Fix issue #2738: Exclude stop parameter for o3 model

Co-Authored-By: Joe Moura <joao@crewai.com>

tests/unit/test_llm.py

@@ -0,0 +1,52 @@
+import unittest
+from unittest.mock import patch, MagicMock
+from types import SimpleNamespace
+
+from crewai.llm import LLM
+
+
+class TestLLM(unittest.TestCase):
+    @patch("crewai.llm.litellm.completion")
+    @patch("crewai.llm.LLM.supports_stop_words")
+    def test_call_with_supported_stop_words(self, mock_supports_stop_words, mock_completion):
+        mock_supports_stop_words.return_value = True
+        
+        message = SimpleNamespace(content="Hello, World!")
+        choice = SimpleNamespace(message=message)
+        response = SimpleNamespace(choices=[choice])
+        mock_completion.return_value = response
+        
+        llm = LLM(model="gpt-4", stop=["STOP"])
+        
+        messages = [{"role": "user", "content": "Say Hello"}]
+        result = llm.call(messages)
+        
+        mock_completion.assert_called_once()
+        call_args = mock_completion.call_args[1]
+        self.assertIn("stop", call_args)
+        self.assertEqual(call_args["stop"], ["STOP"])
+        self.assertEqual(result, "Hello, World!")
+    
+    @patch("crewai.llm.litellm.completion")
+    @patch("crewai.llm.LLM.supports_stop_words")
+    def test_call_with_unsupported_stop_words(self, mock_supports_stop_words, mock_completion):
+        mock_supports_stop_words.return_value = False
+        
+        message = SimpleNamespace(content="Hello, World!")
+        choice = SimpleNamespace(message=message)
+        response = SimpleNamespace(choices=[choice])
+        mock_completion.return_value = response
+        
+        llm = LLM(model="o3", stop=["STOP"])
+        
+        messages = [{"role": "user", "content": "Say Hello"}]
+        result = llm.call(messages)
+        
+        mock_completion.assert_called_once()
+        call_args = mock_completion.call_args[1]
+        self.assertNotIn("stop", call_args)
+        self.assertEqual(result, "Hello, World!")
+
+
+if __name__ == "__main__":
+    unittest.main()