bugfixes for hyperframes producer

Initial repo setup

- Eliminate redundant extractGsapWindows() call (was parsing each script
  twice, now once)
- Fix window shadowing global — renamed to win, consistent with line 655
- Split classAttr once instead of twice
- Named ClipInfo type for the selector map
- Moved clip map construction before the script loop (computed once)
- Removed orphan block scope and #1.5 numbering

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Eliminate redundant extractGsapWindows() call (was parsing each script
  twice, now once)
- Fix window shadowing global — renamed to win, consistent with line 655
- Split classAttr once instead of twice
- Named ClipInfo type for the selector map
- Moved clip map construction before the script loop (computed once)
- Removed orphan block scope and #1.5 numbering

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Eliminate redundant extractGsapWindows() call (was parsing each script
  twice, now once)
- Fix window shadowing global — renamed to win, consistent with line 655
- Split classAttr once instead of twice
- Named ClipInfo type for the selector map
- Moved clip map construction before the script loop (computed once)
- Removed orphan block scope and #1.5 numbering

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Eliminate redundant extractGsapWindows() call (was parsing each script
  twice, now once)
- Fix window shadowing global — renamed to win, consistent with line 655
- Split classAttr once instead of twice
- Named ClipInfo type for the selector map
- Moved clip map construction before the script loop (computed once)
- Removed orphan block scope and #1.5 numbering

…eadless-shell

The engine assumed any binary passed via PRODUCER_HEADLESS_SHELL_PATH
supported the HeadlessExperimental.beginFrame CDP command. When the
CLI resolved system Chrome (e.g. /usr/bin/google-chrome) instead of
chrome-headless-shell, the render would silently hang for 120s
then timeout — the #1 new-user friction point.

Now checks the binary path for "chrome-headless-shell" before
selecting beginframe capture mode. System Chrome falls back to
screenshot mode which works universally.

Reproducer:
  # On a machine with system Chrome but no chrome-headless-shell cached
  npx hyperframes init test --template blank --non-interactive
  cd test && npx hyperframes render --output out.mp4
  # Was: 120s hang, then "Timed out after waiting 120000ms"
  # Now: renders successfully via screenshot mode

…eadless-shell

The engine assumed any binary passed via PRODUCER_HEADLESS_SHELL_PATH
supported the HeadlessExperimental.beginFrame CDP command. When the
CLI resolved system Chrome (e.g. /usr/bin/google-chrome) instead of
chrome-headless-shell, the render would silently hang for 120s
then timeout — the #1 new-user friction point.

Now checks the binary path for "chrome-headless-shell" before
selecting beginframe capture mode. System Chrome falls back to
screenshot mode which works universally.

Reproducer:
  # On a machine with system Chrome but no chrome-headless-shell cached
  npx hyperframes init test --template blank --non-interactive
  cd test && npx hyperframes render --output out.mp4
  # Was: 120s hang, then "Timed out after waiting 120000ms"
  # Now: renders successfully via screenshot mode

Only one cursor may be visible at a time. Multiple cursors on
screen looks broken. Every other cursor must be cursor-hide.
Promoted to rule #1 in the cursor section.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat(skills): add gsap-effects skill with typewriter pattern

Distills typewriter text animation into a reusable reference:
basic typewriter, blinking cursor, word rotation, appending words,
and a characters-per-second timing guide. Uses GSAP TextPlugin.

Also references the new skill from compose-video.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(skills): emphasize cursor must always blink when idle and sit flush

Two key rules added to the typewriter skill:
1. Cursor must blink in every idle state (after typing, after clearing,
   during hold pauses) — a solid idle cursor looks broken.
2. No whitespace between text and cursor elements in HTML — any gap
   between the last character and the caret looks wrong.

Also adds cursor-hide state for multi-line handoffs and updates word
rotation example to include cursor state management.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(skills): backspace must delete from end, not front

TextPlugin's text:{value:""} removes characters from the front,
which looks wrong. Added a backspace helper that steps through
substrings from right to left using tl.call(). Updated word
rotation example to use it.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(skills): handoffs must blink before typing, use margin for spacing

Two lessons from testing:
1. Cursor handoffs need a blink pause — going hide→solid directly
   skips the idle state. Pattern: hide→blink→pause→solid→type→blink.
2. Use margin-left on a wrapper span for spacing between static and
   dynamic text. Flex gap spaces the cursor away, trailing spaces
   collapse.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(skills): enforce single visible cursor as a hard rule

Only one cursor may be visible at a time. Multiple cursors on
screen looks broken. Every other cursor must be cursor-hide.
Promoted to rule #1 in the cursor section.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

…209)

## Summary

Two independent initiatives that improve agent DX and expand HyperFrames' reach.

### Initiative 1: Fix the Clip Animation Footgun

- `gsap_animates_clip_element` lint rule now uses smart detection — only errors when GSAP animates `visibility` or `display` on a clip element
- All other properties (opacity, transform, x, y, scale, etc.) are allowed silently
- This was the #1 agent failure in QA (10/10 agents hit it on v0.2.1)

### Initiative 2: `<hyperframes-player>` Web Component

- New `@hyperframes/player` package — zero dependencies, 3.3KB gzipped
- Iframe-based web component with Shadow DOM for perfect isolation
- Video-like API: `play()`, `pause()`, `seek()`, `currentTime`, `duration`, events
- Controls overlay with play/pause, scrubber (mouse + touch), time display, auto-hide
- Full docs page at `docs/packages/player.mdx`

## Before / After

### Clip animation lint

**Before (10/10 agents hit this):**

```
✗ gsap_animates_clip_element: GSAP animation targets a clip element.
  Selector "#title" resolves to element <div id="title" class="clip">.
  The framework manages clip visibility — animate an inner wrapper instead.
  Fix: Wrap content in a child <div> and target that with GSAP.
```

**After (only errors on actual conflicts):**

```
# This passes lint — no error:
tl.from("#title", { opacity: 0, y: -50, scale: 0.8 }, 0);

# This still errors — actual conflict with runtime:
tl.to("#title", { visibility: "hidden" }, 3);
✗ gsap_animates_clip_element: GSAP animation sets visibility on a clip element.
  Fix: Remove the visibility/display tween. Use opacity for fade effects.
```

