Joseph-Day and the 49ers agreed on a contract Tuesday, Matt Barrows of The Athletic reports.
Joseph-Day was let go by the Chargers on Friday, but he has quickly found a new home with the 49ers a few days later. The 28-year-old has recorded 32 tackles, including 3.0 sacks, over 14 contests this season and he'll bolster an already stout defensive line with San Francisco.