I know of many experienced and capable engineers working on complex stuff who are driving basically all their development through agents. This includes production level work. This is the norm now in the SV startup world at least.

You don't just YOLO it. You do extensive planning when features are complex, and you review output carefully.

The thing is, if the agent isn't getting it to the point where you feel like you might need to drop down and edit manually, agents are now good enough to do those same "manual edits" with nearly 100% reliability if you are specific enough about what you want to do. Instead of "build me x, y, z", you can tell it to rename variables, restructure functions, write specific tests, move files around, and so on.

So the question isn't so much whether to use an agent or edit code manually—it's what level of detail you work at with the agent. There are still times where it's easier to do things manually, but you never really need to.