### Embeddable player

**Before:** No way to embed a composition in a web page.
**After:**

```html
<script src="https://cdn.jsdelivr.net/npm/@hyperframes/player"></script>
<hyperframes-player src="./composition/index.html" controls></hyperframes-player>
```

```js
const player = document.querySelector('hyperframes-player');
player.play();
player.pause();
player.seek(2.5);
player.addEventListener('ready', (e) => console.log('Duration:', e.detail.duration));
```

## Test plan

- [x] 427 core tests pass (20 GSAP lint tests with smart detection)
- [x] 7 player tests pass (formatTime + element registration)
- [x] TypeScript compiles cleanly (core + player)
- [x] Lint: GSAP animating clip with safe props → 0 errors
- [x] Lint: GSAP animating clip with `visibility` → 1 error (correct)
- [x] Player builds to 3.3KB gzipped ESM
- [x] Lockfile updated for CI
- [x] Docs page added at `docs/packages/player.mdx`

PR 8.4 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). User-facing docs catch up with the
shipped capability.

Updates docs/deploy/migrating-to-hyperframes-lambda.mdx:

- "Output format" row in the migration table now lists `webm` alongside
  mp4 / mov / png-sequence with a note that webm uses libvpx-vp9 +
  closed-GOP concat-copy. HDR mp4 remains the only refused format.

- "No webm distributed" caveat replaced with "webm uses closed-GOP VP9"
  explainer covering the encoder args (`-g <chunkSize>`,
  `-keyint_min <chunkSize>`, `-auto-alt-ref 0`, `-cpu-used 2`), why
  alt-ref disable is load-bearing, and that the output preserves alpha
  via yuva420p with Opus audio.

- Migration checklist no longer asks adopters to filter out webm
  compositions; only HDR-dependent renders need to stay on the previous
  framework.

aws-lambda.mdx doesn't currently call out webm as unsupported (only HDR
in the v1 surface list), so it gets no copy edits beyond the migration
guide.

The internal planning doc (DISTRIBUTED-RENDERING-PLAN.md §7.2, §8,
§12 — kept outside the repo) gets matching updates: format support
matrix flipped ✓, v1.5 backlog #1 marked shipped, HDR promoted to the
new top item, and the rev-12 → rev-13 status line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

PR 8.4 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). User-facing docs catch up with the
shipped capability.

Updates docs/deploy/migrating-to-hyperframes-lambda.mdx:

- "Output format" row in the migration table now lists `webm` alongside
  mp4 / mov / png-sequence with a note that webm uses libvpx-vp9 +
  closed-GOP concat-copy. HDR mp4 remains the only refused format.

- "No webm distributed" caveat replaced with "webm uses closed-GOP VP9"
  explainer covering the encoder args (`-g <chunkSize>`,
  `-keyint_min <chunkSize>`, `-auto-alt-ref 0`, `-cpu-used 2`), why
  alt-ref disable is load-bearing, and that the output preserves alpha
  via yuva420p with Opus audio.

- Migration checklist no longer asks adopters to filter out webm
  compositions; only HDR-dependent renders need to stay on the previous
  framework.

aws-lambda.mdx doesn't currently call out webm as unsupported (only HDR
in the v1 surface list), so it gets no copy edits beyond the migration
guide.

The internal planning doc (DISTRIBUTED-RENDERING-PLAN.md §7.2, §8,
§12 — kept outside the repo) gets matching updates: format support
matrix flipped ✓, v1.5 backlog #1 marked shipped, HDR promoted to the
new top item, and the rev-12 → rev-13 status line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

PR 8.4 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). User-facing docs catch up with the
shipped capability.

Updates docs/deploy/migrating-to-hyperframes-lambda.mdx:

- "Output format" row in the migration table now lists `webm` alongside
  mp4 / mov / png-sequence with a note that webm uses libvpx-vp9 +
  closed-GOP concat-copy. HDR mp4 remains the only refused format.

- "No webm distributed" caveat replaced with "webm uses closed-GOP VP9"
  explainer covering the encoder args (`-g <chunkSize>`,
  `-keyint_min <chunkSize>`, `-auto-alt-ref 0`, `-cpu-used 2`), why
  alt-ref disable is load-bearing, and that the output preserves alpha
  via yuva420p with Opus audio.

- Migration checklist no longer asks adopters to filter out webm
  compositions; only HDR-dependent renders need to stay on the previous
  framework.

aws-lambda.mdx doesn't currently call out webm as unsupported (only HDR
in the v1 surface list), so it gets no copy edits beyond the migration
guide.

The internal planning doc (DISTRIBUTED-RENDERING-PLAN.md §7.2, §8,
§12 — kept outside the repo) gets matching updates: format support
matrix flipped ✓, v1.5 backlog #1 marked shipped, HDR promoted to the
new top item, and the rev-12 → rev-13 status line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

PR 8.2 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). Wires libvpx-vp9 webm through the
distributed pipeline now that PR 8.1 proved concat-copy works.

Architectural decision: Path A (concat-copy) — based on PR 8.1's smoke
test result (9/9 tests pass for both yuv420p and yuva420p VP9 streams).
The simpler architecture wins; no re-encode in assemble, no encode-
parallelism loss.

Changes:

- plan.ts:
  - DistributedRenderConfig.format and PlanResult.format now include
    "webm" — type-level acceptance matches the runtime gate.
  - rejectUnsupportedDistributedFormat() no longer trips on webm. HDR
    mp4 remains the only refused configuration.
  - resolveEncoderTriple() returns libvpx-vp9-software + yuva420p +
    preset="good" for format="webm". yuva420p preserves alpha — the
    format's main reason for existing for web delivery.
  - codec= remains rejected for non-mp4 formats (mov is always ProRes
    4444; webm is always libvpx-vp9). The error message lists all four
    distributed-supported formats.
  - FormatNotSupportedInDistributedError docstring updated to reflect
    the new reality (only HDR is unsupported).

- freezePlan.ts: LockedRenderConfig.encoder gains "libvpx-vp9-software".
  Mirrors libx265-software / prores-software / png-sequence in shape;
  the chunk worker reads this discriminant to decide encode args.

- renderChunk.ts: drops the now-incorrect cast that excluded webm from
  buildSyntheticRenderJob's format input; tightens the preset-format
  cast to include webm.

