This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Shapur I's son Bahram I took the Sasanian throne in 274 CE, inheriting a court where the Zoroastrian priesthood had spent three decades watching a king tolerate, and even favor, a rival teacher's faith alongside their own. Freed at last from the protection Mani had enjoyed for thirty years under Shapur I, the priesthood brought a formal charge of heresy against him and won the new king's agreement to act on it.
Mani was imprisoned at Gundeshapur in Susiana, where he died after twenty six days in captivity, at the end of March in either 276 or 277 depending on the source consulted. The thirty years of royal protection that had let his teaching spread across the Persian heartland ended within roughly two years of Bahram I's accession, a reversal as fast as the patronage that preceded it had been long.
His closest disciples in Persia were arrested and executed soon after Mani's own death, a purge that reached well beyond the founder himself and into the network of missionaries and administrators he had spent three decades building around him at the Sasanian court, stripping the faith of much of its Persian leadership in a single stroke.
What Bahram I's reign changed for Manichaeism's spread was the end of its status as a tolerated royal project in its own homeland. Three decades of protection at the Sasanian court gave way, within two years of a new king's accession, to the execution of its founder and the arrest of the disciples who might otherwise have carried his teaching forward from Persia itself, leaving the faith's future spread to depend on missionaries already sent abroad rather than on any continuing base at home.