One default value broke every new signup
A dropped database column stayed referenced by a default value in the auth config. New accounts failed at creation.
New signups stopped completing. Existing users could still sign in. The error surfaced as an unknown column on insert.
A migration had dropped a column that used to live on the user table, moved to be organization-scoped instead. The auth library (Better Auth) still had that field declared in its config, with a default value attached. A default value gets written on every insert, whether or not anything in the app still reads it. Every new account tried to write to a column that no longer existed. Every existing sign-in worked fine, because sign-in does not insert a row.
The fix was one line: remove the stale field from the auth config to match the schema. The lesson was the bigger part, a field with a default value is not inert just because nothing reads it anymore. It still writes.
Try it
If a migration drops a column, grep your auth or ORM config for any default value still pointing at it before you call the migration done. The column doesn't come back just because you stopped looking at it.