Index: binaries/data/mods/public/gui/session/input.js
===================================================================
--- binaries/data/mods/public/gui/session/input.js
+++ binaries/data/mods/public/gui/session/input.js
@@ -1258,11 +1258,29 @@
 
 	var selection = g_Selection.toList();
 
+	const orderone = Engine.HotkeyIsPressed("session.orderone");
 	var queued = Engine.HotkeyIsPressed("session.queue");
-	if (g_UnitActions[action.type] && g_UnitActions[action.type].execute)
-		return g_UnitActions[action.type].execute(target, action, selection, queued);
-	error("Invalid action.type " + action.type);
-	return false;
+	if (!(g_UnitActions[action.type] && g_UnitActions[action.type].execute))
+	{
+		error("Invalid action.type " + action.type);
+		return false;
+	}
+	// Partly duplicated from doAction()
+	if (orderone)
+	{
+		// pick the first unit that can do this order.
+		const unit = selection
+			.find(entity => ["preSelectedActionCheck", "hotkeyActionCheck", "actionCheck"]
+				.some(method => 
+					g_UnitActions[action.type][method] &&
+					g_UnitActions[action.type][method](action.target || undefined, [entity]))
+		);
+		if (unit) {
+			selection = [unit];
+			g_Selection.removeList(selection);
+		}
+	}
+	return g_UnitActions[action.type].execute(target, action, selection, queued);
 }
 
 function getEntityLimitAndCount(playerState, entType)