feat(acp): Honor MCP servers from clients like Zed (stdio + http)

[codefromthecrypt]

Summary

Switches to the sacp library and adds support for MCP servers passed from ACP clients.

This means that any ACP editor can portably pass an MCP server to Goose the same way as another agent like Gemini, Codex or Claude.

Why sacp?

• Handler-based API vs manual trait implementation
• Supports bidirectional requests (agent can request permissions FROM client)
• using the symposium crates, because the SDK donated ones aren't published yet.

Notes:

• Bidirectional permission flow: Tool confirmations send RequestPermissionRequest to the client, which responds with approval/denial.
• Http transport: Supports both stdio (required by spec) and http (e.g., kiwi MCP server)
• SSE rejected: Deprecated in rmcp 0.10+

Type of Change

• Feature
• Refactor / Code quality
• Tests

AI Assistance

• This PR was created or reviewed with AI assistance

Testing

• Integration tests:
  • test_acp_with_mcp_http_server: Spins up real MCP HTTP server with sum tool, tests full flow (prompt → tool call → tool result → answer)
• Manual: Zed + kiwi MCP server + goose (on this branch):

  "context_servers": {
    "kiwi": {
      "url": "https://mcp.kiwi.com",
    },
  },
  "agent_servers": {
    "goose": {
      "type": "custom",
      "command": "/Users/codefromthecrypt/oss/goose/target/release/goose",
      "args": ["acp"],
      "env": {},
    },
  },

Related Issues

Closes #6111

[codefromthecrypt]

since this isn't approved yet anyway, i'll await a pending release from sacp that should be going out today and work any changes in. Also, I did the same MCP integration test in another agent and found it was serving the answer 1+1 from memory and not calling tools.

So, I will change the fake MCP server to something an LLM can't guess. (regardless this isnt an issue here as we are pre-canning responses, but I want to set a good example)

[codefromthecrypt]

tested with nvim yetone/avante.nvim#2883

[codefromthecrypt]

bringing this up for review. the next sacp upgrade will be mechanical and not need much review. better to not hold this change hostage to it.

[Copilot]

Pull request overview

This PR switches goose's ACP implementation from the agent-client-protocol library to the sacp (symposium-acp) library, adding support for MCP servers passed from ACP clients. The refactor enables bidirectional permission requests and adds support for both stdio and HTTP transports for MCP servers.

Key changes:

• Replaces agent-client-protocol with sacp library for handler-based API
• Implements bidirectional permission flow for tool confirmations via RequestPermissionRequest
• Adds HTTP transport support for MCP servers (e.g., kiwi MCP server)

Reviewed changes

Copilot reviewed 14 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
crates/goose-cli/src/commands/acp.rs	Complete rewrite to use sacp's handler-based API; adds MCP server conversion and bidirectional permission handling
crates/goose-cli/Cargo.toml	Replaces agent-client-protocol dependency with sacp 9.0.0
crates/goose/Cargo.toml	Adds sacp dev-dependency and rmcp streamable-http-server feature for tests
crates/goose-mcp/Cargo.toml	Updates rmcp from 0.8.1 to 0.10.0
crates/goose/tests/acp_integration_test.rs	Rewrites ACP tests to use sacp; adds HTTP MCP server integration test
crates/goose/tests/common.rs	Extracts shared test binary building logic; adds GOOSE_BINARY constant
crates/goose/tests/mcp_integration_test.rs	Refactors to use shared common module for binary paths
crates/goose/src/permission/permission_confirmation.rs	Adds PartialEq and Eq derives for test assertions
crates/goose/src/agents/extension.rs	Adds PartialEq derive for ExtensionConfig and Envs for test assertions
crates/goose/tests/test_data/*.txt	Adds new test data files for OpenAI mock responses
Cargo.lock	Updates dependencies for sacp, rmcp, tokio, and transitive dependencies

[alexhancock]

why this change? was this one just inconsistent?

[codefromthecrypt]

yeah just to have it match versions. copilot insisted ;)

[codefromthecrypt]

Thanks for the look @alexhancock and happy holidays!