Performance

Diagnose custom SwiftUI feed jank with stable identity, data-level filtering, bounded nested lazy stacks, and modern scroll visibility APIs before falling back to List.

Make an AVFoundation camera feel ready sooner by splitting preview-critical launch work from deferred output initialization, keeping capture responsive, and testing pressure on real hardware.

Build a field-performance loop with MetricKit reports from real devices, app-state grouping, JSON ingestion, and Instruments traces that reproduce and verify the fix.

Use Device Hub, devicectl, Organizer metrics, and Instruments to reproduce real-device bugs without losing the thread.

Use Instruments' SwiftUI instrument to connect an expensive body update back to the state mutation that caused it, then fix the view instead of guessing.