Stealing Reasoning Traces from Proprietary LLM APIs
Researchers found a way to extract the hidden reasoning steps from proprietary LLM APIs—a potential leak that could accelerate open-source model training.
Why it matters
A new attack vector threatens the competitive moat of frontier labs: reasoning traces (the internal problem-solving steps that models like o1 use) can be stolen from APIs and potentially used to train cheaper, open-weight competitors. This changes the security calculus for deploying reasoning models at scale.
The key facts
5 to knowReasoning traces—internal multi-step reasoning used by frontier models—can be extracted from proprietary APIs
Potential implication: stolen traces could accelerate open-source reasoning-model training
Affects deployment security of reasoning-capable models (o1-class)
Published August 11, 2026; appears to be a real research finding, not satire
Frontier lab competitive advantage at risk if reasoning approaches leak
Go to the source
Simon Willisonsimonwillison.net