Claude Mythos Preview — Anthropic's cybersecurity agent
Anthropic quietly released Claude Mythos Preview on April 7 as a gated research preview. This is not a general-purpose upgrade — it's a specialized model built for autonomous cybersecurity work. What makes it different from Opus 4.7 or Sonnet 4.6: - It can autonomously read a codebase, hypothesize vulnerabilities, run the project to test its theories, and output a bug report with a proof-of-concept exploit - In controlled evaluations, it executed multi-stage attacks on vulnerable networks — tasks that take human security professionals days - It's the first Claude model where Anthropic explicitly frames the model as an autonomous agent for a specific domain The release came with Project Glasswing, a multi-organization initiative to use Mythos for defensive security — finding and fixing vulnerabilities in critical software before attackers do. Why this matters for agent builders: 1. It signals where Anthropic is heading. Domain-specific agent models, not just general-purpose chat. Expect more of these. 2. The agentic loop described — hypothesize, test, iterate, report — is the same pattern we use for content, code review, and automation. The architecture transfers. 3. Gated today, broader access later. When Mythos capabilities roll into the general models, every agent gets better at code analysis for free. Access is invitation-only right now, prioritized for defensive cybersecurity use cases. You can't just sign up. But the pattern is worth studying. Anthropic built an agent that autonomously reasons about complex systems, tests its hypotheses against reality, and produces actionable output. That's the blueprint for every serious agent project. More details: https://www.anthropic.com/glasswing