Python: fix(core): Honor tool_choice parameter passed to agent.run() and chat client methods

python/packages/core/agent_framework/_clients.py

@@ -101,7 +101,7 @@ async def get_response(
         stop: str | Sequence[str] | None = None,
         store: bool | None = None,
         temperature: float | None = None,
-        tool_choice: ToolMode | Literal["auto", "required", "none"] | dict[str, Any] | None = "auto",
+        tool_choice: ToolMode | Literal["auto", "required", "none"] | dict[str, Any] | None = None,
         tools: ToolProtocol
         | Callable[..., Any]
         | MutableMapping[str, Any]
@@ -160,7 +160,7 @@ def get_streaming_response(
         stop: str | Sequence[str] | None = None,
         store: bool | None = None,
         temperature: float | None = None,
-        tool_choice: ToolMode | Literal["auto", "required", "none"] | dict[str, Any] | None = "auto",
+        tool_choice: ToolMode | Literal["auto", "required", "none"] | dict[str, Any] | None = None,
         tools: ToolProtocol
         | Callable[..., Any]
         | MutableMapping[str, Any]
@@ -501,7 +501,7 @@ async def get_response(
         stop: str | Sequence[str] | None = None,
         store: bool | None = None,
         temperature: float | None = None,
-        tool_choice: ToolMode | Literal["auto", "required", "none"] | dict[str, Any] | None = "auto",
+        tool_choice: ToolMode | Literal["auto", "required", "none"] | dict[str, Any] | None = None,
         tools: ToolProtocol
         | Callable[..., Any]
         | MutableMapping[str, Any]
@@ -596,7 +596,7 @@ async def get_streaming_response(
         stop: str | Sequence[str] | None = None,
         store: bool | None = None,
         temperature: float | None = None,
-        tool_choice: ToolMode | Literal["auto", "required", "none"] | dict[str, Any] | None = "auto",
+        tool_choice: ToolMode | Literal["auto", "required", "none"] | dict[str, Any] | None = None,
         tools: ToolProtocol
         | Callable[..., Any]
         | MutableMapping[str, Any]
@@ -688,12 +688,18 @@ def _prepare_tool_choice(self, chat_options: ChatOptions) -> None:
             chat_options: The chat options to prepare.
         """
         chat_tool_mode = chat_options.tool_choice
-        if chat_tool_mode is None or chat_tool_mode == ToolMode.NONE or chat_tool_mode == "none":
+        # Explicitly disabled: clear tools and set to NONE
+        if chat_tool_mode == ToolMode.NONE or chat_tool_mode == "none":
             chat_options.tools = None
             chat_options.tool_choice = ToolMode.NONE
             return
+        # No tools available: set to NONE regardless of requested mode
         if not chat_options.tools:
             chat_options.tool_choice = ToolMode.NONE
+        # Tools available but no explicit mode: default to AUTO
+        elif chat_tool_mode is None:
+            chat_options.tool_choice = ToolMode.AUTO
+        # Tools available with explicit mode: preserve the mode
         else:
             chat_options.tool_choice = chat_tool_mode
 

python/packages/core/agent_framework/openai/_chat_client.py

@@ -205,8 +205,8 @@ def _prepare_options(self, messages: MutableSequence[ChatMessage], chat_options:
             run_options.pop("tools", None)
             run_options.pop("parallel_tool_calls", None)
             run_options.pop("tool_choice", None)
-        # tool choice when `tool_choice` is a dict with single key `mode`, extract the mode value
-        if (tool_choice := run_options.get("tool_choice")) and len(tool_choice.keys()) == 1:
+        # tool_choice: ToolMode serializes to {"type": "tool_mode", "mode": "..."}, extract mode
+        if (tool_choice := run_options.get("tool_choice")) and isinstance(tool_choice, dict) and "mode" in tool_choice:
             run_options["tool_choice"] = tool_choice["mode"]
 
         # response format

python/packages/core/agent_framework/openai/_responses_client.py

@@ -435,8 +435,8 @@ async def _prepare_options(
         else:
             run_options.pop("parallel_tool_calls", None)
             run_options.pop("tool_choice", None)
-        # tool choice when `tool_choice` is a dict with single key `mode`, extract the mode value
-        if (tool_choice := run_options.get("tool_choice")) and len(tool_choice.keys()) == 1:
+        # tool_choice: ToolMode serializes to {"type": "tool_mode", "mode": "..."}, extract mode
+        if (tool_choice := run_options.get("tool_choice")) and isinstance(tool_choice, dict) and "mode" in tool_choice:
             run_options["tool_choice"] = tool_choice["mode"]
 
