Vedanta is constituted by the upenisaes, text called upenitas. Christana teaches ar juna directly from the openisans. The wisdom of the opanitans is embodied in the bagawad gita. And then there is another text called the brahma sutras where philosophical issues arising from the openisiats are worked out. These three together, the opanishats, the bra bagawad Gita and the brahma Sutras, together are the foundational texts vedanta.