Comprehensive architectural analysis of the Claude Code codebase. Each section covers a distinct subsystem with its design decisions, key files, and interaction patterns.
| # | Section | Description |
|---|---|---|
| 00 | Overview | High-level architecture, technology stack, key design decisions, repository statistics |
| 01 | Entry Points & Bootstrap | CLI entry, initialization sequence, deferred prefetching, session lifecycle |
| 02 | Query Engine | Core execution pipeline, API integration, token budgeting, retry strategy |
| 03 | Tool System | Tool abstraction, 44 built-in tools, concurrency model, BashTool and AgentTool deep dives |
| 04 | Commands & Skills | 89 slash commands, skill system, loading pipeline, bundled skills |
| 05 | Permissions & Security | Permission model, security layers, hook-based enforcement, enterprise policies |
| 06 | Terminal Renderer | Custom React reconciler, flexbox layout engine, ANSI protocol, performance optimizations |
| 07 | MCP Integration | MCP client/server, 7 transports, authentication, tool normalization |
| 08 | Agent Coordination | Sub-agents, fork optimization, worktree isolation, multi-agent teams |
| 09 | State Management | AppState, session persistence, file caching, React context, memory system |
| 10 | Build System | esbuild pipeline, feature flags, MACRO constants, Docker, CI/CD |
| 11 | Web Frontend | Next.js app, browser terminal, collaboration, API routes |
| 12 | Configuration | Settings hierarchy, environment variables, hot-reloading, CLAUDE.md |
| 13 | Services & Integrations | API client, OAuth, LSP, telemetry, plugins, voice, bridge, monitoring |
Start here: 00-overview.md for the big picture.
Core runtime: Sections 01-03 cover the execution spine (bootstrap → query engine → tool execution).
Extension points: Sections 04, 07, 13 cover how to extend Claude Code (commands, skills, MCP, plugins).
Security model: Section 05 is essential for understanding how Claude Code manages trust and permissions.
UI internals: Section 06 covers the custom terminal renderer; Section 11 covers the web frontend.
Infrastructure: Sections 10, 12 cover build, configuration, and deployment.