AEO Failure Patterns Skill

AEO Failure Patterns

Purpose: Recognize common errors and apply known fixes automatically. Uses hybrid architecture: core curated patterns + project-specific learned patterns.

Architecture

Core Patterns (in this SKILL.md):

20-30 curated patterns with high-confidence fixes
Portable across projects
Confidence ≥ 0.85 → Auto-fix

Project-Specific Patterns (in PAI memory):

Learned from human resolutions
$PAI_DIR/MEMORY/aeo-failure-patterns.json
Confidence ≥ 0.80 → Auto-fix

When to Use

Invoke when:

Error occurs during task execution
Test fails
Build fails
Runtime exception

Core Patterns

1. Module Not Found

Error Signature:

Error: Cannot find module 'module-name'
or
SyntaxError: Named export 'ExportName' not found

Fix:

# Check if module installed
ls node_modules | grep module-name

# If missing, install
npm install module-name

# If wrong import, check package.json exports
cat node_modules/module-name/package.json | grep exports

Confidence: 0.90

2. Type Error: Property Missing

Error Signature:

TypeError: Cannot read properties of undefined (reading 'propertyName')
or
Property 'propertyName' does not exist on type 'Type'

Fix:

// Add optional chaining
object?.propertyName

// Or add null check
if (object && object.propertyName) { ... }

// Or add type guard
if ('propertyName' in object) { ... }

Confidence: 0.85

3. Dependency Version Conflicts

Error Signature:

npm ERR! peer dep missing: module@version required by package@version
or
npm ERR! Conflicting peer dependency

Fix:

# Use --legacy-peer-deps flag
npm install --legacy-peer-deps

# Or use --force
npm install --force

# Or resolve manually
npm install module@required-version

Confidence: 0.80

4. Async Callback Timeout

Error Signature:

Error: Timeout - Async callback was not invoked within the 5000ms timeout

Fix:

// Add done callback
test('async test', (done) => {
  asyncFunction()
    .then(result => {
      expect(result).toBe(value)
      done()  // ← Required
    })
    .catch(err => {
      done(err)
    })
})

// Or use async/await
test('async test', async () => {
  const result = await asyncFunction()
  expect(result).toBe(value)
})

Confidence: 0.90

5. Stack Overflow (Maximum Call Stack)

Error Signature:

RangeError: Maximum call stack size exceeded

Fix:

// Likely infinite recursion - check base case

function recursive(data) {
  // ❌ Missing base case
  return recursive(data.processed())

  // ✅ Add base case
  if (data.isComplete()) return data
  return recursive(data.processed())
}

Confidence: 0.85

6. Permission Denied (File System)

Error Signature:

Error: EACCES: permission denied, open 'path/to/file'

Fix:

# Check file permissions
ls -la path/to/file

# If owned by different user, use sudo
sudo chown $USER:$USER path/to/file

# Or fix directory permissions
chmod 755 path/to/directory

Confidence: 0.95

7. Configuration File Not Found

Error Signature:

Error: ENOENT: no such file or directory, open '.env'
or
Config file not found: config.json

Fix:

# Copy example config
cp .env.example .env

# Or create from template
cat > .env << EOF
API_KEY=your-key-here
DATABASE_URL=your-database-url
EOF

Confidence: 0.90

8. Git Merge Conflicts

Error Signature:

Auto-merging file.txt
CONFLICT (content): Merge conflict in file.txt
Automatic merge failed; fix conflicts and commit

Fix:

# Find conflicted files
git status | grep "both modified"

# Edit file, resolve markers:
# <<<<<<< HEAD
# your changes
# =======
# their changes
# >>>>>>> branch-name

# After resolving:
git add file.txt
git commit

Confidence: 0.85

9. Unrelated Histories (Git)

Error Signature:

fatal: refusing to merge unrelated histories

Fix:

git merge branch-name --allow-unrelated-histories

Confidence: 0.95

10. Port Already in Use

Error Signature:

Error: listen EADDRINUSE: address already in use :::3000

Fix:

# Find process using port
lsof -i :3000

# Kill it
kill -9 <PID>

# Or use different port
PORT=3001 npm start

Confidence: 0.95

11. CORS Error

Error Signature:

Access to fetch at 'http://api.example.com' from origin 'http://localhost:3000' has been blocked by CORS policy

Fix:

// Server-side: Add CORS headers
import cors from 'cors'
app.use(cors())

// Or specific origin
app.use(cors({
  origin: 'http://localhost:3000'
}))

Confidence: 0.90

12. JSON Parse Error

Error Signature:

SyntaxError: Unexpected token < in JSON at position 0

Fix:

// Check response before parsing
const response = await fetch(url)
const text = await response.text()

// Check if HTML (error page) or JSON
if (text.startsWith('<')) {
  throw new Error('Received HTML instead of JSON')
}

const data = JSON.parse(text)

Confidence: 0.85

13. React Hydration Mismatch

Error Signature:

Warning: Text content did not match. Server: "X" Client: "Y"

Fix:

// Ensure server and client render same content
// Check for date(), Math.random(), etc.

