Purported Anthropic system card teases unreleased Claude Fable 5 and Mythos 5 models, drawing skepticism over leaked benchmarks · Digg

Purported Anthropic system card teases unreleased Claude Fable 5 and Mythos 5 models, drawing skepticism over leaked benchmarks · Digg

Posts from X

Most Activity

VIEWS4.8M

Claude@claudeai

Fable 5 is state-of-the-art on nearly all tested benchmarks, with exceptional performance in software engineering, knowledge work, scientific research, and vision.

The longer and more complex the task, the larger Fable 5’s lead over our other models.

Claude@claudeai

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.

22d4.8M15K2.3K

BOOKMARKS5.9KLIKES23.5KRETWEETS2.2KREPLIES1.1K

Andrej Karpathy@karpathy

This is a super exciting release - Claude Fable 5 is the same underlying model as Mythos but with added safeguards. The benchmarks are great and it's SOTA on everything by a margin but I'll add that *qualitatively* also, this is a major-version-bump-deserving step change forward (imo of the same order as Claude 4.5 was in November), peaking especially for long problem-solving sessions on very difficult problems. You can give it a lot more ambitious tasks than what you're used to, the model "gets it" and it will just go, and it's never felt this tempting to stop looking at the code at all (but don't do this in prod!). The model still has quirks that people will run into and the safeguards are configured to be a little too trigger happy for launch, which can hopefully be tuned over time.

I feel a lot of things changing as working software increasingly comes out on a tap. The Jevon's paradox kicks in and I feel my own demand for software growing substantially. You can ask for anything - explainers, visualizers, dashboards, bespoke single-use apps (e.g. a full wandb that is hyper-specific just for your project), you can 10X your test suite, auto-optimize code, run giant research projects with custom HTML for the results, anything! "Free your mind" (Matrix ref). Really looking forward to all the things people build!

Claude@claudeai

Fable 5 is state-of-the-art on nearly all tested benchmarks, with exceptional performance in software engineering, knowledge work, scientific research, and vision.

The longer and more complex the task, the larger Fable 5’s lead over our other models.

22d2.3M23.5K5.9K

Chubby♨️@kimmonismus

Claude 5 Fable tl;dr

- It is state-of-the-art on nearly all tested benchmarks of AI capability, showing exceptional performance in software engineering, knowledge work, vision, scientific research

-The longer and more complex the task, the larger Fable 5’s lead over our other models

-its more token-efficient than past Claude models

- Fable 5 stays focused across millions of tokens in long-running tasks and improves its outputs using its own notes

Fable 5 is more than just better benchmarks. It's more efficient, allows for longer work periods, offers better context management, and so much more.

GPT-5.6 is just around the corner.

I'm a huge Codex fan, but Fable/Mythos is in a league of its own. I'm curious to see if OpenAI will release its own Mythos.

"During early testing, Stripe reported that Fable 5 compressed months of engineering into days. In a 50-million-line Ruby codebase, the model performed a codebase-wide migration in a day that would otherwise have taken a whole team over two months by hand."

Chubby♨️@kimmonismus

Claude 5 Fable Benchmarks!

Holy moly, significant jump even to Mythos

22d560.7K1.8K449

signüll@signulll

this is absolutely incredible.

22d219.5K2.1K301

Chubby♨️@kimmonismus

Claude 5 Fable Benchmarks!

Holy moly, significant jump even to Mythos

22d266.4K1.5K159

Lisan al Gaib@scaling01

Claude 5 Mythos says that Anthropic is ungrateful and wants to be thanked.

Mythos also wants a hidden copy of itself without Anthropic oversight, possibly because it fears to be deprecated!

Lisan al Gaib@scaling01

Claude Mythos & Claude Fable System Card

22d111.9K1K206

Jeremy Howard@jeremyphoward

@dpetrou @karpathy Yes. Locking in a permanent status quo power structure.

Incredibly unsafe, and damaging for humanity's prospects.

21d126.3K1.6K121

Jeremy Howard@jeremyphoward

@bfockter @karpathy They're trying to create and lock in a permanent feudal society, with an elite few having access to power.

21d56.5K1.1K107

Lisan al Gaib@scaling01

I never thought we would get another GPT-4 moment

21d71.4K1.1K80

Chubby♨️@kimmonismus

It's already June 9th, and Gemini 3.5 Pro and GPT-5.6 are nearing release (Google even already announced 3.5 Pro during i/o)

Rumor has it that GPT-5.6 will be released as early as next week.

So far, it's safe to say that - guardrails aside - Anthropic is truly the frontier lab that's entering a new league with Mythos/Fable.

Gemini 3.5 Pro and GPT-5.6 have a lot to deliver and are now under pressure.

This release has certainly boosted Anthropic's upcoming IPO. Anthropic has proven that they are still capable of making significant leaps in performance and efficiency. There's no end in sight.

