The text is framed as a first-person report of Viraf's own journey rather than a work with a credited literary author, and no compiler is named in the surviving manuscript tradition, which itself postdates the narrative's dramatic setting by an uncertain span.
What would resolve this An independent contemporary or near-contemporary Sasanian or early Islamic-era reference to the text or its compiler would help settle authorship; a philological study distinguishing linguistic strata within the surviving Pahlavi could help separate earlier from later material.
OpenIranian philology and Zoroastrian textual studiesMartin Haug and E.W. West, translators, with Dastur Hoshangji Jamaspji Asa, The Book of Arda Viraf (Martin Haug and E.W. West)