Eighth century Tibet sat between two living Buddhist worlds. From India came the monastic and scholastic tradition of the great universities, with its long graded path of ethics, study, meditation and analytical insight. From Tang China came Chan, whose teachers held that discursive effort is itself an obstacle and that awakening is immediate when conceptual activity stops. Both had followings at the Tibetan court, and the difference was not academic, since it decided what monks should actually do with their days.
Tibetan histories record that Trisong Detsen summoned both sides to Samye, at a date usually given as somewhere between 792 and 794. The Indian position was argued by Kamalasila, a pupil of Santaraksita, and the Chinese by a Chan master the Tibetan sources call Hwashang Mahayana, generally identified with the monk Moheyan. The Tibetan account has Kamalasila win, the emperor rule for the gradual path, and the Chinese party withdraw from Tibet.
The account is contested. Chinese documents recovered from the sealed cave at Dunhuang give the opposite result, with Moheyan vindicated, and modern historians treat the event less as a single formal disputation than as a protracted argument at court that the tradition later compressed into one scene. What is not contested is the outcome for Tibetan Buddhism. The Indian scholastic model became the norm, Kamalasila wrote his Stages of Meditation in its defence, and the figure of the Hwashang survived in Tibetan literature for a thousand years as the standing example of a wrong view, invoked against any teacher accused of telling students that nothing needs to be done.