driver.ts` contains `driveA33` function with the 4-arg signature `(page, browser, extensionId, downloadsDir) => Promise<AssertionRecord>`.
    - `tests/uat/lib/harness-page-driver.ts` driveA33 dispatches SAVE_ARCHIVE inline via `chrome.runtime.sendMessage({type: 'SAVE_ARCHIVE'}, ...)` — verify `grep -c "type: 'SAVE_ARCHIVE'" tests/uat/lib/harness-page-driver.ts` returns ≥ 1.
    - `tests/uat/harness.test.ts` imports `driveA33` (1 line; grep -c returns ≥ 4 including comment).
    - `tests/uat/harness.test.ts` defines `driveA33Wrapped` const.
    - `tests/uat/harness.test.ts` drivers-array contains an `{ name: 'A33', drive: ... }` entry with `SKIP_LONG_UAT` env-gate.
    - Skip-mode UAT: `HEADLESS=1 SKIP_PROD_REBUILD=1 SKIP_LONG_UAT=1 npm run test:uat` reports 34/34 GREEN in ~95s.
    - Full-mode UAT: `HEADLESS=1 SKIP_PROD_REBUILD=1 npm run test:uat` reports 34/34 GREEN in ~6.5 min; A33.1 + A33.2 + A33.3 all PASS.
    - `dispatchSaveArchive` symbol is NOT introduced anywhere — `grep -c 'dispatchSaveArchive' tests/uat/` returns 0.
    - FORBIDDEN_HOOK_STRINGS inventory unchanged at 12 entries — verify by line count of both arrays.
    - **Tier-2 gate (Plan 04-08 iter-2):** `grep -c 'synthetic-display-source' tests/background/no-test-hooks-in-prod-bundle.test.ts` returns ≥ 1; the test PASSES under `npm test -- tests/background/no-test-hooks-in-prod-bundle.test.ts`.
    - Pre-checkpoint bundle gates 6/6 PASS unchanged from Plan 04-03 baseline.
    - vitest 184 baseline preserved (183 prior + 1 new Tier-2 test) — or 181/184 with the 3 documented pre-existing flakes; pass in isolation.
    - **WARNING 4 (iter-2):** `.planning/ROADMAP.md` contains `'CLOSED via Plan 04-08'` (grep returns ≥ 1); contains zero hits on `'STATUS 2026-05-21: OPEN'` (the old status was removed); contains `'STATUS 2026-05-22: CLOSED'`.
    - `.planning/STATE.md` Decisions list contains a Plan 04-08 entry citing ROADMAP SC #1 CLOSED.
    - `.planning/phases/04-harden-clean-up-optional/04-08-SUMMARY.md` exists with: methodology rationale + iter-2 revision summary + spike re-run evidence + probe values + A33 land evidence + UAT before/after + ROADMAP SC #1 closure + cross-reference to Plan 04-04 post-debug amendment.
  </acceptance_criteria>
  <done>A33 lands; UAT 33->34 GREEN; ROADMAP SC #1 CLOSED. Atomic commit: `feat(04-08): A33 SW state persistence harness assertion — methodology reframe (34/34 GREEN; ROADMAP SC #1 CLOSED)`.</done>
</task>

</tasks>

<threat_model>
## Trust Boundaries

| Boundary | Description |
|----------|-------------|
| Bundled WebM fixture -> offscreen test bundle | the `tests/uat/fixtures/synthetic-display-source.webm` is project-owned (CC0-equivalent internal capture) and loaded via Vite's `?url` asset pipeline only in test builds. Production builds tree-shake the entire offscreen-hooks module per `__MOKOSH_UAT__`; the fixture has zero attack surface in production (manifest.json WAR entry for assets/*.webm is inert because production dist/ has zero *.webm files). |
| HTMLVideoElement.captureStream -> MediaRecorder | the video element source is bundled at build time (not network-fetched); no remote-origin attack vector. The captured stream feeds the production MediaRecorder code path verbatim — same boundary as canvas.captureStream had. |
| Puppeteer CDP -> Chrome MV3 SW | unchanged from Plan 04-04 (stopServiceWorker helper reused verbatim). |
| manifest.json web_accessible_resources -> chrome-extension:// URL access | new explicit entry for `assets/*.webm` extends the existing `src/welcome/welcome.html` WAR pattern. Matches `<all_urls>`; in production this is null-surface (no *.webm files); in test this authorizes the bundled fixture. |

