{ inputs, ... }:
{
  perSystem =
    { config, self', pkgs, lib, system, ... }:
    let
      # Load workspace from uv.lock
      workspace = inputs.uv2nix.lib.workspace.loadWorkspace {
        workspaceRoot = inputs.self;
      };

      # Create overlay from workspace
      # Use wheels from PyPI for most packages; we override mlx with our pure Nix Metal build
      overlay = workspace.mkPyprojectOverlay { sourcePreference = "wheel"; };

      # Override overlay to inject Nix-built components
      exoOverlay = final: prev: {
        # Replace workspace exo_pyo3_bindings with Nix-built wheel
        exo-pyo3-bindings = pkgs.stdenv.mkDerivation {
          pname = "exo-pyo3-bindings";
          version = "0.1.0";
          src = self'.packages.exo_pyo3_bindings;
          # Install from pre-built wheel
          nativeBuildInputs = [ final.pyprojectWheelHook ];
          dontStrip = true;
        };
      };

      python = pkgs.python313;

      # Overlay to provide build systems and custom packages
      buildSystemsOverlay = final: prev: {
        # Use our pure Nix-built MLX with Metal support
        mlx = self'.packages.mlx;

        # mlx-lm is a git dependency that needs setuptools
        mlx-lm = prev.mlx-lm.overrideAttrs (old: {
          nativeBuildInputs = (old.nativeBuildInputs or [ ]) ++ [
            final.setuptools
          ];
        });
      };

      pythonSet = (pkgs.callPackage inputs.pyproject-nix.build.packages {
        inherit python;
      }).overrideScope (
        lib.composeManyExtensions [
          inputs.pyproject-build-systems.overlays.default
          overlay
          exoOverlay
          buildSystemsOverlay
        ]
      );
      exoVenv = pythonSet.mkVirtualEnv "exo-env" workspace.deps.default;

      # Virtual environment with dev dependencies for testing
      testVenv = pythonSet.mkVirtualEnv "exo-test-env" (
        workspace.deps.default // {
          exo = [ "dev" ]; # Include pytest, pytest-asyncio, pytest-env
        }
      );

      exoPackage = pkgs.runCommand "exo"
        {
          nativeBuildInputs = [ pkgs.makeWrapper ];
        }
        ''
          mkdir -p $out/bin

          # Create wrapper scripts
          for script in exo exo-master exo-worker; do
            makeWrapper ${exoVenv}/bin/$script $out/bin/$script \
              --set DASHBOARD_DIR ${self'.packages.dashboard} \
              ${lib.optionalString pkgs.stdenv.isDarwin "--prefix PATH : ${pkgs.macmon}/bin"}
          done
        '';
    in
    {
      # Python package only available on macOS (requires MLX/Metal)
      packages = lib.optionalAttrs pkgs.stdenv.hostPlatform.isDarwin {
        exo = exoPackage;
        # Test environment for running pytest outside of Nix sandbox (needs GPU access)
        exo-test-env = testVenv;
      };

      checks = {
        # Ruff linting (works on all platforms)
        lint = pkgs.runCommand "ruff-lint" { } ''
          export RUFF_CACHE_DIR="$TMPDIR/ruff-cache"
          ${pkgs.ruff}/bin/ruff check ${inputs.self}/
          touch $out
        '';
      };
    };
}