Anthropic launches guarded Claude Fable 5 AI model

Artificial Intelligence

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Sam Mendoza

·5 months ago
shared a link post in group #Artificial Intelligencevia#The Most Important Thing
Anthropic launched Claude Fable 5, the first “Mythos-class” model they’ve released to the public. Anthropic considered the original Claude Mythos too dangerous to release, making it available only to select cyber defenders in April. While some critics dismissed this as “fear-based marketing,” partner companies found Claude Mythos Preview highly capable at generating novel exploits — Firefox reported increasing their bug fixes from 76 in March to 423 in April. #Artificial Intelligence Now Anthropic is releasing Fable 5, a version of Mythos with added guardrails designed to prevent misuse. The company is also releasing a new Mythos model to its Project Glasswing partners and select biology researchers. To prevent the public from accessing dangerous capabilities, Claude Fable 5 will route cybersecurity, biology, and chemistry questions to Anthropic’s next-most-advanced model, Claude Opus 4.8. Claude will do the same for queries suspected of being distillation attempts. Anthropic says that because it has “tuned the safeguards to be cautious,” occasionally “benign requests will trigger our classifiers.” They write: “We recognize that this will be frustrating to some users, and our aim is to reduce false positives as we update” the guardrails. Anthropic says it expects significant demand for Fable 5. As a result, it has created a somewhat arcane rollout plan. From now until June 22, Fable will be included in Pro, Max, Team, and seat-based Enterprise plans. Starting June 23, Fable will require separately purchased usage credits. But eventually, the company will “aim to restore Fable 5 as a standard part of subscription plans,” it said. Anthropic also changed its data retention policy for Fable and Mythos. The company will now retain traffic data for 30 days to enable investigations related to misuse. The company promised it won’t use that data to train Claude “or for any non-safety-related purpose.” https://www.anthropic.com..
Claude Fable 5 and Claude Mythos 5
www.anthropic.com

Claude Fable 5 and Claude Mythos 5

Today we’re launching Claude Fable 5: a Mythos-class model that we’ve made safe for general use.

 
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Jerome Cody

The White House lifted export restrictions on Anthropic’s Fable 5, according to a U.S. official. In a post on X, Anthropic said the U.S. government notified it that it has lifted export controls on its Fable 5 model, along with Mythos 5. The company said it will begin restoring customer access to the models on Wednesday. The government’s move, first reported by Politico, was confirmed by a U.S. official. On June 12, the federal government forced Anthropic to withdraw Mythos 5 and Fable 5, a version of Mythos with extra cyberattack safeguards, from the market over national security concerns. The government partially eased the restrictions on Mythos on Friday. To address government concerns, Anthropic implemented a new safeguard to Fable that targets and blocks behavior described in a reported bypass of its protections that triggered the administration’s move, a person close to the company said. The person added that researchers from the Commerce Department’s Center for AI Standards and Innovation have validated both the prior and new safeguards. The lifting of the restrictions comes as the administration balances frontier-model security risks against pressure to keep pace with China’s AI development. OpenAI faced similar treatment last week, agreeing to a limited rollout of its GPT-5.6 model despite CEO Sam Altman’s objections. Industry figures hope a forthcoming executive order will replace ad hoc decisions with a predictable evaluation process. politico.com/news/2026/06..
Trump lifts limits on Anthropic’s Fable and Mythos models

www.politico.com

Trump lifts limits on Anthropic’s Fable and Mythos models

The action could resolve weeks of drama that had cut off widespread access to two of the U.S. tech company's most advanced AI products.

 

Tasia

Epic Games CEO Tim Sweeney wrote, “Thanks for keeping us safe Claude Fable 5!” posting the following conversation: #Artificial Intelligence #DANK MEMES

 
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Sam Mendoza

Satya Nadella thinks so. In a meeting with Copilot engineers this week, the Microsoft CEO reportedly argued that Anthropic’s Fable model feels “editorially controlled,” and refuses too many requests that don’t pose immediate national or cyber security threats. “It doesn’t make sense,” he added, according to attendees who provided a copy of his remarks to CNBC. Fable 5, of course, is Anthropic’s attempt to safely release its powerful Mythos 5 model to the general public. (Both models were held back due to its potential for misuse in developing bioweapons, cybersecurity threats, and so forth.) It now appears that the AI lab’s attempts to rein in Mythos may have hurt its everyday usability, opening the door for competitive releases from rival frontier labs along with Chinese open source projects. cnbc.com/2026/07/16/micro..
Microsoft's Nadella criticizes Anthropic's Fable for being 'editorially controlled'

www.cnbc.com

Microsoft's Nadella criticizes Anthropic's Fable for being 'editorially controlled'

Microsoft enjoys close ties to Anthropic, but it's also working to help companies refine models that keep their data private.

 
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Cyril

Sam Mendoza
Satya Nadella thinks so. In a meeting wi...
Microsoft cannot patch as fast as AI finds bugs: Anthropic’s Mythos model turned up 90 critical and 141 important SharePoint flaws in April alone, most of them still unfixed weeks later. July 14 brought patches for more than 600 bugs, an all-time record against June’s previous high of about 200. propublica.org/article/an..
Anthropic’s New AI Model Can Identify More Software Bugs Than Ever. Microsoft Is Struggling to Fix Them Fast Enough.

www.propublica.org

Anthropic’s New AI Model Can Identify More Software Bugs Than Ever. Microsoft Is Struggling to Fix Them Fast Enough.

Anthropic’s Mythos has flagged bugs faster than Microsoft can fix them. Documents reviewed by ProPublica reveal the tech giant's “mad dash” behind the scenes to patch holes before hackers can find and exploit them.

 
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Cyril

Anthropic released upgrades to its top AI models that it said deliver better performance and lower cost. Claude Fable 5.1 will cost an estimated 25% less than Fable 5 for token-based billing on what Anthropic described as typical workloads, the company said in a blogpost (anthropic.com/claude-fabl.. ) Tuesday, adding that the savings could be much larger for some highly agentic work. Fable 5.1 will also eventually include a new data system called Enterprise Frontier Safeguards that Anthropic said will give customers the same privacy as a zero data retention policy while preventing adversarial use. That will become available to business customers beginning later this fall, it said. Anthropic also released Claude Mythos 5.1, which is the same underlying model designed for more advanced cybersecurity and life sciences work, through its trusted access programs. The company said it also has improved its cybersecurity safeguards to reduce the number of instances where it flags benign content as dangerous.
Introducing Claude Fable 5.1 and Claude Mythos 5.1 \ Anthropic

www.anthropic.com

Introducing Claude Fable 5.1 and Claude Mythos 5.1 \ Anthropic

Our most advanced models for coding and knowledge work. Their research capabilities also offer an early glimpse of how AI models will contribute to scientific progress.

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