What is your workflow for catching LLM code changes before they break your repo?

I spent hours last week re-checking an agent's work because it skipped core steps from a spec I explicitly approved.

Having to manually audit thirty different file changes completely defeats the point of automating the build.

Now I write a separate reference file directly from existing code and force the runner to compare against it before marked complete.

How do you handle automated coding tools going off-script without spending all your time reviewing PRs?