The following code func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool { // create window     MXMetricManager.shared.add(self)     do {       try MXMetricManager.extendLaunchMeasurement(forTaskID: MXLaunchTaskID("1234.zmmm"))       print("some task perform")       try MXMetricManager.finishExtendedLaunchMeasurement(forTaskID: MXLaunchTaskID("1234.zmmm"))     } catch {       print(error)     }     return true   }

@Jason, Thank you for your answer. But i didn't download any file. Actually, my extension doesn't receive task callbacks after app install. I got these errors from console.app when I debug the Background Asset from the command line. And what should i do now? (And if I add a comment directly, it doesn't show?)