HyperFrames Core
Agent pitfalls (read first):
- Center with flex/
inset, not CSStransform: translate(-50%,-50%)on a node you then GSAPx/y. Lint:gsap_css_transform_conflict. UsefromToorxPercent/yPercent. - Do not add a scene-exit
tl.set(..., {visibility:"hidden"}). The runtime already hides timed clips. Opacity fades on inner nodes (oropacityon.clip) are enough. Caption hard-kills are a different rule. window.__timelines["id"]must match the rootdata-composition-id.- After
render, read the summary's second line:beginframevsscreenshot, GPU mode, stage timings.screenshot+software gpuon Linux is the slow path.
HyperFrames renders video from HTML. A composition is an HTML file whose DOM declares timing with data-* attributes, whose animation runtime is seekable, and whose media playback is owned by the framework.
This skill is the technical contract — how to build one hyperframes project. The body below is the build guide; per-topic detail lives in references/ (index next), read on demand. Process docs (brief, storyboard, review, production, dispatch, frame-worker) live in /hyperframes → references/. Other concerns live in the sibling domain skills — hyperframes-animation, hyperframes-creative, media-use, hyperframes-cli, hyperframes-registry. The capability map in /hyperframes says what each one covers.
References
| File | Read it to… |
|---|---|
references/minimal-composition.md | start from the smallest renderable composition skeleton |
references/composition-patterns.md | choose monolithic vs modular; structure a modular index.html; pick a sub-comp archetype |
references/data-attributes.md | look up any data-* (root / clip / sub-comp host / legacy aliases); use class="clip" |
references/tracks-and-clips.md | understand what data-track-index does (and does not) control, z-index, time a clip relative to another |
references/creator-editing-recipes.md | copy truthful cut/trim/reorder/retime/freeze/camera/mask/crossfade/audio editing recipes and their limits |
references/sub-compositions.md | wire a sub-composition (host attrs, <template>, per-instance vars) and animate inside it |
references/variables-and-media.md | declare variables; place <video>/<audio>, set volume, trim |
references/determinism-rules.md | build a seekable timeline; determinism bans; layout / text fit |
references/full-screen-motion.md | author full-frame motion with shared backgrounds |
references/tailwind.md | work in a Tailwind v4 project (init --tailwind; runtime contract differs from Studio's v3) |
For animation runtime specifics (GSAP API, Lottie, Three.js, etc.) go to hyperframes-animation → adapters/<runtime>.md.
Building a composition
Two root forms (not interchangeable)
- Standalone (top-level
index.html): root<div data-composition-id="…">sits directly in<body>, no<template>wrapper. Wrapping a standalone root hides all content andlintrejects it (standalone_composition_wrapped_in_template, error). - Sub-composition (loaded via
data-composition-src): wrap the root in<template>. This is the shape to write: the loader also accepts a plain full document and falls back to its<body>, but the templated form is what the examples and tooling assume.
⚠ Transport rule: for a templated sub-composition the assembler drops the file's own
<head><style>/<script>(packages/core/src/compiler/compositionAssembly.ts, thehasTemplategate), so put<style>/<script>inside the template.<link>is hoisted either way. ⚠ Host-id convention: give the host slot, the inner template, and thewindow.__timelines["<id>"]key the same id. A different local id is supported (the assembler falls back to the first root in the file) but the mismatch is silent, so match them unless you have a reason not to.
File shape, host wiring, and the pre-render checklist → references/sub-compositions.md.
Root must be sized (silent layout bug)
The standalone root authors width/height: 100%. Canvas size is data-width/data-height. The runtime stamps those pixels onto the composition root. Do not hardcode 1920px/1080px on #root. Skeleton → references/minimal-composition.md.
One paused timeline
Each composition registers exactly one gsap.timeline({ paused: true }) at window.__timelines["<id>"] (key = root data-composition-id). Building it inside an async callback (document.fonts.ready) is supported; what matters is that you register only after the build completes. Render length is the root's data-duration, not the timeline's length: a timeline that runs past it is cut off, and one that ends early holds its last frame. Omit the root data-duration and the length is inferred instead (timeline, media window, or adapter). You do not need window.__timelines = window.__timelines || {}: the runtime creates the registry before your inline scripts run, and lint no longer asks for it. Don't manually nest sub-timelines into the host; the runtime auto-nests registered child timelines. Full contract (incl. non-GSAP runtimes) → references/determinism-rules.md + hyperframes-animation/adapters/.
