I run a mechanical contracting company, and I just built a full ERP system from scratch. I bought the company four years ago, when it still ran on pen, paper and a printer. Right after the purchase, I implemented QBO, Pipedrive and Airtable, with some Zapier automations tying them together. That went great. It made us more efficient and helped us scale the business. Then, a month ago, one of my customers showed me what he'd built with Claude Code, and it blew my mind. That weekend, I started building our own app. It began as a chatbot our technicians use to ask code questions and get answers that reference the code. Then came: -Tools to size gas piping and combustion air openings, so techs don't have to dig through tables -A dashboard that shows managers the cost and hours on their projects (something I'd struggled for years to get out of QBO) -An internal CRM that lets us add multiple customers to each bid (we'd been using a workaround in Pipedrive) -A tool that automates batch importing of bills into QBO -A QR code system to track our tools and equipment -Better dispatching -Better timesheets ...plus many other features I couldn't have imagined at the start. We're one month in, building this part-time while still running the day-to-day. Everyone in the company uses the new app daily. Everyone gave feedback and helped shape it for their own department. They all see the benefits, and no one feels like it was pushed on them. What we've ended up with is a truly custom ERP, the kind that until now only large enterprises could achieve. It fits our operations perfectly, so instead of changing how we work to fit whatever tools were available, the tools now fit how we work. I'm sharing this in the hope it helps others. I'm also curious: has anyone else used custom software to improve their operations? I'd love to hear about your experience.