Claude Fable 5.1 (Adaptive Reasoning, Medium Effort, Default Fallback)

Claude Fable 5.1 is an artificial intelligence model developed by Anthropic and released on September 1, 2026. Designed for adaptive reasoning with medium effort and a default fallback configuration, the model achieves an intelligence index of 60.5 and a coding index of 77.1. Performance metrics indicate an output speed of 46.581 tokens per second with a time to first token of 4.523 seconds. Benchmark results for the model include 0.886 on GPQA, 0.538 on HLE, 0.553 on SciCode, and 0.786666666666667 on LCR. Pricing for Claude Fable 5.1 is set at $10.00 per million input tokens and $50.00 per million output tokens, resulting in a blended rate of $20.00 per million tokens.