From b5faa246f068a8aeb76fc5beb6997ed9b7b84bcc Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Sun, 28 Sep 2025 15:14:40 -0700
Subject: [PATCH] fix: coerce nullish `<title>` to empty string

---
 .changeset/silly-walls-fail.md                      |  5 +++++
 .../3-transform/client/visitors/TitleElement.js     | 13 ++++++++++++-
 .../runtime-runes/samples/title-nullish/_config.js  |  7 +++++++
 .../runtime-runes/samples/title-nullish/main.svelte |  6 ++++++
 4 files changed, 30 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/silly-walls-fail.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/title-nullish/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/title-nullish/main.svelte

diff --git a/.changeset/silly-walls-fail.md b/.changeset/silly-walls-fail.md
new file mode 100644
index 0000000000..6f364e7f8a
--- /dev/null
+++ b/.changeset/silly-walls-fail.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: coerce nullish `<title>` to empty string
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/TitleElement.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/TitleElement.js
index e6f4202a01..98d7880b25 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/TitleElement.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/TitleElement.js
@@ -12,8 +12,19 @@ export function TitleElement(node, context) {
 		/** @type {any} */ (node.fragment.nodes),
 		context
 	);
+	const evaluated = context.state.scope.evaluate(value);
 
-	const statement = b.stmt(b.assignment('=', b.id('$.document.title'), value));
+	const statement = b.stmt(
+		b.assignment(
+			'=',
+			b.id('$.document.title'),
+			evaluated.is_known
+				? b.literal(evaluated.value)
+				: evaluated.is_defined
+					? value
+					: b.logical('??', value, b.literal(''))
+		)
+	);
 
 	if (has_state) {
 		context.state.update.push(statement);
diff --git a/packages/svelte/tests/runtime-runes/samples/title-nullish/_config.js b/packages/svelte/tests/runtime-runes/samples/title-nullish/_config.js
new file mode 100644
index 0000000000..819d6b620e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/title-nullish/_config.js
@@ -0,0 +1,7 @@
+import { test } from '../../test';
+
+export default test({
+	test({ assert, target }) {
+		assert.equal(target.ownerDocument.title, '');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/title-nullish/main.svelte b/packages/svelte/tests/runtime-runes/samples/title-nullish/main.svelte
new file mode 100644
index 0000000000..f1fa7e7b84
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/title-nullish/main.svelte
@@ -0,0 +1,6 @@
+<script>
+    const thing = {};
+</script>
+<svelte:head>
+    <title>{thing.thing}</title>
+</svelte:head>
\ No newline at end of file