And maybe an entity having @Transient properties which affect input of any index field (be it via @Field of custom bridges) should always be considered dirty, at least by default?

I'm thinking for example of transient properties which are meant to index the current timestamp, or similar data which isn't even computed from other fields.

Another case is with bridges like TikaBridge: this will open external resource (e.g. a PDF on disk) and there's no guarantee that this content wasn't updated. We assume that developers wouldn't allow that in a "correct" design, but some people might want to express a different requirement as a property of the bridge.