That's a technique called splicing, specifically it refers to "splicing" two videos in the middle, in this case one with real input and one faked. It is surprisingly possible (and often easy) to detect splices based on minute details.

Splicing isn't always cheating, it can be used for other reasons.

I can't prove that he isn't, strictly speaking, but Kosmic is a highly respected runner and has the skills to make this record.

If it needs to be verified, a camera on his hands would be enough for experts to be able to see that. Also if the inputs are visualised on screen.

What if he uses prerecorded footage of his hands, created by using some kind of TAS programmed to perform a 4:55 run in human style and then outputs those button presses to a screen. So instead of playing the game, he just presses what he sees on the screen. It would take a lot of work but would arguably be a lot easier than actually accomplishing the real run. Then, the footage is just TAS footage and the camera on his hands is also prerecorded. Then he just has to read out the comments on stream as this charade is going on and make sly responses to it

I guess my point is that, although I trust the veracity of this record, one should not underestimate the potential for cheating.

> So instead of playing the game, he just presses what he sees on the screen. It would take a lot of work but would arguably be a lot easier than actually accomplishing the real run.

First, matching prerecorded input with the frame-precision required would be nearly as difficult as doing the run, if not more so. At this point, he's already trying to produce very specific inputs that require frame-precision; he's not reacting to what's on the screen and adapting on the fly.

Second, some TAS techniques are incredibly difficult for a human to replicate, and there'd be an expectation that he can replicate those tricks at least sometimes.

Third, some of the techniques for detecting this kind of cheating include carefully watching the inputs to see if they're ever just the slightest bit late or early.

Mostly a lack of evidence

Lack of evidence can't really ever prove anything.

I think part of is the nature of it. Why would you get sufficiently into this scene, care enough about this one game to post video after video of you speedrunning it, to then cheat? The challenge for someone doing it manually is to do it manually; the challenge for someone doing it TAS is to do it TAS. Without the challenge there is literally no reason to do it. So while lack of evidence can't really prove anything, there really isn't that much motivation to cheat. If it was a complete nobody claiming they had manually set a record, yeah, that's suspicious, but someone well involved in the scene either is playing the long con for something that they themselves don't care about (and which they can't really revel in since any sort of in person interaction would show they're frauds), which is unlikely, or they're legit.

>Without the challenge there is literally no reason to do it.

What about money? Fame? Aren't these reasons?

And there are countless examples from history of 'the best' in whatever area getting caught at cheating just to stay 'the best'. I'm not really sure what you're getting at with this.

Actually plenty of people who have been deep in the community have cheated. It happens. But given that this run was performed live during a stream where he is reacting to chat it is pretty unlikely that he was doing playbacks of the entire stream.