fix(telegram): ignore implicit topic root replies (#175)

docs/reference/transports/telegram.md

@@ -76,6 +76,11 @@ Explicit invocation includes any of:
 - Replying to a bot message.
 - Built-in or plugin slash commands (for example `/agent`, `/model`, `/reasoning`, `/file`, `/trigger`).
 
+Note: In forum topics, some Telegram clients include `reply_to_message` on every
+message, pointing at the topic’s root service message (`message_id ==
+message_thread_id`). Takopi treats those as implicit topic references, not
+explicit replies, so they do not trigger mentions-only mode.
+
 Commands:
 
 - `/trigger` shows the current mode and defaults.

src/takopi/telegram/parsing.py

@@ -110,6 +110,11 @@ def _parse_incoming_message(
     media_group_id = msg.media_group_id
     thread_id = msg.message_thread_id
     is_topic_message = msg.is_topic_message
+    if thread_id is not None and reply_to_message_id == thread_id:
+        reply_to_message_id = None
+        reply_to_text = None
+        reply_to_is_bot = None
+        reply_to_username = None
     return TelegramIncomingMessage(
         transport="telegram",
         chat_id=msg_chat_id,

src/takopi/telegram/trigger_mode.py

@@ -43,12 +43,17 @@ def should_trigger_run(
         needle = f"@{bot_username}"
         if needle in lowered:
             return True
-    if msg.reply_to_is_bot:
+    implicit_topic_reply = (
+        msg.thread_id is not None and msg.reply_to_message_id == msg.thread_id
+    )
+
+    if msg.reply_to_is_bot and not implicit_topic_reply:
         return True
     if (
         bot_username
         and msg.reply_to_username
         and msg.reply_to_username.lower() == bot_username
+        and not implicit_topic_reply
     ):
         return True
     command_id, _ = _parse_slash_command(text)

tests/test_telegram_incoming.py

@@ -57,6 +57,34 @@ def test_parse_incoming_update_maps_fields() -> None:
     assert msg.raw["message_id"] == 10
 
 
+def test_parse_incoming_update_ignores_implicit_topic_reply() -> None:
+    update = Update(
+        update_id=1,
+        message=Message(
+            message_id=187,
+            message_thread_id=163,
+            is_topic_message=True,
+            text="Hello",
+            chat=Chat(id=123, type="supergroup", is_forum=True),
+            from_=User(id=99),
+            reply_to_message=MessageReply(
+                message_id=163,
+                from_=User(id=77, is_bot=True, username="TakopiBot"),
+            ),
+        ),
+    )
+
+    msg = parse_incoming_update(update, chat_id=123)
+    assert msg is not None
+    assert isinstance(msg, TelegramIncomingMessage)
+    assert msg.thread_id == 163
+    assert msg.is_topic_message is True
+    assert msg.reply_to_message_id is None
+    assert msg.reply_to_text is None
+    assert msg.reply_to_is_bot is None
+    assert msg.reply_to_username is None
+
+
 def test_parse_incoming_update_filters_non_matching_chat() -> None:
     update = Update(
         update_id=1,

tests/test_telegram_trigger_mode.py

@@ -83,6 +83,32 @@ def test_should_trigger_run_reply_to_bot() -> None:
     )
 
 
+def test_should_trigger_run_ignores_implicit_topic_reply_to_root() -> None:
+    runtime = _runtime()
+    msg = TelegramIncomingMessage(
+        transport="telegram",
+        chat_id=1,
+        message_id=187,
+        text="hello",
+        reply_to_message_id=163,
+        reply_to_text=None,
+        reply_to_is_bot=True,
+        reply_to_username="TakopiBot",
+        sender_id=1,
+        thread_id=163,
+        is_topic_message=True,
+        chat_type="supergroup",
+        is_forum=True,
+    )
+    assert not should_trigger_run(
+        msg,
+        bot_username=None,
+        runtime=runtime,
+        command_ids=set(),
+        reserved_chat_commands=set(RESERVED_CHAT_COMMANDS),
+    )
+
+
 def test_should_trigger_run_known_commands() -> None:
     runtime = _runtime()
     assert should_trigger_run(