---
phase: 01-stabilize-video-pipeline
plan: 07
subsystem: video
tags: [webm, vp9, mediarecorder, getdisplaymedia, offscreen, ffprobe, ffmpeg, mv3, chrome-extension, ring-buffer, restart-segments]

# Dependency graph
requires:
  - phase: 01-stabilize-video-pipeline
    provides: Plans 01..06 — doc cascade (D-A1..D-A6), Wave-0 test infra (vitest + 4 RED tests), offscreen recorder TDD (D-09..D-11 originally, D-13 after fix-a3), port keepalive + OFFSCREEN_READY handshake, SW shrink (alarms/IDB/tabCapture deletion + port host), build pipeline collapse (vite.config.ts inline plugin deletion)
provides:
  - D-12 ffprobe acceptance gate (structural validation of `tests/fixtures/last_30sec.webm`) — exit 0, zero stderr
  - A3 empirical-playback acceptance gate (operator-confirmed Chrome playback + ffmpeg decoder dry-run exit 0, zero packet errors)
  - `tests/fixtures/last_30sec.webm` regression fixture (1.6 MB VP9 1142×1038 captured against the D-13 restart-segments recorder)
  - REQ-video-ring-buffer marked Complete; SPEC §10 acceptance criteria #2, #3, #7 functionally green at Phase 1 level
  - D-09..D-11 RETIRED in favor of D-13 restart-segments (mid-phase architectural correction, both pre-staged fallbacks activated)
  - CON-webm-header-retention RETIRED (D-13's per-segment header isolation makes it meaningless)
affects:
  - Phase 2 (DOM + event-capture privacy) — capture pipeline is now always-on regardless of active tab; Phase 2 content scripts MUST NOT add competing keepalives (port `'video-keepalive'` keeps SW alive)
  - Phase 3 (export pipeline + popup state machine) — popup will consume `getSegments()` output via the existing SW port host
  - Phase 4 (SPEC §10 smoke verification) — Phase 4 verifies the full 9-criterion sweep; Phase 1 only proved #2/#3/#7
  - Phase 5 (P1/P2 hardening) — new entry: `getDisplayMedia` cursor visibility constraint (`video: { cursor: 'always' }`)
  - GSD framework retro candidate — auto-injection of empirical-acceptance gates when RESEARCH.md flags HIGH-risk assumptions

# Tech tracking
tech-stack:
  added: [ffprobe + ffmpeg (system CLIs used for the D-12 / A3 gates)]
  patterns:
    - "Pre-staged contingency activation: when RESEARCH.md flags an assumption as HIGH-risk, plan-time pre-stages a fallback skeleton (D-13 commented block in recorder.ts; base64 wire-format research in CONTEXT.md Doc Cascade). The smoke step then acts as an A/B gate: if simple-approach fails empirically, the executor activates the pre-staged fallback in-cycle rather than scheduling a new plan."
    - "Three-attempt acceptance pattern: attempt 1 (single-continuous recorder) failed at binary-transfer layer → D-12 fix; attempt 2 (after D-12) passed ffprobe but failed Chrome playback → A3 fix via D-13 activation; attempt 3 clean. Each failure was contained by its pre-staged fallback."

key-files:
  created:
    - "tests/fixtures/last_30sec.webm — 1.6 MB regression fixture against the D-13 recorder (replaces stale fixture from 87909d9)"
    - ".planning/phases/01-stabilize-video-pipeline/01-07-SUMMARY.md — this file"
    - ".planning/debug/resolved/d12-blob-port-transfer-fails.md — D-12 debug session, resolved"
    - ".planning/debug/resolved/webm-playback-freeze.md — A3 debug session, resolved"
  modified:
    - ".planning/REQUIREMENTS.md — REQ-video-ring-buffer marked Complete; description AMENDED to reflect D-13 restart-segments"
    - ".planning/ROADMAP.md — Phase 1 row Complete; Success Criteria checked off; cursor-visibility refinement appended to Phase 5"
    - ".planning/STATE.md — Phase 1 closure block + frontmatter flip to phase_complete + Decisions log appended"

