upm

What's interesting is that the redacted full thread alludes to some of these invisible aspects, and Radon appears to have a justification for doing things that way (though it's all blacked out so we cannot evaluate the merits of that argument). https://imgur.com/a/OaEOwu2 https://github.com/replit/upm is likely one of the blacked-out bits in that email, as Radon says he wrote the README.

pipreqs' mapping was my first guess: https://github.com/bndr/pipreqs/blob/master/pipreqs/mapping Although it looks like they may have expanded beyond pipreqs: https://github.com/replit/upm/pull/4

Mac and windows too https://github.com/replit/upm#macos

No magic, it's automating and hooking into existing open-source tools. For Python its poetry (https://python-poetry.org/), not requirements.txt because UPM needs to present strong guarantees on reproducibility -- otherwise things like content-addressable caching wouldn't be possible. Poetry is open-source and UPM is too: https://github.com/replit/upm Every Replit Python project can be downloaded and you'll have the spec file and the lock file so you can install the same dependencies locally.