- assemble.ts: docstring + comment updates. The mp4/mov concat-copy
  path is format-agnostic — webm uses the exact same code (applyFaststart
  is a no-op for webm via the existing chunkEncoder.ts gate;
  muxVideoWithAudio already routes webm to libopus audio).

- planFormatBanlist.test.ts: webm-rejection tests removed; replaced with
  "accepts webm" tests + a HDR+webm combo test that verifies HDR is the
  trip regardless of format.

- plan.test.ts: new describe block pins the webm wiring contract:
  format="webm" produces an encoder=libvpx-vp9-software /
  pixelFormat=yuva420p planDir with closedGop=true and gopSize=chunkSize.

- webm-concat-copy.test.ts (smoke): extended with a yuva420p variant
  that proves the alpha pixel format the distributed pipeline actually
  emits also round-trips through concat-copy. 9/9 tests pass locally.

§8 format support matrix in DISTRIBUTED-RENDERING-PLAN.md is intentionally
left unchanged at this PR — it flips to ✓ in PR 8.4 once the end-to-end
fixture (PR 8.3) is green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

PR 8.3 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). End-to-end regression coverage for
the webm distributed path PRs 8.1 and 8.2 wired up.

Adds packages/producer/tests/distributed/webm-vp9/ matching the
mp4-h264-sdr fixture pattern: a 2-second composition (60 frames @ 30fps)
with text, a crossfade across the frame-30 chunk seam, and a continuous
icon rotation — exercises chunk-boundary continuity for both display
contents and VP9 closed-GOP alpha encoding. `chunkSize: 15` produces 4
chunks so 3 seams are tested, and the crossfade straddles the middle
seam to surface alpha-plane discontinuities introduced by alt-ref drift.

Baseline regenerated inside Dockerfile.test via
`bun run --cwd packages/producer docker:test:update webm-vp9`. Runs in:

  - in-process mode: byte-identical match against baseline ✓
  - distributed-simulated mode: PSNR 56.88-63.49 dB across 100
    checkpoints, well above the 30 dB threshold ✓

Wiring updates required to let webm flow through the harness:

- regression-harness-distributed.ts:
  - checkDistributedSupport() no longer rejects webm. HDR mp4 + NTSC
    fps + non-{24,30,60} fps remain rejected.
  - RunDistributedSimulatedInput.format widened to include webm.
  - Docstring + comments updated.

- regression-harness-distributed.test.ts: webm-rejection test replaced
  with "accepts format=webm" test.

- regression-harness.ts: the now-incorrect format cast at the
  distributed-input call site is dropped; comment about why webm was
  excluded is replaced with "webm is now distributed-supported".

- regression-harness-lambda-local-types.ts: RunLambdaLocalInput.format
  widened to include webm so lambda-local mode can also exercise webm
  fixtures end-to-end.

- aws-lambda webm support (Path A through the Lambda handler):
  - formatExtension.ts: DistributedFormat gains "webm" → ".webm" case.
  - events.ts: RenderChunkEvent / AssembleEvent / PlanLambdaResult
    Format widened to include webm.
  - sdk/validateConfig.ts: ALLOWED_FORMATS gains "webm".
  - handler.ts: downloadChunkObjects format param widened.

The Lambda handler delegates to the producer's assemble() primitive
which PR 8.2 already taught to handle webm (concat-copy + applyFaststart
no-op + muxVideoWithAudio with libopus); no Lambda-side rendering
changes are needed beyond the type/validation surfaces above.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

PR 8.4 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). User-facing docs catch up with the
shipped capability.

Updates docs/deploy/migrating-to-hyperframes-lambda.mdx:

- "Output format" row in the migration table now lists `webm` alongside
  mp4 / mov / png-sequence with a note that webm uses libvpx-vp9 +
  closed-GOP concat-copy. HDR mp4 remains the only refused format.

- "No webm distributed" caveat replaced with "webm uses closed-GOP VP9"
  explainer covering the encoder args (`-g <chunkSize>`,
  `-keyint_min <chunkSize>`, `-auto-alt-ref 0`, `-cpu-used 2`), why
  alt-ref disable is load-bearing, and that the output preserves alpha
  via yuva420p with Opus audio.

- Migration checklist no longer asks adopters to filter out webm
  compositions; only HDR-dependent renders need to stay on the previous
  framework.

aws-lambda.mdx doesn't currently call out webm as unsupported (only HDR
in the v1 surface list), so it gets no copy edits beyond the migration
guide.

The internal planning doc (DISTRIBUTED-RENDERING-PLAN.md §7.2, §8,
§12 — kept outside the repo) gets matching updates: format support
matrix flipped ✓, v1.5 backlog #1 marked shipped, HDR promoted to the
new top item, and the rev-12 → rev-13 status line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

PR 8.4 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). User-facing docs catch up with the
shipped capability.

Updates docs/deploy/migrating-to-hyperframes-lambda.mdx:

- "Output format" row in the migration table now lists `webm` alongside
  mp4 / mov / png-sequence with a note that webm uses libvpx-vp9 +
  closed-GOP concat-copy. HDR mp4 remains the only refused format.

- "No webm distributed" caveat replaced with "webm uses closed-GOP VP9"
  explainer covering the encoder args (`-g <chunkSize>`,
  `-keyint_min <chunkSize>`, `-auto-alt-ref 0`, `-cpu-used 2`), why
  alt-ref disable is load-bearing, and that the output preserves alpha
  via yuva420p with Opus audio.

- Migration checklist no longer asks adopters to filter out webm
  compositions; only HDR-dependent renders need to stay on the previous
  framework.

aws-lambda.mdx doesn't currently call out webm as unsupported (only HDR
in the v1 surface list), so it gets no copy edits beyond the migration
guide.

The internal planning doc (DISTRIBUTED-RENDERING-PLAN.md §7.2, §8,
§12 — kept outside the repo) gets matching updates: format support
matrix flipped ✓, v1.5 backlog #1 marked shipped, HDR promoted to the
new top item, and the rev-12 → rev-13 status line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

PR 8.4 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). User-facing docs catch up with the
shipped capability.

Updates docs/deploy/migrating-to-hyperframes-lambda.mdx:

- "Output format" row in the migration table now lists `webm` alongside
  mp4 / mov / png-sequence with a note that webm uses libvpx-vp9 +
  closed-GOP concat-copy. HDR mp4 remains the only refused format.

