Yes, I see what you mean now. You encountered a bug around system thread and dune didn’t properly pass your artifacts. That’s indeed annoying.
I deeply dislike dune myself and never use it. I just use the Ocaml toolchain like I would a good old C one which might explain our different experiences.
and yeah integrating to VS Code debugging UI would be ideal
I really like OCaml, so I hope the community can continue to improve the UX of these features