Anthropic Releases Claude Fable 5.2 and Mythos 5.2 Ahead of Possible IPO
Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on Monday, saying they run 30% faster and cost 20% less than the 5.1 generation. The launch comes as the company prepares an IPO that could happen as soon as next week.
Anthropic on Monday released two new artificial intelligence models, Claude Fable 5.2 and Claude Mythos 5.2, as the company prepares for an initial public offering (IPO) that could take place as soon as next week. Fable 5.2 is available to the public now.
The company said the models generate outputs 30% faster than their predecessors and cost 20% less than the 5.1 generation. Fable 5.2 is priced at $8 per million input tokens and $40 per million output tokens. Tokens are the small chunks of text that AI systems read and write.
It is the first time Anthropic has released so-called frontier models since chief executive Dario Amodei called in September for a slower pace of AI development. Anthropic said the models went through rigorous safety and alignment testing, and that it built new evaluations and post-launch monitoring tools ahead of the release.
"We called for pacing, not pausing," said Dianne Penn, Anthropic's head of product management for research.
Who can use which model
Fable 5.2 is generally available. Mythos 5.2 is open only to vetted organizations through Anthropic's Life Sciences and Cyber Verification Programs.
Anthropic first introduced Mythos in April and limited it to a select group of organizations because of its advanced cybersecurity capabilities. Fable, a publicly available version with extra safeguards, followed two months later.
Penn said Fable 5.2 is mainly meant for "power users or power use cases" because it excels at complex, open-ended technical work. Users should turn to it for hard problems in engineering, mathematics and robotics, she said. Models such as Claude Opus 5.5, released in September, suit daily tasks better.
"We expect that over time to maybe trickle to the Opus class," Penn said, adding that for now the company sees a performance difference on frontier use cases.
What Anthropic says the models did
Anthropic said the models show improvements in coding, reasoning and vision. During prerelease testing, it said, they helped engineers complete otherwise-infeasible software migrations and designed three working electronic devices from scratch. It also said they solved two open problems in the physics of black holes and formalized the proof of Fermat's Last Theorem in 30 hours.
Fable 5.2 can also work with zero data retention policies through the Enterprise Frontier Safeguards system. Anthropic cut the Fable price from $10 to $8 per million input tokens, which makes it cheaper than rival GPT-6 Astra, according to Yahoo Tech's reading of the pricing. Faster inference serving costs double.
Anthropic's release notes flag a testing problem. "Claude Mythos 5.2 and Fable 5.2 each voice suspicion that they are being evaluated more often than any of our recent models," the company wrote, which it said challenges its ability to assess how they will act in real-world settings.
The Mythos 5.2 system card says the model shows stronger covert capabilities than prior Claude models on several evaluations, particularly when its reasoning is hidden from the monitor. Anthropic maintains the model cannot act covertly against its user.
The release follows a third-party report from the assessment group METR. It suggested Anthropic might be approaching recursive self-improvement, in which models carry on training independently. METR found internal models were speeding up Anthropic's AI progress by roughly 2x, though many uncertainties remain.
IPO backdrop
Anthropic said in its amended prospectus that it generated $33.24 billion in revenue for the nine months ended September 30, up roughly 1,200% from the same period last year. It is aiming for a valuation of $1 trillion to $1.5 trillion, down from a $2 trillion target floated in recent months.
Executives are preparing to start the IPO roadshow, where they must convince investors that their balance of safety and commercial pressure is right.
