I think your confusion is based on the same mistake you make here about what a "time horizon" is: https://news.ycombinator.com/item?id=48018160

If you do sprint planning, you can figure out which tasks have a short enough time horizon that the AI are competent enough to actually do the task correctly, and break down the tasks which they can't do reliably. If this sentence is confusing, see my answer to you in the other thread.

Sprints also gives you insight into when development velocity (per token rather than per time, though for both humans and AI this works out as money) slows down from technical debt.

Or at least it can in principle; I think the speed of AI is likely to make management less of an art and more of a science, with things like "technical debt" and "task estimation" going from gut feeling to something quantifiable, and this may in turn end up replacing Agile (and all the others) with something new.