Anthropic's Mythos Model Faces Capacity Constraints, Creating Opening for Competitors

Anthropic announced in April 2026 that Claude Mythos Preview would only be available to select companies due to security risks and high operating costs, not releasing it publicly. OpenAI's GPT-5.5 is already generally available as of May 2026, with the UK's AI Security Institute finding it comparable in capability at finding software vulnerabilities. Mozilla used Claude Mythos Preview to find 271 vulnerabilities in Firefox, which have been fixed.

Claude Mythos Preview release strategy

• ▪Anthropic does not appear to have the resources for a general release of Claude Mythos Preview.
• ▪The article about Anthropic's Claude Mythos Preview was published on May 10, 2026.
• ▪Anthropic announced in April 2026 that Claude Mythos Preview would only be available to a select group of companies to scan and fix their own software.
• ▪Anthropic stated Claude Mythos Preview would not be released to the general public due to its capability at finding security vulnerabilities in software.

AI vulnerability detection capabilities

• ▪The company Aisle reproduced Anthropic's published results for Claude Mythos Preview with smaller, cheaper models.
• ▪The 271 vulnerabilities found by Claude Mythos Preview in Firefox have been fixed.
• ▪OpenAI's GPT-5.5 is already generally available as of May 2026.
• ▪Mozilla used Claude Mythos Preview to find 271 vulnerabilities in Firefox.
• ▪The UK's AI Security Institute found that OpenAI's GPT-5.5 is comparable in capability to Claude Mythos Preview at finding software vulnerabilities.

Cybersecurity offense-defense dynamics

• ▪Modern generative AI systems including OpenAI's and open-source models are getting good at finding and exploiting vulnerabilities in software.
• ▪Bruce Schneier is a security technologist who teaches at the Harvard Kennedy School at Harvard University.

Tax code loophole discovery

• ▪The Double Dutch Irish Sandwich is a tax loophole that involves multiple different tax jurisdictions.
• ▪AI models' searching, pattern-matching and reasoning capabilities that make them good at analyzing software apply to the tax code.
• ▪The carried interest loophole is a US tax dodge that has been exploited for decades.
• ▪Various US administrations have tried to close the carried interest loophole but legislators have not resisted lobbyists long enough to patch it.

Regulatory system vulnerabilities

• ▪AI models could be tasked with finding loopholes in environmental rules or food and safety rules.
• ▪It generally takes years for a country to amend its tax code.
• ▪The process of amending tax code is political with lobbyists pressuring legislators not to patch loopholes.
• ▪Tax loopholes result in less revenue collected by governments.

Societal adaptation challenges

• ▪The AI revolution will give humans the ability to perform cognitive tasks outside of their bodies at scale.

Perspective of Competitors and alternative AI providers

• ▪The company Aisle reproduced Anthropic's published results for Claude Mythos Preview with smaller, cheaper models.
• ▪The UK's AI Security Institute found that OpenAI's GPT-5.5 is comparable in capability to Claude Mythos Preview at finding software vulnerabilities.

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