From 2af7ba21563f1b7f011ffa9f0c08e4acb473eef3 Mon Sep 17 00:00:00 2001
From: Fedor Nezhivoi <gyzerok@users.noreply.github.com>
Date: Tue, 24 Jun 2025 20:05:24 +0700
Subject: [PATCH 1/3] fix: lift unsafe_state_mutation constraints for SvelteSet
 and SvelteMap created inside the derived (#16221)

Co-authored-by: Fedor Nezhivoi <f.nezhivoi@corp.vk.com>
---
 .changeset/fair-bats-visit.md                 |  5 ++++
 packages/svelte/src/reactivity/date.js        |  4 +--
 packages/svelte/src/reactivity/map.js         |  6 ++---
 packages/svelte/src/reactivity/set.js         |  6 ++---
 .../src/reactivity/url-search-params.js       |  4 +--
 packages/svelte/src/reactivity/url.js         | 18 ++++++-------
 .../side-effect-derived-array/_config.js      | 23 ++++++++++++++++
 .../side-effect-derived-array/main.svelte     | 25 +++++++++++++++++
 .../side-effect-derived-date/_config.js       | 23 ++++++++++++++++
 .../side-effect-derived-date/main.svelte      | 27 +++++++++++++++++++
 .../side-effect-derived-map/_config.js        | 23 ++++++++++++++++
 .../side-effect-derived-map/main.svelte       | 27 +++++++++++++++++++
 .../side-effect-derived-object/_config.js     | 23 ++++++++++++++++
 .../side-effect-derived-object/main.svelte    | 25 +++++++++++++++++
 .../side-effect-derived-primitive/_config.js  | 23 ++++++++++++++++
 .../side-effect-derived-primitive/main.svelte | 25 +++++++++++++++++
 .../side-effect-derived-set/_config.js        | 23 ++++++++++++++++
 .../side-effect-derived-set/main.svelte       | 27 +++++++++++++++++++
 .../_config.js                                | 23 ++++++++++++++++
 .../main.svelte                               | 27 +++++++++++++++++++
 .../side-effect-derived-url/_config.js        | 23 ++++++++++++++++
 .../side-effect-derived-url/main.svelte       | 27 +++++++++++++++++++
 22 files changed, 418 insertions(+), 19 deletions(-)
 create mode 100644 .changeset/fair-bats-visit.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-array/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-array/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-date/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-date/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-map/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-map/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-object/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-object/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-primitive/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-primitive/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-set/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-set/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-url-search-params/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-url-search-params/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-url/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/side-effect-derived-url/main.svelte

diff --git a/.changeset/fair-bats-visit.md b/.changeset/fair-bats-visit.md
new file mode 100644
index 0000000000..bc0a426395
--- /dev/null
+++ b/.changeset/fair-bats-visit.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+lift unsafe_state_mutation constraints for SvelteSet, SvelteMap, SvelteDate, SvelteURL and SvelteURLSearchParams created inside the derived
diff --git a/packages/svelte/src/reactivity/date.js b/packages/svelte/src/reactivity/date.js
index 4176f0ceec..8e2b5d41ab 100644
--- a/packages/svelte/src/reactivity/date.js
+++ b/packages/svelte/src/reactivity/date.js
@@ -1,6 +1,6 @@
 /** @import { Source } from '#client' */
 import { derived } from '../internal/client/index.js';
-import { source, set } from '../internal/client/reactivity/sources.js';
+import { set, state } from '../internal/client/reactivity/sources.js';
 import { tag } from '../internal/client/dev/tracing.js';
 import { active_reaction, get, set_active_reaction } from '../internal/client/runtime.js';
 import { DEV } from 'esm-env';
@@ -40,7 +40,7 @@ var inited = false;
  * ```
  */
 export class SvelteDate extends Date {
-	#time = source(super.getTime());
+	#time = state(super.getTime());
 
 	/** @type {Map<keyof Date, Source<unknown>>} */
 	#deriveds = new Map();
diff --git a/packages/svelte/src/reactivity/map.js b/packages/svelte/src/reactivity/map.js
index eed163dbf2..cd2fac163f 100644
--- a/packages/svelte/src/reactivity/map.js
+++ b/packages/svelte/src/reactivity/map.js
@@ -1,6 +1,6 @@
 /** @import { Source } from '#client' */
 import { DEV } from 'esm-env';
-import { set, source } from '../internal/client/reactivity/sources.js';
+import { set, source, state } from '../internal/client/reactivity/sources.js';
 import { label, tag } from '../internal/client/dev/tracing.js';
 import { get } from '../internal/client/runtime.js';
 import { increment } from './utils.js';
@@ -54,8 +54,8 @@ import { increment } from './utils.js';
 export class SvelteMap extends Map {
 	/** @type {Map<K, Source<number>>} */
 	#sources = new Map();
