Nomotic, Inc. This document specifies the AGTP identifier chain: a layered model of identifiers that together produce a tamper-evident chain of custody across every action an AGTP agent takes. The chain is composed of identifiers already established in the AGTP draft family (Agent-ID, Owner-ID, Session-ID, Task-ID, and the Attribution-Record envelope of base AGTP) together with a small set of additional identifiers introduced by this document (Request-ID, Response-ID, Action-ID, Evaluation-ID, Decision-ID, Audit-ID). The Audit-ID is the cryptographic hash of an extended Attribution-Record and provides the per-agent hash chain that links every action an agent takes back to its Agent Genesis. This document defines the identifiers, how they extend the existing Attribution-Record envelope, the construction of the hash chain, and the verification procedure by which a regulator, auditor, or counterparty reconstructs the chain end to end. The identifier chain is the regulatory backbone of AGTP. Without it, the protocol can record that something happened but cannot prove who caused it, what authorized it, or what was decided.