diff --git a/tests/tools/test_send_message_tool.py b/tests/tools/test_send_message_tool.py
index 3b2c0899158..48003f410a8 100644
--- a/tests/tools/test_send_message_tool.py
+++ b/tests/tools/test_send_message_tool.py
@@ -742,6 +742,64 @@ class TestSendTelegramHtmlDetection:
         sleep_mock.assert_awaited_once()
 
 
+class TestSendTelegramThreadIdMapping:
+    """General-topic mapping in _send_telegram (issue #22267).
+
+    Telegram forum supergroups address the General topic as
+    ``message_thread_id="1"`` on incoming updates, but the Bot API rejects
+    sends with ``message_thread_id=1`` ("Message thread not found"). The
+    gateway adapter's ``_message_thread_id_for_send`` helper maps "1" to
+    ``None`` for that reason; the standalone ``_send_telegram`` helper used
+    by the ``send_message`` tool needs the same mapping.
+    """
+
+    def _make_bot(self):
+        bot = MagicMock()
+        bot.send_message = AsyncMock(return_value=SimpleNamespace(message_id=1))
+        return bot
+
+    def test_general_topic_thread_id_omitted(self, monkeypatch):
+        """thread_id="1" must be dropped before calling the Bot API."""
+        bot = self._make_bot()
+        _install_telegram_mock(monkeypatch, bot)
+
+        asyncio.run(_send_telegram("tok", "-1001234567890", "hello", thread_id="1"))
+
+        bot.send_message.assert_awaited_once()
+        kwargs = bot.send_message.await_args.kwargs
+        assert "message_thread_id" not in kwargs
+
+    def test_non_general_topic_thread_id_preserved(self, monkeypatch):
+        """Real forum-topic thread ids (>1) still pass through as ints."""
+        bot = self._make_bot()
+        _install_telegram_mock(monkeypatch, bot)
+
+        asyncio.run(_send_telegram("tok", "-1001234567890", "hello", thread_id="17585"))
+
+        kwargs = bot.send_message.await_args.kwargs
+        assert kwargs["message_thread_id"] == 17585
+
+    def test_no_thread_id_no_kwarg(self, monkeypatch):
+        """With no thread_id, message_thread_id must not appear in kwargs."""
+        bot = self._make_bot()
+        _install_telegram_mock(monkeypatch, bot)
+
+        asyncio.run(_send_telegram("tok", "-1001234567890", "hello"))
+
+        kwargs = bot.send_message.await_args.kwargs
+        assert "message_thread_id" not in kwargs
+
+    def test_general_topic_thread_id_int_input_also_dropped(self, monkeypatch):
+        """thread_id passed as the int 1 (not str) must still be dropped."""
+        bot = self._make_bot()
+        _install_telegram_mock(monkeypatch, bot)
+
+        asyncio.run(_send_telegram("tok", "-1001234567890", "hello", thread_id=1))
+
+        kwargs = bot.send_message.await_args.kwargs
+        assert "message_thread_id" not in kwargs
+
+
 # ---------------------------------------------------------------------------
 # Tests for Discord thread_id support
 # ---------------------------------------------------------------------------
diff --git a/tools/send_message_tool.py b/tools/send_message_tool.py
index 380208d429e..5199bca67a0 100644
--- a/tools/send_message_tool.py
+++ b/tools/send_message_tool.py
@@ -710,7 +710,27 @@ async def _send_telegram(token, chat_id, message, media_files=None, thread_id=No
         media_files = media_files or []
         thread_kwargs = {}
         if thread_id is not None:
-            thread_kwargs["message_thread_id"] = int(thread_id)
+            # Reuse the gateway adapter's General-topic mapping: in Telegram
+            # forum supergroups, the General topic is addressed as
+            # message_thread_id="1" on incoming updates, but Bot API
+            # sendMessage rejects message_thread_id=1 with "Message thread
+            # not found". The adapter's helper maps "1" to None for that
+            # reason; the send_message tool needs the same mapping or a
+            # send to a forum group's General topic always errors out
+            # (see issue #22267).
+            try:
+                from gateway.platforms.telegram import TelegramAdapter
+                effective_thread_id = TelegramAdapter._message_thread_id_for_send(
+                    str(thread_id)
+                )
+            except Exception:
+                # Fallback: explicit mapping in case the adapter import
+                # fails (e.g. python-telegram-bot missing in this venv).
+                effective_thread_id = (
+                    None if str(thread_id) == "1" else int(thread_id)
+                )
+            if effective_thread_id is not None:
+                thread_kwargs["message_thread_id"] = effective_thread_id
         if disable_link_previews:
             thread_kwargs["disable_web_page_preview"] = True