Tentatively executing an entity includes identifying a runtime data element used by the entity, the runtime data element having a first value at a particular point based on a trace of a prior execution of the entity. Input specifying a second, different, value for the runtime data element is received. A tentative replay of the entity is performed, the tentative replay applying the second, different, value for the runtime data element using the trace. The tentative replay includes setting the runtime data element to the second value and emulating one or more memory writes performed by the entity during the tentative replay. Based on determining that the entity has requested data from the trace during the tentative replay that is not available in the trace, it is detected that the tentative replay has deviated from the prior execution and can no longer continue using the trace.