3 Things React Compiler Won't Auto-Memo: From 512ms Down to 6ms

Originally published at recca0120.github.io "React Compiler auto-memos everything — I don't need manual optimization, right?" That was me six months ago. Then a user reported tab switching was laggy. I opened React DevTools Profiler and recorded a single commit at 512ms . Cold sweat. The project runs React 19 + React Compiler 1.0. In theory, useMemo , useCallback , and React.memo are all automatic. In practice, profile showed compiler missed every hot path. This is my walk through three fixes th