Worked on the getsentry/sentry-cocoa repository to address a critical stability issue in the FramesTracker component, focusing on concurrency management within iOS development using Swift. Delivered a targeted bug fix that resolved a race condition occurring when listeners were added or removed on background threads, which previously risked crashes during listener initialization or deinitialization. The solution involved implementing weak-reference lifetime management and ObjectIdentifier-based tracking to prevent retaining deallocated objects. Added a deterministic regression test to ensure closures do not strongly retain listeners across asynchronous dispatch, and updated documentation to improve traceability, thereby enhancing reliability for applications relying on FramesTracker.