React Compiler

Rule

The compiler memoizes. You do not.

In any React 19+ codebase with the compiler enabled, do not add useMemo, useCallback, or React.memo by default. The compiler handles memoization at finer granularity than a human writes, and adding manual versions is at best noise. This is the most common failure mode in LLM-generated React: the bulk of any agent's React training corpus is pre-compiler, so the default output skews toward manual memoization.

Default behavior when writing React

Write components plainly: