diff --git a/src/agents/models/chatcmpl_stream_handler.py b/src/agents/models/chatcmpl_stream_handler.py
index 474bffe09..5faf06c14 100644
--- a/src/agents/models/chatcmpl_stream_handler.py
+++ b/src/agents/models/chatcmpl_stream_handler.py
@@ -150,6 +150,12 @@ async def handle_stream(
                     )
 
                 if reasoning_content and state.reasoning_content_index_and_output:
+                    # Ensure summary list has at least one element
+                    if not state.reasoning_content_index_and_output[1].summary:
+                        state.reasoning_content_index_and_output[1].summary = [
+                            Summary(text="", type="summary_text")
+                        ]
+
                     yield ResponseReasoningSummaryTextDeltaEvent(
                         delta=reasoning_content,
                         item_id=FAKE_RESPONSES_ID,
@@ -201,7 +207,7 @@ async def handle_stream(
                     )
 
                     # Create a new summary with updated text
-                    if state.reasoning_content_index_and_output[1].content is None:
+                    if not state.reasoning_content_index_and_output[1].content:
                         state.reasoning_content_index_and_output[1].content = [
                             Content(text="", type="reasoning_text")
                         ]