I'm looking into rewriting our non-replicated FP as a replicated FP, and I'm running into this as well. I'd like to show some UI that includes information from the database we keep about items, and if I had the NSFileProviderItemIdentifier we give to iOS, I could use that to look up the info. Is there any no way to convert the __fp/fs/docID ID into the original ID?

I am curious why you need to rely on the domain:process mapping though, if you don't mind to share. Thanks for the response! We don't need to rely on domain:process mapping, but I'm trying to understand what we can rely on. For example, each domain is a separate account - things like cookies, caches, etc are probably not to be shared across accounts. I'm looking at the header for NSFileProviderDomain right now, and I see this comment: On the extension side, a separate instance of NSFileProviderExtension will be created for each @c NSFileProviderDomain registered. In that case, the @c NSFileProviderExtension.domain properties will indicate which domain the NSFileProviderExtension belongs to (or nil if none). This is what led me to believe that all of the calls for a particular domain would be routed to a single process. I'm finding that not to be the case - calls for any domain can come to any Files Extension process, which would seem to contradict that comment as I understand it. Is that as expected?