Request difficulty in a production system is not normally distributed; it has a long thin tail. Most requests are routine — a classification, a lookup, a summary of a short document, a rewrite. A small proportion are genuinely hard, and a smaller proportion still are hard in ways that need the best available model.
Sending the whole distribution to a frontier API means paying tail prices for the body. Sending it all to a local model means the tail fails, visibly, and users generalise from those failures to the whole system. Routing lets each part go where it belongs, and the cost curve that results looks nothing like either extreme.
The same logic applies to sensitivity, and this is the axis that matters more for a regulated client. Some requests touch material that must not leave the building; most do not. A gate that routes on sensitivity as well as difficulty means the confidential subset is structurally incapable of escalating, while everything else keeps access to the best model available.
For requests eligible for a hosted decision service, our Jev model-router design explores fast task assessment and verification before escalation. Jev itself must pass the same data-handling constraints as any other external provider.