AI now writes about 90% of Claude Code's own code. So who reviews it all? Not one human reading line by line. That stopped working as a gate a while ago. Anthropic just published how its team replaced it. The results from June to September: → Merged PRs more than doubled → The share of PRs needing a revert fell by more than 40% → PRs passing after one review round went from 65% to 78% What changed was the review system, not the reviewers. It works in six layers: 1- Verify before the PR exists. The agent runs tests, build and lint and shows the output, instead of just saying it worked. 2- AI review on every PR. Several agents look for bugs in parallel, and the findings get voted on before any are posted. 3- A security review that can block the merge. 4- Required CI. 5- Human approval scaled to the risk: 0, 1 or 2 people depending on what the change touches. 6- Feature flags and staged releases, with one-step rollback. The rule I'm copying first: cap review rounds at 3. Agents will happily fix each other's nitpicks forever. One PR ran more than 50 overnight rounds before its author stopped it. What humans still own: judgment, direction, the risky code paths, and the outcome of every change that ships. The full breakdown is in the carousel. Anthropic's full write up is in the comment.