Miguel Ángel ebd156bcc1 fix: batch GSAP timeline construction to prevent main-thread hang (#1231) (#1249)
* fix: batch GSAP timeline construction to prevent main-thread hang (#1231)

Compositions with thousands of tl.to() calls (e.g. 8,562 in the
reported case) block Chrome's main thread synchronously during HTML
parsing, preventing DOMContentLoaded from firing before Puppeteer's
navigation timeout. This caused render jobs to hang indefinitely at
'Initializing calibration session...' with no error message.

Root cause: GSAP's timeline API is synchronous — each tl.to() call
registers a tween immediately on the main thread. A script with 8k+
calls holds the thread for seconds, starving the browser event loop and
delaying DCL past the navigation timeout window.

Fix: install a property trap on window.gsap in HF_EARLY_STUB (injected
at the top of <head>, before GSAP or user scripts load). When GSAP
assigns itself to window.gsap, the setter intercepts the real gsap
object and wraps gsap.timeline() to return a proxy that queues tween
descriptors (to/from/fromTo/set) instead of calling them synchronously.
A requestAnimationFrame-based flush loop drains 100 tweens per frame,
yielding the main thread between batches so DCL can fire.

When the queue is drained, the stub sets window.__hfTimelinesBuilding =
false and dispatches a 'hf-timelines-built' CustomEvent. init.ts checks
this flag at DOMContentLoaded time; if building is still in progress it
defers bindRootTimelineIfAvailable() until the event fires, then sets
window.__renderReady = true as normal. pollHfReady continues to gate
on both __renderReady and window.__hf.duration > 0, so the render
pipeline does not start until the full timeline is bound.

- Batch size: 100 tweens/rAF tick (empirical; ~4ms/batch at 8k scale)
- Yield mechanism: requestAnimationFrame (cooperative, no setTimeout(0))
- Determinism: 'hf-timelines-built' event guarantees sequencing
- Proxy forwards: pause/seek/totalTime/time/duration/add/paused/
  timeScale/play delegate to the real timeline immediately
- No GSAP package changes; no navigation timeout increase

Fixes #1231

* style: apply oxfmt formatting to producer stub files

* fix(producer): unwrap proxy children in add(), gate setter return on args.length

Addresses two latent correctness concerns from code review:

1. proxy.add() now unwraps __hfReal from any proxy child before passing it
   to the real timeline. GSAP's internal tween graph (_first/_next/_prev
   linkage) requires real timeline instances — proxy objects lack internal
   fields like _dp that GSAP's iteration paths expect.

2. totalTime/time/paused/timeScale now return proxy when called in setter form
   (args.length > 0). Previously these returned the real timeline, causing
   callers who chain .to(...) after a setter call to bypass batching.

Also: build-hf-early-stub.ts now runs oxfmt on the generated output file
so the format check passes in CI on every build.

* fix(producer): gate __hf.duration=0 while GSAP timelines are batching

The HF_BRIDGE_SCRIPT duration getter now returns 0 whenever
window.__hfTimelinesBuilding is true (set by HF_EARLY_STUB while the rAF
batch loop is draining queued tl.to() calls).

pollHfReady in the engine polls until window.__hf.duration > 0, so
returning 0 keeps the engine waiting until the hf-timelines-built event
fires and all tweens are committed to the real GSAP timelines.

Without this gate, normal compositions (style-6, style-13, vignelli)
were being captured mid-batch — the real timelines were empty so GSAP
could not seek them, producing frozen/blank frames in the output video.

* fix(producer): flush GSAP batching under virtual time

* fix(producer): gate render bridge on runtime readiness

* fix(producer): preserve timeline child binding under batching
2026-06-07 09:31:13 -04:00
2026-06-06 20:04:55 +00:00
2026-06-06 20:04:55 +00:00
2026-06-06 20:04:55 +00:00
2026-06-06 20:04:55 +00:00
2026-03-21 22:43:56 -07:00

HyperFrames

npm version npm downloads License Node.js Discord

Write HTML. Render video. Built for agents.

