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fix: catch KeyboardInterrupt in run() for clean Ctrl+C exit #2943

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fix: catch KeyboardInterrupt in run() for clean Ctrl+C exit #2943

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19 changes: 12 additions & 7 deletions src/mcp/server/mcpserver/server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -291,13 +291,18 @@ def run(
if transport not in TRANSPORTS.__args__: # type: ignore # pragma: no cover
raise ValueError(f"Unknown transport: {transport}")

match transport:
case "stdio":
anyio.run(self.run_stdio_async)
case "sse": # pragma: no cover
anyio.run(lambda: self.run_sse_async(**kwargs))
case "streamable-http": # pragma: no cover
anyio.run(lambda: self.run_streamable_http_async(**kwargs))
try:
match transport:
case "stdio":
anyio.run(self.run_stdio_async)
case "sse": # pragma: no cover
anyio.run(lambda: self.run_sse_async(**kwargs))
case "streamable-http": # pragma: no cover
anyio.run(lambda: self.run_streamable_http_async(**kwargs))
except KeyboardInterrupt:
# Ctrl+C should exit cleanly without a traceback when running
# a server from the terminal (e.g. stdio transport).
pass

async def _handle_list_tools(
self, ctx: ServerRequestContext[LifespanResultT], params: PaginatedRequestParams | None
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17 changes: 17 additions & 0 deletions tests/server/test_stdio.py
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Original file line number Diff line number Diff line change
Expand Up @@ -169,3 +169,20 @@ async def lifespan(server: MCPServer) -> AsyncIterator[None]:
assert events == ["setup", "cleanup"]
response = jsonrpc_message_adapter.validate_json(captured.getvalue().decode().strip())
assert response == JSONRPCResponse(jsonrpc="2.0", id=1, result={})


def test_mcpserver_run_catches_keyboard_interrupt(monkeypatch: pytest.MonkeyPatch) -> None:
"""Ctrl+C during `run()` should exit cleanly without a traceback.

Regression test for #2663: when running a stdio server from the terminal,
KeyboardInterrupt (Ctrl+C) should not produce a multi-frame traceback
through anyio.run() → asyncio.runners.
"""

def mock_anyio_run(*args: object, **kwargs: object) -> None:
raise KeyboardInterrupt()

monkeypatch.setattr(anyio, "run", mock_anyio_run)

# Should not raise — KeyboardInterrupt is caught inside run()
MCPServer(name="KeyboardInterruptServer").run("stdio")