[Modern] mutation underfetching/overfetching

I know that concept of fatQuery is not in modern. But I struggle how to organize the schemas in mutations to make sure I am not under/over fetching. When some object is just updated, its safe just to ask for everything that might have changed.. and thats fine most of the time - in worst case its just some overfetching.

But what if new object is added to the list? How do I know which components are using which fields? And what happens if I don't fetch all relevant fields which some component requires - does it show broken data or somehow refetch?

What strategy you use, just ask always for all fields to avoid under fetching?

Sorry not posting this on SO, but I think its actionable and eventually should be closed with some documentation PR.