> I can't think of a functional reason for a no-AI policy: if it runs, it runs, regardless of who or what made it.

AI-written code is far less likely to run than human-written code. Even worse, it often gives the appearance that it will be fine, only blowing up down the line. That is an extremely strong functional reason to reject AI code.

That depends on the model and the toolkit it uses. In my experience from using Claude Code (Max, Opus 4.5+) intensely for the past six months, I maybe had 3 instances where the implementation broke functionally. And all of these breaking changes were resolved by Claude.

Obviously, this won't apply to every context: I work primarily with well-known langs (e.g., Python, JS), small to medium codebases (<500k LoC, for sure), and relatively few co-developers.