From 23b44ced5225bbcf4a3133c5c3f8514b77f4ffd5 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Tue, 22 Jul 2025 16:57:22 -0400
Subject: [PATCH] fix #16477

---
 packages/svelte/src/internal/client/reactivity/batch.js   | 8 ++++++--
 .../samples/1000-reading-derived-effects/Component.svelte | 7 +++++++
 .../samples/1000-reading-derived-effects/_config.js       | 5 +++++
 .../samples/1000-reading-derived-effects/main.svelte      | 8 ++++++++
 4 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/Component.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/main.svelte

diff --git a/packages/svelte/src/internal/client/reactivity/batch.js b/packages/svelte/src/internal/client/reactivity/batch.js
index 2c95985500..ea4698073c 100644
--- a/packages/svelte/src/internal/client/reactivity/batch.js
+++ b/packages/svelte/src/internal/client/reactivity/batch.js
@@ -563,7 +563,7 @@ function flush_queued_effects(effects) {
 		var effect = effects[i++];
 
 		if ((effect.f & (DESTROYED | INERT)) === 0 && is_dirty(effect)) {
-			var wv = write_version;
+			var n = current_batch ? current_batch.current.size : 0;
 
 			update_effect(effect);
 
@@ -586,7 +586,11 @@ function flush_queued_effects(effects) {
 
 			// if state is written in a user effect, abort and re-schedule, lest we run
 			// effects that should be removed as a result of the state change
-			if (write_version > wv && (effect.f & USER_EFFECT) !== 0) {
+			if (
+				current_batch !== null &&
+				current_batch.current.size > n &&
+				(effect.f & USER_EFFECT) !== 0
+			) {
 				break;
 			}
 		}
diff --git a/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/Component.svelte b/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/Component.svelte
new file mode 100644
index 0000000000..7a54323cb9
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/Component.svelte
@@ -0,0 +1,7 @@
+<script>
+	const der = $derived(false);
+
+	$effect(() => {
+		der
+	});
+</script>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/_config.js b/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/_config.js
new file mode 100644
index 0000000000..2e4a27cf09
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/_config.js
@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	async test() {}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/main.svelte b/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/main.svelte
new file mode 100644
index 0000000000..258918e903
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/1000-reading-derived-effects/main.svelte
@@ -0,0 +1,8 @@
+<script>
+	import Component from './Component.svelte'	
+	const arr = Array.from({length: 10001});
+</script>
+
+{#each arr}
+	<Component />
+{/each}