A tiny change to body or to state ownership can raise per-frame CPU on lower-end devices and turn a calm rollout into an urgent rollback.
Profile on representative physical devices (include lower-end models) with Time Profiler, Core Animation, and Allocations to surface CPU, compositing, and churn hotspots.
Use OSSignposter to mark coarse phases (for example: decode, layout, render) and add finer signposts only in narrow canaries so you can correlate trace phases without inflating overhead.
Move heavy per-frame work out of body: precompute or decode images off the main thread and inject a ready-to-draw CGImage into views when possible.
Gate instrumentation and ownership changes behind feature flags, and attach representative Instruments traces to bug reports to aid reproducibility.
Choose explicit state ownership when you need predictable lifetimes and narrower render boundaries; prefer view-local @State for tiny, tightly scoped data.
Combine OSSignposter, Instruments, and CI- or XCTest-gated performance checks to make a repeatable trace → instrument → validate loop.
Have you used signposts in a canary to catch a render regression before rollout? Share one concrete lesson and what you changed as a result.