Editing Openai/691a5ca1-2b1c-8010-8cbd-8797f95aa8d9 (section)

=== Assistant: Short version: there’s no “secret” API that lets Core Motion wake your app and run arbitrary logic while you’re fully i… ===
Short version: there’s no “secret” API that lets Core Motion wake your app and run arbitrary logic while you’re fully in the background or terminated — at least not in a way that’s precise enough for a regulatory 4-hour driving limit, fully offline, and App-Review-safe.

But you can get closer than “pure manual start/stop” with a hybrid design.

I’ll break it into:
# What iOS actually allows here
# A realistic architecture for your use case
# How I’d model the “observable engine”
# What I’d ship given App Review + UX constraints

==== Key truths: ====
* CMMotionActivityManager.startActivityUpdates does not wake a suspended/terminated app. It only delivers events while your process is actually running (foreground or kept alive by some background mode).Apple Developer<ref>{{cite web|title=Apple Developer|url=https://developer.apple.com/documentation/coremotion/cmmotionactivitymanager/startactivityupdates%28to%3Awithhandler%3A%29|publisher=Apple Developer|access-date=2025-11-17}}</ref>
* Core Motion history (via queryActivityStarting(from:to:to:withHandler:)) can be queried when your app is brought back, giving you up to 7 days of activity segments (including .automotive).devfright.com<ref>{{cite web|title=devfright.com|url=https://www.devfright.com/how-to-use-the-cmmotionactivitymanager/|publisher=devfright.com|access-date=2025-11-17}}</ref>
* BGTaskScheduler (BGAppRefreshTask, BGProcessingTask) gives you opportunistic wake-ups, not “wake me right at hour 4 of driving” precision. iOS decides when to run your task based on usage, power, etc.Apple Developer<ref>{{cite web|title=Apple Developer|url=https://developer.apple.com/documentation/backgroundtasks/bgtaskscheduler|publisher=Apple Developer|access-date=2025-11-17}}</ref>
* Background modes (Location, Audio, VoIP, etc.) are heavily scoped. Apple expects you to actually be doing that foregroundly-reasonable use case (navigation, fitness tracking, turn-by-turn, etc.). Misusing them just to keep the app alive is very likely to get flagged.Apple Developer<ref>{{cite web|title=Apple Developer|url=https://developer.apple.com/documentation/xcode/configuring-background-execution-modes|publisher=Apple Developer|access-date=2025-11-17}}</ref>
* Even with the newer “continued processing” style APIs in iOS 26, Apple is focused on user-initiated, bounded tasks (exports, uploads, etc.), not open-ended sensing like “watch for 4 hours of future driving”.Apple Developer<ref>{{cite web|title=Apple Developer|url=https://developer.apple.com/videos/play/wwdc2025/227/|publisher=Apple Developer|access-date=2025-11-17}}</ref>

So:

: 

Your current manual Start/Stop approach is actually very in line with what Apple wants: user-initiated, explicit, and bounded.

==== Given your offline-first + no push requirements, I’d treat this as a hybrid of: ====
* Manual “Start/Stop Driving” (primary source of truth)
* Motion + Location (used for validation and correction, not as the sole trigger)
* Periodic BGTasks to reconcile history and send “late” notifications if needed

===== 1. User taps Start Driving - Start an in-app “session”: - drivingSession.startDate = Date() - enable background location with allowsBackgroundLocationUpdates = true and activityType = .automotiveNavigation (or .otherNavigation if review is picky) - start CMMotionActivityManager.startActivityUpdates on a background queue =====
# While alive (foreground or kept alive by location): - Your “engine” consumes: - Location updates (speed, GPS validity) - Motion activity (.automotive, .stationary, confidence) - It maintains an accumulatedDrivingSeconds counter for the active session.
# When accumulated driving reaches 4 hours: - Schedule a local notification via UNUserNotificationCenter. - (Optionally also schedule earlier “pre-break” notifications at e.g. 3h30.)
# When user taps Stop Driving: - Close that session in SwiftData, record endDate, total driving seconds. - Stop background location + stop motion updates.

This is essentially exactly what navigation / running apps do, just with different output.

: 

===== You can’t force iOS to keep you alive forever. So plan for: =====
* Suspended but not killed: you may still get some location wakeups; process them and let your engine tick forward. But you can’t depend on high-frequency updates.
* Killed (by system or user): everything stops. Here’s where Core Motion history + BGTasks come in.

