Debugging with Claude Code

The login form submits but nothing happens.
Expected: Redirect to dashboard after successful login
Actual: Form clears but user stays on login page
No errors in console

TypeError: Cannot read properties of undefined (reading 'user')
    at AuthContext.tsx:45:23
    at renderWithHooks (react-dom.development.js:14985:18)

Look at the AuthContext component around line 45.
What's causing the undefined 'user' error?

I'm getting this error:
"ReferenceError: process is not defined"

The error occurs when I run the app in the browser.
Using Next.js 14 with App Router.

The shopping cart total doesn't update when I change quantities.
- Adding items works fine
- Removing items works fine
- Changing quantity shows the new number but total stays the same

The dashboard takes 5+ seconds to load.
It was fast before I added the recent activity feed.
Here's the component: src/components/RecentActivity.tsx

The export feature stopped working after updating to v2.0.
It was working in commit abc123.
Now it throws "Invalid file format" error.

Help me find when this bug was introduced.
The feature works in commit from last week (abc123).
It's broken in current main (def456).
Use git bisect to narrow it down.

The bug only happens sometimes.
Help me create a minimal reproduction case
that triggers it consistently.

Add strategic console.log statements to trace
the data flow through the payment processing pipeline.
I need to see where the discount calculation goes wrong.

The component re-renders infinitely.
I think it's a useEffect dependency issue.
Check src/components/UserProfile.tsx

Also check if any parent components might be
causing unnecessary re-renders.

The API returns 500 but only for certain users.
Check the error logs and identify the pattern.
Looking at src/app/api/users/[id]/route.ts

The Redux store has the correct data,
but the component shows stale values.
Check if the selector is memoized correctly.

I can't use a debugger in production.
Add conditional logging that only fires when:
- User ID is 12345
- Amount is over $100
- The discount code is "SPECIAL"

The API call works in Postman but fails in the app.
Compare the exact headers, body, and request format.
Check for any request interceptors or middleware.

The app slows down after extended use.
Help me identify potential memory leaks:
- Event listeners not being removed
- Subscriptions not being cancelled
- Large objects being held in closures

Help me write a test case that reproduces this bug
so we can verify the fix works.

Before we fix this, explain what's causing
the null reference at line 145.
I want to understand the root cause.

Let's fix the authentication bug first.
Don't change the validation logic yet -
we need to isolate whether auth is the problem.

Now that we've fixed it:
1. Run the existing tests
2. Add a test for this specific bug
3. Check for any related edge cases

I have a bug in [feature]. Here's what I know:
- Expected behavior: [...]
- Actual behavior: [...]
- Error message (if any): [...]
- When it started: [...]

Please investigate the relevant code and suggest
what might be causing this.

We've identified the bug is in the [module].
The issue happens between [step A] and [step B].
Look at the code flow and find exactly where
the data gets corrupted/lost/changed incorrectly.

I've applied the fix. Please:
1. Review the change for correctness
2. Check for edge cases I might have missed
3. Suggest any additional tests needed
4. Look for similar patterns elsewhere that might have the same bug

We fixed the immediate issue, but I want to
understand how this happened.
- Why wasn't this caught earlier?
- Are there similar patterns in the codebase?
- What can we do to prevent this type of bug?

Let me explain what this code is supposed to do,
step by step. Stop me if anything sounds wrong:

1. User clicks submit
2. Form data is collected into an object
3. We validate required fields
4. API call is made with the data
5. On success, we redirect to /dashboard

I've been staring at this for hours.
Please look at the authentication flow with fresh eyes.
Something obvious might be wrong that I'm missing.

Let's systematically check each component
in the data pipeline, from input to database:
1. Form submission
2. API route handler
3. Validation middleware
4. Database query
5. Response handling