Project/bin/clip/sequence, clipitems with pproTicks-exact source, files by id, nested sequences, generatoritems, transitionitems with alignment, Basic Motion/Opacity/Time Remap/ Audio Levels/Audio Pan filters with keyframes, generic effects by id/name, labels, markers, links, enabled/locked. Golden Premiere-style document and property round trips. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>