What is the speed of light in this model?

In this model c is proposed to be the maximum rate at which cause-and-effect can spread through the causal graph, not a constant added by hand. A foliation may only tilt so far before it would order effects before their causes, and that maximum legal tilt corresponds to a maximum signal speed. In the simplest string toy model this limit is concrete: information spreads at most one character per rewriting step. This is presented as a derivation within the model rather than established physics.