framefields

framefields

Overview

framefields is a code-first video SDK. A video is a TypeScript Composition (a tree of layers with keyframed animation) that renders natively on WebGPU (Dawn) in Node.js, with no browser, Puppeteer, or Chromium. The engine is the framefields npm package; everything below runs in the user's own project.

This skill takes a project from nothing to a verified first render. For anything past that, load the specialist skill:

Task	Skill
Scenes, layout, typography, animation, beat grids, film structure	framefields-compose
Post-processing, color grading, VFX, on-device vision (tracking, cutouts, pose)	framefields-effects
Frame inspection, frame grids, pixel tests, video export and QA	framefields-render
Ready-made components (npx framefields add)	this skill, section 8
Generating images, video, music, voice with AI models (ai)	this skill, section 6
Autonomous agent payments & runway checks	this skill, section 7
Reporting bugs or engine defects to GitHub	this skill, section 9

---

1. Check the environment

• Node.js 22 or later. Run node --version. Older versions fail at import.
• A GPU, or a CPU renderer. macOS uses Metal (every Mac and macOS VM has a Metal GPU). Linux uses Vulkan, Windows Direct3D 12 or Vulkan. Without a GPU, framefields renders on the CPU: on Linux (a sandbox, CI runner or container) through Mesa lavapipe, installed with apt-get install -y libvulkan1 mesa-vulkan-drivers; on Windows through WARP (built into Windows) or lavapipe. Every feature renders the same there (text, media, Lottie, effects, 3D, vision), only slower: about 12× slower than an M1 Pro's GPU in our Linux test. describeGpu() reports software: true. Fine for frames, grids and short exports; for long films, use a GPU machine or the render worker (framefields-render).
• An ES module project. The project's package.json needs "type": "module".

2. Install

Fastest path: npx framefields init. It writes everything in sections 2 and 3 for you: package.json (with the install-script approvals below, scripts, dependencies, packageManager), tsconfig.json, src/theme.ts / film.ts / render.ts, assets/, the LFS .gitattributes and .gitignore. It also downloads Inter and JetBrains Mono (pinned, with their OFL licenses), registers them in the generated src/components/fonts.ts that theme.ts calls, and runs git init.

npx framefields init my-film --install      # a new project; or `init` inside an existing one

In an existing project it never overwrites: existing files are left alone, and package.json, .gitignore and .gitattributes only gain what they lack (a "type": "commonjs" package is refused). Options: --pm npm|pnpm|yarn|bun (default: the one running it), --emoji (also the color emoji font), --no-fonts, --no-git, --name. It asks no questions, so it runs unattended in CI. The AI gateway key is optional: init writes .env.example and git-ignores .env, and render.ts loads .env when it exists; the user sets FRAMEFIELDS_API_KEY there themselves (never write a key for them). Then go to section 4. The rest of this section and section 3 describe what it writes, for doing it by hand or merging into an unusual setup.

Use the package manager the project already uses (look for pnpm-lock.yaml, yarn.lock, bun.lock, or package-lock.json).

Write package.json before installing. npm 11, pnpm 10, and bun block dependency install scripts unless the project approves them, and framefields needs exactly one: skia-canvas downloads its native binary in its install script. Without it, import "framefields" fails with Cannot find module '.../skia.node'. The other packages that ship install scripts work without them, so deny them to keep installs quiet and skip downloads framefields never uses.

For a new project, create package.json with all three blocks. In an existing project, merge them into its package.json, keeping any entries it already has:

{
  "name": "my-film",
  "private": true,
  "type": "module",
  "allowScripts": {
    "skia-canvas": true,
    "sharp": false,
    "webgpu": false,
    "onnxruntime-node": false,
    "node-av": false,
    "esbuild": false,
    "protobufjs": false
  },
  "pnpm": {
    "onlyBuiltDependencies": ["skia-canvas"],
    "ignoredBuiltDependencies": ["sharp", "webgpu", "onnxruntime-node", "node-av", "esbuild", "protobufjs"]
  },
  "trustedDependencies": ["skia-canvas"]
}

allowScripts is read by npm, pnpm by pnpm, and trustedDependencies by bun; each tool ignores the others' fields. Yarn runs install scripts by default and needs none of them. Also add "packageManager" with the exact manager and version you install with (e.g. "[email protected]"), and commit the lockfile the install writes (pnpm, npm or yarn; bun lockfiles can't be rendered by the worker). Then install:

npm install framefields
npm install --save-dev tsx typescript @types/node

The install must finish without an install-scripts warning. If framefields was installed before the approval was in place, add it and rerun the skipped script with npm rebuild skia-canvas (pnpm rebuild skia-canvas). Never approve every script wholesale (npm install-scripts approve --all).

