As part of getting to grips with the new world of agentic engineering, I built an application to support my work. It’s a sophisticated app: high-quality web UI with dynamic refresh and look-up, modals and auto-save, integrations to external systems, machine learning and text analysis, background jobs, and a proper environment setup with fully automated deployment. It’s approximately 150,000 lines of code, primarily in Rust (~120 kLoC) with the remainder in TypeScript and Terraform. This was entirely written by agents. Mostly Claude Code, and some use of Cursor. I didn’t read or review any of the code, except occasionally, out of interest. While building the application, I could see some things going awry. After watching an edit to line 4,000 of a file scroll by in the terminal, I had a closer look. The data access layer had grown to over 6,000 lines. As more features landed, this continued to grow. Every query, read or write, repeated the same HTTP request setup, the same JSON encoding and decoding.…