Use when collecting or analyzing production iOS or iPadOS performance telemetry with MetricKit, including iOS 27 MetricManager async metric or diagnostic reports, hang or crash triage, custom signposts, extended launch measurement, durable export, or iOS 26 MXMetricManager compatibility.

MetricKit Use MetricKit for low overhead production telemetry that complements local Instruments and Xcode Organizer analysis. On iOS and iPadOS 27, prefer the Swift first MetricManager report sequences. Keep MXMetricManager only in an explicit iOS 26 compatibility branch. Beta sensitive: The iOS/iPadOS 27 surface below is based on Apple's current beta documentation. It has not been locally compiler verified because Xcode 27 is unavailable in this environment. Re check the linked Apple documentation and compile with the shipping Xcode 27 SDK before release. Load [MetricKit Extended and Compatibility Patterns](references/metrickit patterns.md) when implementing durable ingestion, detailed report analysis, or the iOS 26 compatibility path. Contents [MetricManager Setup]( metricmanager setup) [Receiving Metric Reports]( receiving metric reports) [Receiving Diagnostic Reports]( receiving diagnostic reports) [Key Metric Results]( key metric results) [Call Stack Trees]( call stack trees) [Custom Signpost Metrics]( custom signpost metrics) [Durable Export and Upload]( durable export and upload) [Extended Launch Measurement]( extended launch measurement) [iOS 26 Compatibility]( ios 26 compatibility) [Xcode Organizer]( xcode organizer) [Scope Boundaries]( scope boundaries) [Common Mistakes]( common mistakes) [Review Checklist]( review checklist) [References]( references) MetricManager Setup At app launch, create and retain one long lived MetricManager . Start exactly one consumer task for metricReports and one for diagnosticReports . Both properties expose nonthrowing AsyncSequence values: metricReports: some AsyncSequence<MetricReport, Never diagnosticReports: some AsyncSequence<DiagnosticReport, Never Apple documents that concurrent consumers of one sequence can receive nondeterministic subsets. Fan out only after the single consumer receives and durably stores a report; delayed subscription can miss reports. The persistence closures are application specific. Implement them with the durable first workflow below rather than dropping, logging only, or directly uploading each report. If state scoped metrics are needed, construct the manager with the documented init(enabledStateReportingDomains:) initializer and the required domains. Receiving Metric Reports MetricReport is Codable and Sendable . It describes an interval through: timeRange: DateInterval optional environment metadata intervalEntries for full day and shorter interval measurements stateEntries for measurements associated with application states Metric reports normally arrive on a daily cadence. Persist the complete report before extracting individual results. For daily analysis, read the documented fullDayEntry and switch over its MetricResult values: Use @unknown default so a beta or future result does not make the ingestion pipeline brittle. Preserve the raw encoded report even when the current app does not understand a result. Receiving Diagnostic Reports DiagnosticReport is Codable and Sendable . It contains a timeRange , required environment metadata, and one DiagnosticResult . Diagnostics are individual, event based reports intended for prompt delivery when MetricKit produces them. Do not assume every crash, hang, or resource event generates a report; system sampling and eligibility still apply. After durable storage, route the result explicitly: The iOS/iPadOS 27 diagnostic types are CrashDiagnostic , HangDiagnostic , CPUExceptionDiagnostic , DiskWriteExceptionDiagnostic , AppLaunchDiagnostic , and MemoryExceptionDiagnostic . The memory exception case is new in iOS 27. Useful fields include: Diagnostic Important fields CrashDiagnostic callStackTree , exception type/code/reason, signal, virtual memory region, termination category/reason HangDiagnostic callStackTree , hangDuration CPUExceptionDiagnostic callStackTree , totalCPUTime , totalSampledTime DiskWriteExceptionDiagnostic callStackTree , totalBytesWritten AppLaunchDiagnostic callStackTree , launchDuration MemoryExceptionDiagnostic callStackTree Key Metric Results Choose a small telemetry vocabulary that matches the investigation rather than exporting every result. Prioritize the relevant categories: responsiveness and terminations; runtime, CPU, memory, network, and storage; or launch, display/GPU, and custom intervals. Aggregate by app version and environment metadata, compare distributions rather than single values, and correlate regressions with releases. Avoid treating a daily aggregate as a precise trace of one user action. Load the [Key Metric Result Catalog](references/metrickit patterns.md key metric result catalog) when mapping exact MetricResult cases into a parser or dashboard. Call Stack Trees The iOS 27 CallStackTree replaces MXCallStackTree . It is Codable and Sendable and exposes: forEachFrame for frame traversal callStackThreads for thread oriented analysis binaryInfo for image and binary metadata Store the complete diagnostic report before flattening or symbolication. Preserve binary identifiers and offsets so server side symbolication can use matching archives and dSYMs. Custom Signpost Metrics Create an OS log through the manager, then use mxSignpost for begin/end measurement: MetricKit exposes the aggregate as MetricResult.signpostInterval . Do not search for a signpostMetrics array on MetricReport . Use mxSignpost when MetricKit resource measurement is required. Apple documents that intervals created with OSSignposter and a MetricKit log handle do not populate the resource measurement fields that mxSignpost provides. Keep high volume local tracing separate from the small set of stable production intervals used for MetricKit aggregation. Durable Export and Upload Treat report delivery as an at least once ingestion problem: 1. Encode the complete MetricReport or DiagnosticReport with JSONEncoder . 