Audit Chain Checkpoints for Human-AI Governance Substrates: Non-Repudiation via GLOBAL-Signed Chain State Snapshots | APR-Lite Phase 15 — Technical Note

This record documents Phase 15 of APR‑Lite, a cryptographic governance layer designed to preserve human decision authority over AI‑influenced outputs in regulated environments. Phase 15 extends the cryptographic stack introduced in earlier phases to provide non‑repudiation of the audit history itself by notarizing the chain that records signed governance activity at verifiable points in time. Phase 14 established that designated governance activity produces independently verifiable proof artifacts. Phase 15 adds a second layer: the sequence that embeds those artifacts is periodically captured and attested by a distinguished authority. Each checkpoint is a signed assertion of chain state at a moment in time; an adversary who forges or reconstructs a divergent history cannot present a valid attestation over that falsified state without access to the relevant signing material. Checkpoint creation is modeled as governance activity in its own right and passes through the existing signing machinery, so that the act of notarization is itself subject to the same proof regime as other high‑authority behavior. The audit‑verification surface is extended to incorporate these attestations and to report on the integrity of both the underlying linkage structure and the superimposed checkpoints as distinct but related concerns. In this construction, the linkage structure establishes internal consistency of the recorded sequence, while checkpoints provide external non‑repudiation of its evolution over time. Phase 15 achieved full success on its smoke‑test suite for the extended history‑attestation pipeline in worker version 8.2.0‑p15.0. A more detailed treatment, including formalization of the two‑layer proof model and its operational envelope, is available under restricted access to qualified requesters.