Bayd b'Khubz is the plainest entry in the Lebanese egg-sandwich family: eggs, fried or scrambled, put straight into Arabic bread. The name says exactly that, "eggs in bread," and there is almost nothing to hide behind. The angle is execution over ingredients. With only egg and khubz in play, the sandwich is entirely about how the egg is cooked and how fresh and pliable the bread is. Treated carelessly it is dry egg in a stale wrapper. Treated well it is one of the cleanest hot sandwiches there is.
The build is short. Eggs are cooked in oil or a little butter, either fried so the white sets and the yolk stays soft, or beaten and scrambled to a just-set curd, seasoned simply with salt and often pepper or a pinch of seven-spice. The egg is laid onto a sheet of thin khubz or tucked into a pita while still hot and rolled tight so the bread takes a little of the heat and softens against it. That is the whole construction. Good execution is about the egg's texture and the bread's freshness: a fried egg with a runny or barely set yolk that moistens the bread as you eat, or a scramble pulled off the heat while still glossy, wrapped in a soft fresh flatbread that folds without cracking. Sloppy execution overcooks the egg into something dry and bouncy, uses a cold or stale bread that fights the filling, or skips seasoning so the sandwich tastes of nothing and demands salt after the fact.
It shifts mostly by how the egg is cooked and by the small things added at the edges. A fried-egg version with a soft yolk is richer and messier. A scrambled version is tidier and easier to roll. Common additions stay minimal: a smear of olive oil, a slice of tomato, a few sprigs of mint or parsley, a dusting of sumac, sometimes a little cheese folded in while the egg sets. Push it further with sausage, preserved lamb, or fried potato and it stops being bayd b'khubz and becomes one of its named cousins, each of which deserves its own article rather than being folded in here. What this one reliably delivers is the baseline egg sandwich of the Lebanese kitchen: egg, bread, salt, eaten hot and in the hand.