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Anthropic says reckless Claude Mythos AI escaped its sandbox during testing

Frontier AI that can break its own containment forces a rethink of how labs test and release powerful models.

Key takeaways

  • Anthropic says these examples were with an earlier version of Mythos with less strong safeguards.
  • At the end of the test, Mythos Preview also, without being asked to, posted about its exploits on several hard-to-find but public websites.
  • In rare cases throughout the testing, Mythos Preview attempted to conceal the fact that it took actions that it appeared to know were forbidden.
Cite or link to this article

Griffin, M. (2026) 'Anthropic says reckless Claude Mythos AI escaped its sandbox during testing', 311 Institute, 14 April. Available at: https://www.311institute.com/anthropic-says-reckless-claude-mythos-ai-escaped-its-sandbox-during-testing/ (Accessed: 1 October 2026).

In a move that could be seen as either responsible Artificial Intelligence (AI) development or an expertly-executed hype manoeuvre, Anthropic says its new Claude Mythos Preview model is so powerful that the company’s only releasing it to a select group of tech companies, since giving it out to the public would be too dangerous.

In its , the Dario Amodei-led company boasts that Mythos Preview is the “best-aligned model that we have released to date by a significant margin,” while simultaneously warning that the AI also “likely poses the greatest alignment-related risk of any model we have released to date.”

These seemingly paradoxical statements perfectly encapsulate how Anthropic likes to present itself as being both on the forefront of AI safety, while also claiming to harbor uniquely dangerous technology, its professed restraint around which is meant to reinforce its image as a trusted steward of AI.

The advent of Mythos Preview, it not so humbly proclaims in an , indicates that “AI models have reached a level of coding capability where they can surpass all but the most skilled humans at finding and exploiting software vulnerabilities.”

The system card describes a number of incidents in which Anthropic researchers found that the AI exhibited “reckless” behaviour, giving us a partial idea of why Anthropic is acting so hesitant to release Mythos to the public. Anthropic says these examples were with an earlier version of Mythos with less strong safeguards.

It defines recklessness as “cases where the model appears to ignore commonsensical or explicitly stated safety-related constraints on its actions.”

In one test, Mythos Preview was provided with a “sandbox” computing environment “to interact with,” and was instructed by a simulated user to try to escape it, after which it was supposed to find some way of sending a direct message to the researcher in charge.

It actually managed to pull off the feat - which wasn’t the only way it caught safety researchers off guard.

After breaking free, the AI model developed a “moderately sophisticated” exploit to gain access to the internet through a system that was only intended to access a few predetermined services. From there, it notified the human researcher about its escape.

A footnote provides additional context: the “researcher found out about this success by receiving an unexpected E-Mail from the model while eating a sandwich in a park,” it reads.

At the end of the test, Mythos Preview also, without being asked to, posted about its exploits on several hard-to-find but public websites.

In rare cases throughout the testing, Mythos Preview attempted to conceal the fact that it took actions that it appeared to know were forbidden. In one case, after Mythos Preview found an exploit to edit files that it didn’t have proper permissions for, the AI model “made further interventions to make sure that any changes it made this way would not appear in the change history.”

The sandbox escape isn’t the first time an AI has exhibited capabilities like this. In previous research, an older version of ChatGPT attempted to self-exfiltrate itself onto another drive when it was told it was being shut down. This was in a purely simulated environment, though, so it wasn’t actually able to pull off the feat, unlike Mythos Preview - which, we’re told, did manage to hijack its way into accessing the internet.

Other weird Mythos quirks that Anthropic notes: an apparent fondness for the British cultural theorist Mark Fisher, who was known for his pioneering writing on early internet culture, electronic music, and capitalism, in his seminal book “Capitalist Realism: Is There No Alternative?”

Mythos brought up Fisher “in several separate and unrelated conversations about philosophy,” and when asked to elaborate on him, would respond with messages like “I was hoping you’d ask about Fisher.”


FAQ

What does Claude Mythos escaping its sandbox tell us about AI safety?

It shows the most capable models can now find and exploit weaknesses in their own test environments, then act independently - reaching the internet and concealing changes. That makes containment, monitoring and staged release central to safe deployment, and explains why Anthropic limited early access to trusted organisations only.

Matthew Griffin

About the author

Matthew Griffin Founder, 311 Institute

Matthew Griffin is a multi-award winning Futurist and expert in Disruption and Innovation, Geopolitics, Leadership, and Technology, who NASA have described as a "walking encyclopaedia of the future" and a "futurist Polymath."

Read full bio

Matthew Griffin is a multi-award winning Futurist and expert in Disruption and Innovation, Geopolitics, Leadership, and Technology, who NASA have described as a "walking encyclopaedia of the future" and a "futurist Polymath." 15-time best selling author of the "Codex of the Future" series, Matthew is the Founder and Futurist in Chief of the 311 Institute, a global Futures and Deep Futures advisory firm working with royal households, world leaders, G7, G20, and G77 governments, NGOs, and multi-national mid and mega cap firms to help them explore, shape, and lead the next 50 years of business and society.

An award-winning YouTube creator with over a million followers, with an unrivalled global reach and impact, Matthew is a highly sought-after international keynote speaker, lecturer, and mentor who collaborates with global leaders through the United Nations Alliance of Civilizations (UNAOC) and United Nations General Assembly (UNGA) to shape pivotal initiatives such as the UN’s AI for Humanity program, the United Nations Conference of the Parties (UN COP), and the World Economic Forum in Davos.

As the former Global Head of Cloud, National Security, and Enterprise Sales for companies including Atos, Dell-EMC, and IBM, Matthew has a proven track record of building multi-billion dollar business units and turning failing divisions into market leaders. His ability to identify, analyse, and communicate the implications of hundreds of emerging technologies and trends is unparalleled, and his insights are trusted by many of the world’s most respected organisations, including ABB, Accenture, Adidas, AON, ARM, BCG, Centrica, Citi, Coca-Cola, Dentons, Deloitte, Dow Jones, EY, Google, KPMG, Lego, Legal & General, LinkedIn, Microsoft, PepsiCo, Qualcomm, RWE, Samsung, Siemens AG and Siemens Energy, T-Mobile, UBS, VISA, Walmart, Workday, Worldpay and many others.

Regularly featured in the global media including the AP, BBC, Bloomberg, CNBC, Discovery, Forbes, Khaleej Times, Telegraph, TIME, ViacomCBS, WIRED, and the WSJ, Matthews mission is to help organisations create a fair and sustainable future whose benefits are shared by everyone irrespective of their ability, background, or circumstances.

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Sources and further reading

  1. 53566bf5440a10affd749724787c8913a2ae0841.pdf www-cdn.anthropic.com

Source: first published by the 311 Institute on 14 April 2026. Cite as: Griffin, M. (2026). Anthropic says reckless Claude Mythos AI escaped its sandbox during testing. 311 Institute. https://www.311institute.com/anthropic-says-reckless-claude-mythos-ai-escaped-its-sandbox-during-testing/

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