All three players were drafted out of the Canadian Hockey League and a deadline on each of their contract status loomed at 5 p.m. on Friday. Hagel, Budik and Osmanski are eligible for the 2018 NHL Draft in June.
Buffalo's top three picks of the Class of 2016 - Alexander Nylander (first round, eighth overall), Rasmus Asplund (second round, 33rd overall) and Cliff Pu (third round, 69th overall) - are signed to entry-level contracts.