As a freshman at Florida State in 2023, Arnold appeared in 24 games and went 2โ5 with a 6.34 ERA over 44 innings.[3] He played in the Cape Cod Baseball League for the Hyannis Harbor Hawks after the season and was named an All-Star.[4][5] As a sophomore in 2024, Arnold started 18 games and posted an 11โ3 record, a 2.98 ERA, and 159 strikeouts over 105+2⁄3 innings and was named an All-American.[6] After the season, he was selected to play for the USA Baseball Collegiate National Team and was the starting pitcher in a combined no-hitter in a games versus Chinese Taipei.[7]