A debugger executes on a computer system to receive a first debugging command from a client, where the first debugging command sets a first instruction in the reactive application to suspend execution of the reactive application, and where during execution of the reactive application the first instruction is triggered which suspends execution of the reactive application. Responsive to the execution of the reactive application being suspended, a system clock of the reactive application is replaced with a substitute clock and the substitute clock is paused. The debugger then receives a second debugging command, where the second debugging command triggers a second instruction in the reactive application to continue execution of the reactive application. Responsive to the execution of the reactive application being continued, clocking of the substitute clock is continued.