{ ... }: {
  # Steam runtime tweaks (user-session level, not NixOS system config)

  home.sessionVariables = {
    # Improves scaling consistency on HiDPI / Wayland setups
    STEAM_FORCE_DESKTOPUI_SCALING = "1.25";

    # Optional Proton-related behavior toggles (safe defaults)
    PROTON_ENABLE_NVAPI = "1";
    PROTON_NO_ESYNC = "0";
    PROTON_NO_FSYNC = "0";
  };
}