A minimal tsconfig.json:

{
  "compilerOptions": {
    "module": "NodeNext",
    "moduleResolution": "NodeNext",
    "target": "ES2022",
    "strict": true,
    "skipLibCheck": true,
    "noEmit": true,
    "types": ["node"]
  },
  "include": ["src/**/*"]
}

3. Scaffold the project

Keep the composition separate from the script that renders it, so tests, the preview, the render script and the render worker all build the same film. film.ts must only build: no rendering, no process.exit(), no writes at import time.

src/
  theme.ts    # canvas size, fps, colors, fonts: the only place for magic numbers
  film.ts     # buildFilm(): assembles the Composition
  render.ts   # renders frames for review, a live preview, or the full video
assets/
  fonts/      # .ttf / .otf files the film uses
  footage/    # source videos (.mp4, .mov) and audio (.mp3, .wav) tracked in Git LFS
output/       # renders (add to .gitignore)

Text needs a real font file. Ask the user which font to use.

// src/theme.ts
import { FontManager } from "framefields";

export const W = 1920;
export const H = 1080;
export const FPS = 30;
export const INK = "#0E0D0C";
export const PAPER = "#EEE9E0";
export const SANS = "Inter";

export async function registerFonts(): Promise<void> {
  await FontManager.register({ family: SANS, source: "assets/fonts/Inter.ttf" });
}

// src/film.ts
import { Composition, Layer, LayerAnimation } from "framefields";
import { FPS, H, INK, PAPER, registerFonts, SANS, W } from "./theme.js";

const DURATION = 3 * FPS; // frames

export async function buildFilm(): Promise<Composition> {
  // Fonts must be registered before any text layer is built.
  await registerFonts();

  const film = new Composition({
    width: W,
    height: H,
    fps: FPS,
    durationMs: (DURATION / FPS) * 1000,
    backgroundColor: INK,
  });

  film.add(
    Layer.text("Hello, framefields", {
      id: "title",
      position: "absolute",
      x: 0,
      y: H / 2 - 60,
      width: W,
      height: 120,
      fontFamily: SANS,
      fontSize: 96,
      fontWeight: 700,
      fill: PAPER,
      align: "center",
    }).animate(
      LayerAnimation.create()
        .fadeIn(0, 20, "power2.out")
        .fromTo("y", H / 2 - 20, H / 2 - 60, { start: 0, end: 30, ease: "expo.out" }),
    ),
  );

  return film;
}

// src/render.ts
import fs from "node:fs/promises";
import path from "node:path";
import { HeadlessMediaRenderer, startPreview } from "framefields";
import { buildFilm } from "./film.js";

const OUT = path.resolve(import.meta.dirname, "../output");
const [mode = "video", ...args] = process.argv.slice(2);

if (mode === "preview") {
  // The page runs film.ts itself and renders it with WebGPU in the browser.
  const session = await startPreview({ entry: new URL("./film.ts", import.meta.url), export: "buildFilm" });
  console.log(`Preview at ${session.url}`);
  await session.closed; // until its tab closes or the next preview replaces it
  process.exit(0);
}

const film = await buildFilm();
await fs.mkdir(OUT, { recursive: true });

if (mode === "frames") {
  const renderer = new HeadlessMediaRenderer();
  for (const frame of args.map(Number)) {
    const png = await film.renderFrame({ frame, renderer });
    await fs.writeFile(path.join(OUT, `f${String(frame).padStart(4, "0")}.png`), png);
  }
} else if (mode === "grid") {
  const png = await film.renderFrameGrid({
    frames: args.length ? args.map(Number) : [0, 10, 20, 30, 45, 60, 75, 89],
    columns: 4,
    cellWidth: 480,
    showLabels: true,
  });
  await fs.writeFile(path.join(OUT, "grid.png"), png);
} else {
  const result = await film.renderVideo({
    outputPath: path.join(OUT, "output.mp4"),
    quality: "high",
  });
  await result.cleanup?.();
  console.log(`Exported ${result.filePath}`);
}

