AI Assistance Disclosure

This contribution was developed with AI assistance (Claude / Anthropic Claude Code).

Summary

Fix #2663: When running a stdio server from the terminal and pressing Ctrl+C, the server previously produced a noisy multi-frame traceback through anyio.run() → asyncio.runners → anyio.streams.memory.receive. This change wraps the anyio.run() call in MCPServer.run() with a try/except KeyboardInterrupt so the server exits cleanly.

Changes

src/mcp/server/mcpserver/server.py: +7 lines (try/except + comment), −5 lines (indent shift)
tests/server/test_stdio.py: +14 lines (1 new test)

Verification Process

1. Forked → cloned to local sandbox
2. Applied fix: try/except KeyboardInterrupt in run()
3. Wrote test mocking anyio.run to raise KeyboardInterrupt
4. Ran stdio test suite: 5/5 passed (4 existing + 1 new)
5. Ruff format + lint: all checks passed
6. Zero new pragma/type:ignore/noqa annotations

Test Results

tests/server/test_stdio.py::test_stdio_server_round_trips_messages_over_injected_streams PASSED
tests/server/test_stdio.py::test_stdio_server_invalid_utf8 PASSED
tests/server/test_stdio.py::test_mcpserver_run_stdio_serves_until_stdin_closes PASSED
tests/server/test_stdio.py::test_mcpserver_run_stdio_runs_lifespan_cleanup_after_stdin_closes PASSED
tests/server/test_stdio.py::test_mcpserver_run_catches_keyboard_interrupt PASSED [NEW]

Cross-Validation

Closes #2663