- "No webm distributed" caveat replaced with "webm uses closed-GOP VP9"
  explainer covering the encoder args (`-g <chunkSize>`,
  `-keyint_min <chunkSize>`, `-auto-alt-ref 0`, `-cpu-used 2`), why
  alt-ref disable is load-bearing, and that the output preserves alpha
  via yuva420p with Opus audio.

- Migration checklist no longer asks adopters to filter out webm
  compositions; only HDR-dependent renders need to stay on the previous
  framework.

aws-lambda.mdx doesn't currently call out webm as unsupported (only HDR
in the v1 surface list), so it gets no copy edits beyond the migration
guide.

The internal planning doc (DISTRIBUTED-RENDERING-PLAN.md §7.2, §8,
§12 — kept outside the repo) gets matching updates: format support
matrix flipped ✓, v1.5 backlog #1 marked shipped, HDR promoted to the
new top item, and the rev-12 → rev-13 status line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* feat(producer): enable webm in distributed mode via concat-copy

PR 8.2 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). Wires libvpx-vp9 webm through the
distributed pipeline now that PR 8.1 proved concat-copy works.

Architectural decision: Path A (concat-copy) — based on PR 8.1's smoke
test result (9/9 tests pass for both yuv420p and yuva420p VP9 streams).
The simpler architecture wins; no re-encode in assemble, no encode-
parallelism loss.

Changes:

- plan.ts:
  - DistributedRenderConfig.format and PlanResult.format now include
    "webm" — type-level acceptance matches the runtime gate.
  - rejectUnsupportedDistributedFormat() no longer trips on webm. HDR
    mp4 remains the only refused configuration.
  - resolveEncoderTriple() returns libvpx-vp9-software + yuva420p +
    preset="good" for format="webm". yuva420p preserves alpha — the
    format's main reason for existing for web delivery.
  - codec= remains rejected for non-mp4 formats (mov is always ProRes
    4444; webm is always libvpx-vp9). The error message lists all four
    distributed-supported formats.
  - FormatNotSupportedInDistributedError docstring updated to reflect
    the new reality (only HDR is unsupported).

- freezePlan.ts: LockedRenderConfig.encoder gains "libvpx-vp9-software".
  Mirrors libx265-software / prores-software / png-sequence in shape;
  the chunk worker reads this discriminant to decide encode args.

- renderChunk.ts: drops the now-incorrect cast that excluded webm from
  buildSyntheticRenderJob's format input; tightens the preset-format
  cast to include webm.

- assemble.ts: docstring + comment updates. The mp4/mov concat-copy
  path is format-agnostic — webm uses the exact same code (applyFaststart
  is a no-op for webm via the existing chunkEncoder.ts gate;
  muxVideoWithAudio already routes webm to libopus audio).

- planFormatBanlist.test.ts: webm-rejection tests removed; replaced with
  "accepts webm" tests + a HDR+webm combo test that verifies HDR is the
  trip regardless of format.

- plan.test.ts: new describe block pins the webm wiring contract:
  format="webm" produces an encoder=libvpx-vp9-software /
  pixelFormat=yuva420p planDir with closedGop=true and gopSize=chunkSize.

- webm-concat-copy.test.ts (smoke): extended with a yuva420p variant
  that proves the alpha pixel format the distributed pipeline actually
  emits also round-trips through concat-copy. 9/9 tests pass locally.

§8 format support matrix in DISTRIBUTED-RENDERING-PLAN.md is intentionally
left unchanged at this PR — it flips to ✓ in PR 8.4 once the end-to-end
fixture (PR 8.3) is green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(producer): include webm in plan-time needsAlpha + strengthen alpha smoke

PR review feedback from Miguel and Vai on #951 caught a real bug:
`plan.ts`'s `needsAlpha` disjunction excluded `"webm"`, so the plan
stage froze `forceScreenshot: false` into the `LockedRenderConfig`
even though distributed webm uses `yuva420p`. Every chunk worker
captured opaque RGB via BeginFrame (which doesn't preserve alpha on
Linux headless-shell), and libvpx-vp9 encoded uniformly-opaque alpha
that the encoder then dropped — producing un-keyable webm.

Two changes:

1. **plan.ts**: include `"webm"` in `needsAlpha`. Matches the
   in-process renderer's logic at `renderOrchestrator.ts:1469`
   (`const needsAlpha = isWebm || isMov || isPngSequence`); the two
   sites must stay in sync since the distributed pipeline's PSNR
   regression compares against the in-process baseline.

2. **Smoke test (yuva420p describe)**: source frames now use a real
   alpha gradient (`geq=a='X*255/W'` on top of `testsrc2`) instead of
   `testsrc2 + format=rgba` which was uniformly opaque. The decode-
   pix_fmt assertion is dropped (ffprobe reports `yuv420p` for
   VP9-with-alpha because the alpha lives in a Matroska
   `BlockAdditional` sidecar) and replaced with two stronger checks:
   - `TAG:ALPHA_MODE=1` is present on the stream — proves the
     encoder was actually configured for alpha
   - alpha plane variance after `-c:v libvpx-vp9 -i ... -pix_fmt rgba
     -vf extractplanes=a,signalstats` — proves the alpha sub-stream
     round-trips through concat-copy with spatially-varying content,
     not uniform/dropped alpha
   - decode-test gate is now exit-code-only (was `exitCode || stderr`
     which would flake on chatty ffmpeg `-v error` builds emitting
     non-fatal DTS/container notes)

These checks would have caught the `needsAlpha` bug before review.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(aws-lambda): widen narrow format types to include webm

CI on PR #951 was failing at typecheck/build because the producer's
`DistributedRenderConfig.format` widened to include webm in this PR
but the aws-lambda package's narrow `"mp4" | "mov" | "png-sequence"`
type literals in `events.ts`, `handler.ts`, and `validateConfig.ts`
hadn't kept up. `renderToLambda.ts:87` passed `config.format` (now
including webm) into a parameter typed against the narrow union,
producing TS2345.

This widening originally landed in PR #952 (test fixture PR) but
needs to be atomic with the producer's widening here to keep each
PR independently typecheck-clean.

