A hooded man with a knife walks toward a woman sitting in her backyard. Before he reaches her, a humanoid robot steps between them and squares up. That’s the money shot in the one-minute video Unitree released on October 21 to introduce the H2-X, aka “Kung Fu Legend Guardian.”

It’s a machine that, in the company’s words, offers “powerful performance to serve and guard you.” It’s a robot that a lot of people will want at home: the T-800 to their John Connor. If the robot actually exists as the Chinese robot maker imagines it, this will be a mess.

A combat-trained, metal-smashing, bone-breaking robot drags one of the nastiest unsolved problems of battlefield AI straight into the living room. Can autonomous robots really tell friend from foe? Short answer: No. Not yet. And perhaps it will never happen, the same way humans can’t always tell.

The video, which Unitree swears was shot for real and not sped up, opens in a junkyard at night.…