  Let $\textbf{G}$ be a simply connected semisimple algebraic group over a
field of characteristic greater than the Coxeter number. We construct a
monoidal action of the diagrammatic Hecke category on the principal block
$\text{Rep}_0(\textbf{G})$ of $\text{Rep}(\textbf{G})$ by wall-crossing
functors. This action was conjectured to exist by Riche-Williamson. Our method
uses constructible sheaves and relies on Smith-Treumann theory.
