[pxc]

Devenv includes direnv integration, but the main feature is organizing development environment configurations using a NixOS-like module system rather than declaring them as packages (simple functions).

Guix (deliberately) doesn't support anything like the NixOS module semantics. 'Services' are its alternative, of course. I don't know if there is a capability for per-project service declaration in Guix atm, but it wouldn't surprise me!