What's the minimum macOS version supported by Nix?

I know we’re now using the 10.12 SDK for our macOS builds, but I don’t know what the minimum version you can run Nix on is.

Similarly, what version of macOS is Hydra running for its Darwin builds?

According to Matt’s blog post, the minimum version of macOS supported by nixpkgs is 10.12.

Huh, I didn’t realize that nixpkgs set the minimum macOS version to the same as its SDK version.

Is Hydra running macOS 10.12 (for its Darwin builds) or something newer?