HyperFrames Studio conventions

Studio draws one timeline row per top-level element. A project that follows the rules below opens as a short, readable timeline; one that does not opens as a wall of unlabeled rows the user cannot edit. These are conventions for what to build. For how to change a clip, follow /hyperframes-core references/creator-editing-recipes.md and never invent a different form of the same edit.

1. Every scene is a sub-composition

The root composition holds only timed hosts, media and audio. Any scene with nested structure (a div containing children, a title with a subtitle, a chart) is its own file loaded with data-composition-src, wiring in references/sub-compositions.md.

Nested markup left inside the root does not become a row of its own. It hides inside one opaque row that cannot be trimmed or moved part by part.

Author as if a structure lint rejects any violation.

2. One caption track

• All captions live on one track: a single sub-composition host (one data-track-index) marked data-track-kind="captions" that carries every caption group in order.
• Never one row per caption group, and never captions mixed onto a track with another kind.
• Word-timing rules are unchanged: see /embedded-captions and the caption_* lint rules.

3. One element kind per track

Group by kind so each row is one thing the user can select, mute or drag as a set.

Kind	data-track-kind
Base video / A-roll	video (from the tag)
Scenes, overlays, graphics	graphics
Captions	captions
Audio (voiceover, music, sound effects)	audio (from the tag)

Put data-track-kind on sub-composition hosts. Video and audio kinds come from the tag, so <video> and <audio> need no attribute. Give each kind its own data-track-index; the number is display only; it never changes what renders on top. Use CSS for layering.

4. Safe zones

Any ruler or safe-box overlay lives in the preview pane, never inside the composition, so do not add guide elements to the HTML. Both framings (wide and vertical) use the same two safe boxes, Premiere's defaults. The preview toggle draws them with a tick at the midpoint of every edge. Source: ACTION_SAFE_PERCENT and TITLE_SAFE_PERCENT in packages/studio/src/utils/previewSafeMargins.ts.

Box	Share of the frame	Inset on every edge
Action-safe	90%	5%
Title-safe	80%	10%

• Safe margins: everything visible stays inside the action-safe box (90%), and captions and key content stay inside the title-safe box (80%).
• Two-up and 50/50 layouts keep each half's content inside the title-safe box.

Checking your work

Run hyperframes lint and fix every finding. Then open the project in Studio and check that the timeline shows a base row, one row per scene host, one caption row and the audio rows.