claude-skill

claude-code-from-scratch – Rebuild Claude’s Core in 4k Lines

Name: claude-code-from-scratch – Rebuild Claude’s Core in 4k Lines
Author: Windy3f3f3f3f

Recreate Claude’s 500k‑line codebase with a 4k‑line TypeScript/Python skeleton and an 11‑chapter guide. Ideal for founders who want to master coding agents.

From the repo · “Build your own Claude Code from scratch. 🔍 Claude Code 开源了 50 万行代码，读不动？用 ~4000 行 TypeScript / Python 从零复现核心架构，11 章分步教程带你理解 coding agent 精髓”

2,786 stars+34★ this week555 forksPythonGuide quality 9/10 · reviewed Oct 14Updated 7/9/2026100% free · open source

What it does

Create a custom coding agent from scratch using Claude Code's open-source architecture, replicating its core functionality with approximately 4,000 lines of code in Python or TypeScript.

When to use it

•When you need a tailored coding assistant for your specific development workflow
•To understand the inner workings of Claude Code and modify it to suit your requirements
•As a learning resource to grasp the fundamentals of coding agents and their architecture

Ready-to-paste prompt

To start building the coding agent, begin with the first chapter of the tutorial and execute the command `python chapter1.py` to initiate the setup process

Heads up: Before starting, ensure you have a good understanding of Python and TypeScript, as well as the necessary dependencies installed, and be aware that the project involves working with a large codebase of approximately 4000 lines

Saves to your device

Use with Claude

New

Skip the builder — one click puts this in Claude, Cursor, Antigravity and more.

⚡ Runs out of the box

A prompt/skill package — nothing to install beyond adding it to your AI tool.

Try it instantly — no install

Claude Code

mkdir -p ~/.claude/skills/claude-code-from-scratch && curl -fsSL https://workflowstacks.com/api/skills/claude-code-from-scratch/claude-skill -o ~/.claude/skills/claude-code-from-scratch/SKILL.md

Open in another AI app

Opens the app with this repo with the prompt ready to go — no copy-paste needed.

Connect the whole catalog (MCP)

claude mcp add --transport http workflowstacks https://workflowstacks.com/api/mcp

Adds a WorkflowStacks connector to Claude Code: search and load any skill here by chatting.

How claude-code-from-scratch – Rebuild Claude’s Core in 4k Lines works

Codeflow

Free to inspect

Claude-code-from-scratch – Rebuild Claude’s Core in 4k Lines is a large Python project (~16k lines across 62 code files, plus 22 test files). It is a full software project: use it through its install path rather than reading it end to end. Last commit 3 months ago, MIT license, has a test suite.

Size

Large codebase

~16k lines · 62 code files · ~2 h to skim

Setup

Developer setup

A real software project. Use it via its install path; don't expect to read it all.

Runs on

Node.js

Needs API keys (.env)

Python 41%TypeScript 37%JavaScript 19%HTML 3%

Where to start reading

1
README.md
Start here — what it does and how to install it
2
CLAUDE.md
The instructions the AI actually follows
3
src/cli.ts
Where the program starts running
4
package.json
Dependencies and the commands it exposes
5
.env.example
The API keys and settings you must provide

What's in each folder

src/Core code — the actual logic12 files

docs/Documentation17 files

steps/Folder51 files

python/Folder24 files

en/Folder18 files

test/Tests — proof it works25 files

.claude/Editor / agent settings4 files

assets/Images & static assets3 files

READMEHas testsDocumentedNo CIMIT licenseUpdated 4 mo ago

Use with Claude

New

Skip the builder — one click puts this in Claude, Cursor, Antigravity and more.

⚡ Runs out of the box

A prompt/skill package — nothing to install beyond adding it to your AI tool.

Try it instantly — no install

Claude Code

mkdir -p ~/.claude/skills/claude-code-from-scratch && curl -fsSL https://workflowstacks.com/api/skills/claude-code-from-scratch/claude-skill -o ~/.claude/skills/claude-code-from-scratch/SKILL.md

Open in another AI app

Opens the app with this repo with the prompt ready to go — no copy-paste needed.

Connect the whole catalog (MCP)

claude mcp add --transport http workflowstacks https://workflowstacks.com/api/mcp

Adds a WorkflowStacks connector to Claude Code: search and load any skill here by chatting.

Quick Actions

Details

Creator

Windy3f3f3f3f

Language

Python