## STRIDE Threat Register

| Threat ID | Category | Component | Disposition | Mitigation Plan |
|-----------|----------|-----------|-------------|-----------------|
| T-04-08-01 | Tampering | future change to `installFakeDisplayMedia()` reintroduces canvas.captureStream silently | mitigate | `grep -c "canvas.captureStream" src/test-hooks/offscreen-hooks.ts` (code-only, comment-filtered) invariant = 0 codified in Task 1 verify. A33 acts as a regression-catching gate; if a future PR moves source back to canvas, the spike fails fast (videoSize=8505). |
| T-04-08-02 | Tampering | bundled `synthetic-display-source.webm` is renamed/deleted/replaced with a tiny or invalid WebM | mitigate | Task 1 verify checks `wc -c` >= 1_000_000 bytes; Task 2 spike re-run catches any content-level corruption (videoSize-floor gate). |
| T-04-08-03 | Information disclosure | the bundled WebM contains operator content (it's a project-internal capture of the developer's screen) | accept | The existing `tests/fixtures/last_30sec.webm` has been in the repo since 2026-05-15 (Plan 01-07 closure); the new copy at `tests/uat/fixtures/synthetic-display-source.webm` is the same project-owned artifact. Tradeoff: rebuilding a fresh WebM from `ffmpeg -f lavfi -i testsrc` is OPTIONAL per Task 1 Step 1. If the developer prefers content-free fixtures, the regeneration path is the documented escape hatch. |
| T-04-08-04 | DoS (test runtime) | A33's 5-min idle adds ~5 min to harness wall-clock (95s -> 395s); per-commit CI lanes would suffer | mitigate | Env-gated by `SKIP_LONG_UAT=1` (default RUN for closure + alpha; documented per-commit fast-skip path). Same gate Plan 04-04 specified. |
| T-04-08-05 | Repudiation | HTMLVideoElement.captureStream is non-standard (not in lib.dom.d.ts at all TS versions); a TS strict-mode bump could break the cast-through-intersection idiom | accept | The cast is pinned in the code at Task 1 Step 3; project's TS pin is documented; if a TS upgrade ever breaks the cast, the build-test gate (Task 1 verify) catches it. The runtime surface itself (HTMLMediaElement.captureStream) is implemented in Chrome since 2017 and stable per MDN. |
| T-04-08-06 | Spoofing | a malicious replacement `synthetic-display-source.webm` could inject malicious VP9 codec data | accept | the fixture is committed to git; any tamper is visible via `git diff`. Plan 04-08's threat surface is test-only and the test build runs in a sandboxed Puppeteer browser instance. No production user is exposed. |
| T-04-08-07 | Elevation of Privilege | manifest.json's new web_accessible_resources entry for `assets/*.webm` could expose unintended content if a future plan accidentally bundles a sensitive WebM into production dist/ | mitigate | Production dist/ has zero *.webm assets (verified by Task 1 Step 7 grep gate: `find dist -name '*.webm' | wc -l == 0`); Tier-2 filename-leak gate at tests/background/no-test-hooks-in-prod-bundle.test.ts catches any regression. The threat is constructed (no current attack surface) but the gate makes it self-extinguishing. |
| T-04-08-08 | Tampering | future refactor converts `installFakeDisplayMedia()` to async (breaking the eager-install contract — recurrence of iter-2 BLOCKER 2) | mitigate | Grep gate codified in Task 1 verify: `grep -c "export function installFakeDisplayMedia(): Promise" src/test-hooks/offscreen-hooks.ts == 0` AND `grep -c "installFakeDisplayMedia(): void" >= 1`. Any future PR that flips the signature trips the build-test pipeline. Threat is high-impact (silent re-introduction of the 8505-byte race) but the gate is deterministic. |
| T-04-08-09 | Tampering | future refactor removes the explicit `assets/*.webm` WAR entry (breaking the chrome-extension:// access path for the bundled fixture) | mitigate | Task 1 verify gate: `grep -c '"assets/\*\.webm"' manifest.json >= 1`. The fixture would still load via Vite hash URL in test build but the chrome-extension:// scheme access would fail; the spike re-run would catch the regression. |
</threat_model>

