laude Fable 5, developed by, is the company's most capable generally available AI model and the first public release in its new Mythos-class tier. Designed for the most demanding coding, research, and enterprise knowledge-work applications, Fable 5 significantly advances long-horizon reasoning, autonomous execution, and agentic workflows beyond the Opus family. Anthropic positions it as a model capable of sustaining complex projects over days rather than hours, with stronger planning, self-validation, and multi-stage problem solving. Leveraging adaptive reasoning and advanced effort-control mechanisms, Claude Fable 5 excels at large-scale code migrations, complex software engineering projects, multi-agent orchestration, and prolonged autonomous workflows involving numerous concurrent subagents. Anthropic highlights its ability to plan across stages, delegate work to specialized agents, write and execute tests for its own code, and continuously verify outputs against project objectives. Its capabilities are further enhanced by a native 1-million-token context window and support for outputs up to 128,000 tokens, enabling analysis of massive repositories, extensive document collections, and long-running research workflows within a single context. The model also features advanced multimodal and computer-use capabilities, allowing it to interpret diagrams, charts, PDFs, and visual interfaces while using vision to evaluate and refine its own work.