Claude Fable 5

Fable sits above Opus in Anthropic’s lineup: next-generation intelligence built for long-running agents and the most demanding reasoning work. It thinks on every turn, holds a million tokens of context, and stays coherent across sessions that run for many minutes at a stretch.

Fable 5 and Fable 5.1 are the most expensive models we run, at double Opus 5 on both input and output. Reach for it when the work rewards depth over speed and a wrong answer is costly. For most day-to-day brain work, Opus is the better trade.

Best for: long-horizon agentic work, the hardest reasoning, tasks where you’d rather pay more than iterate.