<verification>
- `npx tsc --noEmit` exits 0.
- `npm run build` exits 0 (production; test-hooks tree-shake verified).
- `npm run build:test` exits 0 (test; ?url import resolves; dist-test/assets/<hash>.webm emitted).
- `wc -c tests/uat/fixtures/synthetic-display-source.webm` reports >= 1_000_000 bytes; codec=vp9 per ffprobe.
- `find dist -name '*.webm' | wc -l` returns 0 (production has zero WebM assets — WAR entry is inert there).
- `find dist-test -name '*.webm' | wc -l` returns ≥ 1 (test bundle emits the asset).
- **Code-only grep gates (filtering comments via `grep -v '^[[:space:]]*\(//\|\*\)'`):**
  - `canvas.captureStream` references: 0
  - `fakeVideoEl|videoEl.captureStream|fakeVideoReadyPromise` references: ≥ 3
- `grep -c "installFakeDisplayMedia(): void" src/test-hooks/offscreen-hooks.ts` returns ≥ 1 (sync signature preserved).
- `grep -c "export function installFakeDisplayMedia(): Promise" src/test-hooks/offscreen-hooks.ts` returns 0 (NOT async; iter-2 BLOCKER 2 fix verified).
- `grep -c "await installFakeDisplayMedia" src/test-hooks/offscreen-hooks.ts` returns 0 (eager-install + bridge handler preserve sync calls).
- `grep -c '"assets/\*\.webm"' manifest.json` returns ≥ 1 (iter-2 BLOCKER 1 fix verified).
- `grep -c "synthetic-display-source" tests/background/no-test-hooks-in-prod-bundle.test.ts` returns ≥ 1 (Tier-2 gate present; WARNING 5).
- `grep -r "synthetic-display-source" dist/ 2>/dev/null | wc -l` returns 0 (production tree-shake).
- `grep -cE 'let segments: Blob\[\] = \[\];' src/offscreen/recorder.ts` returns 1 (advisory 2; architecture invariant).
- Spike re-run: `HEADLESS=1 npx tsx tests/uat/spike-a33-sw-persistence.ts` exits 0 with `videoSize > 100_000` (typical 1-3 MB).
- **WARNING 3 (iter-2):** spike log contains:
  - `SPIKE PROBE [POST-PRIME]: segments.length=0`
  - `SPIKE PROBE [PRE-KILL]: segments.length=X` where X ≥ 3
  - `SPIKE PROBE [POST-KILL]: segments.length=X` where X ≥ 3
  - `SPIKE OUTCOME: PASSED`
- UAT harness count 33 -> 34.
- Skip-mode UAT: `HEADLESS=1 SKIP_PROD_REBUILD=1 SKIP_LONG_UAT=1 npm run test:uat` GREEN 34/34 in ~95s.
- Full-mode UAT: `HEADLESS=1 SKIP_PROD_REBUILD=1 npm run test:uat` GREEN 34/34 in ~6.5 min.
- **WARNING 4 (iter-2):** ROADMAP edits:
  - `grep -c 'CLOSED via Plan 04-08' .planning/ROADMAP.md` returns ≥ 1
  - `grep -c 'STATUS 2026-05-21: OPEN' .planning/ROADMAP.md` returns 0 (old status removed)
  - `grep -c 'STATUS 2026-05-22: CLOSED' .planning/ROADMAP.md` returns ≥ 1
- Tier-1 FORBIDDEN_HOOK_STRINGS lockstep at 12 entries (unchanged).
- Tier-2 gate (Plan 04-08): `npm test -- tests/background/no-test-hooks-in-prod-bundle.test.ts` passes.
- Pre-checkpoint bundle gates 6/6 PASS (new Function=0 + eval=0 + Buffer.=1 + window.=0 + document.=0 in SW + Tier-1=12 + en/ru parity).
- vitest baseline 184 preserved (183 prior + 1 new Tier-2; or 181/184 with 3 documented pre-existing flakes; pass in isolation).
- A29 + A30 + A31 + A32 unchanged (no regression to existing assertions).
- Architecture invariant preserved: `src/offscreen/recorder.ts:91 let segments: Blob[] = []` UNCHANGED — debug session-2 verdict is honored (NO IndexedDB persistence work).
- spike-FAILED forensic-evidence preservation: `tests/uat/spike-a33-sw-persistence.ts` retained (Plan 04-04 commit 3726eee + debug session-2 Step B + C additions); now functions as a PASSING regression test under the new methodology.
- `dispatchSaveArchive` symbol NOT introduced anywhere — `grep -c` across spike script + harness files returns 0.
- **iter-2 BLOCKER 1 verify:** WAR entry pre-decided AND the @crxjs/vite-plugin auto-WAR question is sidestepped (no executor improvisation needed).
- **iter-2 BLOCKER 2 verify:** eager-install contract preserved — sync monkey-patch in `installFakeDisplayMedia()`; lazy first-frame inside `fakeGetDisplayMedia` closure; recorder.ts:46-48 await chain race window eliminated.
</verification>

