The primary objective of this protocol is to implement the UG3 phase (Phase 1) of a National Institute on Drug Abuse (NIDA) UG3/UH3 grant (RFA-DA-23-049). This phase is dedicated to the pilot testing of NEAT-O, a digital Cognitive Behavioral Therapy (CBT) program tailored for individuals with opioid use disorder (OUD) and concurrent anxiety or mood disorders - collectively referred to as internalizing disorders (INTDs). NEAT-O is based on an empirically supported CBT framework, specifically modified to address the complexities of comorbidity in substance use disorders (SUDs). This pilot study will evaluate the usability and acceptability of NEAT-O in 15 participants with OUD, with the goal of refining the program\'s content and delivery methods. The results of the pilot study will inform a comprehensive RCT in the UH3 Phase (Phase 2) (N=300). Progression to the UH3 phase, with its funding, depends on meeting milestones in Phase 1 including demonstrating protocol adherence and the program\'s acceptability and usability.