diff --git a/.changeset/strange-apricots-happen.md b/.changeset/strange-apricots-happen.md
new file mode 100644
index 0000000000..d61dfb5149
--- /dev/null
+++ b/.changeset/strange-apricots-happen.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: set `open` binding value in `<details>`
diff --git a/packages/svelte/src/compiler/phases/bindings.js b/packages/svelte/src/compiler/phases/bindings.js
index d8f04e1732..820c66d886 100644
--- a/packages/svelte/src/compiler/phases/bindings.js
+++ b/packages/svelte/src/compiler/phases/bindings.js
@@ -175,6 +175,7 @@ export const binding_properties = {
 	textContent: {},
 	open: {
 		event: 'toggle',
+		type: 'set',
 		valid_elements: ['details']
 	},
 	value: {
diff --git a/packages/svelte/tests/runtime-runes/samples/details-binding-initial/_config.js b/packages/svelte/tests/runtime-runes/samples/details-binding-initial/_config.js
new file mode 100644
index 0000000000..d0ecf31923
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/details-binding-initial/_config.js
@@ -0,0 +1,11 @@
+import { ok, test } from '../../test';
+
+export default test({
+	test({ assert, target }) {
+		const details_el = target.querySelector('details');
+
+		ok(details_el);
+
+		assert.strictEqual(details_el.open, true);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/details-binding-initial/main.svelte b/packages/svelte/tests/runtime-runes/samples/details-binding-initial/main.svelte
new file mode 100644
index 0000000000..fda553038e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/details-binding-initial/main.svelte
@@ -0,0 +1,8 @@
+<script>
+	let open = $state(true);
+</script>
+
+<details bind:open>
+	 <summary>Details</summary>
+	 ...
+</details>