Debugging with AI: Fix Bugs Faster

Debugging can eat hours of your day. But with Claude as your debugging partner, you can identify root causes, understand complex stack traces, and fix bugs in fraction of the time. Here's the playbook.

The AI Debugging Workflow

1. Provide Complete Context

You: "I'm getting this error in production:
Error: Cannot read property 'map' of undefined
  at UserList.render (UserList.tsx:45)
  at App.tsx:120

Here's the component:
[paste code]

Here's what I've tried:
- Added null check (didn't help)
- Verified API returns data in development
- Issue only happens in production"

Claude: [Analyzes and identifies the real issue]

2. Systematic Problem Analysis

Claude helps you think through the problem methodically:

<span class="hljs-comment">// ❌ Before: Random debugging</span>
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">&#x27;here&#x27;</span>);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">&#x27;here2&#x27;</span>);
<span class="hljs-variable language_">console</span>.<span class="hljs-title function_">log</span>(<span class="hljs-string">&#x27;data&#x27;</span>, data); <span class="hljs-comment">// undefined - but why?</span>

<span class="hljs-comment">// ✅ After: Systematic approach with Claude</span>
<span class="hljs-title class_">You</span>: <span class="hljs-string">&quot;Walk me through debugging this step by step&quot;</span>

<span class="hljs-title class_">Claude</span>: <span class="hljs-string">&quot;Let&#x27;s debug systematically:

1. Check where data is set
2. Verify API response structure
3. Check for race conditions
4. Examine error boundaries
5. Review production vs development differences

Let&#x27;s start with #1...&quot;</span>

Common Debugging Scenarios

Scenario 1: Understanding Error Messages

You: "What does this error mean and how do I fix it?
TypeError: Cannot read properties of null (reading 'map')"

Claude: "This means you're trying to call .map() on null or undefined.
Common causes:
1. Data hasn't loaded yet (async issue)
2. API returned null instead of array
3. Optional chaining needed

Show me the code around line 45 and I'll identify the exact cause."

Scenario 2: Race Conditions

<span class="hljs-comment">// Bug: State update after unmount</span>
<span class="hljs-keyword">function</span> <span class="hljs-title function_">UserProfile</span>(<span class="hljs-params">{ userId }</span>) {
  <span class="hljs-keyword">const</span> [user, setUser] = <span class="hljs-title function_">useState</span>(<span class="hljs-literal">null</span>);

  <span class="hljs-title function_">useEffect</span>(<span class="hljs-function">() =&gt;</span> {
    <span class="hljs-title function_">fetchUser</span>(userId).<span class="hljs-title function_">then</span>(setUser); <span class="hljs-comment">// ❌ Might set state after unmount</span>
  }, [userId]);

  <span class="hljs-keyword">return</span> <span class="language-xml"><span class="hljs-tag">&lt;<span class="hljs-name">div</span>&gt;</span>{user?.name}<span class="hljs-tag">&lt;/<span class="hljs-name">div</span>&gt;</span></span>;
}

<span class="hljs-comment">// Ask Claude: &quot;Why am I getting &#x27;Can&#x27;t perform React state update on unmounted component&#x27;?&quot;</span>

<span class="hljs-comment">// Claude&#x27;s fix:</span>
<span class="hljs-keyword">function</span> <span class="hljs-title function_">UserProfile</span>(<span class="hljs-params">{ userId }</span>) {
  <span class="hljs-keyword">const</span> [user, setUser] = <span class="hljs-title function_">useState</span>(<span class="hljs-literal">null</span>);

  <span class="hljs-title function_">useEffect</span>(<span class="hljs-function">() =&gt;</span> {
    <span class="hljs-keyword">let</span> cancelled = <span class="hljs-literal">false</span>;

    <span class="hljs-title function_">fetchUser</span>(userId).<span class="hljs-title function_">then</span>(<span class="hljs-function"><span class="hljs-params">data</span> =&gt;</span> {
      <span class="hljs-keyword">if</span> (!cancelled) {
        <span class="hljs-title function_">setUser</span>(data);
      }
    });

    <span class="hljs-keyword">return</span> <span class="hljs-function">() =&gt;</span> {
      cancelled = <span class="hljs-literal">true</span>;
    };
  }, [userId]);

  <span class="hljs-keyword">return</span> <span class="language-xml"><span class="hljs-tag">&lt;<span class="hljs-name">div</span>&gt;</span>{user?.name}<span class="hljs-tag">&lt;/<span class="hljs-name">div</span>&gt;</span></span>;
}

Scenario 3: Performance Issues

You: "My app is slow when rendering 1000 items. Here's the component:
[paste code]"

Claude: "I see several performance issues:
1. No memoization - re-renders unnecessarily
2. Rendering all 1000 items at once
3. Expensive calculations on every render

Here's an optimized version:
[provides optimized code with virtualization]"

Scenario 4: Memory Leaks

<span class="hljs-comment">// Bug: Subscription not cleaned up</span>
<span class="hljs-keyword">function</span> <span class="hljs-title function_">ChatRoom</span>(<span class="hljs-params">{ roomId }</span>) {
  <span class="hljs-title function_">useEffect</span>(<span class="hljs-function">() =&gt;</span> {
    <span class="hljs-keyword">const</span> subscription = <span class="hljs-title function_">subscribeToRoom</span>(roomId);
    <span class="hljs-comment">// ❌ No cleanup!</span>
  }, [roomId]);
}

