How Semantic Routing Cut My LLM Costs by 70% Without Touching Model Quality

Originally published on robatdasorvi.com

I spent the better part of a year defending a decision I now think was wrong: routing every single request to the biggest model available because I was scared of the alternative looking cheap. Semantic routing for LLM cost reduction isn't a research curiosity anymore. It's the difference between an agent stack that survives its own success and one that gets killed in a budget review the first time usage 10x's. I found that out by almost getting killed in a budget review.

Here's the part nobody wants to say in public: most of us aren't routing based on task difficulty. We're routing based on vibes, and then writing blog posts that make the vibes sound like architecture.

What Is Semantic Routing, Actually?

Semantic routing is a classifier, usually a small embedding model or a lightweight LLM, that sits in front of your model calls and decides which model should handle a given request based on the meaning and difficulty of the query, not just its length or source. The direct answer is: it's a traffic cop, not a genius.

How Semantic Routing Cut My LLM Costs by 70% Without Touching Model Quality

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