Anthropic, the company behind Claude, has released Claude Mythos Preview, its most capable frontier model to date, with dramatic improvements in reasoning, coding, and cybersecurity. In an unusual move, the company has chosen not to make the model generally available, instead restricting access to a consortium of technology companies through a new initiative called Project Glasswing. Claude Mythos Preview represents what Anthropic describes as a "step change" over its predecessor, Claude Opus 4.6. During internal testing, the model autonomously discovered and exploited zero-day vulnerabilities in every major operating system and web browser. The oldest it found was a now-patched 27-year-old bug in OpenBSD, a system known primarily for its security. It also found a 16-year-old vulnerability in FFmpeg's H.264 codec. Internal benchmarks showed dramatic gains. Where Opus 4.6 developed working JavaScript shell exploits only twice out of several hundred attempts on Firefox vulnerabilities, Mythos Preview succeeded 181 times. On the OSS-Fuzz corpus, it achieved full control flow hijack on ten separate, fully patched targets. Engineers at Anthropic with no formal security training asked the model to find remote code execution vulnerabilities overnight, and woke up to complete, working exploits. Rather than releasing Mythos Preview publicly, Anthropic has launched Project Glasswing. Project Glasswing brings together AWS, Apple, Cisco, CrowdStrike, Google, JPMorgan Chase, the Linux Foundation, Microsoft, NVIDIA, and Palo Alto Networks. Anthropic is committing $100M in usage credits. These organizations will use Mythos Preview to identify and patch vulnerabilities in critical software. Commentary has been swift. On Hacker News someone raised practical concerns around the scale of problem this can uncover: …hundreds of millions of embedded devices that cannot be upgraded easily and will be running vulnerable binaries essentially forever. This was a problem before of course, but the ease of chaining vulnerabilities takes the issue to a new level. A