SoK: Blockchain Agent-to-Agent Payments

Venue: BCRA 2026 / Blockchain: Research and Applications, full paper, 2026. Preprint: arXiv:2604.03733 Status: Accepted as a full paper at BCRA 2026.

Abstract

Agentic AI systems are increasingly expected to coordinate autonomous workflows and interact with other agents, including in settings that require financial transactions. This paper systematizes blockchain-based Agent-to-Agent (A2A) payments and studies how payment mechanisms can support trustworthy interactions among unknown or untrusted agents.

The paper organizes A2A payment systems around a four-stage lifecycle: discovery, authorization, execution, and accounting. It categorizes representative blockchain-based designs at each stage and identifies key open challenges, including weak intent binding, misuse under valid authorization, payment-service decoupling, and limited accountability. The work further outlines research directions for cross-stage consistency, behavior-aware control, and compositional payment workflows across agent ecosystems.