diff --git a/telegram/bot.py b/telegram/bot.py
index 97e7435..a841df7 100644
--- a/telegram/bot.py
+++ b/telegram/bot.py
@@ -1660,12 +1660,6 @@ def _group_into_windows(messages: list[dict], window_seconds: int = 300) -> list
     if not messages:
         return []
 
-    # Group by chat_id first
-    by_chat: dict[int, list[dict]] = {}
-    for msg in messages:
-        chat_id = msg.get("chat_id", 0)
-        by_chat.setdefault(chat_id, []).append(msg)
-
     # Group by chat_id first
     by_chat: dict[int, list[dict]] = {}
     for msg in messages:
@@ -1693,7 +1687,6 @@ def _group_into_windows(messages: list[dict], window_seconds: int = 300) -> list
             else:
                 current_window.append(msg)
 
-
         if current_window:
             windows.append(current_window)