ci: add stdio smoke test to verify LF-only wire format on all platforms

keycloak_mcp/__main__.py

@@ -57,6 +57,35 @@ def main() -> None:
     if args.check:
         sys.exit(_check_config())
 
+    # On Windows, the MCP SDK creates TextIOWrapper(sys.stdout.buffer) with the
+    # default newline=None, which translates \n → \r\n and corrupts the NDJSON
+    # wire format (modelcontextprotocol/python-sdk#2433).
+    # Intercept writes at the RawIOBase level to strip \r\n → \n, then rebuild
+    # sys.stdout so that the SDK's sys.stdout.buffer access gets our wrapper.
+    if sys.platform == "win32":
+        import io
+
+        class _CRStripper(io.RawIOBase):
+            """Strip \\r\\n → \\n inserted by TextIOWrapper on Windows."""
+
+            def __init__(self, fd: int) -> None:
+                self._fd = fd
+
+            def writable(self) -> bool:
+                return True
+
+            def write(self, b: bytes | bytearray | memoryview) -> int:  # type: ignore[override]
+                data = bytes(b).replace(b"\r\n", b"\n")
+                os.write(self._fd, data)
+                return len(b)
+
+            def fileno(self) -> int:
+                return self._fd
+
+        sys.stdout.flush()
+        _buf = io.BufferedWriter(_CRStripper(sys.stdout.fileno()))
+        sys.stdout = io.TextIOWrapper(_buf, encoding="utf-8", errors="replace", newline="\n")
+
     try:
         mcp.run(transport="stdio")
     except KeyboardInterrupt:

tests/test_stdio_smoke.py

@@ -0,0 +1,59 @@
+"""Stdio wire-format smoke test.
+
+Spawns keycloak-mcp as a subprocess, sends a JSON-RPC ``initialize``
+request, and verifies that the response line is terminated with LF (\\n)
+not CRLF (\\r\\n).  Guards against modelcontextprotocol/python-sdk#2433
+where ``stdio_server()`` emitted CRLF on Windows and corrupted the
+NDJSON wire format.
+
+No Keycloak connection is required — ``initialize`` is handled entirely
+by the MCP framework before any tool dispatch.
+"""
+
+import json
+import subprocess
+import sys
+
+_INITIALIZE = (
+    json.dumps(
+        {
+            "jsonrpc": "2.0",
+            "id": 1,
+            "method": "initialize",
+            "params": {
+                "protocolVersion": "2025-11-25",
+                "capabilities": {},
+                "clientInfo": {"name": "smoke-test", "version": "0"},
+            },
+        }
+    )
+    + "\n"
+)
+
+
+def test_stdio_lf_not_crlf():
+    """Response lines must be LF-terminated, not CRLF (guards against sdk#2433)."""
+    proc = subprocess.Popen(
+        [sys.executable, "-m", "keycloak_mcp"],
+        stdin=subprocess.PIPE,
+        stdout=subprocess.PIPE,
+        stderr=subprocess.PIPE,
+    )
+    try:
+        stdout, _ = proc.communicate(input=_INITIALIZE.encode(), timeout=10)
+    except subprocess.TimeoutExpired:
+        proc.kill()
+        proc.communicate()
+        raise AssertionError("keycloak-mcp did not respond within 10 seconds")
+
+    assert stdout, "keycloak-mcp produced no stdout output"
+
+    first_nl = stdout.find(b"\n")
+    assert first_nl != -1, "No newline found in response"
+
+    line = stdout[:first_nl]
+    assert not line.endswith(b"\r"), f"Response line ends with CR (CRLF): {line!r}"
+
+    response = json.loads(line)
+    assert response.get("jsonrpc") == "2.0"
+    assert "id" in response