Claude Sonnet 5.5 has been introduced as a significant upgrade to Claude Sonnet 5, offering a 30%+ speed increase and up to 30% cost reduction for most tasks. This model is designed for everyday tasks, bug fixing, and creating polished documents, and is a faster and lower-cost complement to Claude Opus 5.5. Sonnet 5.5 shows improved performance, scoring 70.6% on Terminal-Bench 4.0 and performing well on long-horizon work and image understanding, making it a strong addition to the Claude 5.5 family, which will soon include Claude Haiku 5.5 for high-volume and cost-sensitive applications.