fix(llms): narrow _is_reasoning_model to not match gpt-5.x variants (#4746)

Co-authored-by: Claude <noreply@anthropic.com>

mem0/llms/base.py

@@ -54,14 +54,19 @@ class LLMBase(ABC):
             "o1", "o1-preview", "o3-mini", "o3",
             "gpt-5", "gpt-5o", "gpt-5o-mini", "gpt-5o-micro",
         }
-        
-        if model.lower() in reasoning_models:
-            return True
-        
+
         model_lower = model.lower()
-        if any(reasoning_model in model_lower for reasoning_model in ["gpt-5", "o1", "o3"]):
+        # Strip provider prefixes (e.g. "openai/o3-mini" -> "o3-mini")
+        base_model = model_lower.rsplit("/", 1)[-1]
+
+        if base_model in reasoning_models:
             return True
-            
+
+        # Match o1/o3 family with prefixes (o1-2024-12-17, o3-2025-04-16)
+        # but NOT gpt-5.x variants (gpt-5.4-mini supports temperature)
+        if any(base_model.startswith(prefix) for prefix in ["o1-", "o1.", "o3-", "o3."]):
+            return True
+
         return False
 
     def _get_supported_params(self, **kwargs) -> Dict:

tests/llms/test_openai.py

@@ -285,6 +285,49 @@ def test_store_sent_when_explicitly_false(mock_openai_client):
     assert call_kwargs["store"] is False
 
 
+def test_gpt5_mini_not_classified_as_reasoning(mock_openai_client):
+    """Test that gpt-5.4-mini is NOT treated as a reasoning model.
+
+    gpt-5.4-mini supports temperature and other standard params.
+    The previous substring match on "gpt-5" incorrectly stripped these.
+    Regression test for https://github.com/mem0ai/mem0/issues/4738
+    """
+    config = OpenAIConfig(model="gpt-5.4-mini", temperature=0.1)
+    llm = OpenAILLM(config)
+    messages = [{"role": "user", "content": "Hello"}]
+
+    mock_response = Mock()
+    mock_response.choices = [Mock(message=Mock(content="Response"))]
+    mock_openai_client.chat.completions.create.return_value = mock_response
+
+    llm.generate_response(messages)
+
+    call_kwargs = mock_openai_client.chat.completions.create.call_args
+    # gpt-5.4-mini should pass through temperature, not strip it
+    assert call_kwargs[1].get("temperature") == 0.1
+
+
+def test_is_reasoning_model_classification(mock_openai_client):
+    """Test _is_reasoning_model correctly classifies known models."""
+    config = OpenAIConfig(model="gpt-4.1")
+    llm = OpenAILLM(config)
+
+    # Reasoning models — should return True
+    assert llm._is_reasoning_model("o1") is True
+    assert llm._is_reasoning_model("o3-mini") is True
+    assert llm._is_reasoning_model("o3") is True
+    assert llm._is_reasoning_model("gpt-5") is True
+    assert llm._is_reasoning_model("o1-preview") is True
+    assert llm._is_reasoning_model("o1-2024-12-17") is True
+    assert llm._is_reasoning_model("openai/o3-mini") is True
+
+    # Non-reasoning models — should return False
+    assert llm._is_reasoning_model("gpt-5.4-mini") is False
+    assert llm._is_reasoning_model("gpt-5.4") is False
+    assert llm._is_reasoning_model("gpt-4.1") is False
+    assert llm._is_reasoning_model("gpt-4.1-nano-2025-04-14") is False
+
+
 def test_callback_with_tools(mock_openai_client):
     mock_callback = Mock()
     config = OpenAIConfig(model="gpt-4.1-nano-2025-04-14", response_callback=mock_callback)