But how would you verify that the agents have written memory safe code? Rust's borrowchecker is a lot faster and actually verifiably safe compared to asking an LLM to fix the safety issues that the Zig version had.

Maybe they'd get the same numeric improvements and bug fixes today (or maybe not, or maybe they'd get even more since the LLM isn't spending time rewriting correct code).

But they wouldn't get a change to the structural issues that created the issues in the first place. They'd end up "ke[eping] fixing these kinds of bugs one-off in perpetuity".

Unfortunately (and I say this because I hate this whole rust rewrite) no. There is no fixing a third-party garbage collector on top of the non-memory-managed language. Jarred explains in a post what would that Zig look like.