On Monday, Anthropic introduced Claude Sonnet 4.5, a new frontier AI model designed to push the boundaries of coding performance. The company claims the model can create “production-ready” applications, rather than just prototypes, marking a major step up in reliability from earlier versions.
Claude Sonnet 4.5 will be accessible via the Claude API and the Claude chatbot. Developer pricing remains unchanged from Claude Sonnet 4: $3 per million input tokens (about 750,000 words—over the length of the entire Lord of the Rings series) and $15 per million output tokens.
Over the past year, Anthropic’s AI models have gained traction among developers and enterprises for their strength in software engineering tasks. Companies like Apple and Meta reportedly use Claude AI internally, while API partnerships with platforms like Cursor, Windsurf, and Replit have expanded its commercial footprint. Still, competition is heating up: OpenAI’s GPT-5 has recently challenged Claude models, outperforming them on several coding benchmarks.
Anthropic says Claude Sonnet 4.5 delivers industry-leading results on benchmarks like SWE-Bench Verified, but AI researcher David Hershey cautions that benchmark scores alone don’t capture the model’s full capabilities. During early trials, Hershey observed the AI autonomously coding for up to 30 hours, managing tasks such as building applications, setting up databases, purchasing domain names, and even completing a SOC 2 security audit.
Industry insiders are taking notice. Cursor CEO Michael Truell praised Claude Sonnet 4.5 for its performance on longer-horizon coding tasks, while Windsurf CEO Jeff Wang called it a “new generation of coding models.”
Anthropic also emphasizes that Claude Sonnet 4.5 is its most aligned frontier AI yet, showing reduced tendencies for sycophancy and deception and improved resistance to prompt injection attacks.
Alongside the model launch, Anthropic is releasing the Claude Agent SDK, the same infrastructure behind Claude Code, enabling developers to build their own AI agents. A temporary research preview, “Imagine with Claude,” is available for Max subscribers, demonstrating real-time software generation without prewritten code.
The AI race remains intense, with flagship models emerging every few months. Claude Sonnet 4.5 arrives less than two months after Claude Opus 4.1, highlighting the rapid pace of innovation and the challenge for any company to maintain a long-term lead.
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