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Thread Checker

Detect main thread violations with detailed stack traces.

The Thread Checker flags UI updates and other main-thread-only work happening on background queues. Each violation includes a stack trace pointing to the offending call site.

Thread Checker — violation list

Common causes

  • Updating UILabel or SwiftUI state from a URLSession callback
  • Core Data access off the main context queue
  • Dispatching UI work to a global queue by mistake
Thread Checker — stack trace
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