If you’re using the latest models( Opus/Fable/Astra/ maybe Sol) and the default harness, along with a little guidance against the worst tendencies like over-writing tests, you really shouldn’t be getting the wrong things built. Like a coworker, you can’t throw it blind into a monster codebase without some guidance, but otherwise the latest models genuinely just work TM.

Testing, testing, and more testing. In the project I'm working on right now, about 2/3 of the code is in one way or another related to testing. As a human coder, I'd never spend that much time on building test harnesses, automating regressions, writing unit tests, etc, but it's cheap when you can have a robot do it.