<span class="hljs-comment">// Claude identifies and fixes:</span>
<span class="hljs-keyword">function</span> <span class="hljs-title function_">ChatRoom</span>(<span class="hljs-params">{ roomId }</span>) {
  <span class="hljs-title function_">useEffect</span>(<span class="hljs-function">() =&gt;</span> {
    <span class="hljs-keyword">const</span> subscription = <span class="hljs-title function_">subscribeToRoom</span>(roomId);

    <span class="hljs-keyword">return</span> <span class="hljs-function">() =&gt;</span> {
      subscription.<span class="hljs-title function_">unsubscribe</span>(); <span class="hljs-comment">// ✅ Cleanup</span>
    };
  }, [roomId]);
}

Advanced Debugging Techniques

Network Issues

You: "API calls work in Postman but fail in my app with CORS errors"

Claude: "CORS errors mean the server isn't allowing requests from your domain.
Quick fixes:
1. Development: Use a proxy in vite.config.ts
2. Production: Configure server CORS headers

Here's the vite config:
[provides configuration]"

Build Issues

You: "Code works in dev but breaks in production build"

Claude: "Common causes:
1. Environment variables missing
2. Code splitting breaking imports
3. Minification breaking code
4. CSS class names being optimized away

Check:
- Are you using process.env correctly?
- Any dynamic imports?
- Show me your build config"

Complex State Bugs

<span class="hljs-comment">// Bug: Stale closure in useEffect</span>
<span class="hljs-keyword">function</span> <span class="hljs-title function_">Timer</span>(<span class="hljs-params"></span>) {
  <span class="hljs-keyword">const</span> [count, setCount] = <span class="hljs-title function_">useState</span>(<span class="hljs-number">0</span>);

  <span class="hljs-title function_">useEffect</span>(<span class="hljs-function">() =&gt;</span> {
    <span class="hljs-keyword">const</span> id = <span class="hljs-built_in">setInterval</span>(<span class="hljs-function">() =&gt;</span> {
      <span class="hljs-title function_">setCount</span>(count + <span class="hljs-number">1</span>); <span class="hljs-comment">// ❌ Always uses initial count value</span>
    }, <span class="hljs-number">1000</span>);
    <span class="hljs-keyword">return</span> <span class="hljs-function">() =&gt;</span> <span class="hljs-built_in">clearInterval</span>(id);
  }, []); <span class="hljs-comment">// Empty deps = stale closure</span>

  <span class="hljs-keyword">return</span> <span class="language-xml"><span class="hljs-tag">&lt;<span class="hljs-name">div</span>&gt;</span>{count}<span class="hljs-tag">&lt;/<span class="hljs-name">div</span>&gt;</span></span>;
}

<span class="hljs-comment">// Claude&#x27;s fix:</span>
<span class="hljs-keyword">function</span> <span class="hljs-title function_">Timer</span>(<span class="hljs-params"></span>) {
  <span class="hljs-keyword">const</span> [count, setCount] = <span class="hljs-title function_">useState</span>(<span class="hljs-number">0</span>);

  <span class="hljs-title function_">useEffect</span>(<span class="hljs-function">() =&gt;</span> {
    <span class="hljs-keyword">const</span> id = <span class="hljs-built_in">setInterval</span>(<span class="hljs-function">() =&gt;</span> {
      <span class="hljs-title function_">setCount</span>(<span class="hljs-function"><span class="hljs-params">c</span> =&gt;</span> c + <span class="hljs-number">1</span>); <span class="hljs-comment">// ✅ Functional update</span>
    }, <span class="hljs-number">1000</span>);
    <span class="hljs-keyword">return</span> <span class="hljs-function">() =&gt;</span> <span class="hljs-built_in">clearInterval</span>(id);
  }, []);

  <span class="hljs-keyword">return</span> <span class="language-xml"><span class="hljs-tag">&lt;<span class="hljs-name">div</span>&gt;</span>{count}<span class="hljs-tag">&lt;/<span class="hljs-name">div</span>&gt;</span></span>;
}

Effective Debugging Prompts

For Cryptic Errors

"I'm getting this error: [error message]
Context:
- Framework: [Next.js 14]
- What I was doing: [implementing auth]
- When it happens: [only on login]
- Stack trace: [full stack trace]
What's causing this and how do I fix it?"

For Unexpected Behavior

"My component isn't updating when props change.
Expected: User name updates immediately
Actual: Name stays the same until page refresh
Code: [paste component]
Parent component: [paste parent]"

For Performance Issues

"Page is slow with large datasets.
- Dataset size: 10,000 items
- What's slow: Initial render and filtering
- Already tried: useMemo on filter function
- Chrome DevTools shows: [screenshot or description]
Code: [paste component]"

Debugging Checklist

• Provided complete error message
• Included relevant code
• Described expected vs actual behavior
• Listed what you've already tried
• Shared environment details
• Included stack trace if available
• Noted when/where it happens
• Mentioned any patterns observed

Tools + AI = Super Debugging

Combine Claude with debugging tools:

1. Chrome DevTools: Find where it breaks
2. Claude: Understand why it breaks
3. Fix and verify

Example:
- DevTools shows component re-rendering 100x
- Ask Claude: "Why is this re-rendering constantly?"
- Claude identifies the issue: new object in props
- Apply fix: memoize the object

Conclusion

Debug faster with Claude by:

1. Providing complete context - Error, code, environment
2. Being systematic - Let Claude guide the investigation
3. Understanding root causes - Don't just patch symptoms
4. Learning patterns - Recognize similar bugs faster
5. Combining tools - AI + DevTools = powerful debugging

The goal isn't just fixing bugs—it's understanding them so you write better code that prevents them in the first place.