jhonny-editor/code/docs/uxp-slide-workflows.md

Guarded track-item slides through stable UXP

slide_track_item_uxp is a bounded documented-UXP composition for a familiar three-item timeline slide: it moves the center clip while trimming only its immediate same-track neighbours to retain both adjacent cuts.

Authority and API boundary

The implementation uses stable Premiere UXP 25.6+ audio/video TrackItem timing getters; createMoveAction, createSetStartAction, createSetEndAction, createSetInPointAction, and createSetOutPointAction; plus Project.lockedAccess and Project.executeTransaction. It does not use CEP, QE, raw evaluation, UI automation, or a native SDK.

Guarded flow

1. Call action: "inspect" for a bounded media type, track index, and center clip index. The command returns the active project/sequence IDs and complete timing/source/speed snapshots for the previous, center, and following clips.
2. Call action: "apply" with that unchanged complete snapshot, confirm_slide: true, a non-zero slide_by_seconds in -60 through 60, and a required operation_id.
3. The panel serializes slides and source-only slips per project/sequence/media track. It re-resolves the complete triplet after entering that tail, rejects every stale field, then creates five documented actions in one transaction: center move, previous timeline/source extension, and following timeline/source trim.
4. It resolves the same coordinates again and verifies each source/timeline endpoint, duration, speed, reverse state, and both contiguous cuts.

Only immediate contiguous forward 1x clip items whose source and timeline durations agree are supported. The requested slide must leave both neighbours with positive source and timeline durations within the documented 0–86,400 second bound. The command neither discovers source handles nor changes clips on other tracks.

Proof boundary

Automated tests exercise closed schemas, complete-triplet stale checks, same-operation replay, one-transaction action composition, post-readback, and deterministic serialization against a concurrent slip. They are mock/static contract evidence only. No licensed Premiere host has validated media handles, linked A/V synchronization, rendered frames, playback, persistence after reopening, or Undo. A verification failure can occur after the host transaction commits; inspect all three items before another edit.