fix: Fix MCP debug client factory compatibility with keyword-only factories

Pass keyword arguments instead of positional arguments to the base_factory
in _DebugHttpxClientFactory.__call__. This resolves a regression introduced
in cl/938200678 where positional arguments were passed to factories that
only accept keyword arguments (e.g., EnvoylopeStreamableHTTPConnectionParams).

Co-authored-by: Kathy Wu <wukathy@google.com>
PiperOrigin-RevId: 938765189

Author: wukath

src/google/adk/tools/mcp_tool/mcp_session_manager.py

@@ -233,7 +233,7 @@ def __call__(
       timeout: httpx.Timeout | None = None,
       auth: httpx.Auth | None = None,
   ) -> httpx.AsyncClient:
-    client = self._base_factory(headers, timeout, auth)
+    client = self._base_factory(headers=headers, timeout=timeout, auth=auth)
     if hasattr(client, 'event_hooks') and isinstance(client.event_hooks, dict):
       client.event_hooks.setdefault('response', []).append(self._response_hook)
     return client

tests/unittests/tools/mcp_tool/test_mcp_session_manager.py

@@ -1430,3 +1430,22 @@ async def test_response_hook_skips_sse_body(self):
     assert record["response_body"] == "<SSE stream>"
     mock_response.aread.assert_not_called()
     await base_client.aclose()
+
+  @pytest.mark.asyncio
+  async def test_debug_factory_passes_keyword_arguments(self):
+    """Test that the debug factory passes keyword arguments to base_factory."""
+    base_client = httpx.AsyncClient()
+
+    # A factory function that only accepts keyword arguments
+    def keyword_only_factory(**kwargs) -> httpx.AsyncClient:
+      assert "headers" in kwargs
+      assert "timeout" in kwargs
+      assert "auth" in kwargs
+      return base_client
+
+    debug_factory = _DebugHttpxClientFactory(keyword_only_factory)
+
+    # Should work when called with positional arguments (which maps them to parameter names)
+    client = debug_factory({"X-Test": "Val"}, None, None)
+    assert client is base_client
+    await base_client.aclose()