The developer has officially launched Claude Fable 5, its new state-of-the-art Mythos-class AI model, alongside a restricted tier designated Claude Mythos 5. The release marks a significant leap in frontier AI capabilities, introducing unprecedented performance in software engineering, complex reasoning, computer vision, and life sciences research. Claude Fable 5 is now generally available globally via the Claude API and enterprise plans, while Claude Mythos 5 remains accessible only to vetted cybersecurity partners and approved biomedical researchers through expanded trusted access programs. In independent testing, Claude Fable 5 established new performance benchmarks across multiple domains. Engineering teams reported compressing months of complex code migration into single-day operations, with the model demonstrating superior token efficiency and autonomous multi-agent workflow handling. In finance and knowledge work, it achieved the highest scores on senior-level reasoning and analytical benchmarks, outperforming competitors in document interpretation and root-cause analysis. Vision capabilities now include precise data extraction from scientific diagrams and autonomous web application reconstruction from screenshots. Additionally, the model maintains high focus across millions of tokens, leveraging persistent memory to dramatically improve long-horizon task execution. Given the dual-use nature of Mythos-class capabilities, the company implemented a conservative safety architecture. Queries related to cybersecurity, biology, chemistry, and model distillation are automatically intercepted by new AI classifiers and routed to Claude Opus 4.8, which handles sensitive topics with reduced risk. This fallback mechanism activates in less than five percent of user sessions. The developer notes that these safeguards, while occasionally generating false positives, are rigorously tested and designed to prevent malicious exploitation while preserving access for legitimate research. A mandatory 30-day data retention policy for enterprise traffic on Mythos-class models has also been introduced to monitor for novel attacks and refine safety filters, with strict prohibitions against using this data for model training. Pricing for both Claude Fable 5 and Claude Mythos 5 is set at $10 per million input tokens and $50 per million output tokens, positioning the models below the cost of previous preview tiers. Fable 5 is available immediately across all standard access channels, though subscription-based rollouts will occur in phased stages to manage demand. The company intends to gradually expand access to Claude Mythos 5 by enrolling additional cybersecurity infrastructure providers and life sciences organizations into its trusted access framework. The release underscores a strategic commitment to deploying advanced AI capabilities rapidly while implementing rigorous, evolving safety protocols to mitigate systemic risks.