React Modern React

React 19 features and patterns for both vanilla React (Vite, Astro, plain) and Next.js App Router — useActionState, useFormStatus, useOptimistic, useTransition, useDeferredValue, the React Compiler, Suspense + use() for promises, Error Boundaries. Vanilla React 19 features work in any project; Next-specific patterns (Server Components, Server Actions, App Router conventions, metadata API) are clearly separated. Use when working in any React 19+ project to apply current patterns over older ones. Triggers on "React 19", "useActionState", "useFormStatus", "useOptimistic", "useTransition", "useDeferredValue", "React Compiler", "Suspense", "use()", "Server Component", "Server …