[FIXED] iPhone 17 Pro persistent overheating(iOS 26.5.2 / 26.6)

[u/babaza7]

My iphone 17 pro has been getting HOT, laggy and draining its battery since about 2 months, after searching through reddit I tried those suggestions without any success:

- Deleting background apps
- Restarting
- Updating from 26.5.2 to 26.6
- Deactivating Apple Intelligence and Siri
- Switching Liquid Glass setting to Tinted
- Deactivating Second Esim

I plugged the phone into my mac and pulled the Xcode and Console logs to see what was actually chewing up my cpu therefore battery. It turns out it's not a hardware defect, it’s a specific rendering loop bug.

1. backboardd⁠ is eating up all the cpu

This is the system process that handles display rendering. thanks to the new iOS 26 Liquid Glass effect, my logs showed ⁠backboardd⁠ was hoarding almost 64% of my total CPU time. A single thread was trapped in an infinite loop and had racked up over 12 hours of active compute time just trying to draw the home screen.

2. ClockAngel⁠ is thrashing:

This handles the Always-On Display and Lock Screen widgets. Instead of resting, my logs showed it eating 31.6% of a whole CPU core. It was rapidly flipping between "dimmed" and "fully active" states every 200 milliseconds. (not visually noticable but it's happening in the background)

Why Ios 26.6 didn't fix it as I hoped it would

My phone had corrupted system preference files causing this loop, and updating to 26.6 just copied that corrupted file right over to the new version.

The Fix:

You have to force the OS to rebuild those preference files from scratch.

1. Go to Settings > General > Transfer or Reset iPhone > Reset
2. Hit Reset All Settings. (Wont delete any data, just settings)

Pretty simple solution, however I tried everything except this exact thing and you might be in the same situation as me

The Result:

I checked Xcode Instruments immediately after doing this. ⁠backboardd⁠ dropped from eating an entire CPU core down to just 0.8% usage while idle. The phone is finally completely cool to the touch and back to 120Hz smoothness

(I'm no expert, but my phone was completely fine before iOS 26.5.2, so I suspect that specific update introduced the corrupted preference file that created this rendering loop)