For fifteen years the .env file has been the most convenient lie in web development: a plaintext file full of production-grade credentials, kept safe by the single assumption that only you would ever read your own disk. That assumption is now false, and the fix is less dramatic than it sounds.
A coding agent starts every session knowing nothing about your project, so the repository has to answer its questions. This post describes a small set of files that give those answers, and argues that you should design them like an API: a few clear entry points that make the right context cheap to find.
In February 2026 Mitchell Hashimoto gave a name to a habit, and within six months OpenAI, Anthropic, Thoughtworks and Red Hat had all published on it. The practices underneath the name are decades older than the name — which is the most interesting thing about it.
Picking a Claude model is really two decisions — which model and how much effort — and the more interesting question is who should make them: a config file, a skill, a cheap router model, or the most capable model delegating downward.
Every agent is, at heart, a loop: a model calling tools until the job is done. The interesting engineering question of 2026 is what happens when you wire many of those loops together into a graph — and when you shouldn't.