I already have a public REST API (PHP/Nginx) which is live and already being consumed, lets call it https://example.com/api/...

Now there has to come a GUI with authentication, to manage the API resources. The GUI should be accessible through the API’s main URL https://example.com. I decided to use Next.js and next-auth 4.

next-auth 4’s routing uses /api/auth/* by default. This works fine locally.

Now the problem is the deployment. When I go to https://example.com, I see the UI build. As soon as I click on the login button, a route change to https://example.com/api/auth/error happens, but showing the error output of the REST API (PHP/Nginx). This behavior makes sense for now, since the Webserver is configured in that way, that all /api requests are calling the REST API entrypoint.

What I don’t want is to configure the webserver in such a way, that /api/auth is ignored for calling the REST API entrypoint. Because it’s not only a webserver, its in a Kubernetes cluster, and this is complicated (we are using helmfile, helmcharts, etc.).

What I would like is the ability to customize the next-auth default authentication routing.

I tried with the basePath stuff, but I just get 404 errors, until I realized (if I unterstood correctly) that this feature is anyway only for when the entire UI has to come in a subpath, which is not in my case.

Is there any way to customize the next-auth /api/auth/* path, without changing the basePath?

When I just put pages/api into pages/foo/api, obviously on a page refresh I get GET http://localhost:3000/api/auth/session 404 (Not Found), because next-auth expects the api folder to be in pages/.