fix

packages/svelte/src/compiler/phases/3-transform/client/visitors/template.js

@@ -1680,8 +1680,7 @@ export const template_visitors = {
 					process_children(trimmed, () => b.id('$$anchor'), false, { ...context, state });
 				} else {
 					/** @type {(is_text: boolean) => import('estree').Expression} */
-					const expression = (is_text) =>
-						is_text ? b.call('$.first_child', id, b.true) : b.call('$.first_child', id);
+					const expression = (is_text) => b.call('$.first_child', id, is_text && b.true);
 
 					process_children(trimmed, expression, false, { ...context, state });
 
@@ -2184,6 +2183,9 @@ export const template_visitors = {
 			{ ...context, state: child_state }
 		);
 
+		// TODO only do this when necessary, and use a function with `if (hydrating)` so that it noops for non-hydraters
+		child_state.init.push(b.stmt(b.call('$.set_hydrate_node', context.state.node)));
+
 		if (has_declaration) {
 			context.state.init.push(
 				b.block([

packages/svelte/src/internal/client/dom/operations.js

@@ -70,6 +70,7 @@ export function child(node) {
 		return hydrate_node.appendChild(empty());
 	}
 
+	set_hydrate_node(child);
 	return child;
 }
 

packages/svelte/src/internal/client/index.js

@@ -62,6 +62,7 @@ export {
 	bind_focused
 } from './dom/elements/bindings/universal.js';
 export { bind_window_scroll, bind_window_size } from './dom/elements/bindings/window.js';
+export { set_hydrate_node } from './dom/hydration.js';
 export {
 	once,
 	preventDefault,