{
  lib,
  namespace,
  ...
}:
let
  inherit (lib.${namespace}) nixSettings;
in
{
  nix = {
    settings = nixSettings.commonSettings // {
      inherit (nixSettings)
        commonSubstituters
        commonTrustedPublicKeys
        ;
    };

    gc = nixSettings.commonGc;

    optimise.automatic = lib.mkDefault true;
  };

  nixpkgs = {
    config = {
      # CUDA and ROCm are not applicable on Darwin; those hardware modules are
      # NixOS-only.  Unfree allowance is handled globally via channels-config in
      # the flake.
      allowUnsupportedSystem = true;
    };
  };
}