diff --git a/plugins/platforms/matrix/adapter.py b/plugins/platforms/matrix/adapter.py
index 0b663f1b7..adb880b4d 100644
--- a/plugins/platforms/matrix/adapter.py
+++ b/plugins/platforms/matrix/adapter.py
@@ -2947,6 +2947,19 @@ class MatrixAdapter(BasePlatformAdapter):
             return True
         except Exception as exc:
             logger.warning("Matrix: error joining %s: %s", room_id, exc)
+            # Abandoned rooms (no current members) surface as "no servers
+            # in the room have been provided" or "room not found". The
+            # pending invite keeps retrying every startup unless we
+            # explicitly leave it. The match is narrow enough that
+            # transient failures still leave the invite untouched for the
+            # next try.
+            msg = str(exc).lower()
+            if ("no servers" in msg) or ("room not found" in msg):
+                try:
+                    await self._client.leave_room(RoomID(room_id))
+                    logger.info("Matrix: declined dead invite to %s", room_id)
+                except Exception:
+                    pass
             return False
 
     def _schedule_invite_join(
diff --git a/tests/gateway/test_matrix.py b/tests/gateway/test_matrix.py
index 43aea0d0e..7481e66b3 100644
--- a/tests/gateway/test_matrix.py
+++ b/tests/gateway/test_matrix.py
@@ -4527,3 +4527,87 @@ class TestCreateMatrixSession:
                     assert session.connector is fake_connector
                 finally:
                     await session.close()
+
+
+class TestMatrixDeadInviteHandling:
+    """Tests for _join_room_by_id auto-leaving dead/abandoned rooms.
+
+    Regression: when a room had no current members, ``join_room`` raised
+    ``MUnknown: Can't join remote room because no servers that are in the
+    room have been provided``. The pending invite stayed in the bot's view
+    of the world, so every gateway restart re-attempted the join and
+    re-emitted the warning indefinitely. There was no path that ever
+    cleared the invite.
+    """
+
+    def setup_method(self):
+        self.adapter = _make_adapter()
+        self.adapter._refresh_dm_cache = AsyncMock()
+
+    @pytest.mark.asyncio
+    async def test_no_servers_error_triggers_leave(self):
+        join_err = Exception(
+            "Can't join remote room because no servers that are in the "
+            "room have been provided."
+        )
+        self.adapter._client = types.SimpleNamespace(
+            join_room=AsyncMock(side_effect=join_err),
+            leave_room=AsyncMock(),
+        )
+
+        result = await self.adapter._join_room_by_id("!dead:example.org")
+
+        assert result is False
+        self.adapter._client.leave_room.assert_awaited_once()
+        # leave_room receives a RoomID-wrapped value; verify the underlying str.
+        leave_arg = self.adapter._client.leave_room.await_args.args[0]
+        assert str(leave_arg) == "!dead:example.org"
+
+    @pytest.mark.asyncio
+    async def test_room_not_found_error_triggers_leave(self):
+        join_err = Exception("M_NOT_FOUND: Room not found")
+        self.adapter._client = types.SimpleNamespace(
+            join_room=AsyncMock(side_effect=join_err),
+            leave_room=AsyncMock(),
+        )
+
+        await self.adapter._join_room_by_id("!gone:example.org")
+        self.adapter._client.leave_room.assert_awaited_once()
+
+    @pytest.mark.asyncio
+    async def test_transient_error_does_not_trigger_leave(self):
+        """A network blip or 5xx must NOT decline the invite — the bot
+        should retry on the next sync cycle."""
+        join_err = Exception("Connection reset by peer")
+        self.adapter._client = types.SimpleNamespace(
+            join_room=AsyncMock(side_effect=join_err),
+            leave_room=AsyncMock(),
+        )
+
+        result = await self.adapter._join_room_by_id("!transient:example.org")
+        assert result is False
+        self.adapter._client.leave_room.assert_not_awaited()
+
+    @pytest.mark.asyncio
+    async def test_successful_join_does_not_attempt_leave(self):
+        self.adapter._client = types.SimpleNamespace(
+            join_room=AsyncMock(return_value=None),
+            leave_room=AsyncMock(),
+        )
+
+        result = await self.adapter._join_room_by_id("!alive:example.org")
+        assert result is True
+        assert "!alive:example.org" in self.adapter._joined_rooms
+        self.adapter._client.leave_room.assert_not_awaited()
+
+    @pytest.mark.asyncio
+    async def test_leave_room_failure_is_swallowed(self):
+        """If leave_room itself fails (e.g. server returns 500), the helper
+        must still return False cleanly rather than re-raise."""
+        self.adapter._client = types.SimpleNamespace(
+            join_room=AsyncMock(side_effect=Exception("no servers in the room")),
+            leave_room=AsyncMock(side_effect=Exception("500 internal")),
+        )
+
+        result = await self.adapter._join_room_by_id("!brokenleave:example.org")
+        assert result is False