How I investigated why my iPhone was running hot
A developer investigates why their iPhone was running hot using USB diagnostics, crash reports, and Xcode Instruments. The process involves installing pymobiledevice3 to read battery diagnostics and historical CPU resource reports, which revealed that photoanalysisd (Apple's Photos analysis service) had repeatedly exceeded iOS CPU limits. Enabling Low Power Mode deferred that work, but a live Instruments trace showed other processes like fseventsd (72.7% CPU), fileproviderd (42.5%), and Twitter (peaking above 300%) were still active. Despite the investigation, no single definitive cause was identified — the battery was healthy, but multiple system services were doing significant background work. Practical advice includes restarting the phone, enabling Low Power Mode, and recording a deferred Activity Monitor trace with Instruments.