key-decisions:
  - "D-12 acceptance gate (ffprobe) and A3 empirical-playback gate (operator + ffmpeg dry-run) treated as TWO distinct gates. The original Plan 07 conflated them under 'ffprobe-clean'; the A3 debug session proved they are independent. Phase 1 closure required BOTH green."
  - "Plan 07 closure is auto-handled (Task 2 of original PLAN.md) — the checkpoint:human-verify returned `approved`; the auto-closure flips REQ-video-ring-buffer + STATE + ROADMAP in one atomic commit and writes this SUMMARY in another."
  - "D-09..D-11 retirement is permanent. The original D-13 'fallback if D-12 fails' framing now stands as the production approach; CONTEXT.md decisions remain on record for SPEC provenance but the executable surface is restart-segments."
  - "Cursor visibility (`video: { cursor: 'always' }`) deferred to Phase 5, not back-patched into Phase 1. Phase 1 was a stabilization phase, not a UX-refinement phase; adding the constraint mid-closure would have widened the diff beyond the closure ceremony."
  - "Phase 1 closure satisfies SPEC §10 #2, #3, #7 functionally — but the canonical §10 sweep is owned by Phase 4. This avoids confusing 'Phase 1 closed' with 'SPEC §10 complete'; the latter requires the full 9-criterion smoke under Phase 4."

patterns-established:
  - "Multi-EBML-header WebM concatenation is acceptable for the SPEC §10 #7 'plays back in a browser' criterion. Chrome's MSE pipeline handles it natively. The ffmpeg `-f null` decode dry-run produces muxer DTS-monotonicity warnings at segment join boundaries; these are NOT decoder errors and are documented as an expected D-13 trade-off — not a failure."
  - "Auto-closure of a checkpoint-gated plan: when a `checkpoint:human-verify` returns `approved`, a follow-up automation task (Task 2 of the same plan) lands the closure side-effects (REQ flip, STATE update, ROADMAP update, SUMMARY write). This pattern keeps the checkpoint task minimal and the closure ceremony atomic."
  - "Pre-staged fallbacks pay for their planning cost in the smoke step. Two-out-of-two HIGH-risk-flagged assumptions in Phase 1 (binary-transfer wire format under MV3 port serialization + VP9 keyframe orphan-P-frame risk under age-trim) failed empirically as predicted and were resolved by their pre-staged fallbacks without re-planning."

requirements-completed: [REQ-video-ring-buffer]

# Metrics
duration: "~10min (Plan 07 closure ceremony); not counting the two debug sessions (~30 min D-12, ~45 min A3) which are accounted for in their respective resolved-session files"
completed: 2026-05-15
---

# Phase 1 Plan 07: Manual Smoke + ffprobe + Empirical Playback Acceptance Gates Summary

**Two-gate phase closure (D-12 ffprobe structural + A3 empirical Chrome playback) green against `tests/fixtures/last_30sec.webm` after a three-attempt journey through two pre-staged fallback activations; REQ-video-ring-buffer complete, Phase 1 closed.**

## Performance

- **Duration:** ~10 min (closure ceremony only — three atomic commits + SUMMARY write). Plan 07's total elapsed time across all three smoke attempts was ~3.5 hours including the two debug sessions (D-12 ~30 min + A3 ~45 min); those are accounted for in the respective `.planning/debug/resolved/*.md` files.
- **Started:** 2026-05-15T21:40:00Z (this closure session, after operator returned `approved` on the checkpoint:human-verify)
- **Completed:** 2026-05-15T21:43:00Z (approx — three closure commits landed sequentially)
- **Tasks:** 2 (Task 1 = `checkpoint:human-verify` → operator returned `approved`; Task 2 = AUTOMATED closure with REQ flip + STATE update + SUMMARY)
- **Files modified:** 4 (fixture + REQUIREMENTS.md + ROADMAP.md + STATE.md) plus this SUMMARY created

## Accomplishments

- **D-12 ffprobe gate GREEN.** `ffprobe -v error -f matroska -i tests/fixtures/last_30sec.webm` returns exit 0 with empty stderr. ffprobe `-show_streams` confirms valid VP9 codec, Profile 0, 1142×1038 frame, time_base 1/1000, start_pts 0, color space bt709.
- **A3 empirical-playback gate GREEN.** Operator confirmed end-to-end Chrome playback clean — no ~1 s freeze. `ffmpeg -v warning -i tests/fixtures/last_30sec.webm -f null -` exits 0 with zero decoder errors; the only warnings are muxer DTS-monotonicity reports at segment join boundaries (expected: D-13 concatenates three self-contained multi-EBML-header WebMs; Chrome's MSE pipeline handles this natively, satisfying SPEC §10 #7 "plays back in a browser").
- **All 30/30 unit tests green** across 8 test files (`tests/offscreen/{codec-check,handshake,port,port-serialization,ring-buffer,segment-keyframes,segment-rotation,webm-playback}.test.ts`). Both empirical ffmpeg dry-runs in `webm-playback.test.ts` flipped GREEN after the fresh fixture committed in cd61cbc — previously RED against the stale 87909d9 fixture.
- **`npx tsc --noEmit` clean** at closure time; `npm run build` clean (verified during the fix-a3 cycle, unchanged since).
- **REQ-video-ring-buffer marked Complete** in REQUIREMENTS.md (checkbox + traceability table row); ROADMAP Phase 1 row marked Complete 2026-05-15.
- **D-09..D-11 retired permanently** in favor of D-13 restart-segments; CON-webm-header-retention also retired. Captured in REQUIREMENTS.md amendment + STATE.md Decisions log.
- **Cursor-visibility refinement deferred to Phase 5** — added to the P1/P2 hardening list with the explicit user-observation citation (2026-05-15).

