I think this approach to bug hunting is super promising (obviously - it finds a ton of bugs). The long-term problem is how this kind of bug-hunting can be done routinely, e.g. as part of a test suite. The approach taken by these people, the same approach as when the Julia folks did it, isn't really automatable, because it requires a lot of both human and AI agent work.

I guess longer term it needs to be built into the language, to prevent code and lean proofs from drifting. I.e. it could be opt-in properties that are written along the code, and which is then checked in the test suite. So very similar to ordinary compiler checks, except more expressive and expensive, and done only at test time.

At that point you might as well use Lean?

It would solve the two language problem :-)

Interesting. Now I have an idea to extend my tooling flow, thanks.

bend programming language already solved this problem: https://bend-lang.com/