Reasonbook

Reasonbook, formerly CMOS, is the project record your agents keep: what was decided, why, what was learned, and what remains. The next session can pick up from that record, even in another tool. You make the decisions; agents handle the bookkeeping. No dashboard account is required.

See it work in a 75-second replay of recorded runs in Claude Code and Codex, and read what it sends and stores.

Install it in Claude Code

Install the plugin once for all your projects:

claude plugin marketplace add kneelinghorse/reasonbook
claude plugin install reasonbook@reasonbook

Upgrading from cmos@cmos? Uninstall it before refreshing the marketplace, using claude plugin uninstall cmos@cmos --scope user (or its original project or local scope), then install reasonbook@reasonbook. For a local installation, run the command from that project. If the marketplace already refreshed and uninstall says “not found”, use the tested recovery steps. Upgrade every client before moving an existing record.

For candidate testing, replace kneelinghorse/reasonbook with this checkout's absolute path. Start a new Claude Code session after installation. The plugin supplies the MCP server, hooks and commands; its first cold session may report that Reasonbook is installing and load the record from the next session. Use /reasonbook:init for a new record, /reasonbook:start to read it, /reasonbook:close-out to finish work, /reasonbook:plan to plan, and /reasonbook:build to execute. Plugin installation. Other tools use the harness adapters and coverage guide.

Get a project digest in three steps

Requires Node.js 20 or newer.

1. Install the pinned CLI:

   npm install -g @aquex/reasonbook@4.0.1
   

   Ensure the global npm bin directory is on your PATH. If the former package is installed globally, run npm uninstall -g @aquex/cmos-mcp first. Version 4 provides only the reasonbook command; update scripts and MCP configurations that use the old command.

2. In the project folder you want to track, start a Ledger:

   cd /absolute/path/to/your/project
   reasonbook init --level ledger
   

3. Read its first digest:

   reasonbook review --format=context
   

The digest names this project and shows its decisions, lessons and open work. A new Ledger starts empty. Planner adds next steps; Builder adds sprints and missions.

Codex plugins — 4.0.1

The developer plugin reasonbook supplies the server, seven skills and five lifecycle hooks. The conversation-focused reasonbook-chat supplies the same server and six distinct chat skills, with no hooks. Plugin loading, installation and project calls are verified in the bundled Codex CLI and app-server. ChatGPT Work remains unverified; this is not a hosted plugin for ChatGPT web or phone.

Install the developer plugin:

codex plugin marketplace add kneelinghorse/reasonbook
codex plugin add reasonbook@reasonbook

If the plugin is installed under its former name, remove it first, because both plugins answer as the same server: codex plugin remove cmos@cmos, and codex plugin remove cmos-chat@cmos for the chat plugin.

For chat workflows, install reasonbook-chat@reasonbook instead:

codex plugin add reasonbook-chat@reasonbook

For local development, replace the marketplace repository with this checkout's absolute path. Both plugins can be enabled together: Codex loads one server named rbook, and both sets of skills remain visible. Choose the developer plugin for building; choose the chat plugin for setup, catch-up, recall, proposing decisions, capturing notes and discussing next steps.