diff --git a/litellm/responses/litellm_completion_transformation/streaming_iterator.py b/litellm/responses/litellm_completion_transformation/streaming_iterator.py
index beffd12a349..71502e33d5c 100644
--- a/litellm/responses/litellm_completion_transformation/streaming_iterator.py
+++ b/litellm/responses/litellm_completion_transformation/streaming_iterator.py
@@ -602,6 +602,8 @@ class LiteLLMCompletionStreamingIterator(ResponsesAPIStreamingIterator):
         if self._cached_reasoning_item_id is not None:
             self._message_output_index = self._next_tool_output_index
             self._next_tool_output_index += 1
+        else:
+            self._message_output_index = 0
         self._sequence_number += 1
         event: Final = OutputItemAddedEvent(
             type=ResponsesAPIStreamEvents.OUTPUT_ITEM_ADDED,