<success_criteria>
- Bundled WebM fixture lands at `tests/uat/fixtures/synthetic-display-source.webm` (>=1 MB VP9; project-owned).
- `installFakeDisplayMedia()` rewritten — canvas.captureStream replaced by HTMLVideoElement.captureStream; **function signature remains SYNCHRONOUS** (iter-2 BLOCKER 2); displaySurface monkey-patch + A23 capture + idempotency contract preserved.
- `fakeGetDisplayMedia` closure performs the lazy first-frame wait — first call awaits `fakeVideoReadyPromise`; subsequent calls observe resolved Promise + proceed immediately.
- Ambient module decl for `*.webm?url` added to `globals.d.ts`.
- Explicit web_accessible_resources entry for `assets/*.webm` added to `manifest.json` (iter-2 BLOCKER 1).
- Spike re-run produces `videoSize > 100_000` (typical 1-3 MB) — methodology reframe empirically validated.
- Spike probe values confirm methodology health: POST-PRIME=0, PRE-KILL≥3, POST-KILL≥3 (WARNING 3).
- A33 harness assertion lands per Plan 04-04 Pattern 4 verbatim: driveA33 + driveA33Wrapped + orchestrator entry + SKIP_LONG_UAT env-gate.
- UAT harness count 33 -> 34 GREEN (skip-mode in ~95s; full-mode in ~6.5 min).
- ROADMAP SC #1 (SW state persistence) flipped CLOSED in ROADMAP.md with exact pre-edit/post-edit grep gates verified (WARNING 4).
- Plan 04-04 SUMMARY post-debug amendment cross-referenced in Plan 04-08 SUMMARY.
- Tier-1 FORBIDDEN_HOOK_STRINGS inventory unchanged at 12 entries.
- Tier-2 production-bundle filename-leak gate added: `synthetic-display-source` returns 0 hits in dist/ (WARNING 5).
- Pre-checkpoint bundle gates 6/6 PASS.
- Architectural integrity preserved (no IndexedDB persistence; no chrome.storage migration; src/offscreen/recorder.ts:91 segments array unchanged; grep gate enforces).
- vitest 184 baseline preserved (183 prior + 1 new Tier-2 test).
- Plan 04-04 forensic artifacts (`stopServiceWorker` helper + spike script) repurposed as PASSING regression tests under valid methodology.
- iter-2 BLOCKER 1 + BLOCKER 2 + WARNINGs 1-5 + advisories 1-3 all addressed per checker iter-1 remediation guidance.
</success_criteria>

