We tested the nature of validity sequence effects. During visual search for targets, target-preceding peripheral cues at target position (valid condition) facilitate search relative to cues away from the target (invalid condition). This validity effect (i.e., advantage in valid compared to invalid conditions) is observed for cues that are not predictive of the target, and it reflects the cue’s capture of attention. Importantly, the validity effect is stronger following valid than invalid trials. The underlying causes of this validity sequence effect are unknown. We, therefore, tested if the validity sequence effect reflected trial-to-trial priming or event-file coding. According to these explanations, full trial-to-trial repetitions and full changes of all stimulus features or of all stimulus and response features, respectively, would account for the validity sequence effect. However, the validity sequence effect could also reflect the participants’ retention of a recently helpful cue (i.e., after a valid trial) and/or their suppression of a recently harmful cue (i.e., after an invalid trial). Here, to contrastively test these theories, from trial to trial, the tasks are repeated or switched. The results demonstrated that, under certain conditions, the validity sequence effect can survive task-switching (Experiments 1 and 2), which supports the retention/suppression account. When the tasks were strongly distinguished, however, the validity sequence effect did not survive task-switching (Experiment 3), which supports the event-coding account. Together, the results suggest that task structure can determine the impact of cue processing on subsequent trials, and the extent to which it reflects event-file coding.