Anthropic released the same model twice, at two different safety levels
Anthropic released one model twice on 1 September. Same weights, same price. The difference is who is allowed to switch the safety off.
Claude Fable 5.1 is generally available with the classifiers on. Claude Mythos 5.1 is the same model with them removed, and goes only to vetted US organisations in a programme called Project Glasswing, aimed at cybersecurity and life sciences work. Pricing holds at $10 and $50 per million tokens, but cache reads drop to a quarter of the old rate, taking up to 45% off an agentic run. Terminal-Bench 4.0 goes from 42.0% to 55.8%.
Why this one is different
The industry's usual product ladder is capability: pay more, get a better model. This is a ladder of permission. The capability is identical and the tiering is entirely about who you are, which is the same structure OpenAI used for GPT-5.6-Cyber and Google for Fairwind. Three labs, three weeks, and the frontier quietly became something you qualify for rather than something you buy.
Not a ladder of capability. A ladder of permission.
How we got here
- 24 Jul 2026Claude Opus 5, with thinking on by default.
- 10 Aug 2026OpenAI gates GPT-5.6-Cyber behind Daybreak Red. The first of the three.
- 1 Sep 2026Fable 5.1 and Mythos 5.1: the same model at two safeguard levels, sold to two different kinds of customer.
- 2 Sep 2026Google's Fairwind Program does it again, one day later.
What it does and does not mean
A 45% saving on cache reads is not a 45% saving. It applies to re-reading a long context, which is most of the cost of a long agentic run and almost none of the cost of a short chat, so whether it reaches your bill depends entirely on what you are doing. And every benchmark here is self-reported. What is not in doubt is the structure: the most capable version of this model is not for sale, and access to it is a decision Anthropic makes about you.