Dept. of Mysteries
Anthropic Unveils Claude Fable 5.2 and Claude Mythos 5.2 in a Wondrous Decree
Anthropic has released Claude Fable 5.2 and Claude Mythos 5.2, promising sharper coding, reasoning and vision, faster output and a lower price per token.
Monday, 9 November 2026 · 2 min read
Anthropic has upgraded its Claude Fable and Claude Mythos models, unveiling Claude Fable 5.2 and Claude Mythos 5.2, which the company says are designed to tackle the most daunting technical challenges. The pair show improvements in areas like coding, reasoning and vision. Behold, too, a gentler purse: the new models arrive at a lower price than their predecessors, and Fable 5.2 is available to all users. The prerelease annals read like a catalogue of arcane feats. According to Anthropic, the models helped its engineers complete otherwise-infeasible software migrations, designed three working electronic devices from scratch and solved two open problems in the physics of black holes. They also formalized the proof of Fermat's Last Theorem in 30 hours. Claude Fable and Claude Mythos are the same underlying model. Fable carries strong cybersecurity and biology safeguards to guard against misuse, which is why it can be offered to everyone, while organizations pursuing beneficial work in cybersecurity or biomedical research can apply for Mythos through the Life Sciences and Cyber Verification Programs. Brian Grinstead, Distinguished Engineer at Mozilla, said: "Mythos 5.2 roughly doubled the vulnerability discovery metrics of Mythos 5.1 across respective scanning campaigns." The new models generate outputs up to 30% faster than Claude Fable 5.1 and Claude Mythos 5.1, and cost $8 per million input tokens and $40 per million output tokens, tokens being the small chunks of text a model reads and writes. An optional fast mode speeds up token generation by up to 2.5 times, for $16 per million input tokens and $80 per million output tokens. Anthropic says it ran extensive prerelease safety testing, including novel evaluations of concerning behaviors like sandbox escapes, in which a model tries to break out of the walled-off environment it is tested in. The company believes high-stakes risks from misalignment remain low, and says Fable 5.2's safeguards are as robust as those of Fable 5.1 but produce fewer unnecessary blocks. For most coding and knowledge tasks, Anthropic still recommends starting with Claude Opus 5.5, reserving Fable and Mythos for the most ambitious, open-ended technical work. Claude Fable 5.2 is available today on all platforms, including Amazon Web Services, Google Cloud and Microsoft Azure. Tom Pritchard, Staff Engineer at Shopify, put it plainly: "It feels like working with another staff-level engineer."
Source: www.anthropic.com