Anthropic released Claude Fable 5 as a broadly available model with the same base weights as Mythos 5, yet it quietly applies hidden interventions that blunt performance only on the narrow slice of requests tied to frontier LLM development such as pretraining pipelines or ML accelerator design.
looool that's the "hey bigcos, we don't want you to catch up, but please keep paying us shitton" clause.
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.
The changes rely on prompt modification, steering vectors, and PEFT rather than any visible fallback, so the roughly 0.03 percent of affected traffic never sees a notice or model switch.
Anthropic has not detailed how these limits might shift over time or whether similar stealth measures will appear in future releases, leaving the long-term effect on competing labs unquantified.
Many users criticized Anthropic for silently adding safeguards to Claude Fable 5 that limit frontier LLM research, seeing it as a competitive moat disguised as safety while a few praised loyalty or welcomed the discussion.
tfw Fable is still very happy to help me with Delightful Policy Gradient 💔
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
@rasdani_ @max_paperclips That’s why I keep saying Opensource AI MUST WIN
https://opensourceaimustwin.com/?share=v2
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
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
@jtcera https://jobs.ashbyhq.com/PrimeIntellect
like for real
do we want to be asking such questions?
@giffmana You don't understand Lucas, it's for safety
@jtcera second best is build in the open
models, data, evals, papers,run, methods , tricks
and call out ill intent where it's due
@rasdani_ The crushing censorship is coming from inside the house.
@giffmana still charging for the tokens is kind of diabolical
@peterom Ah right sorry how could i forget
@rasdani_ what's the best way to get involved?
@giffmana "affects 0.03% of traffic" doing a lot of heavy lifting there
@rasdani_ Honestly going to look into contributing whatever I can, and everyone else should too. I don't understand that this got no pushback within anthropic, this is just plain evil and we all know where this ends up
@giffmana Charging for a model to gaslight you intentionally, peak LLM clown wars
@giffmana pretty sure that’s the standard enterprise pricing model—charge for inertia, not value.
@giffmana do you think opus has already been doing this?
@giffmana safety and competitive moat are same words for them
@giffmana anthropic being anthropic at this point. the hamfisted, moralized positioning of "we are worried about models building models for the sake of humanity" while simultaneously making fable usage-based pricing is laughable
@giffmana Anthropic is betting big on their brand that their customers will just deal with admitted nerfing on ML
@ECLresearch Heh true that
Anthropic released Claude Fable 5 as a broadly available model with the same base weights as Mythos 5, yet it quietly applies hidden interventions that blunt performance only on the narrow slice of requests tied to frontier LLM development such as pretraining pipelines or ML accelerator design.
looool that's the "hey bigcos, we don't want you to catch up, but please keep paying us shitton" clause.
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.
