ACP (three protocols)

ACP refers to three unrelated protocols from three organisations at three different steps. Zed's Agent Client Protocol connects editors to coding agents (Act). IBM's Agent Communication Protocol was an agent-to-agent protocol, archived in August 2025 and merged into A2A (Coordinate, defunct). The OpenAI/Stripe Agentic Commerce Protocol lets an agent buy from a merchant (Pay). Published guides routinely state facts about one as though they applied to all; the widely repeated claim that "ACP merged into A2A" is true only of IBM's. A fourth, IBM's Agent Commerce Protocol, could not be verified as a distinct specification on 2026-09-05.