AI Wrote 70% of My Production Codebase. Here's Why That Actually Worked.

I used Claude Code to build Sitewatch — a monitoring platform that catches when websites return 200 OK but are actually broken. Not a side project. A real SaaS, in production, with paying users. AI wrote roughly 60-70% of the codebase. Here are the things I wish someone had told me before I started. 1. Planning matters more than prompting This is the single biggest lesson and the one I almost learned too late. Early on, I'd open Claude Code and start prompting. "Build the check scheduling system." "Add retry logic." "Create the alerting pipeline." And it would. Working code, every time. The problem showed up three weeks in — I had a codebase full of features that each worked individually but didn't fit together. Different error handling patterns. Inconsistent data models. State flowing in three different directions. I had to stop and rewrite the architecture. That cost me more time than if I'd planned it from the start. Now my workflow is: plan first, prompt second. I think through dat