Claude Fable 5.2 and Mythos 5.2 cement Anthropic's AI lead just before its IPO

Anthropic released Claude Fable 5.2 and Mythos 5.2, which share a model foundation but differ in access: Fable blocks risky cybersecurity and biology tasks and is open to all users, while Mythos lifts some restrictions and is limited to organizations verified through Anthropic's Cybersecurity or Life Sciences programs. Artificial Analysis's Index v5 places Fable 5.2 first at 65 points, five ahead of Gemini 4 Carbon and 15 ahead of Fable 5.1, though per-task costs at the highest tier average $26.50. Anthropic says about 1,000 Fable 5.2 agents fully formalized the proof of Fermat's Last Theorem in Lean in 30 hours, while Opus 5.5 reached only 26 percent in 18 hours in the same setup.