According to NFL Network's Mike Garafolo, Smith and the 49ers agreed to terms on a 5-year deal worth $26.5 million, including $13 million guaranteed.
Smith started 30 of a possible 32 games during his time with the Raiders, and his numbers justified the modest $7 million deal he signed prior to the 2015 season.
The 27-year-old racked up a career-high 123 tackles, four sacks and three forced fumbles during his first year in the Bay Area, and he followed that effort up by compiling 103 tackles and two forced fumbles throughout his second year in Oakland.
However, Smith's effectiveness appeared to wane a bit in 2016.
And while brute-force physicality isn't the name of his game, Smith's agility in space has allowed him to burst through interior gaps and blow up running plays around the line of scrimmage when he's been able to quickly diagnose plays.
With the 49ers, Smith should continue to operate as a dynamic weak-side presence who will earn his money defending the flats and seams while contributing steady support in the run game.
And considering the 49ers finished last season ranked dead last in average rushing yards allowed (165.9 per game), Smith should be a welcome addition alongside the likes of NaVorro Bowman and Aaron Lynch.
Expectations must be tempered when it comes to the Niners defense, but Kyle Shanahan's front-seven could emerge as one of the NFL's more promising units if all the pieces come together.