Quickstart | Showcase | Playground | Catalog | Docs | Discord

HyperFrames demo: HTML code on the left transforms into a rendered video on the right

HyperFrames is an open-source framework for turning HTML, CSS, media, and seekable animations into deterministic MP4 videos. Use it locally with the CLI, from AI coding agents with skills, or as the rendering core behind hosted authoring workflows.

Quick Start

With an AI coding agent

Install the HyperFrames skills, then describe the video you want:

npx skills add heygen-com/hyperframes

Try a prompt like:

Using /hyperframes, create a 10-second product intro with a fade-in title, a background video, and subtle background music.

The skills teach agents the HyperFrames production loop: plan the video, write valid HTML, wire seekable animations, add media, lint, preview, and render. They work with Claude Code, Cursor, Gemini CLI, Codex, and other coding agents that support skills.

For visual design handoff workflows, see the Claude Design guide and Open Design guide.

Manually with the CLI

npx hyperframes init my-video
cd my-video
npx hyperframes preview      # preview in browser with live reload
npx hyperframes render       # render to MP4

Requirements: Node.js 22+, FFmpeg

What You Can Build

Need ideas? Browse the Showcase for finished videos you can watch, read, run, and remix.

  • Product launch videos and feature announcements
  • PR walkthroughs with animated code diffs, narration, and captions
  • Data visualizations, chart races, and map animations
  • Social videos with kinetic captions, overlays, and music
  • Docs-to-video, PDF-to-video, and website-to-video explainers
  • Reusable motion graphics for automated content pipelines

Frame.md

frame.md — your design system, ready for video.

Every brand has a design.md. None of them were written for a camera. frame.md is the missing translation layer: it takes your web-context design spec and inverts it for the frame — the same tokens, the same rules, but rewritten so an AI agent can compose a promo video without guessing at scale or reaching for web chrome.

The output is a DESIGN.md superset your whole toolchain can read. Atoms stay sacred. Composition stays free. Numbers come from the script.

Biennale Yellow
Biennale Yellow
BlockFrame
BlockFrame
Blue Professional
Blue Professional
Bold Poster
Bold Poster
Broadside
Broadside
Capsule
Capsule
Cartesian
Cartesian
Cobalt Grid
Cobalt Grid
Coral
Coral
Creative Mode
Creative Mode

Browse and remix them all at hyperframes.dev/design.

How It Works

Define a video as HTML. Add data attributes for timing and tracks. Use GSAP, CSS, Lottie, Three.js, Anime.js, WAAPI, or your own frame adapter for seekable animation.

<div id="stage" data-composition-id="launch" data-start="0" data-width="1920" data-height="1080">
  <video
    class="clip"
    data-start="0"
    data-duration="6"
    data-track-index="0"
    src="intro.mp4"
    muted
    playsinline
  ></video>

  <h1 id="title" class="clip" data-start="1" data-duration="4" data-track-index="1">Launch day</h1>

  <audio
    data-start="0"
    data-duration="6"
    data-track-index="2"
    data-volume="0.5"
    src="music.wav"
  ></audio>

  <script src="https://cdn.jsdelivr.net/npm/gsap@3/dist/gsap.min.js"></script>
  <script>
    const tl = gsap.timeline({ paused: true });
    tl.from("#title", { opacity: 0, y: 40, duration: 0.8 }, 1);
    window.__timelines = window.__timelines || {};
    window.__timelines.launch = tl;
  </script>
</div>

Preview instantly in the browser. Render locally or in Docker. The renderer seeks each frame in headless Chrome and encodes the result with FFmpeg, so the same input produces the same video.

HyperFrames Stack

HyperFrames is the open-source rendering engine, plus a growing set of tools around HTML-native video creation.

