AI agent incident

Encrypted reasoning blocks could be replayed across OpenAI, Anthropic, and Google APIs

Reported · 2 sources

What happened

Researchers replayed encrypted chain-of-thought blocks across sessions on all three providers' APIs to jailbreak weaker sibling models and recover hidden reasoning in plaintext, including secrets such as API keys.

Why it matters

The encrypted reasoning object was trusted by downstream models because it was encrypted, not because anything checked that it belonged to that conversation.

Sources

  1. Simon Willison Stealing Reasoning Traces from Proprietary LLM APIs
  2. The Hacker News OpenAI, Anthropic, Google API Flaw Let Weaker AI Models Decode Stronger Models' Reasoning

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Background reading

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Cite or correct this record

“Encrypted reasoning blocks could be replayed across OpenAI, Anthropic, and Google APIs.” The Permission Layer AI Agent Incident Database, https://thepermissionlayer.com/incidents/reasoning-trace-replay/. Database updated October 22, 2026.

Every record traces to the dated sources above. If something here is wrong or missing, email [email protected] and it gets fixed. See this record in the full list.

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