-	#version = source(0);
-	#size = source(0);
+	#version = state(0);
+	#size = state(0);
 
 	/**
 	 * @param {Iterable<readonly [K, V]> | null | undefined} [value]
diff --git a/packages/svelte/src/reactivity/set.js b/packages/svelte/src/reactivity/set.js
index fd22014cb3..8a656c2bc1 100644
--- a/packages/svelte/src/reactivity/set.js
+++ b/packages/svelte/src/reactivity/set.js
@@ -1,6 +1,6 @@
 /** @import { Source } from '#client' */
 import { DEV } from 'esm-env';
-import { source, set } from '../internal/client/reactivity/sources.js';
+import { source, set, state } from '../internal/client/reactivity/sources.js';
 import { label, tag } from '../internal/client/dev/tracing.js';
 import { get } from '../internal/client/runtime.js';
 import { increment } from './utils.js';
@@ -48,8 +48,8 @@ var inited = false;
 export class SvelteSet extends Set {
 	/** @type {Map<T, Source<boolean>>} */
 	#sources = new Map();
-	#version = source(0);
-	#size = source(0);
+	#version = state(0);
+	#size = state(0);
 
 	/**
 	 * @param {Iterable<T> | null | undefined} [value]
diff --git a/packages/svelte/src/reactivity/url-search-params.js b/packages/svelte/src/reactivity/url-search-params.js
index c77ff9c822..389da7cdb6 100644
--- a/packages/svelte/src/reactivity/url-search-params.js
+++ b/packages/svelte/src/reactivity/url-search-params.js
@@ -1,5 +1,5 @@
 import { DEV } from 'esm-env';
-import { source } from '../internal/client/reactivity/sources.js';
+import { state } from '../internal/client/reactivity/sources.js';
 import { tag } from '../internal/client/dev/tracing.js';
 import { get } from '../internal/client/runtime.js';
 import { get_current_url } from './url.js';
@@ -34,7 +34,7 @@ export const REPLACE = Symbol();
  * ```
  */
 export class SvelteURLSearchParams extends URLSearchParams {
-	#version = DEV ? tag(source(0), 'SvelteURLSearchParams version') : source(0);
+	#version = DEV ? tag(state(0), 'SvelteURLSearchParams version') : state(0);
 	#url = get_current_url();
 
 	#updating = false;
diff --git a/packages/svelte/src/reactivity/url.js b/packages/svelte/src/reactivity/url.js
index 56732a0402..dfede23f6e 100644
--- a/packages/svelte/src/reactivity/url.js
+++ b/packages/svelte/src/reactivity/url.js
@@ -1,5 +1,5 @@
 import { DEV } from 'esm-env';
-import { source, set } from '../internal/client/reactivity/sources.js';
+import { set, state } from '../internal/client/reactivity/sources.js';
 import { tag } from '../internal/client/dev/tracing.js';
 import { get } from '../internal/client/runtime.js';
 import { REPLACE, SvelteURLSearchParams } from './url-search-params.js';
@@ -40,14 +40,14 @@ export function get_current_url() {
  * ```
  */
 export class SvelteURL extends URL {
-	#protocol = source(super.protocol);
-	#username = source(super.username);
-	#password = source(super.password);
-	#hostname = source(super.hostname);
-	#port = source(super.port);
-	#pathname = source(super.pathname);
-	#hash = source(super.hash);
-	#search = source(super.search);
+	#protocol = state(super.protocol);
+	#username = state(super.username);
+	#password = state(super.password);
+	#hostname = state(super.hostname);
+	#port = state(super.port);
+	#pathname = state(super.pathname);
+	#hash = state(super.hash);
+	#search = state(super.search);
 	#searchParams;
 
 	/**
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-array/_config.js b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-array/_config.js
new file mode 100644
index 0000000000..5ad6f57e31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-array/_config.js
@@ -0,0 +1,23 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true,
+		runes: true
+	},
+
+	test({ assert, target }) {
+		const [button1, button2] = target.querySelectorAll('button');
+
+		assert.throws(() => {
+			button1?.click();
+			flushSync();
+		}, /state_unsafe_mutation/);
+
+		assert.doesNotThrow(() => {
+			button2?.click();
+			flushSync();
+		});
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-array/main.svelte b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-array/main.svelte
new file mode 100644
index 0000000000..6468dbebc9
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-array/main.svelte
@@ -0,0 +1,25 @@
+<script>
+	let visibleExternal = $state(false);
+	let external = $state([]);
+	const throws = $derived.by(() => {
+		external.push(1);
+		return external;
+	});
+
+	let visibleInternal = $state(false)
+	const works = $derived.by(() => {
+		let internal = $state([]);
+		internal.push(1);
+		return internal;
+	});
+</script>
+
+<button onclick={() => (visibleExternal = true)}>external</button>
+{#if visibleExternal}
+	{throws}
+{/if}
+<button onclick={() => (visibleInternal = true)}>internal</button>
+{#if visibleInternal}
+	{works}
+{/if}
+
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-date/_config.js b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-date/_config.js
new file mode 100644
index 0000000000..5ad6f57e31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-date/_config.js
