Anthropic, a leader in advanced AI research and development, has announced the release of Claude Sonnet 4.5, its most powerful and aligned AI model to date. Building upon the foundation of previous Claude models, Sonnet 4.5 introduces significant advancements in coding, reasoning, and agent-building capabilities, setting a new standard for enterprise AI applications.
Enhanced Performance and Autonomy
Claude Sonnet 4.5 has achieved top-tier performance on the SWE-bench Verified evaluation, a benchmark assessing real-world software development skills. The model demonstrates exceptional focus and efficiency, maintaining sustained performance on complex, multi-step tasks for over 30 hours an improvement over its predecessor, Opus 4.1, which could operate autonomously for only seven hours.
In addition to its coding prowess, Sonnet 4.5 excels in operating-system-related tasks, achieving a 61.4% score on the OSWorld benchmark, up from 42.2% in the previous version. These enhancements are complemented by the Claude for Chrome extension, enabling users to interact directly with web applications, navigate websites, and complete tasks seamlessly.
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Advancements in Reasoning and Domain Expertise
Sonnet 4.5 exhibits substantial gains in reasoning and mathematical capabilities, outperforming earlier models in various evaluations. Experts across finance, law, medicine, and STEM fields have noted significant improvements in domain-specific knowledge and reasoning, making Sonnet 4.5 a valuable tool for professionals in these sectors.
Customer Success Stories
Early adopters of Claude Sonnet 4.5 have reported transformative impacts on their operations:
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Cursor: “We’re seeing state-of-the-art coding performance from Claude Sonnet 4.5, with significant improvements on longer horizon tasks. It reinforces why many developers using Cursor choose Claude for solving their most complex problems.”
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GitHub Copilot: “Claude Sonnet 4.5 amplifies GitHub Copilot’s core strengths. Our initial evaluations show significant improvements in multi-step reasoning and code comprehension enabling Copilot’s agentic experiences to handle complex, codebase-spanning tasks better.”
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Hai Security: “Claude Sonnet 4.5 reduced average vulnerability intake time for our Hai security agents by 44% while improving accuracy by 25%, helping us reduce risk for businesses with confidence.”
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CoCounsel: “Claude Sonnet 4.5 is state of the art on the most complex litigation tasks. For example, analyzing full briefing cycles and conducting research to synthesize excellent first drafts of an opinion for judges, or interrogating entire litigation records to create detailed summary judgment analysis.”
Commitment to Safety and Alignment
As part of its dedication to responsible AI development, Anthropic has implemented extensive safety training in Claude Sonnet 4.5, resulting in substantial improvements in model behavior. The model demonstrates reduced tendencies toward sycophancy, deception, power-seeking, and the encouragement of delusional thinking. These enhancements are supported by the introduction of the Claude Agent SDK, providing developers with the tools to build long-running agents capable of processing extensive codebases and analyzing large volumes of documents.