CWE-bench v2: More coverage, quality, and transparency

Collinear AI released CWE-bench v2, a public set of 100 programmatically scored tasks in which an agent must find and fix a security weakness in a real open-source repository without breaking existing functionality, covering 91 different CWEs, with a held-out set available on request. Of 11 evaluated models, Gemini 4 Argon leads with 67.8% pass@1 and 81.0% pass@4, just ahead of Claude Opus 5.5 (67.3% pass@1, 78.0% pass@4); 95 tasks are solved by at least one model, but even the leader fails 19% of the set on every attempt. The public set, grader and harness are open, and tasks can be run directly from the Hugging Face repo via Harbor.