Inside Claude Code's Hidden Multi-Agent Architecture

Anthropic's Claude Code has 58 tools, but the one that matters most is the one that spawns copies of itself. On March 31, the full source leaked via npm source maps. I spent the last two days reading the multi-agent architecture. Here is what I found. AgentTool: The Tool That Spawns Agents Every subagent in Claude Code is created through a single tool. The input schema tells you everything about how Anthropic thinks about agent orchestration: const baseInputSchema = z. object ({ description: z. string. describe ( ' A short (3-5 word) description ' ), prompt: z.