fix(mcp): detect server death, fail loudly instead of raw ClosedResourceError#6298
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immuhammadfurqan wants to merge 4 commits into
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fix(mcp): detect server death, fail loudly instead of raw ClosedResourceError#6298immuhammadfurqan wants to merge 4 commits into
immuhammadfurqan wants to merge 4 commits into
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…rceError When an MCP server process dies mid-session, nothing linked the transport death to `_run_client`, which stayed parked on `await self._closing_ev.wait()`. As a result `initialized` kept returning True, the `finally` cleanup never ran, and every subsequent tool call fell through to `self._client.call_tool(...)` and raised a raw `anyio.ClosedResourceError` (empty message) into the LLM tool-call turn — a silent failure for the rest of the session, with no reconnect and no error surfaced to the agent. Detect a dead transport (`anyio.ClosedResourceError`/`BrokenResourceError`, or `McpError(CONNECTION_CLOSED)`) at the tool-call boundary: raise a clear `ToolError` and tear the dead client down so `initialized` reports False and the parked `_run_client` unwinds and runs its cleanup. `_run_client` now treats a post-startup connection close as an expected shutdown rather than an unexpected error. Normal tool-error results are unaffected and do not tear the connection down. This is the "fail loudly" fix; automatic reconnect is left as a follow-up. Closes livekit#6291
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Closes #6291
This PR detects dead MCP transports at tool invocation time, tears down the dead client, and raises a clear ToolError instead of raw anyio errors. It also adds regression tests for dead connection detection and normal tool error propagation.