@@ -0,0 +1,23 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true,
+		runes: true
+	},
+
+	test({ assert, target }) {
+		const [button1, button2] = target.querySelectorAll('button');
+
+		assert.throws(() => {
+			button1?.click();
+			flushSync();
+		}, /state_unsafe_mutation/);
+
+		assert.doesNotThrow(() => {
+			button2?.click();
+			flushSync();
+		});
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-date/main.svelte b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-date/main.svelte
new file mode 100644
index 0000000000..a3c6aa629f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-date/main.svelte
@@ -0,0 +1,27 @@
+<script>
+	import { SvelteDate } from 'svelte/reactivity';
+
+	let visibleExternal = $state(false);
+	let external = new SvelteDate();
+	const throws = $derived.by(() => {
+		external.setTime(12345);
+		return external;
+	})
+
+	let visibleInternal = $state(false);
+	const works = $derived.by(() => {
+		let internal = new SvelteDate();
+		internal.setTime(12345);
+		return internal;
+	})
+</script>
+
+<button onclick={() => (visibleExternal = true)}>external</button>
+{#if visibleExternal}
+	{throws}
+{/if}
+<button onclick={() => (visibleInternal = true)}>internal</button>
+{#if visibleInternal}
+	{works}
+{/if}
+
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-map/_config.js b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-map/_config.js
new file mode 100644
index 0000000000..5ad6f57e31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-map/_config.js
@@ -0,0 +1,23 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true,
+		runes: true
+	},
+
+	test({ assert, target }) {
+		const [button1, button2] = target.querySelectorAll('button');
+
+		assert.throws(() => {
+			button1?.click();
+			flushSync();
+		}, /state_unsafe_mutation/);
+
+		assert.doesNotThrow(() => {
+			button2?.click();
+			flushSync();
+		});
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-map/main.svelte b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-map/main.svelte
new file mode 100644
index 0000000000..bdd5ccb75c
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-map/main.svelte
@@ -0,0 +1,27 @@
+<script>
+	import { SvelteMap } from 'svelte/reactivity';
+
+	let visibleExternal = $state(false);
+	let external = new SvelteMap();
+	const throws = $derived.by(() => {
+		external.set(1, 1);
+		return external;
+	});
+
+	let visibleInternal = $state(false);
+	const works = $derived.by(() => {
+		let internal = new SvelteMap();
+		internal.set(1, 1);
+		return internal;
+	});
+</script>
+
+<button onclick={() => (visibleExternal = true)}>external</button>
+{#if visibleExternal}
+	{throws}
+{/if}
+<button onclick={() => (visibleInternal = true)}>internal</button>
+{#if visibleInternal}
+	{works}
+{/if}
+
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-object/_config.js b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-object/_config.js
new file mode 100644
index 0000000000..5ad6f57e31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-object/_config.js
@@ -0,0 +1,23 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true,
+		runes: true
+	},
+
+	test({ assert, target }) {
+		const [button1, button2] = target.querySelectorAll('button');
+
+		assert.throws(() => {
+			button1?.click();
+			flushSync();
+		}, /state_unsafe_mutation/);
+
+		assert.doesNotThrow(() => {
+			button2?.click();
+			flushSync();
+		});
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-object/main.svelte b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-object/main.svelte
new file mode 100644
index 0000000000..2174bde59f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-object/main.svelte
@@ -0,0 +1,25 @@
+<script>
+	let visibleExternal = $state(false);
+	let external = $state({ v: 1 });
+	const throws = $derived.by(() => {
+		external.v = 2;
+		return external;
+	});
+
+	let visibleInternal = $state(false)
+	const works = $derived.by(() => {
+		let internal = $state({ v: 1 });
+		internal.v = 2;
+		return internal;
+	});
+</script>
+
+<button onclick={() => (visibleExternal = true)}>external</button>
+{#if visibleExternal}
+	{throws}
+{/if}
+<button onclick={() => (visibleInternal = true)}>internal</button>
+{#if visibleInternal}
+	{works}
+{/if}
+
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-primitive/_config.js b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-primitive/_config.js
new file mode 100644
index 0000000000..5ad6f57e31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-primitive/_config.js
@@ -0,0 +1,23 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true,
+		runes: true
+	},
+
+	test({ assert, target }) {
+		const [button1, button2] = target.querySelectorAll('button');
+
+		assert.throws(() => {
+			button1?.click();
+			flushSync();
+		}, /state_unsafe_mutation/);
+
+		assert.doesNotThrow(() => {
+			button2?.click();
+			flushSync();
+		});
