This paper proposes the Sovereign Payment Agent (SPA) model, a conceptual systems governance framework for the controlled deployment of autonomous payment agents within enterprise and regulated financial environments. The framework introduces four primary contributions: a Governance Envelope architecture incorporating Policy-as-Code constraints and audit artifact generation; a five-tier Agent Autonomy Classification (AAC) model; a structured audit artifact standard supporting explainability and regulatory examination; and an adversarial risk architecture addressing prompt injection, signal manipulation, policy drift, and model extraction threats. Also available on SSRN: https: //papers. ssrn. com/sol3/papers. cfm? abstractᵢd=6765180 Part 3 of a 3-paper series on the evolution of intelligent and autonomous payment systems. Part 1: https: //doi. org/10. 5281/zenodo. 20261877Part 2: https: //doi. org/10. 5281/zenodo. 20261969
Avik Nandi (Wed,) studied this question.