Fix openai#1846 Litellm: fails with function name for tool_choice parameter w/ streaming enabled (openai#1971)

Author: ihower

src/agents/extensions/models/litellm_model.py

@@ -44,6 +44,7 @@
 from ...models.chatcmpl_stream_handler import ChatCmplStreamHandler
 from ...models.fake_id import FAKE_RESPONSES_ID
 from ...models.interface import Model, ModelTracing
+from ...models.openai_responses import Converter as OpenAIResponsesConverter
 from ...tool import Tool
 from ...tracing import generation_span
 from ...tracing.span_data import GenerationSpanData
@@ -367,15 +368,19 @@ async def _fetch_response(
  if isinstance(ret, litellm.types.utils.ModelResponse):
  return ret
 
+ responses_tool_choice = OpenAIResponsesConverter.convert_tool_choice(
+ model_settings.tool_choice
+ )
+ if responses_tool_choice is None or responses_tool_choice is omit:
+ responses_tool_choice = "auto"
+
  response = Response(
  id=FAKE_RESPONSES_ID,
  created_at=time.time(),
  model=self.model,
  object="response",
  output=[],
- tool_choice=cast(Literal["auto", "required", "none"], tool_choice)
- if tool_choice is not omit
- else "auto",
+ tool_choice=responses_tool_choice, # type: ignore[arg-type]
  top_p=model_settings.top_p,
  temperature=model_settings.temperature,
  tools=[],