IBM Research: LLM routing is a systems optimization problem

LangChain · x · 2026-07-20

IBM Research argues that LLM routing should be treated as a systems-optimization problem rather than a pure classification task.

The key example: Claude Sonnet 4.6 ended up costing about half as much as GPT-4.1 per task because caching effects dominated the economics, even though its sticker price was higher.

The takeaway is that real-world routing decisions need to account for infrastructure-level effects such as cache reuse, not just headline pricing or model labels.

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