axiom-background-processing

# Background Processing

## Overview

Background execution is a **privilege**, not a right. iOS actively limits background work to protect battery life and user experience. **Core principle**: Treat background tasks as discretionary jobs — you request a time window, the system decides when (or if) to run your code.

**Key insight**: Most "my task never runs" issues stem from registration mistakes or misunderstanding the 7 scheduling factors that govern execution. This skill provides systematic debugging, not guesswork.

**Energy optimization**: For reducing battery impact of background tasks, see `axiom-energy` skill. This skill focuses on task **mechanics** — making tasks run correctly and complete reliably.

**Requirements**: iOS 13+ (BGTaskScheduler), iOS 26+ (BGContinuedProcessingTask), Xcode 15+

## Example Prompts

Real questions developers ask that this skill answers:

#### 1. "My background task never runs. I register it, schedule it, but nothing happens."
→ The skill covers the registration checklist and debugging decision tree for "task never runs" issues

#### 2. "How do I test background tasks? They don't seem to trigger in the simulator."
→ The skill covers LLDB debugging commands and simulator limitations

#### 3. "My task gets terminated before it completes. How do I extend the time?"
→ The skill covers task types (BGAppRefresh 30s vs BGProcessing minutes), expiration handlers, and incremental progress saving

#### 4. "Should I use BGAppRefreshTask or BGProcessingTask? What's the difference?"
→ The skill provides decision tree for choosing the correct task type based on work duration and system requirements

#### 5. "How do I integrate Swift 6 concurrency with background task expiration?"
→ The skill covers withTaskCancellationHandler patterns for bridging BGTask expiration to structured concurrency

#### 6. "My background task works in development but not in production."
→ The skill covers the 7 scheduling factors, throttling behavior, and production