Claude Fable 5.1

Anthropic•Documentation

claude-fable-5-1

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Anthropic's most capable publicly available model, built for ambitious long-running agentic work in software engineering, scientific research, and complex knowledge work. Improves on Fable 5 in coding and root-cause debugging, and cuts cache read pricing by 75% to $0.25 per million tokens. Features mandatory adaptive thinking, 1M token context window, 128K output capacity, and all effort levels including xhigh and max. Priced at $10/$50 per million tokens. Knowledge cutoff June 2026.