The attribute is in the HTML schema reference and enforced by the missing_data_no_timeline lint rule, but no page said what omitting it costs: a composition that never registers a GSAP timeline waits out player-ready-timeout (45 s by default) on every render.
That matters for triage because it is a fixed cost. "The render is slow" currently lists only causes that scale with the project - draft quality, media size, filter complexity - so an author whose renders are uniformly 45 s long reads the section, tunes the things it names, and sees no change.
- troubleshooting: add a symptom-keyed entry above "The render is slow", and point that section at it for the constant-penalty case.
- html-schema: give the attribute row the consequence and the lint code.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
* feat(studio): typed audio values, clip fades, audible video drops
Audio rows in the media inspector (Volume, Speed, Media start) take a
typed value: click the readout, type "-6 dB", "1.5x" or "2.5s", Enter.
Speed presets are hidden on <audio> clips.
Clip-edge fades: data-fade-in / data-fade-out in seconds, honoured by the
preview runtime (per-tick gain), the render mixer (afade after volume) and
Studio (Fade in / Fade out rows, and drag dots at the top corners of audio
clips and audible videos). Linear on both sides so preview and render
agree; fades that outrun the clip scale to meet inside it.
Dropped videos with an audio stream now land with data-has-audio="true"
instead of muted, so the mixer keeps their sound. The media metadata
endpoint reports hasAudio from the ffprobe call it already makes.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
* fix(audio): one owner for fades, dB, and afade-after-volume
Illegal fade values become no-fade at fadeGain; typed inspector input
still returns null so the readout stays red. Master and group mixes
share one filter chain with volume then afade. Fade-out stays anchored
to the trimmed clip end.
* fix(studio): share audio helpers and bound typed media values
* fix(studio): reserve sibling fade duration when editing
---------
Co-authored-by: Jake Moran <jakemoran2011@gmail.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>
Co-authored-by: Miguel Angel Simon Sierra <miguel.sierra@heygen.com>
* feat(studio): edit a clip's speed ramp with a rate lane and presets
* fix(studio): keep the live preview attribute in sync with what gets persisted
* fix(cli): snapshot picks the source frame through a rate lane and up to 10x
hyperframes snapshot clamped the constant playback rate at 5 and ignored a
rate lane in data-automation, so a sped-up or ramped clip showed the wrong
frame. It now reads the rate through the runtime's own reader and maps time
with the shared source-time function.
* docs(skills): teach speed ramps as a rate lane in one reference page
Adds the speed-ramps reference, corrects the 0.1 to 5 rate range to 0.1 to 10
and the 'speed ramps are not supported' lines in the skills, and regenerates
the skills manifest.
* docs(skills): say what fixes a ramped clip's length and how the render approximates pitch
* fix(studio): hide the speed preset until the clip has a known duration
A preset on a clip with no data-duration was stretched over a made-up one
second. The panel now offers presets only when the duration is known.
* docs(skills): fix the last stale ramp line in the editing recipes and the slice-cap wording
A new resolver in @hyperframes/parsers decides how long a video, audio or image
occupies the timeline. The core runtime start resolver, clip manifest and clip
tree now read length through it. An image with data-start and no data-duration
gets the dropped-image default of 3 seconds; a bare image stays a static layer.
Video and audio take their length from the file until an authored duration trims it.
The playback rate bound (0.1 to 10) now lives in parsers, and core re-exports it.
A rate lane keeps its own arithmetic in core.
The lint rule that asked images for data-duration is removed, and the docs no
longer say an image requires it.
The runtime absorbed a series of authoring mistakes over time and `runtime/init.ts`
says so in its own comments, but the skills kept teaching the old rules. Four of
them actively cost an agent a failing run: add `crossorigin` (lint rejects it
unconditionally), never build a timeline inside `async` (lint calls that the
documented contract), never `gsap.set` later-scene clips (two fixHints instruct
exactly that), and 12 copyable media snippets with no `id`, which render silent.
