What I learned building an opinionated and minimal coding agent
2025-11-30
It's not much, but it's mine
Table of contents
In the past three years, I've been using LLMs for assisted coding. If you read this, you probably went through the same evolution: from copying and pasting code into ChatGPT, to Copilot auto-completions (which never worked for me), to Cursor, and finally the new breed of coding agent harnesses like Claude Code, Codex, Amp, Droid, and opencode that became our daily drivers in 2025.
I preferred Claude Code for most of my work. It was the first thing I tried back in April after using Cursor for a year and a half. Back then, it was much more basic. That fit my workflow perfectly, because I'm a simple boy who likes simple, predictable tools. Over the past few months, Claude Code has turned into a spaceship with 80% of functionality I have no use for. The system prompt and tools also change on every release, which breaks my workflows and changes model behavior. I hate that. Also, it flickers.
I've also built a bunch of agents over the years, of various complexity. For example, Sitegeist, my little browser-use agent, is essentially a coding agent that lives inside the browser. In all that work, I learned that context engineering is paramount. Exactly controlling what goes into the model's context yields better outputs, especially when it's writing code. Existing harnesses make this extremely hard or impossible by injecting stuff behind your back that isn't even surfaced in the UI.
Speaking of surfacing things, I want to inspect every aspect of my interactions with the model. Basically no harness allows that. I also want a cleanly documented session format I can post-process automatically, and a simple way to build alternative UIs on top of the agent core. While some of this is possible with existing harnesses, the APIs smell like organic evolution. These solutions accumulated baggage along the way, which shows in the developer experience. I'm not blaming anyone for this. If tons of people use your shit and you need some sort of backwards compatibility, that's the price you pay.
I've also dabbled in self-hosting, both locally and on DataCrunch. While some harnesses like opencode support self-hosted models, it usually doesn't work well. Mostly because they rely on libraries like the Vercel AI SDK, which doesn't play nice with self-hosted models for some reason, specifically when it comes to tool calling.
So what's an old guy yelling at Claudes going to do? He's going to write his own coding agent harness and give it a name that's entirely un-Google-able, so there will never be any users. Which means there will also never be any issues on the GitHub issue tracker. How hard can it be?
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