Claude Mythos Preview: Anthropic's Most Powerful Model They Won't Release

Claude Mythos Preview: Anthropic's Most Powerful Model They Won't Release On April 7, 2026, Anthropic made an unprecedented announcement. They published a 244-page System Card for their most powerful model — Claude Mythos Preview — and simultaneously declared they would not release it to the public. The reason: its cybersecurity capabilities are too dangerous. The Benchmarks Tell a Clear Story Claude Mythos Preview doesn't just beat Opus 4.6 — it operates on a different level entirely. Benchmark Mythos Opus 4.6 Gap SWE-bench Pro 77.8% 53.4% +24.4p SWE-bench Multimodal 59.0% 27.1% +31.9p Terminal-Bench 2.0 82.0% 65.4% +16.6p Cybench 100% — First ever Humanity's Last Exam (tools) 64.7% 53.1% +11.6p BrowseComp improved while using 4.9x fewer tokens . USAMO math olympiad showed "generational improvement." The Cybersecurity Problem This is the core reason for the restricted release: OpenBSD : Found a 27-year-old TCP SACK kernel crash bug FreeBSD NFS : Found a 17-year-old remote code executi