diff --git a/s11_background_tasks/code.py b/s11_background_tasks/code.py
index 8492e85d..5ac1262a 100644
--- a/s11_background_tasks/code.py
+++ b/s11_background_tasks/code.py
@@ -460,6 +460,9 @@ def inject_background_results(messages: list) -> int:
                 *blocks,
             ]
     else:
+        # Currently unreachable: agent_loop always leaves messages[-1] as a
+        # user message, so this branch is never hit in the teaching code.
+        # Kept for independent reuse or future wake-up from background tasks.
         messages.append({"role": "user", "content": blocks})
     return len(notifications)