A browser-based diff viewer for cmux. See what changed at a glance — syntax-highlighted diffs, inline review comments, commit history, GitHub PR status, and custom toolbar actions, all streamed in real time via WebSocket.

Syntax-highlighted diff with add/delete coloring and line numbers.

Select lines and write review comments that are sent to the cmux terminal.

Browse recent commits when no pending changes are detected.

Branch name, navigation links, and custom action buttons.

Update screenshots: bun run screenshots

• Diff view with syntax highlighting (Shiki)
• Real-time diff updates via WebSocket
• Untracked and unstaged file detection
• Commit history browser (when no pending changes)
• Plan file viewer (Claude Code session plans with syntax highlighting)
• Branch selector for switching diff base
• Hash-based URL routing with browser back/forward support
• Custom toolbar actions via JSON (with submenu support)
• File watcher with auto-refresh (working tree + git ref changes)
• Inline review comments sent to cmux terminal
• GitHub PR integration (CI status, PR review comments)
• WebSocket real-time updates (diff changes, PR/CI polling)
• Self-update command (cmux-hub update)
• Auto-shutdown when browser tab closes
• Git worktree support

cmux-hub connects to the cmux Unix socket (/tmp/cmux.sock). The default socket mode only allows cmux child processes to connect.

If you launch cmux-hub from within cmux (e.g. Claude Code commands, terminal shell), the default mode works. If you launch from an external process (Alfred, Raycast, Karabiner Elements, etc.), set Automation mode:

cmux Settings → Automation → Socket Control Mode → Automation mode

Or set CMUX_SOCKET_MODE=allowAll.

Download binary from GitHub Releases:

mkdir -p ~/.local/bin
curl -fsSL "https://github.com/azu/cmux-hub/releases/latest/download/cmux-hub-darwin-arm64" -o ~/.local/bin/cmux-hub
chmod +x ~/.local/bin/cmux-hub

cmux-hub update

# Run (diff of current directory)
cmux-hub

# Specify target directory
cmux-hub /home/user/project

# Custom toolbar actions
cmux-hub --actions actions.json

# Read actions from stdin
cat actions.json | cmux-hub --actions -

When launched inside cmux, cmux-hub automatically opens a browser split pane and shuts down when the pane closes.

Install as a Claude Code plugin. This auto-installs the binary, sets up SessionStart hooks, and copies default actions to ~/.claude/cmux-hub.json. Project-local .claude/cmux-hub.json takes priority if present.

claude plugin marketplace add azu/cmux-hub
claude plugin install cmux-hub@cmux-hub-marketplace

The first session start downloads the binary, so it may take a few seconds to launch.

Update the plugin:

claude plugin update cmux-hub@cmux-hub-marketplace

.claude/cmux-hub.json:

[
  { "label": "Commit", "type": "paste-and-enter", "command": "commit this change" },
  { "label": "Create PR", "type": "paste-and-enter", "command": "create a pull request" }
]

.claude/settings.json:

{
  "hooks": {
    "SessionStart": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "cmux-hub --actions .claude/cmux-hub.json"
          }
        ]
      }
    ]
  }
}

-p, --port <port>      Server port (default: random)
-a, --actions <file>   Toolbar actions JSON file (use - for stdin)
--dry-run              Don't connect to cmux socket
--debug                Enable debug logging (also: DEBUG=*)
-v, --version          Show version
-h, --help             Show help

The /api/diff/auto endpoint computes the appropriate diff range based on the current branch.

When no pending changes are detected, the UI shows recent commits. Clicking a commit displays its diff. A "Commits" link in the toolbar opens the commit list at any time.

Pass a JSON file via --actions to customize toolbar buttons. The type field is required.

[
  {
    "label": "Commit",
    "type": "paste-and-enter",
    "command": "/commit"
  },
  {
    "label": "Create PR",
    "type": "shell",
    "command": "gh pr create --title \"$TITLE\"",
    "input": { "placeholder": "PR title...", "variable": "TITLE" }
  },
  {
    "label": "More",
    "submenu": [{ "label": "Stash", "type": "shell", "command": "git stash" }]
  }
]

Commands can reference shell variables. Variables are prepended as inline environment variables (env prefix).

Variables defined in input.variable are set as environment variables from user input.

{ "command": "git commit -m \"$MSG\"", "input": { "variable": "MSG" } }

Variable values are single-quote escaped and prepended as env prefix. The /api/action endpoint only accepts an action ID and user input variables — not raw command strings. Variable keys are validated against [A-Za-z_][A-Za-z0-9_]*.

When the current branch has an associated Pull Request, cmux-hub polls GitHub via gh CLI and displays:

• CI check statuses (success, failure, in-progress)
• PR review comments with file path and line number
• PR info (title, state, base/head branch)

PR data is pushed to the frontend via WebSocket every 10 seconds.

WebSocket endpoint: /ws — receives diff-updated and pr-updated messages.

• Localhost-only server (127.0.0.1)
• Host header validation (DNS rebinding)
• Origin header validation (CORS/CSRF)
• Sec-Fetch-Site check on write operations
• Null Origin rejected on POST from browsers
• File path access restricted to repository cwd
• Commit hash validated against /^[0-9a-f]{4,40}$/i

bun install

# HMR with hot reload
bun --hot src/cli.ts

# With custom actions
bun --hot src/cli.ts --actions - <<'EOF'
[
  { "label": "Commit", "type": "paste-and-enter", "command": "commit this change" },
  { "label": "Push", "type": "shell", "command": "git push" }
]
EOF

# Build standalone binary
bun run build:compile

bun test          # Run tests
bun run lint      # Lint
bun run fmt       # Format
bun run typecheck # Type check
bun run test:e2e  # E2E tests

• Runtime: Bun
• Frontend: React 19 + Tailwind CSS + shadcn/ui
• Syntax Highlighting: Shiki
• cmux communication: Unix domain socket (/tmp/cmux.sock) via JSON-RPC
• git: Bun.spawn with git CLI
• GitHub: gh CLI

• Difit
• Codex
• Claude Code on the web

MIT