React TypeScript Type-safe React = compile-time guarantees = confident refactoring. <when to use - Building typed React components - Implementing generic components - Typing event handlers, forms, refs - Using React 19 features (Actions, Server Components, use()) - Router integration (TanStack Router, React Router) - Custom hooks with proper typing NOT for: non-React TypeScript, vanilla JS React </when to use <react 19 changes React 19 breaking changes require migration. Key patterns: ref as prop - forwardRef deprecated: useActionState - replaces useFormState: use() - unwraps promises/context…