// ❌ Wrong - different on server vs client
<div>{Date.now()}</div>

// ✅ Correct - use useEffect for client-only
<div>{typeof window !== 'undefined' && Date.now()}</div>

// Or use useEffect
useEffect(() => {
  setTimestamp(Date.now())
}, [])

Confidence: 0.85

14. WebSocket Connection Failed

Error Signature:

WebSocket connection to 'ws://localhost:3000' failed

Fix:

// Check if WebSocket server is running
// Add connection timeout
const ws = new WebSocket('ws://localhost:3000')

ws.onerror = (error) => {
  console.error('WebSocket error:', error)
}

ws.onclose = (event) => {
  if (event.code === 1006) {
    console.log('WebSocket closed abnormally - server may be down')
  }
}

Confidence: 0.80

15. Database Connection Pool Exhausted

Error Signature:

Error: Connection pool exhausted

Fix:

// Increase pool size
const pool = new Pool({
  max: 20,  // Increase from default
  idleTimeoutMillis: 30000,
  connectionTimeoutMillis: 2000,
})

// Or ensure connections are released
const client = await pool.connect()
try {
  await client.query('SELECT * FROM users')
} finally {
  client.release()  // ← Always release
}

Confidence: 0.90

16. YAML Parse Error

Error Signature:

YAMLException: bad indentation of a mapping entry

Fix:

# ❌ Wrong - inconsistent indentation
key:
  subkey: value
    subsubkey: value

# ✅ Correct - consistent indentation
key:
  subkey: value
  subsubkey: value

Confidence: 0.95

17. Cannot Read Headers After Sent

Error Signature:

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client

Fix:

// ❌ Wrong - sending response twice
app.get('/api/users', (req, res) => {
  res.json({ users: [] })
  res.json({ count: 0 })  // ← Error
})

// ✅ Correct - return after sending
app.get('/api/users', (req, res) => {
  res.json({ users: [], count: 0 })
  return  // ← Prevent further execution
})

// Or use if/else
app.get('/api/users', (req, res) => {
  if (error) {
    res.status(500).json({ error })
  } else {
    res.json({ users })
  }
})

Confidence: 0.90

18. NPM Install Hangs

Error Signature:

npm install hangs forever

Fix:

# Clear npm cache
npm cache clean --force

# Delete node_modules and package-lock.json
rm -rf node_modules package-lock.json

# Reinstall
npm install

Confidence: 0.85

19. Docker Container Exits Immediately

Error Signature:

docker run <image> # exits immediately

Fix:

# ❌ Wrong - no process keeping container alive
FROM node:18
WORKDIR /app
COPY package.json .
RUN npm install

# ✅ Correct - use CMD or ENTRYPOINT
FROM node:18
WORKDIR /app
COPY package.json .
RUN npm install
COPY . .
CMD ["npm", "start"]  # ← Keeps container alive

Confidence: 0.90

20. Test Environment Variables Missing

Error Signature:

ReferenceError: process.env is not defined

Fix:

// vite.config.js / jest.config.js
export default {
  test: {
    env: {
      process: { env: {} }  // ← Add process.env polyfill
    }
  }
}

// Or set in test setup
process.env.API_KEY = 'test-key'

Confidence: 0.90

Pattern Matching Flow

Error occurs → Extract message + stack trace + context
Match core patterns → If confidence ≥ 0.85 → Auto-fix
Match project patterns → Read $PAI_DIR/MEMORY/aeo-failure-patterns.json
Fuzzy match → If confidence ≥ 0.70 → Propose, ask confirmation
No match → Escalate to human

Max Retry Limit

Prevent infinite loops:

Same error + same fix → Max 2 attempts
After 2 failures → Escalate
Reset counter on different error

Learning New Patterns

When human resolves an error:

# Extract pattern from resolution
pattern = {
  error_signature: "Error message substring",
  context: { language, framework },
  fix: "Steps taken to fix",
  confidence: 0.50,  # Start low
  success_count: 0,
  failure_count: 0
}

# Write to memory
echo $pattern | jq -c '.' >> ~/.claude/MEMORY/aeo-failure-patterns.json

Promote to auto-fix:

3+ successes → Increase confidence to ≥ 0.80
Failures → Decrease confidence by 0.20
Below 0.50 → Remove from active patterns

Project Pattern Format

{
  "error_signature": "specific error message",
  "context": {
    "language": "javascript",
    "framework": "react"
  },
  "fix": "step-by-step fix instructions",
  "confidence": 0.85,
  "success_count": 5,
  "failure_count": 0,
  "last_seen": "2026-01-22T10:00:00Z"
}

Escalation

If no pattern matches or max retries reached:

❌ CANNOT AUTO-FIX - PATTERN NOT RECOGNIZED

Error: [error message]

Searched:
• 20 core patterns - no match
• 15 project patterns - no match

Action: Escalating to human for guidance.

Invoke aeo-escalation skill.

Agent Skills: AEO Failure Patterns

Install this agent skill to your local

Skill Files