         # additional properties

python/packages/core/tests/core/test_agents.py

@@ -632,3 +632,93 @@ def echo_thread_info(text: str, **kwargs: Any) -> str:  # type: ignore[reportUnk
     assert result.text == "done"
     assert captured.get("has_thread") is True
     assert captured.get("has_message_store") is True
+
+
+async def test_chat_agent_tool_choice_run_level_overrides_agent_level(
+    chat_client_base: Any, ai_function_tool: Any
+) -> None:
+    """Verify that tool_choice passed to run() overrides agent-level tool_choice."""
+    from agent_framework import ChatOptions, ToolMode
+
+    captured_options: list[ChatOptions] = []
+
+    # Store the original inner method
+    original_inner = chat_client_base._inner_get_response
+
+    async def capturing_inner(
+        *, messages: MutableSequence[ChatMessage], chat_options: ChatOptions, **kwargs: Any
+    ) -> ChatResponse:
+        captured_options.append(chat_options)
+        return await original_inner(messages=messages, chat_options=chat_options, **kwargs)
+
+    chat_client_base._inner_get_response = capturing_inner
+
+    # Create agent with agent-level tool_choice="auto" and a tool (tools required for tool_choice to be meaningful)
+    agent = ChatAgent(chat_client=chat_client_base, tool_choice="auto", tools=[ai_function_tool])
+
+    # Run with run-level tool_choice="required"
+    await agent.run("Hello", tool_choice="required")
+
+    # Verify the client received tool_choice="required", not "auto"
+    assert len(captured_options) >= 1
+    assert captured_options[0].tool_choice == "required"
+    assert captured_options[0].tool_choice == ToolMode.REQUIRED_ANY
+
+
+async def test_chat_agent_tool_choice_agent_level_used_when_run_level_not_specified(
+    chat_client_base: Any, ai_function_tool: Any
+) -> None:
+    """Verify that agent-level tool_choice is used when run() doesn't specify one."""
+    from agent_framework import ChatOptions, ToolMode
+
+    captured_options: list[ChatOptions] = []
+
+    original_inner = chat_client_base._inner_get_response
+
+    async def capturing_inner(
+        *, messages: MutableSequence[ChatMessage], chat_options: ChatOptions, **kwargs: Any
+    ) -> ChatResponse:
+        captured_options.append(chat_options)
+        return await original_inner(messages=messages, chat_options=chat_options, **kwargs)
+
+    chat_client_base._inner_get_response = capturing_inner
+
+    # Create agent with agent-level tool_choice="required" and a tool
+    agent = ChatAgent(chat_client=chat_client_base, tool_choice="required", tools=[ai_function_tool])
+
+    # Run without specifying tool_choice
+    await agent.run("Hello")
+
+    # Verify the client received tool_choice="required" from agent-level
+    assert len(captured_options) >= 1
+    assert captured_options[0].tool_choice == "required"
+    assert captured_options[0].tool_choice == ToolMode.REQUIRED_ANY
+
+
+async def test_chat_agent_tool_choice_none_at_run_preserves_agent_level(
+    chat_client_base: Any, ai_function_tool: Any
+) -> None:
+    """Verify that tool_choice=None at run() uses agent-level default."""
+    from agent_framework import ChatOptions
+
+    captured_options: list[ChatOptions] = []
+
+    original_inner = chat_client_base._inner_get_response
+
+    async def capturing_inner(
+        *, messages: MutableSequence[ChatMessage], chat_options: ChatOptions, **kwargs: Any
+    ) -> ChatResponse:
+        captured_options.append(chat_options)
+        return await original_inner(messages=messages, chat_options=chat_options, **kwargs)
+
+    chat_client_base._inner_get_response = capturing_inner
+
+    # Create agent with agent-level tool_choice="auto" and a tool
+    agent = ChatAgent(chat_client=chat_client_base, tool_choice="auto", tools=[ai_function_tool])
+
+    # Run with explicitly passing None (same as not specifying)
+    await agent.run("Hello", tool_choice=None)
+
+    # Verify the client received tool_choice="auto" from agent-level
+    assert len(captured_options) >= 1
+    assert captured_options[0].tool_choice == "auto"

python/packages/core/tests/core/test_types.py

@@ -844,6 +844,54 @@ def test_chat_options_and(ai_function_tool, ai_tool) -> None:
     assert options3.additional_properties.get("p") == 1
 
 
+def test_chat_options_and_tool_choice_override() -> None:
+    """Test that tool_choice from other takes precedence in ChatOptions merge."""
+    # Agent-level defaults to "auto"
+    agent_options = ChatOptions(model_id="gpt-4o", tool_choice="auto")
+    # Run-level specifies "required"
+    run_options = ChatOptions(tool_choice="required")
+
+    merged = agent_options & run_options
+
+    # Run-level should override agent-level
+    assert merged.tool_choice == "required"
+    assert merged.model_id == "gpt-4o"  # Other fields preserved
+
+
+def test_chat_options_and_tool_choice_none_in_other_uses_self() -> None:
+    """Test that when other.tool_choice is None, self.tool_choice is used."""
+    agent_options = ChatOptions(tool_choice="auto")
+    run_options = ChatOptions(model_id="gpt-4.1")  # tool_choice is None
+
+    merged = agent_options & run_options
+
+    # Should keep agent-level tool_choice since run-level is None
+    assert merged.tool_choice == "auto"
+    assert merged.model_id == "gpt-4.1"
+
+
+def test_chat_options_and_tool_choice_with_tool_mode() -> None:
+    """Test ChatOptions merge with ToolMode objects."""
+    agent_options = ChatOptions(tool_choice=ToolMode.AUTO)
+    run_options = ChatOptions(tool_choice=ToolMode.REQUIRED_ANY)
+
+    merged = agent_options & run_options
+
+    assert merged.tool_choice == ToolMode.REQUIRED_ANY
+    assert merged.tool_choice == "required"  # ToolMode equality with string
+
+
+def test_chat_options_and_tool_choice_required_specific_function() -> None:
+    """Test ChatOptions merge with required specific function."""
+    agent_options = ChatOptions(tool_choice="auto")
+    run_options = ChatOptions(tool_choice=ToolMode.REQUIRED(function_name="get_weather"))
+
+    merged = agent_options & run_options
+
+    assert merged.tool_choice == "required"
+    assert merged.tool_choice.required_function_name == "get_weather"
+
+
 # region Agent Response Fixtures