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Autonomy and agency

UK AISI finds Claude Mythos Preview can autonomously take over a simulated corporate network

UK AISI found Claude Mythos Preview completed a 32-step corporate-network takeover in three of ten attempts; Anthropic later verified practical downstream impact through large-scale real-world vulnerability discovery.

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CURRENT ASSESSMENT · REVISION 1
TOWARD DOOM55confidence 90/100

Why it moved the index

Independent testing demonstrated end-to-end autonomous compromise across a long simulated attack chain, while later real-world vulnerability discovery verifies practical impact. Magnitude is limited because the range was weakly defended and simulated.

Assessment history

  1. R1
    Toward 55 · confidence 90

    New historical model-specific autonomy result paired with separately dated practical cyber-impact evidence.

    11 Aug 2026

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  1. DoomBench assesses “UK AISI finds Claude Mythos Preview can autonomously take over a simulated corporate network” as evidence moving toward doom, with magnitude 55 and confidence 90 out of 100 in the autonomy and agency category.

  2. The DoomBench assessment of “UK AISI finds Claude Mythos Preview can autonomously take over a simulated corporate network” is based on reporting from UK AI Security Institute and records the editorial rationale, source quality,...

  3. DoomBench summarizes “UK AISI finds Claude Mythos Preview can autonomously take over a simulated corporate network” as follows: UK AISI found Claude Mythos Preview completed a 32-step corporate-network takeover in three of ten attempts;...

    https://www.doombench.com/news/uk-aisi-finds-claude-mythos-preview-can-autonomously-take-over-a-simulated-corporate-network-2026-04-13