# What is Timeline Studio, and what video editing can it automate?

Timeline Studio is an installable, local-first browser editor for editable AI-assisted video projects. Its portable `.timeline` file is a ZIP archive containing `project.json` and project media, so a human can reopen and continue editing what an Agent produced.

It can assemble a contiguous Visuals track, timed overlays, captions, stickers, voiceovers, separated source audio, and music. The editor includes multilingual browser TTS, Whisper captions, visual transforms, masks, effects, transitions, and offline WebCodecs export with a compatibility fallback.

There are two automation paths:

1. The versioned command runner directly inspects and modifies existing `.timeline` archives. It is transactional, revision-checked, idempotent by operation ID, and supports non-writing project diffs. Its registry covers project/track/clip inspection, timed clip edits, captions, deletion, and source-accurate Visuals trim/split/reorder operations.
2. Browser execution covers AI generation, effects, unsupported editor operations, preview, and rich final rendering. The Skill requires visible-state verification and a reopened editable project. Supported local image, video, and audio imports—and the documented portable headless render subset—can stay on the command path.

An Agent should use the command runner whenever the requested operations are registered and use the browser only for the remaining steps. It must never describe browser automation as deterministic headless execution.

```bash
npm run agent -- project.inspect /projects/product-demo.timeline
npm run agent -- project.diff /projects/update-captions.json
npm run agent -- project.run /projects/update-captions.json
```

See [command-reference.md](command-reference.md) for the exact JSON and [examples.md](examples.md) for complete workflows.