Build Claude Code

Build an Enterprise AI Agent CLI from Scratch

49 progressive lessons that reverse-engineer Claude Code's architecture — from a single while loop to a production-grade product

Start Learning View all 49 lessons

agent.ts — The Core Pattern

while (true) {
  response = await client.messages.create({ messages, tools })
  if (response.stop_reason !== "tool_use") break
  for (const toolCall of response.content) {
    result = await executeTool(toolCall.name, toolCall.input)
    messages.push(result)
  }
}