fix

packages/svelte/src/internal/client/dom/blocks/svelte-head.js

@@ -2,7 +2,6 @@
 import { hydrate_node, hydrating, set_hydrate_node } from '../hydration.js';
 import { empty } from '../operations.js';
 import { block } from '../../reactivity/effects.js';
-import { HYDRATION_START } from '../../../../constants.js';
 import { HEAD_EFFECT } from '../../constants.js';
 
 /**
@@ -35,14 +34,11 @@ export function head(render_fn) {
 			head_anchor = /** @type {TemplateNode} */ (document.head.firstChild);
 		}
 
-		while (
-			head_anchor.nodeType !== 8 ||
-			/** @type {Comment} */ (head_anchor).data !== HYDRATION_START
-		) {
+		while (head_anchor.nodeType !== 8 || /** @type {Comment} */ (head_anchor).data !== '#head') {
 			head_anchor = /** @type {TemplateNode} */ (head_anchor.nextSibling);
 		}
 
-		head_anchor = /** @type {TemplateNode} */ (head_anchor.nextSibling);
+		head_anchor = set_hydrate_node(/** @type {TemplateNode} */ (head_anchor.nextSibling));
 	} else {
 		anchor = document.head.appendChild(empty());
 	}

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

@@ -137,9 +137,9 @@ export function render(component, options = {}) {
  */
 export function head(payload, fn) {
 	const head_payload = payload.head;
-	payload.head.out += BLOCK_OPEN;
+	payload.head.out += '<!--#head-->';
 	fn(head_payload);
-	payload.head.out += BLOCK_CLOSE;
+	payload.head.out += '<!--/head-->';
 }
 
 /**