2. Atomically enqueue the bytes in an app owned durable outbox. 3. Record report type, schema version, app version, and a stable deduplication key. 4. Acknowledge local processing only after the enqueue succeeds. 5. Upload later with retry, backoff, batching, and retention limits. 6. Mark the outbox item uploaded only after the server accepts it. durableOutbox is an application owned abstraction, not a MetricKit API. Do not perform a synchronous network upload inside the sequence consumer. Durable local storage is the recovery mechanism for reports received through the modern sequences; do not make successful ingestion depend on an assumed modern backfill API. Extended Launch Measurement Use trackLaunchTask(id:onTrackingError: :) on the manager for work that extends beyond time to first draw: The API is @MainActor and has synchronous and asynchronous overloads. The task closure's result and thrown error propagate to the caller; a MetricManager.LaunchTaskError is reported through onTrackingError without interrupting the tracked work. Results appear as MetricResult.extendedLaunch . Use stable LaunchTaskID values and track only launch critical work. iOS 26 Compatibility For an app that still deploys to iOS 26, use an availability boundary: iOS/iPadOS 27: use MetricManager and consume both async report sequences. iOS/iPadOS 26 and earlier supported releases: use MXMetricManager.shared , an MXMetricManagerSubscriber , and the legacy payload callbacks. The legacy APIs remain the only documented branch with pastPayloads and pastDiagnosticPayloads . MXMetricManager is deprecated in iOS 27, so isolate it behind availability checks rather than mixing legacy payloads into the modern pipeline. Load [iOS 26 Compatibility](references/metrickit patterns.md ios 26 compatibility) for the full subscriber, legacy signpost, past payload, and extended launch patterns. Xcode Organizer Use Xcode Organizer to inspect Apple aggregated production metrics, hangs, crashes, and regressions before building a custom backend. Use direct MetricKit ingestion when the product needs custom correlation, retention, alerting, or integration with an existing observability system. Do not expect development device runs to reproduce the population, cadence, or aggregation of production reports. Scope Boundaries Task Use instead Reproduce a problem locally or record a detailed trace debugging instruments Diagnose retained objects or memory graph paths ios memgraph analysis Tune SwiftUI invalidation, identity, or scrolling code swiftui performance Study structured EnergyKit impact data energykit Design general logging and os signpost strategy swift logging MetricKit identifies production symptoms and trends. Route the actual code fix to the skill that owns the affected subsystem. Common Mistakes Mistake Correction Uploading directly in the sequence loop Encode and enqueue locally first; upload asynchronously later. Assuming every diagnostic event produces a report Treat diagnostics as sampled, system produced evidence. Looking for pastPayloads on MetricManager Keep legacy backfill only in the iOS 26 MXMetricManager branch. Parsing only known enum cases Preserve the raw report and use @unknown default . Using MXMetricManager.makeLogHandle in the iOS 27 branch Use manager.logHandle(category:) . Using paired extend/finish launch calls in the iOS 27 branch Use trackLaunchTask . Treating MetricKit aggregates as local traces Reproduce with Instruments and signposts. Review Checklist [ ] The iOS 27 branch starts at launch with one retained MetricManager and one consumer per report sequence. [ ] Every report is encoded and durably enqueued before analysis or upload. [ ] Diagnostic and metric switches use @unknown default . [ ] Unknown raw reports remain recoverable. [ ] Symbolication metadata and matching dSYMs are retained. [ ] Custom intervals use manager.logHandle(category:) and mxSignpost . [ ] Extended launch work uses trackLaunchTask . [ ] The iOS 26 MXMetricManager path is isolated behind availability checks. [ ] Production aggregates lead to a local Instruments investigation when appropriate. [ ] iOS 27 beta APIs have been rechecked and compiled with the shipping Xcode 27 SDK. References [MetricManager](https://sosumi.ai/documentation/metrickit/metricmanager) [Metric report sequence](https://sosumi.ai/documentation/metrickit/metricmanager/metricreports) [Diagnostic report sequence](https://sosumi.ai/documentation/metrickit/metricmanager/diagnosticreports) [MetricReport](https://sosumi.ai/documentation/metrickit/metricreport) [DiagnosticReport](https://sosumi.ai/documentation/metrickit/diagnosticreport) [MetricResult](https://sosumi.ai/documentation/metrickit/metricresult) [DiagnosticResult](https://sosumi.ai/documentation/metrickit/diagnosticresult) [CallStackTree](https://sosumi.ai/documentation/metrickit/callstacktree) [Monitoring app performance with MetricKit](https://sosumi.ai/documentation/metrickit/monitoring app performance with metrickit) [Analyzing app performance with MetricKit](https://sosumi.ai/documentation/metrickit/analyzing app performance with metrickit) [iOS & iPadOS 27 release notes](https://sosumi.ai/documentation/ios ipados release notes/ios ipados 27 release notes) [What's new in MetricKit (WWDC26)](https://sosumi.ai/videos/play/wwdc2026/222) [MetricKit Extended and Compatibility Patterns](references/metrickit patterns.md)