The Most Common Beginner Mistakes in Vibe Coding

The term vibe coding was coined by Andrej Karpathy on X in February 2025, and it is worth reading what he actually wrote: a mode where you "fully give in to the vibes, embrace exponentials, and forget that the code even exists… I 'Accept All' always, I don't read the diffs anymore." Crucially, he scoped it to "throwaway weekend projects." The most common beginner mistakes in vibe coding all stem from one error: taking that throwaway-project posture and pointing it at real, internet-facing, money-handling software.

Here are the mistakes that turn cheap, fast code into a liability — and how to avoid each one.

Mistake 1: Not reading the code

This is the original sin, and it is definitional. Developer and AI-tools commentator Simon Willison drew the line precisely in March 2025: "If an LLM wrote the code for you, and you then reviewed it, tested it thoroughly and made sure you could explain how it works to someone else — that's not vibe coding, it's software development." His personal rule: "I won't commit any code to my repository if I couldn't explain exactly what it does to somebody else."

The fix is that rule. For anything beyond a throwaway, read the diff and be able to explain it. The not-reading-the-code posture is fine for a weekend toy and dangerous for everything else.

Mistake 2: Exposing secrets and skipping auth

The most expensive beginner mistakes are security ones, and they cluster. A non-technical indie hacker built a SaaS with Cursor and "zero hand-written code," then posted on 17 March 2025 that he was "under attack… maxed out usage on api keys, people bypassing the subscription, creating random shit on db." The root causes were textbook: exposed API keys, a bypassable paywall with no real authentication, no rate limiting, no input validation.

This is not a one-off. Semafor reported in May 2025 that of 1,645 apps built on Lovable that were scanned, 170 allowed anyone to access user data — names, emails, financial information, even secret AI API keys — traced to improper backend configuration. Lovable's own response: "We're not yet where we want to be in terms of security." The lesson: keep keys in environment variables, never in code; use a managed auth provider rather than a hand-rolled one; and add rate limiting and input validation before anything public goes live.

Mistake 3: Trusting hallucinated dependencies

A distinctly AI-era mistake is installing a package the model invented. A study presented at USENIX Security 2025 analyzed 576,000 generated Python and JavaScript code samples across 16 models and found 19.7% of recommended packages did not exist — over 200,000 unique fabricated names. Open-source models hallucinated around 21.7% of the time versus about 5.2% for commercial ones.

The danger is that the fakes are predictable: of 500 hallucination-triggering prompts run ten times each, 43% of the invented names reappeared in every run. That reliability lets attackers pre-register the fake names with malware — an attack the Python Software Foundation's Seth Larson named "slopsquatting." The fix: verify every import exists on the real registry before installing, and pin your lockfile.

Mistake 4: No version control, no tests

Two habits the throwaway mindset skips and real projects cannot. Without version control, there is no way to see what the agent changed, no way to revert a bad generation, and no record of how the codebase evolved. Without tests, you have only the model's confidence that the code works — and confidence is not correctness. Initialize git before the first prompt, commit in small increments so each AI change is reviewable, and ask the agent to write tests for the path it just built.

The beginner-mistakes checklist

FAQ

Is vibe coding inherently bad? No. As Karpathy framed it, it is great for throwaway weekend projects. The mistake is using that same no-review posture for production, internet-facing, or money-handling software.

What is the single most important habit to fix? Reading the code. Simon Willison's distinction is the whole game: if you review, test, and can explain it, it is software development; if you skip that, it is risky vibe coding.

What is slopsquatting? An attack where someone registers a non-existent package name that LLMs reliably hallucinate, then ships malware in it. Because the same fake names recur across runs, they are easy to target — verify imports before installing.

Why do so many vibe-coded apps get hacked? Because beginners skip the unglamorous backend basics — secrets management, real authentication, rate limiting, input validation — that AI does not add by default, as the 2025 EnrichLead and Lovable incidents showed.

Bottom line

Every common vibe-coding mistake is the throwaway-project mindset misapplied to real software. Read the diff and be able to explain it; keep secrets in the environment and use managed auth; verify every dependency against the real registry before installing; and use version control and tests from the first prompt. Karpathy invented vibe coding for weekend toys — the beginners who got burned in 2025 were the ones who forgot that scope.

Sources and further reading