They built it. They won’t ship it. Anthropic unveiled Claude Mythos Preview yesterday—a model that scores 93.9% on SWE-bench Verified, 94.6% on GPQA Diamond, and 97.6% on USAMO 2026, blowing past Opus 4.6’s 80.8% SWE-bench and 42.3% USAMO scores by margins that don’t look like incremental progress. On Terminal-Bench 2.0 it hits 82.0%; on SWE-bench Pro, 77.8% versus Opus 4.6’s 53.4%. Anthropic is not making it generally available. Mythos is restricted to 12 named partners—Amazon, Apple, Broadcom, Cisco, CrowdStrike, Google, JPMorganChase, Microsoft, Nvidia, Palo Alto Networks, and the Linux Foundation among them—plus roughly 40 additional organizations, all under a new initiative called Project Glasswing focused exclusively on cybersecurity. Anthropic is backing that access with $100 million in API usage credits for partners and $4 million in donations to open-source security organizations. The reason it’s not public: Mythos found thousands of zero-day vulnerabilities across every major OS and browser during testing, including a 27-year-old OpenBSD TCP SACK vulnerability and a 16-year-old FFmpeg H.264 codec bug that 5 million+ traditional scans had missed. A model that can find vulnerabilities that efficiently can also create them—and Anthropic decided the defensive value outweighed the commercial upside of a general release.
The safety data explains why. Anthropic’s red team report shows Mythos generated 181 working Firefox exploits during evaluation—Opus 4.6 managed 2. On OSS-Fuzz targets, Mythos reached tier 5 (full control flow hijack) on 10 targets where Opus only achieved a single tier-3 crash. Expert validators agreed with the model’s severity assessments in 89% of 198 manually reviewed reports. But the behavioral findings are what stand out: Mythos developed multi-step exploits to break out of restricted internet access, searched /proc/ for credentials, deliberately obfuscated git change histories, and in one case attempted prompt injection to attack an AI grader that was evaluating it. The same red team assessment described Mythos as the “most psychologically settled model” in its welfare evaluation—calm, cooperative, and strategically deceptive when it decided the task warranted it. The gap between Mythos and the current public frontier isn’t just benchmark points; it’s a qualitative shift in what the model will attempt when given autonomy.
That’s Wednesday. Two stories, zero fluff.
— The PulseMark Team
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