decision

What a SemanticCache.lookup of this prompt would decide, up to — but not including — the verifier.

null means it would be served (a hit). Otherwise it is the MissReason a lookup would report, with one caveat: MissReason.REJECTED_BY_VERIFIER never appears here, because explain does not run the Verifier. So a null here with a verifier configured means "the guards would pass it; the verifier still gets the last word." Every other outcome matches a real lookup exactly.