{
  description = "DCOS — Distributed Cognitive Operating System";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let
        pkgs = nixpkgs.legacyPackages.${system};
        python = pkgs.python312;
        pythonPackages = pkgs.python312Packages;
      in {
        packages.default = pythonPackages.buildPythonPackage {
          pname = "dcos";
          version = "1.0.0";
          src = ./.;
          nativeBuildInputs = with pythonPackages; [
            python
            setuptools
            wheel
            pytest
            pytest-asyncio
          ];
          propagatedBuildInputs = with pythonPackages; [
            pyyaml
            pydantic
          ];
          doCheck = true;
          checkPhase = ''
            python -m pytest tests/ -x --tb=short -q
          '';
          pyproject = true;
          pyprojectFiles = [ "pyproject.toml" ];
          makeWheel = true;
          packageDir = "src";
        };

        devShells.default = pkgs.mkShell {
          packages = with pkgs; [
            python
            pythonPackages.pip
            pythonPackages.pytest
            pythonPackages.pytest-asyncio
            pythonPackages.pyyaml
            pythonPackages.pydantic
            pythonPackages.ruff
          ];
          shellHook = ''
            export PYTHONPATH="${toString ./src}:$PYTHONPATH"
            echo "DCOS dev shell — Python 3.12, pytest, pyyaml, pydantic"
          '';
        };
      });
}