Claude Code, mostly, but I'm with Scipitie that the tool matters less than the process around it. What's helped most is writing the project's rules and conventions into files the agent reads each session, then putting the non-negotiable ones behind a linter or a test so it can't quietly skip them. Treated that way it behaves a lot like the junior who's read all the books and understood half of them. Left to its own judgement it drifts, which is the part the guardrails are there to catch.