State Handling — React + TanStack Query

<when_to_use>

• Building components that fetch data with useQuery or useSuspenseQuery
• Implementing loading skeletons, error states, or empty states
• Setting up Suspense boundaries (single or parallel)
• Server prefetching with HydrateClient to avoid loading spinners on first paint
• Deduplicating RSC data fetches with React.cache()
• Reviewing mutation forms for proper pending/error handling

NOT for: routing, caching strategies, Server Actions, auth (use nextjs-app-router skill) NOT for: useEffect decisions, React 19 APIs (use react-dev skill)

</when_to_use>

Query State Pattern