{ inputs, self, ... }:
{
  perSystem =
    { pkgs, system, ... }:
    {
      devShells.common = pkgs.mkShellNoCC {
        name = "common";

        packages = [
          pkgs.nixd
        ];

        shellHook = ''
          hooksdir="$(git rev-parse --show-toplevel)/root/hooks"
          if [ ! -d "$hooksdir" ]; then
            echo "error: hooks directory not found at $hooksdir"
            exit 1
          fi
          git config set core.hooksPath "$hooksdir"
        '';
      };

      devShells.root =
        let
          treefmt = pkgs.callPackage ./_treefmt.nix { treefmt-nix = inputs.treefmt-nix; };
        in
        pkgs.mkShellNoCC {
          name = "root";

          inputsFrom = [ self.devShells."${system}".common ];
          packages = [
            # keep-sorted start
            (pkgs.python3.withPackages (ps: [ ps.git-filter-repo ]))
            pkgs.ty
            treefmt
            # keep-sorted end
          ];
          shellHook = ''
            export TREEFMT_WORKING_DIR="$("${pkgs.git}/bin/git" rev-parse --show-toplevel)"
          '';
        };
    };
}