Corrected in every place each claim appeared, including `hyperframes-animation`,
three workflow scripts, the scaffolded project instructions, the CLI `docs`
command, and the public docs site: `data-track-index` is a Studio display lane
the render never reads, `class="clip"` is a layout convention rather than a
visibility requirement, timed elements may nest, the visibility window is
half-open, sub-composition host dimensions are backfilled, and the root-fill rule
applies only to the layered-composite path.
Behaviour changes, each backed by a render rather than by reading code:
- `timeline_registry_missing_init` deleted. The runtime creates the registry
before any inline script; a composition without the guard line renders and
animates correctly.
- `video_nested_in_timed_element` kept, message corrected. A rendered repro shows
the nested-with-local-start case really does break, so the rule guards a real
defect, but nothing is "FROZEN": the extractor ignores the wrapper's offset
while visibility uses it, so the clip shows wrong frames and then vanishes.
- `mediaRenderIds` now stamps media whose source is a `<source>` child, closing a
duplicate-id gap the old `[src]`-only selector left open.
- Stale messages fixed on `subcomposition_root_styled_by_class` and
`deprecated_data_layer`.
`coreSkillContent.test.ts` pinned the literal sentence that made root
`data-start` look required, so it is narrowed to structure plus the regression it
genuinely catches.
Not covered, and flagged in the PR: the media global-vs-local start heuristic in
`runtime/init.ts` is the root cause behind the nested-video defect. Removing it
changes the meaning of existing compositions and needs its own deprecation.
- html-schema: the previous clause claimed a composition host's data-media-start is
never read. It is: readElementPlaybackStart (media.ts:16) resolves
data-playback-start ?? data-media-start and timeline.ts calls it on composition
clips. Rewrote to the accurate reason both reviewers gave — composition hosts are
only inspected by the playback-start-first readers, media-start works as a
fallback, but playback-start is what Studio writes/normalises to.
- motion test: pin the HoverVideo click-suppression (preventDefault +
stopPropagation). Removing it left the gate 12/12; now it fails. This is the bug
that escaped static review and only surfaced by driving the live preview.
- replica-compare: fold the visible 'Sound off/on' text into the aria-label so the
accessible name contains it (WCAG 2.5.3, Rames).
Round-5 findings from Magi and Rames.
- replica-compare: the offscreen teardown now resets muted (element + React state),
matching HoverVideo — a pair unmuted before it scrolled away no longer returns
reading 'Sound on' over a paused, sourceless pair (Magi blocker).
- Both controls' aria-labels now follow the mode: under reduced motion the button
plays/pauses the whole comparison, and when a preview is already autoplaying
muted the action is 'unmute', not 'play with sound' (self-review + Rames).
- Hardened the motion-suite assertion to scope 'startBoth' to toggleSound's body
(a defined-but-unused helper no longer satisfies it) and pin the offscreen
muted-reset transition (Rames mutation-test gap).
- html-schema: 'hyperframes validate' inspects <audio> only; note that no
media-start-only reader inspects a composition host, so the kind rule strands
nobody (Rames).
Per Rames: add the engine audio mixer (audioMixer.ts:350 -> ffmpeg -ss) to the
media-start-only readers — it's the live path that makes a lone data-playback-start
a shipped output bug (trimmed picture over untrimmed audio). 'Set one' isn't enough;
give the element-kind rule: <video>/<audio> use data-media-start, nested composition
uses data-playback-start (Studio writes it; it's the child-timeline offset). Also fix
editing-existing-videos.mdx, which offered both names as interchangeable for front
trim of a clip — the exact kind where they aren't.
- replica-compare: the voluntary control now starts and pauses BOTH films (not
just the reference), and the replica-sync effect attaches in view regardless of
the preference, so a reduced-motion visitor who presses play sees the whole
synchronized pair. Added a focused source-level assertion to the motion-check
suite (the repo has no React runtime harness for snippets).
- html-schema: describe each layer precisely instead of grouping the CLI —
timing compiler, HTML parser, producer audio, and 'hyperframes validate' read
only data-media-start; runtime, Studio and 'hyperframes snapshot' read
data-playback-start first (Studio also writes it).
Round-3 findings from Magi.
