Cursor Debug Mode — AI-Powered Debugging

Debugging is where most developers spend a disproportionate amount of time. Cursor's AI integration significantly reduces this time — not by magically fixing everything, but by eliminating the boring parts of debugging: searching docs, decoding cryptic error messages, and writing repetitive error-handling boilerplate. This guide covers the complete debugging workflow in Cursor.

What You'll Learn

• How Cursor's error lens and inline fix suggestions work
• The optimal workflow for using @ to reference errors
• How to get Cursor to explain terminal errors
• Debugging TypeScript, Python, and JavaScript errors
• Tips for complex bugs that require more than a one-shot fix

Error Lens and Inline Suggestions

Cursor includes an error lens that highlights errors inline in your code — similar to how VS Code highlights TypeScript errors, but with an additional AI layer.

When you hover over a highlighted error, you see:

1. The standard error message
2. An "Ask Cursor" button (or Cmd+. / Ctrl+.)

Clicking this opens an inline AI suggestion panel directly in the editor, showing a proposed fix for the error. You can accept, modify, or reject it.

For TypeScript errors specifically:

• Type mismatches are usually fixable with one click
• Missing properties get auto-completed
• null / undefined handling suggestions are contextually accurate

When inline suggestions fall short: Inline suggestions work best for single-point errors. For errors caused by a chain of incorrect logic, you need to use Composer or Chat instead.

Using @ to Reference Error Messages

The @ syntax in Cursor chat lets you reference specific things. For debugging, the most useful ones are:

@file:filename — Reference a specific file so Cursor has its full content as context

#selection — When you select code in the editor and open chat, Cursor includes the selection automatically

Pasting errors directly — For terminal errors, paste the full error output directly into chat (no special @ needed)

The optimal debugging prompt structure:

Here is the error:
[paste the full error message and stack trace]

Context: I am trying to [what you were doing].

The relevant code is in @file:src/api/users.ts

What is causing this and how should I fix it?

This gives Cursor:

• The exact error (not your interpretation of it)
• What you were doing (intent helps with diagnosis)
• The relevant file for context

Terminal Error Workflow

When a terminal command fails, the full error output appears in Cursor's integrated terminal. Here is the fastest workflow:

1. Copy the terminal error output (select all, Ctrl+C or Cmd+C)

2. Open Cursor Chat (Ctrl+L or Cmd+L)

3. Paste and ask:

   This error appeared when I ran `npm run build`:
   
   [pasted error output]
   
   What is the problem and what do I need to change?
   

4. Cursor diagnoses and suggests. It will tell you which file to change and what to change.

5. Use Composer if multi-file. If the fix requires changes to multiple files, open Composer (Ctrl+I) and ask it to implement the fix.

🇮🇳 India Note: Many Indian developers learn from tutorials that use slightly different package versions or configurations. Cursor is particularly good at explaining "version mismatch" errors — the kind you get when following a tutorial written for Next.js 13 but running Next.js 15. These errors have consistent patterns that Cursor handles well.

Debugging TypeScript Errors

TypeScript errors are the most common source of Cursor debugging sessions. Common categories and how Cursor handles them:

Type mismatch:

Type 'string | undefined' is not assignable to type 'string'

Cursor suggestion: add null check, use optional chaining (?.), or use non-null assertion (and will explain when each is appropriate).

Missing property:

Property 'userId' does not exist on type 'Request'

Cursor suggestion: extend the type interface, or use request.user?.id depending on your auth setup.

Incompatible types between libraries: When you get errors at the boundary between two libraries (e.g., React query types and your API types), Cursor is good at suggesting adapter functions or type assertions.

How to prompt for TypeScript errors:

TypeScript error:
Property 'user' does not exist on type 'Request'

I am using Express with Passport.js authentication.
File is @file:src/middleware/auth.ts

How do I fix this type error properly (without using `any`)?

The "without using any" constraint is important — otherwise Cursor may suggest the quick but wrong solution.

Debugging Python Errors

Python errors tend to be more runtime-focused. Useful debugging prompts:

For AttributeError or KeyError:

Runtime error in my FastAPI route:
AttributeError: 'NoneType' object has no attribute 'id'

Full traceback:
[paste traceback]

The route code is in @file:api/routes/users.py
The database model is in @file:api/models/user.py

Where is the None coming from and how should I handle it?

For async errors in Python:

RuntimeError: This event loop is already running
Context: I am trying to call an async function from a sync context.
File: @file:tasks/background_task.py
How do I fix the event loop issue?

Debugging JavaScript/React Errors

For React errors, the browser console error is the most important artifact:

React error:
Cannot update a component (`App`) while rendering a different component (`UserCard`).

I am calling setState inside the render function of UserCard.
Relevant component: @file:src/components/UserCard.jsx

How do I restructure this to fix the error?

For useEffect dependency warnings:

Warning: React Hook useEffect has a missing dependency: 'fetchData'.
Either include it or remove the dependency array — react-hooks/exhaustive-deps

I don't want to re-run the effect every time fetchData changes (it's a different function reference each render).
@file:src/hooks/useUserData.js

What is the correct pattern here?

Complex Bugs: Multi-Session Approach

For hard bugs that do not have an obvious cause, a structured multi-step approach works better than asking Cursor for a one-shot fix:

1. First prompt: gather evidence

   This bug: [describe behavior]. I cannot reproduce it consistently.
   Help me add strategic logging to narrow down where it is happening.
   Relevant files: @file:service.py, @file:api.py
   

2. Run with logging, collect output

3. Second prompt: analyze evidence

   After adding logging, here is what I see when the bug occurs:
   [paste log output]
   What does this tell us about the cause?
   

4. Third prompt: implement fix

   Based on the diagnosis, implement the fix.
   

This iterative approach uses Cursor as a debugging partner, not a magic fix machine.

Official Resources

• Cursor Documentation — Full feature reference
• Cursor Error Handling Guide — Debugging-specific docs
• TypeScript Docs — Reference for TypeScript errors
• React Error Reference — React error codes and explanations
• Cursor Forum — Community debugging tips