Closed-world authorization treated denial as the end of the interaction. Agents, runtime discovery, delegation, and mission expansion turn denial into the beginning of governance escalation. The draft AuthZEN access request and approval profile standardizes that handoff without standardizing the workflow engines behind it. Client-Initiated Backchannel Authentication (CIBA) is not the answer because the problem is not authentication freshness. It is whether authority should continue under newly discovered runtime conditions.
The new version of AAuth (draft-hardt-aauth-protocol-01) materially changes the earlier comparison. Mission is now first-class in the protocol, with PS-mediated approval, mission-aware token choreography, and governance endpoints. The remaining gap is no longer whether Mission exists, but whether the published model is strong enough to support portable containment rather than just mission correlation and governance hooks.
Open-world OAuth can improve discovery, resource binding, and first-contact trust. That still leaves the harder agent problem: how approved intent becomes bounded authority that stays governed across delegation chains, unfamiliar tools, consent expansion, revocation, and task termination.