pKso = 15.66
is sometimes called pseudohalide - and for a reason
Just like SCN-
and others I am not sure about (N3-
However, AgCN is a fancy compound
While it is only weakly soluble, Ag(CN)2-
complex has high stability constant (log K = 20.48). In effect reaction
2AgCN(s) <-> Ag(CN)2-
increases AgCN solubility.
That's what I suspect from the very beginning, I am just not sure.