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Claude Code is Anthropic’s production-grade AI coding assistant. It embeds a streaming agentic loop powered by Claude, capable of reading files, executing shell commands, searching the web, spawning sub-agents, and managing long-running tasks — all within your terminal. This documentation covers the source code extracted from the @anthropic-ai/claude-code npm package v2.1.88, providing an in-depth reference for the architecture, tools, commands, and internal systems.

Quick Start

Get Claude Code running in minutes with authentication and your first query.

Installation

Install options: npm global, run pre-built CLI, or build from source.

Core Concepts

Understand the agent loop, tool system, permission model, and context management.

Architecture

Deep dive into the query engine, multi-agent system, MCP integration, and persistence.

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Explore the reference

Built-in Tools

40+ tools for file operations, search, execution, agents, and MCP protocol.

Slash Commands

80+ slash commands for session management, configuration, and workflow control.

Configuration

Settings, environment variables, hooks, and the CLAUDE.md memory system.

Analysis Reports

Research findings: telemetry, hidden features, remote control, and roadmap.

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Key capabilities

1

Agentic loop

Claude Code runs a continuous loop: send a prompt to Claude, receive a response, execute any requested tools, append results, and loop back — until Claude stops requesting tool calls.
2

Permission system

Every tool call passes through a layered permission system: pre-tool hooks, always-allow/deny rules, and interactive prompts. Configure permissions via settings.json or CLI flags.
3

Multi-agent orchestration

Spawn sub-agents via AgentTool in fork, worktree, or in-process mode. Coordinate teams of agents sharing a task board and message inbox using TeamCreateTool and SendMessageTool.
4

MCP integration

Connect to any Model Context Protocol server (stdio, SSE, HTTP, WebSocket) to extend Claude Code with custom tools and resources using the standard MCP protocol.
This repository contains decompiled source code for technical research and educational purposes. All source code is copyright Anthropic. Commercial use is prohibited.