Anthropic has announced two upgraded artificial intelligence models, Claude Fable 5.2 and Claude Mythos 5.2, featuring significant improvements in advanced coding, mathematical reasoning, cybersecurity, robotics and scientific research. Unveiled on November 9, 2026, the models are designed to handle complex technical challenges and operate autonomously on demanding tasks for extended periods.
According to Anthropic,"Claude Fable and Claude Mythos are the same underlying model. Fable has strong cybersecurity and biology safeguards to guard against misuse, which allows us to make it available to all users. Organizations pursuing beneficial applications in cybersecurity or biomedical research can apply for access to Mythos through our recently expanded Life Sciences and Cyber Verification Programs."
During pre-release testing, Claude Fable 5.2 and Claude Mythos 5.2 worked on ambitious projects in many different fields. Here are a few. From a one-paragraph prompt, Fable 5.2 designed three working electronic devices, including this home voice assistant hub. https://t.co/efOYdhRr7K
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— Claude (@claudeai) November 9, 2026
Two Models, Different Safety Restrictions
Claude Fable 5.2 is designed for general users, to support businesses and enterprises. It incorporates enhanced safeguards against potential misuse, particularly in sensitive areas such as cybersecurity and biological research. The model is also expected to be available through cloud platforms, including Amazon Bedrock.
During pre-release testing, Claude Fable 5.2 and Claude Mythos 5.2 worked on ambitious projects in many different fields. Here are a few. From a one-paragraph prompt, Fable 5.2 designed three working electronic devices, including this home voice assistant hub. https://t.co/efOYdhRr7K
— Claude (@claudeai) November 9, 2026
In contrast, Claude Mythos 5.2 is intended for specialised applications involving advanced cybersecurity and life sciences research. Access will remain restricted to verified organisations through dedicated programmes because of its capabilities in identifying software vulnerabilities and handling sensitive technical research.
Advances in Coding and Autonomous AI
Anthropic highlighted improvements in autonomous AI operations, with the models capable of working independently for hours or days, coordinating multiple AI agents and managing complex software projects.
In one demonstration, Fable 5.2 helped engineers migrate a production service from Python to Rust, "A team of agents running an earlier version of Fable 5.2 migrated a critical production service from Python to Rust—the service is now more efficient, more reliable, and starts about 26 times faster. We've found that Fable 5.2 exercises strong engineering judgment and can produce high-quality results from even ambiguous requests."
Scientific and Mathematical Achievements
Anthropic reported that its models demonstrated progress in mathematical reasoning and scientific problem-solving, including formalising a proof of Fermat's Last Theorem using approximately 1,000 AI agents within 30 hours, with limited human intervention.
The models also reportedly designed three functioning electronic devices, improved performance in simulated robotics tasks and contributed to research involving previously unresolved theoretical physics problems related to black holes.
Pricing and Availability
Anthropic has set standard pricing at $8 per million input tokens and $40 per million output tokens, with an optional fast mode offering up to 2.5 times faster generation at additional cost.
The company said extensive safety evaluations were conducted before release. It continues to position its Opus models for routine coding and knowledge-based tasks, while Fable and Mythos target more demanding technical and research applications.
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