I had same problem. Solution for me was make xcdatamodel shared for both app (in my case it’s not standalone app for watch, but extension).
So just check the box for share this model for both app:
Also set class generation to Cathegory/Extension or Manual, because you need a little bit different implementation of entity class for iOS and WatchOS. If someone know how to use one class and checking which OS call the instance it will be perfect.
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