Cub

A simple git client with AI code review built in.

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What it is

Cub is a desktop git client. You stage, commit, switch branches, and discard changes the way you would in any other client.

The thing it does that other clients don't: you can review your AI-generated changes inline — leave comments on specific lines, classify them as change-requests, questions, or nits — and an MCP server hands those comments back to the agent so it can address them. No copy-pasting line numbers into chat.

Install

macOS (Apple Silicon — Intel is not supported):

brew install --cask ephraimduncan/cub/cub

Linux — grab the matching artifact from the latest release:

• Cub_<version>_amd64.deb for Debian / Ubuntu
• Cub-<version>-1.x86_64.rpm for Fedora / RHEL
• Cub_<version>_amd64.AppImage for everything else

Cub needs Bun at runtime for the MCP sidecar.

CLI

cub                # launch with the folder picker
cub .              # launch pointed at the current repo
cub /path/to/repo  # launch pointed at a specific repo
cub --mcp          # MCP-only mode, no GUI (for agent configs)

The loop

1. Agent writes a bunch of code.
2. You open Cub on the repo (`cub .`).
3. You browse the diff, leave inline comments
   (change-request / question / nit).
4. You hit "Submit review".
5. In your agent: "address the open review in Cub."
   The agent calls the MCP server, gets your comments,
   makes edits, and marks each one resolved or answered.
6. Cub auto-refreshes; you see what changed and what's left.
7. Stage and commit from Cub when you're happy.

Features

Git client

• Stage, unstage, and discard files from the sidebar
• Commit with message + optional --amend
• Branch switcher in the status bar
• Recent repos and remembered last-opened repo
• Auto-refresh on disk changes

AI code review

• Inline comments on single lines or line ranges
• Classify each comment as change-request / question / nit
• Batched submission — all comments go out together as one review
• Live comment lifecycle: pending → acknowledged → resolved / dismissed, updated as the agent works
• MCP server so any MCP-aware agent (Claude Code, Cursor, etc.) can read and respond

Quality of life

• System / light / dark theme, persisted
• Diff editor font + size, persisted
• Auto-update

Agent setup (MCP)

Cub ships a Node sidecar that exposes an MCP server over stdio. Wire it into your agent like any other MCP tool:

{
  "mcpServers": {
    "cub": {
      "command": "cub",
      "args": ["--mcp"]
    }
  }
}

Tools exposed:

Tool	Purpose
watch_reviews	Long-poll for new submitted reviews
get_review	Fetch the open review's comments (path, line range, text, action type)
acknowledge_comment	Mark a comment as in-progress
resolve_comment	Mark a comment as resolved, with an optional summary
dismiss_comment	Mark a comment as dismissed, with a reason
resolve_review	Close out the review when every comment is handled

Note for agents handling action_type=question: answer in the summary field of resolve_comment. Don't edit code unless the comment is a change-request.

Building from source

Requires Bun, the Rust toolchain, and the Tauri v2 system dependencies.

git clone https://github.com/ephraimduncan/cub.dev
cd cub.dev
bun install
bun run tauri:dev          # hot-reloading dev build (uses dev icon + "(dev)" title)
bun run tauri build        # production binary in src-tauri/target/release/bundle

License

MIT © Ephraim Duncan