Anthropic released two new models on Monday, Nov. 9: Claude Fable 5.2 and Claude Mythos 5.2. The company calls them its most capable models for hard technical work such as coding, science, and finance.
Two names, one model
Fable and Mythos are the same underlying model. Fable carries safeguards against misuse in cybersecurity and biology, which lets Anthropic offer it to all users. Mythos does not have some of those limits, so it goes only to organizations approved through Anthropic’s Cyber Verification Program and Life Sciences Verification Program.
Faster and cheaper
Anthropic says the new models generate output up to 30% faster than the 5.1 versions. Fable 5.2 costs $8 per million input tokens and $40 per million output tokens, down from $10 and $50 for Fable 5.1. That is a 20% cut. An optional fast mode runs up to 2.5 times quicker and costs $16 and $80.
What Anthropic reports
Every figure in this list comes from Anthropic’s own testing, not from independent evaluators.
- Robotics: On RoboDojo, a simulated two-arm control test, Fable 5.2 scored 64.9% at maximum effort. Anthropic lists 29.8% for GPT-6 Astra and 27.6% for Fable 5.1.
- Cybersecurity: On an internal test called CVE Rediscovery, Mythos 5.2 found 10.2% more vulnerabilities than Claude Opus 5.5.
- Mathematics: A team of 1,000 Fable 5.2 agents formalized a proof of Fermat’s Last Theorem in 30 hours. Anthropic’s first attempt, with an unreleased model, took 11 days.
- Software: Anthropic says Claude now writes over 90% of the changes merged into its core codebase, with human guidance.
How to read the launch
Anthropic still suggests Claude Opus 5.5 as the starting point for most coding and knowledge work. It recommends moving up to Fable or Mythos for the most open-ended technical tasks. CNBC reported that the launch comes as the company prepares for a possible public offering.
Disclosure: Ad Astra’s drafts are written with the help of Claude, which Anthropic makes. We link Anthropic’s own pages above and mark which figures are company-reported.