// Native GPU and encoder threads keep Node alive; always exit explicitly.
process.exit(0);

Add scripts to package.json:

"scripts": {
  "typecheck": "tsc --noEmit -p .",
  "frames": "tsx src/render.ts frames",
  "grid": "tsx src/render.ts grid",
  "preview": "tsx src/render.ts preview",
  "render": "tsx src/render.ts"
}

Video assets & Git LFS

Video inputs (Layer.video("assets/footage/clip.mp4")), Lottie animations (Layer.lottie(...)), audio tracks (Layer.audio(...)), LUTs, and custom fonts belong in Git LFS, while render outputs in output/ belong in .gitignore.

1. Initialize Git LFS:

   git lfs install
   

2. Configure .gitattributes at the project root:

   assets/**/*.mp4 filter=lfs diff=lfs merge=lfs -text
   assets/**/*.mov filter=lfs diff=lfs merge=lfs -text
   assets/**/*.webm filter=lfs diff=lfs merge=lfs -text
   assets/**/*.mp3 filter=lfs diff=lfs merge=lfs -text
   assets/**/*.wav filter=lfs diff=lfs merge=lfs -text
   assets/**/*.cube filter=lfs diff=lfs merge=lfs -text
   assets/**/*.lottie filter=lfs diff=lfs merge=lfs -text
   assets/fonts/**/*.ttf filter=lfs diff=lfs merge=lfs -text
   assets/fonts/**/*.otf filter=lfs diff=lfs merge=lfs -text
   

3. Hydrate pointers before rendering: In freshly cloned or containerized agent environments, LFS media exist as ~130-byte text pointer files. Framefields' native WebGPU and WebCodecs demuxers cannot decode pointers and will fail or produce blank frames. Always ensure pointers are hydrated:

   git lfs pull
   

4. Keep .gitignore targeted: Never add *.mp4 to .gitignore when tracking source footage with LFS. Ignore output directories (output/, scratch/) instead.

4. Verify, cheapest step first

Never go straight to a full video render. On a machine without a GPU every render runs on the CPU (lavapipe or WARP), so the cheap steps matter even more. Each step catches problems in seconds that a video render takes minutes to show:

1. npm run typecheck
2. npm run frames -- 0 30 60 and look at the PNGs in output/. A black frame usually means a missing font, a layer outside the canvas, or opacity stuck at 0.
3. npm run grid and check the motion reads smoothly across the contact sheet.
4. npm run preview when a person is watching: they play the film with sound before you export (see below).
5. npm run render once frames and motion look right. Run it in the background with a long timeout. It logs each phase (Rendered 40% …, Mixing audio, Muxing mp4, Done in …) and a Still … line when one runs long, so a pause after the last frame is the audio mix or mux, not a hang.

Show the user the frame PNGs or the grid before the full render. framefields-render covers pixel-probe tests, render QA (renderVideo({ qa })), and diagnosing blank frames. If you suspect an issue or defect in the engine itself or ai gateway, see section 9.

Live preview

npm run preview serves a localhost player (picture, sound, timeline) and prints its URL. The page runs film.ts itself and renders with WebGPU in real time, so the user sees the real film; a slow device skips frames to keep up with the sound.

