Only include stream_options when streaming (#519)

Closes #518

Author: rm-openai

src/agents/models/openai_chatcompletions.py

@@ -528,7 +528,9 @@ async def _fetch_response(
         reasoning_effort = model_settings.reasoning.effort if model_settings.reasoning else None
         store = _Converter.get_store_param(self._get_client(), model_settings)
 
-        stream_options = _Converter.get_stream_options_param(self._get_client(), model_settings)
+        stream_options = _Converter.get_stream_options_param(
+            self._get_client(), model_settings, stream=stream
+        )
 
         ret = await self._get_client().chat.completions.create(
             model=self.model,
@@ -591,8 +593,11 @@ def get_store_param(cls, client: AsyncOpenAI, model_settings: ModelSettings) ->
 
     @classmethod
     def get_stream_options_param(
-        cls, client: AsyncOpenAI, model_settings: ModelSettings
+        cls, client: AsyncOpenAI, model_settings: ModelSettings, stream: bool
     ) -> dict[str, bool] | None:
+        if not stream:
+            return None
+
         default_include_usage = True if cls.is_openai(client) else None
         include_usage = (
             model_settings.include_usage