Anthropic Previews Claude Sonnet 5.5 and Haiku 5.5 for the Coming Weeks

On September 22, Anthropic announced the upcoming release of Claude Sonnet 5.5 and Claude Haiku 5.5, saying the new models will bring similar improvements in performance, efficiency, and safety. The announcement came alongside the launch of Claude Opus 5.5.

Claude Opus 5.5 is the first model Anthropic has released since the company called for a slower pace in frontier AI development. According to Anthropic, it matches Claude Fable 5.1 on most tasks while cutting typical operating costs by 40% compared with Opus 5. The model is priced at $4 per million input tokens and $20 per million output tokens, a 20% reduction in both rates from Opus 5. Anthropic also said that before release, the model was tested by external evaluators including Frontier Design and METR, and includes safety measures such as a pre-execution classifier and an open-source sandbox.

The same day, OpenAI released GPT-6 Sol and GPT-6 Luna, cutting API prices by 50% compared with the promotional pricing of the previous-generation GPT-5.6 models. The parallel releases highlight the continued competition between the two AI companies as safety debates continue.