From c0987c09f816b5d7dcb5564d19c849f7e28b9e7a Mon Sep 17 00:00:00 2001
From: subotac <73706465+subotac@users.noreply.github.com>
Date: Fri, 14 Aug 2026 23:50:35 +0300
Subject: [PATCH]  fix: remove stale capture listeners from spread attributes
 (#18618)

Fixes #18608.

When `set_attributes` normalized removed spread attributes, it also
copied its internal `$$` listener bookkeeping keys into `next` with a
`null` value. This cleared the stored callback before event cleanup, so
removing a capture handler passed `null` to `removeEventListener` and
left the listener attached.

Skip internal `$$` keys during missing-attribute normalization. The
updated runtime-runes sample verifies replacing and then removing a
spread capture handler in both client and hydration modes.


---------

Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
---
 .changeset/happy-spoons-talk.md               |  5 +++++
 .../client/dom/elements/attributes.js         |  3 ++-
 .../event-attribute-spread-update/_config.js  | 21 ++++++++++++++++---
 .../event-attribute-spread-update/main.svelte |  3 +++
 4 files changed, 28 insertions(+), 4 deletions(-)
 create mode 100644 .changeset/happy-spoons-talk.md

diff --git a/.changeset/happy-spoons-talk.md b/.changeset/happy-spoons-talk.md
new file mode 100644
index 0000000000..cf165320db
--- /dev/null
+++ b/.changeset/happy-spoons-talk.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: clean up removed capture event handlers from spread attributes
diff --git a/packages/svelte/src/internal/client/dom/elements/attributes.js b/packages/svelte/src/internal/client/dom/elements/attributes.js
index 589685b5f2..8a25be7acd 100644
--- a/packages/svelte/src/internal/client/dom/elements/attributes.js
+++ b/packages/svelte/src/internal/client/dom/elements/attributes.js
@@ -315,7 +315,8 @@ function set_attributes(
 	var is_option_element = element.nodeName === OPTION_TAG;
 
 	for (var key in prev) {
-		if (!(key in next)) {
+		// don't null our internal $$onX listeners
+		if (!(key in next) && key[0] + key[1] !== '$$') {
 			next[key] = null;
 		}
 	}
diff --git a/packages/svelte/tests/runtime-runes/samples/event-attribute-spread-update/_config.js b/packages/svelte/tests/runtime-runes/samples/event-attribute-spread-update/_config.js
index af03eed4c9..5fbd37c768 100644
--- a/packages/svelte/tests/runtime-runes/samples/event-attribute-spread-update/_config.js
+++ b/packages/svelte/tests/runtime-runes/samples/event-attribute-spread-update/_config.js
@@ -3,16 +3,31 @@ import { test } from '../../test';
 
 export default test({
 	test({ assert, target }) {
-		const [change, increment] = target.querySelectorAll('button');
+		const [change, remove, increment] = target.querySelectorAll('button');
 
 		increment.click();
 		flushSync();
-		assert.htmlEqual(target.innerHTML, '<button>change handlers</button><button>1 / 1</button>');
+		assert.htmlEqual(
+			target.innerHTML,
+			'<button>change handlers</button><button>remove capture handler</button><button>1 / 1</button>'
+		);
 
 		change.click();
 		flushSync();
 		increment.click();
 		flushSync();
-		assert.htmlEqual(target.innerHTML, '<button>change handlers</button><button>3 / 3</button>');
+		assert.htmlEqual(
+			target.innerHTML,
+			'<button>change handlers</button><button>remove capture handler</button><button>3 / 3</button>'
+		);
+
+		remove.click();
+		flushSync();
+		increment.click();
+		flushSync();
+		assert.htmlEqual(
+			target.innerHTML,
+			'<button>change handlers</button><button>remove capture handler</button><button>5 / 3</button>'
+		);
 	}
 });
diff --git a/packages/svelte/tests/runtime-runes/samples/event-attribute-spread-update/main.svelte b/packages/svelte/tests/runtime-runes/samples/event-attribute-spread-update/main.svelte
index 32d4b242cc..ee049e469c 100644
--- a/packages/svelte/tests/runtime-runes/samples/event-attribute-spread-update/main.svelte
+++ b/packages/svelte/tests/runtime-runes/samples/event-attribute-spread-update/main.svelte
@@ -24,4 +24,7 @@
 >
 	change handlers
 </button>
+<button onclick={() => (attrs = { onclick: attrs.onclick, onclickcapture: undefined })}>
+	remove capture handler
+</button>
 <button {...attrs}>{delegated} / {non_delegated}</button>