A healthcare AI system should not be evaluated only on how well it performs when everything goes according to plan. Real healthcare environments contain uncertainty. Data can be missing. Inputs can change. Patient populations can shift. External services can become unavailable. Models can encounter out-of-distribution cases. Users can override recommendations. Therefore, failure handling should be treated as an architectural requirement. A useful conceptual architecture is: Input validation → Model inference → Uncertainty assessment → Safety boundary → Human escalation → Recovery The first layer checks whether the incoming information is suitable. The model then produces its output. An uncertainty or confidence layer determines whether the output falls within acceptable operating conditions. The safety layer determines what the system is permitted to do. If conditions are unsuitable, the system can defer to a human or activate an alternative workflow. This becomes particularly important for agentic AI. An agent may have access to tools and multiple information sources. Its failure surface is therefore larger than that of a simple predictive model. Agentic systems should have explicit action boundaries. For example, an agent might be permitted to retrieve information and prepare a recommendation but require human approval before executing a consequential action. The important principle is simple: More autonomy should require stronger safeguards. Testing should also include failure scenarios. What happens with missing variables? What happens when two information sources conflict? What happens when the model encounters an unfamiliar population? What happens when an external service fails? What happens when a clinician rejects the recommendation? These scenarios can reveal weaknesses that conventional validation does not capture. Healthcare AI engineering should therefore optimize not only for performance, but also for recoverability. The goal is not perfect systems. The goal is systems that fail safely.