Introduction

Review a Git diff one file at a time with context beside the code.

Diffsplain opens a local review page for a checkout, branch, pull request, worktree, or exact Git range. It shows one changed file at a time, with the patch on the left and a short coding agent note on the right.

Start a review

You need Node.js 22.13 or newer and Git. For agent notes, you also need a signed-in coding agent CLI. Set a default with diffsplain config agent NAME or choose one run with --agent NAME. With neither set, an interactive terminal lists usable agents in this order: Codex, Claude, Copilot, Cursor, then OpenCode. You choose one; Diffsplain does not switch agents if it fails. In scripts, set a default, pass --agent NAME, or use --no-agent for a plain review.

Cursor Agent must be version 2026.08.11 or newer. It uses the signed-in Cursor CLI in the user’s home. Cursor still contacts its service.

npx diffsplain

The command opens a local page showing staged, unstaged, and untracked changes against HEAD, the same as --worktree. It starts at port 2299 and uses the next free port when needed.

For a pull request:

npx diffsplain --pr 198

Pull request reviews also need the GitHub CLI. Run gh auth login first if needed.

What the command changes

Diffsplain reads the selected Git data and writes its own cache. It does not switch branches or change the target checkout, index, local refs, or FETCH_HEAD.

Use the arrow buttons or the left and right arrow keys to move through files. Press Cmd+K or Ctrl+K to search the file list.

See CLI usage for every target and option.