Claude Mythos 5.1

Same weights as Fable 5.1, fewer safeguards. Restricted to cyberdefenders and life scientists via trusted access.

by @claudeaiAdded Sep 2, 2026

mythos claude ai security

Claude

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Claude Fable 5.1 is available everywhere today. Claude Mythos 5.1, our model for cyberdefenders and life scientists, is available through trusted access programs. Read more: anthropic.com/claude-fable-a…

6:03 PM · Sep 1, 2026

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Matthew Jörke

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I built thimble, an open source Claude Code plugin that makes it easy to understand what agents did. It adds explainers and interactive visualizations in your terminal. If Claude Code is for building, thimble is for understanding. Install thimble here! github.com/safety-researc…

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