> After the acquisition, use of Mach wasn't expanded I believe modern XPC services integrated with launchd to allow on-demand job launching (similar to Linux d

> After the acquisition, use of Mach wasn't expanded I believe modern XPC services integrated with launchd to allow on-demand job launching (similar to Linux dbus-activation?) are based on Mach 'ports' (IPC). And tangentially, launchd "domains" (gui/user/system) are based on Mach "bootstrap domains", which is why a job launched in the background ("user") may have trouble communicating with a job launched in the GUI domain, if you're just assuming Unix permissions.