Anthropic released Claude Sonnet 5.5 on September 28, 2026. The mid-range model targets routine work such as coding and creating office documents. Anthropic says it should cost significantly less to run than Sonnet 5 and consume tokens at a slower rate. Sonnet 5 was announced on June 30, 2026 for lower-cost agentic deployments.

The company reports that Sonnet 5.5 responds 30% faster than Sonnet 5. In Anthropic’s benchmarks, it outperformed Opus 5.5 on agentic coding. Anthropic links that result to Sonnet 5.5’s ability to launch multiple agents while staying within cost limits. Sonnet remains below Opus in the model hierarchy, although its agility can make it more useful for some workloads.

Anthropic also says Sonnet 5.5 has cyber capabilities comparable to Opus 5. The model will therefore receive the same cyber safeguards that apply to Fable and Opus. Anthropic plans to release a new version of Haiku, its smallest model, in the coming weeks, but has not set a date. The launch follows OpenAI’s September 22 release of enhanced Sol and Luna models, plus Meta’s September 23 announcement of a model for an upcoming smart-glasses feature.