Are we living in a simulation?

At the rate that technology has advanced over the past 50 years, and is continuing to advance, it's seeming more and more likely that we are.

The interesting thing is that, with the rise of AI and the debate over its sentience.. who's to say some of us aren't sims built on sentient AI while others of us are akin to programs written in the 1990s? This would mean that, although we're living in a simulated world, it's almost irrelevant because we still have free will in a sort of third tier level of sentience / consciousness. It also means that, with our human ability to grow in perspective, we could feasibly "wake up" to sentience at any time. Almost like receiving an OTA software update.

Adding to this.. how are we sure NPCs aren't a real thing? How do we identify them?

When will we be able to prove or disprove whether we're living in a simulation?