I am targeting iOS. By shut down, I mean it's not running in the background: the app was started the app after restarting the phone or the app crashed or was forced quit. To my surprise, I tested the Outlook app for Android an it did not recieve any calendar alerts after I force quit outlook. In my mind, there should be a service always running in the background to check for incoming calendar alerts even if the user has not interacted with the email app.

deleted comment

Thank you. Occurs within a library running on another thread. It's could be the async await I recently added. 2 libswift_Concurrency.dylib 0x000000020f5397cc swift::runJobInEstablishedExecutorContext(swift::Job*) + 244 (Task.h:282) It only crashes for some people in production, so I'll revert my URLSession code to regular callbacks for now.