Anthropic Unveils Claude Fable 5: Revolutionary Mythos AI

Anthropic Launches Claude Fable 5, a Mythos-Class AI

Anthropic has recently made public its most advanced artificial intelligence model, Claude Fable 5, belonging to the new Mythos class. This launch marks a significant milestone for the company, which has implemented strict safety measures to limit potentially dangerous uses of this technology. Thus, in sensitive areas such as biology and cybersecurity, the system automatically reverts to a less advanced version, Claude Opus 4.8.

Exceptional Performance and Necessary Safeguards

The announcement on June 9, 2026, by Anthropic highlighted the impressive capabilities of Claude Fable 5. This model is described as the most powerful AI ever offered to the public, with particularly remarkable performance in complex and long-duration tasks. For instance, the AI successfully migrated a 50 million line Ruby codebase in just 24 hours, a task that would normally take several months for a team of engineers. Additionally, it demonstrated its ability to complete the game Pokémon FireRed simply by analyzing screenshots.

However, due to the power of this model, Anthropic deemed it necessary to implement safeguards. During preliminary testing, 95% of sessions were able to proceed without reverting, but the system is designed to switch to Claude Opus 4.8 if a risk is detected.

Claude Mythos 5: An Exclusive Version for Insiders

In parallel, Anthropic has also introduced Claude Mythos 5, a version of the model with relaxed security restrictions. This version is exclusively accessible to organizations participating in the Project Glasswing, a collaborative program with the U.S. government, allowing for more unrestricted use of the AI in certain areas.

A Mystery Surrounding the Number "5" and Doubling of Pricing

An intriguing aspect of this launch is the designation “5” for Claude Fable, as no prior version has been made public. Regarding pricing, the API for Claude Fable 5 is offered at $10 per million input tokens and $50 for output, which is double the cost of Claude Opus 4.8.

For individuals, Claude Fable 5 will be available at no additional cost in paid subscriptions from June 9 to June 22. After this period, access will be restricted, requiring a paid credit system, with reintegration planned later in the year.