Claude Code, Anthropic’s flagship terminal-based coding agent, started as an interactive tool for writing software. But as we iterated on it, we discovered something more fundamental: an extensible infrastructure for building multi-agent applications with ease. Teams at Anthropic are already leveraging Claude Code to build code review systems, issue triaging pipelines, and more – with greater intellectual depth than ever before.

The key to building effective multi-agent systems is understanding the agent loop underpinning both the terminal UI and the SDK. We’ll build intuition for this foundational concept, then explore Claude Code’s various primitives that extend the loop: custom agents for delegation, skills for providing knowledge for Claude to look up, and hooks for injecting logic at decision points.

We’ll examine how these primitives enable the real systems mentioned above, and how Claude Code’s evolution into the Claude Agent SDK enables attendees to build their own multi-agent development workflows.