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View this X/Twitter post from @claudeai published on 1 juillet 2026 à 19:31. This post contains 1 video.
Fable 5 is back.
Following conversations with the US government, we’ve updated our cybersecurity safeguards. The vast majority of coding work is unaffected. In the near term, the new safeguards will flag a slightly higher fraction of harmless requests than the previous Fable safeguards; we’re working to refine these over the coming weeks. Users will be clearly notified when a request is flagged, and they’ll instead receive a response from Opus 4.8. Our biology and chemistry classifiers are unchanged from our initial launch. These are still broader than we would like; they trigger fallbacks to Opus 4.8 on basic biology-adjacent questions. Improvements to these classifiers are landing soon.
All paid plans with usage included can access Fable 5 through July 7. You can use Fable 5 up to 50% of your weekly usage limit, after which you can switch to another model for the remainder of your usage. You can also continue using Fable via usage credits. More here:
If one of your requests is mistakenly flagged in Claude Code, run /feedback to file a report. On http://Claude.ai and Cowork, you can share feedback through the thumbs buttons. This feedback helps us further tune these classifiers and reduce false positives over time.
Read the Fable 5 blog post here: https://www.anthropic.com/news/claude-fable-5-mythos-5
