Why is the basePath in Next Auth v5 still not working?

[hscstudio]

I have encountered several issues when implementing basePath, but unfortunately, the core auth developers only respond by sending irrelevant example links.

If basePath does indeed work, try setting it to something like basePath /custom, and I can confirm it won't work properly.

In my case, if the issue lies here, authentication succeeds but the redirect always goes to /api/auth/callback/keycloak?... instead of /custom/api/auth/callback/keycloak?....

If I manually change it to 'custom', then it works fine.

Just try it yourself if you don't believe me.