<output>
After completion, create `.planning/phases/04-harden-clean-up-optional/04-08-SUMMARY.md` capturing:

- **Methodology reframe rationale** — verbatim cite of debug session-2 verdict (REFUTED-architecture; canvas-captureStream issue); explicit rejection of the previously-proposed IndexedDB persistence plan-fix with the empirical reasoning (the spike would STILL produce 8505 bytes after IDB lands because the failure is in the fake stream, not in segment persistence).
- **iter-2 revision summary** — cite checker iter-1 BLOCKER 1 (Vite asset-emission path) + BLOCKER 2 (eager-install contract) resolutions; explain SYNC install + LAZY first-frame contract; document the explicit WAR entry decision (production inert / test authorized); enumerate WARNING resolutions (autoplay fallback; displaySurface compat sub-gate; spike probe-value grep gates; ROADMAP edit pre-spec; Tier-2 filename-leak gate).
- **Bundled WebM fixture decision** — copy from `tests/fixtures/last_30sec.webm` vs regenerate via ffmpeg; size + codec + duration evidence; license/provenance attestation (CC0-equivalent project-owned internal capture); dual-location note (original fixture remains in place at tests/fixtures/).
- **installFakeDisplayMedia diff summary** — before (canvas.captureStream + RAF + setInterval; sync but throttled) vs after (HTMLVideoElement + sync install + lazy first-frame closure; sync signature + async first-call wait); preserved invariants (displaySurface monkey-patch, A23 capture, idempotency, 6 bridge ops all sync); explicit verification that the function did NOT become async.
- **manifest.json WAR entry decision** — iter-2 BLOCKER 1 rationale; production inert + test authorized; alternative options considered (Option A probe-then-decide; Option C blob URL from ?raw); chosen path = explicit pre-emptive entry.
- **displaySurface compatibility evidence** — WARNING 2 sub-gate result OR spike re-run high-latency catch evidence.
- **Spike re-run evidence** — videoSize before (8505) vs after (>100_000; typical 1-3 MB); segment-count probe values (POST-PRIME=0, PRE-KILL≥3, POST-KILL≥3); elapsed time (~308s baseline preserved); SPIKE OUTCOME: PASSED.
- **A33 land evidence** — driveA33 (4-arg signature); 3-file lockstep diff (extension-page-harness.ts unchanged per Option B; harness-page-driver.ts +driveA33; harness.test.ts +import +wrapped +array push); FORBIDDEN_HOOK_STRINGS at 12 entries (unchanged); Tier-2 gate added; pre-checkpoint gates 6/6 PASS.
- **UAT before/after** — 33/33 -> 34/34 GREEN; skip-mode wall-clock ~95s; full-mode wall-clock ~6.5 min.
- **ROADMAP SC #1 closure** — flipped OPEN -> CLOSED with Plan 04-08 cite + 2026-05-22 date; exact ROADMAP.md edit pre/post snapshots; grep gate verifications.
- **Plan 04-04 cross-reference** — debug session-2 verdict honored; spike-FAILED forensic artifacts (`stopServiceWorker` helper + `spike-a33-sw-persistence.ts`) repurposed as PASSING regression tests.
- **Architectural integrity statement** — `let segments: Blob[] = []` at src/offscreen/recorder.ts:91 is UNCHANGED and canonically correct per debug session-2 segment-count probe evidence; grep gate enforces.
- **Commit refs** — Task 1 atomic commit (methodology fix + WAR entry + Tier-2 gate) + Task 2 atomic commit (A33 land + SUMMARY + STATE/ROADMAP markers).
- **Next plan handoff** — Plan 04-07 (closure aggregator) can now reference ROADMAP SC #1 as GREEN; v1 milestone close prep unblocked from the SW persistence side.
</output>