GitLab CI YAML is one of those formats where you can stare at it for an hour, get it 95% right, and have it fail with yaml: line 12: did not find expected key because of a tab character. AI assistants are very fast at this kind of work. They're also confidently wrong about specific GitLab features in ways that waste a lot of time if you don't know what to check. After a year of letting Claude write a lot of my pipelines, here's what works and what doesn't.