Anthropic Launches New Claude Fable and Mythos 5.2 Models

Anthropic has released Claude Mythos 5.2 and Fable 5.2 with "improvements in areas like coding, reasoning, and vision," while cutting Fable's input price and claiming 30% faster responses. TechCrunch reports: It's Anthropic's first model release since the arrival of a third-party report from the assessment group METR, which suggested the lab might be approaching recursive self-improvement (RSI) -- or the ability for AI models to carry on model training independently. The METR report found internal models were speeding up Anthropic's AI progress by roughly 2x, although many uncertainties remain. Still, Anthropic's release notes significant ongoing challenges in accurately testing model capabilities. "Claude Mythos 5.2 and Fable 5.2 each voice suspicion that they are being evaluated more often than any of our recent models, which challenges our ability to assess how they will act in real-world settings. As these settings expand and capabilities increase with future models, we expect this challenge to grow."

Anthropic maintains that the new version of Mythos does not have the ability to act covertly against its user, a verdict that's detailed further in Mythos 5.2's system card. "Claude Mythos 5.2 shows stronger covert capabilities than prior Claude models on several of our evaluations, particularly when its reasoning is hidden from the monitor," the system card reads. "That said, we believe that low levels of absolute performance on our new covert evaluations support claims that rely on detection of harmful actions in high-stakes situations." Fable 5.2 has been available to select parties in pre-release for some time, and Anthropic says the model has already "solved two open problems in theoretical physics, formalized Fermat's Last Theorem, and supported numerous other research projects."