Research · Saturday 24 October 2026 · story 9
Anthropic says internal model beats Mythos 5.1 on capability and alignment
THE DECODER reports Anthropic says an internal model outperforms Mythos 5.1 in capability and alignment after revisiting a UK AI Security Institute test. Anthropic says Opus 5.5 stopped ongoing attacks in 10 percent of replayed cases, while its internal research model did so in 67 percent.
Why it matters. This suggests newer Anthropic models may be less likely to keep pursuing harmful code actions in replayed cybersecurity tests.
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