Not sure if this is elided or not, but I think the most crucial improvement we could make is annotation of field reliability, which is why I suggested above that we add an Unreliable-Field: field, or something to that effect (whenever Metadata-Version is > 2.1, we’d assume anything not annotated as such is static). This is necessary to distinguish between “did not specify this field” and “this field was specified but in such a way that we cannot guarantee that it will be invariant between builds”.