Modernizing iOS SDK Concurrency Without a Full Rewrite

Modernizing concurrency in a mature SDK does not necessarily require redesigning its architecture. Apriorit describes migrating a production iOS SDK from ReactiveSwift to native Swift concurrency while preserving its repository-based event model and existing integration behavior. The incremental approach replaces third-party reactive dependencies with AsyncStream, improves traceability of asynchronous flows, and treats stream lifecycle, subscriber isolation, and shared-state synchronization as explicit design concerns. Engineering leaders should evaluate concurrency modernization around integration risk and architectural stability, not simply adoption of newer APIs.