Known Errors

edit_item update raw shape:

• Wrong: { "id": "abc", "fromFrame": 30 }
• Right: { "json": "{\"updates\":[{\"id\":\"abc\",\"fromFrame\":30}]}" }
• Use this same updates shape for common moves, trims, and track changes.

edit_item add raw shape:

• The new item goes inside the adds array of the json transaction: { "json": "{\"adds\":[{...}]}" }.
• Use edit_item for simple video placement, for example { "json": "{\"adds\":[{\"type\":\"video\",\"assetId\":\"...\",\"fromFrame\":0}]}" }.

Timeline overlap:

• Error text: Overlap: updated item at ... would overlap existing item at ... on this track.
• Do not force the write or delete the conflicting item silently.
• Retry the edit_item transaction with an explicit available trackId, for example an update containing "trackId":"V2", or ask the user which layer should win.

Workspace path restrictions:

• push_asset on the external MCP only accepts public http(s) URLs as filePath. It rejects local paths, workspace paths, and chat attachment paths.
• For motion-graphic assets, pass the JSX source via create_motion_graphic_from_code({ code:"...", name, width, height, durationInFrames }). push_asset no longer accepts an inline code argument.
• Copying local media into the workspace is not the fix for video/audio/image/GIF imports; use asset-import and import_media instead.
• Use import_media action=create_session, then run the OpenChatCut media import helper once with the returned token for client-held files.

Browser video conversion failure:

• Error text often includes Unable to convert video without dropping audio/video tracks or unknown_source_codec.
• Rerun the OpenChatCut media import helper; it owns frontend-aligned conversion and will surface a user-actionable error if conversion is impossible.
• Do not ask the user to re-import the same file through the editor UI as a workaround — the conversion path is the same, the error will repeat. Fix the source (re-encode locally with ffmpeg) or pick a different file.
• After the replacement asset is uploaded/transcribed, delete the failed original asset if it is unused. The clean final media pool should look like a successful import, not a failed import plus a replacement.

Motion Graphic requirements:

• push_asset(type:"motion-graphic") requires width, height, and duration or durationInFrames.
• MG code must pass the OpenChatCut validator.
• Root AbsoluteFill is not valid for generated MG code; use a scaling root div.
• Avoid declaring a top-level local named scale inside MG code. The validator/runtime may already reserve that identifier; use a specific name such as uiScale.

Local dev Zero caveat:

• When backend runs on a non-default port, use a matching Zero view-syncer configuration.
• In this POC, backend 3010, editor 5177, and view-syncer 4850 are intentionally isolated from the older 3000/5173/4848 stack.

Timeline frame renderer caveat:

• If view_timeline_frames fails for one frame, the project write path can still be healthy — retry with fewer frames or a different time before concluding anything.
• Assets still on blob: placeholders (upload in flight) render as empty; wait for track_progress target=upload before treating a blank frame as a bug.
• Do not report visual proof success unless the tool returns image content that visibly confirms the target frame.