Flowy: compose (author the render timeline)

start_render takes a project — a composition timeline JSON — and turns it into the final video. This skill is that JSON's contract. Full schema + worked example: composition-schema.md. Rendering and polling live in the flowy-render skill.

The model in one breath

Project → Sequence (fps, width×height, duration) → Track[] → Clip[] → MediaSource. Sources hold the media URLs; clips place a source range on the timeline in seconds; tracks stack clips — track index 0 renders TOPMOST. Text is a clip with text config on a "text" source; transparent flam video is a "flam" source keyed at render.

Assembling a film