From c745945e9ec92f6e2809b11f4e68594cee6dd36f Mon Sep 17 00:00:00 2001
From: ComputerGuy <63362464+Ocean-OS@users.noreply.github.com>
Date: Thu, 14 Aug 2025 10:45:41 -0700
Subject: [PATCH] fix: avoid recursion error when tagging circular references

---
 .changeset/six-shirts-scream.md               |  5 +++
 .../svelte/src/internal/client/dev/tracing.js |  7 +++--
 packages/svelte/src/internal/client/proxy.js  | 31 ++++++++++++++-----
 .../src/internal/client/reactivity/sources.js |  2 +-
 4 files changed, 34 insertions(+), 11 deletions(-)
 create mode 100644 .changeset/six-shirts-scream.md

diff --git a/.changeset/six-shirts-scream.md b/.changeset/six-shirts-scream.md
new file mode 100644
index 0000000000..ac4d183474
--- /dev/null
+++ b/.changeset/six-shirts-scream.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: avoid recursion error when tagging circular references
diff --git a/packages/svelte/src/internal/client/dev/tracing.js b/packages/svelte/src/internal/client/dev/tracing.js
index 673a710fac..06b0055cb9 100644
--- a/packages/svelte/src/internal/client/dev/tracing.js
+++ b/packages/svelte/src/internal/client/dev/tracing.js
@@ -179,7 +179,7 @@ export function get_stack(label) {
  */
 export function tag(source, label) {
 	source.label = label;
-	tag_proxy(source.v, label);
+	tag_proxy(source.v, label, source);
 
 	return source;
 }
@@ -187,10 +187,11 @@ export function tag(source, label) {
 /**
  * @param {unknown} value
  * @param {string} label
+ * @param {Value} source
  */
-export function tag_proxy(value, label) {
+export function tag_proxy(value, label, source) {
 	// @ts-expect-error
-	value?.[PROXY_PATH_SYMBOL]?.(label);
+	value?.[PROXY_PATH_SYMBOL]?.(label, source);
 	return value;
 }
 
diff --git a/packages/svelte/src/internal/client/proxy.js b/packages/svelte/src/internal/client/proxy.js
index 3ae4b87ed5..e39b8d6106 100644
--- a/packages/svelte/src/internal/client/proxy.js
+++ b/packages/svelte/src/internal/client/proxy.js
@@ -34,9 +34,13 @@ const regex_is_valid_identifier = /^[a-zA-Z_$][a-zA-Z_$0-9]*$/;
 /**
  * @template T
  * @param {T} value
+ * @param {WeakSet<Source>} [owned_sources]
  * @returns {T}
  */
-export function proxy(value) {
+export function proxy(value, owned_sources) {
+	if (DEV) {
+		owned_sources ??= new WeakSet();
+	}
 	// if non-proxyable, or is already a proxy, return `value`
 	if (typeof value !== 'object' || value === null || STATE_SYMBOL in value) {
 		return value;
@@ -94,8 +98,15 @@ export function proxy(value) {
 	/** Used in dev for $inspect.trace() */
 	var path = '';
 
-	/** @param {string} new_path */
-	function update_path(new_path) {
+	/**
+	 * @param {string} new_path
+	 * @param {Source} updater the source causing the path update
+	 */
+	function update_path(new_path, updater) {
+		// there's a circular reference somewhere, don't update the path to avoid recursion
+		if (owned_sources?.has(updater)) {
+			return;
+		}
 		path = new_path;
 
 		tag(version, `${path} version`);
@@ -127,6 +138,7 @@ export function proxy(value) {
 					sources.set(prop, s);
 					if (DEV && typeof prop === 'string') {
 						tag(s, get_label(path, prop));
+						owned_sources?.add(s);
 					}
 					return s;
 				});
@@ -148,6 +160,7 @@ export function proxy(value) {
 
 					if (DEV) {
 						tag(s, get_label(path, prop));
+						owned_sources?.add(s);
 					}
 				}
 			} else {
@@ -173,11 +186,12 @@ export function proxy(value) {
 			// create a source, but only if it's an own property and not a prototype property
 			if (s === undefined && (!exists || get_descriptor(target, prop)?.writable)) {
 				s = with_parent(() => {
-					var p = proxy(exists ? target[prop] : UNINITIALIZED);
+					var p = proxy(exists ? target[prop] : UNINITIALIZED, DEV ? owned_sources : undefined);
 					var s = source(p, stack);
 
 					if (DEV) {
 						tag(s, get_label(path, prop));
+						owned_sources?.add(s);
 					}
 
 					return s;
@@ -231,11 +245,12 @@ export function proxy(value) {
 			) {
 				if (s === undefined) {
 					s = with_parent(() => {
-						var p = has ? proxy(target[prop]) : UNINITIALIZED;
+						var p = has ? proxy(target[prop], DEV ? owned_sources : undefined) : UNINITIALIZED;
 						var s = source(p, stack);
 
 						if (DEV) {
 							tag(s, get_label(path, prop));
+							owned_sources?.add(s);
 						}
 
 						return s;
@@ -272,6 +287,7 @@ export function proxy(value) {
 
 						if (DEV) {
 							tag(other_s, get_label(path, i));
+							owned_sources?.add(other_s);
 						}
 					}
 				}
@@ -284,18 +300,19 @@ export function proxy(value) {
 			if (s === undefined) {
 				if (!has || get_descriptor(target, prop)?.writable) {
 					s = with_parent(() => source(undefined, stack));
-					set(s, proxy(value));
+					set(s, proxy(value, DEV ? owned_sources : undefined));
 
 					sources.set(prop, s);
 
 					if (DEV) {
 						tag(s, get_label(path, prop));
+						owned_sources?.add(s);
 					}
 				}
 			} else {
 				has = s.v !== UNINITIALIZED;
 
-				var p = with_parent(() => proxy(value));
+				var p = with_parent(() => proxy(value, DEV ? owned_sources : undefined));
 				set(s, p);
 			}
 
diff --git a/packages/svelte/src/internal/client/reactivity/sources.js b/packages/svelte/src/internal/client/reactivity/sources.js
index 7fb3135708..45582d4f9f 100644
--- a/packages/svelte/src/internal/client/reactivity/sources.js
+++ b/packages/svelte/src/internal/client/reactivity/sources.js
@@ -156,7 +156,7 @@ export function set(source, value, should_proxy = false) {
 	let new_value = should_proxy ? proxy(value) : value;
 
 	if (DEV) {
-		tag_proxy(new_value, /** @type {string} */ (source.label));
+		tag_proxy(new_value, /** @type {string} */ (source.label), source);
 	}
 
 	return internal_set(source, new_value);