user_already_exists
what this Supabase Auth error means
How it shows up
AuthApiError: User already registered
What it means
Supabase Auth cannot create this user because an account with the same email address or phone number already exists.
The usual cause in an AI-built app
AI-generated auth screens often call signUp for returning users too, or a test account was already created with the same email while the app was being built.
Check this first
Search for the email under Authentication, Users in the Supabase dashboard to see whether the account already exists and how it was created.