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-primitive/main.svelte b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-primitive/main.svelte
new file mode 100644
index 0000000000..21de8b9d91
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-primitive/main.svelte
@@ -0,0 +1,25 @@
+<script>
+	let visibleExternal = $state(false);
+	let external = $state(1);
+	const throws = $derived.by(() => {
+		external = 2;
+		return external;
+	});
+
+	let visibleInternal = $state(false);
+	const works = $derived.by(() => {
+		let internal = $state(1);
+		internal = 2;
+		return internal;
+	});
+</script>
+
+<button onclick={() => (visibleExternal = true)}>external</button>
+{#if visibleExternal}
+	{throws}
+{/if}
+<button onclick={() => (visibleInternal = true)}>internal</button>
+{#if visibleInternal}
+	{works}
+{/if}
+
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-set/_config.js b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-set/_config.js
new file mode 100644
index 0000000000..5ad6f57e31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-set/_config.js
@@ -0,0 +1,23 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true,
+		runes: true
+	},
+
+	test({ assert, target }) {
+		const [button1, button2] = target.querySelectorAll('button');
+
+		assert.throws(() => {
+			button1?.click();
+			flushSync();
+		}, /state_unsafe_mutation/);
+
+		assert.doesNotThrow(() => {
+			button2?.click();
+			flushSync();
+		});
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-set/main.svelte b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-set/main.svelte
new file mode 100644
index 0000000000..8564f6e7c4
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-set/main.svelte
@@ -0,0 +1,27 @@
+<script>
+	import { SvelteSet } from 'svelte/reactivity';
+
+	let visibleExternal = $state(false);
+	let external = new SvelteSet();
+	const throws = $derived.by(() => {
+		external.add(1);
+		return external;
+	})
+
+	let visibleInternal = $state(false);
+	const works = $derived.by(() => {
+		let internal = new SvelteSet();
+		internal.add(1);
+		return internal;
+	})
+</script>
+
+<button onclick={() => (visibleExternal = true)}>external</button>
+{#if visibleExternal}
+	{throws}
+{/if}
+<button onclick={() => (visibleInternal = true)}>internal</button>
+{#if visibleInternal}
+	{works}
+{/if}
+
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url-search-params/_config.js b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url-search-params/_config.js
new file mode 100644
index 0000000000..5ad6f57e31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url-search-params/_config.js
@@ -0,0 +1,23 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true,
+		runes: true
+	},
+
+	test({ assert, target }) {
+		const [button1, button2] = target.querySelectorAll('button');
+
+		assert.throws(() => {
+			button1?.click();
+			flushSync();
+		}, /state_unsafe_mutation/);
+
+		assert.doesNotThrow(() => {
+			button2?.click();
+			flushSync();
+		});
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url-search-params/main.svelte b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url-search-params/main.svelte
new file mode 100644
index 0000000000..014a1e4e6d
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url-search-params/main.svelte
@@ -0,0 +1,27 @@
+<script>
+	import { SvelteURLSearchParams } from 'svelte/reactivity';
+
+	let visibleExternal = $state(false);
+	let external = new SvelteURLSearchParams();
+	const throws = $derived.by(() => {
+		external.append('foo', 'bar')
+		return external;
+	})
+
+	let visibleInternal = $state(false);
+	const works = $derived.by(() => {
+		let internal = new SvelteURLSearchParams();
+		internal.append('foo', 'bar')
+		return internal;
+	})
+</script>
+
+<button onclick={() => (visibleExternal = true)}>external</button>
+{#if visibleExternal}
+	{throws}
+{/if}
+<button onclick={() => (visibleInternal = true)}>internal</button>
+{#if visibleInternal}
+	{works}
+{/if}
+
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url/_config.js b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url/_config.js
new file mode 100644
index 0000000000..5ad6f57e31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url/_config.js
@@ -0,0 +1,23 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: {
+		dev: true,
+		runes: true
+	},
+
+	test({ assert, target }) {
+		const [button1, button2] = target.querySelectorAll('button');
+
+		assert.throws(() => {
+			button1?.click();
+			flushSync();
+		}, /state_unsafe_mutation/);
+
+		assert.doesNotThrow(() => {
+			button2?.click();
+			flushSync();
+		});
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url/main.svelte b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url/main.svelte
new file mode 100644
index 0000000000..69ead384c3
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/side-effect-derived-url/main.svelte
@@ -0,0 +1,27 @@
+<script>
+	import { SvelteURL } from 'svelte/reactivity';
+
+	let visibleExternal = $state(false);
