Claude Sonnet 4.5
Hybrid reasoning model with superior intelligence for agents, and 200K context window
Announcements
- New
Claude Sonnet 4.5
Sep 29, 2025
Sonnet 4.5 is the best model in the world for agents, coding, and computer use. It’s also our most accurate and detailed model for long-running tasks, with enhanced domain knowledge in coding, finance, and cybersecurity.
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Claude Sonnet 4
Sonnet 4 improves on Sonnet 3.7 across a variety of areas, especially coding. It offers frontier performance that’s practical for most AI use cases, including user-facing AI assistants and high-volume tasks.
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Claude Sonnet 3.7 and Claude Code
Feb 24, 2025
Sonnet 3.7 is the first hybrid reasoning model and our most intelligent model to date. It’s state-of-the art for coding and delivers significant improvements in content generation, data analysis, and planning.
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Availability and pricing
Anyone can chat with Claude using Sonnet 4.5 on Claude.ai, available on web, iOS, and Android.
For developers interested in building agents, Sonnet 4.5 is available on the Claude Developer Platform natively, and in Amazon Bedrock and Google Cloud’s Vertex AI. You can also use Sonnet 4.5 to handle complex coding tasks with our industry-leading coding agent, Claude Code.
Pricing for Sonnet 4.5 starts at $3 per million input tokens and $15 per million output tokens, with up to 90% cost savings with prompt caching and 50% cost savings with batch processing. Learn more at our pricing page.
Use cases
Sonnet 4.5 is our most capable model for agents—and the best model in the world for coding and computer use.
Sonnet 4.5 can produce near-instant responses or extended, step-by-step thinking that is made visible to the user. API users also have fine-grained control over how long the model thinks. Popular use cases include:
Long-running agents
Sonnet 4.5 offers superior instruction following, tool selection, error correction, and advanced reasoning for customer-facing agents and complex AI workflows.
Code generation
Sonnet 4.5 is a powerful choice for agentic coding, and can complete tasks across the entire software development lifecycle, from initial planning to bug fixes, maintenance to large refactors. It offers strong performance in both planning and solving for complex coding tasks, making it an ideal choice to power end-to-end software development processes.
Sonnet 4.5 supports up to 64K output tokens, which is particularly valuable for rich code generation and planning.
Browser and computer use
Sonnet 4.5 leads in computer use capabilities, reliably handling any browser-based task from competitive analysis to procurement workflows to customer onboarding. Sonnet 3.5 was the first frontier AI model to be able to use computers in this way. Sonnet 4.5 uses computers even more accurately and reliably, and we expect the capability to improve over time.
Cybersecurity
Teams using Sonnet 4.5 with Claude Code can deploy agents that autonomously patch vulnerabilities before exploitation, shifting from reactive detection to proactive defense.
Financial analysis
Sonnet 4.5 handles everything from entry-level financial analysis to advanced predictive analysis. For example, it can continuously monitor global regulatory changes and preemptively adapt compliance systems, evolving beyond manual audit preparation to intelligent risk management.
Business tasks
Sonnet 4.5 excels at producing and editing office files like slides, documents, and spreadsheets.
Research
Sonnet 4.5 can search through external and internal data sources to synthesize comprehensive insights across complex information landscapes.
Content generation and analysis
Sonnet 4.5 excels at writing and can understand nuance and tone to generate more compelling content and analyze content on a deeper level.
Benchmarks
Sonnet 4.5 is our best coding model to date, advancing the frontier with 77.2% on SWE-bench Verified. It is also our best computer-using model, reaching 61.4% on OSWorld.
Sonnet 4.5 excels at powering agents for financial analysis, cybersecurity, and research—coordinating multiple agents and processing high volumes of data with the reliability these domains demand.
Trust & Safety
We’ve conducted extensive testing and evaluation of Sonnet 4.5, working with external experts to ensure it meets our standards for safety, security, and reliability. In the model card for this release, we discuss new safety results in several categories.
What customers are saying
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.
Claude Sonnet 4.5 amplifies GitHub Copilot's core strengths. Our initial evals show significant improvements in multi-step reasoning and code comprehension—enabling Copilot's agentic experiences to handle complex, codebase-spanning tasks better. We expect these gains to deliver meaningful value to developers moving from idea to implementation with confidence.
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.
For Devin, Claude Sonnet 4.5 increased planning performance by 18% and end-to-end eval scores by 12%—the biggest jump we've seen since the release of Claude Sonnet 3.6. It excels at testing its own code, enabling Devin to run longer, handle harder tasks, and deliver production-ready code more consistently.
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.
Claude Sonnet 4.5's edit capabilities are exceptional — we went from 9% error rate on Sonnet 4 to 0% on our internal code editing benchmark. Higher tool success at lower cost is a major leap for agentic coding. Claude Sonnet 4.5 balances creativity and control perfectly, thoroughly completing tasks without over-engineering.
For complex financial analysis—risk, structured products, portfolio screening—Claude Sonnet 4.5 with thinking delivers investment-grade insights that require less human review. When depth matters more than speed, it's a meaningful step forward for institutional finance.
Claude Sonnet 4.5 delivers measurable improvements for Next.js tasks. It is particularly good at building and linting Next.js code, showing up to a 17% improvement over its predecessor. We're excited to integrate it into v0 and AI Gateway at launch, giving developers instant access to these advances.
Sonnet 4.5 is state-of-the-art for real-world, agentic enterprise workflows. We've seen a leap in reasoning capabilities within Snowflake Intelligence—enabling customers to extract deeper, more actionable insights from their data.
Claude Sonnet 4.5 resets our expectations—it handles 30+ hours of autonomous coding, freeing our engineers to tackle months of complex architectural work in dramatically less time while maintaining coherence across massive codebases.
Claude Sonnet 4.5 delivers clear wins over Sonnet 4: sharper instruction-following, stronger planning, smarter parallelization. Tasks require fewer iterations, which is critical for our most demanding agentic workflows.
Claude Sonnet 4.5 shows strong promise for red teaming, generating creative attack scenarios that accelerate how we study attacker tradecraft. These insights strengthen our defenses across endpoints, identity, cloud, data, SaaS, and AI workloads.
Claude Sonnet 4.5 is excellent at software development tasks, learning our codebase patterns to deliver precise implementations. It handles everything from debugging to architecture with deep contextual understanding, transforming our development velocity.
See Claude in action
Coding
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Writing
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Students
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Frequently asked questions
We offer different models across the spectrum of speed, price, and performance. Sonnet 4.5 delivers superior intelligence with optimal efficiency for high-volume use cases. We recommend Sonnet 4.5 for most AI applications where you need a balance of advanced capabilities and practical throughput—such as customer-facing agents, production coding workflows, content generation at scale, and real-time research tasks.
Pricing depends on how you want to use Sonnet 4.5. To learn more, check out our pricing page.
Sonnet 4.5 is both a standard model and a hybrid reasoning model in one: you can pick when you want the model to answer normally and when you want it to use extended thinking.
Extended thinking mode is best when performance and accuracy matter more than latency. It significantly improves response quality for complex reasoning tasks, extended agentic work, multi-step coding projects, and deep research. Thinking summaries help you understand key aspects of the model's reasoning process.