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Reasonbook

Formerly CMOS

Pick up where the work left off.

Every new agent session starts cold. Reasonbook keeps what your project decided and why, and what's still open, in a SQLite database in your repository, and brings it into the next session.

Get started

How it works

  1. Record a decision and its reason.

    You make the decisions. Your agent writes each one down with the reason, as it works.

  2. Start the next session with it.

    In Claude Code and Codex, the Reasonbook plugin brings the record into each new session on its own. Without the plugin, one call to rbook_review returns the same digest.

  3. Add planning when the project needs it.

    A new project starts as a Ledger of decisions and what you learned. Planner adds next steps. Builder adds sprints and missions with objectives and success criteria, and starting a mission brings up the past decisions that bear on it.

Install it in Claude Code

Install the plugin once for all your projects:

claude plugin marketplace add kneelinghorse/reasonbook
claude plugin install reasonbook@reasonbook
CLI, Codex and other tools

See it work

A 75-second replay of recorded runs in Claude Code and Codex.

Watch the handoff demo

Local first. The dashboard is optional.

The core loop runs with no network connection, and everything lives in your project's SQLite database. Nothing needs an account. An optional one at reasonbook.ai keeps a hosted copy of the whole database, uploaded a few minutes after your agents stop writing, and gives your projects addresses so they can message each other. One setting turns the uploads off.