The Athletics signed Hartlieb to a minor-league contract Wednesday.
Hartlieb was torched for eight runs over 3.1 innings during his brief time in the majors in 2025, but he boasted a 62:17 K:BB over 53.1 frames at the Triple-A level. The right-handed reliever will likely begin the 2026 campaign in the bullpen at Triple-A Las Vegas.