One of the central points of the launch is the focus on security. Anthropic explained that it subjected Fable 5 to extensive testing to detect vulnerabilities and possible attempts to evade restrictions.
The security measures implemented by Anthropic
"We conducted an internal external bug bounty program that did not find universal jailbreaks in over 1,000 hours of testing," the company stated.
Still, the company acknowledged that new attack techniques could emerge, which is why it implemented additional measures.
Anthropic officially presented Claude Fable 5, the first publicly accessible version based on its most advanced model, Mythos. The company aims to bring this technology to more users, although with specific restrictions in areas considered high risk.
The launch comes at a key moment for the company, which is preparing for a future IPO and continues to expand its presence in the artificial intelligence market.
Anthropic officially introduced Claude Fable 5
What is Claude Fable 5 and why is it important for Anthropic
Claude Fable 5 is the first general-use version of the Mythos model, which until now was limited to strategic partners and organizations linked to critical infrastructure.
According to Anthropic, the model excels in tasks related to programming, information analysis, professional work, and visual comprehension.
However, the company decided to incorporate security barriers. When users make inquiries related to cybersecurity, biology, chemistry, or distillation processes, the system blocks certain responses and redirects the interaction to Claude Opus 4.8.
What is Claude Fable 5 and why is it important for Anthropic
How access to Claude Fable 5 will work
The new artificial intelligence is already available through the Claude API and business plans with measured consumption.
Additionally, until June 22, Fable 5 will be included at no additional cost in the Pro, Max, Team, and Enterprise per user plans.
Starting from June 23, Anthropic will temporarily withdraw the included access and will require usage credits. The company assured that it plans to reintegrate it later as part of standard subscriptions.
Mythos 5 also arrives for selected organizations
Along with Fable 5, Anthropic announced a new version called Mythos 5.
This model will be available only to organizations that already have authorization to use the more advanced versions of the platform.
Mythos 5 also arrives at selected organizations
The company had begun to expand access to Mythos last week, incorporating hundreds of organizations across 15 countries.
Why Anthropic will retain data for 30 days
As part of the protection strategy, Anthropic established a mandatory data retention policy of 30 days for those using Fable 5 and Mythos 5.
Why Anthropic will retain data for 30 days
The measure will also apply to corporate clients who previously had zero retention agreements.
According to the company, the information will not be used to train models but to detect complex attacks, new jailbreak attempts, and reduce false positives in security systems.
The information will not be used to train models, but to detect complex attacks
What performance Claude Fable 5 showed in the initial tests
Anthropic stated that more than 95% of the test sessions operate completely with responses generated by Fable 5, without needing to resort to Opus 4.8.
The analysis firm Hex reported that the model was the first to reach 90% in its benchmark for complex analytical tasks.
For its part, the platform Base44 highlighted its ability to create complete applications in a single interaction, while Genspark noted superior results in interface design and video game programming.
What performance did Claude Fable 5 show in the initial tests
How much does it cost to use Claude Fable 5
Anthropic set the price for Fable 5 and Mythos 5 at US$ 10 per million input tokens and US$ 50 per million output tokens.
The fee doubles the cost of Claude Opus 4.8 and could become a barrier to mass adoption, especially among companies looking to reduce expenses related to artificial intelligence.
How much does it cost to use Claude Fable 5
Still, some companies believe that the additional performance justifies the investment. From Rakuten, they highlighted that the model can review and validate its own work, a capability they consider key for increasingly autonomous operations.
