Anthropic releases Opus 5.5, cutting prices and citing Fable-level results

Opus is the most capable and expensive tier in Anthropic’s three-tier Claude lineup, with Sonnet in the middle and Haiku the fastest and cheapest. Anthropic says Opus 5.5 outpaces the larger Fable model on many benchmarks and succeeded at a number of informal tasks Fable failed to complete. The new model is also faster to run, which the company says reflects an overall drop in the compute required to serve it. Beyond pricing, Opus 5.5 changes how the model communicates: Anthropic says it is 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 Opus 5’s release on July 24. According to Anthropic’s announcement, Sonnet 5.5 and Haiku 5.5 — the next tiers in the lineup — will follow “in the coming weeks,” with similar performance improvements. Anthropic says Opus 5.5 is comparable to its Mythos model in biology and cybersecurity capabilities, so it is subject to the same safeguards as Fable, limiting how much the model can be used to discover exploits in compiled programs or help develop recognizable biological weapons, among other restrictions.

Opus 5.5 is Anthropic’s first model release since CEO Dario Amodei embraced calls to pace the frontier — deliberately slowing capability progress to let alignment work keep up. “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.” Anthropic says Opus 5.5’s safety training was broadly similar to its predecessors, including alignment testing and pre-release evaluation by outside organizations like METR and Frontier Design, though it said more advanced training and evaluation systems — including improved security and monitoring — are already being prepared for future models. “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 company’s blog post reads. “We expect to share more details on these efforts soon.”

Why it matters

A price cut alongside a capability claim signals Anthropic is competing on cost as well as performance, even as it publicly commits to a slower, more deliberate release cadence.