Piece Status What it does
CLI Available Scaffold, preview, lint, inspect, and render local video projects
Core / Engine / Producer Available Parse compositions, drive headless Chrome, encode video, and mix audio
Catalog Available Reusable blocks and components for transitions, overlays, captions, charts, maps, and effects
Agent skills Available Teach coding agents the video-production patterns that generic web docs miss
Studio Available, evolving Browser surface for previewing and editing compositions
AWS Lambda rendering Available Deploy a distributed render stack and drive renders from your laptop or CI
hyperframes.dev Available Community playground for previewing, iterating, sharing, and rendering HTML-native video projects
frame.md Available Invert your design system for the camera — a DESIGN.md superset an agent can compose video from

Catalog

Install ready-to-use blocks and components:

npx hyperframes add flash-through-white   # shader transition
npx hyperframes add instagram-follow      # social overlay
npx hyperframes add data-chart            # animated chart

Browse the catalog at hyperframes.heygen.com/catalog.

Why HyperFrames?

  • HTML-native: compositions are HTML files with data attributes. No React requirement, no proprietary timeline format.
  • Agent-friendly: agents already write HTML, and the CLI is non-interactive by default.
  • Deterministic: same input, same frames, same output. Built for CI, regression tests, and automated rendering.
  • No build step: an index.html composition plays as-is and can be previewed directly in the browser.
  • Adapter-based animation: bring GSAP, CSS animations, Lottie, Three.js, Anime.js, WAAPI, or a custom runtime.
  • Open source: Apache 2.0 license, with no per-render fees or commercial-use thresholds.

HyperFrames vs Remotion

HyperFrames is inspired by Remotion. Both tools render video with headless Chrome and FFmpeg. The main difference is the authoring model: Remotion's bet is React components; HyperFrames' bet is plain HTML that humans and agents can both write easily.

HyperFrames Remotion
Authoring HTML + CSS + seekable animation React components
Build step None; index.html plays as-is Bundler required
Agent handoff Plain HTML files JSX / React project
Library-clock animations Seekable, frame-accurate via adapters Wall-clock animation patterns need care
Distributed rendering Local and AWS Lambda render paths Remotion Lambda, mature cloud renderer
License Apache 2.0 Source-available Remotion License

Read the full comparison in the HyperFrames vs Remotion guide.

Documentation

Full documentation: hyperframes.heygen.com/introduction

Packages

Package Description
hyperframes CLI for creating, previewing, linting, and rendering compositions
@hyperframes/core Types, parsers, generators, linter, runtime, and frame adapters
@hyperframes/engine Seekable page-to-video capture engine using Puppeteer and FFmpeg
@hyperframes/producer Full rendering pipeline for capture, encode, and audio mix
@hyperframes/studio Browser-based composition editor UI
@hyperframes/player Embeddable <hyperframes-player> web component
@hyperframes/shader-transitions WebGL shader transitions for compositions
@hyperframes/aws-lambda AWS Lambda SDK and deployment surface for distributed renders

Community

HyperFrames is used in production at HeyGen, with community examples from teams like tldraw, TanStack, and others in ADOPTERS.md. Open a PR if your team is using HyperFrames.

Development Note

The repo uses Git LFS for golden regression-test baselines under packages/producer/tests/**/output.mp4 (about 240 MB of .mp4 files). If you're cloning the full repo for development, install Git LFS first:

# macOS
brew install git-lfs

# Ubuntu / Debian
sudo apt install git-lfs

# Windows
winget install GitHub.GitLFS

# Then, once per machine
git lfs install

If you only need source files, you can skip LFS content:

GIT_LFS_SKIP_SMUDGE=1 git clone https://github.com/heygen-com/hyperframes.git

License

Apache 2.0

S
Description
Write HTML. Render video. Built for agents.
Readme
752 MiB
Languages
JavaScript 56.4%
TypeScript 43.4%