Agent Client Protocol

The Agent Client Protocol (ACP) gives code editors and coding agents a single way to talk to each other. An editor is the interactive program a person uses to view and change source code, and a coding agent is a program that uses generative AI to modify code on its own. Instead of a bespoke integration per editor and agent pair, both sides implement one protocol.

Messages are JSON-RPC requests, responses, and notifications. A connection opens with an initialize exchange that negotiates a protocolVersion, and the capabilities exchanged in that handshake decide which optional messages each side supports. The current stable protocol version is 1.

Wire compatibility and artifact versions are tracked separately. The Rust crate version and the JSON Schema release versions describe the generated artifacts, so two schema releases can describe the same wire-compatible protocol while organizing, naming, or emitting definitions differently for code generation. Consumers read the negotiated protocolVersion for wire shape and the artifact versions for compatibility with the generated Rust and schema outputs.

The repository root crate, agent-client-protocol-schema, carries the Rust data model for wire messages: request, response, notification, JSON-RPC envelope, and protocol-version types. Implementations in Rust start instead from the higher-level agent-client-protocol runtime crate, which provides the client and agent APIs.