MetricKit (iOS production telemetry)

Field-collected power/performance metrics and crash/hang/exception diagnostics, aggregated on-device by the system and delivered to your app — no third-party SDK, no per-event network cost. Grounded in Apple's MetricKit framework.

• On-device & privacy-preserving: the OS aggregates over a 24h window and hands you a payload; nothing leaves the device until you upload it. No PII, no user identifiers — safe for a fintech privacy posture. Still declare any upload/collection in the privacy manifest (see app-store-review).
• Delivery cadence: subscriber callbacks fire at most once per day, on a background queue, and only when the app has been foregrounded since the last delivery. Diagnostics can also arrive right after the next launch following a crash/hang.
• Two APIs: the stable delegate-based MXMetricManager (iOS 13+, crashes/diagnostics iOS 14+) — the default for the iOS 26 era — and the new async MetricManager (iOS 27, WWDC26) covered in references/new-metricmanager.md.
• Not a profiler. MetricKit tells you what regressed in the field, aggregated; to root-cause locally with call trees and allocations use debugging-instruments.

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