diff --git a/nanobot/channels/telegram.py b/nanobot/channels/telegram.py
index 32f8c67..d2ce74c 100644
--- a/nanobot/channels/telegram.py
+++ b/nanobot/channels/telegram.py
@@ -222,12 +222,18 @@ class TelegramChannel(BaseChannel):
             "Type /help to see available commands."
         )
     
+    @staticmethod
+    def _sender_id(user) -> str:
+        """Build sender_id with username for allowlist matching."""
+        sid = str(user.id)
+        return f"{sid}|{user.username}" if user.username else sid
+
     async def _forward_command(self, update: Update, context: ContextTypes.DEFAULT_TYPE) -> None:
         """Forward slash commands to the bus for unified handling in AgentLoop."""
         if not update.message or not update.effective_user:
             return
         await self._handle_message(
-            sender_id=str(update.effective_user.id),
+            sender_id=self._sender_id(update.effective_user),
             chat_id=str(update.message.chat_id),
             content=update.message.text,
         )
@@ -240,11 +246,7 @@ class TelegramChannel(BaseChannel):
         message = update.message
         user = update.effective_user
         chat_id = message.chat_id
-        
-        # Use stable numeric ID, but keep username for allowlist compatibility
-        sender_id = str(user.id)
-        if user.username:
-            sender_id = f"{sender_id}|{user.username}"
+        sender_id = self._sender_id(user)
         
         # Store chat_id for replies
         self._chat_ids[sender_id] = chat_id