Anthropic announced Claude Sonnet 5.5 on September 28 as the second model in its Claude 5.5 family, positioning it for coding, documents and other well-scoped work.
Reported speed and cost gains
Anthropic says Sonnet 5.5 runs over 30% faster and costs up to 30% less for most work than Sonnet 5. The company also reports 70.6% on Terminal-Bench 4.0 versus 10.3% for Sonnet 5; these are issuer measurements, not independent replication.
Reuters independently confirmed the release. Its reporting does not replicate Anthropic’s benchmarks; realized cost and performance depend on workload and settings.