Tools

Vercel's guide to React composition patterns: replaces boolean prop sprawl with compound components, lifted state and clean Context interfaces, including React 19 API changes. Useful for refactoring component libraries and reviewing component architecture.

React and Next.js performance rules from Vercel's engineering team: 70 rules ranked by impact covering request waterfalls, bundle size, server performance and re-renders, for writing, reviewing and refactoring. Maintained by Vercel.

Runs React Doctor via npx to scan React code for security, performance, correctness, accessibility and architecture issues with a 0-100 health score; checks changed code for regressions, and on /doctor fetches the official triage playbook to fix issues.

Audits a whole React codebase read-only: runs a React Doctor scan as evidence, vets findings across bugs, performance, accessibility, security and maintainability, ranks them by leverage, then writes self-contained plans other agents can execute. Never edits source.