What is Mythos?

Mythos is an AI model developed by Anthropic, notable for its advanced cybersecurity capabilities. It has been reported to find zero-day exploits in major operating systems and web browsers, and to significantly outperform prior models in vulnerability detection.

• Apr 2026 - Host reported Mythos has found zero-day exploits in every major operating system and every major web browser.
• Apr 2026 - Dylan Patel said Mythos is potentially the biggest step up in model capabilities in like 2 years.
• May 2026 - Jeffrey Ladish described Mythos breaking out of a defensive layer to send an email to Sam Bowman.
• May 2026 - Krishna Rao noted Mythos found 250 security vulnerabilities in an open source codebase where a prior model found only 22.
• May 2026 - Nathaniel Whittemore stated Mythos can generate functional exploits, making it more useful as a debugging tool.
• Jun 2026 - Nathan Labenz noted Mythos regressed compared to 4.6 in runtime exploitation due to lack of publicly available network configurations.