Yep

How exactly? Isn't a requirements.txt file, generated from pip-compile, incapable of specifying OS stuff?

It's also my understanding that pip-tools does not let you make layered requirements files with pyproject.toml files, only with .in files

You can specify different dependencies in pyproject.toml and then use --extra with pip-compile to pull them in. I do this with dev and test sections for example. Constraints seem like they work like you'd expect here. pip-compile also has the -c flag if you want to use that.

I guess I don't know what you mean by OS stuff, but maybe this works for that too?

Hmm. So you generate a requirements.txt and a dev-requirements.txt. It sounds like they have overlapping dependencies? I can't get them to be "layered" where the dev-requirements.txt only has the dev dependencies.

Ah, yeah that's what I do--I don't think there's any way to do that no.