Server

Implement JWT/cookie authentication and authorization in tRPC using createContext for user extraction, t.middleware with opts.next({ ctx }) for context narrowing to non-null user, protectedProcedure base pattern, client-side Authorization headers via httpBatchLink headers(), WebSocket connectionParams, and SSE auth via cookies or EventSource polyfill custom headers.

Set HTTP cache headers on tRPC query responses via responseMeta callback for CDN and browser caching. Configure Cache-Control, s-maxage, stale-while-revalidate. Handle caching with batching and authenticated requests. Avoid caching mutations, errors, and authenticated responses.

Configure input and output validation with .input() and .output() using Zod, Yup, Superstruct, ArkType, Valibot, Effect, or custom validator functions. Chain multiple .input() calls to merge object schemas. Standard Schema protocol support. Output validation returns INTERNAL_SERVER_ERROR on failure.

Create and compose tRPC middleware with t.procedure.use(), extend context via opts.next({ ctx }), build reusable middleware with .concat() and .unstable_pipe(), define base procedures like publicProcedure and authedProcedure. Access raw input with getRawInput(). Logging, timing, OTEL tracing patterns.

Entry point for all tRPC skills. Decision tree routing by task: initTRPC.create(), t.router(), t.procedure, createTRPCClient, adapters, subscriptions, React Query, Next.js, links, middleware, validators, error handling, caching, FormData.

Initialize tRPC with initTRPC.create(), define routers with t.router(), create procedures with .query()/.mutation()/.subscription(), configure context with createContext(), export AppRouter type, merge routers with t.mergeRouters(), lazy-load routers with lazy().

Deploy tRPC on WinterCG-compliant edge runtimes with fetchRequestHandler() from @trpc/server/adapters/fetch. Supports Cloudflare Workers, Deno Deploy, Vercel Edge Runtime, Astro, Remix, SolidStart. FetchCreateContextFnOptions provides req (Request) and resHeaders (Headers) for context creation. The endpoint option must match the URL path prefix where the handler is mounted.

Set up real-time event streams with async generator subscriptions using .subscription(async function*() { yield }). SSE via httpSubscriptionLink is recommended over WebSocket. Use tracked(id, data) from @trpc/server for reconnection recovery with lastEventId. WebSocket via wsLink and createWSClient from @trpc/client, applyWSSHandler from @trpc/server/adapters/ws. Configure SSE ping with initTRPC.create({ sse: { ping: { enabled, intervalMs } } }). AbortSignal via opts.signal for cleanup. splitLink to route subscriptions.

Throw typed errors with TRPCError and error codes (NOT_FOUND, UNAUTHORIZED, BAD_REQUEST, INTERNAL_SERVER_ERROR), configure errorFormatter for client-side Zod error display, handle errors globally with onError callback, map tRPC errors to HTTP status codes with getHTTPStatusCodeFromError().

Mount tRPC as Express middleware with createExpressMiddleware() from @trpc/server/adapters/express. Access Express req/res in createContext via CreateExpressContextOptions. Mount at a path prefix like app.use('/trpc', ...). Avoid global express.json() conflicting with tRPC body parsing for FormData.

Mount tRPC as a Fastify plugin with fastifyTRPCPlugin from @trpc/server/adapters/fastify. Configure prefix, trpcOptions (router, createContext, onError). Enable WebSocket subscriptions with useWSS and @fastify/websocket. Set routerOptions.maxParamLength for batch requests. Requires Fastify v5+. FastifyTRPCPluginOptions for type-safe onError. CreateFastifyContextOptions provides req, res.

Call tRPC procedures directly from server code using t.createCallerFactory() and router.createCaller(context) for integration testing, internal server logic, and custom API endpoints. Catch TRPCError and extract HTTP status with getHTTPStatusCodeFromError(). Error handling via onError option.

Deploy tRPC on AWS Lambda with awsLambdaRequestHandler() from @trpc/server/adapters/aws-lambda for API Gateway v1 (REST, APIGatewayProxyEvent) and v2 (HTTP, APIGatewayProxyEventV2), and Lambda Function URLs. Enable response streaming with awsLambdaStreamingRequestHandler() wrapped in awslambda.streamifyResponse(). CreateAWSLambdaContextOptions provides event and context for context creation.

Mount tRPC on Node.js built-in HTTP server with createHTTPServer() from @trpc/server/adapters/standalone, createHTTPHandler() for custom http.createServer, createHTTP2Handler() for HTTP/2 with TLS. Configure basePath to slice URL prefix, CORS via the cors npm package passed as middleware option. CreateHTTPContextOptions provides req and res for context creation.

Handle FormData, file uploads, Blob, Uint8Array, and ReadableStream inputs in tRPC mutations. Use octetInputParser from @trpc/server/http for binary data. Route non-JSON requests with splitLink and isNonJsonSerializable() from @trpc/client. FormData and binary inputs only work with mutations (POST).

Break a tRPC backend into multiple services with custom routing links that split on the first path segment (op.path.split('.')) to route to different backend service URLs. Define a faux gateway router that merges service routers for the AppRouter type without running them in the same process. Share procedure and router definitions via a server-lib package with a single initTRPC instance. Each service runs its own standalone/Express/Fastify server.