I think performance expectations for shells on Windows are pretty different. The first time I open PowerShell in a given session on my work computer, it takes ~9 seconds on average, without a particularly complex config.
That said, I think it can also makes sense to aim higher in terms of performance at the cost of a more bespoke Windows implementation. lol
(Although Oil will obviously run on OS X because it uses plain libc from source, as is officially supported)
Cosmopolitan libc does seem interesting, because a shell basically only depends on libc.
It would be interesting to get Oil to run like that, on platforms where fork() is supported (not bare metal I assume).
Would it work on Windows? How do they do fork() emulation? I think that's very hard on Windows
Oh yeah it looks like it's slow on Windows (and OpenBSD)
https://justine.lol/cosmopolitan/functions.html
So I don't think it would make sense as a path for portability for a "production" shell