OpenAI Bel

Claude Mythos 5.1 is Anthropic’s newest Mythos-class model, designed for advanced cybersecurity, biology, scientific research, coding, and long-running knowledge work. It is the same underlying model as Claude Fable 5.1 but uses different safeguards: Fable 5.1 is generally available, while Mythos 5.1 is restricted to trusted access programs with safeguards specifically designed for cybersecurity and life sciences research. The model sets a new performance frontier for agentic coding and demonstrates the strongest cyber capabilities of any Anthropic model released to date. In scientific research, Mythos 5.1 can work with specialized tools and complex workflows across molecular design, computational biology, and other technical domains. In Anthropic’s experiments, it designed high-affinity protein binders across multiple targets and achieved its strongest measured hit rate to date. It also optimized seven open-source protein and genomics deep learning models.

Claude Sonnet 5.5 is Anthropic’s mid-tier Claude 5.5 model designed for fast, well-scoped everyday work, coding, and professional document creation. Anthropic says it runs more than 30% faster than Claude Sonnet 5 and typically costs up to 30% less per task while keeping the same base token pricing. The model shows major gains in agentic coding, with a 70.6% score on Terminal-Bench 4.0 and stronger performance on FrontierCode and CursorBench than its predecessor. Sonnet 5.5 also performs strongly on knowledge work, computer use, chart understanding, and long-horizon tasks, in some cases approaching Claude Opus 5.5 at higher effort settings. Anthropic positions it as especially useful for debugging, routine coding, collaboration, and producing polished documents, slides, spreadsheets, and user interfaces. Claude Sonnet 5.5 is available across Anthropic’s platforms as well as AWS, Google Cloud, and Microsoft Azure.