Tethered Internet still active when closing lid on MBP 16" (M3) - draining batteries and heating laptop in bag

[matsan]

Don't know if this is machine- or OS-specific. Lately I've been working while on the road and found a rather annoying issue when using Tethered Internet from my iPhone 13 - the MBP 16" stays on even with lid closed. This drains the battery of both devices and (worse) really heats up the laptop in its sleeve!
Running macOS 15.3 and iOS 18.3.

Googling I've found that seems to be related to power nap, but I have this set to "Only on Power Adapter" so there must be some other setting as well. This doesn't happen when I connect to WiFi at a cafe, only when using the iPhone. If this is due to the cafe's WiFi going away or not I can't tell.

Given Apple's latest Lid Gate - https://www.macrumors.com/how-to/prevent-macbook-turning-on-when-lid-is-opened/ - maybe there's a command from the (ahem!) Terminal I should use...

 

[smoking monkey]

I noticed this recently as well. I packed away my laptop in my backpack, left work, got home, went about my business at home for a little and noticed the tethering symbol still present on my phone in the DI.
I flipped tethering off to stop it. but it's happened several times. I'll be at work, go off for a bit then come back and open the laptop and it's still connected. It's actually quite convenient to be fair. So maybe it's a feature???

Perhaps it's location aware? Maybe it thinks I want to tether at home even though I've never done so.

 

[matsan]

So maybe it's a feature???

Yeah, I hope the expensive machine doesn't break due to warming up too much in the bag though...
I got the laptop out of the bag after four hours travel and it was hot to touch and the fans started spinning when I connected it to the USB-C station in the office.

 

[jakdaniel1975]

it happened to me now I always turn off the wifi before closing the lid and putting it in the backpack

 

[adrianlondon]

There's more than one bug in this area.

At home and on battery, lid closed for a few hours, "wake for network access" set to never, and the laptop will ring when a Facetime call comes in.

However, it then remembers that it should be pretending to be disconnected and goes quiet after a couple of rings.

 

[matsan]

Changed the Battery setting to "Never" and still see the machine active on the WiFi network (UniFi, see associations and disconnects in the logs) during night so something is triggering it to connect.