Changing watchOS Deployment Target - What happens to users on old versions

Not a silly question. Any watch that can update to watchOS 7 can also update to watchOS 8, so moving from minOS 7 to minOS 8 won't leave any users behind. They'll need to update their watches to get your app update, but that's something they can and should do. If you set your minOS to watchOS 9 (which is the analog to iOS 16), users on Series 3 watches won't be able to update their OS to that version, and the watch app on their device would be deleted when the iOS app is updated to the version with the dependent watch app that requires watchOS 9. If your watch app were independent, I believe (but have not tested this, so I might be wrong) that the last watchOS 7/8-compatible version of the app would stay on the watch, since app versions are not required to stay in sync in this case.

I have an app currently built for iOS 18 with a companion watchOS app targeting watchOS 10. If I raise the iOS minimum deployment target to iOS 26, users on iOS 18 will no longer be able to update the app (which is fine). My question is about users who have phones running iOS 18 or iOS 26 (and thus can update the app on their iPhone) but have older Apple Watch hardware that cannot run watchOS 11 or later (and thus cannot update the watchOS companion app). • Will these users be able to update the app on their iPhone despite their watch being on an unsupported watchOS version? This would mean the app becomes useless for them. • If they update the app on the iPhone, will the watchOS companion app be removed or become non-functional because the bundled watchOS app requires at least watchOS 11? • How does Apple handle this situation where the iOS app can update but the companion watchOS app is not compatible with the older watch? • Is there any way I can prevent these users from updating the app to the latest version?

Will these users be able to update the app on their iPhone despite their watch being on an unsupported watchOS version? This would mean the app becomes useless for them.

Yes they will. Are you saying that your watch app is the valuable bit, and the iOS app doesn't do anything without the watch app?

If they update the app on the iPhone, will the watchOS companion app be removed or become non-functional because the bundled watchOS app requires at least watchOS 11?

You didn't say whether the watchOS app is independent or not; the older version of an independent watchOS app would stay on the watch if a person updates the iOS app, as independence does mean that the two sides can be updated independently and the versions are not guaranteed to match. If the person deletes the watchOS app and tries to re-install it, however, I do not think they will be able to get it back once your update is live in the App Store. If the watchOS app requires the iOS app to be installed to run, yes it will be deleted if a person updates the iOS app with the new minOS if the watch that's paired with the phone can't update to at least watchOS 11.

Is there any way I can prevent these users from updating the app to the latest version?

Not that I can think of, aside from communicating that watchOS 11 will be required with the next version of the app.

I see, thank you. That's what I suspected but hoped there would be a better solution.

Yes, they will. Are you saying that your watch app is the valuable bit, and the iOS app doesn't do anything without the watch app?

Well, it's a fitness/workout app, and most users use the Watch to actually work out. The phone app is just for setup and checking your data. (workout is also possible but users prefer to use the watch)

You didn't say whether the watchOS app is independent or not.

Yes, my app is not independent.

Not that I can think of, aside from communicating that watchOS 11 will be required with the next version of the app.

Communicating the requirement of watchOS 11 (regardless of the channel) won't be noticed by all users running watchOS 10. Hence, many auto-updated iOS apps will render the app useless to most of these users.

To conclude: The only "proper" workaround is to make the watch app independent, so users on older hardware can keep the older version. Correct?

(I'm aware that making the app independent will imply a whole bunch of other issues, especially when it comes to data sync and DB schemes...)