I Went Looking for the Diff Debt in My Own Repo

Two posts ago I said I'd shipped code I never read. It's easy to write that as a general observation about the industry. It's less comfortable to go open your own repo and count. So I did. Here's what I found, and what I've actually done about it. The repo It's a desktop app I built for my own company. Roughly fourteen thousand lines of Python, a Tkinter UI, invoicing and documents and reports, the kind of internal tool nobody else will ever see. I had never written Python before I started it. I built it anyway, with a lot of AI help, learning as I went. That combination - no prior experience, heavy AI assistance, a real deadline because the business actually needed the thing - is basically a diff debt factory. I wasn't cutting corners on purpose. I just didn't have the knowledge to evaluate half of what I was merging, and it worked, so I moved on. What I actually found The clearest example took me months to notice. Five different parts of the app generate PDFs. Quotes, proformas, reports, petitions, heat treatment certificates. Every one of them was failing, in different ways, at different times, and I kept fixing them individually. Different error, different module, different patch. The actual cause was one thing: LibreOffice wasn't installed on the machine. Every one of those modules quietly depended on it to do the document conversion. Not one of them said so anywhere. I'd merged that dependency five separate times without ever registering that I'd taken it on. That's diff debt in its purest form. The code wasn't messy. It wasn't badly written. It just made an assumption I'd never read, and I paid interest on it five times over before I understood the principal. There were smaller ones too. A path handling bug that only showed up because my Windows username has a Turkish character in it - the code assumed ASCII and nobody, including me, had thought about it. Two Python versions installed side by side, quietly fighting. A stray quotation mark in my system PATH th