Signal

A macOS menu-bar status light app — a breathing LED that lives in your status bar.

Features

• Breathing LED in the menu bar with a 3D glow effect
• Three colors: 🟢 Green (calm) → 🟡 Yellow (caution) → 🔴 Red (alert)
• Each color breathes at a different speed (red = fastest, green = slowest)
• CLI companion (sgnl) for scripting and automation
• LSUIElement — no Dock icon, pure menu-bar app
• macOS 14+ (Sonoma)

Build & Installation

Option 1: Direct Build & Installation

Build the app and install it to your system paths:

make build    # Build release binary & .app bundle
make run      # Build and launch immediately
make install  # Copy .app to /Applications and CLI helper to ~/.local/bin
make clean    # Remove build artifacts

Option 2: Package as DMG

Build a clean, shareable disk image (.dmg) containing Signal.app and a shortcut to /Applications:

make dmg      # Packages the app into .build/Signal.dmg

To install:

1. Open the DMG and drag Signal.app to your Applications folder.
2. Launch the application.
3. Open the status bar controls and click "Install 'sgnl' CLI Command" to install the sgnl command line tool directly to ~/.local/bin without using terminal scripts.

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Code Signing & Troubleshooting

For instructions on signing the application with an Apple Developer Account, or resolving macOS Gatekeeper warnings ("app is damaged" / "unidentified developer"), please see SIGNING.md.

CLI Usage

sgnl red       # Switch to red   (fastest breathing, ~1.2s cycle)
sgnl yellow    # Switch to yellow (medium breathing,  ~2.4s cycle)
sgnl green     # Switch to green  (slowest breathing, ~4.0s cycle)
sgnl help      # Show help

sgnl breath off # close effect

Automation Examples

# Turn red on test failure
if ! make test; then sgnl red; fi

# CI status monitor
sgnl green   # deploy succeeded
sgnl red     # deploy failed

Claude Code Hook Integration

You can integrate sgnl with Claude Code hooks to turn your status bar light into a physical/visual indicator of Claude's state!

Add the following to your project-level or global .claude/settings.json file:

{
  "hooks": {
    "SessionStart": [
      {
        "type": "command",
        "command": "sgnl green",
        "shell": "bash",
        "timeout": 3
      }
    ],
    "UserPromptSubmit": [
      {
        "type": "command",
        "command": "sgnl yellow",
        "shell": "bash",
        "timeout": 3
      }
    ],
    "PermissionRequest": [
      {
        "matcher": "*",
        "hooks": [
          {
            "type": "command",
            "command": "sgnl red",
            "shell": "bash",
            "timeout": 3
          }
        ]
      }
    ],
    "Stop": [
      {
        "type": "command",
        "command": "sgnl off",
        "shell": "bash",
        "timeout": 3
      }
    ]
  }
}

• Green (Idle/Ready): Lights up when you start a session or when Claude stops thinking and waits for your input.
• Yellow (Thinking/Working): Breathes with a caution light whenever you submit a prompt and Claude starts executing tools/thinking.

Architecture

signal/
├── Package.swift              # SwiftPM manifest
├── Makefile                   # Build system
├── Resources/
│   └── Info.plist             # LSUIElement = true
└── Sources/
    ├── Signal/
    │   ├── main.swift         # NSApplication entry point
    │   └── AppDelegate.swift  # Status item, animation, IPC
    └── sgnl/
        └── main.swift         # CLI → DistributedNotification

IPC: The CLI tool posts a DistributedNotification (com.signal-light.colorChange) that the app observes. No sockets, no files — just the macOS notification bus.

Requirements

• macOS 14.0+ (Sonoma)
• Swift 5.9+
• Xcode Command Line Tools