Skill UI

Guides preserving React 18 concurrent patterns during migration to React 19 while outlining post-migration adoption of new APIs like use(), Actions, useOptimistic, and Suspense data fetching so concurrent behavior stays intact.

This guide serves as a comprehensive reference for source-file migration patterns required when upgrading to React 19. It details critical API changes, such as updating `ReactDOM.render` to `createRoot().render()`, modernizing ref handling, and adjusting legacy context usage. It is essential for developers migrating large, existing React applications to ensure compatibility with the latest React standards.

Guides React 19 test migrations by outlining act import changes, Simulate-to-fireEvent replacements, full react-dom/test-utils cleanup, and StrictMode call-count verification strategies.