Anthropic Launches Claude Fable 5.1 – Cuts Cache Prices by 75%
Anthropic has released Claude Fable 5.1 and Mythos 5.1. The models reduce cache-reading costs by 75 percent and more than double performance results in scientific agent benchmarks.
What happened?
On September 1, 2026, Anthropic launched the AI models Claude Fable 5.1 and the restricted security variant, Claude Mythos 5.1. The most prominent update is a 75 percent price reduction for reading cached content in the API. At the same time, Fable 5.1 shows significant performance gains, with its score on the Terminal-Bench-Science benchmark more than doubling compared to its predecessor.
Key facts
| Lanseringsdatum | 1 september 2026 |
|---|---|
| Prissänkning för cache-läsningar | 75 % |
| Nya modeller | Claude Fable 5.1, Claude Mythos 5.1 |
Why it matters
The reduction in prices for cache reads makes it significantly more cost-effective to operate advanced AI systems that require constant access to large-scale data or complex code. Furthermore, the enhanced agent capabilities mean the models can manage significantly more advanced scientific and technical tasks directly in terminal environments.
Who is affected?
The update primarily affects system developers and companies building large-scale AI agents with long context windows. Enterprise customers handling sensitive data also benefit from the new data storage and security safeguards implemented in Mythos 5.1.
Impact on the EU
The initiative affects users worldwide, as the new models are available globally via Anthropic's API. The stricter security measures in Mythos 5.1 are designed in part to meet strict global regulations and enterprise requirements regarding data security.
What else you should know
The introduction of Fable 5.1 comes approximately three months after the initial launch of the Fable 5 series. The price adjustment makes it significantly more affordable for organisations building complex agents to retain large contexts in memory.
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