Jost captained Canada at the 2016 IIHF World U18 Championships in Grand Forks, North Dakota, where he led the tournament in scoring with 15 points in seven games. His points total established a Canadian record at that event, surpassing the previous mark set by Connor McDavid (14) in 2013. Despite placing out of the medals, Jost was selected as the tournament's “Best Forward” and was named to the All-Star Team. On April 30, 2018, Jost was a late addition to Team Canada's senior roster to compete at the 2018 IIHF World Championship. After sitting out as a healthy scratch for the opening round-robin game, Jost drew into the lineup and played his first game at the senior level, scoring two goals and an assist in a 10-0 blowout victory over South Korea on May 6, 2018. Jost played the remainder of the tournament with Nicolas Roy and teammate Fabbro as Canada placed fourth overall.