fix: stop background writes clobbering a concurrent user edit - #620
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fix: stop background writes clobbering a concurrent user edit#620My-Denia wants to merge 7 commits into
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`useSequentialTimelineOps` exists because every timeline edit is a read-modify-write of the whole document, and its header says so: anything that reads the doc and saves it back belongs on that chain. The `loadedmetadata` handler did neither -- it read `getState().document` and issued its own save. That is enough to lose an edit, because the store is only written once the bridge answers. A user's save in flight leaves `getState()` returning the PRE-edit document, the probe builds a full snapshot from it, and whichever write lands second wins. The epoch check in `saveDocument` does not cover this: it guards undo, redo and project switches, not a concurrent save. Move the read, the compute and the write inside `enqueueTimelineWrite`, which the shell already holds, and await the saves so the queue actually waits for them -- a fire-and-forget write would let the next queued edit read a document this one has not committed yet.
Its `add*` siblings compute and save in the same tick, so reading the render closure is harmless there. This one is different: the wand captures the callback, awaits a multi-second cursor-telemetry IPC, and only then calls it. Anything the user commits during that wait is in the store but not in the closure, so the snapshot written back is missing their edit -- and it was also anchoring the new regions against clips that may no longer exist. Read from the store inside the callback, and anchor against that same document, matching `applyClipEdit`, `setTrimEntries` and `insertClipAt` -- which is also what lets this compose with `useSequentialTimelineOps` instead of racing it. The test captures the callback before the store moves, the way the wand does, and fails against the closure read: the saved document comes back carrying the old title, with the user's edit gone.
Putting the write on the queue fixed one race and opened a narrower one: there is now real time between the metadata event and the write, and the duration in hand came off the video that fired the event. Two ways it can land somewhere it does not belong. Across projects: switch while the task is queued and the document read inside it is the new project, which gets the old video's length. `saveDocument`'s epoch check cannot see this -- the write is issued after the switch, not across it. So the event is bound to the project that was open when it fired, and dropped if that is no longer the one loaded. Within one project: the seed branch stamps the duration on the primary asset and sizes the clip from it, and `replaceTimeline` hard-codes clips to that same primary asset -- so an event from any OTHER asset seeds one video's length under another's id. Pre-existing, but the queue delay is what makes a primary change between the event and the write reachable at all. Seed only when the asset that fired is the one the seed is about; the primary's own event does its own seeding. The sibling branch needed neither guard: `applyProbedDuration` is handed the asset id and returns the document untouched when it does not hold it.
The two guards in the previous commit shipped untested, on the argument that the `loadedmetadata` path has no component harness. That confused "cannot test the component" with "cannot test the behaviour": the decision is pure -- a document, an asset id, a duration and the project the event came from -- and only the queueing around it needs the component. So the decision moves to an exported `documentAfterProbedDuration` and the handler keeps the wiring. Both guards now fail their tests when removed: without the project binding a switched-to project takes the old video's length, and without the asset check a non-primary asset seeds a clip that `replaceTimeline` pins to the primary. The seed, the fold-in and the already-settled cases are covered too. Two `saveDocument` call sites became one, so the write-audit table loses a row.
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Included review availability: Your plan provides up to 8 included reviews per hour; 6 remain after this review. 📝 WalkthroughWalkthroughThe change centralizes probed-duration updates, selects the primary asset for empty-timeline previews, and queues metadata persistence against the current document. Bulk zoom creation now reads current store state after telemetry waits, with regression coverage for concurrent edits. ChangesTimeline consistency
Estimated code review effort: 3 (Moderate) | ~25 minutes Merge Risk: ⚪ Minimal · up to This change prevents background duration and bulk-zoom updates from overwriting newer timeline edits and selects the intended primary asset for empty timelines. The covered guards and persistence behavior leave no identified merge-blocking risk. Sequence Diagram(s)sequenceDiagram
participant handleLoadedMetadata
participant enqueueTimelineWrite
participant documentAfterProbedDuration
participant saveDocument
handleLoadedMetadata->>enqueueTimelineWrite: enqueue loaded duration
enqueueTimelineWrite->>documentAfterProbedDuration: transform current document
documentAfterProbedDuration-->>enqueueTimelineWrite: updated document or null
enqueueTimelineWrite->>saveDocument: persist effective document
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✅ Passed checks (4 passed)
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In `@src/components/ai-edition/NewEditorShell.probedDuration.test.tsx`:
- Line 1: Remove the `@vitest-environment` jsdom directive from the
documentAfterProbedDuration test so it runs in Vitest’s default Node
environment; leave the test behavior unchanged.
