{
  inputs = {
    nixops4.follows = "nixops4-nixos/nixops4";
    nixops4-nixos.url = "github:nixops4/nixops4-nixos";
  };

  outputs =
    inputs:
    {
      nixConfig = {
        extra-trusted-substituters = "https://cache.saumon.network/proxmox-nixos";
        extra-trusted-public-keys = "proxmox-nixos:D9RYSWpQQC/msZUWphOY2I5RLH5Dd6yQcaHIuug7dWM=";
      };
    }
    // import ./mkFlake.nix inputs (
      { inputs, sources, ... }:
      {
        imports = [
          "${sources.git-hooks}/flake-module.nix"
          inputs.nixops4.modules.flake.default

          ./deployment/flake-part.nix
          ./infra/flake-part.nix
          ./keys/flake-part.nix
          ./secrets/flake-part.nix
          ./services/tests/flake-part.nix
        ];

        perSystem =
          {
            pkgs,
            lib,
            system,
            ...
          }:
          {
            checks = {
              panel = (import ./. { inherit sources system; }).tests.panel.basic;
            };
            formatter = pkgs.nixfmt-rfc-style;

            pre-commit.settings.hooks =
              let
                ## Add a directory here if pre-commit hooks shouldn't apply to it.
                optout = [ "npins" ];
                excludes = map (dir: "^${dir}/") optout;
                addExcludes = lib.mapAttrs (_: c: c // { inherit excludes; });
              in
              addExcludes {
                nixfmt-rfc-style.enable = true;
                deadnix.enable = true;
                trim-trailing-whitespace.enable = true;
                shellcheck.enable = true;
              };
            apps =
              let
                default-configuration = builtins.fromJSON (
                  let
                    env = builtins.getEnv "DEPLOYMENT";
                  in
                  if env != "" then
                    env
                  else
                    builtins.trace "env var DEPLOYMENT not set, falling back to `deployment/configuration.sample.json`!" (
                      lib.readFile ./deployment/configuration.sample.json
                    )
                );
                host-mapping = {
                  pixelfed = "test04";
                  peertube = "test05";
                  mastodon = "test06";
                };
                inherit
                  (import ./deployment/fediversity {
                    inherit system host-mapping;
                    ancilliary.garage = "test01";
                    conf."default-configuration" = default-configuration // {
                      enable = true;
                      applications = lib.mapAttrs (_app: _: { enable = true; }) host-mapping;
                    };
                  })
                  ssh-hosts
                  ;
              in
              lib.mapAttrs (_: program: {
                type = "app";
                inherit program;
              }) ssh-hosts;
          };
      }
    );
}