ci: add stdio smoke test to verify LF-only wire format on all platforms#15
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shigechika merged 3 commits intomainfrom May 1, 2026
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ci: add stdio smoke test to verify LF-only wire format on all platforms#15shigechika merged 3 commits intomainfrom
shigechika merged 3 commits intomainfrom
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The Windows CI job previously ran only pytest unit tests, which exercise pure-Python logic and never spawn the MCP server. This meant the CRLF regression (modelcontextprotocol/python-sdk#2433) would not be caught. Add tests/test_stdio_smoke.py: spawns keycloak-mcp as a subprocess, sends a JSON-RPC initialize request, and asserts the response line is terminated with LF (\n) not CRLF (\r\n). Runs on every matrix entry (ubuntu-latest × 3.10/3.12/3.13 + windows-latest × 3.12) via the existing `uv run pytest -v` step — no CI workflow changes required. Closes #3 Co-Authored-By: Claude Sonnet 4.6 <[email protected]>
…tion On Windows, sys.stdout defaults to text mode which translates \n to \r\n, corrupting the NDJSON wire format (modelcontextprotocol/python-sdk#2433). Use msvcrt.setmode to force binary mode on the underlying file descriptors before mcp.run() so the MCP SDK's writes pass through unchanged. Co-Authored-By: Claude Sonnet 4.6 <[email protected]>
msvcrt.setmode() cannot prevent the \n -> \r\n translation because it happens in Python's TextIOWrapper layer before reaching the OS fd level. The MCP SDK creates TextIOWrapper(sys.stdout.buffer, encoding="utf-8") with the default newline=None, which on Windows translates \n to \r\n. Work around this by rebuilding sys.stdout around a _CRStripper RawIOBase that strips \r\n -> \n before each os.write(), so the SDK's subsequent TextIOWrapper.write() calls are corrected at the raw I/O level. Co-Authored-By: Claude Sonnet 4.6 <[email protected]>
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Summary
tests/test_stdio_smoke.py: spawnskeycloak-mcpas a subprocess, sends a JSON-RPCinitializerequest, and asserts the response line is terminated with\nnot\r\n.uv run pytest -vstep picks up the new file automatically, so it runs on every matrix entry (ubuntu-latest × 3.10/3.12/3.13 + windows-latest × 3.12).initializeis handled entirely by the MCP framework before any tool dispatch.What this guards against
modelcontextprotocol/python-sdk#2433 —
stdio_server()on Windows emitted\r\ninstead of\n, corrupting the NDJSON wire format. The previous Windows CI job only ran unit tests and would not have caught this regression.Test plan
uv run pytest tests/test_stdio_smoke.py -v— passes locally (macOS)Closes #3
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