ios-ettrace-performancelisted

# iOS ETTrace Performance Use ETTrace for a bounded, symbolicated sampling experiment. Treat capture conditions and symbolication as part of the evidence, not as setup trivia. ## Contents - [Boundary](#boundary) - [Capture Contract](#capture-contract) - [Workflow](#workflow) - [Interpret the Report](#interpret-the-report) - [Common Mistakes](#common-mistakes) - [Review Checklist](#review-checklist) - [References](#references) ## Boundary This skill owns ETTrace framework/CLI capture, exact-build dSYMs, processed flamegraph JSON, and like-for-like verification. Use Instruments for broad CPU, hitch, energy, or concurrency triage. Use SwiftUI performance guidance for view identity, invalidation, and layout remediation. ETTrace periodically samples thread stacks. Its durations reconstruct sampled attribution from those intervals; do not present them as wall-clock production timings or compare them directly with a differently configured profiler. ## Capture Contract Write these down before capturing: - one exact user flow and its start/stop boundary; - launch capture or already-running runtime capture; - app commit, build configuration, optimization settings, and architecture; - ETTrace runner and framework versions, plus single-thread or multi-thread mode; - simulator/device model and OS build; - launch method, data state, cache state, and repetition count. Reject a before/after claim when any of these materially differ. Rebuild and repeat under one contract instead. #