diff --git a/nanobot/agent/tools/message.py b/nanobot/agent/tools/message.py
index efbadca10..3ac813248 100644
--- a/nanobot/agent/tools/message.py
+++ b/nanobot/agent/tools/message.py
@@ -86,12 +86,14 @@ class MessageTool(Tool):
     ) -> str:
         channel = channel or self._default_channel
         chat_id = chat_id or self._default_chat_id
-        # Only use default message_id if chat_id matches the default context.
-        # If targeting a different chat, don't reply to the original message.
-        if chat_id == self._default_chat_id:
+        # Only inherit default message_id when targeting the same channel+chat.
+        # Cross-chat sends must not carry the original message_id, because
+        # some channels (e.g. Feishu) use it to determine the target
+        # conversation via their Reply API, which would route the message
+        # to the wrong chat entirely.
+        if channel == self._default_channel and chat_id == self._default_chat_id:
             message_id = message_id or self._default_message_id
         else:
-            # Targeting a different chat - don't use default message_id
             message_id = None
 
         if not channel or not chat_id: