[casept]

Does anything like the Antithesis hypervisor exist as open source?

The closest I've seen is Qemu record/replay, but that's very slow (no KVM acceleration, no multicore), and broken in current Qemu versions (replayed system just gets stuck).

[eatonphil]

https://github.com/facebookexperimental/hermit but it hasn't worked for me and is now unmaintained.

[spencerflem]

There's languages that support time travel debugging, like RR for GDB, or smalltalk, but no open source system wide thing like Antithesis that I know of yet.

[dzaima]

rr can record process trees; i.e. basically any part/descendant of a process you spawn will be recorded and can be replayed (userspace CPU & memory, that is); won't record the entire OS though.