> undefined behavior that even a mid-level C++ dev could have easily caught (assuming iterator stability in a vector that was being modified)

This is not an AI thing, plenty of "mid-level" C++ developers could have made that same mistake. New code should not be written in C++.

(I do wonder how Claude AI does when coding Rust, where at least you can be pretty sure that your code will work once it compiles successfully. Or Safe C++, if that ever becomes a thing.)