bd8a161c2e
Last part of step 4's session baseline for opt-in ACP v2 support (after
#1231–#1235): a v2 `session/resume` can now replay the session's
history. Nothing changes on ACP v1.
## Change
- **Routing.** v2 restores a session with `session/resume` and replays
only when `replayFrom` asks for it. v1 splits that into
`session/resume`, which never replays, and `session/load`, which replays
everything before it responds. That's exactly what v2 requires of
`replayFrom: { type: "start" }`. So `v1RestoreSessionRequest` maps the
v2 request to one of the two. A cursor that starts elsewhere is
rejected, since v1 can only replay from the start.
- **Clearing replayed messages.** The agent replays messages as chunks,
and chunks append. A v2 client may still hold a replayed message, so
before the first replayed chunk of each message, the v2 surface sends
that message with `content: []`. The draft requires that of a message
replayed as chunks. It happens only while that session replays
(`V2ClientConnection.replaying`), and the clear and the chunk go to the
connection together, so nothing comes between them.
- **Prompt ids.** The draft requires a prompt's user message to replay
under the id its `session/prompt` response returned. Since #1226 that id
is the user message's uuid, which Claude Code keeps in the transcript,
so no new code is needed. A test checks it end to end.
## Scenario suite
`session-load-replay` passes, so every scenario now passes on v2. The
status table becomes `V2_STOPS`: the scenarios that stop on v2, which is
empty today and stays as the place for a scenario v2 can't run yet. The
replay golden file shows each message cleared before its chunks, and the
`session/resume` response after the last replayed update.
A replayed Edit or Write shows no diff yet on v2: replay has no
PostToolUse hook. Building it from the transcript is the next PR.
## Verification
- **Replay test:** a live prompt, then resume with replay from a
transcript holding the uuid Claude Code saved. The replayed user message
carries the prompt response's id, each message is cleared before its
chunks, everything arrives before the response, and a live prompt
afterwards gets no clears.
- **Mutations:** each rule fails a test when removed: no clears, clears
that stay on after the replay, a replay served as a plain resume, and
one clear per id rather than per message.
- Build, lint and all 2385 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).