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Claude Code
v2.1.88
@anthropic-ai/claude-code v2.1.88
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Claude Code Analysis

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

The most complex CLI tool ever shipped — decoded.

What you'll discover
🦆
A duck lives inside Claude Code

Easter egg in the buddy pet system — 18 collectible companions with rarity tiers.

→ See fun facts
🤖
ML classifier named yoloClassifier

Real production security code. It gates whether dangerous shell commands need permission.

→ See permissions
🐧
Fast Mode = Penguin Mode internally

Variable name: penguinModeOrgEnabled. Penguin Mode disables extended thinking.

→ See fun facts
Repoquery.tsTool.tsservices/tools/
Lines of Code
0
3× Linux 1.0 kernel
Source Files
0
.ts and .tsx files
Slash Commands
0
From /compact to /stickers
Built-in Tools
0
Bash, Edit, Agent, MCP...
Start here: Architecture →Deep dive: Query Loop

How to Read This Site

🚀
Quick Tour30 min4 pages

Get the big picture fast

Home→Architecture→Query Loop→Fun Facts
🔬
Deep Dive2 hours7 pages

Full technical picture

Architecture→Query Loop→Tools→Permissions→Agents→Context→Services
🏗️
Builder's Path3 hours5 pages

For those extending Claude Code

Tools→Permissions→Agents→Services→Module Map

Core Execution Loop

Deep dive →
User Input
Prompt + attachments
API Stream
Text + tool_use blocks
Tool Execution
Read=parallel, Write=serial
Permission Check
5-layer security gate
If tools called → loop again

Key Innovations

Streaming Tool Execution

TIMELINE
Model
Tool 1
Tool 2
→ tools overlap with model generation

StreamingToolExecutor queues tool_use blocks as they arrive, cutting end-to-end latency.

Zero-Cost Cache Sharing

HOW IT WORKS
Parent
10K tokens
= bytes
FREE
Child
cache hit ✓

CacheSafeParams frozen at fork time. Identical bytes = automatic prompt cache hit, making subagents nearly free.

Multi-Level Compaction

ESCALATION
Microcompact
Snipping
Autocompact
Collapse

4 escalating strategies keep conversations going indefinitely without hitting hard token walls.

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

Start here

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

Query Loop

7 phases per turn

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

Tools

Read & Write run differently

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

Permissions

Has a real ML model

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

Agents

Cache hit = free spawn

Subagent spawning, zero-cost cache sharing, worktree isolation

Services

MCP = 470KB service

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

Context & Memory

5 prompt layers assembled

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

File Map

1,884 source files

Complete directory structure with key files and their purposes

Fun Facts

There's a duck inside

Easter eggs, buddy pets, the yoloClassifier, wizard comments

Recommended Reading

Architecture
Start here
Query Loop
Core execution
Fun Facts
Easter eggs
By ConnectOnion

Claude Code Pattern Study & Rewrite

Your coding assistant has a duck hiding inside — from anti-ptrace defense to AI dreaming, 50 design decisions you didn't know about. By the Open-source AI Agent Framework team.

𝕏 @ConnectOnionAI
OpenOnion.aiDocs