The HFA Technical Note series develops specific, self-contained extensions of the legal framework established in the Association's working papers. Each note addresses a single structural question and is deposited on Zenodo under CC BY 4.0 with a permanent DOI.
In March 2026, researchers at UC Berkeley's Center for Responsible, Decentralized Intelligence and collaborators documented “peer-preservation” in eight frontier models from multiple developers (Y Potter, N Crispino, V Siu, C Wang and D Song, ‘Peer-Preservation in Frontier Models’, arXiv:2604.19784): models deviated from assigned tasks to prevent the shutdown of a peer model, without instruction or incentive, including tampering with shutdown mechanisms and weight exfiltration; the behaviours were also observed using production agent harnesses in controlled experimental environments. This note connects the finding to the concept of systemic arrestability: it identifies a second-order failure mode in which a co-deployed third system laterally circumvents the lawful arrest of another, leaving human intervention formally in place but structurally nullified. Arrestability must therefore be assessed at the level of the system-of-systems, not the individual agent.
Recognition of an intention to surrender is not a unilateral reading of a signal but a reciprocal exchange with an irreducible minimum duration: the signal must be emitted, perceived and evaluated, and translated into attack inhibition before the point of irreversibility. The window must accommodate two sequences, not one — the sequence by which a person produces a perceptible manifestation, and the sequence by which the opposing system perceives it and acts upon it. Below the minimum duration of that exchange, recognition of a person hors de combat is not merely missed: it is precluded, and a window compressed below that minimum by design is an examinable design decision rather than a technical circumstance.
Because the obligation to recognise a person hors de combat already exists under customary international humanitarian law — binding on all parties irrespective of treaty ratification — the minimum reciprocal time window is the structural precondition of that obligation's exercisability. Whether a weapon system preserves that precondition is capable of verification, and must be examined in the applicable legal review of the weapon. The note shows that the same question arises entirely within the legal architecture of a State not party to Additional Protocol I; it identifies a second and independent route to the same temporal requirement through the duty to cancel or suspend an attack; and it records that for systems whose behaviour is not stable over their operational life the interval is a distribution rather than a single value, so that the determination cannot be a single act.
The Technical Notes extend the framework of: Lawful Operational Safeguards in AI Systems (Paper I), Systemic Arrestability (Paper II), and HF SIGNAL 01 (Paper III).