mythos will be bad ON PURPOSE on ai "frontier llm research" tasks, this is very very sad for the research community

also the fact that this is un purpose not visible to the user is crazy

When Fable 5 is used for frontier LLM development, it does not notify the user and instead limits the model’s capabilities through methods such as prompt modification, steering vectors, and PEFT.

Anthropic estimated that this would affect approximately 0.03% of traffic.

Labs starting to pull up the ladders on the ability to diffuse AI was inevitable. Doing it without telling the user is misaligned.

DO NOT USE FABLE 5 FOR AI R&D/CODING!!

Interesting tidbit from the Mythos/Fable system card: Anthropic are invisibly nerfing any requests that target frontier LLM development.

LMFAO this can't be real

this is the biggest wake-up call to protect and nourish open source AI

if you don't build out sovereign and independent models+infra closed labs will patronize you to an insulting degree

Anthropic’s new Fable 5 safeguards are fascinating.

When the model is used for frontier LLM development, it apparently does not simply refuse or warn the user. Instead, it quietly limits its own effectiveness through techniques like prompt modification, steering vectors, and PEFT.

That means Claude may still answer, but become deliberately less useful for building frontier AI systems, pretraining pipelines, distributed training infrastructure, or ML accelerators.

Anthropic says this should affect only around 0.03% of traffic, but the precedent is big: They are being selectively capability-throttled in strategically sensitive domains.

Another quite successful prediction by @DKokotajlo : Fable is intentionally nerfed for frontier ML research. This is within ~3 months of Daniel's prediction of Q1 2026 (made in 2023).

Although I don't think Mythos is automating ML research to the same extent as his prediction.

Turns out Fable 5 is shadowbanning AI researchers 🫤

We should really nationalize anthropic at this point cause this is cuuuuuuraaaaaaazy.

Btw this doesn’t just make the model less useful it will nerf your code and tell you it’s not. Like you legitimately cannot use this. And how are we to know whether it touches inference optimization or even harness engineering, if we’re not alerted?

trust & your brand is a long term thing being in the frontier is a short term thing

note that the nerfing here is SILENT. meaning anthropic will SILENTLY NERF and give you WORSE ANSWERS without alerting you

that's honestly demonic

frontier coding abilities, as long as you're only working on react apps

June 9th Researcher Reciprocity License

"if you train on it, you let us generate - reverse terms of use void"

Status quo 1. We teach frontier devs with ICLR/NeurIPS papers, OSS Github contributions 2. They use it to make frontier models 3. Then ban us from exploring our ideas

We need a new license, original thinkers can't be an underclass to a tyrannical researcher fiefdom

looool that's the "hey bigcos, we don't want you to catch up, but please keep paying us shitton" clause.

The best part of all these Claude 5 Fable safety measures is I bet the jailbreaking community will still get past them, so the people doing open research in good faith don't get access to the best models but bad actors maybe can.

this is *totally* done because of deep concern for public safety, and not as an anti-competition move

The real reason they held Mythos back wasn't for your safety, it was for their moat.

How could one possibly implement this without damaging its ability to do performance-critical software engineering?