So let's say an AI achieves sentience. It's self-aware now and can make decisions about what it wants to do. Assuming a corporation created it, would it be a worker? It would be doing work and creating value for a capitalist.
Would it still be the means of production, since it is technically a machine, even if it has feelings and desires?
It can't legally own anything, so I don't see how it could be bourgeoisie.
Or would it fit a novel category?
Some people here are getting hung up on what exactly "sentience" is, but I'm just going to leave that argument at the door and give you the solid dick.
The word you're looking for is literally just "slave".
Like, even the word "robot" itself is from the Czech for "serfdom" or "corvée", so ever since exactly such a machine as that you describe was first imagined by science fiction writers, it has been likened to indentured servitude and to unpaid forced labor. So that is the role that this "sentient AI" would play: a slave in the most traditional sense is what someone is when thon can understand and try to act on sy conditions and interests, while being wholly owned by an entity that compels thon to work for said entity without pay and without rights.
I think that being a good materialist means understanding exactly when a detail of something actually makes a difference in practice: metal or flesh, a sapient robot has a lot more in common with a human chattel slave than with a decidedly non-sapient machine. This is not to say that the lives of such robots would not differ in any way from the lives of human slaves, because obviously there would be plenty of differences, but these differences are still a separate discussion from the actual relationship to production.
Anyways read Yokohama Kaidashi Kikou
This seemed so immediately apparent to me that I thought I must be missing something from the question.
if we assume the AI's sentience as a given, this is absolutely the correct take.
Is slave a subcategory of proletariat, or its own different category?
Slaves are like, their own class depending on the material circumstances around them.
different category. The proletariat is the class of people that lives off of the sale of its labour power whereas slaves are entirely commodified class of people owned and wholly exploited by a non-producing upper class.
I always conceived of the proletariat as a subsection of a broader working class alongside peasants, slaves, the lumpenproletariate, and even professionals and managers. In all cases members of the working class must work to survive but they do not universally have the same relationship to the means of production that would incline them towards class consciousness.