Chosei

Chosei, also known as an “infinite cycle,” is an exceptionally rare situation in Go where both players are stuck in an endless loop of repeating moves with no way to break the cycle. Unlike a ko, where players can choose to play elsewhere to resolve the repetition, in chosei, there’s no alternative—the cycle is unavoidable and the game can’t progress unless one of the players agrees to suffer a loss by breaking the sequence.

This situation is so rare that it’s more of a theoretical curiosity than something you’re likely to encounter in actual play. Still, it’s an interesting quirk of the game that highlights the depth and complexity of Go’s rules.

Japanese and Korean rules usually declare chosei a void game (no result), meaning neither player wins or loses, while Chinese rules allow for special handling of such cycles, often requiring intervention to determine a fair outcome. On the other hand, Superko rules—used in many modern formats—forbid exact board repetitions, effectively preventing chosei from occurring altogether.