# Model routing

A step that picks, for each request, which model handles it, using a fixed rule or a model that judges the request.

Google for Developers (Machine Learning Glossary, 2026) says: “The algorithm that determines the ideal model for inference in model cascading. A model router is itself typically a machine learning model that gradually learns how to pick the best model for a given input. However, a model router could sometimes be a simpler, non-machine learning algorithm.” In practice, many routers are fixed rules. Cascading is a different method: it tries a cheap model first and moves up only if the answer isn't good enough.

Also called: LLM routing, Model cascading

Kind of: LLM gateway

Often confused with: Router agent

Source: https://redfinchadvisory.com/lexicon/model-routing (version 1.0, changed 2026-10-21)