From 01f1937a98ff26589524fb1c8bcab0de2649133f Mon Sep 17 00:00:00 2001
From: Paolo Ricciuti <ricciutipaolo@gmail.com>
Date: Sun, 15 Feb 2026 10:44:23 +0100
Subject: [PATCH] fix: take async into consideration for dev delegated handlers
 (#17710)

Closes #17709

### Before submitting the PR, please make sure you do the following

- [x] It's really useful if your PR references an issue where it is
discussed ahead of time. In many cases, features are absent for a
reason. For large changes, please create an RFC:
https://github.com/sveltejs/rfcs
- [x] Prefix your PR title with `feat:`, `fix:`, `chore:`, or `docs:`.
- [x] This message body should clearly illustrate what problems it
solves.
- [x] Ideally, include a test that fails without this PR but passes with
it.
- [x] If this PR changes code within `packages/svelte/src`, add a
changeset (`npx changeset`).

### Tests and linting

- [x] Run the tests with `pnpm test` and lint the project with `pnpm
lint`
---
 .changeset/lemon-mails-guess.md                          | 5 +++++
 .../phases/3-transform/client/visitors/shared/events.js  | 3 ++-
 .../samples/event-handler-async-delegated/_config.js     | 9 +++++++++
 .../samples/event-handler-async-delegated/main.svelte    | 8 ++++++++
 4 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/lemon-mails-guess.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/event-handler-async-delegated/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/event-handler-async-delegated/main.svelte

diff --git a/.changeset/lemon-mails-guess.md b/.changeset/lemon-mails-guess.md
new file mode 100644
index 0000000000..9156bac953
--- /dev/null
+++ b/.changeset/lemon-mails-guess.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: take async into consideration for dev delegated handlers
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/events.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/events.js
index 9485a33b3d..f01bf08694 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/events.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/events.js
@@ -70,7 +70,8 @@ export function build_event(context, event_name, handler, capture, passive, dele
 		fn = b.function(
 			b.id(name),
 			handler.params,
-			handler.body.type === 'BlockStatement' ? handler.body : b.block([b.return(handler.body)])
+			handler.body.type === 'BlockStatement' ? handler.body : b.block([b.return(handler.body)]),
+			handler.async
 		);
 	}
 
diff --git a/packages/svelte/tests/runtime-runes/samples/event-handler-async-delegated/_config.js b/packages/svelte/tests/runtime-runes/samples/event-handler-async-delegated/_config.js
new file mode 100644
index 0000000000..eb5b2a1675
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/event-handler-async-delegated/_config.js
@@ -0,0 +1,9 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true
+	},
+	async test() {}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/event-handler-async-delegated/main.svelte b/packages/svelte/tests/runtime-runes/samples/event-handler-async-delegated/main.svelte
new file mode 100644
index 0000000000..bffcad6059
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/event-handler-async-delegated/main.svelte
@@ -0,0 +1,8 @@
+<button
+	type="button"
+	onclick={async () => {
+		await Promise.resolve();
+	}}
+>
+	Button
+</button>