Claude Fable is Anthropic's most capable publicly available AI model, built for long, complex, multi-step work rather than quick answers, and sits at the top of the Claude lineup just below Claude Mythos, a restricted-access model reserved for a small group of vetted security and research partners. It powers agentic AI tasks like autonomous coding, deep research, and browser automation, staying on task for hours with minimal supervision, planning a task, using tools, checking its own work, and reporting back once it's actually done. Because a model this capable could be misused in sensitive areas like cybersecurity and biology, certain flagged requests in these domains are automatically handled by a different, less capable Claude model instead, and users won't be charged Fable pricing when that happens. Claude Fable is available to Pro, Max, Team, and Enterprise users on Claude.ai, and to developers through the Claude Platform; free-plan users need to upgrade to access it. Users select Fable as their model in the Claude app's model picker, which applies whether working in a regular chat or in Claude Cowork, and can set an adjustable effort level controlling how much time and reasoning it applies to a task, which the app usually sets automatically based on the request.