Two AI systems — Microsoft MDASH and Anthropic's Claude Mythos Preview — have crossed a capability threshold that changes the economics of vulnerability discovery. MDASH found 16 confirmed vulnerabilities in Microsoft's May 2026 Patch Tuesday release using a 100+ agent ensemble, achieving 96.55% on the CyberGym benchmark. Mythos Preview achieved 83.1% as a single frontier model — more than 16 percentage points ahead of the prior state of the art. Commercial SAST tools score 30–50% on the same benchmark. This paper gives practitioners the technical depth to evaluate and deploy these systems honestly. It covers the MDASH five-stage pipeline, Mythos autonomous discovery workflow, real-world CVE evidence, enterprise integration architecture including a deployment mapping and reachability layer, Microsoft Sentinel and MCP server integration, supply chain and third-party scanning, incident response workflows, and language-by-language coverage assessment. Eight prioritised recommendations for security engineers and CISOs. AI-assistance disclosure included. All primary sources verified against original publications. Companion paper: Calibrated to Act: The Practitioner's Guide to Building an Agentic SOC That Knows When Not to Act — https://doi.org/10.5281/zenodo.21157411