compromised diagonal
A diagonal connection that looks sound but can be vulnerable to a cut.
A compromised diagonal is a diagonal connection between stones that has been weakened, or made vulnerable to a cutting tactic, by the surrounding stones. The stones may appear connected, yet an opponent can exploit a nearby cutting point because the usual supporting stones or liberties are absent or compromised.
Recognizing this weakness helps a player decide whether to cut the shape or reinforce it. Unlike an ordinary kosumi, a compromised diagonal is not reliably connected: its status depends on the surrounding position. Whether it can actually be cut must be read from the local liberties and surrounding stones; the diagonal shape alone does not determine the result.