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src/components/ai-edition/NewEditorShell.probedDuration.test.tsxsrc/components/ai-edition/NewEditorShell.tsxsrc/lib/ai-edition/store/documentWriteAudit.test.tssrc/lib/ai-edition/store/useTimeline.test.tssrc/lib/ai-edition/store/useTimeline.ts
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- src/lib/ai-edition/store/documentWriteAudit.test.ts
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With no clips to follow, the preview fell back to the whole asset list and VirtualPreview mounted index 0 — `document.assets[0]`, which is not always the primary. `handleLoadedMetadata` seeds the first clip against `primaryAssetId ?? assets[0]` and, since the guard added here earlier, ignores an event from any other asset. So the two disagreed exactly when they had to agree: the mounted asset fired an event the seed refused, nothing else was ever mounted (the index only moves for clips, and there are none), and the timeline stayed empty for good. A project whose first import is audio is that case. Audio never claims the empty primary slot (document-service.addAsset), so `assets[0]` is the audio track and the primary is the video added after it. The empty-timeline fallback now mounts the resolved primary instead, and keeps the old whole-list behaviour when that id resolves to nothing, so a stale primary cannot leave the stage with no source at all.
The file opts into jsdom but never touches the DOM: it calls `documentAfterProbedDuration` directly and asserts on the document it returns. vitest.config.ts makes `node` the default for exactly this reason and the docblock is the opt-in — 972ms of environment setup here bought nothing.
This was referenced Sep 7, 2026
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Summary
Two background paths read the document, build a whole-document snapshot and save it, so whatever the user committed in between is dropped.
The window is real because the store is only written once the bridge answers. While a user's save is in flight,
useProjectStore.getState().documentstill returns the pre-edit document; a task that reads it and saves a snapshot built from it lands second and takes their edit with it.saveDocument's epoch check does not cover this —currentWriteEpochchanges on undo, redo and project switch, not on a concurrent save.loadedmetadataprobe now folds its duration in on the shared write queue, reading the document inside the task and awaiting the save.useSequentialTimelineOpsexists for exactly this, and says so: "every timeline edit is a read-modify-write of the whole document ... Anything that reads the doc and saves it back belongs here."addZoomsBulknow reads the document at write time instead of off the render closure, and anchors the new regions against that same document. Itsadd*siblings compute and save in the same tick; this one is reached from the wand only after a multi-second cursor-telemetry IPC, so its closure is stale by seconds rather than by a render.replaceTimelinepins every clip it builds to the primary asset, so an event from any other asset would write one video's length under another's id.videoSources[sourceIndex], index 0 while no clip moves it), so guarding the seed alone would leave the mounted asset firing an event the seed refuses and the timeline empty for good. The whole-list fallback stays for a primary id that resolves to nothing.Related issue
None. Both turned up while reviewing #619, and neither was introduced there, so they are here rather than folded into it.
Type of change
Release impact
Desktop impact
Screenshots / video
Nothing visible changes on the ordinary path. What changes is which document reaches disk when two writes overlap, and — for a project whose first asset is not its primary — which asset the preview mounts while the timeline is still empty.
Testing
addZoomsBulkhas a regression test that captures the callback before the store moves, the way the wand does. Against the old closure read it fails by reproducing the defect: the saved document comes back carrying the pre-edit title, with the user's edit gone.The probe's decision moved out of the component into an exported
documentAfterProbedDurationso it could be tested at all — the event reaches the shell through Preview, PreviewCanvas, VirtualPreview and a real<video>decoding real media, which no test environment here provides. Both of its guards fail their tests when removed, and the seed, the fold-in and the already-settled cases are covered too.Collapsing the handler's two
saveDocumentcalls into one changed the write topology, whichdocumentWriteAudit.test.tscaught until its table was updated.npx tsc --noEmit,npx tsc -p tsconfig.test.json --noEmitandnpm run lintare clean. The full suite passes.Driven on a real machine as well, because the riskiest edit here is a guard that can suppress the timeline seed — an editor opening with no clip is exactly what that seed exists to prevent. A HUD recording on Windows opened in the editor with the probed length folded in: one clip at 0–26.517 s against an asset reporting 26.516667 s, bound to the primary asset. Auto enhance then wrote four
focusMode: autoregions onto that same project with the clip and its duration unchanged.The case the guard needs the preview for was driven too, since it is the one the ordinary recording flow never reaches. A project holding a 5.000 s audio asset first and a 26.516667 s recording as its primary, with an empty timeline, opened against a real
<video>: with the guard alone the mounted source is the audio and no clip is ever seeded; with the preview change the mounted source is the recording and the seed writes one clip at 0–26.516667 s on it. The ordinary single-video project seeds the same clip either way.Scope
This does not give the editor general concurrency control over document writes, and it should not be read as if it did.
enqueueTimelineWriteonly coordinates writes that go through it, and most callers reachsaveDocumentdirectly —handleRenameProjectamong them. So two concurrent read-modify-write saves in the same project can still overwrite each other, and nothing here changes that.Closing that properly means either a shared read-modify-write coordinator every caller goes through, or version-conditional writes at the persistence layer. Two cheaper things do not work and were tried on paper first: a revision check before the bridge call adds nothing, because a save that already landed is visible to the read inside the queued task anyway; and one after the await keeps the store right while leaving the losing document on disk, since the bytes are written by then. Serialising sends inside
saveDocumentdoes not help either, because the defect is in when each caller read, not in what order they sent.What this change does is narrow the two paths where the read and the write are separated by a multi-second await, which is where the window is wide enough to lose an edit in ordinary use rather than by interleaving.