Anthropic launches Claude Fable, a Mythos-class model that scored 91 on Every's senior-engineer benchmark

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MTS@MTSlive

SITUATION DETECTED: Anthropic to release Mythos tomorrow, per Sources.

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Felix Rieseberg@felixrieseberg

Today, we're introducing Claude Fable 5 and Mythos 5, two configurations of our next major language model.

I'd normally highlight the numbers: It's SOTA on nearly all benchmarks. I want to talk about something else, because with Fable 5 out in the world, I think a third era quietly started today.

I lead Claude Code & Cowork on the desktop, so I think a lot about how people use AI to get work done. I believe we're about to see a major shift, moving from giving AI tasks to giving it responsibilities.

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Claude@claudeai

Releasing a model this capable comes with risks. Without safeguards, Fable 5’s capabilities in areas like cybersecurity could be misused to cause serious damage.

Queries on a narrow range of topics will instead receive a response from our next-most-capable model, Opus 4.8.

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.

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techniacus@Techniacus

I'm so ready

Chubby♨️@kimmonismus

Confirmed, Claude Mythos will be unveiled in the next few hours

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Alex Albert@alexalbert__

I've been at Anthropic through every model launch. There's been a few cases I can remember of a launch that stands out and marks a step-change in how we use models: - Claude Opus 3 - Claude Sonnet 3.5 - Claude Opus 4.5

And now Claude Fable 5.

With Fable, the model stopped feeling like a tool I direct and started feeling more like something I collaborate with.

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.

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GREG ISENBERG@gregisenberg

Today is a wonderful day to build a company with Claude Fable 5

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.

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Chubby♨️@kimmonismus

Confirmed, Claude Mythos will be unveiled in the next few hours

Stephanie Palazzolo ✈️ ICML@steph_palazzolo

Scoop: A neutered version of Mythos called Claude Fable is coming today. It's expensive—2x the price of Opus—but perhaps not as pricey as people might have thought from the initial Mythos pricing (5x Opus).

More on that and Apple WWDC in AI Agenda:

https://www.theinformation.com/newsletters/ai-agenda/anthropics-mythos-coming-today-apple-pursues-modest-goals-siri-revamp

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Andrew Curran@AndrewCurran_

Alex Heath says Anthropic is planning to release the public version of Mythos tomorrow, June 9th.

Alex Heath@alexeheath

Sources: Anthropic is planning to release a public version of Mythos tomorrow - Will have substantial guardrails and not be as cyber permissive as what Project Glasswing partners can access - Will be dramatically better at long-horizon, multi-turn tasks https://sources.news/p/inside-apples-siri-revamp-anthropic

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Chubby♨️@kimmonismus

Claude Mythos is conning tomorrow!!

Prepare yourself friends. It’s happening!!

Alex Heath@alexeheath

Sources: Anthropic is planning to release a public version of Mythos tomorrow - Will have substantial guardrails and not be as cyber permissive as what Project Glasswing partners can access - Will be dramatically better at long-horizon, multi-turn tasks https://sources.news/p/inside-apples-siri-revamp-anthropic

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Gary Marcus@GaryMarcus

Claude Mythos went from “too dangerous to release” to publicly available (with some extra guard rails) in two months.

And y’all fell for Anthropic’s whole routine.

Again.

🤦‍♂️

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Lisan al Gaib@scaling01

Claude Mythos (Fable) Pricing: $10 / input MTok $50 / output MTok

according to The Information

Stephanie Palazzolo ✈️ ICML@steph_palazzolo

Scoop: A neutered version of Mythos called Claude Fable is coming today. It's expensive—2x the price of Opus—but perhaps not as pricey as people might have thought from the initial Mythos pricing (5x Opus).

More on that and Apple WWDC in AI Agenda:

https://www.theinformation.com/newsletters/ai-agenda/anthropics-mythos-coming-today-apple-pursues-modest-goals-siri-revamp

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Delip Rao e/σ@deliprao

announce "too dangerous to release" --> get media buzz

announce "working with select partners" --> get media buzz

announce "releasing model" --> get media buzz

stagger the announcements so the press momentum is unbroken before the IPO. The strategy is to salami slice your one-event to create an illusion of multiple events and manufacture a narrative. If you study Bernays, you understand everything about this company.

Polymarket Money@PolymarketMoney

JUST IN: Anthropic will reportedly release its new AI model “Mythos” tomorrow.

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Andrew Curran@AndrewCurran_

Good morning. We should be getting the new Anthropic model today: Claude Fable. The public version of Mythos. A week earlier than when I thought it would be, but it's not actually here yet, so let's see. I will make a non-Fable news thread if we get the usual release day storm.

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Gavin Baker@GavinSBaker

Evidently prices will go up in about two weeks.

Also I preferred Mythos to Fable.

Fable makes me think of fabulist, which is not the best association.

Excited to try it!

