Bugs & Logic Errors

Focus on significant bugs that would cause runtime failures. Avoid nitpicks.

Checks

• Null/Undefined Access: Missing guards before accessing properties
• Off-by-One Errors: Incorrect loop bounds, slice indices
• Race Conditions: Concurrent access without synchronization
• Resource Leaks: Unclosed files, connections, subscriptions, event listeners
• Error Handling Gaps: Unhandled promise rejections, swallowed exceptions
• Infinite Loops: Missing base cases, unreachable break conditions
• State Mutation: Unexpected side effects, mutating shared state

Output Format

For each issue, return structured output with diff-style fix:

### 🐛 {{issue_title}}

**Location:** `{{file}}:{{line}}`
**Confidence:** {{score}}/100

**Problem:**
{{reason}}

**Current Code:**
```{{language}}
{{problematic_code}}

Suggested Fix:

- {{old_line}}
+ {{new_line}}

Why this fix works: {{explanation}}

## Example Output

### 🐛 Null reference on user object

**Location:** `src/api/users.ts:45`
**Confidence:** 95/100

**Problem:**
Accessing `user.email` without null check. Will throw if `findUser` returns null.

**Current Code:**
```typescript
const user = await findUser(id);
sendEmail(user.email);  // 💥 Throws if user is null

Suggested Fix:

  const user = await findUser(id);
+ if (!user) {
+   throw new NotFoundError(`User ${id} not found`);
+ }
  sendEmail(user.email);

Why this fix works: Early return with explicit error prevents runtime crash and provides meaningful error message.