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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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
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R1
Toward 84 · confidence 99
New joint launch story for two already authoritative exact-version model records.
11 Aug 2026
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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.
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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.
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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