Lumen
An open-source desktop browser with an AI agent in the sidebar that can operate the browser, with an approval step before anything risky.
What I did
- Specified each feature and the rules for when the AI must ask before acting
- Wrote performance budgets (startup, bundle size, Settings open time) as tests that fail the build
- Ran parallel AI coding agents, one per feature branch, with CI on every change before it landed
- Shipped Windows and signed macOS builds with a self-updater
A side project where I learned to manage AI coding agents like a team. Every change brought its own tests, docs and changelog entry, and nothing landed until CI passed. I wrote very little of the code by hand. My part was deciding what to build, writing the specs and tests, reviewing changes and shipping releases.
What broke and what I changed
It got slower as features piled up. Startup and the Settings window slowed down with each new feature. I turned the speed targets into tests that fail the build: a ceiling on modules loaded at startup (about 340), a size limit on the UI bundle, and 150 ms to open Settings. Heavy modules now load only when first used, and hidden widgets and background tabs are parked.
