fix(prompting): address greptile review - fix SyntaxError, restore backward compat, add trailing tool-call test

- Remove stray ): on line 303 (P0 SyntaxError)
- Restore backward-compatible trailing-assistant behavior (P1)
- Add test_ensure_alternating_roles_trailing_tool_call_assistant
- Keep role check alongside _counts_for_alternation (P2 is false positive)

Made-with: Cursor

litellm/litellm_core_utils/prompt_templates/common_utils.py

@@ -300,7 +300,6 @@ def _insert_user_continue_message(
         curr_message = result_messages[i]
         inserted_continue_message = False
         if _counts_for_alternation(curr_message) and curr_message["role"] == "assistant":
-        ):
             j = i - 1
             while j >= 0:
                 previous_message = result_messages[j]
@@ -314,12 +313,9 @@ def _insert_user_continue_message(
         if not inserted_continue_message:
             i += 1
 
-    # Handle final message
-    if (
-        result_messages[-1]["role"] == "assistant"
-        and _counts_for_alternation(result_messages[-1])
-        and ensure_alternating_roles
-    ):
+    # Handle final message — append user_continue after any trailing assistant,
+    # including ones with tool_calls, to preserve backward compatibility.
+    if result_messages[-1]["role"] == "assistant" and ensure_alternating_roles:
         result_messages.append(continue_message)
 
     return result_messages

tests/llm_translation/test_prompt_factory.py

@@ -903,6 +903,40 @@ def test_ensure_alternating_roles_does_not_split_tool_call_chain():
     ]
 
 
+def test_ensure_alternating_roles_trailing_tool_call_assistant():
+    messages = [
+        {"role": "user", "content": "What's the weather?"},
+        {
+            "role": "assistant",
+            "content": None,
+            "tool_calls": [
+                {
+                    "id": "call_abc",
+                    "type": "function",
+                    "function": {
+                        "name": "get_weather",
+                        "arguments": '{"location": "NYC"}',
+                    },
+                }
+            ],
+        },
+    ]
+
+    transformed_messages = get_completion_messages(
+        messages=messages,
+        assistant_continue_message=None,
+        user_continue_message=None,
+        ensure_alternating_roles=True,
+    )
+
+    # Backward compat: trailing assistant (even with tool_calls) gets user_continue
+    # appended, then assistant_continue bridges the user→user gap.
+    assert transformed_messages[-1] == {"role": "user", "content": "Please continue."}
+    assert transformed_messages[0] == {"role": "user", "content": "What's the weather?"}
+    assert transformed_messages[1]["role"] == "assistant"
+    assert transformed_messages[1].get("tool_calls") is not None
+
+
 def test_alternating_roles_e2e():
     from litellm.llms.custom_httpx.http_handler import HTTPHandler
     import json