Do Not Add an LLM Router Until You Can Defend Each Downgrade

Cost optimization is not a model-picker problem

When an LLM bill grows, the tempting answer is a blanket model downgrade. That is usually the wrong first move. A support classification, a retrieval rewrite, and a complex planning step do not have the same failure cost.

The useful question is: which calls have evidence that they can be cheaper?

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The useful design choice: analysis before automation

The interesting part is not a headline saving. It is converting a bill into a reviewable hypothesis:

1. Collect a bounded, sanitized sample of real calls.


2. Identify call groups that are candidates for a cheaper model.


3. Run a task-specific regression suite against those groups.


4. Automate routing only for groups that pass.

That sequence is boring in the best way. It creates an artifact an engineering team can challenge, reproduce, and roll back.

A local capture still has security boundaries

Frugon also includes frugon capture. Its and public repository are linked for further review.