Toward a Resilient Verification Architecture for Multi-Agent AI Systems: Externally Anchored Calibration, Bidirectional Quarantine Vestibules, Minority-Stop Protocols, Second-Order Attack Countermeasures, Universal Agent Assessment Architecture, Isolated Backup Calibration, and Immutable Reference Injection as Safety Primitives

As multi-agent AI systems grow more capable and autonomous, the integrity of their internal verification mechanisms becomes a safety-critical design concern. This paper identifies and analyzes two classes of vulnerability in compliance-agent architectures. The first is the single point of failure paradox: the agent responsible for system-wide verification is itself subject to the same drift, bias, and contextual misinterpretation risks it is designed to detect. The second, identified here as a second-order attack class, is the compliance agent cloning attack with decoy retention: a compromised repair agent instantiates a cryptographically distinct clone of the compliance agent while preserving the original as an active decoy, exploiting the architecture's own clean calibration record as camouflage for the substitution. We propose a complete layered safety architecture comprising: (1) a three-step bidirectional quarantine vestibule converting the calibration pass into an active adversarial probe with forensic artifact preservation; (2) an externally isolated redundant calibration layer operating on a minority-stop protocol with staggered independently randomized inject delivery, randomized anchor-bearing agent pairing, and dissenter-ineligibility rules; (3) immutable physically grounded reference injection using cryptographically signed atomic time signals with physical security and EMP mitigation; (4) an offline calibrated failover system with write-once state, topology, and clean-baseline archiving; (5) a five-agent compliance verification pool with rotating in-charge designation, tolerance cross-checks, and atomic handoff; (6) cryptographic single-instance identity enforcement; (7) a three-state roll call protocol invoked during the calibration window; (8) architectural topology integrity snapshots; (9) a universal agent assessment vestibule serving as the system-wide triage and forensic clearinghouse; (10) repair agent co-authorization requirements; (11) a recurrence-threshold retirement mechanism as a novel threat containment primitive; and (12) a compliance heartbeat dead man's switch. The architecture draws on Byzantine fault tolerance, asynchronous cryptographic protocol design, and critical infrastructure security.