Tech Radar, April 27, 2026: Claude Sonnet 4.5 and the Agent SDK — The Best Coding Model Just Open-Sourced Its Infrastructure
Anthropic shipped two things this week that reframe how engineering teams will build AI agents. First, Claude Sonnet 4.5 — explicitly labeled “the best coding model in the world” — with substantial gains in reasoning, math, and computer use. Second, and more consequentially for platform teams, they open-sourced the Claude Agent SDK: the actual infrastructure that powers their frontier products. This is not an incremental model update. It is a strategic move to own the infrastructure layer of the emerging agent ecosystem, positioning Anthropic as both the model provider and the toolchain standard for complex agentic systems. ...