fix: improve response api handling and cold storage configuration

- Fix s3_path configuration in cold storage logging to use actual logger instance path
- Add proper null/empty response validation in session handler to prevent processing invalid responses

Author: hula-la

litellm/litellm_core_utils/litellm_logging.py

@@ -4150,15 +4150,24 @@ def _generate_cold_storage_object_key(
         from litellm.integrations.s3 import get_s3_object_key
 
         # Only generate object key if cold storage is configured
-        if litellm.configured_cold_storage_logger is None:
+        configured_cold_storage_logger = litellm.configured_cold_storage_logger
+        if configured_cold_storage_logger is None:
             return None
 
         try:
             # Generate file name in same format as litellm.utils.get_logging_id
             s3_file_name = f"time-{start_time.strftime('%H-%M-%S-%f')}_{response_id}"
 
+            # Get the actual s3_path from the configured cold storage logger instance
+            s3_path = ""  # default value
+            
+            # Get the actual logger instance from the logger name
+            custom_logger = litellm.logging_callback_manager.get_active_custom_logger_for_callback_name(configured_cold_storage_logger)
+            if custom_logger and hasattr(custom_logger, 's3_path') and custom_logger.s3_path:
+                s3_path = custom_logger.s3_path
+            
             s3_object_key = get_s3_object_key(
-                s3_path="",  # Use empty path as default
+                s3_path=s3_path,  # Use actual s3_path from logger configuration
                 team_alias_prefix="",  # Don't split by team alias for cold storage
                 start_time=start_time,
                 s3_file_name=s3_file_name,

litellm/responses/litellm_completion_transformation/session_handler.py

@@ -141,7 +141,7 @@ async def extend_chat_completion_message_with_spend_log_payload(
         # Add Output messages for this Spend Log
         ############################################################
         _response_output = spend_log.get("response", "{}")
-        if isinstance(_response_output, dict):
+        if isinstance(_response_output, dict) and _response_output and _response_output != {}:
             # transform `ChatCompletion Response` to `ResponsesAPIResponse`
             model_response = ModelResponse(**_response_output)
             for choice in model_response.choices: