Apple has announced that one of iOS 9’s big new features, App Thinning (or “app slicing”), has been delayed due to an issue with iOS 9. App Thinning was announced at WWDC as a way to help trim down the size of large applications by letting developers mark assets for each specific type of device. When users download the app, the App Store will determine which device they have and only require them to download the assets necessary to run on their device.
While TestFlight has supported the feature for a few weeks, Apple says the public version of iOS 9 will not support it until a later update due to a problem with the way iCloud handles backups.
The issue was explained in a post on Apple’s developer center.
App slicing is currently unavailable for iOS 9 apps due to an issue affecting iCloud backups created from iOS 9 where some apps from the App Store would only restore to the same model of iOS device.
When a customer downloads your iOS 9 app, they will get the Universal version of your app, rather than the variant specific for their device type. TestFlight will continue to deliver variants for your internal testers. App slicing will be reenabled with a future software update. No action is needed by you at this time.
This may explain why many app updates that were released over the past few weeks have been mysteriously reissued by Apple since yesterday morning, though the company hasn’t confirmed the connection.
App Thinning will continue to function on TestFlight without any changes, but developers will not be able to distribute sliced versions of their apps on the App Store until a software update fixes the issue.