Jackson was recalled from Triple-A Sacramento prior to Friday's game against the Cardinals, Kerry Crowley of The San Jose Mercury News reports.
Jackson signed a minor-league deal with San Francisco in March. He'll join the big-league roster after posting an impressive 18:1 K:BB across 11 scoreless innings with Sacramento. The right-hander last pitched in the majors with the Brewers in 2019, when he posted a 4.45 ERA and 47:18 K:BB across 30.1 innings.