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Advanced debugging specialist for diagnosing and resolving code issues. Use when user encounters bugs, errors, unexpected behavior, or mentions debugging.
npx skill4agent add charon-fan/agent-playbook debugger# Check recent changes
git log --oneline -10
# Check error logs
tail -f logs/error.log
# Check environment
env | grep -i debug| Category | Symptoms | Investigation Steps |
|---|---|---|
| Null/Undefined | "Cannot read X of undefined" | Trace the variable origin |
| Type Errors | "X is not a function" | Check actual vs expected type |
| Async Issues | Race conditions, timing | Check promise handling, async/await |
| State Issues | Stale data, wrong state | Trace state mutations |
| Network | Timeouts, connection refused | Check endpoints, CORS, auth |
| Environment | Works locally, not in prod | Compare env vars, versions |
| Memory | Leaks, OOM | Profile memory usage |
| Concurrency | Deadlocks, race conditions | Check locks, shared state |
# Find recently modified files
find . -type f -mtime -1 -name "*.js" -o -name "*.ts" -o -name "*.py"
# Grep for error patterns
grep -r "ERROR\|FATAL\|Exception" logs/
# Search for suspicious patterns
grep -r "TODO\|FIXME\|XXX" src/
# Check for console.log left in code
grep -r "console\.log\|debugger" src/# Run with debug output
NODE_DEBUG=* node app.js
# Check syntax
node -c file.js
# Run tests in debug mode
npm test -- --inspect-brk# Run with pdb
python -m pdb script.py
# Check syntax
python -m py_compile script.py
# Verbose mode
python -v script.py# Race detection
go run -race main.go
# Debug build
go build -gcflags="-N -l"
# Profile
go test -cpuprofile=cpu.prof# When you don't know where the bug is:
def process():
step1()
step2()
step3()
step4()
# Comment out half:
def process():
step1()
# step2()
# step3()
# step4()
# If bug disappears, uncomment half of commented:
def process():
step1()
step2()
# step3()
# step4()
# Continue until you isolate the bug// Before (mysterious failure):
async function getUser(id: string) {
const user = await db.find(id);
return transform(user);
}
// After (with logging):
async function getUser(id: string) {
console.log('[DEBUG] getUser called with id:', id);
const user = await db.find(id);
console.log('[DEBUG] db.find returned:', user);
const result = transform(user);
console.log('[DEBUG] transform returned:', result);
return result;
}// Complex code with bug:
function processBatch(items, options) {
// 100 lines of complex logic
}
// Create minimal reproduction:
function processBatch(items, options) {
console.log('Items:', items.length);
console.log('Options:', options);
// Test with minimal data
return processBatch([items[0]], options);
}| Error | Likely Cause | Solution |
|---|---|---|
| Accessing property on null/undefined | Add null check, use optional chaining |
| Wrong type, shadowing | Check typeof, verify import |
| Syntax error | Check line before error, validate syntax |
| Import path wrong | Check relative path, verify file exists |
| Port already in use | Kill existing process, use different port |
| Service not running | Start service, check port |
| Request too slow | Increase timeout, check network |
python scripts/debug_report.py <error-message>references/checklist.mdreferences/patterns.mdreferences/errors.md