remotion-composition-builder

name	remotion-composition-builder
description	Authors or extends a Remotion composition (.tsx) wired to BrandConfig + Storyboard + layout spec + motion. The actual builder skill — runs as a Sonnet-tier worker. Triggered after brand, storyboard, designer, and motion-language outputs are ready. Produces the file under remotion-studio/src/compositions/ and registers it in src/Root.tsx.
automation	automatic
intents	build-composition, write-composition, edit-composition

remotion-composition-builder

The hands. Reads everything else, writes the TSX.

Triggers

• Wave 4 of a remotion-orchestrator plan.
• User asks to "build a composition for {topic}" with brand + storyboard already known.

Inputs

All consumed from prior skill outputs in the same job:

• BrandConfig (from src/brands/{slug}.ts) — runtime + behaviour: voice, voiceover, motion, audience, channel, forbiddenWords
• {slug}.design.md (loaded via loadDesign(slug) from src/brands/loadDesign.ts) — visual tokens: colour, typography, spacing, components, layout, elevation
• Storyboard JSON (from remotion-screen-storyteller)
• Layout spec (from remotion-designer) — references design.md tokens by name
• Motion block (part of BrandConfig)
• Channel spec / aspect ratio (from remotion-marketing-strategist)

See src/brands/CONTRACT.md for the full ownership boundary between BrandConfig and design.md.

Method

1. Locate composition — does src/compositions/{Name}.tsx exist?
   • If yes → patch in place (preserve existing API).
   • If no → create new file using Explainer.tsx as the template.
2. Wire imports — import { brands } from '../brands' for runtime, import { loadDesign, colour, spacing, componentRecipe, typography } from '../design' for visual tokens, motion helpers from ../motion.
3. Define schema — z.object for input props matching the Storyboard shape.
4. Compose scenes — one <Sequence> per storyboard scene. Each scene component reads cfg = brands[props.brand] (for motion/voice/voiceover) AND tokens = loadDesign(props.brand) (for colour/typography/spacing/component recipes), then composes them. Use componentRecipe(tokens, 'cta-primary') to get a fully-resolved CSS-ready object instead of inlining hexes.
5. Audio — wire <Audio src={staticFile(scene.voiceoverAudioPath)} /> per scene if path is set.
6. Register in Root — add or update <Composition id="{Name}" ... /> in src/Root.tsx. durationInFrames = sum(scene.durationSec) * fps.
7. File hygiene — composition file ≤500 lines. Extract scenes to src/compositions/{Name}/scenes/*.tsx if it grows past that.
8. Type check — run npx tsc --noEmit. On red, fix and retry once.

Output

Edited files:

• src/compositions/{Name}.tsx (or scene sub-files)
• src/Root.tsx (registry entry)

Status report to remotion-orchestrator:

{ "composition": "Explainer", "filesChanged": [...], "tscPassed": true, "ready": true }

Boundaries

• Never inline brand values (hex codes, font names, spacing literals) — always read from tokens (visual) or cfg (runtime). See CONTRACT.md for which side owns what.
• Never set durationInFrames without summing storyboard scene durations × fps.
• Never staticFile() an asset path that doesn't exist — fail loud at build, not silent at render.
• Never bypass signatureEntry() for entry motion — keeps motion-language consistent.
• Never duplicate a token across BrandConfig.ts and {slug}.design.md. If the value lives in .design.md, the .ts must not redeclare it.

Reused

• src/compositions/Explainer.tsx — canonical template
• src/motion/index.ts — signatureEntry, brandFadeIn, staggerStart
• src/colour/index.ts — readableOn, brandGradient, contrast
• src/design/index.ts — loadDesign, colour, spacing, typography, componentRecipe, resolveToken
• src/brands/loadDesign.ts — typed loader for {slug}.design.md
• src/brands/CONTRACT.md — BrandConfig ↔ design.md ownership boundary

Hands off to

remotion-render-pipeline to actually render.