Anthropic has cleared its first Mythos-class model for broad public access, delivering Claude Fable 5 as the company's strongest generally available option yet for extended agentic work in coding, knowledge tasks, and tool use while keeping the same base architecture as the more restricted Mythos 5 variant.
Claude Fable 5 is out today. The first Mythos-class model everyone can use & the first model I hand off whole projects to. This weekend I built a self-maintaining, proactive media tracker for myself, over 2 days with Fable taking large chunks at a time
Tables shared in launch posts place Fable 5 ahead on agentic coding, knowledge work, and tool-use metrics compared with Opus 4.8 and competing models like GPT 5.5, though full official model card details live on Anthropic's site.
High-risk prompts involving cybersecurity, biology, or model distillation automatically fall back to Opus 4.8 with user notification and no token charge; reroutes remain under 5 percent of sessions and data is kept for 30 days.
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use.
Its capabilities exceed those of any model we’ve ever made generally available.
Fable 5 is now available in Claude Code and Cowork
Fable is the best model I have used for coding, by a wide margin. It is a big step up, enabling less prompts and steers, more efficient token use, better code quality, better tool use, more intelligent self-verification, longer running sessions, and higher trust & autonomy.
Happy coding!
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use.
Its capabilities exceed those of any model we’ve ever made generally available.
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
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use.
Its capabilities exceed those of any model we’ve ever made generally available.
Holy shit they actually launched it
If you thought AI progress was slowing down, well here's the immediate answer to that. Huge jump in capability across the board. This is going to deliver major improvement in agents across almost all knowledge work categories.
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use.
Its capabilities exceed those of any model we’ve ever made generally available.
My favorite chart from our system card - FrontierCode is an excellent eval, and it accurately reflects the step up I feel when using Fable!
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use.
Its capabilities exceed those of any model we’ve ever made generally available.
LMFAO this can't be real
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
@claudeai let the monthly migration from codex to claude code begin
@claudeai It's agi guys.
Claude Fable is the first non-slop-coder LLM 👌
This new Frontier Code benchmark demonstrates this clear
@claudeai Chat, isn't it too early???
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
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
It’s out, less expensive than expected and a huge increase in capabilities.
I’ll be testing this over the next week but imagine the internal acceleration ant are having with models like these atm.
Anthropic going for ASI while leaving everyone else in the dust
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
@claudeai good progress...
@claudeai Fantastic. In one 50-million-line Ruby codebase, Fable 5 finished a migration in one day that would have taken a whole team more than two months by hand.
Claude Fanle just dropped and it's the best model yet from anyone
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use.
Its capabilities exceed those of any model we’ve ever made generally available.
I just got bullied by AGI
Introducing Claude Fable 5: a Mythos-class model that we’ve made safe for general use.
Its capabilities exceed those of any model we’ve ever made generally available.
The crazy jump in perf for Claude 5 Fable is vindication for people who say Opus 4.5 and were like "yeah I should (mostly) stop writing code by hand and get ready for the future." More jumps still to come!
Anthropic has cleared its first Mythos-class model for broad public access, delivering Claude Fable 5 as the company's strongest generally available option yet for extended agentic work in coding, knowledge tasks, and tool use while keeping the same base architecture as the more restricted Mythos 5 variant.
Claude Fable 5 is out today. The first Mythos-class model everyone can use & the first model I hand off whole projects to. This weekend I built a self-maintaining, proactive media tracker for myself, over 2 days with Fable taking large chunks at a time
