Is the concept of Supramundane Path in the Early Buddhist Texts or a later addition? Anyway what does it mean?
It’s mainly found in the commentaries, based on the Abhidhamma.
In the suttas, there is probably a distinction between the path that produces rebirth, and that which goes beyond rebirth, which is supramundane (lokuttara).
The Abhidhamma and Commentaries take this simple distinction and depict the path as essentially twofold. Basically everything you and I and everyone else has ever known is the “mundane” path, which is where practice actually happens. Then, at the moment of enlightenment, there is a single mind-moment, an umpteen billionth of a second, where all of the path-factors are present in full strength and the fetters are cut forever: this is the “supramundane path”. Needless to say, the path is never spoken of in this way in the suttas.