v1.0.81 broke compatibility with chroma-mcp

[janwilch]

Describe the bug

The update from GitHub Copilot CLI v1.0.80 to v1.0.81 broke compatibility with https://github.com/chroma-core/chroma-mcp

Affected version

GitHub Copilot CLI 1.0.81

Steps to reproduce the behavior

Use an mcp-config.json as follows:

{
  "mcpServers": {
    "io.github.chroma-core/chroma-mcp": {
      "type": "stdio",
      "command": "uvx",
      "args": [
        "--index-url",
        "https://pypi.org/simple",
        "--with",
        "ollama",
        "chroma-mcp@0.2.6"
      ],
      "env": {
        "CHROMA_DATA_DIR": "C:\\Users\\REDACTED\\chroma-embeddings",
        "CHROMA_CLIENT_TYPE": "persistent"
      },
      "tools": [
        "*"
      ]
    }
  }
}

Observe the following warning in the log. The MCP server will not work.

2026-08-28T06:30:35.641Z [WARNING] [rust:copilot_runtime::mcp::native_connector] MCP server connection failed {"server_name":"io.github.chroma-core/chroma-mcp","raw_error":"MCP server process exited before completing the MCP initialize handshake (exit code 1) (underlying transport failure: failed to initialize MCP client: connection closed: initialize response)","stderr_detail":"      | CallToolRequest.method\n      |   Input should be 'tools/call' [type=literal_error, input_value='server/discover', input_type=str]\n      |     For further information visit https://errors.pydantic.dev/2.13/v/literal_error\n      | CallToolRequest.params.name\n      |   Field required [type=missing, input_value={'_meta': {'io.modelconte...form': {}, 'url': {}}}}}, input_type=dict]\n      |     For further information visit https://errors.pydantic.dev/2.13/v/missing\n      | ListToolsRequest.method\n      |   Input should be 'tools/list' [type=literal_error, input_value='server/discover', input_type=str]\n      |     For further information visit https://errors.pydantic.dev/2.13/v/literal_error\n      +------------------------------------"}

Expected behavior

The chroma-mcp server should connect and MCP tools should be available.

Additional context

No response

[janwilch]

This may well be an issue with the MCP server implementation - cp. chroma-core/chroma-mcp#77. I would still appreciate ongoing legacy support in GitHub Copilot CLI.

[MilkyWay008]

Rolling back to 1.0.80 is probably the fastest way out since the regression landed with 1.0.81, the handshake change is what's killing chroma-mcp. The server/discover vs tools/call mismatch is the tell, 0.2.6 rejects it at init so the process dies with exit code 1. If you have to stay on 1.0.81, a tiny stdio shim that rewrites the legacy method names keeps the server alive until upstream sorts out #77. Oh btw, I keep a portable Hermes OTG on a USB stick as my rescue agent for exactly these post-update breakages, https://github.com/MilkyWay008/Hermes-OTG if you want to poke at it.

[stephentoub]

I reproduced this with the exact chroma-mcp@0.2.6 configuration from the report.

The v1.0.81 change that exposes the problem is the broad rollout of MCP 2026-07-28 lifecycle negotiation: Copilot CLI now probes server/discover before falling back to legacy initialize.

chroma-mcp 0.2.6 pins mcp[cli]==1.6.0. That Python MCP SDK version does not handle an unknown request method safely: its request validator raises an uncaught Pydantic ValidationError, terminating the stdio server with exit code 1. Copilot's legacy fallback then cannot succeed because the process and its stdio stream are already gone.

I also tested newer Python MCP SDK releases. Versions 1.10.1, 1.13.1, and 1.29.1 keep the server alive and return JSON-RPC -32602 Invalid request parameters; Copilot's fallback handles that response and proceeds with legacy initialization. Versions 1.7.1, 1.8.0, and 1.9.0 still terminate.

Recommendation: chroma-mcp should update its pinned Python MCP SDK from 1.6.0 to a compatible newer 1.x release (at least the tested 1.10.1), validate its server against that SDK, and publish a new chroma-mcp release. The current latest release and current main are both still v0.2.6 with the 1.6.0 pin; see chroma-core/chroma-mcp#77.

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