Reducing Claude Code Malfunctions with a Single Spec File

The most common mistake non-technical founders make when using Claude Code is treating it like a casual chat. While it’s exciting to experiment at first, there comes a point where the AI starts spitting out inconsistent or contradictory code. As a project grows, the AI tends to lose track of your original vision. To prevent this, you need to create a blueprint in plain language before you even touch the terminal.

Time Saved by the product_spec.md File

Even without development knowledge, you must define the skeleton of your service yourself. Create a file named product_spec.md at the very top of your project folder. In this file, describe in detail—and in your own language—the purpose of the service, the essential features, and how users will navigate through the screens.

Once prepared, run Claude Code in your terminal and enter Plan Mode. Then, simply instruct it: "Create an implementation plan based strictly on the contents of this document." According to observations by Anthropic, developing based on such pre-defined specifications can save over 5 hours of wasted time spent untangling messy code later.

How to Avoid a $75,000 Bill from API Key Leaks

Security isn't something to worry about later. According to 2024 statistics, sensitive information accidentally exposed on GitHub increases by more than 2% every year. AI agents are actually twice as likely to expose security information compared to human developers. In one real-world case, a leaked Google Cloud API key resulted in a charge of $82,000—over 100 million Korean won—in just two days. For a solo founder, this is a catastrophic event that could force a business to close.

Do these three things before writing any code:

• Create a file by typing touch .env in the terminal, and command Claude to write all passwords and API keys only in this file.
• Create a .gitignore file and write .env inside it. This prevents the file from ever leaving your computer.
• Set access permissions for the .env file to "deny" in the Claude configuration file (~/.claude/settings.json).

By doing this, you can fundamentally block automated hacking bots from stealing your precious credentials.

When the Screen Is Blank, Copy the Browser Console

It’s frustrating when the AI says the code is finished, but the browser screen remains a blank white page. However, you don't need to call an expensive outsourced developer in this situation. The browser is already giving you the answer.

Press F12 in your web browser to open the Console window. Copy all the red error messages you see there and simply paste them into the Claude Code terminal. Just add a quick note: "I'm getting this error; find the cause and fix it." Even if you don't understand the technology, if you convey the error messages accurately, the AI will act as your eyes and ears to catch the bugs.

The Rollback Habit That Saves 90% of Costs

Claude Code charges you based on the volume of tokens you use. While most users spend around $12 a day, you can get hit with a price bomb if you repeat the same questions or assign tasks that are too massive.

To save costs, you must break tasks into small chunks. Request one login feature or one menu bar design at a time. Every time a feature is successfully implemented, tell it: "Commit what we've done so far." Think of it as a save point in a game. If the AI messes up the code, don't panic; just type git reset --hard HEAD in the terminal. It will magically return to the last successful state. This one habit can reduce unnecessary re-fix costs by up to 90%.