The Upanishads, texts traditionally included with the Vedas consisting of conversations between sages and their students which clarify the philosophical teachings of the Vedas. In the Vedanta tradition they're referred to as the Shruti Prasthana, because the Vedas are Shruti or heard from the gods.
The Bhagavad Gita, which needs little introuction. This is referred to as the Smriti Prasthana, because the Bhagavad Gita is part of Mahabharata which is a Smriti text, as it was composed by the sage Vyasa.
The Brahma Sutras, AKA the Vedanta Sutras, a work by Vyasa which summarizes and systematizes the philosophical doctrines laid out in the Upanishads. It is referred to Nyaya Prasthana, because Vyasa relies on Nyaya or logic to argue for his interpretation of the words of the Upanishads. (You can read the Brahma Sutras here.)
My question is, who developed this terminology of calling these texts the Prasthanatrayi or three starting points of philosophical knowledge? Does Vyasa mention this in the Brahma Sutras? Or was it invented by subsequent Vedantic thinkers like Adi Shankaracharya?
This should go without saying, but just in case, I'm not looking for who are the author of these three. I'm asking who singled out these particular works as the three starting points of the Vedanta school.