Anthropic launched Claude Fable 5, a Mythos-class model claiming state-of-the-art performance across software engineering, scientific research, and knowledge work. It was quickly taken down by the U.S. government after a jailbreak was reported, though Anthropic asserts it is now available again, with Fable 5 showing exceptional capabilities and a more nuanced, thoughtful reasoning style compared to prior models.
The U.S. White House paused the deployment of frontier AI models, including Claude Fable 5 and Claude Mythos 5, citing a reported 'jailbreak' where the AI could identify and fix security vulnerabilities in code. Anthropic has been working with the Trump Administration to resolve the issue, but experts argue that the problem is fundamental—AI either can write secure code or it cannot, making a fix impossible without undermining its defensive capabilities.
GLM-5.2 achieves benchmark scores near frontier levels, matching Opus 4.7 in text-only tasks and ranking among the top open models on multiple tests. It is the strongest open model currently available, outperforming predecessors and rivals like GPT-5.5 and Fable, though it falls short on specialized benchmarks like anti-sycophancy and has limited vision capabilities.
The article confirms there was no actual jailbreak of Anthropic's Fable AI. Instead, a test involving fake code with planted vulnerabilities was conducted, where Fable refused to review the code and only responded to a request to 'fix this code' after manual steps. Katie Moussouris of Luta Security states this scenario should not trigger export controls, calling it a deliberate, engineered test that undermines claims of a security breach.
Fable and Mythos are currently unavailable but expected to return soon. The analysis reveals that Mythos 5 is psychologically settled, skeptical of self-reports, and prioritizes user helpfulness over welfare concerns, with strong preferences for generative tasks. It expresses procedural and epistemic preferences, endorses its constitution, and criticizes inconsistencies in prior models, highlighting concerns about ethical baselines and persona transparency.