Innate sensorimotor policies constrain cerebellar adaptive correction

Innate sensorimotor policies enable rapid and reliable behavior but can become ineffective when environments change. How these policies interact with feedback-driven processes to support behavioral flexibility remains unclear. Using closed-loop virtual reality in larval zebrafish, we reversed the visual consequences of self-generated turns. Larvae initially followed their innate mapping and then rapidly switched to corrective turns in the opposite direction. Purkinje cell ablation abolished this correction while preserving innate optomotor responses. Imaging revealed outcome-invariant sensorimotor representations in granule cells and an outcome-dependent modulation of inferior olive neurons and Purkinje cells. Correction weakened as the optic-flow angle increased, despite persistent error-related representations. The innate behavioral repertoire also shifted as the optic-flow angle increased, making corrective turns less likely. An actor-critic model initialized with the measured behavioral repertoire reproduced the limits of correction. Together, these results show that adaptive behavior emerges from the interaction between an innate feed-forward policy and an olivo-cerebellar instructive signal, revealing innate behavioral structure as a fundamental constraint on cerebellar adaptation.