Guarantees¶

Scheduler.guarantees() returns a per-platform truth table. UX should branch on it rather than assume parity.

Field	Android `WorkManager`	iOS 18 `BGTaskScheduler`	macOS 15 `NSBackgroundActivityScheduler`
`survivesProcessDeath`	true	true	true
`survivesReboot`	true	true	true
`survivesForceQuit`	true	false	true
`honoursWallClock`	approximate	false (hint only)	approximate
`supportsRetryBackoff`	true (native)	true (library-emulated)	true (library-emulated)
`cancelsInFlight`	true	false	true
`minimumPeriodicInterval`	15 min	15 min recommended	1 sec
`maxConcurrentTasks`	unbounded-ish	~1000	unbounded-ish

Read carefully:

survivesForceQuit = false on iOS. The single most important caveat. See Force-quit caveat (iOS).
honoursWallClock = false on iOS means earliestBeginDate is a hint — the system can defer indefinitely based on opaque heuristics (battery state, usage patterns, Low Power Mode).
cancelsInFlight = false on iOS means Scheduler.cancel(taskId) only kills pending requests; a worker already executing on iOS finishes whatever it was doing.

Branching UX on guarantees¶

val g = scheduler.guarantees()

if (!g.survivesForceQuit) {
    // iOS: educate the user.
    showToast("Open the app daily so we can sync.")
}

if (!g.honoursWallClock) {
    // iOS: don't promise a wall-clock cadence.
    label.text = "Syncs throughout the day"      // not "syncs every hour"
}

if (!g.cancelsInFlight) {
    // iOS: a Cancel button only stops *future* runs, not the current one.
    cancelButton.subtitle = "Stops future runs"
}

What's not in the table¶

isForeground — there's no notion of "foreground work" in v1 (Android setForeground lands as ExecutionHint.LongRunning in v2).
requiresCharging on Apple — Android honours WorkConstraints.requiresCharging natively via WorkManager. On iOS / macOS the library has no charging probe, so the field is silently ignored. Workers that need charging should check inside execute() and return WorkResult.Retry.
Anything observability-related — Scheduler.observe() is v2.

Network constraints — honoured everywhere¶

WorkConstraints.networkRequired is honoured on every platform, by different mechanisms:

Android — WorkManager refuses to dispatch the worker until the constraint is met. The OS holds it indefinitely.
iOS / macOS — a library-managed pre-execution gate, driven by reachable, waits up to min(5 s, budget / 4). On timeout the worker is short-circuited to WorkResult.Retry and the scheduler reschedules per the request's BackoffPolicy.

NetworkRequirement.Unmetered is honoured against ReachabilityStatus.isDataMetered == false (wifi/ethernet) on all platforms — Android maps to NetworkType.UNMETERED; Apple checks the metered axis directly. The legacy "downgrade Unmetered to Any on iOS" behaviour is gone. See Recipes → Require a network connection.