Though Kapanen's playing time was limited at the Olympic Winter Games Milano Cortina 2026, he made the most of it by helping Team Finland win a bronze medal.

Kapanen replaced injured forward Mikko Rantanen and was moved to the first line with Sebastian Aho and Artturi Lehkonen for the third-place game, a 6-1 win against Team Slovakia and Montreal Canadiens teammate Juraj Slafkovsky. The victory gave Kapanen his second international medal after winning silver at the 2022 IIHF World Junior Championship and further entrenched his status with the Canadiens, who selected the Timra native in the second round (No. 64) of the 2021 NHL Draft. He signed a three-year, entry-level contract with Montreal on June 15, 2024, after playing 51 games for KalPa in Liiga, Finland's top professional hockey league (34 points; 14 goals, 20 assists). He also led Finland with six goals in eight games at the 2024 IIHF World Championship.

Kapanen joined Laval of the American Hockey League for the 2025 Calder Cup Playoffs, when he scored his first goal in North America to help the Rocket to a 5-4 win at Rochester in Game 1 of the North Division Finals. He scored his first NHL goal on opening night of the 2025-26 season, when the Canadiens lost 5-2 to the Toronto Maple Leafs at Scotiabank Arena on Oct. 8. Kapanen was the fifth player on record in Canadiens history to score his first NHL goal while short-handed, joining Chris Chelios (Oct. 13, 1984), Doug Jarvis (Nov. 8, 1975), Lawrence Pleau (March 11, 1970) and Jacques Laperriere (Nov. 9, 1963).