refactor: address review feedback on invalid role validation

- Move VALID_MESSAGE_ROLES to constants.py per project convention
- Remove unused idx variable from enumerate
- Fix weak OR assertion — split into two independent assertions
  with descriptive error messages

litellm/constants.py

@@ -1791,3 +1791,6 @@ ADVISOR_TOOL_DESCRIPTION: str = (
     "want to verify your reasoning, or face a complex decision. "
     "Describe your question or challenge clearly in the 'question' field."
 )
+
+# Valid roles for OpenAI chat completion messages
+VALID_MESSAGE_ROLES = {"system", "user", "assistant", "tool", "function", "developer"}

litellm/utils.py

@@ -73,6 +73,7 @@ from litellm.constants import (
     MINIMUM_PROMPT_CACHE_TOKEN_COUNT,
     OPENAI_EMBEDDING_PARAMS,
     TOOL_CHOICE_OBJECT_TOKEN_COUNT,
+    VALID_MESSAGE_ROLES,
 )
 
 _CachingHandlerResponse = None
@@ -8211,8 +8212,6 @@ def convert_list_message_to_dict(messages: List):
     return new_messages
 
 
-VALID_MESSAGE_ROLES = {"system", "user", "assistant", "tool", "function", "developer"}
-
 
 def validate_and_fix_openai_messages(messages: List):
     """
@@ -8221,7 +8220,7 @@ def validate_and_fix_openai_messages(messages: List):
     Handles missing role for assistant messages and rejects invalid roles.
     """
     new_messages = []
-    for idx, message in enumerate(messages):
+    for message in messages:
         if not message.get("role"):
             message["role"] = "assistant"
         elif message["role"] not in VALID_MESSAGE_ROLES:

tests/litellm_utils_tests/test_invalid_role_validation.py

@@ -67,7 +67,9 @@ class TestInvalidRoleValidation:
         error_text = str(exc_info.value)
         # No traceback leakage
         assert "Traceback" not in error_text
-        assert ".py\"" not in error_text or "litellm" not in error_text
+        # No internal path disclosure
+        assert ".py\"" not in error_text, f"Internal file path leaked: {error_text}"
+        assert "litellm" not in error_text or "Invalid role" in error_text, f"litellm internal path leaked: {error_text}"
         # No internal path disclosure
         assert "/usr/lib/" not in error_text
         assert "site-packages" not in error_text