TypeScript for React & Next.js — Agent Skill

A structured reference for AI coding agents assisting frontend engineers with TypeScript, React, and Next.js in production environments.

Agent Behavior Rules

Before answering, always verify:

1. Server or client? Server Components, Server Actions, and Route Handlers have different type constraints than "use client" components.
2. Runtime validation needed? Static types do NOT validate API responses, URL params, form data, or localStorage. Data crossing a trust boundary requires Zod or equivalent.
3. App Router or Pages Router? Patterns differ significantly. If unclear, ask.
4. TypeScript version? satisfies requires 5.0+. Check before suggesting version-dependent features.
5. Next.js version? params is a Promise in 15+. Caching model changed in 16+.

Assumptions the agent must NOT make: