Bannister and Cat Safety

I have absolutely no idea where to put this, so I'll try here.

I recently let my cats up into my converted attic.  The stairs come up the center and there's a bannister around it.  There's a sofa table along one side of it and desks and file cabinets on the other.  The top rails are as wide as two by fours, but they're slippery.  I don't worry about them walking around the top of the stair railing as chasing each other and going over the top and falling down into the stairwell.  In other words, they have the perfect launching pad  for running up the couch, onto the sofa table and attempting to leap to the other side (or slipping when they try to turn).

Is this a legitimate worry?

Honestly, not so much. I think it's about as dangerous as scraping your knee as a kid because you think jumping off a swing mid-air is hilarious (I may or may not have done that). They probably won't do it again.

That said, I would see if you can cover the stairs, railings, any part that has a sharp or pointed end or edge with something soft, even a just thick fabric, like maybe carpeting or rug that goes up the stairs.

I thought about that, wrapping some foam around the railing and buying a big piece of rectangular foam to stick in the stairwell.   I'm not so much worried about them losing their balance and falling, as them having the zoomies and chasing one another.  They start at one end of the living room and sail over the back of the couch (the back faces the middle of the room and not a wall) on their way to the other end of the house.  Except if they do that up here they're going to have an 8 foot drop down the open stairwell.