I got the same issue and wonder why no one can give any hints?
Currently, we run multiple Next.js apps concurrently (with Turborepo) and I’m only able to authenticate the user on the “Login” application (running on a different port than the others).
More details: Authenticate User on multiple localhost Next.js apps (with different ports)
I really hope someone is able to provide an answer to a problem with a not uncommon approach to web app development.