## Task Commits

Plan 07 closure ceremony (this SUMMARY's three atomic commits):

1. **Task 1.5 (post-checkpoint): Fixture regeneration commit** — `cd61cbc` (test): replaced the stale 87909d9 fixture with the fresh D-13-recorder capture (1.6 MB VP9 1142×1038).
2. **Task 2a: Phase 1 closure flips** — `7df72aa` (feat): REQUIREMENTS.md REQ-video-ring-buffer flipped to Complete; ROADMAP.md Phase 1 row Complete + Success Criteria checked off + Phase 5 cursor-visibility appended; STATE.md Phase 1 Closure Notes block added + frontmatter to `phase_complete` + Decisions log entry.
3. **Task 2b: SUMMARY write** — `<commit-3-hash>` (docs): this SUMMARY committed.

Plan 07 also retained two prior debug-session arbitration cycles (already on the branch — they ARE the substance of Plan 07's execution, but each was committed as its own resolved-session bundle, not as Plan 07 commits per se):

- **D-12 fix cycle (5 commits):** c0d9166, d653283, 2831849, d5bb948, bf07619 — base64 wire-format binary transport.
- **A3 fix cycle (6 commits):** 5530292, 6a1a034, 670daa3, f81438d, 87909d9, 872f25d — D-13 restart-segments activation.

_Note: Plan 07's original spec called for ONE commit at Task 2 completion. The closure ceremony was split into three atomic commits (fixture / REQ-STATE-ROADMAP flip / SUMMARY) so the SUMMARY can cite the prior commits by hash and so the REQUIREMENTS/ROADMAP/STATE flip is reviewable independently of the SUMMARY's narrative._

## Files Created/Modified

**Created (this closure session):**

- `tests/fixtures/last_30sec.webm` — replaces the stale 87909d9 fixture; 1.6 MB; VP9 1142×1038; captured against the D-13 restart-segments recorder; concat of 3 × ~10 s self-contained WebM segments
- `.planning/phases/01-stabilize-video-pipeline/01-07-SUMMARY.md` — this file

**Modified (this closure session):**

- `.planning/REQUIREMENTS.md` — REQ-video-ring-buffer checkbox + description AMENDED + traceability row flipped to Complete
- `.planning/ROADMAP.md` — Phase 1 list-item + Success Criteria + Plan 07 row + Progress table row all flipped to Complete with 2026-05-15 date; Phase 5 P1/P2 list appended with `getDisplayMedia` cursor visibility refinement
- `.planning/STATE.md` — frontmatter `status` to `phase_complete`, completed_phases 0→1, completed_plans 6→7, percent 86→100; stopped_at + last_activity rewritten; Current Position rewritten for Phase 2 readiness; Performance Metrics Phase 1 row populated + Plan 07 row added; Decisions log appended with `[Phase 01-07-closure]` + `[Phase 01-07-deferred-to-5]`; Session Continuity rewritten; **Phase 1 Closure Notes** section added

**Created in prior fix cycles (referenced for context, not in this closure):**

- `src/shared/binary.ts` — D-12 fix: portable Blob ↔ base64 helpers
- `tests/offscreen/port-serialization.test.ts` — D-12 fix: 6 tests proving JSON serialization corruption + base64 round-trip pin
- `tests/offscreen/segment-keyframes.test.ts` — A3 fix: production-driven RED block (now GREEN) + documentation + GREEN-pinning blocks
- `tests/offscreen/segment-rotation.test.ts` — A3 fix: 8 tests pinning D-13 ring-buffer invariants
- `tests/offscreen/webm-playback.test.ts` — A3 fix: 2 empirical ffmpeg dry-runs (RED until fresh fixture, GREEN after cd61cbc)
- `.planning/debug/resolved/d12-blob-port-transfer-fails.md`
- `.planning/debug/resolved/webm-playback-freeze.md`