+	let external = new SvelteURL('https://svelte.dev');
+	const throws = $derived.by(() => {
+		external.host = 'kit.svelte.dev'
+		return external;
+	})
+
+	let visibleInternal = $state(false);
+	const works = $derived.by(() => {
+		let internal = new SvelteURL('https://svelte.dev');
+		internal.host = 'kit.svelte.dev'
+		return internal;
+	})
+</script>
+
+<button onclick={() => (visibleExternal = true)}>external</button>
+{#if visibleExternal}
+	{throws}
+{/if}
+<button onclick={() => (visibleInternal = true)}>internal</button>
+{#if visibleInternal}
+	{works}
+{/if}
+

From 922bee9a6d44c2a0313766a9a996411acf451408 Mon Sep 17 00:00:00 2001
From: Paolo Ricciuti <ricciutipaolo@gmail.com>
Date: Wed, 25 Jun 2025 11:35:03 +0200
Subject: [PATCH 2/3] fix: use fine grained for template if the component is
 not explicitly in legacy mode (#16232)

* fix: use fine grained for template if the component is not explicitly in legacy mode

* chore: add comment

Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>

* fix: add `LabeledStatement` to `instance.ast` check

* fix: spread `keys`

* fix: snapshots

* fix: use `compileOption.runes` if defined + add other tests

---------

Co-authored-by: Simon H <5968653+dummdidumm@users.noreply.github.com>
---
 .changeset/cold-dingos-dream.md               |  5 ++++
 .../src/compiler/phases/2-analyze/index.js    | 23 +++++++++++++++++++
 .../client/visitors/shared/utils.js           |  5 +++-
 .../svelte/src/compiler/phases/types.d.ts     |  1 +
 .../svelte/tests/runtime-legacy/shared.ts     |  5 +++-
 .../_config.js                                | 17 ++++++++++++++
 .../main.svelte                               |  8 +++++++
 .../test.svelte.js                            |  9 ++++++++
 .../_config.js                                | 17 ++++++++++++++
 .../main.svelte                               |  9 ++++++++
 .../test.svelte.js                            |  9 ++++++++
 .../_config.js                                | 17 ++++++++++++++
 .../main.svelte                               |  9 ++++++++
 .../test.svelte.js                            |  9 ++++++++
 .../_config.js                                | 17 ++++++++++++++
 .../main.svelte                               |  9 ++++++++
 .../test.svelte.js                            |  9 ++++++++
 .../_config.js                                | 17 ++++++++++++++
 .../main.svelte                               |  9 ++++++++
 .../test.svelte.js                            |  9 ++++++++
 .../_config.js                                | 17 ++++++++++++++
 .../main.svelte                               | 10 ++++++++
 .../test.svelte.js                            |  9 ++++++++
 .../_config.js                                | 17 ++++++++++++++
 .../main.svelte                               | 12 ++++++++++
 .../test.svelte.js                            |  9 ++++++++
 .../samples/legacy-runes-ambiguous/_config.js | 17 ++++++++++++++
 .../legacy-runes-ambiguous/main.svelte        |  7 ++++++
 .../legacy-runes-ambiguous/test.svelte.js     |  9 ++++++++
 .../purity/_expected/client/index.svelte.js   |  6 ++---
 30 files changed, 320 insertions(+), 6 deletions(-)
 create mode 100644 .changeset/cold-dingos-dream.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/test.svelte.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/test.svelte.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/test.svelte.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/test.svelte.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/test.svelte.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/test.svelte.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/test.svelte.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/test.svelte.js

diff --git a/.changeset/cold-dingos-dream.md b/.changeset/cold-dingos-dream.md
new file mode 100644
index 0000000000..c48414abc2
--- /dev/null
+++ b/.changeset/cold-dingos-dream.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: use fine grained for template if the component is not explicitly in legacy mode
diff --git a/packages/svelte/src/compiler/phases/2-analyze/index.js b/packages/svelte/src/compiler/phases/2-analyze/index.js
index fded183b86..80adc10c1a 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/index.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/index.js
@@ -431,6 +431,29 @@ export function analyze_component(root, source, options) {
 		template,
 		elements: [],
 		runes,
+		// if we are not in runes mode but we have no reserved references ($$props, $$restProps)
+		// and no `export let` we might be in a wannabe runes component that is using runes in an external
+		// module...we need to fallback to the runic behavior
+		maybe_runes:
+			!runes &&
+			// if they explicitly disabled runes, use the legacy behavior
+			options.runes !== false &&
+			![...module.scope.references.keys()].some((name) =>
+				['$$props', '$$restProps'].includes(name)
+			) &&
+			!instance.ast.body.some(
+				(node) =>