• Run it as a background command and read its output: it says when the page opened, prints errors from the page (a failed build, a frame that threw, a missing font), and says why it stopped. It stops 5 s after its last tab closes; just run it again.
• It doesn't open anything. If your app has a built-in browser, open the URL there; otherwise give the user the link. startPreview(..., { open: true }) opens their default browser.
• Reference assets from the file's URL. The page runs film.ts itself, so asset paths must resolve in the browser too: build them from the module's own URL, path.resolve(path.dirname(fileURLToPath(import.meta.url)), "../assets/fonts"), rather than process.cwd() or a bare relative path. The preview serves any file inside the project (the folder with package.json); pass root (one or more paths) to startPreview for fonts or media kept elsewhere.
• After changing the film, run it again. It takes over the same URL, and the open tab reloads by itself at the same moment.
• Link to a moment with #t=12.5 (seconds). In a browser you can script, window.framefieldsPreview has seek(seconds), play(), pause() and state(); seek resolves once the frame is drawn, so screenshot after it.
• The user can pin notes on the picture. Pausing and clicking (or dragging an area) adds a note at that spot and moment. Each one prints in the preview's output and is saved in .framefields/preview-notes/: notes.json, plus note-<id>.jpg, the frame with the spot marked. When the user says they left notes, read notes.json and look at each open note's picture before you edit. Then run the preview again so they can check the changes and tick them off. framefields-render has the details.

5. Render on a server

The framefields render worker (Docker, RunPod pod or serverless) renders a pushed commit: it pulls LFS assets, installs from the lockfile, imports src/film.ts, calls buildFilm, and uploads the result. A project built as above works unchanged if:

• framefields is 2.2+, the lockfile is committed and matches package.json, and packageManager is pinned;
• every input is under assets/, tracked by Git LFS and pushed (git lfs ls-files lists it);
• asset paths come from import.meta.url, never process.cwd();
• nothing writes into node_modules while rendering (files are shared read-only).

A failed job returns { code, hint, retryable }; resubmit unchanged only when retryable is true. Job format and error codes: https://framefields.dev/docs/guides/render-service/

6. Generate assets with AI

Use the connected Framefields MCP server for list_models, get_model_schema, and estimate_generation_cost when available (in Claude Code sessions, these are exposed as mcp__plugin_framefields_framefields__list_models, mcp__plugin_framefields_framefields__get_model_schema, and mcp__plugin_framefields_framefields__estimate_generation_cost). Use import { ai } from "framefields" in a local script to generate, edit, or process media; MCP does not submit or retrieve generation jobs. The SDK authenticates with a separate gateway API key (FRAMEFIELDS_API_KEY), not the MCP OAuth connection. Use only the currently supported catalog models and the input fields from the selected model's schema.

• list_models: inspect catalog models and category tasks (text-to-image, text-to-video, speech-to-text, etc.).
• get_model_schema: check required and optional inputs for the model before writing the script.
• estimate_generation_cost: check published rates or request cost estimates before running paid generation.

framefields exports ai for image, video and audio operations through the Framefields gateway. Each request uses a model ID and account credits. run, subscribe, stream, queue, and storage support the gateway workflow.

import { ai } from "framefields";

const apiKey = process.env.FRAMEFIELDS_API_KEY;
if (!apiKey) throw new Error("Set FRAMEFIELDS_API_KEY before generating assets.");
ai.config({ apiKey });

const { data, requestId } = await ai.subscribe<{ images: { url: string }[] }>("seedream/4.5", {
  input: { prompt: "Neon street at night, rain, 35mm", image_size: "landscape_16_9" },
});
console.log(data.images[0].url);

The key. Requests authenticate with an ff_live_… key from https://framefields.dev/dashboard/keys. For local execution, ask the user to set FRAMEFIELDS_API_KEY in the process environment themselves; never ask them to paste a key into chat. The script reads process.env.FRAMEFIELDS_API_KEY and fails with an actionable message when it is missing. Do not inspect or print environment variables or credential files, embed the key in source, or commit it. AI generation is optional and does not affect local composition and rendering. Without a key, gateway calls cannot run. Failures throw ApiError with the gateway's type: on insufficient_credits (status 402) tell the user to top up at https://framefields.dev/dashboard/billing rather than retrying; key_limit_reached means the key's monthly cap; rate_limited and too_many_inflight_requests mean wait and retry. A ValidationError (422) lists the bad input fields in fieldErrors.

Generate once, into assets/, in its own script. Generation costs money and is not deterministic, so it never runs inside buildFilm(), the preview, tests or the render worker. Write src/generate.ts, run it on purpose, download every output into assets/generated/ (tracked in Git LFS, as above), and reference the local file from the film. Generated output URLs expire, and the worker renders from the repository.

