sign-in on Vercel gives 404 for /api/auth/verify-request, works on localhost, also works on Vercel after a page refresh

[akoskm]

Hi!

Using the SendGrid provider I managed to implement signIn, signOut and session retrieval in my app. Everything works locally except receiving a bunch of errors because of some assertion errors that are probably caused by this.

The issue I'm facing right now is a weird one because locally when I sign in I get redirect to this page:

however, with my app deployed on Vercel the signIn ends up with this:

the weirdest thing is that when I reload the page, the URL is found. On the screenshot below you can see the first 404 and the 200 after the refresh:

I found a similar discussion where I also included screenshots from my Vercel logs: #10585 (comment)