ExperimentalReadonly ExperimentalexpiresReadonly ExperimentalkindReadonly ExperimentalobservedReadonly ExperimentalreferenceStable evidence identity. Common credential-shaped forms are rejected, but callers must still treat accepted values as potentially sensitive and must not supply credentials, signed URLs, or secrets.
Optional Readonly ExperimentalsourceEvidence identity only; when present it must match the enclosing source profile.
Readonly Experimentaltruth
Exclusive freshness boundary.