Paper Detail

CoBa: Cost-Effective Test-Time Scaling via Compute-Balanced Routing

Yan Zhou, Yue Ouyang, Kaiyang Zheng, Suncheng Xiang

arxiv Score 12.2

Published 2026-08-07 · First seen 2026-08-10

General AI

Abstract

Test-time scaling is often implemented by spending more compute along one axis: sampling more solutions, extending a chain of thought, or applying a stronger evaluator. Under a fixed inference budget, these choices compete. This paper formulates test-time reasoning as a compute-allocation problem in which a system must decide whether the next unit of compute should be spent on generation, verification, or stopping. We introduce CoBa, a compute-balanced routing policy that first obtains a small set of candidates, applies cheap verification broadly, and routes uncertain or high-value candidates to stronger verification. On 3,129 example-generator evaluations spanning MATH-500, AIME 2024/2025, AMC 2023, and procedural symbolic reasoning, CoBa-Routed-Strong reaches 85.13% macro accuracy, statistically matching a self-evaluation weighted-voting proxy at 85.20% while using 49.1% fewer parameter-weighted tokens. It also matches best-of-16 majority voting within 0.01 macro-accuracy points while using 58.9% fewer parameter-weighted tokens; paired tests retain a small best-of-16 edge at substantially higher cost. Paired bootstrap tests show significant gains over single-sample decoding, while the remaining gap to the pool oracle exposes headroom for sharper routing. For local reasoning systems, test-time scaling becomes a question of where the next computation is most valuable.

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BibTeX

@article{zhou2026coba,
  title = {CoBa: Cost-Effective Test-Time Scaling via Compute-Balanced Routing},
  author = {Yan Zhou and Yue Ouyang and Kaiyang Zheng and Suncheng Xiang},
  year = {2026},
  abstract = {Test-time scaling is often implemented by spending more compute along one axis: sampling more solutions, extending a chain of thought, or applying a stronger evaluator. Under a fixed inference budget, these choices compete. This paper formulates test-time reasoning as a compute-allocation problem in which a system must decide whether the next unit of compute should be spent on generation, verification, or stopping. We introduce CoBa, a compute-balanced routing policy that first obtains a small s},
  url = {https://arxiv.org/abs/2608.07424},
  keywords = {cs.AI},
  eprint = {2608.07424},
  archiveprefix = {arXiv},
}

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