[Side B] Breaking Free from Vibe Coding Fatigue: A Practical Record of Building an OSS with 'Spec-First AI Development'

From the Author: D-MemFS was featured in Python Weekly Issue #737 (March 19, 2026) under Interesting Projects, Tools and Libraries . Being picked up by one of the most widely-read Python newsletters confirmed that in-memory I/O bottlenecks and memory management are truly universal challenges for developers everywhere. This series is my response to that interest. 🧭 About this Series: The Two Sides of Development To provide a complete picture of this project, I’ve split each update into two perspectives: Side A (Practical / from Qiita): Implementation details, benchmarks, and technical solutions. Side B (Philosophy / from Zenn): The development war stories, AI-collaboration, and design decisions. Are You Realizing the Limits of "Vibe Coding"? Having AI write code for us has become the norm. Throw a prompt at it, and it returns plausible code. It runs. The tests pass. It's convenient. However, if you continue this way of "having AI generate code based on a vague vibe"—often called Vibe Co