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

Claude Fable 5.1, developed by Anthropic and released on September 1, 2026, is an AI model featuring Adaptive Reasoning, Max Effort, and Default Fallback configurations. In standardized evaluations, the model achieved an intelligence index of 65.7 and a coding index of 81.6. Benchmark performance results include a GPQA score of 0.937, an HLE score of 0.591, a SciCode score of 0.62, and an LCR score of 0.8. Regarding operational performance, the model maintains an output speed of 67.585 tokens per second with a time to first token of 244.369 seconds. Pricing for the model 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.