Sometime in the early or mid 1980s, maybe even late 1970s, I came across a SciFi story on a PBS channel about a lone fighter dress in pseudo-samurai clothing with a sword. The guy was in battle with another individual, both were intent on killing each other.
The guy had an AI companion in the form of a sphere on top of a walking stick. In one scene taking place at night, the AI described itself as being very large once and helped a lot of people before the world fell.
In one of the final scenes, the guy comes across a kneeling figure in a cloak which turned out to be a gun turret that destroys the AI companion. The nemesis appears at a distance and the guy proceeds to tell him while he has had the guidance of the AI most of his life, he'll learn to do without. The show ends with the guy walking off into the distance.
Any clues what this might have been?