Known issues

This page lists issues that affect Cable Detective users, including the one that was ours. We list them here for transparency.

The whole Mac restarts on plug or unplug while Cable Detective is open - fixed in 1.8.1

What happened

With the app open, plugging or unplugging a USB-C, Thunderbolt or MagSafe device could hard-panic macOS inside Apple's port-controller driver (com.apple.driver.AppleHPM): the Mac shows the restart screen, or freezes, and comes back with a kernel panic report. It happened on every Apple Silicon Mac and every macOS 26.x we heard from, only while the app was running, and never for a bare cable with nothing on the other end.

Why it happened

Cable Detective never writes to a port. But up to 1.8.0 it asked macOS to be told about state changes on the port-controller bus device (a kernel "interest notification"). When a device is plugged or unplugged, Apple's driver forwards an interrupt status code to whoever is listening, and it forwards it in a way that is fine for other kernel drivers but makes the kernel treat that small status code as a memory address when the listener is an app. The kernel reads memory address 0x38, which does not exist, and panics. Only apps that register that particular listener on that particular device trigger it; the open-source WhatCable does not, which is why it never crashed anyone.

What changed in 1.8.1

1. Cable Detective registers no interest notifications at all, on anything. It only asks macOS to tell it when a port-related service appears or disappears, which never touches the driver's message path.
2. Port state is read from the registry on the app's own schedule: instantly after a plug or unplug, and every five seconds for changes on a cable that stays connected.
3. A build-time check now fails the build if anyone ever adds an interest notification, a user client, or a property write back into the app.

The earlier 1.8.0 change (no reads inside notification callbacks, a 400 ms settle window) was well meant but addressed the wrong mechanism, which is why 1.8.0 still crashed. The full technical root cause, with the kernel disassembly and the Apple xnu source lines, is written up in detail and we are happy to send it to anyone who asks.

If you sent us a report

Thank you. The four App Store reviews and the four support mails describing this were what made it findable. If 1.8.1 still restarts your Mac on a plug or unplug, please use Settings → Report a bug so we get the full port state with it.

Our own part in it

The same panic hit our own Mac three times in May 2026. We read the panic log, saw Apple's driver in the backtrace, and closed it as an Apple bug that an app could not cause. That was wrong, and it cost four users a crashing Mac for four months.

Reporting a different issue

If you hit something not listed here, email [email protected] with the macOS build, Mac model, and a redacted Copy all export from the affected port.