The Royals signed Bummer to a minor-league contract Monday, Jon Heyman of the New York Post reports.
Bummer held a 7.63 ERA in 19 appearances for Atlanta earlier this season and has permitted four runs with a 6:2 K:BB over six innings during his time in the minors in 2026. The lefty reliever had a 26.9 percent strikeout rate in his first eight major-league seasons, but his strikeouts and velocity have both been down the last two years.