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Claude Sonnet 4.5 is probably the “best coding model in the world” (at least for now)

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Claude Sonnet 4.5 is the best coding model in the world. It’s the strongest model for building complex agents. It’s the best model at using computers. And it shows substantial gains in reasoning and math. Anthropic gave me access to a preview version of a “new model” over the weekend which turned out to be Sonnet 4.5. My initial impressions were that it felt like a better model for code than GPT-5-Codex, which has been my preferred coding model since it launched a few weeks ago. This space moves so fast—Gemini 3 is rumored to land soon so who knows how long Sonnet 4.5 will continue to hold the “best coding model” crown. The pricing is the same as the previous Sonnet: $3/million input tokens and $15/million output tokens. This remains significantly cheaper than Claude Opus—$15/$75—but still quite a bit more than GPT-5 and GPT-5-Codex, both at $1.25/$10. The claude.ai web interface (not yet the Claude iPhone native app) recently added the ability for Claude to write and then directly exe

Claude Sonnet 4.5 is probably the “best coding model in the world” (at least for now) Simon Willison’s Weblog Subscribe Sponsored by: Microsoft - Agent projects stall between demo and production. Microsoft's MVP checklist closes that gap. Try it Claude Sonnet 4.5 is probably the “best coding model in the world” (at least for now) 29th September 2025 Anthropic released Claude Sonnet 4.5 today , with a very bold set of claims: Claude Sonnet 4.5 is the best coding model in the world. It’s the strongest model for building complex agents. It’s the best model at using computers. And it shows substan

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