From c3ad8c48f4f0e6e7d33812da7d7a04a5ceff5560 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Thu, 5 Jun 2025 17:23:33 -0400
Subject: [PATCH] WIP

---
 packages/svelte/src/internal/client/reactivity/deriveds.js  | 6 ++++++
 packages/svelte/src/internal/client/reactivity/effects.js   | 6 +++---
 .../tests/runtime-runes/samples/async-error/_config.js      | 1 +
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/packages/svelte/src/internal/client/reactivity/deriveds.js b/packages/svelte/src/internal/client/reactivity/deriveds.js
index 3f21da8e54..fab6e691ff 100644
--- a/packages/svelte/src/internal/client/reactivity/deriveds.js
+++ b/packages/svelte/src/internal/client/reactivity/deriveds.js
@@ -160,9 +160,15 @@ export function async_derived(fn, location) {
 			if (error) {
 				if (error !== STALE_REACTION) {
 					signal.f |= ASYNC_ERROR;
+
+					// @ts-expect-error the error is the wrong type, but we don't care
 					internal_set(signal, error);
 				}
 			} else {
+				if ((signal.f & ASYNC_ERROR) !== 0) {
+					signal.f ^= ASYNC_ERROR;
+				}
+
 				internal_set(signal, value);
 
 				if (DEV && location !== undefined) {
diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index 5a5b4d69f5..f434035ffa 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -339,7 +339,7 @@ export function render_effect(fn, flags = 0) {
  * @param {Array<() => Promise<any>>} async
  */
 export function template_effect(fn, sync = [], async = [], d = derived) {
-	var batch = /** @type {Batch} */ (current_batch);
+	var batch = current_batch;
 	var parent = /** @type {Effect} */ (active_effect);
 
 	if (async.length > 0) {
@@ -349,12 +349,12 @@ export function template_effect(fn, sync = [], async = [], d = derived) {
 			if ((parent.f & DESTROYED) !== 0) return;
 
 			// TODO probably need to do this in async.js as well
-			batch.restore();
+			batch?.restore();
 
 			restore();
 			create_template_effect(fn, [...sync.map(d), ...result]);
 
-			batch.flush();
+			batch?.flush();
 		});
 	} else {
 		create_template_effect(fn, sync.map(d));
diff --git a/packages/svelte/tests/runtime-runes/samples/async-error/_config.js b/packages/svelte/tests/runtime-runes/samples/async-error/_config.js
index 8f6975f6fb..52ac432083 100644
--- a/packages/svelte/tests/runtime-runes/samples/async-error/_config.js
+++ b/packages/svelte/tests/runtime-runes/samples/async-error/_config.js
@@ -10,6 +10,7 @@ export default test({
 		flushSync(() => button1.click());
 		await Promise.resolve();
 		await Promise.resolve();
+		await Promise.resolve();
 		flushSync();
 		assert.htmlEqual(
 			target.innerHTML,