Also refactor `formatExtension` from a switch dispatch to a
`Record<DistributedFormat, string>` lookup. Adding the webm case
tipped the switch's CRAP to the 30.0 fallow threshold; the lookup
table drops cyclomatic from 5 to 1 with the same compile-time
exhaustiveness guarantee (TS errors on missing entries when
`DistributedFormat` adds a new format). The runtime
`_exhaustive: never` throw was only protecting against a string
slipping past TS; `validateConfig.ts`'s `ALLOWED_FORMATS` already
gates untrusted input at the SDK boundary.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* feat(producer): enable webm in distributed mode via concat-copy

PR 8.2 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). Wires libvpx-vp9 webm through the
distributed pipeline now that PR 8.1 proved concat-copy works.

Architectural decision: Path A (concat-copy) — based on PR 8.1's smoke
test result (9/9 tests pass for both yuv420p and yuva420p VP9 streams).
The simpler architecture wins; no re-encode in assemble, no encode-
parallelism loss.

Changes:

- plan.ts:
  - DistributedRenderConfig.format and PlanResult.format now include
    "webm" — type-level acceptance matches the runtime gate.
  - rejectUnsupportedDistributedFormat() no longer trips on webm. HDR
    mp4 remains the only refused configuration.
  - resolveEncoderTriple() returns libvpx-vp9-software + yuva420p +
    preset="good" for format="webm". yuva420p preserves alpha — the
    format's main reason for existing for web delivery.
  - codec= remains rejected for non-mp4 formats (mov is always ProRes
    4444; webm is always libvpx-vp9). The error message lists all four
    distributed-supported formats.
  - FormatNotSupportedInDistributedError docstring updated to reflect
    the new reality (only HDR is unsupported).

- freezePlan.ts: LockedRenderConfig.encoder gains "libvpx-vp9-software".
  Mirrors libx265-software / prores-software / png-sequence in shape;
  the chunk worker reads this discriminant to decide encode args.

- renderChunk.ts: drops the now-incorrect cast that excluded webm from
  buildSyntheticRenderJob's format input; tightens the preset-format
  cast to include webm.

- assemble.ts: docstring + comment updates. The mp4/mov concat-copy
  path is format-agnostic — webm uses the exact same code (applyFaststart
  is a no-op for webm via the existing chunkEncoder.ts gate;
  muxVideoWithAudio already routes webm to libopus audio).

- planFormatBanlist.test.ts: webm-rejection tests removed; replaced with
  "accepts webm" tests + a HDR+webm combo test that verifies HDR is the
  trip regardless of format.

- plan.test.ts: new describe block pins the webm wiring contract:
  format="webm" produces an encoder=libvpx-vp9-software /
  pixelFormat=yuva420p planDir with closedGop=true and gopSize=chunkSize.

- webm-concat-copy.test.ts (smoke): extended with a yuva420p variant
  that proves the alpha pixel format the distributed pipeline actually
  emits also round-trips through concat-copy. 9/9 tests pass locally.

§8 format support matrix in DISTRIBUTED-RENDERING-PLAN.md is intentionally
left unchanged at this PR — it flips to ✓ in PR 8.4 once the end-to-end
fixture (PR 8.3) is green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(producer): include webm in plan-time needsAlpha + strengthen alpha smoke

PR review feedback from Miguel and Vai on #951 caught a real bug:
`plan.ts`'s `needsAlpha` disjunction excluded `"webm"`, so the plan
stage froze `forceScreenshot: false` into the `LockedRenderConfig`
even though distributed webm uses `yuva420p`. Every chunk worker
captured opaque RGB via BeginFrame (which doesn't preserve alpha on
Linux headless-shell), and libvpx-vp9 encoded uniformly-opaque alpha
that the encoder then dropped — producing un-keyable webm.

Two changes:

1. **plan.ts**: include `"webm"` in `needsAlpha`. Matches the
   in-process renderer's logic at `renderOrchestrator.ts:1469`
   (`const needsAlpha = isWebm || isMov || isPngSequence`); the two
   sites must stay in sync since the distributed pipeline's PSNR
   regression compares against the in-process baseline.

2. **Smoke test (yuva420p describe)**: source frames now use a real
   alpha gradient (`geq=a='X*255/W'` on top of `testsrc2`) instead of
   `testsrc2 + format=rgba` which was uniformly opaque. The decode-
   pix_fmt assertion is dropped (ffprobe reports `yuv420p` for
   VP9-with-alpha because the alpha lives in a Matroska
   `BlockAdditional` sidecar) and replaced with two stronger checks:
   - `TAG:ALPHA_MODE=1` is present on the stream — proves the
     encoder was actually configured for alpha
   - alpha plane variance after `-c:v libvpx-vp9 -i ... -pix_fmt rgba
     -vf extractplanes=a,signalstats` — proves the alpha sub-stream
     round-trips through concat-copy with spatially-varying content,
     not uniform/dropped alpha
   - decode-test gate is now exit-code-only (was `exitCode || stderr`
     which would flake on chatty ffmpeg `-v error` builds emitting
     non-fatal DTS/container notes)

These checks would have caught the `needsAlpha` bug before review.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(aws-lambda): widen narrow format types to include webm

CI on PR #951 was failing at typecheck/build because the producer's
`DistributedRenderConfig.format` widened to include webm in this PR
but the aws-lambda package's narrow `"mp4" | "mov" | "png-sequence"`
type literals in `events.ts`, `handler.ts`, and `validateConfig.ts`
hadn't kept up. `renderToLambda.ts:87` passed `config.format` (now
including webm) into a parameter typed against the narrow union,
producing TS2345.

This widening originally landed in PR #952 (test fixture PR) but
needs to be atomic with the producer's widening here to keep each
PR independently typecheck-clean.

Also refactor `formatExtension` from a switch dispatch to a
`Record<DistributedFormat, string>` lookup. Adding the webm case
tipped the switch's CRAP to the 30.0 fallow threshold; the lookup
table drops cyclomatic from 5 to 1 with the same compile-time
exhaustiveness guarantee (TS errors on missing entries when
`DistributedFormat` adds a new format). The runtime
`_exhaustive: never` throw was only protecting against a string
slipping past TS; `validateConfig.ts`'s `ALLOWED_FORMATS` already
gates untrusted input at the SDK boundary.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* test(producer): add webm-vp9 distributed regression fixture

PR 8.3 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). End-to-end regression coverage for
the webm distributed path PRs 8.1 and 8.2 wired up.

