I'm 49. I learned to code two years ago. Before that, I spent 30 years as a carpenter in Japan. This is the story of why I built HORIZON SHIELD — and the architectural decision that made it actually useful. The problem nobody was solving Japan's residential renovation market is ¥7.35 trillion per year. Contractors routinely overcharge by 15–20%. The weapon they use is a single Japanese character: 一式 (isshiki) — "lump sum." One line item. No breakdown. Inside that line item, markups of 200–300% are invisible. After 30 years on job sites, I watched this happen to thousands of families. They had no way to verify whether a quote was fair. Then ChatGPT arrived — and homeowners started asking it for second opinions. They got different numbers every time. A contractor will weaponize any inconsistency. "The AI said ¥800,000 last week and ¥1,200,000 this week — which is it?" Game over. The architectural insight The problem with using an LLM for cost estimation isn't intelligence. It's determinism.…