Have you had a chance to explore `Better Auth`

Error importing route file: Error: Client created with undefined deployment address. If you used an environment variable, check that it's set.
    at validateDeploymentUrl (file:///Users/me/proj/node_modules/convex/dist/esm/common/index.js:15:11

Error importing route file: Error: Client created with undefined deployment address. If you used an environment variable, check that it's set.
    at validateDeploymentUrl (file:///Users/me/proj/node_modules/convex/dist/esm/common/index.js:15:11

import { auth } from '@/lib/auth' // import your auth instance
import { createAPIFileRoute } from '@tanstack/react-start/api'
 
export const APIRoute = createAPIFileRoute('/api/auth/$')({
  GET: ({ request }) => {
    return auth.handler(request)
  },
  POST: ({ request }) => {
    return auth.handler(request)
  },
})

import { auth } from '@/lib/auth' // import your auth instance
import { createAPIFileRoute } from '@tanstack/react-start/api'
 
export const APIRoute = createAPIFileRoute('/api/auth/$')({
  GET: ({ request }) => {
    return auth.handler(request)
  },
  POST: ({ request }) => {
    return auth.handler(request)
  },
})

const getUser$ = createServerFn({ method: "GET" }).handler(async () => {
    const webRequest = getWebRequest();

    if (!webRequest) {
        throw new Error("Web request not available");
    }

    const { headers } = webRequest;
    const session = await authClient.getSession({
        fetchOptions: { headers },
        query: { disableCookieCache: true },
    });

    return session?.data?.user || null;
});

const getUser$ = createServerFn({ method: "GET" }).handler(async () => {
    const webRequest = getWebRequest();

    if (!webRequest) {
        throw new Error("Web request not available");
    }

    const { headers } = webRequest;
    const session = await authClient.getSession({
        fetchOptions: { headers },
        query: { disableCookieCache: true },
    });

    return session?.data?.user || null;
});

convex/users.ts

import { query } from "./_generated/server";
import { betterAuth } from "./http";

export const getAuth = query({
    handler: async (ctx) => {
        const user = await betterAuth.getAuthUser(ctx)
        
        return user
    }
})

convex/users.ts

import { query } from "./_generated/server";
import { betterAuth } from "./http";

export const getAuth = query({
    handler: async (ctx) => {
        const user = await betterAuth.getAuthUser(ctx)
        
        return user
    }
})

app/page.tsx

import { api } from "@/convex/_generated/api";
import { fetchQuery } from "convex/nextjs";

export default async function Chat() {
  const user = await fetchQuery(api.users.getAuth, {});

  console.log(user);

  return <div>{user?.email ?? "no user"}</div>;
}

app/page.tsx

import { api } from "@/convex/_generated/api";
import { fetchQuery } from "convex/nextjs";

export default async function Chat() {
  const user = await fetchQuery(api.users.getAuth, {});

  console.log(user);

  return <div>{user?.email ?? "no user"}</div>;
}

import { createRouter as createTanStackRouter } from "@tanstack/react-router";
import { QueryClient } from "@tanstack/react-query";
import { routerWithQueryClient } from "@tanstack/react-router-with-query";
import { ConvexQueryClient } from "@convex-dev/react-query";
import { ConvexProviderWithAuth } from "convex/react";
import { useBetterAuth } from "@erquhart/convex-better-auth/react";
import { authClient } from "~/lib/auth-client";
import { routeTree } from "./routeTree.gen";
import { NotFound } from "~/components/not-found";
import { Error as ErrorBoundary } from "~/components/error";

export function createRouter() {
  const PUBLIC_CONVEX_URL = import.meta.env.PUBLIC_CONVEX_URL;
  const convexQueryClient = new ConvexQueryClient(PUBLIC_CONVEX_URL);

  const queryClient: QueryClient = new QueryClient({
    defaultOptions: {
      queries: {
        queryKeyHashFn: convexQueryClient.hashFn(),
        queryFn: convexQueryClient.queryFn(),
      },
    },
  });
  convexQueryClient.connect(queryClient);

  const router = routerWithQueryClient(
    createTanStackRouter({
      routeTree,
      defaultPreload: "intent", 
      context: { queryClient },
      Wrap: ({ children }) => (
        <ConvexProviderWithAuth client={queryClient} useAuth={useBetterAuth(authClient)}> // Error is here
          {children}
        </ConvexProviderWithAuth>
      ),
      defaultNotFoundComponent: NotFound,
      defaultErrorComponent: ErrorBoundary,
      scrollRestoration: false,
    }),
    queryClient,
  );

  return router;
}

declare module "@tanstack/react-router" {
  interface Register {
    router: ReturnType<typeof createRouter>;
  }
}

import { createRouter as createTanStackRouter } from "@tanstack/react-router";
import { QueryClient } from "@tanstack/react-query";
import { routerWithQueryClient } from "@tanstack/react-router-with-query";
import { ConvexQueryClient } from "@convex-dev/react-query";
import { ConvexProviderWithAuth } from "convex/react";
import { useBetterAuth } from "@erquhart/convex-better-auth/react";
import { authClient } from "~/lib/auth-client";
import { routeTree } from "./routeTree.gen";
import { NotFound } from "~/components/not-found";
import { Error as ErrorBoundary } from "~/components/error";

export function createRouter() {
  const PUBLIC_CONVEX_URL = import.meta.env.PUBLIC_CONVEX_URL;
  const convexQueryClient = new ConvexQueryClient(PUBLIC_CONVEX_URL);

  const queryClient: QueryClient = new QueryClient({
    defaultOptions: {
      queries: {
        queryKeyHashFn: convexQueryClient.hashFn(),
        queryFn: convexQueryClient.queryFn(),
      },
    },
  });
  convexQueryClient.connect(queryClient);

  const router = routerWithQueryClient(
    createTanStackRouter({
      routeTree,
      defaultPreload: "intent", 
      context: { queryClient },
      Wrap: ({ children }) => (
        <ConvexProviderWithAuth client={queryClient} useAuth={useBetterAuth(authClient)}> // Error is here
          {children}
        </ConvexProviderWithAuth>
      ),
      defaultNotFoundComponent: NotFound,
      defaultErrorComponent: ErrorBoundary,
      scrollRestoration: false,
    }),
    queryClient,
  );

  return router;
}

declare module "@tanstack/react-router" {
  interface Register {
    router: ReturnType<typeof createRouter>;
  }
}