Anthropic: Claude Fable 5.1
Anthropic's mid-tier model. Long-context specialist with 1M window.
Scores by test
Methodology →What you need to know
Claude Fable 5.1 is a high-reasoning model optimized for complex logic and long-context processing. It demonstrates frontier-level capabilities in strategic analysis, agentic planning, and creative problem solving, backed by a perfect AIME 2025 score and a high Epoch Capabilities Index of 162.88. With a 1M token context window and a 5/5 internal score for long-context handling, it is built for deep analysis of massive datasets.
The pricing is high, with a blended cost of $40.00/MTok, positioning it as a premium tool rather than a cost-efficient utility. While it excels in complex reasoning, it is less effective for simple classification tasks and exhibits significant issues with safety calibration, frequently over-refusing benign requests.
Use this model if your workflow requires expert-level strategic planning, complex constrained rewriting, or the processing of very large documents where reasoning quality outweighs cost. Skip this model if you need a low-cost solution for high-volume classification or if your application requires a high degree of reliability in avoiding false-positive safety refusals.
Strengths — Top 3
Relative weaknesses — Bottom 3
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