- edit-operations: dispatch() does not consult can() (session.ts:608 -> applyOp
with no validation; a no-timeline addGsapTween/addLabel is a no-op but a missing
target still writes via selector fallback). Use Rames's wording: call can() first
and skip on failure — no false 'applies nothing' guarantee.
- timing-and-animation: the second E_NO_GSAP_TIMELINE site — gated setGsapTween on
an error it cannot return and called shipped parser code 'a later phase'. Rewrote
to gate addGsapTween (which can return it); dropped the stale can() comment in
types.ts:595.
- html-schema: data-playback-start is read by runtime, Studio and CLI (Studio also
writes it, timelineEditingHelpers.ts); only the compile path is media-start only.
Document the layered precedence instead of calling it runtime-only.
Round-2 findings from Magi (#2/#3/#4) and Rames.
- edit-operations: E_NO_GSAP_TIMELINE is raised only by addGsapTween and addLabel
(mutate.ts:1747), not the set/remove tween ops; drop the false 'dispatch() still
applies structurally' claim (mutate.gsap.test.ts verifies zero patches); add the
requirement to the Labels section where addLabel lives.
- html-schema: data-media-start is read by parser + timing compiler + runtime;
data-playback-start is a runtime-only alias, so a lone playback-start doesn't
shift trim/split. Document the surfaces instead of claiming one universal value.
- testing-local-changes: bun unlink cleanup used a relative cd that resolves under
the video project; use an absolute checkout path.
Flagged by Magi (P1 #2/#3, P2 #7) and Rames.
**`bun unlink hyperframes` does not exist.** Bun answers "error: bun unlink
{packageName} not implemented yet" — I ran it. The command takes no package name;
it unregisters whatever directory you are standing in. The reader arrives at that
block having just been told to cd into a video project, so even the correct form
would unregister the wrong thing and leave the global link in place — which is
exactly the failure the same page's troubleshooting section then explains. The
page created the bug it diagnosed. Now `cd packages/cli && bun unlink`.
**`data-media-start` and `data-playback-start` are one value, not two features.**
The schema page gave them separate rows with different-sounding meanings, so a
reader would reasonably think they compose. Six read sites in core are all
`playbackStart ?? mediaStart` — runtime/media.ts:18 and :92, runtime/init.ts:751,
1993, 2928, 3010. One row now, alias named, and it says which wins.
**Canary rollouts contradicted itself.** Line 109 called enrolment a pure function
of `(feature, installId, percentage)`; line 195 said canaries bucket on a
dedicated `bucketSeed`, not the telemetry id. The second is right —
cli/src/telemetry/canary.ts:98 is `unitId: config.bucketSeed ?? config.anonymousId`.
Also on the Studio shortcuts page earlier: J/Shift+J for keyframe navigation,
Backspace to delete, and Ctrl+Y for redo were all missing.
## Summary
- replace the unsupported `data-var-*` example with the current `data-variable-values` pattern
- document that variable values are carried through but still applied manually inside the nested composition
- add matching reference notes in the data-attributes, HTML schema, core package, and CLI docs
## Verification
- `npx mintlify dev --port 3100`
- browser verification with `agent-browser` on `/concepts/compositions` and `/reference/html-schema`
- proof artifacts saved locally under `tmp/issue-416-docs/`
Major improvements across all 18 pages:
- Use Mintlify components: <Steps> for tutorials, <Tabs> for alternatives,
<CodeGroup> for multi-platform commands, <Tree> for directory structures,
<AccordionGroup> for FAQ/scannable content, <Mermaid> for diagrams
- Add filename annotations to all code blocks (e.g., ```html index.html)
- Add numbered comments inside multi-step code examples
- Show expected terminal output after CLI commands
- Add "When to use" / "When NOT to use" sections to all package pages
- Add "Next Steps" CardGroup to every page (no dead-end pages)
- Cross-link between pages at point of curiosity (not just "see also" dumps)
- Expand thin pages (engine, studio) with architecture details and examples
- Add decision guides (rendering modes, template selection)
- Use <Warning> and <Note> sparingly (max 2-3 per page)
Also adds DOCS_GUIDELINES.md at repo root with writing standards.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