+					node.type === 'LabeledStatement' ||
+					(node.type === 'ExportNamedDeclaration' &&
+						((node.declaration &&
+							node.declaration.type === 'VariableDeclaration' &&
+							node.declaration.kind === 'let') ||
+							node.specifiers.some(
+								(specifier) =>
+									specifier.local.type === 'Identifier' &&
+									instance.scope.get(specifier.local.name)?.declaration_kind === 'let'
+							)))
+			),
 		tracing: false,
 		classes: new Map(),
 		immutable: runes || options.immutable,
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js
index 15982899c9..c861a51b7d 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/shared/utils.js
@@ -370,7 +370,10 @@ export function validate_mutation(node, context, expression) {
 export function build_expression(context, expression, metadata, state = context.state) {
 	const value = /** @type {Expression} */ (context.visit(expression, state));
 
-	if (context.state.analysis.runes) {
+	// Components not explicitly in legacy mode might be expected to be in runes mode (especially since we didn't
+	// adjust this behavior until recently, which broke people's existing components), so we also bail in this case.
+	// Kind of an in-between-mode.
+	if (context.state.analysis.runes || context.state.analysis.maybe_runes) {
 		return value;
 	}
 
diff --git a/packages/svelte/src/compiler/phases/types.d.ts b/packages/svelte/src/compiler/phases/types.d.ts
index 67cbd75ff8..8fa4bff619 100644
--- a/packages/svelte/src/compiler/phases/types.d.ts
+++ b/packages/svelte/src/compiler/phases/types.d.ts
@@ -51,6 +51,7 @@ export interface ComponentAnalysis extends Analysis {
 	/** Used for CSS pruning and scoping */
 	elements: Array<AST.RegularElement | AST.SvelteElement>;
 	runes: boolean;
+	maybe_runes: boolean;
 	tracing: boolean;
 	exports: Array<{ name: string; alias: string | null }>;
 	/** Whether the component uses `$$props` */
diff --git a/packages/svelte/tests/runtime-legacy/shared.ts b/packages/svelte/tests/runtime-legacy/shared.ts
index 11ea9f6dda..126992a0c0 100644
--- a/packages/svelte/tests/runtime-legacy/shared.ts
+++ b/packages/svelte/tests/runtime-legacy/shared.ts
@@ -158,7 +158,10 @@ async function common_setup(cwd: string, runes: boolean | undefined, config: Run
 		...config.compileOptions,
 		immutable: config.immutable,
 		accessors: 'accessors' in config ? config.accessors : true,
-		runes
+		runes:
+			config.compileOptions && 'runes' in config.compileOptions
+				? config.compileOptions.runes
+				: runes
 	};
 
 	// load_compiled can be used for debugging a test. It means the compiler will not run on the input
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/_config.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/_config.js
new file mode 100644
index 0000000000..904fea3f65
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/_config.js
@@ -0,0 +1,17 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		runes: undefined
+	},
+	async test({ assert, target }) {
+		const p = target.querySelector('p');
+		const btn = target.querySelector('button');
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.equal(p?.innerHTML, '0');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/main.svelte b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/main.svelte
new file mode 100644
index 0000000000..cb5837dcd6
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/main.svelte
@@ -0,0 +1,8 @@
+<svelte:options runes={false} />
+<script>
+	import { get, set } from "./test.svelte.js";
+</script>
+
+<p>{get()}</p>
+
+<button onclick={()=>set()}></button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/test.svelte.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/test.svelte.js
new file mode 100644
index 0000000000..f0e7181c29
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-explicit-false/test.svelte.js
@@ -0,0 +1,9 @@
+let count = $state(0);
+
+export function get() {
+	return count;
+}
+
+export function set() {
+	count++;
+}
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/_config.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/_config.js
new file mode 100644
index 0000000000..904fea3f65
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/_config.js
@@ -0,0 +1,17 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		runes: undefined
+	},
+	async test({ assert, target }) {
+		const p = target.querySelector('p');
+		const btn = target.querySelector('button');
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.equal(p?.innerHTML, '0');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/main.svelte b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/main.svelte
new file mode 100644
index 0000000000..a7370b48d6
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/main.svelte
@@ -0,0 +1,9 @@
+<script>
+	import { get, set } from "./test.svelte.js";
+
+	$$props;
+</script>
+
+<p>{get()}</p>
+
+<button onclick={()=>set()}></button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/test.svelte.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/test.svelte.js
