(Reuters) - San Francisco 49ers offensive tackle Trent Williams has agreed a six-year deal worth $138.06 million to stay with the franchise, his agency said on Wednesday. The deal includes $55.1 million in fully guaranteed money and a $30.1 million signing bonus, making him the highest paid offensive lineman in NFL history, NFL Network said. Eight-time Pro Bowler Williams, 32, was drafted by the Washington Football Team with the fourth overall pick in 2010. He spent nine seasons in Washington before his relationship with the team soured and he was acquired by the 49ers in the off-season last year. Williams started 14 games for San Francisco last season and finished with the fourth-best pass-block win rate (93.6%) among offensive tackles.