Claude Sonnet 4.5 (20250929)

Claude Sonnet 4.5 is positioned by Anthropic as its most intelligent model at launch, with a particular emphasis on coding tasks and complex agent workflows, and it became available through Amazon Bedrock on the same day as its wider release. Independent commentary shortly after release described it as a step forward in agent-oriented reasoning, suggesting practical strengths in multi-step planning, tool orchestration, and sustained software engineering tasks where careful instruction following matters more than raw single-turn generation. This framing aligns with its placement in the mid-tier Sonnet family, aiming to balance capability and cost for production workloads.

In practical terms, Claude Sonnet 4.5 is best suited for teams building agentic systems, code-generation pipelines, and document- or image-grounded assistants that benefit from extended context and reasoning over attached files. Its combination of reasoning, tool calling, temperature control, and multimodal input handling makes it a flexible default for complex automation, while remaining lighter than flagship-tier alternatives. Developers should expect the strongest gains on multi-step coding, refactoring, and agent loops where planning and reliable tool use are central to the workflow.