Agent Client Protocol

The Agent Client Protocol (ACP) standardizes communication between code editors (interactive programs for viewing and editing source code) and coding agents (programs that use generative AI to autonomously modify code).

Learn more at agentclientprotocol.com.

This repository is the official Rust SDK for ACP. It provides crates for building clients, agents, and proxies, plus a conductor that orchestrates chains of proxies between an editor and an agent so that behavior can be extended without modifying the agent itself.

Crates

Core SDK

• agent-client-protocol – Roles (Client, Agent, Proxy, Conductor), connection builders, handlers, and protocol types.
• agent-client-protocol-http – HTTP/SSE and WebSocket transports.
• agent-client-protocol-rmcp – Integration with the rmcp MCP SDK.
• agent-client-protocol-derive – Derive macros used by the core crate.

Native MCP-over-ACP support is currently opt-in through the core crate's unstable_mcp_over_acp feature. Standalone MCP servers need no ACP transport feature; the rmcp integration exposes a matching passthrough feature when those servers are attached to ACP. Stable protocol v1 supports per-session and global proxy attachment. Draft protocol v2 supports the same two attachment scopes when both unstable_protocol_v2 and unstable_mcp_over_acp are enabled: Proxy.v2().with_mcp_server(...) injects a global declaration into each supported session setup request, while v2::SessionBuilder::with_mcp_server(...) attaches a server to one new session and v2::ResumeSessionBuilder::with_mcp_server(...) attaches one while resuming. With unstable_session_fork, v2::ForkSessionBuilder::with_mcp_server(...) attaches one while forking. Successful v2 attachments remain active for the connection lifetime, and all three builders expose on_proxy_session_start to forward proxied setup without coupling later session events to that response.

Proxy orchestration

• agent-client-protocol-conductor – Binary and library that manages chains of proxy components.
• agent-client-protocol-polyfill – Compatibility proxies, including adapting native MCP-over-ACP declarations to HTTP for agents that cannot consume them directly.
• agent-client-protocol-trace-viewer – Interactive sequence-diagram viewer for conductor trace files.

Patterns, examples, and testing

• agent-client-protocol-cookbook – Practical patterns for clients, agents, and proxies, rendered as rustdoc.
• agent-client-protocol-test – Shared test utilities and fixtures.
• yopo – "You Only Prompt Once", an example client.

Documentation

• API reference for individual crates is on docs.rs/agent-client-protocol.
• Design and architecture documentation lives in the mdbook at agentclientprotocol.github.io/rust-sdk. Source is in md/.
• Draft protocol v2 setup, version-typed connections, and high-level session usage are covered in Protocol V2. To run a complete v2 agent/client pair first, use the Runnable V2 Quickstart.

Every connection names its protocol version: Client.v1(), Agent.v1(), and Proxy.v1() start stable-v1 connections, and their .v2() counterparts select the draft-v2 API. The matching types live in agent_client_protocol::v1 and agent_client_protocol::v2, which export the same names (ConnectionTo, Builder, Responder, SessionBuilder, ...). With unstable_protocol_v2, use Proxy.protocol_router() to expose separate strict v1 and v2 proxy implementations as one component. Custom raw routing infrastructure can use Builder::new(role), which applies no protocol-version guard.

Integrations

• Protocol schema and documentation
• Agents
• Clients
• Official Libraries
  • Kotlin: acp-kotlin – supports JVM, other targets are in progress
  • Rust: agent-client-protocol - See the stable-v1 agent and client, or the draft-v2 agent and client examples
  • TypeScript: @agentclientprotocol/sdk - See examples/
• Community Libraries

Pull Requests

Pull requests should intend to close an existing issue.

Issues

• Bug Reports: If you notice a bug in the protocol, please file an issue and we will be in touch.
• Protocol Suggestions: If you'd like to propose additions or changes to the protocol, please start a discussion first. We want to make sure proposed suggestions align well with the project. If accepted, we can have a conversation around the implementation of these changes. Once that is complete, we will create an issue for pull requests to target.

License

By contributing, you agree that your contributions will be licensed under the Apache 2.0 License.