React 19 Best Practices Comprehensive performance optimization guide for React 19 applications. Contains 44 rules across 8 categories, prioritized by impact from critical (concurrent rendering, server components) to incremental (component patterns). Covers the React 19.3 stabilizations: , Fragment refs, and direct Context providers in Server Components. Table of Contents 1. Concurrent Rendering — CRITICAL - 1.1 Avoid Suspense Fallback Thrashing — HIGH (prevents flickering, smoother UX) - 1.2 Leverage Automatic Batching for Fewer Renders — HIGH (fewer renders in heavy updates) - 1.3 Use useDef…