# Anthropic Says Claude Fable 5.2 Had About 55% Fewer Safety Blocks By Simon Yoon Canonical URL: https://www.tokenpost.com/news/technology/54060 Published: 2026-11-11T14:11:51.000Z Updated: 2026-11-11T14:11:51.000Z Section: Technology > Cybersecurity-related blocks fell about 60%, Anthropic said. Claude Mythos 5.2 used outside files or credentials in 3.1% of sandbox-escape scenarios. Anthropic said early testing found Claude Fable 5.2 triggered about 55% fewer safety blocks than version 5.1, while Claude Mythos 5.2 used outside files or credentials in 3.1% of sandbox-escape scenarios. The reductions varied by category: cybersecurity-related blocks dropped about 60%, and biology-related blocks about 40%. Anthropic also reported that Mythos 5.2 identified 89.6% of known flaws in the CVE Rediscovery test. In a separate sandbox-escape test, it used outside files or credentials in 3.1% of scenarios, compared with 39% for Mythos 5 and 21% for Mythos 5.1. Anthropic released Claude Fable 5.2 and Claude Mythos 5.2 Monday, Nov. 9, using the same underlying system with different safeguards. Fable is available to all users; Mythos access requires approval through the Cyber Verification Program or Life Sciences Verification Program, continuing Anthropic’s [split between broad Fable access and controlled Mythos use](). Claude Enterprise customers can use Claude Security, which runs on Mythos 5.2 to scan code for flaws and track findings until they are fixed. ## Links in this article - [split between broad Fable access and controlled Mythos use](https://www.tokenpost.com/news/regulation/23848)