[Bug]: edits made while the AI agent is running are overwritten when it answers

[EtienneLescot]

Describe the bug

Edits made in the editor while the AI agent is running are silently lost when the agent's turn finishes.

The chat sends a full document snapshot taken at Send time, the agent folds its edits onto that snapshot in the main process, and the renderer applies the returned document wholesale — setDocument + saveDocument — with no check that the live document has moved in the meantime. Last write wins on a stale base, so every user edit made during the turn (padding, background, a trim, a zoom, a clip move, a title change…) is overwritten on screen and on disk.

Where it happens:

• snapshot at send: LeftPanel.tsx:931 — useProjectStore.getState().document is captured once and passed to chatRun
• agent folds its tools onto that snapshot and returns holder.current (electron/ai-edition/deep-agent/service.ts, DocumentHolder)
• blind apply on return: LeftPanel.tsx:875-880 — applyAgentDocument does store.setDocument(parsed) then store.saveDocument(parsed)

Note this is not the torn-file race DocumentService.writeProject already guards against (that queue makes the two saves sequential and atomic — it just means the agent's stale document is written cleanly on top of the user's).

The one mitigation today is that setDocument pushes the previous document onto the undo stack, so a single Ctrl+Z restores the user's version — but it then throws away the agent's work, and nothing tells the user anything was clobbered.

Expected behavior

A user edit made during an agent turn must not be lost.

At minimum: detect the conflict (the store's revision already increments on every local mutation — capture it alongside the snapshot at send and compare on apply) and tell the user instead of silently overwriting. Better: rebase the agent's tool results onto the current document, or block/queue the conflicting local edit while a turn is in flight.

To Reproduce

1. Open a project in the editor and ask the AI a question that takes a while and edits the document (e.g. "remove the silences").
2. While the agent is still working, change something yourself — e.g. the padding in the inspector, or move a clip.
3. Wait for the agent to answer.
4. The change from step 2 is gone: it's absent from the timeline/inspector and from the saved .openscreen file.

OS

Windows

Additional context

Any of the direct document editors can lose an edit this way (timeline, inspector, transcript editor, captions pane) — they all write to the same projectStore document that the agent's return value replaces.

[github-actions]

Fixed by #309 and merged into main.

This change is assigned to the Next Release release milestone and is not necessarily available in the latest downloadable desktop release yet. It is currently marked as status: pending release until a packaged release containing it is published.