Reliable Chain-of-Thought via Prefix Consistency

Fuente: arXiv
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Auteurs principaux: Iwase, Naoto, Ichihara, Yuki, Quamar, Mohammad Atif, Komiyama, Junpei
Format: Preprint
Publié: 2026
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author Iwase, Naoto
Ichihara, Yuki
Quamar, Mohammad Atif
Komiyama, Junpei
author_facet Iwase, Naoto
Ichihara, Yuki
Quamar, Mohammad Atif
Komiyama, Junpei
contents Large Language Models often improve accuracy on reasoning tasks by sampling multiple Chain-of-Thought (CoT) traces and aggregating them with majority voting (MV), a test-time technique called self-consistency. When we truncate a CoT partway through and regenerate the remainder, we observe that traces with correct answers reproduce their original answer more often than traces with wrong answers. We use this difference as a reliability signal, prefix consistency, that weights each candidate answer by how often it reappears under regeneration. It requires no access to token log-probabilities or self-rating prompts. Across five reasoning models and four math and science benchmarks, prefix consistency is the best correctness predictor in most settings, and reweighting votes by it reaches Standard MV plateau accuracy at up to 21x fewer tokens (median 4.6x). Our code is available at https://github.com/naoto-iwase/prefix-consistency.
format Preprint
id arxiv_https___arxiv_org_abs_2605_07654
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Reliable Chain-of-Thought via Prefix Consistency
Iwase, Naoto
Ichihara, Yuki
Quamar, Mohammad Atif
Komiyama, Junpei
Machine Learning
Computation and Language
Large Language Models often improve accuracy on reasoning tasks by sampling multiple Chain-of-Thought (CoT) traces and aggregating them with majority voting (MV), a test-time technique called self-consistency. When we truncate a CoT partway through and regenerate the remainder, we observe that traces with correct answers reproduce their original answer more often than traces with wrong answers. We use this difference as a reliability signal, prefix consistency, that weights each candidate answer by how often it reappears under regeneration. It requires no access to token log-probabilities or self-rating prompts. Across five reasoning models and four math and science benchmarks, prefix consistency is the best correctness predictor in most settings, and reweighting votes by it reaches Standard MV plateau accuracy at up to 21x fewer tokens (median 4.6x). Our code is available at https://github.com/naoto-iwase/prefix-consistency.
title Reliable Chain-of-Thought via Prefix Consistency
topic Machine Learning
Computation and Language
url https://arxiv.org/abs/2605.07654