new file mode 100644
index 0000000000..f0e7181c29
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$props/test.svelte.js
@@ -0,0 +1,9 @@
+let count = $state(0);
+
+export function get() {
+	return count;
+}
+
+export function set() {
+	count++;
+}
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/_config.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/_config.js
new file mode 100644
index 0000000000..904fea3f65
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/_config.js
@@ -0,0 +1,17 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		runes: undefined
+	},
+	async test({ assert, target }) {
+		const p = target.querySelector('p');
+		const btn = target.querySelector('button');
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.equal(p?.innerHTML, '0');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/main.svelte b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/main.svelte
new file mode 100644
index 0000000000..ccf9bd2864
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/main.svelte
@@ -0,0 +1,9 @@
+<script>
+	import { get, set } from "./test.svelte.js";
+
+	$$restProps;
+</script>
+
+<p>{get()}</p>
+
+<button onclick={()=>set()}></button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/test.svelte.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/test.svelte.js
new file mode 100644
index 0000000000..f0e7181c29
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-$$restProps/test.svelte.js
@@ -0,0 +1,9 @@
+let count = $state(0);
+
+export function get() {
+	return count;
+}
+
+export function set() {
+	count++;
+}
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/_config.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/_config.js
new file mode 100644
index 0000000000..2d72de6d13
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/_config.js
@@ -0,0 +1,17 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		runes: undefined
+	},
+	async test({ assert, target }) {
+		const p = target.querySelector('p');
+		const btn = target.querySelector('button');
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.equal(p?.innerHTML, '1');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/main.svelte b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/main.svelte
new file mode 100644
index 0000000000..49aef81518
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/main.svelte
@@ -0,0 +1,9 @@
+<script>
+	import { get, set } from "./test.svelte.js";
+
+	export const x = 42;
+</script>
+
+<p>{get()}</p>
+
+<button onclick={()=>set()}></button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/test.svelte.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/test.svelte.js
new file mode 100644
index 0000000000..f0e7181c29
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-const/test.svelte.js
@@ -0,0 +1,9 @@
+let count = $state(0);
+
+export function get() {
+	return count;
+}
+
+export function set() {
+	count++;
+}
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/_config.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/_config.js
new file mode 100644
index 0000000000..904fea3f65
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/_config.js
@@ -0,0 +1,17 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		runes: undefined
+	},
+	async test({ assert, target }) {
+		const p = target.querySelector('p');
+		const btn = target.querySelector('button');
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.equal(p?.innerHTML, '0');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/main.svelte b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/main.svelte
new file mode 100644
index 0000000000..f7cd0ede2e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/main.svelte
@@ -0,0 +1,9 @@
+<script>
+	import { get, set } from "./test.svelte.js";
+
+	$: console.log("");
+</script>
+
+<p>{get()}</p>
+
+<button onclick={()=>set()}></button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/test.svelte.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/test.svelte.js
new file mode 100644
index 0000000000..f0e7181c29
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-labeled/test.svelte.js
@@ -0,0 +1,9 @@
+let count = $state(0);
+
+export function get() {
+	return count;
+}
+
+export function set() {
+	count++;
+}
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/_config.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/_config.js
new file mode 100644
index 0000000000..904fea3f65
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/_config.js
@@ -0,0 +1,17 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		runes: undefined
+	},
+	async test({ assert, target }) {
+		const p = target.querySelector('p');
+		const btn = target.querySelector('button');
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.equal(p?.innerHTML, '0');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/main.svelte b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/main.svelte
