Something small that has been on my mind for the past decade or so -- assistant chatbot.
Basically I long wanted to plug a chatbot into my messenger of choice with all sorts of tools for quick use, of course after the emergence of LLMs it was only a matter of time before I find time for it.
As an experiment I have decided to use Claude code + opencode to develop it, and after some trial and error I am very thoroughly impressed with the results, it grew to a nearly 10k LOC in a week and it is still very much manageable, I haven't changed a single line of code manually still.
I have developed it as a "core" that imports modules with a rigid and thoroughly documented in a spec.MD file interface, and every single bit of functionality essentially acts as a different sub-app that can consume events that trigger it and handle all of the internal logic within itself, that way everything is separated nicely and totally manageable within LLM context.
It does everything from setting up and sending reminders and todo lists, helping me track car mileage and fuel consumption, getting an overview of the day ahead(sometimes if task is important even a reminder few days prior to its date), to even opening my front gate. And all of that is exposed to 'core' chat module through tool calls, so I can request anything in plain English or voice.
Also has a web-ui where I can review tasks, reminders, settings or search past conversations.
Been using it a lot, and since I'm using groq for inference, I still haven't even needed to pay a thing, since it fits within the free limits