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The Verge - Tech
Anthropic releases its first Mythos-class model Claude Fable
Anthropic has officially introduced Claude Fable 5, the first model from its Mythos class, noted for its exceptional capabilities particularly in software engineering and complex tasks. Despite past hesitances over public release due to cybersecurity risks, the model features new safeguards intended to block high-risk responses. The testing has shown it performs effectively in 95% of its interactions without reverting to an earlier model, Claude Opus 4.8, which is still available as a fallback for sensitive queries. The company also alludes to a second model, Claude Mythos 5, which seems to lift some of those safeguards, but access is currently limited.
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Published 10 Jun 2026, 09:06 UTC2 min read
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Summary
TL;DR
- Anthropic's Claude Fable 5 is the first model from its Mythos class.
- The model excels in tasks related to software engineering and vision.
- Introduces new safeguards to manage risks in sensitive areas.
- 95% of sessions operated solely on Fable responses.
- Access to Claude Mythos 5 is limited to select organizations.
Interesting facts
- Fable 5 is double the cost of its previous flagship, Claude Opus 4.8.
- The model’s performance improves as tasks lengthen and become more complex.
- Claude Mythos Preview users can upgrade to the more capable Mythos 5 model.