Add default include of reasoning.encrypted_content for store=False to prevent reasoning errors

src/agents/models/openai_responses.py

@@ -259,6 +259,10 @@ async def _fetch_response(
         include_set: set[str] = set(converted_tools.includes)
         if model_settings.response_include is not None:
             include_set.update(model_settings.response_include)
+
+        if model_settings.store is False and model_settings.response_include is None:
+            include_set.add("reasoning.encrypted_content")
+
         if model_settings.top_logprobs is not None:
             include_set.add("message.output_text.logprobs")
         include = cast(list[ResponseIncludable], list(include_set))

tests/test_store_response_include.py

@@ -0,0 +1,50 @@
+import pytest
+from openai.types.responses.response_usage import InputTokensDetails, OutputTokensDetails
+
+from agents import ModelSettings, ModelTracing, OpenAIResponsesModel
+
+
+class DummyResponses:
+    async def create(self, **kwargs):
+        self.kwargs = kwargs
+
+        class DummyResponse:
+            id = "dummy"
+            output = []
+            usage = type(
+                "Usage",
+                (),
+                {
+                    "input_tokens": 0,
+                    "output_tokens": 0,
+                    "total_tokens": 0,
+                    "input_tokens_details": InputTokensDetails(cached_tokens=0),
+                    "output_tokens_details": OutputTokensDetails(reasoning_tokens=0),
+                },
+            )()
+
+        return DummyResponse()
+
+
+class DummyClient:
+    def __init__(self):
+        self.responses = DummyResponses()
+
+
+@pytest.mark.allow_call_model_methods
+@pytest.mark.asyncio
+async def test_store_false_includes_encrypted_reasoning():
+    client = DummyClient()
+    model = OpenAIResponsesModel(model="gpt-5", openai_client=client)  # type: ignore
+    await model.get_response(
+        system_instructions=None,
+        input="hi",
+        model_settings=ModelSettings(store=False),
+        tools=[],
+        output_schema=None,
+        handoffs=[],
+        tracing=ModelTracing.DISABLED,
+        previous_response_id=None,
+    )
+    include = set(client.responses.kwargs["include"])
+    assert "reasoning.encrypted_content" in include