Anthropic has shipped Claude Opus 4, the flagship model in its Claude lineup, and it represents a significant leap in capability. The headline feature is a 1 million token context window combined with extended thinking - a chain-of-thought mechanism that lets the model reason through complex problems step by step before producing a final answer. In practice, this means you can feed it an entire codebase and ask for architectural analysis, or drop in hundreds of pages of documentation and get accurate, sourced answers.
For developers, the improvements to code generation and debugging are substantial. Opus 4 handles multi-file refactors, understands project structure across dozens of files simultaneously, and produces noticeably fewer hallucinations when working with unfamiliar libraries. The model also powers Claude Code, Anthropic's agentic coding tool, which can now handle more complex tasks like full feature implementation across multiple files.
Pricing sits at $15 per million input tokens and $75 per million output tokens - expensive, but competitive with GPT-4o for comparable capability. For founders building AI-powered products, the extended context window opens up use cases that were previously impractical, from analyzing entire customer support histories to processing complete financial reports in one shot.
If you are building anything that requires processing large documents or complex reasoning, Opus 4 is worth testing against your current model.
