The Annals of Hincmar name "Bosone filio Buvini quondam comitis" in 869. An agreement between Charles II "le Chauve" King of the West Franks and his brother Ludwig II "der Deutsche" King of the East Franks dated Jun 860 names "nobilis ac fidelibus laicis…Chuonradus, Evrardus, Adalardus, Arnustus, Warnarius, Liutfridus, Hruodolfus, Erkingarius, Gislebertus, Ratbodus, Arnulfus, Hugo, item Chuonradus, Liutharius, Berengarius, Matfridus, Boso, Sigeri, Hartmannus, Liuthardus, Richuinus, Wigricus, Hunfridus, Bernoldus, Hatto, Adalbertus, Burchardus, Christianus, Leutulfus, Hessi, Herimannus, item Hruodulfus, Sigehardus", although it is not known whether "…Boso…" refers to the same person. His brother-in-law King Charles II "le Chauve" granted the abbey of Saint-Maurice d'Agaune to him. "Boso comes simulque Bernardus comes ad vicem" donated Nogent "in pago Otmense" for the soul of "quondam amici nostri Odonis comitis…uxoris suæ Guendilmodis" to Saint-Martin-des-Tours by charter dated 871 after 21 Jun.
He was invested as Comte de Vienne in 870 by King Charles II after the latter conquered the kingdom of Provence. He was installed as Comte de Berry in  after the deposition of Gérard comte en Aquitaine. He accompanied King Charles II to Italy in 875: an agreement dated Feb 876 of King Charles II "le Chauve" names "Bosonis…ducis et sacri palatii archiministri atque imperiali missi" among those present in Italy with the king.
He was invested as dux regni Italici at Pavia in Feb 876, fulfilling the role of viceroy in the absence of the king. Recalled by Emperor Charles in early 877, Boson left his brother Richard in his place in Italy and became Governor and Comte de Provence in . He took part in the general rebellion of 877, refusing to swear allegiance to Louis II "le Bègue" King of the West Franks on his accession. After the death of King Louis II, "Hugo abbas et Boso et alii" sent "Walterum Episcopum Aurelianensem et Goiranum et Anscherum comites" to Ludwig III King of the East Franks to offer him part of the kingdom in 879.
He was named King BOSON at Mantaille, near Vienne 15 Oct 879 by the archbishops of Vienne, Besançon, Lyon, Tarentaise, Aix and Arles, and crowned at Lyon a few days later. Settipani points out that Boson´s kingdom was not referred to as Provence or Lower Burgundy (Bourgogne transjurane), doubting even that any term was used at all to describe it. He installed his capital at Vienne. The reigning Carolingian monarchs formed a league against him, captured Lyon, and besieged Vienne which fell in 882, although Boson refused to capitulate. The Annales Fuldenses record that the sons of Ludwig II " der Deutsche" King of the East Franks fought "Buosonem in Galliam" in 880 and expelled him from "Madasconam urbem", accepting homage from "Bernhardum qui in ea principatum tenebat".
The Annales Fuldenses record the death in 887 of "Buosone", leaving a young son by "filia Hludowici Italici regis". The epitaph of "Bosonis Regis" records his death "III Id Jan VIII anno regni sui". 1