From 87f7e979635baa46acb594ecc7f2822920cb7aaf Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Mon, 29 Sep 2025 08:05:13 -0700
Subject: [PATCH] fix: wrap async `children` in `$$renderer.async` (#16862)

---
 .changeset/rude-terms-confess.md                           | 5 +++++
 .../phases/3-transform/server/visitors/shared/component.js | 7 ++++++-
 .../samples/async-children/_expected.html                  | 1 +
 .../samples/async-children/component.svelte                | 4 ++++
 .../samples/async-children/main.svelte                     | 7 +++++++
 5 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/rude-terms-confess.md
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/async-children/_expected.html
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/async-children/component.svelte
 create mode 100644 packages/svelte/tests/server-side-rendering/samples/async-children/main.svelte

diff --git a/.changeset/rude-terms-confess.md b/.changeset/rude-terms-confess.md
new file mode 100644
index 0000000000..a24774952e
--- /dev/null
+++ b/.changeset/rude-terms-confess.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: wrap async `children` in `$$renderer.async`
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
index d0de750c0e..e463ea785a 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
@@ -242,7 +242,12 @@ export function build_inline_component(node, expression, context) {
 			params.push(pattern);
 		}
 
-		const slot_fn = b.arrow(params, b.block(block.body));
+		const slot_fn = b.arrow(
+			params,
+			node.fragment.metadata.has_await
+				? b.block([create_async_block(b.block(block.body))])
+				: b.block(block.body)
+		);
 
 		if (slot_name === 'default' && !has_children_prop) {
 			if (
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-children/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-children/_expected.html
new file mode 100644
index 0000000000..04d9709792
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-children/_expected.html
@@ -0,0 +1 @@
+<!--[--><!--[--><!---->1<!--]--><!----><!--]-->
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-children/component.svelte b/packages/svelte/tests/server-side-rendering/samples/async-children/component.svelte
new file mode 100644
index 0000000000..73b5a2f823
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-children/component.svelte
@@ -0,0 +1,4 @@
+<script>
+    const { children } = $props();
+</script>
+{@render children()}
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-children/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-children/main.svelte
new file mode 100644
index 0000000000..ae0fc571b3
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-children/main.svelte
@@ -0,0 +1,7 @@
+<script>
+    import Component from "./component.svelte";
+</script>
+<Component>
+    {@const one = await 1}
+    {one}
+</Component>
\ No newline at end of file