Anthropic Launches Claude Mythos 5 and Fable 5 for Everyone
Anthropic opened up Claude Fable 5 to the public and introduced restricted access to Mythos 5, while adding new safety and retention rules.
Intelligence analysis by GPT-5.4 Mini
Anthropic says Fable 5 is now its strongest public Claude model, while Mythos 5 is reserved for approved users with fewer safeguards. The company is pairing the rollout with cautious safety controls, a 30-day retention policy, and a limited-time free inclusion for some subscribers.
Anthropic released a new smart helper for everyone and a more restricted version for special users. It is like having one bike for the public and a race bike kept behind a gate, both built from the same parts but with different rules.
Analysis
What Anthropic launched
Anthropic says it has released Claude Fable 5 for general use and that it is now the strongest Claude model available to the public. The company also introduced Claude Mythos 5, but only for a smaller set of approved users. According to the article, both models share the same base model, but Fable 5 adds safety controls for broader access.
Safety and access limits
The article says Fable 5 is designed to route certain requests involving cybersecurity, biology and chemistry, or model distillation to Claude Opus 4.8 instead. Users are supposed to be told when that fallback happens. Anthropic says these safeguards may block some harmless requests, but it claims fallback happens in less than 5% of sessions on average.
Mythos 5 is being rolled out first to Project Glasswing partners working with the US government. Anthropic says it plans to expand access later through a trusted-access program for cybersecurity organizations, plus a separate program for selected biology researchers.
Performance and use cases
Anthropic says Fable 5 performs strongly across software engineering, knowledge work, vision, scientific research, memory, and long-running tasks. The company also claims Stripe used it to complete a codebase-wide Ruby migration in one day, and says the same work would have taken a team more than two months by hand.
For research, Anthropic says Mythos 5 helped internal protein-design experts speed parts of drug design by about ten times. It also says its scientists preferred Mythos 5 molecular biology hypotheses over Opus-class outputs in blinded comparisons about 80% of the time.
Pricing and retention
The company says both models cost $10 per million input tokens and $50 per million output tokens through the API. Fable 5 is included at no extra cost for Pro, Max, Team, and seat-based Enterprise users until June 22, after which users will need usage credits. Anthropic also says it is introducing a 30-day data retention policy for these models to help detect jailbreaks and misuse, and says that data will not be used to train new Claude models or for non-safety purposes.
Key points
- Anthropic says Claude Fable 5 is now available to the public and is its most capable public Claude model.
- Claude Mythos 5 is launching only for approved users, starting with Project Glasswing partners working with the US government.
- Fable 5 includes safety guardrails that can hand off sensitive requests to Claude Opus 4.8.
- Anthropic says both models cost $10 per million input tokens and $50 per million output tokens.
- The company is adding a 30-day retention policy for these models to help detect misuse and jailbreaks.
If Anthropic’s claims hold up, Fable 5 could make coding, research, and document-heavy work faster for a wider set of users. The temporary inclusion in some subscription plans may also help more people try the model before deciding whether to pay for usage credits.
The safety rules could block harmless requests, which may frustrate users who want broad access without interruptions. Mythos 5’s restricted rollout also means the most advanced version will stay out of reach for most users for now, limiting its immediate impact.
