MHS saves weeks by turning hardware integration into a software change — and under the EU Machinery Regulation, a software change to a machine's safety behaviour can make whoever performed it the legal manufacturer. Whether that fires on any given install is currently undecidable from public information, because Anthropic has not published the spec.

Anthropic's 212-page system card says what the launch page does not. Fable 5.1 and Mythos 5.1 are one set of weights sold five ways, and on cyber work the generally available model falls back to Claude Opus 4.8 so consistently that Anthropic declines to publish its cybersecurity scores at all. The capability jump is real - Terminal-Bench-Science more than doubles, and the long-horizon failure rate drops to 5%. But the safeguard layer costs 5.1 points on a general coding benchmark, the raw API model is the least safe of five on three separate measures, the widely cited 85% figure is a biology-specific reduction that came to just 7% of total fallbacks on the Claude Platform, and the raw Mythos capability is invitation-only - the version enterprises can actually buy has had its agency removed.

The 2026 OWASP Top 10 for LLM Applications, published August 4, reordered around agents: Excessive Agency climbed to third, Unbounded Consumption rose four places, and Improper Output Handling fell five. Behind the moves is a methodology change with an awkward result, since practitioners rank prompt injection first while the raw incident record drops it out of the top ten entirely. This guide walks all ten entries with the mechanism, a production failure, and the controls that hold, separating defenses that merely reduce attack success from the architectural bounds that survive an adaptive attacker.