The Backstory#
In the summer of 2025, I tackled the GR 20 in Corsica for the third time. One major risk on the trail during summer is sudden thunderstorms. While Météo-France’s AROME model offers incredibly precise forecast data, there’s a catch: large sections of the trail have absolutely no cell service. However, my Garmin inReach Messenger is capable of receiving satellite texts.
So, I devised a plan. I used Claude to build a CustomGPT for ChatGPT that acted as my “Tech Lead,” feeding technical requirements into Cursor AI. Cursor then did the heavy lifting, implementing the actual project for me in Python.
Long story short: It worked. It actually worked incredibly well. The weather updates I received every morning and evening were spot-on and saved me from walking straight into several severe thunderstorms.
But getting there was as rocky as the GR 20 itself. Several times, I thought I was right at the finish line—only to realize moments later that the AI had pretty much torched the entire codebase, and even frequent Git commits couldn’t always save me. It cost me about two months of my life. I’m guessing an experienced developer could have pulled it off in three weeks with AI, or maybe five weeks without it.
The biggest lesson I learned is that AI is about as smart and enthusiastic as a junior developer. But unlike a human junior, the AI doesn’t learn from its mistakes. You have to constantly optimize the processes yourself to keep the AI on the rails. I also learned the hard way that you need to structure your documentation in a highly modular way, ensuring the AI only loads the specific context it needs into its memory—and nothing more.
Those were just my first attempts. Six months have passed since then; I’ve learned a ton, and the software landscape has evolved significantly, too.
Links#
- Weather Email Autobot (original) on GitHub
- Gregor Zwanzig (rewrite) on GitHub