Local-only fields in mutation responses

I’m currently using local-only fields (via the @client directive & field policies) to create a friendly descriptor for one of my types (a “Part”).

For queries, everything works beautifully. However, when using a mutation to create a new Part, those same local-only fields are not available. I can fetch the descriptor with cache.readFragment, but that’s a workaround I’d rather not be forced to do.

Am I missing something simple to enable access to those local-only fields as a result of a mutation?

I’m working on a simple reproduction now, but figured I might just be missing something obvious.