404 on api/auth/session when using basePath

Your question

How to set the correct path for /api/auth/session in an app using a custom basePath, it seems like an explicit NEXTAUTH_URL is ignored?

What are you trying to do

I have a global login app at root, running on mysite.com

On successful login, this redirects to another app which sits on a subpath like mysite.com/custom-app/

This app has a custom basePath set in the next.config.js

basePath: '/custom-app',

Login is successful and navigation to the subpath works correctly, but when the session is checked for, it seems to ignore the NEXTAUTH_URL and just checks the session at the default mysite.com/api/auth/session ?

NEXTAUTH_URL=mysite.com/custom-app/api/auth/

If I remove the basePath, everything works correctly when testing between two apps; one running on localhost:8080 the other localhost:3000

Just wondering if I’m missing something, or if this is even possible yet?

Thanks

• Found the documentation helpful
• Found documentation but was incomplete
• Could not find relevant documentation
• Found the example project helpful
• Did not find the example project helpful

[iaincollins]

@callamwilliams This is really interesting and I don’t actually understand the problem here or why what you did worked.

Please fee free to leave this open for future investigation in case it hints at a bug or just a gap in the docs.

I think the problem could be solved with a pages/_app.js file which sets this option for both client and server side renders, although it looks like this functionality is not documented.

import { Provider } from 'next-auth/client'

export default function App ({ Component, pageProps }) => {
  return (
    <Provider session={pageProps.session} options={{ basePath: `/custom-app/api/auth` }}>
      <Component {...pageProps} />
    </Provider>
  )
}

I’d be interested in knowing if this also worked, instead of using next.config.js to export the env var - although I think exporting the env var that is absolute fine too, and I can see why it resolves the issue with a custom base path (as the NextAuth.js “client” supports being run both browser and server side, and reads in default values for options from env vars if they are set).

[balazsorban44]

For anyone ending up here, I summed up a possible solution at #1713! Please go there and comment on what you think!