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+---
+name: debugging-strategies
+description: Master systematic debugging techniques, profiling tools, and root cause analysis to efficiently track down bugs across any codebase or technology stack. Use when investigating bugs, performance issues, or unexpected behavior.
+---
+
+# Debugging Strategies
+
+Transform debugging from frustrating guesswork into systematic problem-solving with proven strategies, powerful tools, and methodical approaches.
+
+## When to Use This Skill
+
+- Tracking down elusive bugs
+- Investigating performance issues
+- Understanding unfamiliar codebases
+- Debugging production issues
+- Analyzing crash dumps and stack traces
+- Profiling application performance
+- Investigating memory leaks
+- Debugging distributed systems
+
+## Core Principles
+
+### 1. The Scientific Method
+
+**1. Observe**: What's the actual behavior?
+**2. Hypothesize**: What could be causing it?
+**3. Experiment**: Test your hypothesis
+**4. Analyze**: Did it prove/disprove your theory?
+**5. Repeat**: Until you find the root cause
+
+### 2. Debugging Mindset
+
+**Don't Assume:**
+- "It can't be X" - Yes it can
+- "I didn't change Y" - Check anyway
+- "It works on my machine" - Find out why
+
+**Do:**
+- Reproduce consistently
+- Isolate the problem
+- Keep detailed notes
+- Question everything
+- Take breaks when stuck
+
+### 3. Rubber Duck Debugging
+
+Explain your code and problem out loud (to a rubber duck, colleague, or yourself). Often reveals the issue.
+
+## Systematic Debugging Process
+
+### Phase 1: Reproduce
+
+```markdown
+## Reproduction Checklist
+
+1. **Can you reproduce it?**
+   - Always? Sometimes? Randomly?
+   - Specific conditions needed?
+   - Can others reproduce it?
+
+2. **Create minimal reproduction**
+   - Simplify to smallest example
+   - Remove unrelated code
+   - Isolate the problem
+
+3. **Document steps**
+   - Write down exact steps
+   - Note environment details
+   - Capture error messages
+```
+
+### Phase 2: Gather Information
+
+```markdown
+## Information Collection
+
+1. **Error Messages**
+   - Full stack trace
+   - Error codes
+   - Console/log output
+
+2. **Environment**
+   - OS version
+   - Language/runtime version
+   - Dependencies versions
+   - Environment variables
+
+3. **Recent Changes**
+   - Git history
+   - Deployment timeline
+   - Configuration changes
+
+4. **Scope**
+   - Affects all users or specific ones?
+   - All browsers or specific ones?
+   - Production only or also dev?
+```
+
+### Phase 3: Form Hypothesis
+
+```markdown
+## Hypothesis Formation
+
+Based on gathered info, ask:
+
+1. **What changed?**
+   - Recent code changes
+   - Dependency updates
+   - Infrastructure changes
+
+2. **What's different?**
+   - Working vs broken environment
+   - Working vs broken user
+   - Before vs after
+
+3. **Where could this fail?**
+   - Input validation
+   - Business logic
+   - Data layer
+   - External services
+```
+
+### Phase 4: Test & Verify
+
+```markdown
+## Testing Strategies
+
+1. **Binary Search**
+   - Comment out half the code
+   - Narrow down problematic section
+   - Repeat until found
+
+2. **Add Logging**
+   - Strategic console.log/print
+   - Track variable values
+   - Trace execution flow
+
+3. **Isolate Components**
+   - Test each piece separately
+   - Mock dependencies
+   - Remove complexity
+
+4. **Compare Working vs Broken**
+   - Diff configurations
+   - Diff environments
+   - Diff data
+```
+
+## Debugging Tools
+
+### JavaScript/TypeScript Debugging
+
+```typescript
+// Chrome DevTools Debugger
+function processOrder(order: Order) {
+    debugger;  // Execution pauses here
+
+    const total = calculateTotal(order);
+    console.log('Total:', total);
+
+    // Conditional breakpoint
+    if (order.items.length > 10) {
+        debugger;  // Only breaks if condition true
+    }
+
+    return total;
+}
+
+// Console debugging techniques
+console.log('Value:', value);                    // Basic
+console.table(arrayOfObjects);                   // Table format
