How to setup Next App Router + Clerk + TRPC

route.ts

// TRPC API endpoint
// src/app/api/trpc/[trpc]/route.ts

import { fetchRequestHandler } from "@trpc/server/adapters/fetch";
import { type NextRequest } from "next/server";

import { env } from "~/env";
import { appRouter } from "~/server/api/root";
import { createTRPCContext } from "~/server/api/trpc";
import { getAuth } from "@clerk/nextjs/server";

/**
 * This wraps the `createTRPCContext` helper and provides the required context for the tRPC API when
 * handling a HTTP request (e.g. when you make requests from Client Components).
 */

const createContext = async (req: NextRequest) => {
  return createTRPCContext({
    headers: req.headers,
    auth: getAuth(req),
  });
};

const handler = (req: NextRequest) =>
  fetchRequestHandler({
    endpoint: "/api/trpc",
    req,
    router: appRouter,
    createContext: () => createContext(req),
    onError:
      env.NODE_ENV === "development"
        ? ({ path, error }) => {
            console.error(
              `❌ tRPC failed on ${path ?? "<no-path>"}: ${error.message}`,
            );
          }
        : undefined,
  });

export { handler as GET, handler as POST };

server.ts

// TRPC Proxy for server side usage
// src/trpc/server.ts

import "server-only";

import {
  createTRPCProxyClient,
  loggerLink,
  TRPCClientError,
} from "@trpc/client";
import { callProcedure } from "@trpc/server";
import { observable } from "@trpc/server/observable";
import { type TRPCErrorResponse } from "@trpc/server/rpc";
import { cookies, headers } from "next/headers";
import { NextRequest } from "next/server";
import { cache } from "react";
import { appRouter, type AppRouter } from "~/server/api/root";
import { createTRPCContext } from "~/server/api/trpc";
import { transformer } from "./shared";
import { getAuth } from "@clerk/nextjs/server";

/**
 * This wraps the `createTRPCContext` helper and provides the required context for the tRPC API when
 * handling a tRPC call from a React Server Component.
 */
const createContext = cache(() => {
  return createTRPCContext({
    headers: new Headers({
      cookie: cookies().toString(),
      "x-trpc-source": "rsc",
    }),
    auth: getAuth(
      new NextRequest("https://notused.com", { headers: headers() }),
    ),
  });
});

export const api = createTRPCProxyClient<AppRouter>({
  transformer,
  links: [
    loggerLink({
      enabled: (op) =>
        process.env.NODE_ENV === "development" ||
        (op.direction === "down" && op.result instanceof Error),
    }),
    /**
     * Custom RSC link that lets us invoke procedures without using http requests. Since Server
     * Components always run on the server, we can just call the procedure as a function.
     */
    () =>
      ({ op }) =>
        observable((observer) => {
          createContext()
            .then((ctx) => {
              return callProcedure({
                procedures: appRouter._def.procedures,
                path: op.path,
                rawInput: op.input,
                ctx,
                type: op.type,
              });
            })
            .then((data) => {
              observer.next({ result: { data } });
              observer.complete();
            })
            .catch((cause: TRPCErrorResponse) => {
              observer.error(TRPCClientError.from(cause));
            });
        }),
  ],
});

trpc.ts

// TRPC server response
// src/server/api/trpc.ts

/**
 * YOU PROBABLY DON'T NEED TO EDIT THIS FILE, UNLESS:
 * 1. You want to modify request context (see Part 1).
 * 2. You want to create a new middleware or type of procedure (see Part 3).
 *
 * TL;DR - This is where all the tRPC server stuff is created and plugged in. The pieces you will
 * need to use are documented accordingly near the end.
 */
import { initTRPC, TRPCError } from "@trpc/server";
import superjson from "superjson";
import { ZodError } from "zod";

import { db } from "~/server/db";
import { type getAuth } from "@clerk/nextjs/server";

type AuthObject = ReturnType<typeof getAuth>;

/**
 * 1. CONTEXT
 *
 * This section defines the "contexts" that are available in the backend API.
 *
 * These allow you to access things when processing a request, like the database, the session, etc.
 *
 * This helper generates the "internals" for a tRPC context. The API handler and RSC clients each
 * wrap this and provides the required context.
 *
 * @see https://trpc.io/docs/server/context
 */
export const createTRPCContext = async (opts: {
  headers: Headers;
  auth: AuthObject;
}) => {
  return {
    db,
    userId: opts.auth.userId,
    ...opts,
  };
};

/**
 * 2. INITIALIZATION
 *
 * This is where the tRPC API is initialized, connecting the context and transformer. We also parse
 * ZodErrors so that you get typesafety on the frontend if your procedure fails due to validation
 * errors on the backend.
 */
const t = initTRPC.context<typeof createTRPCContext>().create({
  transformer: superjson,
  errorFormatter({ shape, error }) {
    return {
      ...shape,
      data: {
        ...shape.data,
        zodError:
          error.cause instanceof ZodError ? error.cause.flatten() : null,
      },
    };
  },
});

/**
 * 3. ROUTER & PROCEDURE (THE IMPORTANT BIT)
 *
 * These are the pieces you use to build your tRPC API. You should import these a lot in the
 * "/src/server/api/routers" directory.
 */

/**
 * This is how you create new routers and sub-routers in your tRPC API.
 *
 * @see https://trpc.io/docs/router
 */
export const createTRPCRouter = t.router;

/**
 * Public (unauthenticated) procedure
 *
 * This is the base piece you use to build new queries and mutations on your tRPC API. It does not
 * guarantee that a user querying is authorized, but you can still access user session data if they
 * are logged in.
 */
export const publicProcedure = t.procedure;

/** Reusable middleware that enforces users are logged in before running the procedure. */
const enforceUserIsAuthed = t.middleware(({ ctx, next }) => {
  if (!ctx.userId) {
    throw new TRPCError({ code: "UNAUTHORIZED" });
  }
  // Make ctx.userId non-nullable in protected procedures
  return next({ ctx: { userId: ctx.userId } });
});

/**
 * Protected (authenticated) procedure
 *
 * If you want a query or mutation to ONLY be accessible to logged in users, use this. It verifies
 * the session is valid and guarantees `ctx.session.user` is not null.
 *
 * @see https://trpc.io/docs/procedures
 */
export const protectedProcedure = t.procedure.use(enforceUserIsAuthed);

Thank you. This solved hours of searching and trying.

got this "Object literal may only specify known properties, and 'auth' does not exist in type '{ headers: Headers; }'.ts(2353)"

Is this solution "production-ready" @mkcode?
I'm asking because I'm not sure about this part.

    auth: getAuth(
      new NextRequest("https://notused.com", { headers: headers() }),
    ),

Is this solution "production-ready" @mkcode? I'm asking because I'm not sure about this part.

    auth: getAuth(
      new NextRequest("https://notused.com", { headers: headers() }),
    ),

Have you been able to find alternate solution to this ?