A kid, a kitchen knife, and a bundle of wires
At the age of school I knew how to sold wires by using kitchen knife. I tested resistors and capacitors. Wiring came next, done with a scissor, along with converting AC to DC voltage. I built a 2-way speaker system and assembled an amplifier by following a kit manual. I also made an aeroplane model by adding DC motors and lights, and used to mend my neighbor’s electronics appliances just because I was curious how they worked.
None of that stuff ran on one wire. A speaker needs power going one way and signal going another. An amplifier has input, output, gain control, and ground, all sitting inches apart from each other. All of it has to be right, or you get a hum, a short, or smoke. The thing that made any of it survive being a kid’s hands with a kitchen knife was the harness. It is the bundle that keeps every wire routed exactly where it needs to go. It protects the wiring from heat and from getting yanked loose. It also keeps it from touching the wrong wire and frying whatever you just spent a week building.
I never called it that back then. I just knew that a loose wire was a broken device. A well-routed one kept working no matter how many times I picked it up and moved it around. Years later I would learn the industry has a name for exactly this discipline: harness engineering.
What harness engineering actually means today
I am thinking about this now because “harness” showed up again this year, in a completely different context. It means almost the exact same thing. Harness engineering is the term the AI coding world is using for this discipline. It means designing the constraints, checks, and feedback loops that sit around an AI agent. It covers the rules the agent follows, the guardrails it can’t cross, and the loop that catches a mistake before it repeats.
Agent = Model + Harness. Same as Amplifier = Circuit + Harness. The model is powerful the same way raw current is powerful. Left loose, both of them go wherever they want. Usually that is somewhere you did not intend.
The old lesson wearing a new name
So is it possible the child soldering wires with a kitchen knife was already learning this lesson? The industry is only now giving it a name. I think so. Whether it is electricity or an AI agent’s output, the power itself was never the hard part. Routing it so it goes exactly where you meant it to, every single time, is the actual engineering.
It made me pause and rethink something. We keep inventing new names for a very old idea. Contain the power. Route it deliberately. Protect it from itself. That could be a bundle of copper wires behind a dashboard. It could be a set of linters, hooks, and review gates around an agent writing your code. Either way, the job has not changed. Only the wire has.
What’s next
Now and onward my focus is to discover more of these parallels. What does a well-harnessed AI agent setup actually look like next to a well-harnessed circuit? Where does the analogy start to break down? In future posts I will walk through building an actual harness around an agent I use daily. I’ll share what breaks first — practical harness engineering, not just the theory. But for that you need to stay with me for the next post.
Related reading: my earlier post on what “AI Native” actually means, and for the technical background on the term itself, Martin Fowler’s writeup on harness engineering.
Happy Building…