Anthropic debuts preview of powerful new AI model Mythos in new cybersecurity initiative

Anthropic on Tuesday released a preview of its new frontier modelMythoswhich it says will be used by a small coterie of partner organizations for cybersecurity work. In a previously leaked memothe AI startup called the model one of its “most powerful” yet.

The model’s limited debut is part of a new security initiativedubbed Project Glasswingin which 12 partner organizations will deploy the model for the purposes of “defensive security work” and to secure critical softwareAnthropic said. While it was not specifically trained for cybersecurity workthe model will be used to scan both first-party and open source software systems for code vulnerabilitiesthe company said.

Anthropic claims thatover the past few weeksMythos identified “thousands of zero-day vulnerabilitiesmany of them critical.” Many of the vulnerabilities are one to two decades oldthe company added.

Mythos is a general-purpose model for Anthropic’s Claude AI systems that the company claims has strong agentic coding and reasoning skills. Anthropic’s frontier models are considered its most sophisticated and high-performance modelsdesigned for more complex tasksincluding agent-building and coding.

The partner organizations previewing Mythos as part of Project Glasswing include AmazonAppleBroadcomCiscoCrowdStrikethe Linux FoundationMicrosoftand Palo Alto Networks. As part of the initiativethese partners will ultimately share what they’ve learned from using the model so that the rest of the tech industry can benefit from it. The preview is not going to be made generally availableAnthropic saidthough 40 organizations will gain access to the Mythos preview aside from the partnership.

Anthropic also claims that it has engaged in “ongoing discussions” with federal officials about the use of Mythosalthough one would have to imagine that those discussions are complicated by the fact that Anthropic and the Trump administration are currently locked in a legal battle after the Pentagon labeled the AI lab a supply-chain risk over Anthropic’s refusal to allow autonomous targeting or surveillance of U.S. citizens.

News of Mythos was originally leaked in a data security incident reported last month by Fortune. A draft blog about the model (then called “Capybara”) was left in an unsecured cache of documents available on a publicly inspectable data lake. The leakwhich Anthropic subsequently attributed to “human error,” was originally spotted by security researchers. “‘Capybara’ is a new name for a new tier of model: larger and more intelligent than our Opus models — which wereuntil nowour most powerful,” the leaked document saidadding later that it was “by far the most powerful AI model we’ve ever developed,” according to the report. 

In the leakAnthropic claimed that its new model far exceeded performance areas (like “software codingacademic reasoningand cybersecurity”) met by its currently public models and that it could potentially pose a cybersecurity threat if weaponized by bad actors to find bugs and exploit them (rather than fix themwhich is how Mythos will be deployed).

Last monththe company accidentally exposed nearly 2,000 source code files and over half a million lines of code via a mistake it made in the launch of version 2.1.88 of its Claude Code software package. The company then accidentally caused thousands of code repositories on GitHub to be taken down as it attempted to clean up the mess.

Correction April 72026: An earlier version of this article erroneously stated how many partners are working with Anthropic on Project Glasswing. There are 12 partner organizationsthough 40 organizations total will have access to the Mythos preview.