This is a super exciting release - Claude Fable 5 is the same underlying model as Mythos but with added safeguards. The …
Andrej Karpathy Twitter · Andrej Karpathy (@karpathy) · 2026-06-09
Andrej Karpathy endorses Claude Fable 5 as the new state-of-the-art across benchmarks, describing it as the same underlying model as Claude Mythos with added safeguards and calling it a qualitative major-version step change.
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Extraction
Topics: claude-fable-5model-releasebenchmarksstate-of-the-art
Claims
- Claude Fable 5 is built on the same underlying model as Claude Mythos but with added safeguards.
- Fable 5 achieves state-of-the-art benchmark results by a margin over competing models.
- Beyond benchmark numbers, Karpathy considers Fable 5 a qualitative major-version-worthy step change.
Key quotes
This is a super exciting release - Claude Fable 5 is the same underlying model as Mythos but with added safeguards. The benchmarks are great and it's SOTA on everything by a margin but I'll add that *qualitatively* also, this is a major-version-bump-deserving step change forward.