From 7dc864d94160164ae9f835b51aed24f3e4c6f539 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Thu, 5 Mar 2026 21:34:38 -0500
Subject: [PATCH] Revert "fix: skip derived re-evaluation inside inert effect
 blocks" (#17869)

Reverts sveltejs/svelte#17852, because it isn't a real fix
https://github.com/sveltejs/svelte/pull/17868
---
 .changeset/chatty-papers-sing.md              |  5 ---
 .../internal/client/reactivity/deriveds.js    | 17 ++--------
 .../if-block-const-inert-derived/_config.js   | 18 -----------
 .../if-block-const-inert-derived/main.svelte  | 32 -------------------
 4 files changed, 2 insertions(+), 70 deletions(-)
 delete mode 100644 .changeset/chatty-papers-sing.md
 delete mode 100644 packages/svelte/tests/runtime-runes/samples/if-block-const-inert-derived/_config.js
 delete mode 100644 packages/svelte/tests/runtime-runes/samples/if-block-const-inert-derived/main.svelte

diff --git a/.changeset/chatty-papers-sing.md b/.changeset/chatty-papers-sing.md
deleted file mode 100644
index 4d85b91bfc..0000000000
--- a/.changeset/chatty-papers-sing.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: skip derived re-evaluation inside inert effect blocks
diff --git a/packages/svelte/src/internal/client/reactivity/deriveds.js b/packages/svelte/src/internal/client/reactivity/deriveds.js
index 2c9b9da33e..7df7651294 100644
--- a/packages/svelte/src/internal/client/reactivity/deriveds.js
+++ b/packages/svelte/src/internal/client/reactivity/deriveds.js
@@ -10,8 +10,7 @@ import {
 	ASYNC,
 	WAS_MARKED,
 	DESTROYED,
-	CLEAN,
-	INERT
+	CLEAN
 } from '#client/constants';
 import {
 	active_reaction,
@@ -306,22 +305,10 @@ function get_derived_parent_effect(derived) {
  * @returns {T}
  */
 export function execute_derived(derived) {
-	var parent_effect = get_derived_parent_effect(derived);
-
-	// don't update `{@const ...}` in an outroing block
-	if (
-		!async_mode_flag &&
-		!is_destroying_effect &&
-		parent_effect !== null &&
-		(parent_effect.f & INERT) !== 0
-	) {
-		return derived.v;
-	}
-
 	var value;
 	var prev_active_effect = active_effect;
 
-	set_active_effect(parent_effect);
+	set_active_effect(get_derived_parent_effect(derived));
 
 	if (DEV) {
 		let prev_eager_effects = eager_effects;
diff --git a/packages/svelte/tests/runtime-runes/samples/if-block-const-inert-derived/_config.js b/packages/svelte/tests/runtime-runes/samples/if-block-const-inert-derived/_config.js
deleted file mode 100644
index b803182079..0000000000
--- a/packages/svelte/tests/runtime-runes/samples/if-block-const-inert-derived/_config.js
+++ /dev/null
@@ -1,18 +0,0 @@
-import { flushSync, tick } from 'svelte';
-import { test } from '../../test';
-
-export default test({
-	html: '<button>clear</button><div><p>hello</p></div>',
-
-	async test({ assert, target, raf, logs }) {
-		const [button] = target.querySelectorAll('button');
-
-		flushSync(() => button.click());
-		assert.deepEqual(logs, ['hello']);
-
-		// Let the transition finish and clean up
-		raf.tick(100);
-
-		assert.htmlEqual(target.innerHTML, '<button>clear</button>');
-	}
-});
diff --git a/packages/svelte/tests/runtime-runes/samples/if-block-const-inert-derived/main.svelte b/packages/svelte/tests/runtime-runes/samples/if-block-const-inert-derived/main.svelte
deleted file mode 100644
index 58b34d52b9..0000000000
--- a/packages/svelte/tests/runtime-runes/samples/if-block-const-inert-derived/main.svelte
+++ /dev/null
@@ -1,32 +0,0 @@
-<script>
-	let value = $state('hello');
-
-	function compute(v) {
-		console.log(v);
-		return { data: v, ready: true };
-	}
-
-	function fade(node) {
-		return {
-			duration: 100,
-			tick: (t) => {
-				node.style.opacity = String(t);
-			}
-		};
-	}
-</script>
-
-<button
-	onclick={() => {
-		value = undefined;
-	}}>clear</button
->
-
-{#if value}
-	{@const result = compute(value)}
-	{#if result.ready}
-		<div out:fade|global>
-			<p>{result.data}</p>
-		</div>
-	{/if}
-{/if}