What is Claude Mythos 5?

Claude Mythos 5 is Anthropic's most capable model, launched June 9, 2026. It is the successor to Claude Mythos Preview and is currently deployed through Project Glasswing for cyberdefenders and critical infrastructure providers. It carries the strongest cybersecurity capabilities of any model in the world.

What is the difference between Claude Mythos 5 and Claude Fable 5?

They are the same underlying model. Claude Fable 5 has safety classifiers active that route certain cybersecurity, biology, and distillation queries to Claude Opus 4.8. Claude Mythos 5 has those cyber safeguards lifted for Glasswing partners. Fable 5 is generally available; Mythos 5 is restricted to Glasswing.

Can I use Claude Mythos 5 through the API or Claude.ai?

Not yet. Mythos 5 is restricted to Project Glasswing partners. Fable 5, the general-access version with safeguards enabled, is available on the Claude API (claude-fable-5) and on Claude.ai subscription plans.

What is Project Glasswing?

Project Glasswing is Anthropic's cybersecurity initiative that gives select partners access to Mythos-class models for defensive security work. It was launched in April 2026 with Mythos Preview and has expanded to Mythos 5 in collaboration with the US government. A broader trusted access program is coming soon.

How does Claude Mythos 5 compare to GPT-5.5 and Gemini 3.1 Pro?

Mythos 5 and Fable 5 are state-of-the-art on nearly all tested benchmarks, showing exceptional performance in software engineering, knowledge work, vision, scientific research, and cybersecurity. See the benchmark table above for a full comparison.

What is the pricing for Claude Mythos 5?

Mythos 5 is priced at $10 per million input tokens and $50 per million output tokens — less than half the price of Claude Mythos Preview.

What vulnerabilities has Claude Mythos actually found?

Anthropic reports thousands of zero-day vulnerabilities across every major operating system and web browser. Disclosed examples include a 27-year-old OpenBSD remote crash vulnerability, a 16-year-old FFmpeg bug missed by five million automated tests, Linux kernel privilege escalation chains, and a Firefox browser exploit chaining four vulnerabilities to escape both renderer and OS sandboxes.

Will Claude Mythos 5 ever be publicly available?

Anthropic has stated it plans to expand access through a broader trusted access program, but no public timeline has been given. The program will initially cover cybersecurity organizations and, separately, life sciences researchers.