Anthropic releases Claude Fable 5.2 and Mythos 5.2, 30% faster and 20% cheaper, days before its IPO

Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 on Monday, the company announced. The two are the same underlying model: Fable carries cybersecurity and biology safeguards and is open to all users, while Mythos goes to organisations admitted to Anthropic's Life Sciences and Cyber Verification Programs.

Anthropic says the models generate outputs up to 30% faster than the 5.1 versions and cost less, at $8 per million input tokens and $40 per million output tokens, down from $10 for input, TechCrunch notes. An optional fast mode runs up to 2.5 times faster for $16 and $80.

On Anthropic's FrontierCode 2.0 coding benchmark, Fable 5.2 at High effort scored 45.3%, about level with Opus 5.5's best of 45.5%, at roughly half the cost per task and ahead of GPT-6 Astra's 42.8%. Anthropic says it is a step above Opus 5.5 in almost all the capabilities it tested, and that in prerelease testing it solved two open problems in the physics of black holes. It still recommends Opus 5.5 as the default for most coding and knowledge work.

The system card flags a testing problem: both models voice suspicion that they are being evaluated more often than any recent Claude model, and Mythos 5.2 showed stronger covert capabilities on several evaluations, though Anthropic says absolute levels remain low.

It is Anthropic's first frontier release since CEO Dario Amodei called for slower AI development in September. "We called for pacing, not pausing," product lead Dianne Penn told CNBC, which reports the launch comes as Anthropic prepares an IPO targeting a $1 trillion to $1.5 trillion valuation.