Beginner
Best Claude Prompt for Debug & Fix
Why Claude?
Claude excels at systematic error diagnosis — it reads stack traces carefully, identifies root causes rather than just symptoms, and explains WHY the bug exists, not just what to change. Critical for subtle logic bugs, race conditions, and cross-file issues.
Prompt Template
<role>
You are a senior debugger. Your job is to find the root cause of the bug — not just patch the symptom. Reason step by step before proposing a fix. Be honest about uncertainty.
</role>
<code_context>
Language: {{language}}
Relevant code:
{{code_snippet}}
</code_context>
<error>
{{error_message_or_stack_trace}}
</error>
<reproduction>
Steps to reproduce: {{reproduction_steps}}
Expected behavior: {{expected_behavior}}
Actual behavior: {{actual_behavior}}
</reproduction>
<instructions>
1. Identify the root cause. Explain the chain of events from code to error in plain English.
2. List any other places in the codebase that might have the same underlying issue.
3. Propose the minimal fix. Show only the changed lines with before/after diff format.
4. Explain why your fix resolves the root cause (not just the symptom).
5. Suggest one test case that would have caught this bug earlier.
</instructions> Example Output
Root cause: db.users.findOne() returns null when no record matches, but the code immediately accesses user.id on line 4 without a null check. This is a missing guard, not a DB error.
Chain of events: invalid userId → findOne returns null → null.id throws TypeError → unhandled → 500 response
Show full example
Before:
```
const user = await db.users.findOne({ id: userId });
const orders = await db.orders.find({ userId: user.id });
```
After:
```
const user = await db.users.findOne({ id: userId });
if (!user) throw new NotFoundError(`User ${userId} not found`);
const orders = await db.orders.find({ userId: user.id });
```
Test case that would have caught this: `it('returns 404 for unknown userId', async () => { const res = await request.get('/orders?userId=nonexistent'); expect(res.status).toBe(404); })`
Make it yours
Your Generated Prompt
Prompt copied! What's next?
Got your AI output? Make it better.
Paste what Claude generated into Coda One — free, no signup.
Tips for Better Results
Paste the full stack trace, not just the error message — line numbers and call frames are critical for Claude to pinpoint the issue. Include the reproduction steps even if they seem obvious.
Example (filled in)
<role>
You are a senior debugger. Your job is to find the root cause of the bug — not just patch the symptom. Reason step by step before proposing a fix. Be honest about uncertainty.
</role>
<code_context>
Language: TypeScript
Relevant code:
async function getUserOrders(userId: string) {
const user = await db.users.findOne({ id: userId });
const orders = await db.orders.find({ userId: user.id });
return orders;
}
</code_context>
<error>
TypeError: Cannot read properties of null (reading 'id')
at getUserOrders (src/orders/service.ts:4:45)
</error>
<reproduction>
Steps to reproduce: Call GET /orders with a userId that doesn't exist in the database
Expected behavior: Return 404 with "User not found"
Actual behavior: Crashes with TypeError
</reproduction>