The ability to adapt behavior based on changing feedback, internal goals, extrinsic demands, or environmental contexts requires cognitive flexibility [1]. Cognitive flexibility improves from childhood to adulthood, with greater flexibility correlating with improved academic, occupational, and mental health outcomes [2]. Understanding developmental underpinnings of age-related enhancements in cognitive flexibility may thus inform efforts to foster healthy neurocognitive trajectories. Given the dynamic nature of flexibility, substantial work examining its neural origins has studied the essential role of ongoing brain dynamics, or neural variability, defined as time-dependent changes in the expression of brain activity. Here, we aim to parse multifaceted relationships between two developmentally dissociable domains of flexibility — cognitive shifting and contingency-based switching — and the maturational processes that support them through the lens of multiscale neural variability and its generating neurobiological mechanisms. We consider how the ontogenesis of these two domains of flexibility, while temporally distinct, may be interrelated. We propose a testable developmental framework wherein flexible behavior during reward seeking and contingency-based switching in adolescence leads to stochastic exploration, behavioral variability, and environmental sampling, which, in turn, support the refinement of brain processes required for efficient cognitive shifting in adulthood.