This doesn't mean that AI tools aren't useful. They're about as useful as a sloppy junior developer who has read a thousand books and is now rushing things: Somewhat useful, but not trustworthy, and require much supervision.

The TODO comment left by the developer was misleading. The correct way to prevent duplicate memberships is a unique index on the underlying database table.

The check added by Codex is bonkers and doesn't prevent duplicate memberships when two calls are racing each other.