Totally agree! I wrote a whole essay about it, before Apple deprecated the APIs, pointing out some of the missing elements to make a smooth experience. Now, you just have to allow users to send "share URLs" to each other manually. https://deeje.medium.com/cloudkit-sharing-apple-and-you-900441dbef29

I thought I read somewhere that the action to delete storage is only for the dev environment? If you want to delete your data, you can do that via Settings > [Apple ID] > iCloud > Manage Account Storage > [Your App] > Delete

you can register for notifications of the player for events such as starting, stopping, pausing, etc. While the music player is playing, you'll want to set up a Timer to periodically update a progress bar. In SwiftUI you can use the TimelineView to periodically update the progress bar. https://developer.apple.com/documentation/swiftui/timelineview

fwiw, I'm still getting up to speed on Swift concurrency, but I suspect that NSManagedObject is most definitely not sendable.

In the "Signing and Capabilities" section of your app target, make sure you add the "Background Modes" capability and enable "Remote notifications" https://developer.apple.com/documentation/swiftdata/syncing-model-data-across-a-persons-devices

is your code kicking off 100 CKModifyRecordsOperations simultaneously? yes, assume any CloudKit operation can receive a throttling error and respond as needed

also, in case you haven't found this yet… https://developer.apple.com/documentation/technotes/tn3162-understanding-cloudkit-throttles

is the question, you are building a new version of your app and want to load an existing store from an old version, and also enable history, does that work and what are the implications? My suggestion is to build a test app, define a core data schema, run the app, generate and save some test data, quit the app, enable the history bit, and launch again, does the call to load stores fail in some way? and if it succeeds, when you add new data, what does the history show?

are you doing anything with core data in background threads?

I suspect that all apps using NSPersistentCloudKitContainer will behave the same way? If this genuinely surprises end-users, then it's on Apple to address, not you.

start with TechNote 3162: Understanding CloudKit Throttles

then read TN3163: Understanding the synchronization of NSPersistentCloudKitContainer

and finally, read TN3164: Debugging the synchronization of NSPersistentCloudKitContainer

there are several open source libraries that use location… like https://github.com/AndrewHartAR/ARKit-CoreLocation

I've often wondered how NSPersistentCloudKitContainer.share… works, and your example goes a long way to explaining it. When you identify the objects you want to share, they get moved to a new zone. and that zone is what is shared. but the API probably wasn't designed to handle the scenario you describe, so once a record is moved to a shared zone, it doesn't/can't get move to another zone. 2¢