HackerPapers

arXiv:2603.07267cs.CR

How to Steal Reasoning Without Reasoning Traces

Tingwei Zhang, John X. Morris, Vitaly Shmatikov

Abstract

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.

arXiv comments
Journal reference
DOI
Subjects
cs.CRCryptography and Security

On Hacker News

Linked by 3 identifiable commenters in 3 comments across 3 threads, from Jun 2026 to Aug 2026.

Comments linking this paper, per year.

Discussed in comments3 threads

  1. GPT-5.6 Sol Pricing Cut by 50% 1 comment
    • You can train a LLM to inverse summarised thinking into thinking text. It’s not perfect, but it gets you maybe 80% of the quality with proper techniques. Paper: https://arxiv.org/abs/2603.07267 FWIW, there’s not that much value protected here anyway IMHO, and even raw thinking…

      dannywView on HNParent context

    • Really cool work, you get the actual traces. Looks like the vendors can all reliably fix this one though. A harder to defend against approach here where they work backwards from the results and ask the model to generate a plausible trace: How to Steal Reasoning Without Reasoning…

      nervaiView on HNParent context

    • It is quite likely that the intermediate tokens don’t have ‘semantic import’[0] There are methods like Habitual Reasoning Distillation or Inverted Reasoning Traces [1] that can help. While there are reasons to hide the intermediate tokens from a IP protection stand point, there…

      nyrikkiView on HNParent context

Submitted to Hacker News

Connected through shared HN threads, not inferred similarity or a recommendation.