+console.time('operation'); /* code */ console.timeEnd('operation');  // Timing
+console.trace();                                 // Stack trace
+console.assert(value > 0, 'Value must be positive');  // Assertion
+
+// Performance profiling
+performance.mark('start-operation');
+// ... operation code
+performance.mark('end-operation');
+performance.measure('operation', 'start-operation', 'end-operation');
+console.log(performance.getEntriesByType('measure'));
+```
+
+**VS Code Debugger Configuration:**
+```json
+// .vscode/launch.json
+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "Debug Program",
+            "program": "${workspaceFolder}/src/index.ts",
+            "preLaunchTask": "tsc: build - tsconfig.json",
+            "outFiles": ["${workspaceFolder}/dist/**/*.js"],
+            "skipFiles": ["<node_internals>/**"]
+        },
+        {
+            "type": "node",
+            "request": "launch",
+            "name": "Debug Tests",
+            "program": "${workspaceFolder}/node_modules/jest/bin/jest",
+            "args": ["--runInBand", "--no-cache"],
+            "console": "integratedTerminal"
+        }
+    ]
+}
+```
+
+### Python Debugging
+
+```python
+# Built-in debugger (pdb)
+import pdb
+
+def calculate_total(items):
+    total = 0
+    pdb.set_trace()  # Debugger starts here
+
+    for item in items:
+        total += item.price * item.quantity
+
+    return total
+
+# Breakpoint (Python 3.7+)
+def process_order(order):
+    breakpoint()  # More convenient than pdb.set_trace()
+    # ... code
+
+# Post-mortem debugging
+try:
+    risky_operation()
+except Exception:
+    import pdb
+    pdb.post_mortem()  # Debug at exception point
+
+# IPython debugging (ipdb)
+from ipdb import set_trace
+set_trace()  # Better interface than pdb
+
+# Logging for debugging
+import logging
+logging.basicConfig(level=logging.DEBUG)
+logger = logging.getLogger(__name__)
+
+def fetch_user(user_id):
+    logger.debug(f'Fetching user: {user_id}')
+    user = db.query(User).get(user_id)
+    logger.debug(f'Found user: {user}')
+    return user
+
+# Profile performance
+import cProfile
+import pstats
+
+cProfile.run('slow_function()', 'profile_stats')
+stats = pstats.Stats('profile_stats')
+stats.sort_stats('cumulative')
+stats.print_stats(10)  # Top 10 slowest
+```
+
+### Go Debugging
+
+```go
+// Delve debugger
+// Install: go install github.com/go-delve/delve/cmd/dlv@latest
+// Run: dlv debug main.go
+
+import (
+    "fmt"
+    "runtime"
+    "runtime/debug"
+)
+
+// Print stack trace
+func debugStack() {
+    debug.PrintStack()
+}
+
+// Panic recovery with debugging
+func processRequest() {
+    defer func() {
+        if r := recover(); r != nil {
+            fmt.Println("Panic:", r)
+            debug.PrintStack()
+        }
+    }()
+
+    // ... code that might panic
+}
+
+// Memory profiling
+import _ "net/http/pprof"
+// Visit http://localhost:6060/debug/pprof/
+
+// CPU profiling
+import (
+    "os"
+    "runtime/pprof"
+)
+
+f, _ := os.Create("cpu.prof")
+pprof.StartCPUProfile(f)
+defer pprof.StopCPUProfile()
+// ... code to profile
+```
+
+## Advanced Debugging Techniques
+
+### Technique 1: Binary Search Debugging
+
+```bash
+# Git bisect for finding regression
+git bisect start
+git bisect bad                    # Current commit is bad
+git bisect good v1.0.0            # v1.0.0 was good
+
+# Git checks out middle commit
+# Test it, then:
+git bisect good   # if it works
+git bisect bad    # if it's broken
+
+# Continue until bug found
+git bisect reset  # when done
+```
+
+### Technique 2: Differential Debugging
+
+Compare working vs broken:
+
+```markdown
+## What's Different?
+
+| Aspect       | Working         | Broken          |
+|--------------|-----------------|-----------------|
+| Environment  | Development     | Production      |
+| Node version | 18.16.0         | 18.15.0         |
+| Data         | Empty DB        | 1M records      |
+| User         | Admin           | Regular user    |
+| Browser      | Chrome          | Safari          |
+| Time         | During day      | After midnight  |
+
+Hypothesis: Time-based issue? Check timezone handling.
