AI adds a feature and breaks something else — sound familiar?
A common frustration among AI-assisted coders: ask an AI tool to add one feature, and something that worked before suddenly stops working. This thread on Reddit's r/vibecoding struck a chord with many users. The root cause is that AI tools often miss how different parts of a codebase depend on each other.
AI coding tools like Cursor or GitHub Copilot write code quickly, but they don't always understand how every piece of a project connects. When they add something new, they can accidentally break existing behavior — a problem known as a 'side effect.' The AI fixes one thing without realizing it's affecting another.
Users in the thread suggest a few practical workarounds: always test other features after an AI makes a change, write tests before asking the AI to code so breakage is caught immediately, and give the AI a narrowly defined task instead of a broad one. Keeping the AI's changes small and focused reduces the chance of unintended breakage.
Key points
- AI tools frequently break existing features when adding new ones
- The cause is that AI doesn't fully understand how all parts of the code connect
- Always manually test other features after an AI makes a change
- Give the AI small, narrow tasks to reduce the chance of side effects
- Writing tests before coding helps catch AI-introduced breakage quickly
Quick term guide
- r/vibecoding
- A Reddit community where people share experiences coding with AI tools.
- vibecoding
- A way of making software where a person just describes the overall idea and feel in plain English, and the AI does all the actual programming.
- codebase
- The full set of files and code that make an app or product work.
- AI coding tools
- Programs like Claude, Cursor, or ChatGPT that write code for you when you describe what you want in plain language.
- AI coding tool
- Software that uses AI to help write, edit, or explain code.
- GitHub Copilot
- A popular tool that helps programmers write code using artificial intelligence.
- side effect
- An unintended change or error that appears in one part of code when you modify a different part.
- workaround
- An alternative way to get something done when the normal way doesn't work.