fix: preserve conversation context in Telegram private chats (#1105)

* fix: preserve conversation context in Telegram private chats

In private (1-on-1) chats, set topic_id=None so all messages map to a
single DeerFlow thread per chat instead of creating a new thread for
every message. Also fix _cmd_generic to use topic_id=None in private
chats so /new correctly targets the default thread.

Group chat behavior is unchanged (reply_to or msg_id as topic_id).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: preserve conversation context in Telegram private chats

Fixes #1101

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix: mirror _on_text reply logic in _cmd_generic for group chats

_cmd_generic now prefers reply_to_message.message_id over msg_id in
group/supergroup chats, consistent with _on_text. This ensures commands
like /new and /status target the correct conversation thread when sent
as a reply in group chats.

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: JeffJiang <for-eleven@hotmail.com>
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/src/channels/manager.py

@@ -351,12 +351,12 @@ class ChannelManager:
     async def _handle_chat(self, msg: InboundMessage) -> None:
         client = self._get_client()
 
-        # Look up existing DeerFlow thread by topic_id (if present)
-        thread_id = None
-        if msg.topic_id:
-            thread_id = self.store.get_thread_id(msg.channel_name, msg.chat_id, topic_id=msg.topic_id)
-            if thread_id:
-                logger.info("[Manager] reusing thread: thread_id=%s for topic_id=%s", thread_id, msg.topic_id)
+        # Look up existing DeerFlow thread.
+        # topic_id may be None (e.g. Telegram private chats) — the store
+        # handles this by using the "channel:chat_id" key without a topic suffix.
+        thread_id = self.store.get_thread_id(msg.channel_name, msg.chat_id, topic_id=msg.topic_id)
+        if thread_id:
+            logger.info("[Manager] reusing thread: thread_id=%s for topic_id=%s", thread_id, msg.topic_id)
 
         # No existing thread found — create a new one
         if thread_id is None:

backend/src/channels/telegram.py

@@ -234,6 +234,17 @@ class TelegramChannel(Channel):
         user_id = str(update.effective_user.id)
         msg_id = str(update.message.message_id)
 
+        # Use the same topic_id logic as _on_text so that commands
+        # like /new target the correct thread mapping.
+        if update.effective_chat.type == "private":
+            topic_id = None
+        else:
+            reply_to = update.message.reply_to_message
+            if reply_to:
+                topic_id = str(reply_to.message_id)
+            else:
+                topic_id = msg_id
+
         inbound = self._make_inbound(
             chat_id=chat_id,
             user_id=user_id,
@@ -241,6 +252,7 @@ class TelegramChannel(Channel):
             msg_type=InboundMessageType.COMMAND,
             thread_ts=msg_id,
         )
+        inbound.topic_id = topic_id
 
         if self._main_loop and self._main_loop.is_running():
             asyncio.run_coroutine_threadsafe(self._send_running_reply(chat_id, update.message.message_id), self._main_loop)
@@ -259,14 +271,19 @@ class TelegramChannel(Channel):
         user_id = str(update.effective_user.id)
         msg_id = str(update.message.message_id)
 
-        # topic_id: if the user is replying to a bot message, look up
-        # the original topic_id stored for that reply chain.  Otherwise
-        # the current message starts a new topic.
-        reply_to = update.message.reply_to_message
-        if reply_to:
-            topic_id = str(reply_to.message_id)
+        # topic_id determines which DeerFlow thread the message maps to.
+        # In private chats, use None so that all messages share a single
+        # thread (the store key becomes "channel:chat_id").
+        # In group chats, use the reply-to message id or the current
+        # message id to keep separate conversation threads.
+        if update.effective_chat.type == "private":
+            topic_id = None
         else:
-            topic_id = msg_id
+            reply_to = update.message.reply_to_message
+            if reply_to:
+                topic_id = str(reply_to.message_id)
+            else:
+                topic_id = msg_id
 
         inbound = self._make_inbound(
             chat_id=chat_id,