  We argue for an exponential bound characterizing the chaotic properties of
modular Hamiltonian flow of QFT subsystems. In holographic theories, maximal
modular chaos is reflected in the local Poincare symmetry about a
Ryu-Takayanagi surface. Generators of null deformations of the bulk extremal
surface map to modular scrambling modes -positive CFT operators saturating the
bound- and their algebra probes the bulk Riemann curvature, clarifying the
modular Berry curvature proposal of arXiv:1903.04493.