// src/generate.ts
import fs from "node:fs/promises";
import path from "node:path";
import { ai } from "framefields";

const apiKey = process.env.FRAMEFIELDS_API_KEY;
if (!apiKey) throw new Error("Set FRAMEFIELDS_API_KEY before generating assets.");
ai.config({ apiKey });

const OUT = path.resolve(import.meta.dirname, "../assets/generated");
await fs.mkdir(OUT, { recursive: true });

async function save(url: string, name: string): Promise<string> {
  const file = path.join(OUT, name);
  await fs.writeFile(file, Buffer.from(await (await fetch(url)).arrayBuffer()));
  return file;
}

const still = await ai.subscribe<{ images: { url: string }[] }>("seedream/4.5", {
  input: { prompt: "Neon street at night, rain, 35mm", image_size: "landscape_16_9", seed: 7 },
});
await save(still.data.images[0].url, "street.jpg");

// Feed a local file to a model: put a Blob in the input and it is uploaded for you
// (or call ai.storage.upload(blob) yourself and pass the URL).
const image_url = new Blob([await fs.readFile(path.join(OUT, "street.jpg"))], { type: "image/jpeg" });
const clip = await ai.subscribe<{ video: { url: string } }>("seedance/2.0/image-to-video", {
  input: { prompt: "slow push in, rain falling", image_url, duration: "5" },
  logs: true,
  onQueueUpdate: (u) => u.status === "IN_PROGRESS" && u.logs.forEach((l) => console.log(l.message)),
});
await save(clip.data.video.url, "street.mp4");
process.exit(0);

Then Layer.image("assets/generated/street.jpg") / Layer.video("assets/generated/street.mp4") in the film.

• Pick the model and its input from the catalog. https://framefields.dev/models lists every model with its id, category, price per unit and input schema. Each model has its own input and output fields (images[0].url, video.url, audio.url, audio_file.url …): read the schema and pass the output shape as the type argument, or log data once, instead of guessing.
• Long jobs (video, music): subscribe waits and polls. For several at once, ai.queue.submit(model, { input }) each, keep every request_id, then ai.queue.result(model, { requestId }); an interrupted script can collect the results instead of paying again. Reading a status or result is free and retried on transient errors; submitting is never retried, so it can't bill twice.
• Costs: Generation consumes credits. When useful, use the MCP price-estimate tool or the model catalog to report an estimate or unit rate; actual charges can vary. Do not invent a total when only a unit rate is known.
• Pass a fixed seed where the model accepts one, and keep the prompts in generate.ts, so a result can be regenerated.
• Frame-rate and size: generated clips rarely match the composition's fps or aspect. Use fit: "cover" on the layer, and check the clip's real duration before cutting to it.

7. Autonomous agent payments

Coding agents interacting with the AI gateway can discover endpoints, inspect credit runway, and handle top-ups programmatically:

• Manifest discovery: Read GET https://framefields.dev/.well-known/agent-payment.json for live auth schemes, pack amounts, and endpoint paths.
• Runway check: GET https://framefields.dev/api/v1/agent/balance using the FRAMEFIELDS_API_KEY process environment variable as the bearer credential (never print it) returns { balance_usd, held_usd, available_usd }. Query this before expensive generation batches.
• Autonomous 402 flow: When credits are exhausted, the gateway returns HTTP 402 Payment Required with a dynamic Dodo checkout link:

  {
    "status": "payment_required",
    "action_required": {
      "type": "redirect_to_checkout",
      "url": "https://checkout.dodopayments.com/buy/...",
      "instructions": "Pass this URL to your human user to complete authorization."
    }
  }
  

  Pass the URL to the user in chat/terminal to authorize via Dodo Payments.
• On-demand top-up: Alternatively, call POST https://framefields.dev/api/v1/agent/top-up with {"amount": 25} (or 10, 50, 100) to generate a checkout session dynamically.

8. Grow the film

Once the first render works, move to the specialist skills: framefields-compose for splitting the film into scene modules on a beat grid, framefields-effects for grading, grain, and vision-driven effects, and framefields-render for tests and delivery checks. Keep theme.ts as the single source of sizes, colors, fonts, and timing as the project grows.

