Anthropic launches Claude Sonnet 4.5, its most powerful coding and agentic model.
Summary
Anthropic has announced the immediate availability of Claude Sonnet 4.5, a new frontier AI model positioned as a state-of-the-art tool for coding, building complex agents, and using computer applications. The launch is accompanied by significant upgrades across the Claude ecosystem, including new features in Claude Code, an enhanced API, and the release of the Claude Agent SDK for developers. The new model is available at the same price as its predecessor, Claude Sonnet 4, and is described as the company's most aligned and safe model to date.
Key Takeaways
* Product Name: Claude Sonnet 4.5.
* Primary Capabilities: State-of-the-art performance in coding (SWE-bench Verified), computer use (OSWorld benchmark), complex reasoning, and mathematics.
* New Developer Tool: The Claude Agent SDK has been released, allowing developers to build their own agents using the same infrastructure that powers Anthropic's Claude Code product.
* Product Updates:
* Claude Code: Adds "checkpoints" to save and revert progress, a refreshed terminal, and a native VS Code extension.
* Claude Apps: Now support in-conversation code execution and file creation (spreadsheets, slides, docs).
* API: Includes new context editing and memory tools for longer-running agents.
* Availability: Available immediately via the API (`claude-sonnet-4-5`).
* Pricing: Remains the same as Claude Sonnet 4, at $3/$15 per million input/output tokens.
* Safety & Alignment: Touted as Anthropic's "most aligned frontier model yet," with significant reductions in misaligned behaviors and improved defenses against prompt injection attacks.
Strategic Importance
This launch positions Anthropic as a direct competitor in the high-stakes agentic AI space, aiming to provide the foundational model and developer tools for building autonomous systems. By releasing the Agent SDK, Anthropic is empowering an ecosystem of developers, moving beyond being a model provider to becoming a platform for building next-generation AI applications.