Agent Communication Protocol (ACP)

A REST-native performative messaging protocol introduced by IBM as part of its **BeeAI** open-source agent runtime. ACP optimizes for **local multi-agent systems** — high-throughput internal coordination between agents running on the same host or within the same data-center rack — using multi-part messages, asynchronous streaming, and rich observability primitives (per-message tracing, latency histograms, message-graph reconstruction).

A2A is optimized for cross-organizational, cross-vendor agent collaboration; the trust model assumes you are reaching across administrative boundaries. ACP solves a different problem: when you have a dozen specialized agents (planner, retriever, code-writer, code-reviewer, executor, summarizer) running together as a *single application*, you want low-latency message passing and deep observability, not OAuth-mediated handshakes. ACP is the local-multi-agent dual of A2A.