Dev Tools · 5h ago
Optimistic UI Race Condition Surfaces on Fifth Click
A developer discovered a race condition in React's useOptimistic hook that only appeared after rapidly toggling a checkbox five times. The optimistic UI appeared correct, but overlapping requests caused the server state to diverge from the UI. The fix involves disabling the toggle while a request is pending, similar to form submission guards.
Meridian48 take
This bug is a classic reminder that optimistic UI can mask race conditions, and developers must explicitly handle request deduplication even when the framework makes it look easy.
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The Optimistic UI Race Condition That Only Showed Up on the Fifth Click →
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