- Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 on September 1, with Fable 5.1 scoring 52.6% on Terminal-Bench-Science 0.1, more than doubling Fable 5’s 24.7% result.
- Cache read costs are reduced by 75%, cutting typical workloads by roughly 25% and highly agentic workloads by up to 45%, while base pricing remains unchanged at $10 per million input tokens and $50 per million output tokens.
- Fable 5.1 is excluded from Pro plans and standard Team seats, drawing from usage credits, while Max and premium Team or Enterprise seats include it for up to 50% of weekly limits.
Anthropic released Claude Fable 5.1 and Claude Mythos 5.1 on Tuesday, its first update to the Mythos-class model line since Fable 5 launched on June 9. The company claims the new models are the world’s “most advanced for coding and knowledge work.”
The release arrives three months into a cycle that included an export-control shutdown, a pricing dispute over subscription access, and the July launch of Claude Opus 5 at half the per-token price of Fable 5. Fable 5.1 scored 52.6% on Terminal-Bench-Science 0.1, more than double Fable 5’s 24.7% and ahead of Opus 5’s 29.0%.
On Terminal-Bench 4.0, which tests agentic coding through a command-line environment, Fable 5.1 scored 55.8% against Fable 5’s 42.0% and Opus 5’s 52.3%. Mythos 5.1, running with lighter Cybersecurity filters, scored 60.9% on the same test, with Anthropic noting the gap reflects tasks its safeguards intercepted and rerouted to Opus 4.8.
Cache reads now cost 75% less, cutting typical workload costs by roughly 25% and highly agentic workloads by up to 45%. Base pricing remains unchanged at $10 per million input tokens and $50 per million output tokens, compared to Opus 5’s $5 and $25.
Fable 5.1 is not included in Pro plans or standard Team seats, which run it on usage credits. Max and premium Team or Enterprise seats get it included for up to 50% of weekly limits.
The model is available now on the Claude API, Amazon Bedrock, Google Cloud, and Microsoft Foundry under the model ID “claude-fable-5-1.”
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