💡 What it does
Trace inversion uses the visible reasoning summary as a scaffold. The model aims to preserve the broad order and intent of the supplied bubbles while filling in intermediate steps, producing output in a <think>...</think> block. It is intended for research and synthetic-data workflows rather than as a general-purpose answer model.
The generated trace is not the original hidden reasoning of Claude or any other source model. It is a model-generated reconstruction, and should be labelled as synthetic.
📚 Training data
The model uses 11100 training- and 555 evaluation-entries from the following datasets (also used by the NoBubble reference model):
The key fields have been mapped and converted to this dataset: xtools-at/trace-inversion-opus-synthetic
The reasoning bubble is retained in the prompt at inference time.
🛠️ Usage
Include all three ingredients—the problem, the answer, and the reasoning bubble(s)—in the prompt. For example:
System
You are a trace inversion model. Given a problem, a final answer, and several compressed reasoning bubbles, reconstruct a detailed reasoning trace that could plausibly lead to the final answer. Follow these rules:- Treat the reasoning bubbles as the skeleton of the trace.- Expand each bubble into coherent reasoning while preserving the original logical order.- Keep the trace consistent with the problem and the final answer.- Do not introduce unrelated methods, new assumptions, or a different conclusion.- Output only the reconstructed reasoning trace wrapped in <think>...</think>.
User
Problem:{problem} Model's final answer:{final_answer} Reasoning Bubbles:{reasoning_bubbles} Reconstruct the full reasoning trace.
Expected output shape:
<think>{synthetic reconstructed trace}</think>
Use the model's supported Qwen3.5 processor/model classes and chat template for inference. Generation settings can affect trace length and style, so validate outputs before adding them to a training dataset.
🎯 Intended uses
- Expanding compressed reasoning summaries into candidate synthetic traces.
- Research into trace inversion and reasoning supervision.
- Creating draft examples for downstream supervised fine-tuning, after careful filtering and verification.
⚠️ Limitations & responsible use
- Synthetic, not recovered: outputs are reconstructions, not verified private reasoning from a source model.
- Answer-conditioned: the model treats the supplied final answer as a constraint and may produce a convincing explanation for an incorrect answer.
- Bubbles matter: this model is designed to receive reasoning bubble(s); omitting them is outside its intended input setup and may reduce quality.
- Verify before reuse: check calculations, run code where relevant, and fact-check claims before using traces as supervision.
- Research use: do not rely on generated traces as proof of correctness or for high-stakes medical, legal, or financial decisions. Follow applicable model and dataset terms when using or redistributing outputs.
@misc{zhang2026stealreasoning, title = {How to Steal Reasoning Without Reasoning Traces}, author = {Tingwei Zhang and John X. Morris and Vitaly Shmatikov}, year = {2026}, eprint = {2603.07267}, archivePrefix = {arXiv}}