Chosei

Chosei, also known as Eternal life, is a special repeating position in which stones can be captured and recaptured in an endless cycle, preventing the position from resolving.

In the capture sequence, the board eventually returns to an earlier position. This creates perpetual repetition rather than an ordinary finished ko fight. Unlike an ordinary ko, chosei is a larger or more complex repeating configuration whose cycle cannot be settled through the usual exchange of ko threats. It is used to describe and adjudicate this exceptional cyclic position. The result depends on the ruleset: repetition may be prohibited, or rules that permit it may declare the game no result.