Fix mcp tool cloning for handoff pattern (#1883)

Author: moonbox3

python/packages/core/agent_framework/_workflows/_handoff.py

@@ -80,6 +80,14 @@ def _clone_chat_agent(agent: ChatAgent) -> ChatAgent:
     options = agent.chat_options
     middleware = list(agent.middleware or [])
 
+    # Reconstruct the original tools list by combining regular tools with MCP tools.
+    # ChatAgent.__init__ separates MCP tools into _local_mcp_tools during initialization,
+    # so we need to recombine them here to pass the complete tools list to the constructor.
+    # This makes sure MCP tools are preserved when cloning agents for handoff workflows.
+    all_tools = list(options.tools) if options.tools else []
+    if agent._local_mcp_tools:
+        all_tools.extend(agent._local_mcp_tools)
+
     return ChatAgent(
         chat_client=agent.chat_client,
         instructions=options.instructions,
@@ -101,7 +109,7 @@ def _clone_chat_agent(agent: ChatAgent) -> ChatAgent:
         store=options.store,
         temperature=options.temperature,
         tool_choice=options.tool_choice,  # type: ignore[arg-type]
-        tools=list(options.tools) if options.tools else None,
+        tools=all_tools if all_tools else None,
         top_p=options.top_p,
         user=options.user,
         additional_chat_options=dict(options.additional_properties),

python/packages/core/tests/workflow/test_handoff.py

@@ -3,13 +3,15 @@
 from collections.abc import AsyncIterable, AsyncIterator
 from dataclasses import dataclass
 from typing import Any, cast
+from unittest.mock import MagicMock
 
 import pytest
 
 from agent_framework import (
     AgentRunResponse,
     AgentRunResponseUpdate,
     BaseAgent,
+    ChatAgent,
     ChatMessage,
     FunctionCallContent,
     HandoffBuilder,
@@ -20,6 +22,8 @@
     WorkflowEvent,
     WorkflowOutputEvent,
 )
+from agent_framework._mcp import MCPTool
+from agent_framework._workflows._handoff import _clone_chat_agent
 
 
 @dataclass
@@ -368,3 +372,32 @@ async def async_termination(conv: list[ChatMessage]) -> bool:
     user_messages = [msg for msg in final_conv_list if msg.role == Role.USER]
     assert len(user_messages) == 2
     assert termination_call_count > 0
+
+
+async def test_clone_chat_agent_preserves_mcp_tools() -> None:
+    """Test that _clone_chat_agent preserves MCP tools when cloning an agent."""
+    mock_chat_client = MagicMock()
+
+    mock_mcp_tool = MagicMock(spec=MCPTool)
+    mock_mcp_tool.name = "test_mcp_tool"
+
+    def sample_function() -> str:
+        return "test"
+
+    original_agent = ChatAgent(
+        chat_client=mock_chat_client,
+        name="TestAgent",
+        instructions="Test instructions",
+        tools=[mock_mcp_tool, sample_function],
+    )
+
+    assert hasattr(original_agent, "_local_mcp_tools")
+    assert len(original_agent._local_mcp_tools) == 1
+    assert original_agent._local_mcp_tools[0] == mock_mcp_tool
+
+    cloned_agent = _clone_chat_agent(original_agent)
+
+    assert hasattr(cloned_agent, "_local_mcp_tools")
+    assert len(cloned_agent._local_mcp_tools) == 1
+    assert cloned_agent._local_mcp_tools[0] == mock_mcp_tool
+    assert len(cloned_agent.chat_options.tools) == 1