Anthropic releases Opus 5.5 with lower prices and Fable-level performance
Anthropic released cheaper, faster Claude Opus 5.5 and called it its strongest model.
Anthropic released Claude Opus 5.5 on Tuesday and called it the strongest model it has tested, saying it outpaces the larger Fable model on many coding and knowledge-work benchmarks. Output tokens cost $20 per million, compared with $25 for Opus 5, and Anthropic said the model is faster and needs less compute. The company says its biology and cybersecurity capabilities are comparable to Mythos, so Fable-level safeguards limit uses such as exploit discovery in compiled programs and assistance with biological weapons. Sonnet 5.5 and Haiku 5.5 are expected in the coming weeks, and METR and Frontier Design evaluated the release.
- Output tokens cost $20 per million, down from $25 for Opus 5.
- Anthropic calls Opus 5.5 its strongest model tested to date.
- It beat larger Fable on many coding and knowledge benchmarks.
- Biology and cybersecurity safeguards match those applied to Fable.
- Sonnet 5.5 and Haiku 5.5 are planned in the coming weeks.
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Anthropic’s newest model, Opus 5.5, was released on Tuesday, setting a new state-of-the-art in coding and knowledge work performance. Notably, the release outpaces the larger Fable model in many benchmarks, and succeeded in a number of informal tasks that Fable failed to complete.
In the announcement, Anthropic called it “the strongest-performing model we’ve tested to date.”
Opus 5.5 is also significantly cheaper than Opus 5. Output tokens will be charged at $20 per mTok, compared to $25 for the previous model, and other metrics have similar price drops. The model is also faster to run, reflecting an overall drop in the compute requirements.
The new version also makes significant changes to how Opus communicates, with the Opus 5.5 less likely to use jargon and more likely to put important information at the start of its messages.
The launch comes just two months after the release of Opus 5 on July 24th. According to the announcement, Sonnet 5.5 and Haiku 5.5 will be released “in the coming weeks,” with similar performance improvements.
Anthropic says that Opus 5.5 is comparable to Mythos in its biology and cybersecurity capabilities, so its release is subject to the same safeguards as the company’s Fable model. Those safeguards limit how much the models can be used to discover exploits in compiled programs or developing recognizable biological weapons, among other tasks.
Opus 5.5 is Anthropic’s first model release since CEO Dario Amodei embraced calls to pace the frontier, deliberately slowing down progress on AI capabilities to match the rate of progress on alignment.
“I have become convinced that fully addressing the risks requires even more prudence,” Amodei wrote in a post earlier this month, “not just investing in risk prevention, but pacing the rate of capabilities advancement so that risk prevention has time to keep up.”
Opus 5.5’s safety training was broadly similar to its predecessors, with alignment testing and pre-release evaluation by outside organizations like METR and Frontier Design. But Anthropic emphasized that more advanced training and evaluation systems were already being prepared for future models, including improved security and monitoring systems.
“As AI becomes more capable, public policy should play a larger role in making sure the systems people rely on are safe. That capacity takes time to build, and we’ve started to put the infrastructure in place to support it,” the blog post reads. “We expect to share more details on these efforts soon.”
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Russell Brandom has been covering the tech industry since 2012, with a focus on platform policy and emerging technologies. He previously worked at The Verge and Rest of World, and has written for Wired, The Awl and MIT’s Technology Review. He can be reached at russell.brandom@techcrunch.com or on Signal at 412-401-5489.