{
  inputs,
  ...
}:
_: prev: {
  # include nixpkgs stable
  stable = import inputs.nixpkgs-stable {
    inherit (prev.pkgs) system;
    config.allowUnfree = true;
  };

  # include custom packages
  custom =
    (prev.custom or { })
    // (import ../packages {
      inherit (prev) pkgs;
      inherit inputs;
    });

  # use nixfmt-rfc-style as the default
  nixfmt = prev.nixfmt or prev.nixfmt-rfc-style;
}