Since Lithium uses PDO, you can just get the PDO object and call the beginTransaction() method.
$foo = app\models\Foo::create();
$pdo = Connections::get('default')->connection;
$pdo->beginTransaction();
$foo->bar = 'Hello';
$foo->save();
$pdo->commit();
https://github.com/UnionOfRAD/lithium/issues/1004#issuecomment-23690165 http://www.php.net/manual/en/pdo.begintransaction.php