A machine that behaves like prey
Strip away the branding and look at the robot vacuum as your dog sees it: a low, round creature that emerges from its corner without warning, travels in darting lines, pauses, spins, bumps into chair legs, backs up and tries again. It makes a rising and falling whirring noise, it is roughly the size of a small animal, and it operates at exactly his head height. Prey drive is triggered by movement patterns far more than by what a thing is, and this machine's pattern — scuttle, stop, dart — is close to a small animal's. Herding breeds add their own reading: an object moving erratically around the room is a job to be controlled, circled and nipped into line, which is why collies, cattle dogs and terriers are the usual vacuum hunters.
Why it never learns to leave
A real intruder would flee, fight or be caught, and any of those endings would close the episode. The robot offers none. It does not run away properly, it does not get caught in any satisfying sense, and if your dog's charge makes a person switch it off or pick him up and remove him while laughing, the encounter ends in excitement either way. Tomorrow it comes out again. That endless rematch keeps the behaviour rehearsed and fresh. There is also a territorial layer for some dogs: the machine crosses the whole house, enters his room, noses under his bed's furniture and retreats to its dock on his floor, and a dog already inclined to patrol will treat its rounds as an invasion to be answered daily.
Safety first: nipping a machine is not harmless fun
It is tempting to film it, but build the habit out rather than enjoying it. Teeth on a moving appliance can crack on hard casing, catch in brushes, or meet the spinning parts underneath if he flips it. A dog who practises lunging at one moving household object generalises the habit more easily to others — wheeled toys, children's ride-ons, mobility aids, an actual small pet moving quickly across the floor. And a robot vacuum full of dust and hair, mouthed daily, is not something you want him ingesting from. Treat the chasing as a training task with a deadline, not a personality quirk.
Teaching a settle for cleaning time
Give him a job that pays better than hunting. Practise a mat settle while the robot is parked and silent, then with it cleaning in another room behind a closed door, rewarding calm listening. Next, let it clean the far side of a room while he is on his mat with a long-lasting chew, with a person beside him rewarding settled behaviour and a lead on if he is likely to launch. Keep sessions short and end them before he boils over. On non-training cleans, simply manage it: he goes out for his walk, or settles in a room the robot is not cleaning, so the majority of the machine's outings happen without an audience rehearsing the hunt.
A rota so the robot never meets an unsupervised dog
Because the vacuum runs on its own schedule in many homes, align the two rotas: the household's and the machine's. Set cleaning times for when he is reliably out or settled, and make sure everyone who lives there knows the rule — no launching the robot as a joke while the dog is loose, no filming ambushes for social media. Log which rooms and distances he can now ignore, so the training plan advances instead of restarting. KinsLe's Care Teams lets you assign who supervises each practice clean and record his progress, keeping the robot vacuum truce a shared household project.