64% lower median cost, with no measurable quality change
The authors report that a model router for LangChain’s Open SWE coding agent reduced median cost per thread by 64% against their previous baseline of always using a top-tier frontier model. They report no measurable change in quality in that comparison.
Supporting evidence
How to Build a Model Router in the Harness
Original excerpt
Compared to our previous baseline of always using a top-tier frontier model, it cut median cost per thread by 64% with no measurable change in quality.
Context
We felt this pain recently at LangChain as our monthly coding agent spend started to climb rapidly. Hearing the same concern from customers, we set out to build an effective model router for Open SWE , our open source coding agent. This post covers how we built the router, what we learned, and how you can get started building model routing into your agents.