WWDC 2025 - iOS 26 Background APIs Explained: BGContinuedProcessingTask Changes Everything

Understanding the Background Runtime Foundation

The App Lifecycle Flow

• Foreground State: App interface is active, receives full system resources and CPU time
• Background Transition: Process remains alive but enters suspended state by default
• Suspension Protection: System preserves battery life, privacy, and resources for foreground apps
• Resume Process: App returns to foreground through app switcher with system restoration

Core System Principles

• Energy Conservation: Every operation (CPU, GPU, network, Neural Engine) has battery cost
• Resource Management: System manages memory, CPU time, and network bandwidth prioritization
• Opportunistic Execution: Background runtime is discretionary, not guaranteed
• Coalesced Work: System batches background activities to minimize device wake cycles

The Five Pillars of Background Excellence

1. Efficient Resource Usage

• Minimize CPU cycles and memory footprint
• Defer non-critical tasks until device charging
• Keep operations lightweight and purpose-driven
• Monitor impact in Battery Settings for user transparency

2. Minimal System Impact

• Avoid bloated workloads that compete with foreground experience
• Prefer batch processing over continuous operations
• Respect system throttling and suspension signals
• Design discrete, targeted tasks rather than broad operations

3. Resilient Architecture

• Save incremental progress frequently
• Handle expiration signals promptly
• Design atomic operations that can resume from interruption
• Trust system scheduling for optimal resource allocation

4. Courteous Behavior

• Honor user preferences (Low Power Mode, Background App Refresh, Low Data Mode)
• Ensure value delivered proportional to resource consumption
• Respond to user intent when app removed from switcher
• Maintain transparency about background activities

5. Adaptive Design

• Account for dynamic conditions (network, CPU load, thermal state, battery level)
• Design tasks to pick up where they left off
• Clearly advertise task requirements to system
• Maintain flexibility for varying runtime opportunities

Background Task Categories and Implementation

App Refresh Tasks (BGAppRefreshTask)

Purpose: Silent content fetching based on usage patterns
Best For: Frequently used apps requiring fresh content on launch

Key Characteristics:

• System aligns scheduling with app usage history
• Higher scheduling probability for frequently used apps
• Automatic suspension when task completion closure returns

SwiftUI Implementation Pattern:

WindowGroup {
    ContentView()
}
.backgroundTask(.appRefresh("bundleID.appRefresh")) {
    await performContentRefresh()
}

Background Push Notifications

Purpose: Server-initiated content updates
Best For: Infrequent, irregular remote document updates

Key Characteristics:

• Push-based rather than pull-based updates
• Always considered discretionary by system
• Low priority delivery with coalescing for efficiency
• Respect user intent when app removed from switcher

Processing Tasks (BGProcessingTask)

Purpose: Complex background operations (ML models, database maintenance)
Best For: Resource-intensive tasks that can be deferred

Key Features:

• Support for network and power requirements
• Immediate registration required during app launch
• Configurable execution constraints for battery optimization

Implementation Pattern:

BGTaskScheduler.shared.register(
    forTaskWithIdentifier: "bundleID.processing",
    using: nil
) { task in
    handleProcessingTask(task as! BGProcessingTask)
}

// Configure requirements
let request = BGProcessingTaskRequest(identifier: "bundleID.processing")
request.requiresNetworkConnectivity = true
request.requiresExternalPower = true

Begin/End Background Tasks

Purpose: Complete in-flight work during background transition
Best For: Critical operations that cannot be interrupted (state saves, file cleanup)

Implementation Strategy:

var backgroundTaskID: UIBackgroundTaskIdentifier = .invalid

func handleCriticalWork() {
    backgroundTaskID = UIApplication.shared.beginBackgroundTask(withName: "Critical Task") {
        // Expiration handler
        UIApplication.shared.endBackgroundTask(self.backgroundTaskID)
        self.backgroundTaskID = .invalid
    }

    performCriticalWork()

    UIApplication.shared.endBackgroundTask(backgroundTaskID)
    backgroundTaskID = .invalid
}

iOS 26: Continued Processing Tasks

Revolutionary User-Initiated Background Processing

Purpose: Long-running tasks with system UI progress indication
Best For: Exports, uploads, complex processing initiated by explicit user action

Core Requirements

• Explicit User Initiation: Must start with button tap or gesture, never automatic
• Clear Goal Definition: Represents immediate, understandable objective
• Measurable Progress: System requires continuous progress reporting
• User Control: Users can monitor progress and cancel at any time

Implementation Architecture

1. Info.plist Configuration:

BGTaskSchedulerPermittedIdentifiers:
- com.yourapp.bundleid.userTask
- com.yourapp.bundleid.export.*  // Wildcard support

2. Dynamic Handler Registration:

func prepareForUserTask() {
    BGTaskScheduler.shared.register("com.yourapp.userTask") { task in
        let continuedTask = task as! BGContinuedProcessingTask

        var shouldContinue = true
        task.expirationHandler = {
            shouldContinue = false
        }

        // Progress reporting is mandatory
        task.progress.totalUnitCount = 100
        task.progress.completedUnitCount = 0

        while shouldContinue && hasWork {
            performWorkUnit()
            task.progress.completedUnitCount += 1
        }

        task.setTaskCompleted(success: shouldContinue)
    }
}

3. Task Submission with Strategy:

func submitUserInitiatedTask() {
    let request = BGContinuedProcessingTaskRequest(
        identifier: "com.yourapp.userTask",
        title: "Exporting Photos",
        subtitle: "Processing 147 items"
    )

    // Choose submission strategy
    request.strategy = .fail  // Fail if cannot start immediately
    // or .queue (default) for queued execution

    try? BGTaskScheduler.shared.submit(request)
}

Advanced Capabilities

Background GPU Access (iOS 26):

• Add background GPU capability in Xcode project settings
• Query BGTaskScheduler.shared.supportedResources at runtime
• System enforces resource requirements and rejects invalid requests
• Dynamic adaptation based on device capabilities

Quality of Service Management:

• Background tasks receive lower QoS compared to foreground
• System intelligently boosts priority when app returns to foreground
• Ensures smooth transition and responsive user experience

Development Best Practices

Pre-Development Questions

1. Initiation Source: User-initiated vs. system-discretionary?
2. Duration Classification: Short, medium, or long-running task?
3. Criticality Assessment: Essential for app state vs. enhancement feature?
4. User Interaction: Requires consent or input vs. autonomous operation?

Task Design Principles

• Atomic Operations: Each task performs single, well-defined function
• Resource Awareness: Understand and respect system constraints
• Progress Transparency: Provide meaningful progress updates for user-facing tasks
• Graceful Degradation: Handle interruption and resource limitations elegantly

System Integration

• Registration Timing: Register background tasks immediately during launch
• Handler Management: Use appropriate queues and threading for task execution
• Error Handling: Implement robust error handling and recovery mechanisms
• Resource Querying: Check device capabilities before requesting specialized resources

The evolution of iOS background runtime represents a sophisticated balance between user experience, system performance, and battery life.