Viviani and Fine have both impressed since joining as 'apprentices' at the start of August, with 22-year-old Viviani sprinting to victory at Belgian one-day race Scaahl Sels three weeks later.
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Attilio is the younger brother of Italian sprint star Elia Viviani - also set to join Cofidis next season - and so much will be expected of him, though he says he has already 'settled in'.
"I'm really happy here on the team, said Attilio. "I'm trying to learn French, and am happy that I can already understand what's being said at the race briefings.
"I was given an opportunity to win a race early on, and that gave me a huge amount of confidence...I'll be doing everything I can for the team in the coming weeks and next season.
21-year-old Fine debuted with the tea, at La Poly Normande in mid-August, and drew praise for the way he rode for his teammates at the Tour du Limousin. He is also due to represent France at under-21 level at the upcoming UCI Road World Championships in Yorkshire.
He said: "I'm really proud to be turning pro with such a renowned team as Cofidis. It's a huge challenge, but I'll be doing everything I can to meet expectations and repay the faith put into me."
Cofidis team manager Cedric Vasseur also expressed his excitement at having Attilio and Fine on board.
"It's always a pleasure, but also a duty, to allow young amateur riders to reach a milestone by joining the ranks of the professionals," said Vasseur. "Attilio and Eddy have already impressed the whole team, and we're excited to be able to count on them for next season."