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How to Use ChatGPT to Debug Code: A Practical Guide

A practical guide to using ChatGPT to debug code - the prompt patterns that work, the security trap most tutorials skip, and the cases where it just lies.

8 min readIntermediate

Here’s something most debugging tutorials won’t tell you: when you ask ChatGPT to debug code, roughly 1 in 5 of the packages it suggests installing might not actually exist. A March 2025 research paper found that across 576,000 generated Python and JavaScript code samples, recommended packages didn’t exist roughly 20% of the time. Attackers are now registering those phantom names as malware.

That’s the backdrop for this guide. ChatGPT is genuinely good at debugging – when you use it right. Here’s how to actually do that, plus the trap nobody warns you about.

Why the standard “paste code, ask for fix” approach fails

Most tutorials show the same workflow: paste your broken function, ask “why doesn’t this work,” accept the fix. It works for typos and null checks. It falls apart the moment your bug isn’t local to the code you pasted.

Two reasons. First, to use ChatGPT as a troubleshooting tool you need at least a clue where the offending code is – pasting thousands of lines is impractical, and the web version can’t troubleshoot well without a human who knows the codebase guiding it. Second, ChatGPT will not reason without prompting – if you pursue a piece of code that isn’t right for the task, it lets you, because as a language model it can’t know your assumptions are flawed and won’t try to correct them.

So if you tell it “this loop is wrong, fix the loop,” it will fix the loop – even when the real bug is upstream in how you built the input. You’ll get a confident answer to the wrong question.

Four prompt patterns that actually find bugs

Skip the “please help me debug this” opener. These four patterns are what consistently work in practice.

1. The rubber-duck prompt

Don’t ask for a fix. Ask ChatGPT to walk through the code line by line and tell you what each variable holds at each step. You’re using it as a tracer, not an oracle. Bugs surface when the model’s narration diverges from what you expected to happen.

2. The minimal-repro prompt

Strip the failing case down to a 10-20 line snippet before pasting. Give ChatGPT only the function plus a sample input and the expected vs. actual output. ChatGPT is excellent at troubleshooting small snippets like methods or whole classes, but for problems requiring many lines of code it may not be the best tool.

3. The hypothesis-first prompt

State your theory before asking. “I think the issue is that pandas is treating this column as object dtype instead of int – verify or disprove this.” This forces ChatGPT into critique mode instead of generation mode. Generation mode is where it makes things up.

4. The package-verification prompt

If the fix involves a library you haven’t heard of, immediately ask: “Does this package exist on PyPI/npm as of your knowledge cutoff? What’s the official repository URL?” More on why this matters below.

The security trap no debugging tutorial mentions

This is the section other guides skip. “Slopsquatting” was coined by Python Software Foundation developer-in-residence Seth Larson, as a play on “typosquatting” – registering slightly misspelled versions of legitimate package names. The slopsquatting twist: attackers don’t wait for typos. They wait for ChatGPT to invent a plausible-sounding package, then register that name on PyPI or npm with malicious code inside.

The repeatability is the real problem. Researchers tested 16 code-generation AI models including ChatGPT in a USENIX Security 2025 study covering 576,000 code samples – almost 20% recommended non-existent packages. But the finding that makes this an actual attack surface: 43% of those hallucinated package names appeared in every single one of 10 re-runs. Same prompt, same fake package, every time. An attacker only needs to observe the model once to know exactly what name to squat.

How often does this happen with ChatGPT specifically? Commercial models like GPT-4 and GPT-4 Turbo hallucinated packages at about a 5.2% rate, while open-source models averaged 21.7%. Lower, but not zero. And 38% of the non-existent names echoed real libraries with similar naming patterns, 13% were simple typos, and the remaining 51% were pure fabrications.

The proof-of-concept is unsettling. In early 2024, security researcher Bar Lanyado noticed AI models repeatedly hallucinating a Python package called huggingface-cli (the real install is pip install -U "huggingface_hub[cli]"). He uploaded an empty package under that name to PyPI – it got more than 30,000 authentic downloads in three months, and Alibaba had copy-pasted the hallucinated install command into the README of one of their public repositories.

