In the PMI-CP in Managing AI guidance, monitoring and diagnosing AI model performance is framed as a lifecycle responsibility, not a one-time task. When a model that previously performed well suddenly shows increased error rates, PMI emphasizes first checking for data drift and concept drift—that is, changes in the distribution or meaning of the real-world input data compared with the data the model was trained and validated on. The material explains that teams should “systematically compare current production data distributions with training and validation distributions to detect shifts that may degrade model performance, even when the model architecture has not changed.” This is because many performance issues in production are driven not by the model code itself, but by changes in user behavior, population characteristics, upstream systems, or environmental conditions. By analyzing the distribution of real-world data for potential shifts, the project team can determine whether the cause is data drift, data quality issues, or a change in the underlying patterns the model is supposed to learn. Only once this is understood should they proceed to architectural changes, hyperparameter tuning, or retraining strategies. Therefore, the action that best identifies the root cause of the performance decline is to analyze the distribution of real-world data for potential shifts.