  In this note we show how the 1-loop exact correction to the subleading soft
graviton theorem arising from IR divergences of scattering amplitudes matches
onto the quadratic corrections to the soft charges computed from the BMS flux
algebra. In the process, we examine how the BMS flux construction extends the
celestial diamond framework to non-linear order and non-trivial vacua, and
provides the natural symmetry generators for Celestial CFT.
