Anthropic
Anthropic ships Claude Sonnet 5.5
On Sept. 28, 2026, Anthropic introduced Claude Sonnet 5.5, the second model in the Claude 5.5 family. The company says it runs more than 30 percent faster than Claude Sonnet 5 and typically costs up to 30 percent less per task at the same list price — $2 per million input tokens and $10 per million output tokens. On Terminal-Bench 4.0, an agentic coding test, Anthropic reports 70.6 percent for Sonnet 5.5 versus 10.3 percent for Sonnet 5. It is the first Sonnet model to launch with cyber safeguards and fallbacks like those on Claude Opus. The model ID is claude-sonnet-5-5. It is available on the Claude Platform and through Amazon Web Services, Google Cloud, and Microsoft Azure. Anthropic says Claude Haiku 5.5 will join the family in the coming weeks. The system card says Responsible Scaling Policy evaluations found Sonnet 5.5 broadly less capable than Opus 5.5 and that it does not cross any new Responsible Scaling Policy thresholds.
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