Anthropic releases Opus 5.5 with lower prices and Fable-level performance

Anthropic has released Opus 5.5, describing it as “the strongest-performing model we’ve tested to date.” The company says the model sets a new state of the art in coding and knowledge work, outperforming the larger Fable model in many benchmarks and completing some informal tasks that Fable failed.

Opus 5.5 is also cheaper and faster than Opus 5. Output tokens cost $20 per mTok, compared with $25 for the previous model, while other metrics have seen similar price reductions. Anthropic said the lower computing requirements contribute to faster operation.

The model is less likely to use jargon and more likely to place important information at the beginning of its messages. The release came two months after Opus 5 launched on July 24. Anthropic said Sonnet 5.5 and Haiku 5.5 will arrive “in the coming weeks” with similar performance improvements.

Anthropic also said Opus 5.5 is comparable to Mythos in biology and cybersecurity capabilities, so it has the same safeguards as Fable. The company said those safeguards restrict certain high-risk uses. Safety work included alignment testing and pre-release evaluation by METR and Frontier Design, while Anthropic is preparing more advanced training, security, and monitoring systems for future models.