Anthropic launches Claude Fable 5.2, Mythos 5.2 before IPO

Anthropic released two new frontier AI models, Claude Fable 5.2 and Claude Mythos 5.2, on Monday, November 9. The company says they are faster and cheaper than the versions that came before them, and the launch comes as it prepares for an initial public offering that could happen as soon as next week. These are the first frontier models Anthropic has shipped since CEO Dario Amodei called for slowing the pace of AI development in September. "We called for pacing, not pausing," Dianne Penn, Anthropic's head of product management for research, told CNBC.cnbc.com

Faster outputs, lower prices

Anthropic says the new models produce outputs up to 30% faster than Fable 5.1 and Mythos 5.1, and that they are better at coding, reasoning and vision, according to 9to5Mac. Fable 5.2 costs $8 per million input tokens and $40 per million output tokens, according to Anthropic's developer documentation. Fable 5.1 cost $10 and $50, so the new price is 20% lower, Yahoo Finance reported. Both models have a 1 million-token context window, 128,000 maximum output tokens and a knowledge cutoff of June 2026, the documentation shows.finance.yahoo.com+2

Bloomberg reported that Fable 5.2 can take on harder software engineering work and hardware tasks such as controlling robots. It can also run long projects and coordinate more than 1,000 AI agents at once, according to Bloomberg. Penn said Fable 5.2 is meant for "power users or power use cases." She said Claude Opus 5.5, released in September, is a better fit for everyday tasks.bloomberg.com+1

Mythos stays restricted

Fable 5.2 is available to all customers. It can be used through the Claude API, on Claude Platform on AWS and through Google Cloud. Mythos 5.2 uses the same underlying model as Fable 5.2 but has fewer safeguards for cybersecurity and life sciences work, Bloomberg reported. Only vetted organizations in Anthropic's Life Sciences and Cyber Verification programs can use it. Anthropic first introduced Mythos in April and limited who could use it because of its advanced cybersecurity capabilities. Two months later it released Fable, a public version with extra safeguards. The 5.1 versions came out in September, The Verge noted.platform.claude.com+3

Safety and the IPO

Anthropic said the models went through rigorous safety and alignment testing, and that it built new evaluations and post-launch monitoring tools before the release. The company is targeting a valuation of $1 trillion to $1.5 trillion in its offering, down from a $2 trillion figure discussed in recent months. Its amended prospectus reports revenue of $33.24 billion for the nine months ended September 30, roughly 1,200% higher than the same period a year earlier, CNBC reported. Penn said the new models handle work that is "completely novel," and that their capabilities may eventually "trickle to the Opus class".cnbc.com