I had similar feeling a couple months ago, but I changed the approach and feel more confident now. First of all, any feature now starts from RFC, then RFC brakes into manageable parts, I can review and understand, by planning. When feature is implemented, I run code review and QA pass. This is mandatory. Then I review PR, even eye-balling makes you more confident. If I have doubts, I write the review comment or ask the model to explain what the fragment does and how it relates to other parts. Then integration runtime testing - I use specially trained QA agent. Them manual testing.

Ask your agent to do a mock formal verification of your code, that will surface any gotchas. Create lots of unit tests. I think of the NL spec as an abstraction of the pseudocode which is an abstraction of the real code.