What he is doing in there is kinda cool but the trampoline app solution is quite similar and unfortunately does not fix this problem. Fundamentally the problem is that when you install stuff with nix it gets a folder that is unique to that nix generation. That is by design nix, because you want to be able to go back and forth between generations etc. Apple does not think of things the same way. Applications is a single folder that you can’t subdivide with iterations and it’s “speshul”. These core philosophies are antithetical to each other. This is fine for Most applications who don’t need to be in Applications. You let Nix install into its own little /nix/ generation folder and then create a “trampoline” in applications which is basically like a symlink. Then your app shows up in spotlight etc. where this falls apart is applications like 1Password that MUST boot from the speshul Applications folder

However, you are right, it definitely makes some other pieces of this cleaner. In particular, if you just use homebrew directly with nix, you aren't deterministic or reproducible. You have an impure setup because if you remove a cask from the list, it doesn't actually delete it from homebrew, and you can't go back and forth with generations because homebrew is stuffing things in /applications. The project you linked forces brew stuff to behave like Nix applications and go in /nix instead, which allows it to be able to walk between generations. So it solves most of the issues with brew and nix but not all of them.