Start here. This is the direct spoken answer to practice first.
Overview
Observed quality can change even when the application repository has not.
I watch quality and operational metrics over time by task slice and deployed version, using stable anchor cases plus sampled current traffic. A shift can come from user behavior, source data, tools, retrieval, provider models, moderation, or the grader itself. Versioned traces and deployment markers let me separate those causes instead of calling every change model drift.