If AI writes the code and AI reviews the code, what is the human actually responsible for?

A question that came out of a previous discussion. I asked whether code review was becoming the first AI bottleneck.

What surprised me was how many people responded with some variation of:

1. AI writes the code
2. AI reviews the code
3. Human approves the PR

Some teams seem to be moving in that direction already. That made me wonder: What is the human's role in this workflow?

Not in theory, but in practice. If AI generates implementation and AI performs the first review pass, where does human responsibility actually begin?

Architecture? Business requirements? Testing? Production incidents? Final accountability?

I'm not asking whether AI is good or bad. I'm trying to understand where experienced engineers believe the human still adds unique value once code generation and review are heavily automated.

Curious to hear from teams already operating this way.