fix(whiteboard): stop malformed agent-drawn elements from crashing the board - #953
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lukebrevoort wants to merge 2 commits into
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fix(whiteboard): stop malformed agent-drawn elements from crashing the board#953lukebrevoort wants to merge 2 commits into
lukebrevoort wants to merge 2 commits into
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…e board An agent drew a flow diagram via the whiteboard_update MCP tool and emitted arrows with no `points` array. Excalidraw's restoreElements() calls isInvisiblySmallElement() — which reads `element.points.length` unguarded — before restoreElement() applies its own [[0,0],[width,height]] fallback, so the scene threw "Cannot read properties of undefined (reading 'length')" and took down the whole route. Add sanitizeElements() and apply it in loadWhiteboard and saveWhiteboard, so malformed geometry can neither be persisted nor served. It applies the same fallback Excalidraw itself would, just early enough to matter. Sanitizing on read means boards already holding bad elements render immediately and heal on their next write, with no data migration. Also wrap the whiteboard tab in an error boundary so an unrenderable scene degrades to a message instead of blanking the app, and correct the MCP tool cheat sheet, which listed `points` as optional and told agents not to over-validate. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Summary
Prevent malformed agent-created whiteboard elements from crashing or hanging the whiteboard.
This is the main-repository version of the fix discussed in #857; the fork branch was not modified.
Verification
pnpm run checkpasses.