From b9e03714ebe1dbad9b31351f4e2d5487c90c670a Mon Sep 17 00:00:00 2001
From: Paolo Ricciuti <ricciutipaolo@gmail.com>
Date: Thu, 2 Jul 2026 08:30:23 +0200
Subject: [PATCH] fix: correctly transform declaration tags during SSR (#18492)

Closes #18490
---
 .changeset/rich-jokes-attack.md                             | 5 +++++
 .../phases/3-transform/server/visitors/shared/utils.js      | 6 ++++--
 .../samples/declaration-tags-transform/_expected.html       | 1 +
 .../samples/declaration-tags-transform/main.svelte          | 4 ++++
 4 files changed, 14 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/rich-jokes-attack.md
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/declaration-tags-transform/_expected.html
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/declaration-tags-transform/main.svelte

diff --git a/.changeset/rich-jokes-attack.md b/.changeset/rich-jokes-attack.md
new file mode 100644
index 0000000000..46e7d2d8c8
--- /dev/null
+++ b/.changeset/rich-jokes-attack.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: correctly transform declaration tags during SSR
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/utils.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/utils.js
index 3da6fcf321..56157cee37 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/utils.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/utils.js
@@ -60,7 +60,9 @@ export function process_children(nodes, { visit, state }) {
 				if (evaluated.is_known) {
 					quasi.value.cooked += escape_html((evaluated.value ?? '') + '');
 				} else {
-					expressions.push(b.call('$.escape', /** @type {Expression} */ (visit(node.expression))));
+					expressions.push(
+						b.call('$.escape', /** @type {Expression} */ (visit(node.expression, state)))
+					);
 
 					quasi = b.quasi('', i + 1 === sequence.length);
 					quasis.push(quasi);
@@ -80,7 +82,7 @@ export function process_children(nodes, { visit, state }) {
 		if (node.type === 'ExpressionTag' && node.metadata.expression.is_async()) {
 			flush();
 
-			const expression = /** @type {Expression} */ (visit(node.expression));
+			const expression = /** @type {Expression} */ (visit(node.expression, state));
 
 			let call = b.call(
 				'$$renderer.push',
diff --git a/packages/svelte/tests/server-side-rendering/samples/declaration-tags-transform/_expected.html b/packages/svelte/tests/server-side-rendering/samples/declaration-tags-transform/_expected.html
new file mode 100644
index 0000000000..5665318328
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/declaration-tags-transform/_expected.html
@@ -0,0 +1 @@
+<!--[--><div>number</div><!--]-->
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/declaration-tags-transform/main.svelte b/packages/svelte/tests/server-side-rendering/samples/declaration-tags-transform/main.svelte
new file mode 100644
index 0000000000..d969f907a5
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/declaration-tags-transform/main.svelte
@@ -0,0 +1,4 @@
+<div>
+	{let dt = $derived(Date.parse("2026-10-01T00:00:00Z"))}
+	{typeof dt}
+</div>
\ No newline at end of file