Adds packages/producer/tests/distributed/webm-vp9/ matching the
mp4-h264-sdr fixture pattern: a 2-second composition (60 frames @ 30fps)
with text, a crossfade across the frame-30 chunk seam, and a continuous
icon rotation — exercises chunk-boundary continuity for both display
contents and VP9 closed-GOP alpha encoding. `chunkSize: 15` produces 4
chunks so 3 seams are tested, and the crossfade straddles the middle
seam to surface alpha-plane discontinuities introduced by alt-ref drift.

Baseline regenerated inside Dockerfile.test via
`bun run --cwd packages/producer docker:test:update webm-vp9`. Runs in:

  - in-process mode: byte-identical match against baseline ✓
  - distributed-simulated mode: PSNR 56.88-63.49 dB across 100
    checkpoints, well above the 30 dB threshold ✓

Wiring updates required to let webm flow through the harness:

- regression-harness-distributed.ts:
  - checkDistributedSupport() no longer rejects webm. HDR mp4 + NTSC
    fps + non-{24,30,60} fps remain rejected.
  - RunDistributedSimulatedInput.format widened to include webm.
  - Docstring + comments updated.

- regression-harness-distributed.test.ts: webm-rejection test replaced
  with "accepts format=webm" test.

- regression-harness.ts: the now-incorrect format cast at the
  distributed-input call site is dropped; comment about why webm was
  excluded is replaced with "webm is now distributed-supported".

- regression-harness-lambda-local-types.ts: RunLambdaLocalInput.format
  widened to include webm so lambda-local mode can also exercise webm
  fixtures end-to-end.

- aws-lambda webm support (Path A through the Lambda handler):
  - formatExtension.ts: DistributedFormat gains "webm" → ".webm" case.
  - events.ts: RenderChunkEvent / AssembleEvent / PlanLambdaResult
    Format widened to include webm.
  - sdk/validateConfig.ts: ALLOWED_FORMATS gains "webm".
  - handler.ts: downloadChunkObjects format param widened.

The Lambda handler delegates to the producer's assemble() primitive
which PR 8.2 already taught to handle webm (concat-copy + applyFaststart
no-op + muxVideoWithAudio with libopus); no Lambda-side rendering
changes are needed beyond the type/validation surfaces above.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* docs(aws-lambda): drop stale webm rejection from validateConfig docblock

PR #952 review nit (Miguel): the validateConfig.ts file-header comment
still claimed the SDK rejects webm, but the runtime check no longer
does (ALLOWED_FORMATS now includes 'webm'). Update the docblock to
reflect that only force-hdr remains an SDK-side rejection.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* ci(regression): add webm-vp9 to shard-3 + refactor formatExtension

Three follow-ups bundled together (Vai's review feedback on PR #952
plus the fallow audit finding that surfaced when the webm case was
added):

1. **Wire webm-vp9 into CI regression.** The fixture was added in this
   PR but never appeared in any `.github/workflows/regression.yml`
   shard's args allowlist, so the regression harness's positional-args
   gate skipped it in CI. Append `webm-vp9` to shard-3 (which already
   carries `mp4-h264-sdr` + `webm-transparency`) so the fixture runs.

2. **Fix stale "four hard gates" prose in checkDistributedSupport
   docstring.** Earlier in the stack I removed the webm bullet but
   didn't update the count. Two gates remain (fps + hdr).

3. **Refactor `formatExtension` from switch to lookup table.** Adding
   the webm case made the switch dispatch's CRAP score hit 30.0
   (cyclomatic = 5, plus the function's small body). Replaced with a
   `Record<DistributedFormat, string>` lookup, which:
   - drops cyclomatic from 5 → 1,
   - keeps exhaustiveness enforcement at compile time (TS errors if
     a new format gets added to `DistributedFormat` without a
     matching key in the Record literal),
   - drops the runtime `_exhaustive: never` throw, which was only
     guarding against an arbitrary string slipping past TS — a
     caller-side concern, not this function's job.

   The function now reads as a table lookup, which matches what it
   actually does, and the fallow audit now reports zero new
   complexity findings (down from 1).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

PR 8.4 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). User-facing docs catch up with the
shipped capability.

Updates docs/deploy/migrating-to-hyperframes-lambda.mdx:

- "Output format" row in the migration table now lists `webm` alongside
  mp4 / mov / png-sequence with a note that webm uses libvpx-vp9 +
  closed-GOP concat-copy. HDR mp4 remains the only refused format.

- "No webm distributed" caveat replaced with "webm uses closed-GOP VP9"
  explainer covering the encoder args (`-g <chunkSize>`,
  `-keyint_min <chunkSize>`, `-auto-alt-ref 0`, `-cpu-used 2`), why
  alt-ref disable is load-bearing, and that the output preserves alpha
  via yuva420p with Opus audio.

- Migration checklist no longer asks adopters to filter out webm
  compositions; only HDR-dependent renders need to stay on the previous
  framework.

aws-lambda.mdx doesn't currently call out webm as unsupported (only HDR
in the v1 surface list), so it gets no copy edits beyond the migration
guide.

The internal planning doc (DISTRIBUTED-RENDERING-PLAN.md §7.2, §8,
§12 — kept outside the repo) gets matching updates: format support
matrix flipped ✓, v1.5 backlog #1 marked shipped, HDR promoted to the
new top item, and the rev-12 → rev-13 status line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* docs(lambda): document webm support in distributed mode

PR 8.4 of the WebM distributed-rendering plan (v1.5 backlog #1; see
DISTRIBUTED-RENDERING-PLAN.md §7.2). User-facing docs catch up with the
shipped capability.

Updates docs/deploy/migrating-to-hyperframes-lambda.mdx:

- "Output format" row in the migration table now lists `webm` alongside
  mp4 / mov / png-sequence with a note that webm uses libvpx-vp9 +
  closed-GOP concat-copy. HDR mp4 remains the only refused format.

- "No webm distributed" caveat replaced with "webm uses closed-GOP VP9"
  explainer covering the encoder args (`-g <chunkSize>`,
  `-keyint_min <chunkSize>`, `-auto-alt-ref 0`, `-cpu-used 2`), why
  alt-ref disable is load-bearing, and that the output preserves alpha
  via yuva420p with Opus audio.

