Here's a talk on that topic: https://infocondb.org/con/recon/recon-2023/be-kind-please-rewind-adventures-in-creating-a-macos-recordreplay-debugger https://infoc

Here's a talk on that topic: https://infocondb.org/con/recon/recon-2023/be-kind-please-rewind-adventures-in-creating-a-macos-recordreplay-debugger https://infocondb.org/con/recon/recon-2023/be-kind-please-re.... IIRC, they ended up implementing a form of lightweight VM to be able to instrument programs on macOS.