Love this. I've shifted in the past few months to using highly expressive types in Scala 3 to have types carry more and more compile-time proofs (without macros, though a couple are warranted). Not only does it help with agentic test "sprawl", it seems to prevent agents from falling into lower-quality modes of operation. One of the more annoying things I've been preventing is what I call "noun accretion", where agents try and make a new monomorphic type for everything, instead of clearly genericizing when sensible. My bet is on formal-method-shaped tooling (including languages with strong type systems) to accelerate decent-quality agentic coding.

When I say "highly expressive types", I mean techniques I'd likely not want to ship in a typical codebase, unless the team was already on the typelevel programming bandwagon (i.e. having HKT and type functions being basic blocks already, not weird). Agents are better at "math" than basically most devs (even category-theory-pilled ones), at least in terms of knowledge. Better yet, they are decent at pedagogy, especially when considering they have "infinite" patience for dialogue.

In a more personal setting, I've had Codex Lean-ify a couple of my hobby proofs, it was extremely easy. Note: not saying it did this 100% "correctly" (gotta learn more Lean 4 to check more thoroughly), but it also seems to check for classic proof gotchas by default. Very excited for the future of formal methods.