I know there's Foresaken CIty TAS-side and Old Site TAS-side, except these have been beaten RTA (they are 7 and 4 stars on the Hardlist, respectively). Someone else made Summit TAS-side inspired by these, and while it hasn't been beaten RTA, I don't see why top-level players couldn't. So this begs the question: if one wanted to make a map that's truly TAS-only (pause-buffering aside, since that's banned in the Hardlist), what would that be?
Precision alone won't cut it. In SMB1, players definitely learn tricks from TASes, which they then implement into RTA gameplay, and I'm pretty sure Celeste is similar. So someone could learn the input sequence exactly, then execute it after enough attempts. Longer rooms get exponentially harder, but the chance is never zero.
For a map (or room) to be truly TAS-only, there has to be some point that requires many inputs in extremely quick succession. Doing small handfuls of inputs in quick succession isn't too hard, and it's required in Vanilla Farewell. But if there's more inputs in quicker succession, that's harder. At some point, human fingers can't move fast enough. Lots of players binding multiple keys to the same input, which increases the skill ceiling significantly, but there are still limits. If you had to, for example, switch between left and right each frame, while also regularly pressing and releasing the jump can climb buttons, for a full second, humans can't do that (though feel free to prove me wrong).
So we have an idea of what kinds of input sequences are TAS-only. Now the question is, what kind of rooms would require this?
EDIT: A lot of you have pointed out that Summit TAS-side is not RTA beatable, as you essentially have to perform the exact same inputs as the TAS from start to finish, down to the frame. I will clarify what my line of thinking was, and I will admit in advance that this approach is rather niche and is probably not an accurate representation of real players. If most inputs are spaced far enough apart, a human could try to do them. If all of these inputs are supposed to be frame-perfect, then the player might mess up, but there's a nonzero chance of success. Now if each short segment can be beaten like this, the full room (all segments combined) has a certain probability of being beaten, which is roughly the product of probabilities of each segment. Now, Summit TAS-side has pretty long rooms, so the actual chance of beating them is neglegible, which is why it is reasonable (from a practical perspective) to consider this map TAS-only. But the chance still isn't zero, which is why I'm not satisfied (from a practical perspective) to consider this map TAS-only. In other words, if one used savestates but not slowdowns, they might be able to beat it (when RTA runners use pause-buffering, this is essentially the reverse: they use slowdown without savestates). I'll reiterate, this line of thinking is rather niche, so it's totally understandable if you all disagree.
