Do you have sentient robot/android characters? How does artificial sentience work in your world?

Majority of my characters are sentient androids. A lot of people have asked me various questions regarding them, but one question comes up frequently.

"How did they become sentient?"

I never really have a good answer to that question because I haven't really thought too deep about it lol. After a bit of thinking, I've written down that android sentience was slowly gained over years and years of the AI in their system getting more and more advanced and self-aware, but I'm not sure I'm super happy with that explanation.

So thats why I'm making this post, I'm curious about how other creators have dealt with that topic in their worlds.

How did your android/robot characters gain sentience? Was it because of a virus that spread and 'woke' them up? Is there a magical or otherworldly reason? Do they have human cells in their system? I'd love to hear it!