I had the same issue when trying to remove a child object from a relationship directly using the context.delete method I fixed my crash by removing the object from the parent object list and saving the context. So instead of doing mainModelContext.delete(child) I am doing // get the child index from the parent parent.childs.remove(at: childIndex) mainModelContext.save() This seems to fix the crash and its also trigger update on the parent model if a view is observing it. My experience with SwiftData so far has been that if you have to modify relationships it's better to do it from parent side. I have encountered crashes or updates not triggering as expected otherwise.