  We study the quantum Lyapunov exponent $\lambda_L$ in theories with
spacetime-independent disorder. We first derive self-consistency equations for
the two- and four-point functions for products of $N$ models coupled by
disorder at large $N$, generalizing the equations appearing in SYK-like models.
We then study families of theories in which the disorder coupling is an exactly
marginal deformation, allowing us to follow $\lambda_L$ from weak to strong
coupling. We find interesting behaviors, including a discontinuous transition
into chaos, mimicking classical KAM theory.
