I have a personal project I've been playing with as an experiment. It's a personal health and medical records app. Originally started as a way to replace a spreadsheet I used to keep track of my labs and a few other things. I purposely did it hands off. I think I edited the code once just because I was being impatient. It's up to 1.2M lines of code and it works. Minor bugs now, mostly around dark mode, but Claude Code has no issues adding new features or refining existing ones. And I've been adding some crazy features just to see if it can do it. It has a DICOM viewer for imaging studies, pulls common medications from various public APIs to auto-fill. It exposes an API I use with the Health Auto Export to push Apple Health data from my phone. Pulls provider info from the NPI database API to auto-fill name, specialty, location, phone, etc. Text extraction from uploaded reports, extracts context from the reports to create new entries for procedures, diagnoses, etc. Has a firefox plugin to scrape my data from MyChart. Even tracks basic weather (temp, pressure, AQI) and has a correlation engine to allow me to click on a symptom (pulled from diary entries) and it shows correlating data (weather, vitals, med changes, etc) around it. So not a simple app. All containerized and (via instructions in claude.md) it manages the containers and updates documentation on every change. One key is to force it to write and pass tests. The test suite for the app is huge but it usually means code works the first time as the AI can run the tests and troubleshoot at the end of every update.
Now is it perfect? No. There are gaps you need to know about and work to fix. For exampe it it took me a while to tune the claude.md to get it to always use ZOD because it will happily create front end and back end components in the same run with mis-matched schemas. And I'm sure the code isn't the most efficient. Claude actually has a "Code Simplification" skill I need to incorporate into the workflow at some point. But it's been a fun experiment so far.