Mythos 5.1

1. Claude Fable 5.1 and Mythos 5.1: The System Card (thezvi.substack.com via hn)

   +1 2w mythos

   At the time of its release Claude Fable 5.1 was, by a healthy margin, the most capable publicly available AI model in the world. As per usual, we have a 200+ page model card, and the assessments start there.

2. Trusted Access To Claude Mythos 5.1 & Fable 5.1 Defensive Security Work (www.reddit.com via reddit)

   2w mythossecuritysonnet+2

   With Claude Mythos 5.1 and Claude Fable 5.1 release, they also announced their Trusted Access For Claude Mythos 5.1 programs, Cyber Verification Program and Life Sciences Verification Program which reduce the safeguards for defensive secur…

3. Discussion Hub for new Claude incident: Elevated errors for multiple models on Sep 3, 2026 (www.reddit.com via reddit)

   2w service-statusmythosopus+1

   Update - We are continuing to work on a fix for this issue. Sep 3, 14:49 UTC Update - An exhaustive list of affected models: Mythos/Fable 5.1, Mythos/Fable 5, Opus 5, Opus 4.8, Opus 4.6.

4. [AINews] Claude Fable/Mythos 5.1: new SOTA model, 75% cache price cut but 70% more output tokens (www.latent.space)

   2w mythosgrokopenai

   With Astra clearly finally warming up for a full launch (with @sama and @openai writing about it again after a month of self imposed pacing), there’s a familiar window to take the narrative with the round robin of model launches, with Grok…

5. Fable 5.1 and Mythos 5.1 Release Discussion Hub (www.reddit.com via reddit)

   2w mythos

   We have had a ton of (mostly) euphoric posts about the 5.1 release - but it's starting to overwhelm the subreddit. So please direct discussion here.

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