Error: Tried to access "$types.__endpoint" which is not available at runtime

Error: Tried to access "$types.__endpoint" which is not available at runtime
    at [blah]/functions/node_modules/@trpc/core/dist/index.js:344:23

import { initTRPC } from "@trpc/server";
import { CreateExpressContextOptions } from "@trpc/server/adapters/express";

export const createContext = ({ }: CreateExpressContextOptions) => ({});
type Context = Awaited<ReturnType<typeof createContext>>;

export const t = initTRPC.context<Context>().create();

import { aRouter } from "./routes/aRouter.routes";
import { t } from "./utils/trpc.utils";
import { onRequest } from "firebase-functions/v2/https";
import { createHTTPHandler } from "@trpc/server/adapters/standalone";
import cors from "cors";

export const appRouter = t.mergeRouters(aRouter);

export type AppRouter = typeof appRouter;

export const api = onRequest(createHTTPHandler({ router: appRouter, createContext: () => ({}), middleware: cors() }));