Anthropic has unveiled Claude Sonnet 4.5, its most advanced AI model to date—described by the company as ‘the best coding model in the world’.
Released in September 2025, Sonnet 4.5 marks a significant evolution in agentic capability, safety alignment, and real-world task execution.
Designed to power Claude Code and enterprise-grade AI agents, Sonnet 4.5 excels in long-context coding, autonomous software development, and complex business workflows.
Benchmark
In benchmark trials, the model reportedly sustained 30+ hours of uninterrupted coding, outperforming its predecessor Opus 4.1 and rival systems like GPT-5 and Gemini 2.52.
Anthropic’s emphasis on safety is equally notable. Sonnet 4.5 underwent extensive alignment training to reduce sycophancy, deception, and prompt injection vulnerabilities.
It now operates under Anthropic’s AI Safety Level 3 framework, with filters guarding against misuse in sensitive domains such as chemical or biological research.
New features include ‘checkpoints’ for code rollback, file creation within chat (spreadsheets, slides, documents), and a refreshed terminal interface.
Developers can now build custom agents using the Claude Agent SDK, extending the model’s reach into autonomous task orchestration4.
Anthropic’s positioning is clear: Claude Sonnet 4.5 is not merely a chatbot—it’s a colleague. With pricing held at $3 per million input tokens and $15 per million output tokens, the model is accessible yet formidable.
As AI enters its ‘super cycle’, Claude Sonnet 4.5 signals a shift from conversational novelty to operational necessity.
Whether this heralds a renaissance or a reckoning remains to be seen—but for now, Anthropic’s latest release sets a new benchmark for intelligent autonomy.