Claude Code Analysis

Deep dive into the internals of @anthropic-ai/claude-code v2.1.88

Source extracted from cli.js.map of the npm package. TypeScript, Ink-based terminal UI, codename Tengu.

Lines of Code

512K

3x Linux 1.0 kernel

Source Files

1,884

.ts and .tsx files

Slash Commands

101

From /compact to /stickers

Built-in Tools

Bash, Edit, Agent, MCP...

Core Execution Loop

User InputPrompt + attachments

API StreamText + tool_use blocks

Tool ExecutionRead=parallel, Write=serial

Permission Check5-layer security gate

Loop until no more tool calls or exit condition

Fun Facts Highlights

See all 20+ →

🐧Fast Mode = Penguin Mode

Internal codename. Variables: penguinModeOrgEnabled, tengu_penguins_off

😤Frustration Detector

Regex detects 'wtf', 'ffs', 'this sucks' → triggers feedback survey

🐉18 Collectible Buddy Pets

Rarity tiers (1% legendary), hats, 5 stats including CHAOS and SNARK

💤Auto-Dream: Claude Sleeps

Background memory consolidation fires after 24h + 5 sessions. It runs /dream.

Explore

System Design

High-level system design, directory map, and how all pieces fit together

Query Loop

The core agentic cycle: message → API → tool calls → results → repeat

Tools

43 built-in tools — Bash, FileEdit, Agent, MCP, and more

Permissions

5-layer security with an ML classifier called 'yoloClassifier'

Agents

Subagent spawning, zero-cost cache sharing, worktree isolation

Services

Compaction, MCP (470KB!), LSP, analytics, memory extraction

Context & Memory

System prompt construction, CLAUDE.md, auto-memory system

File Map

Complete directory structure with key files and their purposes

Fun Facts

Easter eggs, buddy pets, the yoloClassifier, wizard comments

Streaming Tool Execution

Tools start executing while the model is still generating. StreamingToolExecutor queues tool_use blocks as they arrive.

Zero-Cost Cache Sharing

CacheSafeParams frozen at fork time. Identical system prompt bytes = automatic prompt cache hit for subagents.

Multi-Level Compaction

4 strategies (micro, auto, snip, collapse) keep conversations within token limits. Unlimited session length.