swiftui-performance-audit

Start with a code-first review looking for expensive work in body such as formatters, sorting, and filtering, plus unstable ForEach identity and broad observation. If code review is inconclusive, capture a Release-mode trace with the SwiftUI Instruments template and inspect Long View Body Updates with Time Profiler.

Janky scrolling usually comes from unstable identity, inline filtering inside ForEach, or heavy row bodies. Use stable domain identifiers instead of id: \.self, pre-filter and pre-sort collections before rendering, and move formatting or image decoding off the main thread.

Use the SwiftUI template, which combines the SwiftUI instrument with Time Profiler and hang or hitch detection. Record in a Release build on a real device, reproduce only the problematic interaction, and inspect Long View Body Updates and Update Groups.

Broad @Observable models cause update fan-out when many views read the same large collection or root object, so one small change invalidates many views. Narrow the observable surface with per-item view models or scoped state so only affected views update.

Use equatable() only when equality checking is cheaper than recomputing the subtree and the view inputs are value-semantic and stable. Applying it as a blanket fix can add comparison overhead without reducing actual render work.

Code review falls short when symptoms like hangs, hitches, or memory growth have no obvious code-level cause. In those cases capture a SwiftUI Instruments trace with Time Profiler on a real device in Release mode, since Debug builds and Simulator distort timing behavior.