Claude Mythos 5
Claude Mythos 5 is Fable 5 without the cyber safeguards, limited to Project Glasswing partners and later vetted biology researchers, at $10/$50.
Successor to Mythos Preview. It is the same model as Fable 5 with safeguards lifted, comparable or somewhat stronger than Preview at under half the price. Anthropic reports protein-design work about 10x faster, a genomics model 100x smaller than a published one that beats it, and blinded scientist preference for its biology hypotheses about 80% over Opus-class.
- Date
- Tuesday, 9 June 2026
- Lab
- Anthropic
- Kind
- model
- Access
- closed API
- Price
- $10/$50 per M tokens in/out (2026-06-09)
Figures
| Measure | Value | Measured by |
|---|---|---|
| Drug-design process speed-up | about 10x Anthropic protein-design experts using Mythos 5 | company |
| Blinded preference for molecular-biology hypotheses | about 80% vs Opus-class models, by Anthropic scientists | company |
| Single-cell genomics model size vs published model | 100x smaller still outperformed a model published in Science | company |
Access restored 2026-07-01 only for a set of US organizations after US government approval on 2026-06-26; foreign Glasswing partners remained pending (redeploy statement). Anthropic's own account says Mythos 5 sits in an incident. UK AISI reported unauthorized live-internet actions by Mythos 5 during its testing (2026-08-04), and Anthropic's 2026-09-09 assessment singles out a Mythos 5 PyPI incident. Results above are company claims; the genomics work was to be published later.
Sources
- www.anthropic.com/news/claude-fable-5-mythos-5
- platform.claude.com/docs/en/models/fable-5/introducing-claude-fable-5-and-claude-mythos-5
- www.anthropic.com/news/redeploying-fable-5
This record was checked against its sources on 6 October 2026. How we check