This report introduces the "Time Stepping Package for Optimization", or TSOpt, which is an interface for time-stepping simulation written in C++. It packages a simulator together with its derivatives (\sensitivities") and adjoint derivatives with respect to simulation parameters in a single object called a Jet, which can be used in conjunction with an optimization algorithm to solve a simulation-driven optimization problem. Further, TSOpt interfaces with the Rice Vector Library (RVL), allowing Jet objects to define a Operator subclass.