fix: Handle Mistral LLM role requirements for tools

- Modify role handling in LLM class for Mistral models
- Add tests for Mistral role handling with tools
- Fixes #2194

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

src/crewai/llm.py

@@ -406,6 +406,14 @@ class LLM:
                     "Invalid message format. Each message must be a dict with 'role' and 'content' keys"
                 )
 
+        # Handle Mistral role requirements
+        if "mistral" in self.model.lower():
+            messages_copy = [dict(message) for message in messages]  # Deep copy
+            for message in messages_copy:
+                if message.get("role") == "assistant":
+                    message["role"] = "user"
+            return messages_copy
+
         if not self.is_anthropic:
             return messages
 

tests/llm_test.py

@@ -13,6 +13,47 @@ from crewai.utilities.token_counter_callback import TokenCalcHandler
 
 
 # TODO: This test fails without print statement, which makes me think that something is happening asynchronously that we need to eventually fix and dive deeper into at a later date
+@pytest.mark.vcr(filter_headers=["authorization"])
+@pytest.mark.vcr(filter_headers=["authorization"])
+def test_mistral_with_tools():
+    """Test that Mistral LLM correctly handles role requirements with tools."""
+    llm = LLM(model="mistral/mistral-large-latest")
+    messages = [
+        {"role": "user", "content": "Test message"},
+        {"role": "assistant", "content": "Assistant response"}
+    ]
+    
+    # Get the formatted messages
+    formatted_messages = llm._format_messages_for_provider(messages)
+    
+    # Verify that assistant role was changed to user for Mistral
+    assert any(msg["role"] == "user" for msg in formatted_messages if msg["content"] == "Assistant response")
+    assert not any(msg["role"] == "assistant" for msg in formatted_messages)
+    
+    # Original messages should not be modified
+    assert any(msg["role"] == "assistant" for msg in messages)
+
+
+def test_mistral_role_handling():
+    """Test that Mistral LLM correctly handles role requirements."""
+    llm = LLM(model="mistral/mistral-large-latest")
+    messages = [
+        {"role": "system", "content": "System message"},
+        {"role": "user", "content": "User message"},
+        {"role": "assistant", "content": "Assistant message"}
+    ]
+    
+    # Get the formatted messages
+    formatted_messages = llm._format_messages_for_provider(messages)
+    
+    # Verify that assistant role was changed to user for Mistral
+    assert any(msg["role"] == "user" for msg in formatted_messages if msg["content"] == "Assistant message")
+    assert not any(msg["role"] == "assistant" for msg in formatted_messages)
+    
+    # Original messages should not be modified
+    assert any(msg["role"] == "assistant" for msg in messages)
+
+
 @pytest.mark.vcr(filter_headers=["authorization"])
 def test_llm_callback_replacement():
     llm1 = LLM(model="gpt-4o-mini")