Pro tip: before running any pip install or npm install that ChatGPT suggested, open the official registry page for that package in your browser. Check the publish date, weekly download count, and GitHub link. A package with 50 downloads and a creation date from last week is a red flag – especially if ChatGPT confidently described it as “a popular library.”

Real example: the pandas KeyError that ChatGPT almost solved wrong

Here’s a debugging session from earlier this year. The code threw a KeyError on a salary column:

import pandas as pd

df = pd.read_csv('payroll_export.csv')
avg = df.groupby('Position')['Salary'].mean()
print(avg)
# KeyError: 'Salary'

The naive prompt – “why does this throw KeyError” – got the obvious answer: the column name is wrong. ChatGPT suggested calling df.columns to inspect. Useful but generic.

The hypothesis-first prompt got further. “I think the CSV has ‘salary’ lowercase but my code expects ‘Salary’ capitalized – confirm or refute by writing code that checks for case-insensitive column matches and shows me which it found.” ChatGPT generated a one-liner using df.columns.str.lower() that immediately surfaced the real culprit: the export had a trailing space – 'salary ' – not just casing. A whitespace bug, not a casing bug.

Without the hypothesis prompt, ChatGPT would’ve cheerfully “fixed” it by changing ‘Salary’ to ‘salary’ and the KeyError would’ve reappeared in production a week later.

Pro tips most guides miss

  • Use Advanced Data Analysis (formerly Code Interpreter) when you can.Running GPT-4 in Code Interpreter mode drops hallucination rates on multi-step reasoning from under 10% to under 1%. When ChatGPT actually executes your code, it can’t lie about the output – it sees the real error.
  • Lower the temperature if you’re using the API. As of 2025, research confirms that lower temperature settings (less randomness) reduce hallucination rates. The catch: the ChatGPT web UI doesn’t expose temperature at all. Only the API does. If you’re debugging via the chat interface, you’re stuck at the default.
  • Open a new chat for each bug. Long sessions accumulate wrong context. Once you’ve fed ChatGPT a bad assumption, it keeps building on it – start fresh when a session starts going in circles.
  • Ask it to bet. “On a scale of 1-10, how confident are you this is the bug?” Forcing a confidence number sometimes pulls out hedging the model would otherwise hide. Not a perfect signal, but a cheap sanity check.

One last note on why all of this matters. According to OpenAI’s own research, “Language models hallucinate because training rewards guessing over acknowledging uncertainty” – the model learned that confidently completing sentences gets positive feedback, while saying “I don’t know” often doesn’t. You can read more about this on OpenAI’s own writeup, and the package-hallucination research is on arXiv. Debugging with ChatGPT isn’t about trusting it. It’s about structuring prompts so it can’t bluff.

FAQ

Is ChatGPT or GitHub Copilot better for debugging?

Different tools, different jobs. Copilot is inline and reactive – it autocompletes inside your editor. ChatGPT is conversational – better when you need to explain a weird stack trace or walk through logic. Most working devs use both.

Can ChatGPT debug code it didn’t write?

Yes, but with a sharp drop in accuracy once the codebase grows. Imagine handing a stranger 4,000 lines of unfamiliar Python and asking “what’s wrong here” – they’d squint at it for an hour and guess. ChatGPT does the same thing, except it answers in 3 seconds and sounds confident. The fix is to isolate: find the function that’s misbehaving, paste only that, give it the failing input and expected output. Quality jumps immediately.

Does ChatGPT remember bugs I’ve already fixed in this conversation?

Within a single chat session, mostly yes – but “mostly” is doing heavy lifting. Long debugging sessions drift. The model starts referencing variable names from three messages ago that you’ve since renamed, or applies a fix you already rejected. When that happens, start a fresh chat and paste the current state of the code. It feels wasteful. It saves time.

Next step: grab the last bug you fixed manually this week. Re-debug it with ChatGPT using the hypothesis-first pattern from section two. Compare how close it gets to your actual fix – and note any package names it suggests, then verify each one on PyPI or npm before you trust them.