check / check (push) Successful in 5m15s
A login stores the username in the session cookie, which cannot carry a value past about 4096 bytes, so a username of about 2 KB or more could never log in and the login answered 500. Usernames are now limited to 1024 bytes, about half of what the cookie can carry. The User model rejects a longer one with ErrUsernameTooLong, and a check constraint on the users table rejects it for any path that bypasses the model. The comment on MaxUsernameBytes gives the arithmetic. Model: opus-5-5