Anthropic introduced Claude Sonnet 5.5 on September 28, 2026 as a faster and lower-cost model for everyday professional work. Anthropic says Sonnet 5.5 runs more than 30% faster than Sonnet 5 and costs up to 30% less for most work.
Positioning within Claude 5.5
Anthropic describes Sonnet 5.5 as a complement to Claude Opus 5.5. Sonnet is aimed at well-scoped everyday tasks, coding fixes, document creation, presentations, spreadsheets, and other work where users want strong capability without using the highest-cost model for every request.
Coding and long-horizon work
Anthropic reports a substantial improvement on Terminal-Bench 4.0, an agentic coding evaluation, with Sonnet 5.5 scoring 70.6% compared with 10.3% for Sonnet 5. The company also highlights long-horizon work and image understanding.
Benchmark numbers are vendor-reported measurements and should not be treated as a guarantee of performance in a particular application. Teams should test the model using their own codebases, documents, and tool workflows.
Cost and speed
Faster generation can matter as much as raw benchmark performance in interactive products. Lower per-task cost also makes it more practical to use capable models repeatedly inside coding assistants and agent workflows.
Everyday professional workloads
Anthropic specifically points to polished documents, slides, and spreadsheets alongside bug fixing and ordinary knowledge work. This makes Sonnet 5.5 relevant to applications that combine reasoning with file creation or editing rather than pure chat.
Practical takeaway: Organizations choosing between AI models should evaluate total task cost and completion time, not only model quality. Sonnet 5.5 is designed for the middle ground between high-end reasoning and high-volume everyday work.
Source: Anthropic — Claude Sonnet 5.5