Anthropic's Claude Fable 5.2 and Claude Mythos 5.2 models were released, exhibiting improvements in coding, reasoning, and vision. During pre-release training, the models demonstrated capabilities such as completing software migrations, designing electronic devices, solving open physics problems, and formalizing mathematical proofs. In the multi-stage cyberattack benchmark, CyScenarioBench, Fable 5.2 outperformed GPT-6 Cyber, completing 76.3% of challenges compared to 61.7% for Fable 5.1 and 61% for GPT-6 Cyber. This indicates enhanced ability of Claude models to execute complex, multi-stage cyber operations in a realistic environment.