Thanks for your help! I've figured out what the main entrypoint needs to do for an app extension, here's the relevant Objective-C code: // https://medium.com/@avaidyam/nsextension-pluginkit-a-brief-intro-2803be91a777 void NSExtensionMain() { @autoreleasepool { // Retrieve the default PKService instance id pkService = [NSClassFromString(@"PKService") defaultService]; if (pkService) { // Call the internal run method with arguments // Note: This mimics the behavior described, but PKService's _defaultRun:arguments: is private API. // In practice, use public APIs like NSXPCListener.resume() in your extension's principal class. [pkService run]; } else { // Fallback: Manually set up the NSXPCListener if PKService isn't available NSXPCListener *listener = [NSXPCListener serviceListener]; // Set your delegate that conforms to NSXPCListenerDelegate // Example: listener.delegate = [[YourExtensionDelegate alloc] init]; [listener resume]; } } } The network extension starts up now and successfully connects (just dropping the packets right now but this should be enough to start from).