What is model routing?
Model routing is the selection of a model per task rather than standardising a whole deployment on one. A routing layer holds the decision, so a model can be replaced for one class of work without the surrounding system being altered. The choice is expressed as configuration and recorded with each output.
Why the routing layer is the only defence against a vendor's roadmap
A deployment that calls one provider directly from forty places has made that provider a structural dependency, and the cost appears the first time a price changes or a model is withdrawn. Routing confines the decision to a single layer, which turns a migration into a configuration change for a defined set of tasks. The benefit regulated clients value most has nothing to do with price, since routing lets a task handling personal data go to a model in an approved jurisdiction while everything else goes elsewhere. The constraint becomes enforceable rather than documented.
- Routing makes a model a replaceable component rather than a dependency.
- Residency and approval constraints can be enforced at the routing layer.
- Inexpensive tasks stop paying for capability they never required.
- Each output carries the model that produced it, which an audit requires.
How model routing works
- Task types are classified by difficulty and by the constraints they carry.
- A preferred model is declared per task type with its justification recorded.
- The routing layer resolves the model at request time from configuration.
- Each candidate model is evaluated per task type before entering the configuration.
- The resolved model is recorded on the output alongside its version.
- Routing decisions are reviewed whenever a new model becomes available.
How model routing is evaluated
Routing is assessed on whether the choice improves outcomes and whether it remains traceable afterwards. Examine the following per task type:
- quality per task type against the single model baseline
- cost per task before and after the routing decision
- proportion of requests resolved to the intended model
- compliance of constrained tasks with their residency requirement
- share of outputs recording the model version used
Limitations, risks and common failure modes
- Routing rules accumulate until nobody can predict which model answers.
- A cheaper model is routed to a task type it was never evaluated on.
- Prompts tuned for one model degrade when another receives the same task.
- The routing configuration is changed without a record of who changed it.