Redirect to 404 "/api/auth/callback/github?code=" after authentication

[Mordai]

Environment

  System:
    OS: Linux 6.6 Manjaro Linux
    CPU: (20) x64 12th Gen Intel(R) Core(TM) i7-12700K
    Memory: 25.21 GB / 31.11 GB
    Container: Yes
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 23.3.0 - /usr/bin/node
    npm: 11.0.0 - /usr/bin/npm
  npmPackages:
    next: 15.1.4 => 15.1.4 
    next-auth: ^5.0.0-beta.25 => 5.0.0-beta.25 
    react: ^19.0.0 => 19.0.0 

Reproduction URL

https://github.com/Mordai/yt-directory

Describe the issue

When signing in with the GitHub provider using Auth.js (next-auth), after the OAuth flow completes, the user is redirected to http://localhost:3000/api/auth/callback/github?code=CODE (I got a 404 error page there) and not to the default root page (/).

How to reproduce

1. Set up a Next.js app with the following dependencies:

next: 15.1.4
next-auth: 5.0.0-beta.25
react: 19.0.0

2. Configure Auth.js with the GitHub provider (in auth.ts file):

import NextAuth from "next-auth";
import GitHub from "next-auth/providers/github";

export const { handlers, signIn, signOut, auth } = NextAuth({
  providers: [GitHub],
});

3. Create Auth.js App Router files.
   Create a route.ts file in app/api/auth/[...nextauth] folder with the content:

import { handlers } from "@/auth"; // Referring to the auth.ts
export const { GET, POST } = handlers;

4. Configure a GitHub OAuth App.
   My .env.local file:

AUTH_SECRET=<my secret> # Added by `npx auth`.
AUTH_GITHUB_ID=<my GitHub ID>
AUTH_GITHUB_SECRET=<my GitHub secret>

5. Call the signIn function on a page:

<form
  action={async () => {
    "use server";
    await signIn("github");
  }}>
  <button type="submit">Sign in</button>
</form>

6. Sign in with GitHub.
   Observe the redirection sequence:
   After a successfull authentication, you'll be redirected to http://localhost:3000/api/auth/callback/github?code=CODE and see a 404 page.

Expected behavior

After signing in, the user should be redirected back to the app (root), as no custom redirects/middlewares were defined.

[JayWebtech]

Try building your project let's see if it will build successfully

[Mordai]

Yeah, I tried it (it builds without any errors/warnings), but the same behaviour after running the built application: redirect to a 404 [...]/callback URL.

[Mordai]

Solved.
I had whitespace in my path :)