How the Cerebras across the reticle limits to produce the largest chip,WSE?
The "reticle limits" you allude to refer to the area over which the optics can maintain the highest resolution. This is one of the things that limits the size of a conventional chip.

Normally, when you step the reticle to the next chip position, you don't care so much about the exact alignment between the two adjacent chips, because you aren't trying to make connections between them. The stepper just needs to be accurate enough so that you don't waste a lot of area for the dicing channels.

But if you DO want to make connections between "chips" using overlapping images, there's nothing stopping you from coming up with a relaxed set of design rules for those connections that takes into account the accuracy of the stepper.

There are other ways to make such connections as well. In the worst case, you could always use your wire bonder to make them. And a FIB (focused ion beam) machine can be used to post-process a wafer to add or remove connections.