Current views posit that forming and retrieving memories of ongoing events influences action control. However, the organizational structure of these memories, or event files, remains unclear. The "hierarchical coding view" posits a hierarchical structure, wherein task sets occupy a high level of the hierarchy. Here, the contents of an event file can be retrieved only if the task set repeats. In contrast, the "binary coding view" posits a nonhierarchical structure, which consists of a collection of independent, binary bindings between different feature pairs. In this view, repeating an abstract feature from a previous event (e.g., the previous trial's S-R mapping) triggers the retrieval of the associated feature from the same binding (e.g., the previous trial's congruency) even if the task set changes. To distinguish between these views, we investigated the nature of task set boundaries for the congruency sequence effect (CSE), an index of adaptive control that reflects event file formation and retrieval. Specifically, we investigated whether or not a CSE appears when the task set changes but the previous trial's S-R mapping repeats. Three experiments involving a cross-modal prime-probe task yielded a CSE under these conditions and ruled out alternative explanations. These findings show that the typical binary structure of event files generalizes from concrete features (e.g., colors and locations) to abstract features (e.g., S-R mappings and task sets). Therefore, contrary to the hierarchical coding view, they provide a nonhierarchical explanation of task set boundaries for the CSE.