Python: preserve MCP connection errors during cleanup

python/packages/core/agent_framework/_mcp.py

@@ -642,6 +642,11 @@ async def _safe_close_exit_stack(self) -> None:
                 )
             else:
                 raise
+        except Exception as e:
+            if type(e).__name__ == "ExceptionGroup":
+                logger.warning("Could not cleanly close MCP exit stack due to cleanup error group. Error: %s", e)
+            else:
+                raise
         except asyncio.CancelledError:
             logger.warning("Could not cleanly close MCP exit stack because the lifecycle owner task was cancelled.")
 

python/packages/core/tests/core/test_mcp.py

@@ -3891,6 +3891,33 @@ async def test_mcp_tool_safe_close_handles_cancelled_error():
     mock_exit_stack.aclose.assert_called_once()
 
 
+async def test_mcp_tool_safe_close_handles_cleanup_exception_group():
+    """Cleanup task groups should not hide the original connect failure."""
+    import builtins
+    from contextlib import AsyncExitStack
+
+    exception_group_type = getattr(builtins, "ExceptionGroup", None)
+    if exception_group_type is None:
+        pytest.skip("ExceptionGroup is not available on this Python version")
+
+    tool = MCPStreamableHTTPTool(
+        name="test",
+        url="http://example.com/mcp",
+        load_tools=False,
+        load_prompts=False,
+    )
+
+    mock_exit_stack = AsyncMock(spec=AsyncExitStack)
+    mock_exit_stack.enter_async_context = AsyncMock(side_effect=ConnectionRefusedError("down"))
+    mock_exit_stack.aclose = AsyncMock(side_effect=exception_group_type("cleanup failed", [RuntimeError("reader")]))
+    tool._exit_stack = mock_exit_stack
+
+    with pytest.raises(ToolException, match="Failed to connect to MCP server"):
+        await tool.__aenter__()
+
+    mock_exit_stack.aclose.assert_called_once()
+
+
 async def test_connect_sets_logging_level_when_logger_level_is_set():
     """Test that connect() sets the MCP server logging level when the logger level is not NOTSET."""