After updating to watchOS 27, some users of my app can no longer launch the watch app. The watch shows:
"[App] Needs to Be Updated — The developer of this app needs to update it to work with watchOS 27."
The shipping version is not the problem. My current App Store release contains both arm64_32 and arm64 slices in the watch app and its extension, and launches correctly on watchOS 27 when freshly installed. Affected users already have the current version on iPhone. Archives going back to December 2022 also contain arm64.
The fix, in both cases so far, is for the user to remove and reinstall the watch app: Watch.app → My Watch → [app] → toggle "Show App on Apple Watch" off, wait for the icon to disappear, then back on. After that it launches normally on the same device and OS version.
My working theory is that the installed copy is thinned at install time. A watch that installed the app under an earlier watchOS received an arm64_32-only copy, which persisted through later app updates and OS updates. watchOS 27's 64-bit requirement then rejects it. A reinstall on 27 pulls the arm64 slice. One affected user has had the app installed on an Ultra 2 since December 2023, which fits.
I have not been able to verify the contents of the installed copy on a user device, so this is inference rather than confirmed.
Two things I'd like to know:
Is anyone else seeing this? If so, what was the install history of the affected devices? Is there any supported way to force a watch app to be re-downloaded, or to detect from the iPhone app that the watch copy is in this state? Right now users have no indication that a reinstall fixes it, and the message points at the developer.
Feedback filed as FB24834097