What 49 Vibe-Coded GitHub Projects Revealed About AI Code Duplication

I ran jscpd against 49 vibe-coded GitHub projects looking for code duplication patterns. Average duplication: 7.98% (above the 3-5% industry benchmark). But the unexpected finding wasn’t in the apps — it was in the skill libraries built to teach AI agents how to code. Those have 30-40% duplication rates, mostly in markdown instructions and CSS templates duplicated for different agent platforms. The infrastructure designed to enforce AI discipline embodies the same pattern it’s trying to prevent.