I'm surprised that whatever IO primitive is used on Mac doesn't work on OpenBSD. Mac has select and some variant of kqueue, right? What is ghostty doing there that doesn't work on OpenBSD?
Might not be that different to add OpenBSD. Someone would begin here: https://github.com/mitchellh/libxev/blob/main/src/backend/kq...
It's about 1/3 tests and 2/3 mostly-designed-to-be-portable code. Some existing gaps for FreeBSD, but fixing those (and adding OpenBSD to some switch/enums) should get you most of the way there.
E.g., here it is kqueue-aware on FreeBSD: https://github.com/mitchellh/libxev/blob/34fa50878aec6e5fa8f...
Might not be that different to add OpenBSD. Someone would begin here: https://github.com/mitchellh/libxev/blob/main/src/backend/kq... It's about 1/3 tests and 2/3 mostly-designed-to-be-portable code. Some existing gaps for FreeBSD, but fixing those (and adding OpenBSD to some switch/enums) should get you most of the way there.