(instancetype)propertiesRequestForExtension:(NSString *)identifier queue:(dispatch_queue_t)queue; Looks very promising. I'll check it out!

If it responds over XPC it's definitely activated, we are good on this part. I'm not sure though that an activated extension is always running, for whatever reason. Can we assume that even if it's not running (there is no process) macOS will always start it up for me just because I issued an XPC request over its Mach service?