Claude Mythos 5

MA

Matthew Berman24 Jul 2026

Anthropic model with no cyber guardrails. It is much stronger than Opus 5 at developing exploits (13 vs 4 exploitation success).

AI

AI Search28 Jun 2026

After the US government banned access to Claude Fable and Mythos, a letter eased the ban to allow Mythos 5 release to about 100 trusted partners including US companies and agencies. The creator argues this shows the importance of open-source models.

MA

Matthew Berman13 Jun 2026

Frontier model first revealed via Project Glasswing and withheld from general release for being too strong at cyber offense and defense. It was also covered by the export directive. The creator argues it is not much better than GPT-5.5 at finding vulnerabilities and calls the 'too dangerous' framing fear-based marketing.

MA

Matt Wolfe12 Jun 2026

Same underlying model as Fable 5 with safeguards lifted in some areas, available only to a small group of cyber defenders and infrastructure providers.

AI

AI Search11 Jun 2026

Earlier Anthropic model said to be too dangerous to release; Fable 5 beats it on benchmarks and is described as the same underlying model as Mythos 5 with extra safeguards.

MA

Matt Wolfe11 Jun 2026

Same underlying model as Fable 5 but with safety guardrails lifted in certain areas. It remains restricted to Project Glasswing partners, cybersecurity pros and government.

MA

Matthew Berman9 Jun 2026

Same model class as Fable 5 but without guardrails, offered to the security community for finding bugs and hardening software. Same pricing; Anthropic cited a ~10x speedup in aspects of protein design.