From 9d74ecbd026de4a1324f2c98087d6f34d0b25fb1 Mon Sep 17 00:00:00 2001
From: Jungzl <13jungzl@gmail.com>
Date: Mon, 29 Sep 2025 11:14:33 +0800
Subject: [PATCH 1/2] fix: preserve tuple type in `$state.snapshot`

---
 .changeset/lucky-moles-enjoy.md  |  5 +++++
 packages/svelte/src/ambient.d.ts | 16 +++++++++-------
 packages/svelte/types/index.d.ts | 16 +++++++++-------
 3 files changed, 23 insertions(+), 14 deletions(-)
 create mode 100644 .changeset/lucky-moles-enjoy.md

diff --git a/.changeset/lucky-moles-enjoy.md b/.changeset/lucky-moles-enjoy.md
new file mode 100644
index 000000000000..6802de34d35c
--- /dev/null
+++ b/.changeset/lucky-moles-enjoy.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+preserve tuple type in `$state.snapshot`
diff --git a/packages/svelte/src/ambient.d.ts b/packages/svelte/src/ambient.d.ts
index 59128e45f002..d655fb648a2f 100644
--- a/packages/svelte/src/ambient.d.ts
+++ b/packages/svelte/src/ambient.d.ts
@@ -85,13 +85,15 @@ declare namespace $state {
 			? NonReactive<T>
 			: T extends { toJSON(): infer R }
 				? R
-				: T extends Array<infer U>
-					? Array<Snapshot<U>>
-					: T extends object
-						? T extends { [key: string]: any }
-							? { [K in keyof T]: Snapshot<T[K]> }
-							: never
-						: never;
+				: T extends readonly unknown[]
+					? { [K in keyof T]: Snapshot<T[K]> }
+					: T extends Array<infer U>
+						? Array<Snapshot<U>>
+						: T extends object
+							? T extends { [key: string]: any }
+								? { [K in keyof T]: Snapshot<T[K]> }
+								: never
+							: never;
 
 	/**
 	 * Declares state that is _not_ made deeply reactive — instead of mutating it,
diff --git a/packages/svelte/types/index.d.ts b/packages/svelte/types/index.d.ts
index 2c015b5a10ae..6dc6629faad5 100644
--- a/packages/svelte/types/index.d.ts
+++ b/packages/svelte/types/index.d.ts
@@ -3171,13 +3171,15 @@ declare namespace $state {
 			? NonReactive<T>
 			: T extends { toJSON(): infer R }
 				? R
-				: T extends Array<infer U>
-					? Array<Snapshot<U>>
-					: T extends object
-						? T extends { [key: string]: any }
-							? { [K in keyof T]: Snapshot<T[K]> }
-							: never
-						: never;
+				: T extends readonly unknown[]
+					? { [K in keyof T]: Snapshot<T[K]> }
+					: T extends Array<infer U>
+						? Array<Snapshot<U>>
+						: T extends object
+							? T extends { [key: string]: any }
+								? { [K in keyof T]: Snapshot<T[K]> }
+								: never
+							: never;
 
 	/**
 	 * Declares state that is _not_ made deeply reactive — instead of mutating it,

From 5edc0ab6747b9917e1fc8a0ba18ec5466e77320e Mon Sep 17 00:00:00 2001
From: Rich Harris <hello@rich-harris.dev>
Date: Wed, 1 Oct 2025 11:57:31 -0400
Subject: [PATCH 2/2] Update .changeset/lucky-moles-enjoy.md

---
 .changeset/lucky-moles-enjoy.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.changeset/lucky-moles-enjoy.md b/.changeset/lucky-moles-enjoy.md
index 6802de34d35c..ef1dfe4bdd69 100644
--- a/.changeset/lucky-moles-enjoy.md
+++ b/.changeset/lucky-moles-enjoy.md
@@ -2,4 +2,4 @@
 'svelte': patch
 ---
 
-preserve tuple type in `$state.snapshot`
+fix: preserve tuple type in `$state.snapshot`