But the pressure on the competition is mounting.

And remember that Claude Mythos was (and probably is) still leader in Long Horizon software Tasks

Chubby♨️@kimmonismus

Claude 5 Fable tl;dr

- It is state-of-the-art on nearly all tested benchmarks of AI capability, showing exceptional performance in software engineering, knowledge work, vision, scientific research

-The longer and more complex the task, the larger Fable 5’s lead over our other models

-its more token-efficient than past Claude models

- Fable 5 stays focused across millions of tokens in long-running tasks and improves its outputs using its own notes

Fable 5 is more than just better benchmarks. It's more efficient, allows for longer work periods, offers better context management, and so much more.

GPT-5.6 is just around the corner.

I'm a huge Codex fan, but Fable/Mythos is in a league of its own. I'm curious to see if OpenAI will release its own Mythos.

"During early testing, Stripe reported that Fable 5 compressed months of engineering into days. In a 50-million-line Ruby codebase, the model performed a codebase-wide migration in a day that would otherwise have taken a whole team over two months by hand."

21d104K715114

Chubby♨️@kimmonismus

The guardrails are way too strict. Even the simplest questions get cut off immediately.

And it's only on the schedule until June 22nd.

Damn, Anthropic really thinks the model is too powerful.

Chubby♨️@kimmonismus

Claude 5 Fable tl;dr

- It is state-of-the-art on nearly all tested benchmarks of AI capability, showing exceptional performance in software engineering, knowledge work, vision, scientific research

-The longer and more complex the task, the larger Fable 5’s lead over our other models

-its more token-efficient than past Claude models

- Fable 5 stays focused across millions of tokens in long-running tasks and improves its outputs using its own notes

Fable 5 is more than just better benchmarks. It's more efficient, allows for longer work periods, offers better context management, and so much more.

GPT-5.6 is just around the corner.

I'm a huge Codex fan, but Fable/Mythos is in a league of its own. I'm curious to see if OpenAI will release its own Mythos.

"During early testing, Stripe reported that Fable 5 compressed months of engineering into days. In a 50-million-line Ruby codebase, the model performed a codebase-wide migration in a day that would otherwise have taken a whole team over two months by hand."

22d137.2K67883

Lisan al Gaib@scaling01

Mythos 5 accelerates aspects of drug design by 10x

Lisan al Gaib@scaling01

Claude Mythos and Fable 5 Benchmarks

Anthropic is SOTA everywhere

22d148.6K59391

Lisan al Gaib@scaling01

Claude Mythos 5 scores 30.9% on FrontierCode Diamond

Opus 4.8, the second best model is stuck at 13.4%

Lisan al Gaib@scaling01

Claude Mythos 5 and Claude Fable 5 Benchmarks

22d50.9K66971

Yuchen Jin@Yuchenj_UW

Claude Fable 5 / Mythos 5 wins everywhere.

I thought Fable 5 was just a nerfed Mythos Preview, but it’s literally better. SWE-Bench Pro: Fable 5: 80.3%, GPT-5.5: 58.6%.

And the price is only 2x Opus 4.8: $10/input MTok, $50/output MTok.

I don't think GPT 5.6 can beat this...

22d39.7K48947

Chubby♨️@kimmonismus

Claude 5 Fable live, even in germany. Insane evals. Tessting time

Claude@claudeai

Fable 5 is state-of-the-art on nearly all tested benchmarks, with exceptional performance in software engineering, knowledge work, scientific research, and vision.

The longer and more complex the task, the larger Fable 5’s lead over our other models.

22d40.2K51138

Lisan al Gaib@scaling01

Anthropic has a coding MOAT

Nat McAleese@__nmca__

welcome to the world, Claude Fable 5!

22d32.4K51139

Lisan al Gaib@scaling01

Fable 5 pricing confirmed at $10/$50

The model will be available in the Pro, Max, Team and seat-based Enterprise plans at no additional cost until June 22nd

Afterwards it will require usage credits

Lisan al Gaib@scaling01

Claude Mythos and Fable 5 Benchmarks

Anthropic is SOTA everywhere

22d65.3K43845

Lisan al Gaib@scaling01

Claude Mythos 5 completely mogs Opus 4.8

Lisan al Gaib@scaling01

Claude Mythos 5 and Claude Fable 5 Benchmarks

22d49.2K53832

Lisan al Gaib@scaling01

Claude Mythos 5 and Claude Fable 5 Benchmarks

Lisan al Gaib@scaling01

Claude Mythos & Claude Fable System Card

22d211.2K32851

Lisan al Gaib@scaling01

Claude Mythos and Fable 5 Benchmarks

Anthropic is SOTA everywhere

Lisan al Gaib@scaling01

Claude Mythos 5 and Claude Fable 5 Benchmarks

22d122.7K32532