Model rollout is the operational process of moving a new model from testing into production — typically not all at once, but in staged phases. A team might first deploy to 1% of traffic, monitor for behavioral anomalies and performance regressions, then expand to 10%, then 50%, then full rollout. This staged approach limits the blast radius if something unexpected goes wrong: catching a behavioral regression when it affects 1% of users is far better than discovering it after full deployment. For behavior architects, rollout is when months of evaluation and design decisions meet reality — it’s where you learn which behavioral concerns were correctly anticipated and which unexpected issues appear only under real-world usage patterns.