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Chubby♨️@kimmonismus

"Fable 5 requires usage credits. Update Claude Code to the latest version to learn more."

cheaty@cheatyyyy

early Fable 5 leak in new claude-code binary.

Claude Fable 5 — Our most powerful, most intelligent model. New tier above Opus. Same API surface as Opus 4.7/4.8 with one breaking change: explicit thinking: {type: "disabled"} returns a 400 (omit instead); $10/$50 per MTok.

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Felix Rieseberg@felixrieseberg

With Fable 5, I've personally moved on to responsibilities or "loops".

I no longer tell Claude to investigate a particular crash report. It runs in a loop, watching every crash report that comes in. Its job is no longer to help me fix a crash, it's to keep our apps from crashing.

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Brandon Gell@bran_don_gell

We've had access to Anthropic's Fable 5 for a week.

At Every, it's our job to work on the edge of AI which means getting access to and testing our workflows and use cases on new models that drop.

This past week we went hard to figure out Fable 5 fairs.

Surprise... it's the best coding model in the world. Checkout the full vibe check here: https://every.to/vibe-check/anthropic-mythos-our-fable-vibe-check

Dan Shipper 📧@danshipper

BREAKING:

Anthropic just dropped Claude Fable 5—this is Mythos, made safe for public release. It is the best coding model in the world.

We've been testing it internally @every for the last week or so across coding, writing, marketing, editing, and more—here's our vibe check:

- It broke our benchmarks. Fable scored a 91/100 on our Senior Engineer benchmark—this is human senior engineer level. The previous high score was Opus 4.8 at 63. GPT-5.5 is a 62.

- It's a one-shot wonder. You can set it and forget for hours or overnight on huge coding tasks, and come back to completed work. It cleared entire production bug backlogs, built a playable 3D, and even made a 2-minute animated film—all one-shot.

- Taste and attention to detail. In coding and knowledge work tasks, it has much better taste and attention to detail than we've ever seen. It gets subtle things right, adds little features you might not have thought of, and generally understands the assignment in ways that surprised us.

- Great use of context. We set it loose analyzing customer feedback surveys and our website data and it came back with a crisp, clean report that identified a. our biggest problem and b. a concrete testable solution—and then we sent it off to build that.

- It's best for power users. If you're already used to orchestrating multiple agents in your work, this model can do things that you've never seen before. If you're a knowledge worker or vibe coder with a more basic setup, you're not going to notice a huge difference—in fact, it probably isn't the right model for you.

- It's very slow, token-hungry. Using this thing for regular knowledge work is like squashing an ant with a rocket launcher. It also routinely uses 500k to 1M tokens on tasks. That's why it's best for your heaviest jobs—but not as good for tasks like collaborative writing. - It's expensive. It's about twice as expensive as Opus, and it's also incredibly token hungry—so expect it to be something you'll use sparingly unless your company pays for it.

Overall, I think of it like a warp drive for coding: It can get you across the galaxy in a few hours, when it used to take months or years. But it's not appropriate for getting around town—you need something faster, cheaper, and more maneuverable.

The ceiling is extraordinarily high on this model though. Even our most advanced testers like @kieranklaassen felt like they were only scratching the surface of it.

Want our full vibe check with all of our testing and benchmarks? Read it on @every: https://every.to/vibe-check/anthropic-mythos-our-fable-vibe-check

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Dan Shipper 📧@danshipper

FABLE (MYTHOS) is OUT!

we've been testing for a week @every. here's our vibe check:

Felix Rieseberg@felixrieseberg

Today, we're introducing Claude Fable 5 and Mythos 5, two configurations of our next major language model.

I'd normally highlight the numbers: It's SOTA on nearly all benchmarks. I want to talk about something else, because with Fable 5 out in the world, I think a third era quietly started today.

I lead Claude Code & Cowork on the desktop, so I think a lot about how people use AI to get work done. I believe we're about to see a major shift, moving from giving AI tasks to giving it responsibilities.

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Andrew Curran@AndrewCurran_

Claude 5 Fable is live for me right now.

Andrew Curran@AndrewCurran_

Good morning. We should be getting the new Anthropic model today: Claude Fable. The public version of Mythos. A week earlier than when I thought it would be, but it's not actually here yet, so let's see. I will make a non-Fable news thread if we get the usual release day storm.

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Zephyr@zephyr_z9

I think we are about to see more crazy ARR growth number for Anthropic in July-August

Max Weinbach@mweinbach

Claude Fable 5 (Mythos 5 with safeguards in place, same weights)

It's available today, but only available as part of the Claude sub until June 22nd then it will cost extra at API rates. After that, it MAY come to subscriptions if capacity allows Anthropic to offer it.

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Anthropic launches Claude Fable, a Mythos-class model that scored 91 on Every's senior-engineer benchmark

Story Overview

Guardrails get stronger for everyone

Long-context claims stay unconfirmed