- Migration checklist no longer asks adopters to filter out webm
  compositions; only HDR-dependent renders need to stay on the previous
  framework.

aws-lambda.mdx doesn't currently call out webm as unsupported (only HDR
in the v1 surface list), so it gets no copy edits beyond the migration
guide.

The internal planning doc (DISTRIBUTED-RENDERING-PLAN.md §7.2, §8,
§12 — kept outside the repo) gets matching updates: format support
matrix flipped ✓, v1.5 backlog #1 marked shipped, HDR promoted to the
new top item, and the rev-12 → rev-13 status line.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* refactor: address simplify-review findings on webm stack

Folds in cleanups identified by a multi-agent code-review pass over the
4-PR webm-distributed stack:

- plan.ts: `resolveEncoderTriple()` webm case now calls
  `getEncoderPreset(quality, "webm")` for its preset string instead of
  hardcoding "good". The hardcode was wrong for `quality: "draft"`
  (`getEncoderPreset` returns "realtime" for that tier) — would have
  silently overridden the draft → realtime mapping for distributed webm
  renders.
- chunkEncoder.ts: trim the new VP9 closed-GOP comment block from ~18
  lines of WHY narration down to the 6 lines that actually explain why
  (alt-ref + cpu-used drift). Match the alpha branch's idempotent-push
  comment to the same standard.
- chunkEncoder.test.ts: drop the duplicate WHY comment that restated
  the implementation comment in plain words.
- webm-concat-copy.test.ts: rewrite the file-header docstring to
  describe the contract being tested instead of the PR-8.1-gating
  history; strip "PR 8.2 / Path A / Path B" references from error
  messages (they belong in PR bodies, not in test output). Consolidate
  the yuva420p alpha smoke into a single `it()` block (was a full
  4-test describe with duplicated setup) — the yuv420p block already
  covers the probe/decode/frame-count contract; the alpha smoke only
  needs to prove the alpha args don't break concat-copy.
- plan.test.ts: drop the "PR 8.1 proved the contract" comment.
- webm-vp9 fixture: drop the aspirational "Other webm-with-audio
  fixtures cover the mux path separately when added" sentence (no
  other fixtures exist). Regenerated the baseline via
  `docker:test:update webm-vp9` to reflect the updated comment.
- migrating-to-hyperframes-lambda.mdx: add a paragraph about
  distributed webm's perf cost — ~10-25% larger files at constant CRF
  due to forced keyframes, and slower per-chunk encode due to
  `-cpu-used 2` being more conservative than the libvpx default.

All unit tests + the webm-vp9 distributed-simulated regression still
pass after these changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(cli): accept --format=webm in `hyperframes lambda render`

The CLI's `lambda render` subcommand's FORMATS allowlist and the
`RenderArgs.format` type still narrowed to `mp4 | mov | png-sequence`,
so even though the producer + aws-lambda packages now support webm
end-to-end, the CLI surface rejected it with `--format must be mp4|mov|
png-sequence`. Add webm to both spots and update the --help description.

Surfaced during real-AWS deploy prep — the local lambda-local /
distributed-simulated tests didn't go through the CLI so the gap went
unnoticed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(producer): font cache writes to /tmp on Lambda (read-only \$HOME)

The deterministic Google Fonts cache was rooted at
`\$HOME/.cache/hyperframes/fonts`, which fails on AWS Lambda — the
runtime's `\$HOME` resolves to a `/home/sbx_*` directory tree that's
read-only. `mkdirSync(..., { recursive: true })` can't create that
path and the plan stage trips with `ENOENT: no such file or directory,
mkdir '/home/sbx_user1051/.cache/hyperframes/fonts/space-mono'` on
every Lambda render that pulls a Google Font (i.e. every distributed
fixture using `@import url("https://fonts.googleapis.com/...")`).

Detect Lambda via `\$AWS_LAMBDA_FUNCTION_NAME` and route the cache to
`tmpdir()/hyperframes/fonts` in that case. Lambda's `/tmp` survives
across invocations on a warm container, so cache hit rate is the same
as non-Lambda runs. Also honor an explicit
`\$HYPERFRAMES_FONT_CACHE_DIR` override for adopters who want a
different location regardless of the runtime.

Surfaced while verifying webm distributed end-to-end on real AWS — the
same bug affects mp4 fixtures using Google Fonts; webm just happened to
be the one I tried first.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* refactor: extract DistributedFormat type + trim font-cache resolver

Second simplify-review pass on the webm stack flagged two cleanups:

1. **`DistributedFormat` type duplicated 10 times.** Every file in the
   distributed pipeline carried its own copy of
   `"mp4" | "mov" | "png-sequence" | "webm"` — adding a new format
   meant a 10-place edit with no compile-time guarantee they stayed in
   sync. Extract a single source of truth in
   `packages/producer/src/services/distributed/shared.ts`, re-export
   from `@hyperframes/producer/distributed` and
   `@hyperframes/aws-lambda/sdk`, and have all callers pull from
   there. The aws-lambda `ALLOWED_FORMATS` runtime tuple and the CLI's
   `FORMATS` tuple now both use `satisfies readonly DistributedFormat[]`
   so the compiler enforces the runtime allowlist stays in sync with
   the type.

2. **`deterministicFonts.ts` font-cache resolver was over-commented.**
   Trim the 7-line block to 4 lines (drop the aspirational
   "and other read-only-FS execution environments" — only Lambda is
   detected — and the warm-container `/tmp` persistence narration —
   anyone reading already knows Lambda /tmp semantics). Collapse the
   two-step `if (explicit && explicit.length > 0)` into a single
   nullish-coalesce expression now that the empty-string defensive
   check is gone (`process.env.X` is `string | undefined`, no third
   shape to guard against).

Out-of-scope skips (called out by the agents, deferred):
- In-process `RenderConfig.format` and the in-process CLI's
  `render.ts` format union still carry their own inline copies. The
  union happens to coincide today but they're separate concerns —
  leaving them alone limits this PR's blast radius.
- `fontCacheDir(slug)` / `resolveFontCacheRoot()` naming asymmetry
  flagged as taste; skipping.
- Pre-existing redundant `existsSync` before `mkdirSync({ recursive:
  true })` in `fontCacheDir` — out of scope.

