TL;DR — Every AI system decomposes into two things that matter: the model and the harness (the code wrapping it). Claude Code, GitHub Copilot, ChatGPT — those are harnesses, not models. Right now only frontier labs build both halves. That won't last. As harness engineering becomes its own discipline — domain-specialized, model-agnostic — it absorbs most of what we currently call software engineering. The app store becomes the agent store, and our job shifts from writing code for humans to writing harnesses that automate human workflows.
I keep coming back to one formula whenever someone asks where AI engineering is actually headed:
Agent = Model × Harness
It sounds almost too simple. But it draws a line that clears up a surprising amount of confusion — about what an agent is, about who builds them, and about what our jobs become.
The distinction: model vs harness
