Anthropic unveiled Claude Fable 5.2 and Claude Mythos 5.2, new versions of its most powerful AI models with enhanced programming, reasoning and image processing capabilities. By data developer, the new products perform tasks up to 30% faster than their predecessors, and in most tests performed they outperform Claude Opus 5.5.
Image source: Anthropic (screenshots)
Fable 5.2 and Mythos 5.2 are built on the same basic model, but differ in defense mechanisms. The first is available to a wide range of users and has enhanced restrictions for tasks in the field of cybersecurity and biology. Mythos 5.2 is intended for verified organizations engaged in research in these areas.
Specifically, in the CVE Rediscovery test, the new Mythos detected 10.2% more vulnerabilities than Opus 5.5 and 14.4% more than Mythos 5.1. At the same time, Anthropic separately notes that the results of its own assessment of the search for vulnerabilities were approximately comparable to Opus 5.5.
In programming, Fable 5.2 demonstrated the ability to independently create large-scale projects. In one experiment, the model, with the help of more than a thousand agents, created a working operating system with drivers, file storage, an interface, and an installer in eight days.
In another case, a thousand agents formalized a proof of Fermat’s last theorem in Lean in just 30 hours. In addition, the model independently designed three electronic devices: a home voice assistant, a USB speakerphone and a portable virtual pet.
Significant progress has also been noted in other scientific areas. Fable 5.2 solved two open problems in theoretical physics related to black holes and quantum gravity, and also showed improved results in controlling robots. Mythos 5.2 developed a method for predicting the structure of the protein coats of adeno-associated viruses used in gene therapy delivery and correctly modeled 28 structures out of 34 attempts.
Anthropic also reports a reduction in the number of unwarranted defense triggers by approximately 55% compared to the previous version. Claude Fable 5.2 is available now on major platforms including Amazon Web Services, Google Cloud and Microsoft Azure. The cost is $8 per million input and $40 per million output tokens. Accelerated Fast Mode will cost twice as much. Mythos 5.2 is only available to organizations that have been specifically vetted by Anthropic.
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