AI model wars: Anthropic extends Fable access again after OpenAI’s Sol release

Anthropic extended access to its Claude Fable 5 AI model for subscribers through July 19, the second such extension in a week, following OpenAI's launch of GPT-5.6 with its Sol model. The move escalates the rivalry between the two AI firms, with Anthropic also planning broader release of its restricted Mythos model.

Anthropic extended access for Claude Fable 5 for subscribers for the second time in a week, an apparent response to the launch of OpenAI’s latest ChatGPT model—which the rival firm claims sets a “new standard”—following Fable’s turbulent debut overshadowed by its clash with the U.S. government. Key Facts - Anthropic, its decision Sunday on X, through an email to subscribers and an updated announcing , said Claude Fable 5 would be available to subscribers at no extra cost through July 19. support page - That marks the second time Anthropic has expanded access to Fable after a one-week promotion on July 7, allowing Claude users to spend up to 50% of their weekly subscription limits on the model. launching - Even if users exhaust their expanded Fable access, they can still use the model by purchasing usage credits, which allow Claude subscribers to pay based on how much they use, Anthropic said. - The extension comes just three days after OpenAI GPT-5.6, headlined by its flagship model Sol, which the company said achieved “state-of-the-art” results in coding, knowledge work, cybersecurity and science while “outperforming previous and competing frontier models” at a lower cost. launched - OpenAI claimed Sol and its other new models outperformed Anthropic’s Fable in coding tasks and that its rival’s model failed to test for questions involving scientific research Anthropic Fable would “fall back” to a previous model for most biology and chemistry requests . said Will Anthropic make Mythos publicly available? Anthropic has said it plans to open up Mythos—its restricted flagship AI model, from which Fable is made with additional safety guardrails—“more broadly in the future,” though access is currently limited to roughly 150 organizations across more than 15 countries. Mythos was released last month to a “small number” of partners for use in defensive cybersecurity, Anthropic said, indicating its latest version could be used to “find and exploit software vulnerabilities more effectively than any other model—and all but the most skilled human security experts.” Anthropic’s rivalry with OpenAI Competition between Anthropic and OpenAI has become increasingly public in recent months. Anthropic CEO Dario Amodei, who spent nearly five years at OpenAI before leaving to co-found Anthropic in 2021, appeared https://www.youtube.com/watch?v=x2VHFgyawPE to say last month he departed the company over his distrust of OpenAI CEO Sam Altman: “At the end of the day, why argue with someone when you don’t have the same vision and you don’t trust them?” That came months after Altman Anthropic for running an ad during the Super Bowl, accusing the rival firm of being “so clearly dishonest” and calling it “authoritarian,” arguing OpenAI had no intention of serving ads in the way Anthropic portrayed. https://x.com/sama/status/2019139174339928189?lang=en criticized Key background Anthropic debuted Fable in early June as a restricted variant of its more powerful Mythos model. The company noted Fable included safety features that blocked users from inquiring about cybersecurity, as well as biology and chemistry needed to create bioweapons. The Commerce Department forced Anthropic to pull the model days later, however, and the AI firm disclosed the government “became aware” of a report from researchers at Amazon who were able to bypass Fable’s safety mechanisms. Researchers were able to get Fable to “demonstrate” how a software security vulnerability could be exploited, according to Anthropic, which noted the technique used by the researchers was now “blocked in over 99% of cases.” Anthropic has been at odds with the Trump administration for months, after the Pentagon designated the firm a supply chain risk in March following a spat between officials and Anthropic, which refused to allow the government unrestricted access to its models. This story was originally published on forbes.com and all figures are in USD. Want to see more Forbes articles on your feed? Tap here to make Forbes Australia a preferred source on Google. Look back on the week that was with hand-picked articles from Australia and around the world. Sign up to the Forbes Australia newsletter here or become a member here .