Anthropic Launches Claude Fable 5, Its First Public Mythos-Class AI Model

Anthropic has officially launched Claude Fable 5, the company's first publicly available Mythos-class AI model, giving customers access to a system that delivers significantly stronger performance than any Claude model released before.



The launch follows Anthropic's introduction of the more powerful Claude Mythos model earlier this year, which remained restricted to selected partners and cybersecurity organizations because of its advanced capabilities.



According to Anthropic, Claude Fable 5 achieves state-of-the-art results across a wide range of benchmarks, including software engineering, scientific research, vision tasks, knowledge work, and long-running complex projects. The company says the model performs especially well on tasks that require sustained reasoning and extended context handling.



What Makes Claude Fable 5 Different?



Anthropic says Fable 5 can work autonomously for longer periods than previous Claude models, helping users tackle larger and more complicated workflows without frequent intervention.



Key highlights include:




Advanced software engineering performance that helps developers handle complex coding tasks.



Improved long-context understanding for processing large amounts of information.



Stronger reasoning capabilities across research, analysis, and knowledge work.



Enhanced memory and task persistence for longer projects and workflows.




Built-In Safety Measures



Because of its advanced capabilities, Anthropic has implemented additional safeguards for Claude Fable 5. The company says certain sensitive requests, particularly those involving cybersecurity topics, may automatically route to the less capable Claude Opus 4.8 model.



Anthropic notes that these protections trigger in fewer than 5% of sessions on average, although some harmless requests can occasionally be affected while the company continues refining its safety systems.



Claude Mythos 5 Remains Restricted



Alongside Fable 5, Anthropic also introduced Claude Mythos 5, a version with fewer safeguards that remains available only to a small group of cyberdefenders and infrastructure providers with special access permissions.



Both new models cost $10 per million input tokens and $50 per million output tokens, which is less than half the price of the earlier Claude Mythos Preview offering.



Claude Fable 5 is available starting today on Pro, Max, Team, and seat-based Enterprise plans at no additional cost through June 22. Beginning June 23, users will need usage credits to continue accessing the model, although Anthropic says it plans to restore broader subscription access once capacity allows.




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