fix: invalid model setting when passing prompt to Agent

Author: seratch

src/agents/models/openai_responses.py

@@ -306,7 +306,7 @@ async def _fetch_response(
             previous_response_id=self._non_null_or_not_given(previous_response_id),
             conversation=self._non_null_or_not_given(conversation_id),
             instructions=self._non_null_or_not_given(system_instructions),
-            model=self.model,
+            model=self.model if prompt is None else NOT_GIVEN,
             input=list_input,
             include=include,
             tools=converted_tools_payload,

tests/test_openai_responses.py

@@ -3,6 +3,7 @@
 from typing import Any
 
 import pytest
+from openai import NOT_GIVEN
 from openai.types.responses import ResponseCompletedEvent
 
 from agents import ModelSettings, ModelTracing, __version__
@@ -63,3 +64,35 @@ def __init__(self):
 
     assert "extra_headers" in called_kwargs
     assert called_kwargs["extra_headers"]["User-Agent"] == expected_ua
+
+
+@pytest.mark.allow_call_model_methods
+@pytest.mark.asyncio
+async def test_prompt_id_omits_model_parameter():
+    called_kwargs: dict[str, Any] = {}
+
+    class DummyResponses:
+        async def create(self, **kwargs):
+            nonlocal called_kwargs
+            called_kwargs = kwargs
+            return get_response_obj([])
+
+    class DummyResponsesClient:
+        def __init__(self):
+            self.responses = DummyResponses()
+
+    model = OpenAIResponsesModel(model="gpt-4", openai_client=DummyResponsesClient())  # type: ignore[arg-type]
+
+    await model.get_response(
+        system_instructions=None,
+        input="hi",
+        model_settings=ModelSettings(),
+        tools=[],
+        output_schema=None,
+        handoffs=[],
+        tracing=ModelTracing.DISABLED,
+        prompt={"id": "pmpt_123"},
+    )
+
+    assert called_kwargs["prompt"] == {"id": "pmpt_123"}
+    assert called_kwargs["model"] is NOT_GIVEN