Anthropic launches derivative version of Mythos model with Claude Fable 5
Anthropic has introduced Claude Fable 5, giving the general public access for the first time to technology derived from the powerful Mythos model. Although the model demonstrates superior capabilities in image processing, professional knowledge work and software development, it is being launched with strict safety protocols.
To prevent misuse in sensitive sectors such as chemistry, biology and cybersecurity, the system is programmed to reject high‑risk requests and instead direct users to Claude Opus 4.8.
The rollout is proceeding cautiously. Mythos was first shown in April to a small group of partners and later expanded to several hundred infrastructure‑focused organisations worldwide. Fable 5 is currently accessible via usage‑based Enterprise subscriptions and the Claude API. For users with Pro, Max, Team and licence‑based Enterprise subscriptions, the model is free until 22 June.
From 23 June, users on these subscriptions will have to use credits to access Fable 5, until the company can once again integrate it as a standard subscription feature. At the same time, an updated version, known as Mythos 5, is being distributed to previously authorised organisations.
This release comes as Anthropic prepares for a possible stock market listing and advocates a global, synchronised mechanism to slow the development of frontier AI. The company has expressed concern about recursive self‑improvement (RSI), in which AI systems could develop independently of human oversight. To mitigate these risks, Anthropic has subjected Fable 5 to rigorous red‑teaming and bug bounty programmes, which, after more than 1,000 hours of testing, have not revealed any universal jailbreaks.
Despite these safeguards, the possibility of new exploits has led Anthropic to introduce a mandatory 30‑day data‑retention policy for all traffic, setting aside previous contracts with zero retention. The company clarifies that this data will not be used for training, but is necessary to refine classifiers and thwart complex attacks. This move may herald a new trend in the sector, whereby access to top‑tier models requires agreeing to mandatory data storage for safety purposes.
Impressive performance
The performance statistics for Fable 5 are impressive. According to analytics firm Hex, the model is the first to achieve a score of 90% on a benchmark for long‑term analytical tasks, showing a high level of nuance.
Other players in the sector, such as Genspark and Base44, have praised its ability to create complete applications in a single pass and its superiority in game coding and UI design. Although most sessions (around 95%) remain within the Fable 5 framework without falling back to Opus 4.8, the costs are considerable.
At $10 per million input tokens and $50 per million output tokens, Fable 5 is twice as expensive as Opus 4.8. Since many companies are already struggling with rising AI expenditures, this price may limit adoption.
Business AM
Subscribers 0
Fans 0
Followers 0
Followers