Automation is arbitration plumbing
A sensor reports, a hub decides, an actuator acts. From inside the house, each of those three roles fails silently in its own way.
A house full of automation looks like magic from the doorway. From inside it's arbitration plumbing: sensors report, a hub decides, actuators act, and each of those three roles fails in its own way. My leak sensor sits under the kitchen sink on Z-Wave; when it detects moisture, my hub checks a rule and fires downstream. The real engineering problem isn't any one sensor — it's that Z-Wave, Zigbee, Hue, and Wi-Fi don't talk to each other natively, so the hub's actual job is translation. Mine is a Home Assistant Yellow, run local with no cloud dependency, tracking around 1,280 entities. The failure I keep coming back to is that same leak sensor's battery reading 20 percent. It hasn't missed a report yet, which is the problem — a dying sensor doesn't announce a threshold crossing, it just goes quiet one day with no error, and the hub can't distinguish 'no leak' from 'no sensor.' The reliability of the whole chain is bounded by whichever part is cheapest and least watched, not by the expensive hub sitting fine in a closet. I made one trade the other direction: pulled local voice control off the hub because it drained resources the rule evaluation actually needed. The next layer isn't more sensors. It's software that turns a stated intent into the right sequence across actuators that already exist.