In June, Anthropic first released Fable 5, its Mythos-class AI model for Claude. Three months later, Anthropic is updating Claude with the new Fable 5.1 model upgrade.
Claude Fable 5.1 and Mythos 5.1 arrived today
In the world of Anthropic, Fable is Claude’s most capable model. Haiku, Sonnet, and Opus are small, medium, and large forms below Fable.
“Claude Fable 5.1 sets new standards for coding, knowledge work, and long-term problem solving,” said Anthropic. The company says that the new model has a higher level of performance compared to the Fable 5.
Anthropic also says that Fable 5.1 “achieves results similar to or better than Fable 5 at a much lower cost” when set to low or medium effort.
More from Anthropic below:
Fable 5.1 avoids shortcuts that result in poor quality work, and it’s smart enough to fix the root causes of software problems. For example, in the testing of the Millennium Investment Company, Fable 5.1 found the cause of a rare crash in their internal system that their engineers (or other models) could not explain after years of effort.
In addition to Fable 5.1, Anthropic also released Mythos 5.1 for users with access to Mythos.
“Claude Fable 5.1 and Claude Mythos 5.1 are the same model, but with different levels of protection,” Anthropic explained. “Fable 5.1 is generally available, while Mythos 5.1 is available only through our Trusted Access program; its protections are specifically designed to support cybersecurity and life science work.”
Here is the price information of Fable 5.1:
Fable 5.1 will cost about 25% less than Fable 5 for normal work, wherever it is billed by token. This is because we are discounting our cache reads (where the model reads inputs that have already been processed and stored). For work with high representation, savings are often very large – up to about 45%.
In terms of price, Anthropic said it has reduced the price of Fable 5.1’s read cache (where the model is reused in the context it has been processed) wherever usage is billed by token, such as our API. The company said this “leads to a significant reduction in the overall cost of operating the model.” Otherwise, the price is unchanged from Fable 5.
You can learn more in the announcement post here.
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