{
  inputs,
  lib,
  self,
  ...
}: let
  inherit
    (lib)
    singleton
    concatMap
    mkDefault
    mkImageMediaOverride
    ;
in {
  flake.nixosConfigurations.hela = inputs.nixpkgs-stable.lib.nixosSystem {
    system = "x86_64-linux";
    modules =
      singleton
      (import ./hela.nix);
    specialArgs = {
      inputs' = inputs;
    };
  };

  flake.nixosConfigurations."jörmungandr" = inputs.nixpkgs-stable.lib.nixosSystem {
    system = "x86_64-linux";
    modules =
      singleton
      (import ./jormungandr.nix);
    specialArgs = {
      inputs' = inputs;
    };
  };

  flake.nixosConfigurations.client = inputs.nixpkgs-stable.lib.nixosSystem {
    system = "x86_64-linux";
    modules =
      singleton
      (import ./client.nix);
    specialArgs = {
      inputs' = inputs;
    };
  };

  perSystem = {
    lib,
    pkgs,
    system,
    ...
  }: {
    checks.router = pkgs.stdenv.mkDerivation {
      name = "router";
      phases = [
        "runPhase"
      ];

      env = {
        HELA_SYSTEM =
          (self.nixosConfigurations.hela.extendModules {
            modules = [
              "${pkgs.path}/nixos/modules/testing/test-instrumentation.nix"
            ];
          })
          .config
          .system
          .build
          .vm;

        CLIENT_SYSTEM =
          (self.nixosConfigurations.client.extendModules {
            modules = [
              "${pkgs.path}/nixos/modules/testing/test-instrumentation.nix"
            ];
          })
          .config
          .system
          .build
          .vm;

        JORMUNGANDR_SYSTEM =
          (self.nixosConfigurations."jörmungandr".extendModules {
            modules = [
              "${pkgs.path}/nixos/modules/testing/test-instrumentation.nix"
            ];
          })
          .config
          .system
          .build
          .vm;
      };

      nativeBuildInputs = with pkgs; [
        iproute2
        vde2
        socat
        (python3.withPackages (ps:
          with ps; [
            ptpython
            colorama
            junit-xml
          ]))
      ];

      runPhase = ''
        PYTHONPATH=${pkgs.path}/nixos/lib/test-driver python ${../router.py}

        mkdir -p $out
        touch $out/success
      '';
    };
  };
}