arXiv AI

When LLM Routers Overpay: The Cost of Strong-Model Preference

arXiv AI
Oct 5

Dynamic LLM Routers are Often Misguided

Dynamic LLM routers aim to reduce inference costs by directing each query to the cheapest capable model. In a study of six commercial routers across 14 settings and eight task categories, none surpassed a simple random router that selects between two well-chosen models at the same cost, with some underperforming by over 10 percentage points. The authors identify four common patterns—difficulty blindness, length reversal, semantic matching, and roster suboptimality—that explain this gap and propose a new evaluation method and a simple two-model router that mitigates these patterns, though its advantage over random routing remains modest.

By Sam Wang, Julia White, Sahibzada Allahyar, Dhruv Atreja, Urchade Zaratiana, Kelton Zhang
arXiv AI
Sep 30

You Cannot Pick a Provider From the Price List: Market-Aware Routing for Open-Weight LLM Inference

The paper demonstrates that in open‑weight LLM inference markets, selecting a model is insufficient; clients must also choose a provider, as the same model can differ markedly in quality, latency, availability, and price across providers. The authors propose a market‑aware routing approach, including a measured‑map policy and an online router called FACET, which certifies provider feasibility for each task and safely falls back to a reliable anchor. Experiments show that this strategy yields cost savings while maintaining quality and avoiding degraded endpoints.

By Liang He, Jingbo Wen, Yixiong Chen, Yue Yang, Qizhen Lan, Kangning Cui, Xilu Wang
arXiv AI
Sep 30

Routing Should Pay for Itself: Sparse Supervision for Economical LLM Routing

The paper introduces SaveRouter, a sparse‑supervision framework for large language model routing that selectively gathers informative model feedback and shares capability information across related queries. By using only about 33–41% of available training feedback, SaveRouter achieves competitive or superior routing quality while reducing the break‑even deployment volume by 1.9–9.5× compared to conventional routers. The study also shows that the supervision level that minimizes serving cost may differ from the one that yields the earliest payback.

By Guannan Lai, Gelin Bian, Hao-Xuan Ma, Jun-Peng Jiang, Long Chen, Jian-Dong Liu, Zhi-Hao Tan, Han-Jia Ye
Hugging Face Trending Papers
Oct 22

Predictable performance is suboptimal, and what it means for model routing

The paper investigates how performance predictors can improve model routing for large language models (LLMs). It shows that a predictor only outperforms a model’s self‑confidence when the candidate model is suboptimal or the predictor adds significant capacity. The authors provide theoretical bounds, extend the analysis to two‑model cascades, and confirm that predictors help most with suboptimal models, with gains diminishing after fine‑tuning.

arXiv Machine Learning
Oct 23

Predictable performance is suboptimal, and what it means for model routing

The paper investigates how performance predictors can improve model routing for large language models (LLMs). It shows that a predictor only outperforms a model’s self‑confidence when the candidate model is suboptimal or the predictor adds significant capacity. The authors provide theoretical bounds, extend the analysis to two‑model cascades, and confirm their findings experimentally across 16 LLMs on four benchmarks, noting that the advantage diminishes as models are fine‑tuned.

By Guanhua Zhang, Moritz Hardt
arXiv Computation and Language
Oct 26

Cluster, Route, Escalate: Cascaded Framework for Cost-Aware LLM Serving

arXiv:2606.27457v2 Announce Type: replace-cross Abstract: Serving open-weight language models on premises forces a trade-off between accuracy and computational cost. Hosting models of different sizes...

By Yasmin Moslem, Magdalena Kacmajor, Vasudevan Nedumpozhimana, Ammar Abbas, Solmaz Panahi, David Lynch, Zhuangzhuang Nie, Alexandros Agapitos, Aleksandar Milenovic, Hongmeng Song, Yucheng Shi, Yue Pan, Patricia Buffini, John D. Kelleher