Originally published at recca0120.github.io React Compiler reached 1.0 stable in October 2025 — it auto-applies what useMemo / useCallback / React.memo do by hand. Most tutorials online still teach the old react({ babel: { plugins: [...] } }) form, which no longer works on Vite 8 + @vitejs/plugin-react v6 . v6 made one big change: internal Babel was dropped in favor of oxc . JSX transform and Fast Refresh now run in Rust — much faster, but the tradeoff is that Babel plugins can no longer be passed through react({ babel: {...} }) . To run Babel-based tools like React Compiler, you now need to add @rolldown/plugin-babel separately. This post documents the correct 2026 install flow and how to use React Compiler itself. What React Compiler Actually Does The most tedious part of writing React is sprinkling memoization everywhere . Children re-render, function references change, shallow comparison fails — solved by useMemo / useCallback / React.memo , but knowing when they help is an eyeball exercise.…