Squirrel Trap detects Cmd+Tab so it can pop up alongside the app switcher. On macOS that requires a session-level CGEventTap, which is gated behind the Input Monitoring permission — the same permission a keylogger would need. That's a reasonable thing to be cautious about, so here's exactly what the tap does, in AppSwitchMonitor.swift:

• It's listen-only. The tap is created with options: .listenOnly — it can observe events but cannot modify or consume them. The native app switcher, and every other app on the system, sees every keystroke exactly as if the tap didn't exist.
• It only asks for two event types. eventsOfInterest is limited to keyDown and flagsChanged, plus tapDisabledByTimeout/tapDisabledByUserInput (macOS's own notifications that the tap was suspended, which the code re-enables and nothing else). No other event type ever reaches this code.
• It reads two fields and nothing else. The callback in handleTapEvent checks event.flags.contains(.maskCommand) and event.getIntegerValueField(.keyboardEventKeycode) — whether Command is held, and whether the key is Tab. It never reads a character, unicode value, or any other field. Nothing about what you type is stored, logged, or transmitted; the only thing this code can ever know is "Cmd+Tab happened."
• The app runs without the App Sandbox (com.apple.security.app-sandbox = false in the entitlements). This is a requirement, not an oversight: a session-level CGEventTap cannot be created from inside the sandbox at all. Everything else about the app's own data (the to-do list, preferences) still lives in the normal per-app container regardless.

If you find a security issue, please email jeremy@livedigitally.com with details rather than opening a public issue. We'll acknowledge and work with you on a fix and disclosure timeline.