Anthropic announces Claude Fable 5.1 and Mythos 5.1 models
Anthropic has released its new Claude Fable 5.1 and Mythos 5.1 models, which feature improved coding capabilities and reduced pricing for agentic workloads. The company has implemented enhanced security measures, including anti-distillation mechanisms and updated watermarking protocols to comply with the EU AI Act.
Why it matters
These releases highlight the ongoing industry tension between advancing AI capabilities for complex tasks and managing the significant safety risks associated with autonomous model behavior and potential misuse.
Anthropic announced the release of its new Claude Fable 5.1 and Claude Mythos 5.1 models on September 1, referring to them as “the world’s most advanced models for coding and knowledge work.”
The two models are the same except for their safeguards, according to the Claude-maker, with Fable 5.1 being generally available, while Mythos 5.1 is available only through the company’s trusted access programmes.
As for pricing, Anthropic stated that Fable 5.1 would cost an estimated 25% less than Fable 5 for “typical workloads” wherever the usage is billed by token. The company explained this was because it was reducing its pricing on models reading inputs that were already processed and stored.
For highly agentic work, the company said users could expect savings of up to approximately 45%.
Anthropic reported that Fable 5.1 could be used to discover software vulnerabilities, but not to develop exploits.
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