Add configure_logging opt-out to MCPServer (#1656)

src/mcp/server/mcpserver/server.py

@@ -82,7 +82,8 @@
 )
 from mcp.server.mcpserver.tools import Tool, ToolManager
 from mcp.server.mcpserver.utilities.context_injection import find_context_parameter
-from mcp.server.mcpserver.utilities.logging import configure_logging, get_logger
+from mcp.server.mcpserver.utilities.logging import configure_logging as _configure_logging
+from mcp.server.mcpserver.utilities.logging import get_logger
 from mcp.server.request_state import RequestStateBoundary, RequestStateSecurity
 from mcp.server.sse import SseServerTransport
 from mcp.server.stdio import stdio_server
@@ -174,6 +175,7 @@ def __init__(
         extensions: Sequence[Extension] | None = None,
         debug: bool = False,
         log_level: Literal["DEBUG", "INFO", "WARNING", "ERROR", "CRITICAL"] = "INFO",
+        configure_logging: bool = True,
         warn_on_duplicate_resources: bool = True,
         warn_on_duplicate_tools: bool = True,
         warn_on_duplicate_prompts: bool = True,
@@ -256,8 +258,10 @@ def __init__(
             self._token_verifier = ProviderTokenVerifier(auth_server_provider)
         self._custom_starlette_routes: list[Route] = []
 
-        # Configure logging
-        configure_logging(self.settings.log_level)
+        # Configure logging (opt-out via configure_logging=False for applications
+        # that embed MCPServer and manage their own logging setup; see #1656)
+        if configure_logging:
+            _configure_logging(self.settings.log_level)
 
         self._extensions: list[Extension] = []
         for extension in extensions or ():

tests/server/mcpserver/test_configure_logging.py

@@ -0,0 +1,35 @@
+from unittest.mock import patch
+
+from mcp.server.mcpserver import MCPServer
+
+
+class TestConfigureLogging:
+    def test_default_calls_configure_logging(self):
+        """By default, `MCPServer` configures logging on construction (the
+        pre-existing behavior, preserved for backwards compatibility)."""
+        with patch("mcp.server.mcpserver.server._configure_logging") as spy:
+            MCPServer("test-server")
+
+        spy.assert_called_once_with("INFO")
+
+    def test_configure_logging_false_skips_configuration(self):
+        """`configure_logging=False` opts a server out of calling
+        `_configure_logging` (and therefore `logging.basicConfig()`)
+        entirely, so an application can safely manage its own logging
+        setup without the server racing to configure the root logger
+        first.
+
+        See: https://github.com/modelcontextprotocol/python-sdk/issues/1656
+        """
+        with patch("mcp.server.mcpserver.server._configure_logging") as spy:
+            MCPServer("test-server", configure_logging=False)
+
+        spy.assert_not_called()
+
+    def test_configure_logging_true_still_calls_configure_logging(self):
+        """Explicitly passing `configure_logging=True` behaves the same as
+        the default (sanity check for the new parameter's positive case)."""
+        with patch("mcp.server.mcpserver.server._configure_logging") as spy:
+            MCPServer("test-server", configure_logging=True, log_level="DEBUG")
+
+        spy.assert_called_once_with("DEBUG")