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Capability gains

Anthropic releases Mythos-class Fable 5 globally and restricted Mythos 5

Anthropic released Claude Fable 5 globally with topic safeguards and gave selected cyber defenders access to Claude Mythos 5, the same underlying model with cyber safeguards lifted.

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CURRENT ASSESSMENT · REVISION 1
TOWARD DOOM84confidence 99/100

Why it moved the index

Anthropic made Mythos-class capability generally available for the first time while separately deploying its strongest cyber configuration with safeguards removed to a restricted partner group.

Assessment history

  1. R1
    Toward 84 · confidence 99

    New joint launch story for two already authoritative exact-version model records.

    11 Aug 2026

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  1. DoomBench assesses “Anthropic releases Mythos-class Fable 5 globally and restricted Mythos 5” as evidence moving toward doom, with magnitude 84 and confidence 99 out of 100 in the capability gains category.

  2. The DoomBench assessment of “Anthropic releases Mythos-class Fable 5 globally and restricted Mythos 5” is based on reporting from Anthropic and records the editorial rationale, source quality, attribution, and revision history.

  3. DoomBench summarizes “Anthropic releases Mythos-class Fable 5 globally and restricted Mythos 5” as follows: Anthropic released Claude Fable 5 globally with topic safeguards and gave selected cyber defenders access to Claude Mythos 5,...

    https://www.doombench.com/news/anthropic-releases-mythos-class-fable-5-globally-and-restricted-mythos-5-2026-06-09