All tests + typecheck still pass. Lambda render still works
end-to-end (no functional changes).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* docs(lambda): drop plan-doc reference from migration checklist

PR review feedback: source/docs should not mention the
distributed-rendering planning doc. Tighten the migration checklist
sentence to describe the webm path directly rather than referencing
the doc's version label.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* refactor(producer): split resolveEncoderTriple into mp4 + non-mp4 helpers

CI Fallow audit on PR #953 flagged `resolveEncoderTriple` at CRAP 31.6 —
the function interleaved (a) mp4 codec validation + dispatch, (b) the
non-mp4 codec-rejection throw, and (c) per-format dispatch. Splitting
into `resolveMp4EncoderTriple` + `resolveNonMp4EncoderTriple` drops the
top-level function's cyclomatic complexity below the threshold while
preserving every error message and code path. Behavior unchanged.

Also extracts an `EncoderTriple` type alias so the three functions
share the return shape declaratively rather than repeating it.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Make the example library load-bearing in 4 places:

1. SKILL.md — new 'Step -1: Study the Example Library' BEFORE Step 0.
   Mandatory: read examples/README.md + at least 3 scene HTMLs before
   planning. Names which scenes are 'the bars' (04-composed-ui scene 01
   kanban + scene 02 chat). Non-negotiable rule: if you'd reach for a
   product screenshot of an interface as a primary visual, STOP and
   build that UI from divs using the matching example scene.

2. step-3-storyboard.md — Technique-pick checklist after the pacing
   table. Every beat must name 2-4 techniques AND cite the matching
   example scene path. Beats with <2 cited techniques must be redesigned.
   Forbidden: 'show the kanban' as a beat with no scene citation.

3. step-5-build.md — Copy-closest mandate added to the build section.
   Concrete map from beat type to example scene path. Do not write
   any beat from scratch; there is always a closer example.

4. beat-builder-guide.md — Example scene moved to the #1 mandatory
   read for every beat. Sub-agents copy the cited scene's index.html
   to compositions/beat-N-name.html and mutate, not write from scratch.
   Specific call-out: if the beat has narration, also study
   examples/04-composed-ui/scene-02-chat-with-typing — the canonical
   narration-sync pattern (every meaningful phrase = one visual event).

This is the lever HANDOFF Recommendation 2 named: agents pattern-match
to what they study, not to skill prose. With 18 production-grade scenes
in the library and the workflow now requiring agents to copy them as
starting points, the screenshot+Ken-Burns default has somewhere better
to go.

Three concrete bugs found while auditing PR #991:

1. html-in-canvas-patterns.md (#1 in catalog, 3D Rotation with Bloom):
   The code example used `new THREE.EffectComposer(renderer)` UMD-style
   namespace access while the ESM imports right below pull them in as
   bare named imports. Three.js r150+ removed the UMD `examples/js/`
   globals, so as written the example throws `TypeError:
   THREE.EffectComposer is not a constructor`. Switched to the bare
   names matching the imports. THREE.Vector2 stays as-is — Vector2 is
   on the THREE namespace.

2. techniques.md (#5, Lottie Animation): The CDN path
   `@lottiefiles/dotlottie-web/dist/dotlottie-player.js` returns 404.
   `@lottiefiles/dotlottie-web` is the JavaScript SDK, not a web
   component — its `main` is `dist/index.cjs`. The web-component
   package is `@lottiefiles/dotlottie-wc` and the custom element is
   `<dotlottie-wc>`, not `<dotlottie-player>`. Updated both.

3. techniques.md (5 occurrences across Lottie / lottie-web /
   Video / @font-face examples): asset paths used the `../capture/`
   pattern that PR #989's `invalid_capture_path` lint rule emits an
   error for. Replaced all with root-relative `capture/...`. PRs #989
   and #991 are no longer self-contradictory.

Three concrete bugs found while auditing PR #991:

1. html-in-canvas-patterns.md (#1 in catalog, 3D Rotation with Bloom):
   The code example used `new THREE.EffectComposer(renderer)` UMD-style
   namespace access while the ESM imports right below pull them in as
   bare named imports. Three.js r150+ removed the UMD `examples/js/`
   globals, so as written the example throws `TypeError:
   THREE.EffectComposer is not a constructor`. Switched to the bare
   names matching the imports. THREE.Vector2 stays as-is — Vector2 is
   on the THREE namespace.

2. techniques.md (#5, Lottie Animation): The CDN path
   `@lottiefiles/dotlottie-web/dist/dotlottie-player.js` returns 404.
   `@lottiefiles/dotlottie-web` is the JavaScript SDK, not a web
   component — its `main` is `dist/index.cjs`. The web-component
   package is `@lottiefiles/dotlottie-wc` and the custom element is
   `<dotlottie-wc>`, not `<dotlottie-player>`. Updated both.

3. techniques.md (5 occurrences across Lottie / lottie-web /
   Video / @font-face examples): asset paths used the `../capture/`
   pattern that PR #989's `invalid_capture_path` lint rule emits an
   error for. Replaced all with root-relative `capture/...`. PRs #989
   and #991 are no longer self-contradictory.

Three concrete bugs found while auditing PR #991:

1. html-in-canvas-patterns.md (#1 in catalog, 3D Rotation with Bloom):
   The code example used `new THREE.EffectComposer(renderer)` UMD-style
   namespace access while the ESM imports right below pull them in as
   bare named imports. Three.js r150+ removed the UMD `examples/js/`
   globals, so as written the example throws `TypeError:
   THREE.EffectComposer is not a constructor`. Switched to the bare
   names matching the imports. THREE.Vector2 stays as-is — Vector2 is
   on the THREE namespace.

2. techniques.md (#5, Lottie Animation): The CDN path
   `@lottiefiles/dotlottie-web/dist/dotlottie-player.js` returns 404.
   `@lottiefiles/dotlottie-web` is the JavaScript SDK, not a web
   component — its `main` is `dist/index.cjs`. The web-component
   package is `@lottiefiles/dotlottie-wc` and the custom element is
   `<dotlottie-wc>`, not `<dotlottie-player>`. Updated both.

3. techniques.md (5 occurrences across Lottie / lottie-web /
   Video / @font-face examples): asset paths used the `../capture/`
   pattern that PR #989's `invalid_capture_path` lint rule emits an
   error for. Replaced all with root-relative `capture/...`. PRs #989
   and #991 are no longer self-contradictory.