React Render Loop Debugging

Context

Use this skill when a React page keeps re-rendering, refetching, or polling forever after mount or selection changes.

Patterns

1. Trace the full effect chain: useEffect -> callback/hook -> setState -> dependency churn.
2. If a callback is invoked by a mount effect, do not make that callback depend on maps, arrays, or objects that the callback also resets or replaces.
3. Use refs to read the latest mutable collections inside async callbacks when you need current reconciliation data without changing callback identity.
4. Prefer stable IDs/strings in polling and fetch effects over whole selected objects.
5. Check retry toasts and polling callbacks for recursive calls that capture unstable objects.

Examples

• src/aipolicyengine-ui/src/pages/Apis.tsx: loadInitialData originally depended on operationsByApi and also called setOperationsByApi({}), so the mount effect keyed to loadInitialData re-fired continuously.
• Fix pattern: mirror operationsByApi into operationsByApiRef.current and read the ref inside the callback, leaving the callback deps stable.

Anti-Patterns

• useEffect(() => { void loadInitialData() }, [loadInitialData]) when loadInitialData depends on state it also recreates.
• Depending on inline objects/arrays or selected entity objects when only an ID is needed.
• Polling effects that re-arm on every render because status inputs are not stable.