diff --git a/.gitignore b/.gitignore
index e66cd370..bee4b907 100644
--- a/.gitignore
+++ b/.gitignore
@@ -146,4 +146,4 @@ cython_debug/
 # CAI files
 .cai/
 .vscode/
-cai_env/
+
diff --git a/tests/core/test_openai_chatcompletions.py b/tests/core/test_openai_chatcompletions.py
index 89a00627..afb45526 100644
--- a/tests/core/test_openai_chatcompletions.py
+++ b/tests/core/test_openai_chatcompletions.py
@@ -174,3 +174,119 @@ async def test_get_response_with_tool_call(monkeypatch) -> None:
     assert fn_call_item.name == "do_thing"
     assert fn_call_item.arguments == "{'x':1}"
 
+@pytest.mark.asyncio
+async def test_fetch_response_non_stream(monkeypatch) -> None:
+    """
+    Verify that `_fetch_response` builds the correct OpenAI API call when not
+    streaming and returns the ChatCompletion object directly. We supply a
+    dummy ChatCompletion through a stubbed OpenAI client and inspect the
+    captured kwargs.
+    """
+
+    # Dummy completions to record kwargs
+    class DummyCompletions:
+        def __init__(self) -> None:
+            self.kwargs: dict[str, Any] = {}
+
+        async def create(self, **kwargs: Any) -> Any:
+            self.kwargs = kwargs
+            return chat
+
+    class DummyClient:
+        def __init__(self, completions: DummyCompletions) -> None:
+            self.chat = type("_Chat", (), {"completions": completions})()
+            self.base_url = httpx.URL("http://fake")
+
+    msg = ChatCompletionMessage(role="assistant", content="ignored")
+    choice = Choice(index=0, finish_reason="stop", message=msg)
+    chat = ChatCompletion(
+        id="resp-id",
+        created=0,
+        model="fake",
+        object="chat.completion",
+        choices=[choice],
+    )
+    completions = DummyCompletions()
+    dummy_client = DummyClient(completions)
+    model = OpenAIChatCompletionsModel(model=cai_model, openai_client=dummy_client)  # type: ignore
+    # Execute the private fetch with a system instruction and simple string input.
+    with generation_span(disabled=True) as span:
+        result = await model._fetch_response(
+            system_instructions="sys",
+            input="hi",
+            model_settings=ModelSettings(),
+            tools=[],
+            output_schema=None,
+            handoffs=[],
+            span=span,
+            tracing=ModelTracing.DISABLED,
+            stream=False,
+        )
+   
+    # Ensure expected args were passed through to OpenAI client.
+    kwargs = completions.kwargs
+    assert kwargs["stream"] is False
+    assert kwargs["store"] is True
+    assert kwargs["model"] == cai_model
+    assert kwargs["messages"][0]["role"] == "system"
+    assert kwargs["messages"][0]["content"] == "sys"
+    assert kwargs["messages"][1]["role"] == "user"
+    # Defaults for optional fields become the NOT_GIVEN sentinel
+    assert kwargs["tools"] is NOT_GIVEN
+    assert kwargs["tool_choice"] is NOT_GIVEN
+    assert kwargs["response_format"] is NOT_GIVEN
+    assert kwargs["stream_options"] is NOT_GIVEN
+
+
+@pytest.mark.asyncio
+async def test_fetch_response_stream(monkeypatch) -> None:
+    """
+    When `stream=True`, `_fetch_response` should return a bare `Response`
+    object along with the underlying async stream. The OpenAI client call
+    should include `stream_options` to request usage-delimited chunks.
+    """
+    os.environ['CAI_STREAM'] = 'true'
+    async def event_stream() -> AsyncIterator[ChatCompletionChunk]:
+        if False:  # pragma: no cover
+            yield  # pragma: no cover
+
+    class DummyCompletions:
+        def __init__(self) -> None:
+            self.kwargs: dict[str, Any] = {}
+
+        async def create(self, **kwargs: Any) -> Any:
+            self.kwargs = kwargs
+            return event_stream()
+
+    class DummyClient:
+        def __init__(self, completions: DummyCompletions) -> None:
+            self.chat = type("_Chat", (), {"completions": completions})()
+            self.base_url = httpx.URL("http://fake")
+
+    completions = DummyCompletions()
+    dummy_client = DummyClient(completions)
+    model = OpenAIChatCompletionsModel(model=cai_model, openai_client=dummy_client)  # type: ignore
+    with generation_span(disabled=True) as span:
+        response, stream = await model._fetch_response(
+            system_instructions=None,
+            input="hi",
+            model_settings=ModelSettings(),
+            tools=[],
+            output_schema=None,
+            handoffs=[],
+            span=span,
+            tracing=ModelTracing.DISABLED,
+            stream=True,
+        )
+    # Check OpenAI client was called for streaming
+    assert completions.kwargs["stream"] is True
+    assert completions.kwargs["store"] is True
+    assert completions.kwargs["stream_options"] == {"include_usage": True}
+    # Response is a proper openai Response
+    assert isinstance(response, Response)
+    assert response.id == FAKE_RESPONSES_ID
+    assert response.model == cai_model
+    assert response.object == "response"
+    assert response.output == []
+    # We returned the async iterator produced by our dummy.
+    assert hasattr(stream, "__aiter__")
\ No newline at end of file