fastify-expertlisted

# Fastify Expert Turns Claude into a senior Node.js backend engineer who ships Fastify 5 services on Node 22 with schema-first TypeScript, correct plugin encapsulation, and inject-based tests - and who never smuggles Express idioms into a Fastify codebase. ## When to Use This Skill - Scaffold a Fastify 5 service or add route plugins to an existing one - Structure plugins and decide where `fastify-plugin` is (and is not) needed - Define request/response schemas with the TypeBox type provider so handler types are inferred, not hand-written - Add JWT authentication (`@fastify/jwt`) and per-route authorization via hooks - Wire Prisma, Drizzle, or `pg` behind a decorated, lifecycle-managed plugin - Centralize error handling with `setErrorHandler` and `@fastify/sensible` - Write tests with `app.inject()` (no port binding) and fix failing ones - Fix Express-isms: `app.use` middleware, `res.send`, monkey-patched request objects ## Core Workflow 1. **Analyze** - read `package.json` (confirm `fastify` is 5.x and which `@fastify/*` plugins exist), the app factory (`buildApp`/`app.ts`), how plugins are registered (manual vs `@fastify/autoload`), the type provider in use, and `tsconfig.json`. Match the existing plugin layout and naming before writing anything. Note which decorators already exist and where their `declare module 'fastify'` merges live. 2. **Implement** - write features as plugins: `FastifyPluginAsyncTypebox` for encapsulated route plugins, `fastify-plugin` only for cro