nixos-config/options/host/version.nix

{
  lib,
  pkgs,
  config,
  ...
}:
let
  cfg = config.host.version;
in
{
  options = {
    host.version = lib.mkOption {
      type = lib.types.str;
      default = "25.05";
      description = "System version.";
    };
  };

  config.system.stateVersion = cfg;
}