**Modified in prior fix cycles:**

- `src/shared/types.ts` — D-12: added `TransferredVideoChunk`; A3: renamed → `TransferredVideoSegment` + field renames + `isFirst` dropped
- `src/offscreen/recorder.ts` — D-12: base64 encode side; A3: D-13 restart-segments activation (the main rewrite, replacing D-09..D-11)
- `src/background/index.ts` — D-12: base64 decode side; A3: segment-semantics adaptation + `mergeVideoSegments`
- `tests/offscreen/ring-buffer.test.ts` — A3: retired to a vestigial breadcrumb after segment-rotation supersedes it

## Decisions Made

1. **Plan 07 closure is split into three atomic commits.** The original spec called for one commit at Task 2 completion. Splitting (fixture / REQ+STATE+ROADMAP flip / SUMMARY) makes each commit reviewable in isolation and lets the SUMMARY cite the fixture and closure commits by hash. Trade-off: three commits where one was specced — judged a worthwhile diff-clarity improvement.
2. **D-12 + A3 are treated as TWO distinct gates.** The original PLAN.md framed acceptance as "ffprobe-clean" (a single gate). The A3 debug session proved that a ffprobe-clean file can still freeze in Chrome playback — they are independent. Phase 1 closure requires both green, and the SUMMARY documents both gates explicitly so future phases can't conflate them.
3. **D-09..D-11 retirement is permanent.** The original D-13 framing in CONTEXT.md was "fallback if D-12 fails." After A3 activated it, D-13 IS the production approach. CONTEXT.md retains D-09..D-11 for SPEC provenance, but REQUIREMENTS.md, ROADMAP.md, and the executable surface (src/offscreen/recorder.ts) all reflect D-13 as authoritative.
4. **The muxer DTS-monotonicity warnings are NOT a failure.** ffmpeg `-f null -` prints warnings at segment join boundaries because the three concatenated WebM segments have overlapping per-segment timestamps (each segment's pts restarts at ~0 in its own EBML segment). This is the documented D-13 trade-off for multi-EBML-header WebM concat. SPEC §10 #7 only requires "plays back in a browser" — Chrome's acceptance is sufficient and was operator-confirmed.
5. **Cursor visibility refinement deferred to Phase 5, not back-patched into Phase 1.** Phase 1 is a stabilization phase; adding the `cursor: 'always'` constraint mid-closure widens the diff beyond the closure ceremony. Phase 5 is the right home for capture-quality refinements.

## Deviations from Plan

### Deviations from the ORIGINAL Plan 07 spec

**1. [Rule 4 → architectural escalation, then auto-resolved] D-12 binary transfer failure surfaced during first smoke attempt**
- **Found during:** Task 1 first attempt (operator's first ./smoke.sh run)
- **Issue:** Saved `last_30sec.webm` was 75 bytes of literal `"[object Object]"` text — chrome.runtime.Port JSON-serializes payloads across extension contexts, corrupting Blob → `{}` → `"[object Object]"` in the SW-side Blob ctor
- **Fix:** Pre-staged fallback activated — added `src/shared/binary.ts` with portable Blob ↔ base64 helpers; encoded on the offscreen side (`REQUEST_BUFFER` handler), decoded on the SW side (`BUFFER` receive)
- **Files modified:** `src/shared/binary.ts` (new), `src/shared/types.ts`, `src/offscreen/recorder.ts`, `src/background/index.ts`
- **Verification:** 6 new tests in `port-serialization.test.ts` (including a byte-exact reproduction of the 75-byte payload + a GREEN-pinning block for the base64 wire format); empirical re-smoke after fix produced a 2.1 MB ffprobe-valid WebM
- **Committed in:** c0d9166, d653283, 2831849, d5bb948, bf07619
- **Resolved-session doc:** `.planning/debug/resolved/d12-blob-port-transfer-fails.md`

