Apple Three-Piece Analytics

When to invoke

• Starting a new App and deciding on an analytics SDK.
• Evaluating Firebase / TelemetryDeck / Mixpanel / Amplitude / Sentry.
• Writing PrivacyInfo.xcprivacy.
• User asks "what metrics should I track", "what can I see without a third-party SDK".

Default decisions

v1 uses the Apple three-piece set

macOS caveat: MetricKit on macOS yields a reduced payload set compared to iOS (some payload types are iOS-only, e.g. MXAppLaunchMetric). For mac-heavy apps, lean more on App Store Connect Analytics + targeted OSSignposter traces.

| Game Center (if it's a game) | Leaderboards / achievement completion / peer-player comparison | Game Center API / Game Center app |

Privacy / Manifest

• `PrivacyInfo.xcprivacy` is a required deliverable (hard App Store submission requirement).
• Because no third-party SDK, no IDFA, no PII are collected, the manifest content is very minimal.
• No ATT prompt needed (no IDFA use case).
• CloudKit / Game Center's user-facing privacy notices are handled at the system layer by Apple; the App only needs to declare data usage in PrivacyInfo.

What's not covered (explicitly accepted)

• Micro-behaviour streams like "which button was tapped" or "how long was spent on a screen" are not covered by the three-piece set.
• Confirm v1 doesn't need to answer these questions; deviate if it does.

Rationale

• At solo / small-team scale, the three pieces cover most key questions (installs / retention / performance / crashes / player comparisons).
• No third-party SDK → no ATT, no PrivacyInfo additions, small build size, and the privacy claim is verifiable by readers via grep on import.
• Positive for a public-repo showcase ("no third-party tracking" is a credible commitment).

Deviation considerations

Adopt TelemetryDeck (privacy-friendly first)

• Trigger: actually need the micro-behaviour stream of "which button, where do users get stuck".
• Priority: TelemetryDeck > Firebase (the latter has heavier privacy burden, needs ATT, and many PrivacyInfo entries).
• How to integrate: swap in the TrackingSink implementation via telemetry-facade-pattern; call sites change nothing.

Adopt Sentry / Crashlytics

• Trigger: MetricKit MXDiagnosticPayload persistence still isn't enough for the incident workflow.
• Cost: third-party SDK, extra PrivacyInfo entries, build size.

Verification checklist

• PrivacyInfo.xcprivacy exists and passes App Store Connect validation.
• No import Firebase* / import Sentry / import Amplitude, etc.
• MetricKit subscription is wired (MXMetricManager.shared.add(...)).
• Game Center entitlement aligns with leaderboard / achievement definitions (for games).

Related skills

• telemetry-facade-pattern: the sink implementations for each piece.
• oslog-logger-defaults: MetricKit payloads persist via OSLog.
• apple-public-repo-security: "no PII / no third-party SDK" is one of the public-repo commitments.