How much does Fable 5.1 cost per token?

Input is $10 per million tokens, output is $50 per million, and cache write is $12.5 per million. Cache reads are $0.25 per million tokens.

Are Fable and Mythos 5.1 different models?

Some community analysis suggests they may use the same weights, differing only in safety and routing behavior, but Anthropic has not confirmed this.

Large Language ModelsAI Business & IndustryLatent SpaceSep 2, 2026Sep 2, 2026, 19:01 JST

Claude Fable 5.1 Launch, Cache Costs Cut 75%

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3 Key Points

What happened
Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 as its new flagship models. It positions them as the world's most advanced for coding and knowledge work.
Why it matters
The cache read price dropped 75% to $0.25 per million tokens. This helps long sessions. However, output token use rose 1.7x, so the net per-task cost increased 20%.
What to watch
Fable 5.1 scores 66 on the Artificial Analysis Intelligence Index, ahead of rivals. It has a 1 million token context window and accepts text plus image inputs.

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Context & Analysis

The launch comes as other models like Grok 4.7 and Gemini Flash 3.8 approach, but Fable 5.1's reception highlights a split between raw capability and practical use. Benchmarks show large gains, such as doubling Terminal-Bench-Science scores, but users report rate limits and ergonomic issues. The price cut on cache reads signals a focus on long-running agentic tasks, yet the higher output token usage tempers the benefit. Artificial Analysis notes Fable 5.1 may tie with Opus 5 on some agentic knowledge work, so the win is not absolute. Community questions about whether Fable and Mythos are distinct models add uncertainty to benchmark interpretation.

FAQ

How much does Fable 5.1 cost per token?: Input is $10 per million tokens, output is $50 per million, and cache write is $12.5 per million. Cache reads are $0.25 per million tokens.
Are Fable and Mythos 5.1 different models?: Some community analysis suggests they may use the same weights, differing only in safety and routing behavior, but Anthropic has not confirmed this.

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