trpc

trpc

Routers & Procedures

• t.router({ user: t.procedure.query(...) }) — define API surface.
• Procedures: .query() for reads, .mutation() for writes, .subscription() for real-time events.
• Input validation: t.procedure.input(z.string()).query(...) — auto-inferred types.
• .output(z.object({...})) — validate and type response shape.

Middleware & Context

• t.middleware(async ({ ctx, next }) => { ... return next({ ctx: enriched }) }) — pipeline.
• Context: router.createContext() — per-request initialization (auth, DB, session).
• Per-procedure middleware via .use(middleware) chaining.

Error Handling

• TRPCError — new TRPCError({ code: 'NOT_FOUND', message: '...' }) with typed codes.
• Error formatting: router.formatError(({ shape, error }) => ...) — customize error shape.
• Error filtering by code in client onError callbacks.

React Query Integration

• Auto-generated hooks: trpc.user.useQuery(args), .useMutation(), .useUtils().invalidate().
• SSR: trpcNext.createSSGHelpers() or trpcNext.withTRPC() HOC for Next.js.
• Server-side calls: caller = router.createCaller(ctx) — invoke without HTTP.

Adapters

• HTTP: @trpc/server/adapters/express, @trpc/server/adapters/next, @trpc/server/adapters/fastify.
• Standalone: @trpc/server/adapters/standalone for Node http server.
• AWS Lambda: @trpc/server/adapters/aws-lambda.