Anthropic launched the Claude 4 generation with two models: the flagship Claude Opus 4 and the workhorse Claude Sonnet 4. Both were pitched as the best coding models in the world, capable of sustaining coherent work over multi-hour agentic sessions.

Opus 4 introduced the ability to use tools in parallel and maintain focus across long-horizon tasks, while Sonnet 4 delivered most of that capability at a lower price. Anthropic framed the pair around agents that could work autonomously for extended periods.

Claude 4 reset the frontier in software engineering tasks and kicked off the rapid 4.x iteration cadence — 4.1, 4.5, 4.6, and 4.8 followed within a year.