LONG-CONTEXT

Andrej Karpathy gave Opus 5 the first paragraph of the Lord of the Rings, a 1M-token budget (about $10), and asked for a three.js render. Two hours and 5,500 lines of code later, the model had procedurally built a 3D world - and exposed a real weakness in how agents verify their own work.

Anthropic's flagship reasoning model. Best-in-class for coding, long-context analysis, and agentic workflows. 1M token context window. Available via API and in Claude Code.