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I have an Apple Bluetooth keyboard and trackpad that I share between two MacBook Pros (one personal, one from my employer).

I keep Bluetooth disabled on whichever laptop I'm not using, and the keyboard and trackpad will usually automatically connect to the other laptop.

However, some days the keyboard (and the trackpad, on rarer occasions), still re-connects to my personal MacBook Pro (MacBookPro11,4 on macOS 12.4), even though Bluetooth is disabled. System Preferences, Control Center, and running bluetoothd all show that Bluetooth is disabled, yet the phantom connection persists.

This behavior started occurring after I did a clean install of macOS Monterey in October 2021, and has persisted across subsequent updates (currently running macOS 12.4).

I solve this by toggling Bluetooth on and back off, after which the keyboard is disconnected (and will connect to my other MacBook Pro). But I'm baffled by this "phantom" Bluetooth connection, and would love ideas on how to investigate this further.

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  • Do you have an iCloud account, or have "Universal Control" turned on? The former might be storing Bluetooth connections in the cloud, and the latter might be sharing them from a nearby device (not idea if it would show up in bluetoothd, though)
    – chronospoon
    Commented Jul 24, 2022 at 20:44
  • @chronospoon excellent idea! Both laptops are indeed signed in to the same iCloud account. My personal MacBook is too old to support Universal Control, but my newer work MacBook has it enabled. I'll try disabling Universal Control there and see if the phantom connections happen again or not.
    – penguinrob
    Commented Jul 25, 2022 at 16:25
  • @chronospoon I just reproduced the issue again. 😄 This time was with Universal Control turned off on the newer MacBook Pro that supports it, and both laptops had bluetooth turned off. The keyboard and trackpad still connected to the older MacBook Pro.
    – penguinrob
    Commented Aug 11, 2022 at 13:34
  • I don't know if this provides any clues, but when the trackpad connects in this state, multi-touch gestures (scrolling, swiping between spaces, etc.) don't work. Only single-finger cursor movements and clicking work. When I enable Bluetooth and the trackpad reconnects, then all gestures again work as expected.
    – penguinrob
    Commented Aug 11, 2022 at 13:39

1 Answer 1

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Some ideas for why it's connecting, despite Bluetooth disabled:

  • iOS, and perhaps macOS, will automatically re-enable Bluetooth/Wi-Fi after something like 24 hours, if you disable it from the Control Center. Go into Settings to actually disable it.
  • The Bluetooth state machine is very complicated; in this case, note that the keyboard/trackpad can also remember their sides of the connection, and may attempt to reconnect to whichever MacBook has a stronger signal at the time.
    • For troubleshooting purposes, you could try resetting the keyboard and trackpad, so they forget about their paired connections.
    • There's potentially a sort of ping-pong effect where you wipe one side of the Bluetooth connection, the other keeps re-instantiating it, and the connection's never fully cleared out. One way to avoid this is to keep the Bluetooth peripherals off, reset the macOS Bluetooth stacks, and then factory reset the keyboard/trackpad before turning them back on.

Note that the above steps are all about fixing Bluetooth specifically; it sounds increasingly unlikely that Bluetooth is the issue here. The part with "multi-touch gestures don't work" is probably a large clue; I'd suspect KVM-type software at work, since a lot of programs don't bother/are unable to transport multi-touch gestures correctly.

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