Anthropic’s most capable generative AI model is still in the hands of a select few organizations and cybersecurity professionals, but the most powerful Claude model you can use now is getting an upgrade.

Claude Opus 4.8, released Thursday, is a “modest but tangible improvement” over Opus 4.7, Anthropic said in a blog post. 

But the company also said it’s making significant progress on producing a version of its Claude Mythos Preview model that it’s willing to release to the public. Right now, it has restricted access to Mythos to a consortium of partners as part of what it calls Project Glasswing, explaining that the model’s cybersecurity capabilities are advanced enough to warrant giving cybersecurity experts and major tech companies some lead time to patch flaws found by the model.

“Models of this capability level require stronger cyber safeguards before they can be generally released,” Anthropic said. “We’re making swift progress on developing these safeguards and expect to be able to bring Mythos-class models to all our customers in the coming weeks.”

Mythos for everyone?

Anthropic’s decision to withhold Mythos Preview from the general public, at least for now, has been an interesting one. Was it a wise, forward-thinking move to protect the internet’s critical infrastructure from potential flaws? Was it an easy way to churn up marketing hype? Security researchers have found that the model is certainly capable of finding exploits much more quickly than human hackers, even if it isn’t necessarily pushing beyond human capabilities. Mozilla’s latest version of Firefox included more than 200 fixes identified by Mythos Preview.

Read more: AI Arms Race Accelerates With New Models from OpenAI, DeepSeek and Anthropic

But the fact that Mythos will soon be available to anyone, even with significant cybersecurity guardrails, means we’ll finally get to see if the model lives up to the hype, with all the risks that might entail.

Darren Williams, founder and CEO of the cybersecurity firm BlackFog, told CNET in an email that big model releases are often tense moments.

“On one hand, Anthropic’s decision to stage the release, holding back until safeguards are developed, shows the right instincts,” he said. “But the more capable a model is, the higher the stakes if those safeguards fall short or if the model is eventually misused. The window between a powerful model’s release and broad adoption of defenses against it is always a vulnerable moment.”

Mythos is going to be far more expensive to run than other AI models, however, and that could limit its usefulness to hackers. Jake Williams, a cybersecurity researcher and faculty member at IANS Research, said Mythos was 30 times as expensive in tests as the previous Opus model.

“This is outside the reach of many, including any commodity threat actors,” Williams told CNET in an email. “Nation-state actors already had better technology for finding vulnerabilities. This is only changing the game for a small percentage of threat actors.”

What’s new about Claude Opus 4.8

As for Opus 4.8, Anthropic said it’s an improvement across benchmarks compared to Opus 4.7. Tests found that Opus 4.8 was less likely to make unsupported claims and more likely to indicate uncertainty, the company said.

A few new features are also coming to Anthropic’s AI products, including the ability to control how much “effort” a model will use to respond to a prompt on Claude.ai and in Claude Cowork. Higher effort will likely get better results as the model spends more time on a response, but it will burn through your usage limits faster. A lower setting will respond faster and hit rate limits more slowly.