Claude Fable 5.1

Fable 5.1 is the newest model in Fable, the line Anthropic places above Opus. It costs the same as Fable 5, double Opus 5 on both input and output, and it holds a million tokens of context.

It thinks before every answer and decides for itself how long. Reach for it when the work rewards depth over speed and a wrong answer is costly. For most day-to-day work, Opus is the better trade.

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