There was a short story I read as a kid (between 2007 and 2009) about a world where people were raised from a young age with a microchip implanted in their skull which was trained over time to simulate the brain.
At some age, they would have their flesh brain tossed out in favor of the chip. But a month before the surgery, the chip would be set out of sync mode (so that it wasn't being corrected anymore based on how the flesh brain behaved).
Well, in this short story, the chip is set out of sync mode and this teenage kid then starts to realize that he can't control his actions. It starts with him disagreeing with his own choice of what fruit to buy at the supermarket.
So basically, the kid we listen to across the story is the consciousness that resides on the chip. He realizes this.
Then the surgery happens and the flesh brain is removed, and the chip is put in control.
Anyway, I don't remember the ending, but I remember I loved the story and it scared the hell out of me as a kid.
Existential, psychological terror is probably the best way to describe it.
Do you know what book has this story in it? Do you know what story this is?
Internet searches come up with nothing. I'm searching my house because I swear I don't remember tossing out this book.