**2. [Rule 4 → architectural escalation, then auto-resolved] A3 cluster-alignment freeze surfaced during second smoke attempt**
- **Found during:** Task 1 second attempt (operator's re-smoke after D-12 fix landed)
- **Issue:** The ffprobe-valid WebM froze ~1 s into Chrome playback. ffmpeg `-v warning -i ... -f null -` showed 8× `Error submitting packet to decoder: Invalid data found` + `File ended prematurely at pos. 2100851`. Root cause: D-09..D-11's age-trim evicted middle chunks containing VP9 keyframes that subsequent retained tail chunks depended on (orphan P-frames)
- **Fix:** Pre-staged fallback activated — the D-13 restart-segments skeleton commented at the bottom of `src/offscreen/recorder.ts` (lines 298-316 originally) was activated. Recorder lifecycle replaced: stop()/start() every 10 s on the same MediaStream, keep last 3 self-contained ~10 s WebM segments (3 × 10 s = 30 s preserved). Each segment is independently decodable. As a side effect, per-segment `.stop()` also fixed the "File ended prematurely" Matroska finalization gap
- **Files modified:** `src/offscreen/recorder.ts` (rewrite), `src/background/index.ts` (segment semantics + `mergeVideoSegments`), `src/shared/types.ts` (`TransferredVideoChunk` → `TransferredVideoSegment` + field renames + `isFirst` dropped), `tests/offscreen/ring-buffer.test.ts` (retired), `tests/offscreen/segment-rotation.test.ts` (new)
- **Verification:** 28/30 tests green immediately after the fix; the 2 remaining REDs were the empirical ffmpeg dry-runs against the still-stale fixture, which flipped GREEN once the fresh fixture committed in cd61cbc; operator-confirmed end-to-end Chrome playback clean
- **Committed in:** 5530292, 6a1a034, 670daa3, f81438d, 87909d9, 872f25d
- **Resolved-session doc:** `.planning/debug/resolved/webm-playback-freeze.md`

**3. [Closure ceremony split into 3 commits, not 1]** See Decisions Made #1 above.

---

**Total deviations:** 2 architectural escalations (both pre-staged fallback activations), 1 closure-ceremony commit-split. Both architectural escalations were anticipated in CONTEXT.md and RESEARCH.md (HIGH-risk flags); both pre-staged fallbacks activated cleanly without needing a fresh phase plan. The commit-split was a Plan 07 spec deviation but improves reviewability.

**Impact on plan:** The two pre-staged fallbacks paid for their planning cost in the smoke step exactly as designed. Phase 1's overall structure held; no plan re-numbering was needed; no `/gsd-insert-phase` was called. The closure ceremony itself is on-spec modulo the 3-commit split.

## Issues Encountered

Three smoke attempts, two pre-staged fallback activations, one clean acceptance.

**Attempt 1 (single-continuous MediaRecorder, originally specced under D-09..D-11):**
- Result: 75-byte text file in the archive (5 × `"[object Object]"`)
- Root cause: D-12 — chrome.runtime.Port JSON-serializes payloads, corrupting Blobs
- Resolution: Activate the base64 wire-format pre-stage from CONTEXT.md Doc Cascade

**Attempt 2 (D-12 fix landed, single-continuous recorder retained):**
- Result: 2.1 MB ffprobe-valid WebM; opens in Chrome but freezes ~1 s in
- Root cause: A3 — VP9 keyframe orphan-P-frame issue under age-trim eviction of middle chunks
- Resolution: Activate the D-13 restart-segments pre-stage from CONTEXT.md

**Attempt 3 (D-12 + A3 fixes both landed, D-13 recorder):**
- Result: 1.6 MB WebM (3 × ~10 s self-contained segments concatenated); ffprobe exit 0; ffmpeg dry-run exit 0 with zero decoder errors; operator-confirmed clean Chrome playback end-to-end
- Resolution: Commit the fresh fixture as `tests/fixtures/last_30sec.webm`; close Phase 1

## Process Observation — Candidate for GSD Framework Retro

**Plan 01-07's smoke step ended up surfacing TWO unanticipated-cascade failures (D-12 binary transfer + A3 keyframe alignment), each of which had a pre-staged fallback that activated cleanly without needing a fresh phase or replan.**

This is a real datapoint for the GSD framework. Two observations:

1. **Pre-staging works.** RESEARCH.md flagged both binary-transfer semantics under MV3 port serialization AND VP9 keyframe orphan-P-frame risk under age-trim as HIGH-risk assumptions. CONTEXT.md and PLAN.md pre-staged fallbacks for both (the Doc Cascade for binary transfer; the D-13 commented skeleton for keyframe alignment). Both HIGH-risk assumptions failed empirically, exactly as flagged. Both pre-staged fallbacks activated within ~30-45 min of detection. No re-planning was required.

2. **Plan 07's smoke step DID the empirical-acceptance-gate work that was, in spirit, what RESEARCH.md was warning about.** The smoke step is supposed to be a confirmation gate; it ended up being a discovery gate twice in a row.

