Thrun joined the USNTDP for the
2017–18 season and recorded three goals and 17 assists in 32 games for the U-17 team. He returned to the USNTDP for the
2018–19 season and recorded four goals and 19 assists in 28 games.
College He began his
collegiate career for the
Harvard Crimson during the
2019–20 season. He scored his first career goal on November 1, 2019. During his freshman year he recorded three goals and 18 assists in 31 games, and led the team with a plus-17 rating. Following an outstanding season, he was named a finalist for the
ECAC Hockey Best Defensive Defenseman and was named to the
All-ECAC Rookie Team. He recorded eight goals and 14 assists in 24 games for the Fighting Saints. His 0.92 points per game average ranked second among defensemen. Following the season he was named to All-USHL Third Team. Thrun finished the
2022–23 season with seven goals and 24 assists in 33 games, leading all defenseman in the
ECAC with 0.94 points per game. He finished the year with a
plus-minus rating of +20. Thrun was named the
ECAC Hockey Best Defensive Defenseman, as well as
ECAC First-Team and an
AHCA East First Team All-American. After the conclusion of the Sharks' season, Thrun returned to Harvard to finish his
bachelor's degree as a double major in
economics and
psychology.
Professional On February 15, 2023, Thrun, notified the
Anaheim Ducks that he intended to test free agency rather than sign with them when his rights expired in August 2023. Thrun's rights were subsequently traded to the
San Jose Sharks on February 28. At the conclusion of his junior season with the Crimson, Thrun was signed by the Sharks to a two-year, entry-level contract on March 25, 2023, and joined the team immediately. Thrun played his first NHL game on March 23, 2023, against the
Vegas Golden Knights, where he recorded two assists in the Sharks' 4–3
overtime victory. Thrun scored his first career goal on January 9, 2024, the lone Sharks goal in a 7–1 loss to the
Toronto Maple Leafs. On April 14, 2024, Thrun was voted 2023–24 Sharks Rookie of the Year by the Bay Area media. On July 24, 2024, he signed a two-year contract extension with the Sharks. During the
2024–25 season, he recorded two goals and ten assists in 60 games. On July 10, 2025, Thrun was traded to the Toronto Maple Leafs in exchange for
Ryan Reaves. ==International play==