First-pass lint gotchas (a guaranteed first build failure)
Rules that lint does catch, but only after the fact. Write them right the first time:
- Never pair a CSS initial
transformwith a GSAP tween on the same property — the CSS value and the tween's start fight andlintrejects it withgsap_css_transform_conflict. Set the initial state inside the tween withgsap.fromTo(el, { x: -40 }, { x: 0 })instead of a CSStransform: translateX(-40px). - Never put
crossoriginon<video>/<audio>.lintrejects it unconditionally withmedia_crossorigin_breaks_preview(error), including for canvas/WebGL/WebAudio readback. There is no suppression. - Never give a
<video data-start>an ancestor that also carriesdata-start.lintrejects it withvideo_nested_in_timed_element(error). Time the wrapper or the video, not both. - Every
<audio>needs anid.lintrejects it withmedia_missing_id, and an id-less<audio>is never picked up by the mixer, so the render is silent. - Never tween a
.clipwithautoAlphaorvisibility—lintrejects it withgsap_animates_clip_element. Animate a child instead. - A named CSS
font-familyneeds an in-file@font-faceto a shipped local file, orlintfiresfont_family_without_font_face. - Sub-composition
#rootuseswidth/height: 100%(orinset: 0), not hardcoded1920px/1080px. Canvas size isdata-width/data-height.
A lint error also switches off the layout and contrast audits: check then reports 0 sample(s) and 0/0 text checks, which reads like a clean file but means nothing ran. Clear lint errors before you trust those numbers.
Non-negotiable rules (silent bugs automated gates may miss)
Surfaced here; full rationale in the linked reference. Do not violate:
- No render-time clocks / unseeded
Math.random/ network / input-state; norepeat: -1(use a finite count). →determinism-rules.md - Never tween
display,visibility, orautoAlphaon a.clipelement. The framework owns clip visibility, andlintrejects it (gsap_animates_clip_element). Animate a child instead. →determinism-rules.md - No
<br>in body text; transformed elements must be block-level + sized; pulsing absolute decoratives need peak clearance. →determinism-rules.md <video>/<audio>are found by a flat document query, so the framework seeks and decodes them at any nesting depth (including inside a sub-comp<template>or wrapper). One hard limit:linterrors if a<video data-start>sits inside another plain element that also hasdata-start, and the failure is real (wrong source frames, then the clip vanishes mid-slot), so put the timing on the wrapper or on the video, never both. Sub-composition hosts are exempt: media inside a sub-composition renders correctly. The other caveat is timelines, not placement: a sub-comp timeline can't animate host-root elements. →variables-and-media.md- Keep every
idunique across the assembled page (prefix sub-comp ids with the composition id,#<id>-hero) so your own#idCSS andgetElementByIdcalls resolve. Frame injection no longer depends on it: the compiler stamps a document-uniquedata-hf-render-idon everyvideo[src]/audio[src]/img[src]. Media that uses<source>children instead of asrcattribute is not stamped, so unique ids still matter there. →composition-patterns.md - A full-screen fill on the composition root is fine on a normal render. It is dropped only on the layered-composite path (HDR content, or a composition using shader transitions), where the engine forces every composition root transparent so the layer beneath shows through. If your composition uses shader transitions or HDR media, put the fill on a full-bleed child (
position:absolute; inset:0). →composition-patterns.md
Editing existing compositions
- Read the files first. Preserve unrelated timing, tracks, IDs, variables, media paths.
- Match existing composition IDs and timeline keys.
- Adding a clip: set its
data-start/data-durationintentionally against the clips around it.data-track-indexis a Studio display lane, not a timing constraint, so it does not need to be free. data-hiddenon any composition element hides it in BOTH preview and render, overriding its time window; it is non-destructive/reversible and toggled by Studio's timeline eye icon.- Adding a sub-composition: verify its internal
data-composition-idbefore wiring the host.
Validation
Use hyperframes-cli for command details
-
npx hyperframes checkpasses (0 findings across lint, runtime, layout, motion, and contrast) - Projects with sub-compositions:
npx hyperframes snapshot --at <midpoints>and eyeball each frame -
npx hyperframes preview --backgroundfor review (the user can edit anything in Studio's timeline, and the server survives the invoking command) -
npx hyperframes renderonly after the user approves