> The borrow checker will catch all kinds of bugs that AI-generated code will happily compile in Zig but will blow up as UB at runtime.

This has not been my experience; Claude does a great job of writing unit tests for the Zig code, and combined with Zig's fuzzing features and a Python-based integration testing suite, I have avoided hitting runtime UB so far. In exchange, I get much faster compile times, which are important for the agentic development loop.