  We study the remnants of Yangian symmetry of AdS/CFT magnons reflecting from
boundaries with no degrees of freedom. We present the generalized twisted
boundary Yangian of open strings ending on boundaries which preserve only a
subalgebra h of the bulk algebra g, where (g,h) is a symmetric pair. This is
realized by open strings ending on the D3 brane known as the Y=0 maximal giant
graviton in AdS_5 x S^5. We also consider the Yangian symmetry of the boundary
which preserves an su(1|2) subalgebra only.
