Cursor, Claude Code and Codex all have a BIG problem

A developer and early investor in Cursor argues that AI coding tools like Cursor, Claude Code, and Codex are plagued by poor UX and instability because they were built using early, weaker AI models—a form of premature 'vibe coding' that created low-quality codebases with compounding technical debt. The core thesis is that codebase quality peaks around the 6-month mark and only degrades after that, and bad patterns spread exponentially faster than good ones, especially when AI agents copy existing code. Practical advice includes: tolerate zero bad patterns, aggressively delete and rewrite bad code (now cheap with AI), keep unrelated features in separate repos, spend more time in planning mode with models, and use the latest models. A proposed future pattern is maintaining two parallel codebases—a 'slopfest' prototype version for rapid experimentation and a clean production version—similar to how Vampire Survivors maintains both a Phaser.js prototype and a C++ production build.