Just wanted to share this as a heads-up for anyone using an M4 MacBook Air for long development sessions.
I live in a country where there currently isn’t an authorized Apple service center, so getting this properly inspected or repaired under warranty is not straightforward for me. Because of that, I figured I’d at least document what happened.
I bought this MacBook Air M4 in August 2025 and had been using it normally since then without any display issues. Over the past week, though, I used it much more heavily than usual: roughly 14 hours a day in Xcode, running builds, working with Claude Code, and keeping the machine awake with caffeinate -dims.
During one of those sessions, the laptop was sitting on my bed. I turned around and noticed that Xcode had crashed because the system ran out of memory. At the same time, a permanent horizontal line/band appeared along the bottom of the display.
A few details:
The line stays in exactly the same place.
It does not change when I move the lid.
It is still there after rebooting.
There was no drop, pressure damage, or liquid damage.
Because the line does not react to lid movement, it does not seem like a hinge or flex cable issue.
The laptop is less than a year old, so it feels unlikely that this is just some random display defect that happened to show up now.
Of course, I cannot prove that overheating directly caused the display issue. But the timing is hard to ignore: about a week of sustained heavy load, the machine getting very hot, Xcode crashing due to memory pressure, and then a permanent line appearing on the display.
So I guess my warning is: be careful using a fanless MacBook Air for very long heavy workloads, especially on soft surfaces like a bed where heat dissipation is worse. The CPU may throttle, but that does not necessarily mean the whole machine is having a good time thermally.
Has anyone else seen something like this on an M4 MacBook Air or another Apple Silicon MacBook?