How to Steal Reasoning Without Reasoning Traces

Fuente: arXiv
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Main Authors: Zhang, Tingwei, Morris, John X., Shmatikov, Vitaly
Format: Preprint
Published: 2026
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author Zhang, Tingwei
Morris, John X.
Shmatikov, Vitaly
author_facet Zhang, Tingwei
Morris, John X.
Shmatikov, Vitaly
contents Many large language models (LLMs) use reasoning to generate responses but do not reveal their full reasoning traces (a.k.a. chains of thought), instead outputting only final answers and brief reasoning summaries. To demonstrate that hiding reasoning traces does not prevent users from "stealing" a model's reasoning capabilities, we introduce trace inversion models that, given only the inputs, answers, and (optionally) reasoning summaries exposed by a target model, generate detailed, synthetic reasoning traces. We show that (1) traces synthesized by trace inversion have high overlap with the ground-truth reasoning traces (when available), and (2) fine-tuning student models on inverted traces substantially improves their reasoning and enables distillation from proprietary, black-box LLMs.
format Preprint
id arxiv_https___arxiv_org_abs_2603_07267
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle How to Steal Reasoning Without Reasoning Traces
Zhang, Tingwei
Morris, John X.
Shmatikov, Vitaly
Cryptography and Security
Many large language models (LLMs) use reasoning to generate responses but do not reveal their full reasoning traces (a.k.a. chains of thought), instead outputting only final answers and brief reasoning summaries. To demonstrate that hiding reasoning traces does not prevent users from "stealing" a model's reasoning capabilities, we introduce trace inversion models that, given only the inputs, answers, and (optionally) reasoning summaries exposed by a target model, generate detailed, synthetic reasoning traces. We show that (1) traces synthesized by trace inversion have high overlap with the ground-truth reasoning traces (when available), and (2) fine-tuning student models on inverted traces substantially improves their reasoning and enables distillation from proprietary, black-box LLMs.
title How to Steal Reasoning Without Reasoning Traces
topic Cryptography and Security
url https://arxiv.org/abs/2603.07267