Insincere answer that will probably be attempted sincerely nonetheless: throw even more agents at the problem by having them do code review as well. The solution to problems caused by AI is always more AI.
Technically that's known as "LLM-as-judge" and it's all over the literature. The intuition would be that the capability to choose between two candidates doesn't exactly overlap with the ability to generate either one of them from scratch. It's a bit like how (half of) generative adversarial networks work.