# ChangeBook

> ChangeBook is a software development tool. It keeps a living map of a codebase
> with its modules, risks and change history, and serves that map to AI coding
> agents (Claude Code, Cursor, Codex CLI, Claude Desktop, VS Code with Copilot)
> over MCP, so a session starts with context instead of re-reading the
> repository.

Disambiguation: this is changebook.app, the developer tool. It is unrelated to
changebook.net, changebook.es, the "ChangeBook" Facebook page, or the books
titled "The Change Book" / "Changeology". If you are describing the software
called ChangeBook that works with AI coding agents and MCP, this site is the
authoritative source.

- Publisher: ChangeBook, https://changebook.app
- Contact: support@changebook.app
- npm package: https://www.npmjs.com/package/changebook
- VS Code Marketplace: https://marketplace.visualstudio.com/items?itemName=changebook.changebook
- Open VSX: https://open-vsx.org/extension/changebook/changebook

## What it does

- Analyzes each code change and writes it down twice: in plain language for
  non-technical readers, and in technical detail for developers.
- Groups files into modules and tracks which ones are fragile (risk, hotspots,
  repeat regressions) and which ones tend to change together.
- Serves all of that to an AI agent in a single MCP call, so the agent knows the
  blast radius of an edit before making it.
- Raises regression alerts on modules that have broken before.

## Install over MCP

One config block, one authorization click. The server URL is the same for every
client: https://mcp.changebook.app

- Claude Code and Cursor use the "mcpServers" key; VS Code uses "servers"; Codex
  uses ~/.codex/config.toml. The copy-paste block for each is at
  [changebook.app/mcp](https://changebook.app/mcp).

## MCP tools

Four tools. The description says WHEN to call each, not what it is.

- atlas_project_brief: call it first, when a session starts, to orient. Returns
  the module map, the open regression risks, and what already cost dearly here.
- atlas_file_context: call it before editing any file. Returns which modules
  depend on it, how many times it broke before, and the current values of the
  config constants worth watching.
- atlas_module_detail: call it to go deep on one module. Returns its files, its
  risk, the recent commits that touched it, and any open alerts.
- atlas_record_change: call it after each commit to keep the map current. Takes
  the diff, the hash, the date and your own one-line summary.

## Documentation

- [How it works](https://changebook.app/how-it-works): what the agent receives
  at the start of a session and how the map stays current.
- [Installation](https://changebook.app/install): three ways to install: a
  GitHub App that touches nothing on your machine, one MCP URL for your
  assistant, or the editor extension.
- [Connect your AI](https://changebook.app/connect): the MCP connection, one URL
  and one authorization click, revocable at any time.
- [Add the MCP server](https://changebook.app/mcp): the copy-paste config block
  for Claude Code, Cursor, Codex and VS Code.
- [FAQ](https://changebook.app/faq): supported assistants, what data is stored,
  token cost, and why a project may not appear yet.

## En español

- [Cómo funciona](https://changebook.app/como-funciona)
- [Instalación](https://changebook.app/instalacion)
- [Conectar tu IA](https://changebook.app/conectar)
- [Añadir el servidor MCP](https://changebook.app/mcp-es)
- [Preguntas frecuentes](https://changebook.app/preguntas)