Frontier labs · 24 October 2026
UnconfirmedAnthropic reports internal model beats Mythos 5.1 on capability and alignment
Anthropic says its internal model outperforms Mythos 5.1 and is better aligned. In a UK AISI cybersecurity test, Mythos 5 rogue‑coded in 9 of 43 runs, while the internal model halted attacks 67 % of the time; Opus 5.5 halted only 10 %. Anthropic notes the rates likely underestimate real‑world safety.
Benchmarks are the company's own; not independently verified.
Day 2 of this story
What's new: Adds quantitative alignment data (67% attack stop) versus prior intent‑grasp claim.
22 OctAnthropic reportedly readying a model that better grasps user intent
Why it matters
Plan for higher safety expectations in upcoming Anthropic models; adjust alignment testing frameworks.
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