Ios swift – How can we reliably detect when a user runs out of iCloud storage?

I am using NSPersistentCloudKitContainer, to integrate CoreData with CloudKit.

What I want to achieve is to prompt the user to go to iCloud settings to manage their storage when there is a sync error, and we realize the user doesn’t have enough iCloud storage.

I am using the following code snippet, to monitor the sync progress.

// https://crunchybagel.com/nspersistentcloudkitcontainer/
private func initEventChangedNotification() {
    NotificationCenter.default.addObserver(
        self,
        selector: #selector(eventChangedNotification),
        name: NSPersistentCloudKitContainer.eventChangedNotification,
        object: nil
    )
}

@objc func eventChangedNotification(_ notification: Notification) {
    CoreDataStack.eventChangedNotification(notification)
}

static func eventChangedNotification(_ notification: Notification) {
    guard let event = notification.userInfo?[NSPersistentCloudKitContainer.eventNotificationUserInfoKey] as? NSPersistentCloudKitContainer.Event else {
        return
    }

    if let error = event.error {
        print(">>>> error = (error)")
        if let ckError = error as? CKError {
            print(">>>> ckError.errorCode = (ckError.errorCode)")
            print(">>>> ckError.localizedDescription = (ckError.localizedDescription)")
        }
        
        error_log(error)
        return
    }
    
    let isFinished = event.endDate != nil
    ...
}

I run the above code with my iCloud storage is full.

What I am expecting, is to receive quotaExceeded (Error code 25)

However, what I am receiving is partialfailure (Error code 2)

Here’s the logging

>>>> error = Error Domain=CKErrorDomain Code=2 "(null)"
>>>> ckError.errorCode = 2
>>>> ckError.localizedDescription = The operation couldn’t be completed. (CKErrorDomain error 2.)

However, when I run another app in the same device, using the same iCloud account, this is how it looks like.

1. It is able to detect quotaExceeded (Error code 25)
2. Tapping on ‘Sync now’ triggers the sync operation to run immediately. How are they able to achieve this? I thought we have no control over when the sync runs?

May I know, how can we reliably detect when a user runs out of iCloud storage?

Thank you