Telemetry

Quick Start

Use this skill to add lightweight app instrumentation that helps debug behavior without turning the codebase into a logging landfill. Prefer Apple's unified logging APIs and verify the events after a build/run loop.

Core Guidelines

• Prefer Logger from the OSLog framework for structured app logs.
• Give each feature a clear subsystem/category pair so runtime filtering stays easy.
• Log meaningful user and app lifecycle events: window opening, sidebar selection changes, menu commands, menu bar extra actions, sync/load milestones, and unexpected fallback paths.
• Keep info logs concise and stable. Use debug logs for noisy state details.
• Do not log secrets, auth tokens, personal data, or raw document contents.
• Add signposts only when measuring timing or performance spans; do not overinstrument by default.

Minimal Logger Pattern

import OSLog

private let logger = Logger(
  subsystem: Bundle.main.bundleIdentifier ?? "SampleApp",
  category: "Sidebar"
)

@MainActor
func selectItem(_ item: SidebarItem) {
  logger.info("Selected sidebar item: \(item.id, privacy: .public)")
  selection = item.id
}

Use feature-specific categories like Windowing, Commands, MenuBar, Sidebar, Sync, or Import so logs can be filtered quickly.

Workflow

1. Identify the behavior that needs observability.
   • Window open/close
   • Sidebar or inspector selection changes
   • Menu or keyboard command actions
   • Menu bar extra actions
   • Background load/sync/import events
   • Error and recovery paths
2. Add the smallest useful instrumentation.
   • Create one Logger per feature area or type.
   • Log action boundaries and key state transitions.
   • Prefer one high-signal line per user action over noisy value dumps.
3. Build and run the app.
   • Use build-run-debug for the build/run loop.
   • If script/build_and_run.sh exists, prefer ./script/build_and_run.sh --telemetry for live telemetry checks or ./script/build_and_run.sh --logs for broader process logs.
   • Exercise the UI or command path that should emit telemetry.
4. Read runtime logs and verify the event fired.
   • Use Console.app with a process/subsystem filter when that is the fastest manual check.
   • Use log stream --style compact --predicate 'process == "AppName"' for live terminal verification.
   • Prefer tighter predicates when you know the subsystem/category: log stream --style compact --predicate 'subsystem == "com.example.app" && category == "Sidebar"'
5. Tighten or remove instrumentation.
   • If the event fires, keep only the logs that remain useful for future debugging.
   • If it does not fire, move the log closer to the suspected control path and rerun.

Verification Checklist

• The app builds after telemetry changes.
• The relevant action emits exactly one clear log line or a small bounded sequence.
• The log can be filtered by process, subsystem, or category.
• No sensitive payloads are written to unified logs.
• Noisy temporary debug logs are removed or demoted before finishing.

Guardrails

• Do not use print as the primary app telemetry mechanism for macOS app code.
• Do not leave a dense trail of permanent debug logs around every state mutation.
• Do not claim an event is wired correctly until you have a concrete verification path through Console, log stream, or captured process output.
• If the debugging task is mostly about crash/backtrace analysis rather than action telemetry, switch to build-run-debug.