[4][5] During the 2023–24 season, he recorded 18 goals and 29 assists in 26 games for the NTDP in the United States Hockey League (USHL).
[7][8] Hagens represented the United States at the 2022 World U-17 Hockey Challenge where he recorded eight goals and 13 assists in seven games and won a gold medal.
[9][10] He represented the United States at the 2023 IIHF World U18 Championships, where he recorded one goal and four assists in seven games and won a gold medal.
[13][14] He again represented the United States at the 2024 IIHF World U18 Championships, where he led the tournament in scoring with nine goals and 13 assists in seven games and won a silver medal.
[18][19] Hagens' brother, Michael, is also an ice hockey player committed to play at Boston College.