No belt, but they don’t puncture anything like a high pressure 23mm does. Very infrequent, or due to dumb stuff like super low pressure on rocky downhills while loaded.
I run both Hetres and Cerfs on two of my bikes, had one puncture on the Cerfs in over 3000ks. Mostly road rides with occasional dirt roads. I’m about to try Cols de la Madeleine which are 23 mm.
23mm on a 23mm rim. They’re quite narrow. I’d only use them if the frame is super tight, much much rather the 26mm Cerf if it fits. Or the Compass Cayuse Pass if you’re balleur.
I’m saying that the wide, low pressure, Compass tyres have a slightly different casing to the Grand Bois, and have been much more successfully setup TL. I would not run the medium/narrow 700C Compass tyres TL.