**Candidate retro question for `/gsd-plan-phase`:** When RESEARCH.md flags an assumption as HIGH-risk AND a fallback is pre-staged, should the planner automatically inject an empirical-acceptance gate (e.g. ffmpeg dry-run + Chrome playback for video/codec assumptions; cross-context message round-trip test for MV3 messaging assumptions) BEFORE the phase's final commit-merge, rather than discovering the failure during the human-verify smoke step? The current sequence (Plan 01 → ... → 07 = smoke → debug session if smoke fails) works, but a slightly tighter feedback loop ("if smoke would surface a HIGH-risk-flagged failure, escalate to the pre-staged fallback BEFORE creating a debug session") might shorten the orchestration overhead in future phases that have similarly cascade-prone subject matter (codec / wire-format / container-spec work in particular).

Not a process bug — a possible process refinement. Logged here for `/gsd-plan-phase` retro consideration in Phase 2 or beyond.

This is the SECOND debug session in Phase 1's life — both written up in `.planning/debug/resolved/`. The cycle latency between "manual smoke reveals the issue" and "RED test in place + fix landed" was ~30 minutes for D-12 and ~45 minutes for A3. Acceptable but worth tightening.

## User Setup Required

None — Phase 1 ships as a Chrome extension with `desktopCapture` permission; the operator interacts with `chrome://extensions` "Load unpacked" for development and Chrome's native screen-share picker for capture. No external services configured by Phase 1.

The cursor visibility refinement (Phase 5) will, when activated, add a `cursor: 'always'` constraint to the `getDisplayMedia` call in `src/offscreen/recorder.ts` — no user action required there either, just a one-line code change in Phase 5.

## Next Phase Readiness

**Ready for Phase 2:** The offscreen now owns capture entirely. Phase 2 (DOM + event-capture privacy via rrweb v2 maskInputFn + content-script input logging) plugs into the existing content-script architecture and does NOT touch the offscreen.

**Constraints Phase 2 must respect:**

- The port `'video-keepalive'` keeps the SW alive. Phase 2's content-script work MUST NOT add competing keepalives (e.g., redundant `chrome.alarms`, redundant ports). Audit P1 #8 (alarms keepalive ineffective) was resolved in Phase 1 by deleting `chrome.alarms`; do not re-introduce it.
- The SW's `onMessage` listener validates `sender.id === chrome.runtime.id` (T-1-04 SW-side sender check, documented 4 places in `src/offscreen/recorder.ts`). Content scripts have the same extension ID and pass this check. If Phase 2 adds a new sender path (e.g., an injected page-world script via `chrome.scripting`), Phase 2 must respect the guard.
- `mergeVideoSegments` in `src/background/index.ts` IS the export path for video. Phase 2 work goes into `events.json` / `session.json`; no merge function changes needed.

**Workflow next steps (per user settings: deep code-review + verifier enabled):**

1. `/gsd-code-review` (deep code-review gate on the Phase 1 branch) — covers all 25-ish Phase 1 commits including the two debug-session fix cycles + this closure ceremony.
2. `/gsd-verify-work` (verifier — runs the full vitest + tsc + grep gates against the Phase 1 branch).
3. After both pass: merge Phase 1, plan Phase 2 via `/gsd-plan-phase 2`.

**Blockers / concerns:** None. Phase 1 is complete; the two debug sessions are documented and resolved; pre-staged fallbacks worked as designed.

## Self-Check: PASSED

Verified after writing this SUMMARY:

- `tests/fixtures/last_30sec.webm` exists (1 633 459 bytes) ✓
- `.planning/phases/01-stabilize-video-pipeline/01-07-SUMMARY.md` exists (this file) ✓
- Commit `cd61cbc` (fixture replacement) in `git log --all` ✓
- Commit `7df72aa` (closure flips) in `git log --all` ✓
- `grep -c "Phase 1 closure" .planning/STATE.md` → 3 (≥ 1) ✓
- `grep "REQ-video-ring-buffer" .planning/REQUIREMENTS.md` shows `[x]` ✓
- `grep "Complete" .planning/ROADMAP.md` shows Phase 1 row Complete 2026-05-15 ✓
- `npx vitest run` → 30/30 green ✓
- `npx tsc --noEmit` → exit 0 ✓
- ffprobe + ffmpeg dry-run both exit 0 ✓

---

*Phase: 01-stabilize-video-pipeline*
*Completed: 2026-05-15*
