Agent Client Protocol

Zed introduced Agent Client Protocol in August 2025 under Apache-2.0, JSON-RPC 2.0 over stdio, framed against the precedent of Language Server Protocol. The specification page states the problem: "AI coding agents and editors are tightly coupled but interoperability isn't the default." The costs it lists are integration overhead, limited compatibility, and developer lock-in, since "choosing an agent often means accepting their available interfaces". The arithmetic argument: N+M integrations rather than N×M.

The protocol has left its creator's orbit. The specification site lists Zed Industries and JetBrains at the same level, alongside an ACP Registry, RFDs, Community, Publications, Updates and Brand, with libraries in Kotlin, Java, Python, Rust and TypeScript. Its navigation shows v1 (Latest) and v2 (Draft), not the "ACP 1.2" that circulates elsewhere.

Block's Berd desktop application connects to the goose runtime through Agent Client Protocol; Buzz binds goose, Codex and Claude Code through buzz-acp, a harness that also translates ACP to MCP. The relation to MCP is close by construction: Agent Client Protocol re-uses MCP's JSON representations where possible, adds types for agentic coding UX such as diff display, and defaults to Markdown so editors need not render HTML.

Franciska Dethlefsen wrote on Zed's blog in May 2026 that "ACP is an open protocol… so that your editor is never locked into one provider's pricing decisions", after Anthropic announced separate credits for third-party agent usage, a change suspended a month later. Full support for remote agents over HTTP or WebSocket remains declared a work in progress.