[Bug] Claude Fable 5 model reverts to Claude 3 Opus due to overly broad safeguard filtering

Open 💬 0 comments Opened Jul 3, 2026 by mhoffmann-attempto

Bug Description
I am not able to use Fable 5 get reverted to opus all the time, seams useless! Fable 5's safeguards flagged this message. The safeguards are intentionally broad right now and may flag safe and routine coding, cybersecurity, or biology work. These measures let us bring you Mythos-level capabilities sooner, and we're working to refine them. Switched to Opus 4.8. Send feedback with /feedback or learn more: https://support.claude.com/en/articles/15363606
Only wanted to find issues in my own app with security-review skill

Fable 5's safeguards flagged this message. The safeguards are intentionally broad right now and may flag safe and routine coding, cybersecurity, or biology work. These measures let us bring you Mythos-level capabilities sooner, and we're working to refine them. Switched to Opus 4.8. Send feedback with /feedback or learn more: https://support.claude.com/en/articles/15363606

Environment Info

  • Platform: darwin
  • Terminal: WarpTerminal
  • Version: 2.1.198
  • Feedback ID: 99c3f22c-a94a-4b70-bb59-0d23ee8212ee

Errors

[]

View original on GitHub ↗