• Individuals of at least 25 years of age or older;

• Diagnosed with OUD as per DSM-5 criteria;

• Initiated or re-initiated methadone-based OAT within the past 30 days prior to study entry;

• Cannabis-use experienced, defined as having used any amount of cannabis in the six months prior to the screening visit;

• Willing to only use study-provided cannabis as directed by study protocol, including abstention from non-study cannabis and cannabinoids;

• Agree to keep all study medication stored in a secure location and not to share/distribute study medication to any other individual;

• If assigned female sex at birth:

‣ Be of non-childbearing potential, defined as (i) postmenopausal (12 months of spontaneous amenorrhea and over 45 years of age); or (ii) documented surgical sterilization (i.e., tubal ligation, hysterectomy, or bilateral oophorectomy); or

⁃ If of childbearing potential, be willing to use an acceptable method of contraception throughout the study and have a negative pregnancy test at screening;

• Ability to understand and comply with study protocol procedures and to provide written informed consent.

∙ In addition to meeting all eligibility criteria outlined in Phase 1, participants will be eligible for Phase 2 provided they meet ALL the following criteria at Week 12:

• Participants who have not experienced a study medication-related serious adverse event during Phase 1;

• Participants who have not been lost to follow-up during Phase 1.