mainThreadHang

Watches the main run loop directly. A reading each time a hang starts or resolves, sharing a faultId with the thread snapshot it triggers.


Delivery	stream, onChange
Mechanism	runLoopObserver
Requires	iOS 17+, basset 0.1.1+

Config (concurrency.mainThreadHang:key=value,...)

thresholdMs (int 100…60000): How long the main thread must stay busy before this reports. Default 2000.

Real output from basset request get, captured against a running app:

CAPTURED                  ELAPSED  INSTRUMENT

launch 12527301282799096824
2026-08-23T14:26:24.864Z  +0.0s    concurrency.mainThreadHang(mainThread)
├─ hangNanoseconds   2130051708
├─ hangResolved      false
├─ runLoopTurnCount  4
└─ faultId           1
2026-08-23T14:26:26.069Z  +1.2s    concurrency.mainThreadHang(mainThread)
├─ hangNanoseconds   3231712250
├─ hangResolved      true
├─ runLoopTurnCount  4
└─ faultId           1

Getting Started

SDK

CLI

Instruments

Reference

mainThreadHang