Fix your Next.js login and keep users signed in across two apps

Split one app into two, or built them separately with Bolt or Lovable and now want a single login across both? That's this job.

What usually turns out to be wrong: the session cookie is scoped to the exact host instead of the parent domain, so signing in on one app leaves the other logged out. Or the middleware guards pages but not the API routes underneath them. That one looks fine until somebody checks. Or a refresh token races with itself on a slow connection and drops people back to the login screen for no reason they can see.

I go through your auth flow, tell you which of those is happening, then fix it. NextAuth, Supabase Auth or your own JWT setup, whichever you're on.

You get shared sessions that hold, routes that are genuinely protected rather than protected-looking, and a short note on what was broken so it doesn't come back next month.