Thornton was reinstated to the 49ers active roster Monday, Field Yates of ESPN reports.

EDGE Analysis

After announcing his retirement last August, Thornton now rejoins the NFL on the first day of the 49ers offseason program. The 30-year-old has spent time with the Eagles, Cowboys and Bills across seven seasons, and has appeared in 89 career games with 48 starts, 278 tackles and 7.5 sacks. He projects to compete for a depth role along the defensive line this offseason.