React 19 Development Patterns Overview React 19 patterns for Next.js App Router, Server Actions, optimistic UI, and concurrent features. See Quick Reference for API summary and Examples for copy-paste patterns. When to Use - Building React 19 applications with Next.js App Router - Implementing optimistic UI with or - Creating Server Actions with form validation - Migrating from class components to hooks - Optimizing concurrent rendering with React Compiler - Managing complex state with or custom hooks - Wrapping async operations in Suspense boundaries Quick Reference | Pattern | Hook / API |…