Ensure that function_call_prompt extends system messages following its current schema

Fixes #11267

litellm/litellm_core_utils/prompt_templates/factory.py

@@ -3711,7 +3711,14 @@ def function_call_prompt(messages: list, functions: list):
     function_added_to_prompt = False
     for message in messages:
         if "system" in message["role"]:
-            message["content"] += f""" {function_prompt}"""
+            if isinstance(message["content"], str):
+                message["content"] += f""" {function_prompt}"""
+            else:
+                message["content"].append({
+                    "type": "text",
+                    "text": f""" {function_prompt}""",
+                    "cache_control": {"type": "ephemeral"}
+                })
             function_added_to_prompt = True
 
     if function_added_to_prompt is False:

tests/test_litellm/test_system_message_format_bug.py

@@ -0,0 +1,72 @@
+"""
+Test for GitHub issue #11267 - System message format issue with Ollama + tools
+"""
+
+from unittest.mock import patch
+
+@patch("litellm.add_function_to_prompt", True)
+def test_system_message_format_issue_reproduction():
+    """
+    Reproduces the system message format bug from GitHub issue #11267.
+    """
+    from litellm import completion
+    
+    # Define test data directly from data.jsonl content
+    model = "ollama/custom_model_name"  # Use explicit Ollama model
+    messages = [
+        {
+            "role": "user",
+            "content": [
+                {
+                    "type": "text",
+                    "text": "What is the capital of France?"
+                }
+            ]
+        },
+        {
+            "role": "system",
+            "content": [
+                {
+                    "type": "text",
+                    "text": "You are Claude Code, Anthropic's official CLI for Claude.",
+                    "cache_control": {"type": "ephemeral"}
+                }
+            ]
+        }
+    ]
+    
+    temperature = 1
+    
+    # Add tools to trigger the bug - this is what causes the issue
+    tools = [
+        {
+            "type": "function", 
+            "function": {
+                "name": "get_weather",
+                "description": "Get weather for a location",
+                "parameters": {
+                    "type": "object",
+                    "properties": {
+                        "location": {"type": "string"}
+                    },
+                    "required": ["location"]
+                }
+            }
+        }
+    ]
+
+    response = completion(
+        model=model,
+        messages=messages,
+        tools=tools,
+        temperature=temperature,
+        mock_response=True
+    )
+
+    assert len(messages[1]["content"]) == 2
+
+
+if __name__ == "__main__":
+    print("Testing system message format issue...")
+    test_system_message_format_issue_reproduction()
+    print("Tests completed!")