I’m writing this on the Shinkansen heading to Osaka, halfway through a solo 10-day trip across Japan that I planned almost entirely with AI agents. This post isn’t about how AI can write a generic itinerary — anything can do that now. It’s about the small, weirdly clever ways agents earned their keep on this trip: rewriting the itinerary in place so my own trip viewer would render the day correctly, cross-referencing Reddit, YouTube transcripts, and official sources on its own to validate each leg, optimizing a 7-hour layover down to the minute, and replanning the afternoon when check-in finished early.

I’m now officially a Happy engineer! In this post, I’ll explain what Happy is, why I decided to self-host it, and how my setup works. I’ll also share practical details about my LLM provider strategy, workspace configuration, and the lessons I learned along the way. Happy is becoming more than just a tool—it’s evolving into my primary development environment. With MCP tool integration and remote development capabilities, I rarely need a traditional IDE setup anymore.