diff --git a/nanobot/channels/base.py b/nanobot/channels/base.py
index d83367c..8f16399 100644
--- a/nanobot/channels/base.py
+++ b/nanobot/channels/base.py
@@ -72,7 +72,14 @@ class BaseChannel(ABC):
         if not allow_list:
             return True
         
-        return str(sender_id) in allow_list
+        sender_str = str(sender_id)
+        if sender_str in allow_list:
+            return True
+        if "|" in sender_str:
+            for part in sender_str.split("|"):
+                if part and part in allow_list:
+                    return True
+        return False
     
     async def _handle_message(
         self,
diff --git a/nanobot/channels/telegram.py b/nanobot/channels/telegram.py
index 840c250..ac2dba4 100644
--- a/nanobot/channels/telegram.py
+++ b/nanobot/channels/telegram.py
@@ -199,8 +199,10 @@ class TelegramChannel(BaseChannel):
         user = update.effective_user
         chat_id = message.chat_id
         
-        # Get sender identifier (prefer username, fallback to user_id)
-        sender_id = str(user.username or user.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}"
         
         # Store chat_id for replies
         self._chat_ids[sender_id] = chat_id