Ready-made components

framefields has a registry of parametric motion components: a mouse pointer with clicks and drags, a camera that zooms to clicks, window and device frames, word-timed captions, text reveals, counters, annotations, a terminal, code blocks, title cards, lower thirds, meters, chat threads, toasts, callouts, spotlights, confetti, logo reveals, backdrops, audio waveforms, word cycles, touches, before/after splits, selections and card stacks. They are not in the npm package: framefields add copies their source into the project, where it is ordinary project code to read and change.

npx framefields list                            # every component, one line each
npx framefields list --json                     # generated props, dependencies, fonts and examples
npx framefields fonts list --json               # pinned font catalog and configured paths
npx framefields api                             # generated timing/grid/preflight reference
npx framefields add mouse-pointer focus-zoom    # writes src/components/<name>/
npx framefields fonts add emoji                 # color emoji (chat-thread and captions add it themselves)

The generated project also has check (TypeScript plus schema/lint/timeline preflight) and check:render (adds a GPU frame/grid smoke check) scripts. They produce versioned JSON for agents and terminate with a failure code on errors. For a custom entry, use framefields check src/film.ts --export buildFilm --json; add --render to write inspection artifacts under output/check. Keep the builder free of generation, rendering and writes, because preflight imports and executes it.

import { MousePointer } from "./components/mouse-pointer/index.js";

const pointer = MousePointer({
  path: [
    { to: [400, 300], at: 0 },
    { to: [960, 540], at: 30, click: true },
  ],
});
film.add(pointer);
// pointer.cues.clicks[0].frame: key a button press or a sound to the click.

• Before writing a common motion piece by hand, run npx framefields list. A component already handles timing, theme, cues and edge cases, and the copy is the project's to adjust.
• Files go to src/components (or components when there is no src); the folder is saved in framefields.json, and --dir changes it on first use. Components that build on others bring them along (terminal adds app-frame and counter).
• Installed code imports only framefields and framefields/components (the shared toolkit), so it always matches the installed framefields version. After upgrading framefields, npx framefields add <name> --overwrite refreshes a component; without the flag, files you changed are left alone and reported as skipped.
• Fonts come with the components that need them. chat-thread and captions ask for a color emoji font. add downloads Noto Color Emoji (pinned by SHA-256, ~10.7 MB, saved with its OFL license) into assets/fonts/, records it under fonts in framefields.json, and writes src/components/fonts.ts. Call its registerFonts() once before building or rendering, next to the FontManager.register calls. --no-fonts skips the download, npx framefields fonts add emoji installs it later (or for plain Layer.text), and pointing fonts.emoji in framefields.json at another font keeps yours. Track assets/fonts/** with Git LFS.
• Emoji without an emoji font draw nothing. comp.lint() reports missing_emoji_font, and the first render prints the same warning. Fix it with the command above, not by removing the emoji.
• Every component takes the base props (x, y, width, height, at, duration, hold, theme, enter, exit, seed, fps, canvas) and returns a normal box layer with cues (frames of its events), span and parts (inner layers to animate or style). Time is in frames.
• Each installed index.ts documents what the component does at the top and defines its props in its schema; npx framefields list gives one-line summaries. Props are validated when the component is built, and a wrong one throws with the reason.

9. Report engine issues

When you encounter an unexpected crash, native WebGPU / Dawn failure, WGSL shader compilation error, compositor schema validation defect, or behavior bug in framefields itself (distinguishable from project-level configuration or asset errors):

1. Ask the user first: Never open an issue autonomously without explicit confirmation. Explain what went wrong, summarize the reproduction, and ask if they would like an issue reported to gatewai-dev/framefields.
2. Collect diagnostic details:
   • Operating system and architecture (process.platform, process.arch).
   • Node.js version (node --version) and framefields version.
   • GPU backend and device (run describeGpu() or note Metal, Vulkan, DX12, or CPU lavapipe/WARP).
   • Minimal reproduction code (the smallest composition or script that triggers it).
   • Exact error message, full stack trace, or validation failure log.
3. Open the issue: Once the user confirms, submit the issue via GitHub CLI:

   gh issue create --repo gatewai-dev/framefields --title "<concise summary>" --body "<diagnostic details and repro>"
   

   If gh is unavailable or not authenticated in the environment, output the title, formatted body, and a direct link for the user: https://github.com/gatewai-dev/framefields/issues/new.