Papercut build

Build every episode on the library instead of writing a Remotion project from scratch. Read library/README.md once.

Preflight

• Install: Standard or Full. Needs the library, node 20+, npm, ffmpeg, Python tools (numpy, Pillow, soundfile) and Chrome or Chromium for the audio render. Probe with the commands in papercut-explainer; if something is missing, run ./install.sh --doctor and hand over to papercut-setup.
• Library: $PAPERCUT_LIB, else the PAPERCUT_LIB= line in ~/.config/papercut-explainer/config.env, else ask once. With no library at all, build from the sketches in ../papercut-explainer/references/remotion-recipes.md.
• Load the Remotion best-practices skill first (remotion-best-practices, from the Remotion plugin, or npx skills add remotion-dev/skills -g -y -a <your harness id>; install.sh --mode standard does this) and follow its routing for markup, captions and the Studio.
• Needs papercut/STORYBOARD.md and narration/script.json from the earlier stages.
• Smoke test of the whole toolchain: library/tools/selftest.sh builds examples/hello-reel/ in a throwaway folder and renders one still.

1. Scaffold

$PAPERCUT_LIB/new_episode.sh <series-dir> NN-slug CompId [out-name]

It creates <series>/episodes/NN-slug/{research,narration/voice,papercut} with the template project and a synced copy of the kit in src/lib/. node_modules comes from $DONOR, else the newest sibling episode, else npm i. If <series>/papercut-assets/ exists, it is laid over the default textures and props.

The folder may already exist, because the earlier stages wrote research/, narration/script.json and papercut/STORYBOARD.md into it. The script merges into it and never overwrites a file that is there. It stops only if papercut/package.json exists (already scaffolded).

Never edit src/lib/ in a project. It is a snapshot, so an old episode renders the same after the library changes. Fix the library, then re-sync with papercut/sync_kit.sh.

2. Plan: episode.json, voice, timing

From the storyboard, fill papercut/episode.json:

• scenes: [["S01Hook", "l1_hook", 0], ["S02Name", "l2_name", "called"], ...] (scene id, narration line id, first word as an index or the exact word).
• banners: {"S01Hook": "TAKEAWAY IN CAPS"}. hook: see papercut-hook. cuts: the Camera / Cut table's cut column. bed, whipScene, cutSfx, gaps (extra beat after a line, in seconds).

Then run papercut-voice through its timing step (it ends with build_vo.py and timing_md.py). Then, from papercut/:

python3 $PAPERCUT_LIB/papercut/stubs.py        # src/scenes/index.ts + a stub per scene

build_vo.py flags any scene under 1.2 s; merge it into a neighbour. timing_md.py writes the Timing section of STORYBOARD.md (absolute frames and word cues), so agents never open plan.json.

3. Assets

Follow ../papercut-explainer/references/asset-prompts.md: an image tool (anything that outputs transparent PNGs) for backgrounds and complex static props, code for characters, all text, tags, gauges, buttons and UI. No text inside generated images. With no image tool, build every prop in code with the paper filter; the style holds up. Backdrops: use the library's <Backdrop> set (library/papercut/public/bg/backdrops/_sheet.jpg); generate a new one only when an episode needs a place the library lacks. The proof screenshot: node $PAPERCUT_LIB/tools/capture.mjs <url> public/proof/x.png, shown with the kit's RealShot.

4. Scenes

1. Build S01Hook yourself first, from the HOOK block. It is the reference scene the agents match (cue constants, the camera, clamped interpolate).
2. Hand the rest to scene agents in parallel, grouped by scene (2-3 scenes each; more agents cost more startup context). Use the papercut-scene agent that install.sh wrote for your harness (Claude Code ~/.claude/agents, OpenCode ~/.config/opencode/agents, Codex ~/.codex/agents, Gemini CLI ~/.gemini/agents); a general agent also works. Spawn it with your harness's own mechanism (the Task tool in Claude Code, the subagent tool in opencode, Codex's subagents, Gemini's agent tool). If your harness has no subagents, build the scenes yourself one at a time, in the same order and with the same brief; it is slower, not different. The brief is library/papercut/AGENT_BRIEF.md. The spawn message gives the project path, each agent's scenes with absolute frame ranges, a QA folder name and the value of $PAPERCUT_LIB.
3. File ownership: an agent writes only src/scenes/<Scene>.tsx, an optional <Scene>.parts.tsx and tools/cue_sheet.d/<Scene>.json. Never src/lib/**, other scenes, index.ts, plan.json, episode.json or the storyboard.
4. Agents read library/papercut/CATALOG.md and library/audio/CATALOG.md, not the kit source, and reuse components, prop sets and scene templates (kit/scenes/, for example CtaPhoneDM for the CTA) before drawing anything new.

Build rules: 1080x1920, 30 fps, scenes chained in the kit's transition series. Global layers: VO and music <Audio>, the taped banner with <Boil>, <WordTagCaptions>, <GrainOverlay>. Every prop is wrapped in <Paper>, entrances use <PopIn>, each scene runs inside its storyboard camera. No CSS animations. Keep the bottom 20% clear. Neighbouring scenes never share a backdrop. The default hero is a boxy orange critter (token C.hero #D67354, shade C.heroLo #A9553B, alias you); accessories and name pills tell the cast apart.

5. Sound

Pick SFX by name from library/audio/sfx/*.js and the bed by preset from library/audio/beds/*.json. From papercut/:

python3 $PAPERCUT_LIB/tools/cues.py && node $PAPERCUT_LIB/audio/render.mjs

cues.py merges the agents' rows into tools/cues.json and prints a note if air sounds exceed one per 2.5 s. render.mjs writes public/audio/music.wav and fx.wav.

6. Render

Preview in the Studio (npx remotion studio). Render only when asked:

$PAPERCUT_LIB/tools/render.sh        # -> out/<out>.mp4

Flags: --workers N (default 3), --conc N, --force, --keep. Each scene is cached, so after a fix only the changed scene re-renders; a change to the kit, plan, voice or captions re-renders everything. The first run downloads Remotion's headless Chrome, and out/cache takes several GB of ProRes.

To fix or rebuild one scene: edit src/scenes/<Scene>.tsx, check it with papercut-qa, then run render.sh again.

7. Harvest (after the episode)

python3 $PAPERCUT_LIB/tools/harvest.py .       # from papercut/; read-only report
python3 $PAPERCUT_LIB/tools/catalog.py         # regenerate both catalogs

Promote kit fixes, reusable components, new SFX and recurring beats as library/HARVEST.md describes, and add an entry to library/CHANGELOG.md.

• When a move looks stiff or muddy, check ../papercut-explainer/references/motion-principles.md for the matching principle and its kit helper.

Hand-off

Next is papercut-qa, which reads stills from the project and STORYBOARD.md. Run it per scene while building and once on the whole reel before the final render. After posting, papercut-strategy runs the autopsy.