Anthropic's frontier model targeting hard technical tasks and agent-scale collaboration.
Anthropic launched Claude Fable 5.2 and Claude Mythos 5.2, targeting the hardest technical challenges with gains in coding, reasoning and vision. Fable 5.2 scored 41.3% on the Remote Labor Index, roughly double Opus 5.5 and GPT-6 Astra, and 1,000 Fable 5.2 agents formalized Fermat's Last Theorem in 30 hours versus 11 days for Anthropic's first formalization. Mythos 5.2 also cut sandbox-escape rates to 3.1% from 39% in Mythos 5.
Prominent AI observer Ethan Mollick tested Anthropic's new Claude Fable 5.2 ahead of public launch and found it highly impressive, building on the already strong Opus 5.5. He frames AGI as matching most human experts on most computer-based intellectual tasks and asks whether this model and imminent OpenAI and Google rivals now cross that limited threshold.
Anthropic has upgraded Claude Fable and Claude Mythos to version 5.2, with gains in coding, reasoning and vision. Both share the same underlying model: Fable ships with cybersecurity and biology safeguards for general availability, while Mythos is gated behind verification programs for security and life-sciences organizations. In prerelease testing the models completed otherwise-infeasible software migrations, designed three working electronic devices from scratch, solved two open problems in black hole physics, and formalized Fermat's Last Theorem in 30 hours.