Claude Sonnet 4.5

January 9, 2026

TL;DR

Sonnet 4.5 is a hybrid reasoning model designed for agents, coding, and computer use, offering superior intelligence and accuracy.
It shows significant improvements over previous versions, particularly in coding, content generation, data analysis, and planning.
The model supports up to 64K output tokens and excels in various use cases including long-running agents, code generation, cybersecurity, financial analysis, research, and content creation.
Sonnet 4.5 offers near-instant responses or visible extended, step-by-step thinking, allowing fine-grained control over the model's thinking process.
It is available for general use on Claude.ai and for developers via the Claude Developer Platform, Amazon Bedrock, Google Cloud's Vertex AI, and Microsoft Foundry.
Pricing starts at $3 per million input tokens and $15 per million output tokens, with potential cost savings through prompt caching and batch processing.
Extensive testing and evaluation have been conducted to ensure safety, security, and reliability, with specific mention of improved performance in areas like vulnerability patching, code editing accuracy, and autonomous coding.
Sonnet 4.5 is recommended for AI applications needing a balance of advanced capabilities and practical throughput, such as customer-facing agents and production coding workflows.
Extended thinking mode is available for tasks where performance and accuracy are more critical than latency, enhancing response quality for complex reasoning and research.

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