The project consists of a study of the manuscript tradition of the medieval text Merlin en prose, as a preliminary study for a new critical edition. The current critical edition has been conducted using the method of a basic witness (A. Micha (edited by), Robert de Boron, Merlin, roman du XIII siècle, 1979). Although it constitutes a fundamental study, the edition of A. Micha cannot be considered definitive in its results; on the contrary, it requires an update of the method and the results obtained with it, and thus of the data available to the publisher (consistency of the testimonial; dating of some witnesses). The aim of this project is therefore a new study of the manuscript tradition, to be conducted with the method applied to the critical edition of another medieval Arthurian prose, namely the Giron le Courtois (L. Leonardi – R. Trachsler et al. (edited by), Il Ciclo di Guiron le Courtois. Romanzi in prosa del secolo XIII, 2020). The work of constitutio textus will be conducted with a strictly Lachmannian method, and will depend on a preliminary phase of rationalization of witness relationships. The stemmatic rationalization of the testimonial will be argued on the basis of significant errors or variants that can reasonably be judged as innovations. The rationalization of the tradition expressed in a stemmatic representation will ultimately also serve to clarify the history of the “text” of the prose, circulated within multiple cyclic configurations.