On next relaunch (or BGTask wake):
# Use CMMotionActivityManager.queryActivityStarting(from:to:to:handler:) to fetch activity segments since the last time you reconciled.devfright.com<ref>{{cite web|title=devfright.com|url=https://www.devfright.com/how-to-use-the-cmmotionactivitymanager/|publisher=devfright.com|access-date=2025-11-17}}</ref>
# Filter segments where activity.automotive == true and confidence is .medium/.high.
# Reconstruct driving intervals and: - Merge them with your stored sessions (manual Start/Stop windows). - Adjust any session that looks “off” (e.g. user forgot to tap Start but you see 2h of automotive → you can offer to auto-fill it next time they open the app).
# If from that reconstruction you see: - “User crossed 4h of continuous driving X minutes ago and we didn’t notify”: - Send a late notification (“You’ve been driving for about 4 hours. Time for a break?”).

This is not perfect to the minute—but it’s honest, offline, and uses the tools Apple actually gives you.

===== You can register a BGAppRefreshTask: =====
* On sceneWillResignActive, schedule a refresh task for, say, 30–60 min in the future.
* In the task handler: - Run the same Core Motion history reconciliation. - Update SwiftData. - If you see they’re well past 4 hours (and no notification has fired yet), send one now.

You have to accept:
* BGTasks are not guaranteed to fire on schedule. They’re “when the system feels like it”.Apple Developer<ref>{{cite web|title=Apple Developer|url=https://developer.apple.com/documentation/backgroundtasks/bgtaskscheduler|publisher=Apple Developer|access-date=2025-11-17}}</ref>
* This is more “nudge the user if they forget the app exists”, not “tachograph-level compliance.”

So the real-time guarantee only exists while you’re alive under a background mode; outside of that, it’s “best effort”.

==== Your idea of a small aggregated engine is good — the trick is to design it so it’s pure and reusable, and you just plug it into whatever background runtime you can get. ====

Conceptually:

<syntaxhighlight lang="swift">actor DrivingEngine {
    struct Event {
        let date: Date
        let isDriving: Bool
        let speed: CLLocationSpeed?
    }

    private var currentSession: DrivingSession?
    private var accumulatedSeconds: TimeInterval = 0

    func handle(event: Event) -> DrivingUpdate {
        // Update state machine based on transitions
        // e.g. stationary -> driving, driving -> stopped, etc.
        // Use timestamps to accumulate driving time
    }

    func resume(from storedSession: DrivingSession?) {
        // Rehydrate from SwiftData / persisted state
    }
}

</syntaxhighlight>

Then you have different “front-ends” that feed events into it:
* Foreground: CMMotion + GPS didUpdateLocations.
* Background (while location is alive): same, but no UI.
* BGTask / app relaunch: synthetic events built from Core Motion history (queryActivityStarting) and maybe historical location, if you’re storing that.

Your SwiftUI view just observes some published view model that’s driven by this actor; in the background scenario you skip the UI part and just call the engine then schedule notifications.

Important: this engine doesn’t rely on timers; it operates only off timestamps from events, which works fine whether events are real-time or “I fetched a batch an hour later”.

==== If your requirements are: ====
* 100% offline
* accurate “4h” notifications
* App-Review-safe
* no push

Then:
'' Manual Start/Stop is the only ''reliable* core.
* Sensors (Core Motion + GPS speed) are helpers: - To auto-pause/resume the session while you’re alive - To reconcile missed time later - To show the user “we think you were driving Xh YYmin between A and B”.

What I would ship:
# Primary: the manual Start/Stop session pattern you already have.
# Secondary: - Use motion + GPS to auto-pause/resume during a session (e.g. if they’re obviously parked 20+ minutes, you auto-stop and prompt next time). - On app relaunch/BGTask, use Core Motion history to fill gaps and offer corrections (“We detected additional driving between 13:00 and 14:15, add to your log?”).
# Notifications: - Real-time: scheduled when session starts, kept accurate while background location keeps you alive. - Fallback: if BGTask or relaunch finds they already passed 4h, send a “late” reminder.

That gets you:
* Good UX (they don’t have to be perfect with Start/Stop).
* Honest technical constraints (you’re not fighting iOS background policy).
* A clean story for App Review: navigation/fitness-like background behavior initiated explicitly by the user, plus best-effort post-hoc detection.

If you want, next step we can sketch:
* A concrete DrivingSession SwiftData model
* A DrivingEngine actor with simple state transitions
* How to wire that into CLLocationManager + CMMotionActivityManager + BGTaskScheduler in Swift-concurrency style.