Fix: Remove stop parameter for o4-mini model

src/crewai/llm.py

@@ -358,7 +358,12 @@ def _prepare_completion_params(
         }
 
         # Remove None values from params
-        return {k: v for k, v in params.items() if v is not None}
+        params = {k: v for k, v in params.items() if v is not None}
+
+        if "o4-mini" in self.model:
+            params.pop("stop", None)
+
+        return params
 
     def _handle_streaming_response(
         self,

tests/llm_test.py

@@ -533,3 +533,39 @@ def test_handle_streaming_tool_calls_no_tools(mock_emit):
         expected_completed_llm_call=1,
         expected_final_chunk_result=response,
     )
+
+
+def test_llm_o4_mini_stop_parameter():
+    """Test that o4-mini model works correctly without stop parameter."""
+    llm = LLM(model="o4-mini", stop=["STOP", "END"])
+
+    # Check that stop parameter is set
+    assert llm.stop == ["STOP", "END"]
+
+    params = llm._prepare_completion_params(messages=[{"role": "user", "content": "Hello"}])
+
+    assert "stop" not in params
+
+    with patch("litellm.completion") as mock_completion:
+        # Create a mock response
+        mock_message = MagicMock()
+        mock_message.content = "Test response"
+        mock_choice = MagicMock()
+        mock_choice.message = mock_message
+        mock_response = MagicMock()
+        mock_response.choices = [mock_choice]
+        mock_response.usage = {
+            "prompt_tokens": 5,
+            "completion_tokens": 5,
+            "total_tokens": 10,
+        }
+
+        # Set up the mock to return our response
+        mock_completion.return_value = mock_response
+
+        response = llm.call(messages=[{"role": "user", "content": "Hello, world!"}])
+
+        assert response == "Test response"
+
+        call_args = mock_completion.call_args[1]
+        assert "stop" not in call_args