07c7ed3752
Step 6 of opt-in ACP v2 support, option (b) as decided in review. Stacked on #1255: both change the `initialize` line of every v2 golden file. Once #1255 merges, I'll merge `main` into this branch so the diff shows fork alone. Nothing changes on ACP v1. ## Why fork, then resume The agent's v1 fork copies the transcript into a new session and returns only its id. Until a client resumes or loads the fork, a prompt to it fails with "Session not found", and the request's `mcpServers` go unused. AIR, the only v1 client that forks, loads the fork right away. The fork RFD describes the response as "the same as `session/new`", with config options, and the request as taking `session/load`'s options. So on v2 the client gets a session it can prompt at once: - `v1ForkSessionRequests` (`src/v2/session.ts`) builds the v1 fork, then a v1 resume of the fork without replay, with the request's `cwd`, `additionalDirectories` and `mcpServers`. The request's `_meta` goes to the fork alone. - The response is the new `sessionId` plus the resume's `configOptions`. The available commands follow as an update, as for `session/new` and `session/resume`. - `capabilities.session.fork: {}` is advertised. Each fork starts its own Claude Code process, as `session/new` does. The draft doesn't say whether a fork must be live, so that's recorded as feedback for it. ## Verification - An end-to-end test forks a session with an HTTP MCP server, checks the forked Claude Code session resumes the copied transcript with that server, and prompts the fork without a `session/resume`. - Removing the resume, the MCP servers or the capability fails tests. - Every v2 golden file changes on its `initialize` line only, which gains `session.fork`. - Build, lint and all 2411 tests pass.
ACP adapter for the Claude Agent SDK
Use Claude Agent SDK from ACP-compatible clients!
This tool implements an ACP agent by using the official Claude Agent SDK, supporting:
- Context @-mentions
- Images
- Tool calls (with permission requests)
- Compact file changes through the negotiated AIR diff patch extension
- Following
- Edit review
- TODO lists
- Nested subagent transcripts
- Interactive (and background) terminals
- Custom Slash commands
- Client MCP servers
/mcpin the chat: the MCP server status as a list. The adapter runs/mcp reconnect,/mcp enable, and/mcp disablethrough the SDK control API, because Claude Code refuses them in SDK mode. A reconnect of an ACP server that needs authentication starts MCP OAuth through URL elicitation- Session-scoped long-running goals for AIR through the goal extension under
_meta.jetbrains.air.goal - Structured errors, recovery, and warnings through the opt-in session failure extension
- Concrete model and effort defaults through the opt-in recommended config value extension
- Tool permission presentation, editable choices, and durable effects through the permission extension
- One fact per field in every tool call report, as the ACP tool call contract defines
- All AIR extensions, capabilities, and
_metakeys: AIR extensions
Learn more about the Agent Client Protocol.
To try changes that have landed on main but are not released yet, install from the
preview channel — every push to main publishes one. See
docs/RELEASES.md.
npm install @agentclientprotocol/claude-agent-acp@preview
Subagent sessions
Subagents are exposed only after bilateral capability negotiation. Until the released ACP SDKs
preserve the draft clientCapabilities.subagents field, a supporting client may advertise
nativeSubagentSessions in _meta.jetbrains.air.capabilities; the adapter mirrors the capability
in its initialize response. The canonical field remains supported and takes precedence once it is
available. Without either client signal, Agent/Task lifecycle keeps its legacy ordinary ACP
tool-call representation and child interactions stay on the root session. Clients that use the
historical _meta["subagent-transcript"] capability or forwardSubagentText session option retain
the flattened child transcript behavior. See AIR extensions.
Contribution Policy
This project does not require a Contributor License Agreement (CLA). Instead, contributions are accepted under the following terms:
By contributing to this project, you agree that your contributions will be licensed under the Apache License, Version 2.0. You affirm that you have the legal right to submit your work, that you are not including code you do not have rights to, and that you understand contributions are made without requiring a Contributor License Agreement (CLA).