axiom-xcode-debugging

# Xcode Debugging

## Overview

Check build environment BEFORE debugging code. **Core principle** 80% of "mysterious" Xcode issues are environment problems (stale Derived Data, stuck simulators, zombie processes), not code bugs.

## Example Prompts

These are real questions developers ask that this skill is designed to answer:

#### 1. "My build is failing with 'BUILD FAILED' but no error details. I haven't changed anything. What's going on?"
→ The skill shows environment-first diagnostics: check Derived Data, simulator states, and zombie processes before investigating code

#### 2. "Tests passed yesterday with no code changes, but now they're failing. This is frustrating. How do I fix this?"
→ The skill explains stale Derived Data and intermittent failures, shows the 2-5 minute fix (clean Derived Data)

#### 3. "My app builds fine but it's running the old code from before my changes. I restarted Xcode but it still happens."
→ The skill demonstrates that Derived Data caches old builds, shows how deletion forces a clean rebuild

#### 4. "The simulator says 'Unable to boot simulator' and I can't run tests. How do I recover?"
→ The skill covers simulator state diagnosis with simctl and safe recovery patterns (erase/shutdown/reboot)

#### 5. "I'm getting 'No such module: SomePackage' errors after updating SPM dependencies. How do I fix this?"
→ The skill explains SPM caching issues and the clean Derived Data workflow that resolves "phantom" module errors

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## Red Flags — Check Environment First

If you see ANY of these, suspect environment not code:
- "It works on my machine but not CI"
- "Tests passed yesterday, failing today with no code changes"
- "Build succeeds but old code executes"
- "Build sometimes succeeds, sometimes fails" (intermittent failures)
- "Simulator stuck at splash screen" or "Unable to install app"
- Multiple xcodebuild processes (10+) older than 30 minutes

## Mandatory First Steps

**ALWAYS run these commands FIRST** (before reading code):

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