From 85e7439e2413b2072a38c1f351be0e02fb753164 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Thu, 10 Jul 2025 09:29:09 -0400
Subject: [PATCH] make it unnecessary to hand onto `current_sources` past the
 initial update

---
 packages/svelte/src/internal/client/proxy.js  | 29 +++++++++++++++----
 .../svelte/src/internal/client/runtime.js     | 12 ++++----
 2 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/packages/svelte/src/internal/client/proxy.js b/packages/svelte/src/internal/client/proxy.js
index 7970d28ae5..5da1b7e188 100644
--- a/packages/svelte/src/internal/client/proxy.js
+++ b/packages/svelte/src/internal/client/proxy.js
@@ -1,6 +1,13 @@
 /** @import { Source } from '#client' */
 import { DEV } from 'esm-env';
-import { get, active_effect, current_sources, set_current_sources } from './runtime.js';
+import {
+	get,
+	active_effect,
+	update_version,
+	active_reaction,
+	set_update_version,
+	set_active_reaction
+} from './runtime.js';
 import {
 	array_prototype,
 	get_descriptor,
@@ -41,7 +48,7 @@ export function proxy(value) {
 	var version = source(0);
 
 	var stack = DEV && tracing_mode_flag ? get_stack('CreatedAt') : null;
-	var parent_sources = current_sources;
+	var parent_version = update_version;
 
 	/**
 	 * Executes the proxy in the context of the reaction it was originally created in, if any
@@ -49,13 +56,23 @@ export function proxy(value) {
 	 * @param {() => T} fn
 	 */
 	var with_parent = (fn) => {
-		var previous_sources = current_sources;
-		set_current_sources(parent_sources);
+		if (update_version === parent_version) {
+			return fn();
+		}
+
+		// child source is being created after the initial proxy —
+		// prevent it from being associated with the current reaction
+		var reaction = active_reaction;
+		var version = update_version;
+
+		set_active_reaction(null);
+		set_update_version(parent_version);
 
-		/** @type {T} */
 		var result = fn();
 
-		set_current_sources(previous_sources);
+		set_active_reaction(reaction);
+		set_update_version(version);
+
 		return result;
 	};
 
diff --git a/packages/svelte/src/internal/client/runtime.js b/packages/svelte/src/internal/client/runtime.js
index 2fe1900933..6477e2942a 100644
--- a/packages/svelte/src/internal/client/runtime.js
+++ b/packages/svelte/src/internal/client/runtime.js
@@ -92,13 +92,6 @@ export function set_active_effect(effect) {
  */
 export let current_sources = null;
 
-/**
- * @param {null | Source[]} value
- */
-export function set_current_sources(value) {
-	current_sources = value;
-}
-
 /** @param {Value} value */
 export function push_reaction_value(value) {
 	if (active_reaction !== null && active_reaction.f & EFFECT_IS_UPDATING) {
@@ -143,6 +136,11 @@ let read_version = 0;
 
 export let update_version = read_version;
 
+/** @param {number} value */
+export function set_update_version(value) {
+	update_version = value;
+}
+
 // If we are working with a get() chain that has no active container,
 // to prevent memory leaks, we skip adding the reaction.
 export let skip_reaction = false;