+```
+
+### Technique 3: Trace Debugging
+
+```typescript
+// Function call tracing
+function trace(target: any, propertyKey: string, descriptor: PropertyDescriptor) {
+    const originalMethod = descriptor.value;
+
+    descriptor.value = function(...args: any[]) {
+        console.log(`Calling ${propertyKey} with args:`, args);
+        const result = originalMethod.apply(this, args);
+        console.log(`${propertyKey} returned:`, result);
+        return result;
+    };
+
+    return descriptor;
+}
+
+class OrderService {
+    @trace
+    calculateTotal(items: Item[]): number {
+        return items.reduce((sum, item) => sum + item.price, 0);
+    }
+}
+```
+
+### Technique 4: Memory Leak Detection
+
+```typescript
+// Chrome DevTools Memory Profiler
+// 1. Take heap snapshot
+// 2. Perform action
+// 3. Take another snapshot
+// 4. Compare snapshots
+
+// Node.js memory debugging
+if (process.memoryUsage().heapUsed > 500 * 1024 * 1024) {
+    console.warn('High memory usage:', process.memoryUsage());
+
+    // Generate heap dump
+    require('v8').writeHeapSnapshot();
+}
+
+// Find memory leaks in tests
+let beforeMemory: number;
+
+beforeEach(() => {
+    beforeMemory = process.memoryUsage().heapUsed;
+});
+
+afterEach(() => {
+    const afterMemory = process.memoryUsage().heapUsed;
+    const diff = afterMemory - beforeMemory;
+
+    if (diff > 10 * 1024 * 1024) {  // 10MB threshold
+        console.warn(`Possible memory leak: ${diff / 1024 / 1024}MB`);
+    }
+});
+```
+
+## Debugging Patterns by Issue Type
+
+### Pattern 1: Intermittent Bugs
+
+```markdown
+## Strategies for Flaky Bugs
+
+1. **Add extensive logging**
+   - Log timing information
+   - Log all state transitions
+   - Log external interactions
+
+2. **Look for race conditions**
+   - Concurrent access to shared state
+   - Async operations completing out of order
+   - Missing synchronization
+
+3. **Check timing dependencies**
+   - setTimeout/setInterval
+   - Promise resolution order
+   - Animation frame timing
+
+4. **Stress test**
+   - Run many times
+   - Vary timing
+   - Simulate load
+```
+
+### Pattern 2: Performance Issues
+
+```markdown
+## Performance Debugging
+
+1. **Profile first**
+   - Don't optimize blindly
+   - Measure before and after
+   - Find bottlenecks
+
+2. **Common culprits**
+   - N+1 queries
+   - Unnecessary re-renders
+   - Large data processing
+   - Synchronous I/O
+
+3. **Tools**
+   - Browser DevTools Performance tab
+   - Lighthouse
+   - Python: cProfile, line_profiler
+   - Node: clinic.js, 0x
+```
+
+### Pattern 3: Production Bugs
+
+```markdown
+## Production Debugging
+
+1. **Gather evidence**
+   - Error tracking (Sentry, Bugsnag)
+   - Application logs
+   - User reports
+   - Metrics/monitoring
+
+2. **Reproduce locally**
+   - Use production data (anonymized)
+   - Match environment
+   - Follow exact steps
+
+3. **Safe investigation**
+   - Don't change production
+   - Use feature flags
+   - Add monitoring/logging
+   - Test fixes in staging
+```
+
+## Best Practices
+
+1. **Reproduce First**: Can't fix what you can't reproduce
+2. **Isolate the Problem**: Remove complexity until minimal case
+3. **Read Error Messages**: They're usually helpful
+4. **Check Recent Changes**: Most bugs are recent
+5. **Use Version Control**: Git bisect, blame, history
+6. **Take Breaks**: Fresh eyes see better
+7. **Document Findings**: Help future you
+8. **Fix Root Cause**: Not just symptoms
+
+## Common Debugging Mistakes
+
+- **Making Multiple Changes**: Change one thing at a time
+- **Not Reading Error Messages**: Read the full stack trace
+- **Assuming It's Complex**: Often it's simple
+- **Debug Logging in Prod**: Remove before shipping
+- **Not Using Debugger**: console.log isn't always best
+- **Giving Up Too Soon**: Persistence pays off
+- **Not Testing the Fix**: Verify it actually works
+
+## Quick Debugging Checklist
+
+```markdown
+## When Stuck, Check:
+
+- [ ] Spelling errors (typos in variable names)
+- [ ] Case sensitivity (fileName vs filename)
+- [ ] Null/undefined values
+- [ ] Array index off-by-one
+- [ ] Async timing (race conditions)
+- [ ] Scope issues (closure, hoisting)
+- [ ] Type mismatches
+- [ ] Missing dependencies
+- [ ] Environment variables
+- [ ] File paths (absolute vs relative)
+- [ ] Cache issues (clear cache)
+- [ ] Stale data (refresh database)
+```
+
+## Resources
+
+- **references/debugging-tools-guide.md**: Comprehensive tool documentation
+- **references/performance-profiling.md**: Performance debugging guide
+- **references/production-debugging.md**: Debugging live systems
+- **assets/debugging-checklist.md**: Quick reference checklist
+- **assets/common-bugs.md**: Common bug patterns
+- **scripts/debug-helper.ts**: Debugging utility functions