new file mode 100644
index 0000000000..36becde4a3
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/main.svelte
@@ -0,0 +1,10 @@
+<script>
+	import { get, set } from "./test.svelte.js";
+
+	export let x = 42;
+</script>
+
+{x}
+<p>{get()}</p>
+
+<button onclick={()=>set()}></button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/test.svelte.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/test.svelte.js
new file mode 100644
index 0000000000..f0e7181c29
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let-2/test.svelte.js
@@ -0,0 +1,9 @@
+let count = $state(0);
+
+export function get() {
+	return count;
+}
+
+export function set() {
+	count++;
+}
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/_config.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/_config.js
new file mode 100644
index 0000000000..904fea3f65
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/_config.js
@@ -0,0 +1,17 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		runes: undefined
+	},
+	async test({ assert, target }) {
+		const p = target.querySelector('p');
+		const btn = target.querySelector('button');
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.equal(p?.innerHTML, '0');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/main.svelte b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/main.svelte
new file mode 100644
index 0000000000..1449b7d582
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/main.svelte
@@ -0,0 +1,12 @@
+<script>
+	import { get, set } from "./test.svelte.js";
+
+	let x = 42;
+
+	export { x };
+</script>
+
+{x}
+<p>{get()}</p>
+
+<button onclick={()=>set()}></button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/test.svelte.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/test.svelte.js
new file mode 100644
index 0000000000..f0e7181c29
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous-export-let/test.svelte.js
@@ -0,0 +1,9 @@
+let count = $state(0);
+
+export function get() {
+	return count;
+}
+
+export function set() {
+	count++;
+}
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/_config.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/_config.js
new file mode 100644
index 0000000000..2d72de6d13
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/_config.js
@@ -0,0 +1,17 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	mode: ['client'],
+	compileOptions: {
+		runes: undefined
+	},
+	async test({ assert, target }) {
+		const p = target.querySelector('p');
+		const btn = target.querySelector('button');
+		flushSync(() => {
+			btn?.click();
+		});
+		assert.equal(p?.innerHTML, '1');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/main.svelte b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/main.svelte
new file mode 100644
index 0000000000..698a852ac9
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/main.svelte
@@ -0,0 +1,7 @@
+<script>
+	import { get, set } from "./test.svelte.js";
+</script>
+
+<p>{get()}</p>
+
+<button onclick={()=>set()}></button>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/test.svelte.js b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/test.svelte.js
new file mode 100644
index 0000000000..f0e7181c29
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/legacy-runes-ambiguous/test.svelte.js
@@ -0,0 +1,9 @@
+let count = $state(0);
+
+export function get() {
+	return count;
+}
+
+export function set() {
+	count++;
+}
diff --git a/packages/svelte/tests/snapshot/samples/purity/_expected/client/index.svelte.js b/packages/svelte/tests/snapshot/samples/purity/_expected/client/index.svelte.js
index da6fdf44d8..a351851875 100644
--- a/packages/svelte/tests/snapshot/samples/purity/_expected/client/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/purity/_expected/client/index.svelte.js
@@ -8,13 +8,11 @@ export default function Purity($$anchor) {
 	var fragment = root();
 	var p = $.first_child(fragment);
 
-	p.textContent = (
-		$.untrack(() => Math.max(0, Math.min(0, 100)))
-	);
+	p.textContent = '0';
 
 	var p_1 = $.sibling(p, 2);
 
-	p_1.textContent = ($.untrack(() => location.href));
+	p_1.textContent = location.href;
 
 	var node = $.sibling(p_1, 2);
 

From 777e67b9487ffbc8f433e50752243fcb51d22392 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Wed, 25 Jun 2025 12:38:03 +0200
Subject: [PATCH 3/3] Version Packages (#16216)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 .changeset/clever-dodos-jam.md  |  5 -----
 .changeset/cold-dingos-dream.md |  5 -----
 .changeset/fair-bats-visit.md   |  5 -----
 packages/svelte/CHANGELOG.md    | 10 ++++++++++
 packages/svelte/package.json    |  2 +-
 packages/svelte/src/version.js  |  2 +-
 6 files changed, 12 insertions(+), 17 deletions(-)
 delete mode 100644 .changeset/clever-dodos-jam.md
 delete mode 100644 .changeset/cold-dingos-dream.md
 delete mode 100644 .changeset/fair-bats-visit.md

diff --git a/.changeset/clever-dodos-jam.md b/.changeset/clever-dodos-jam.md
deleted file mode 100644
index bdeb979184..0000000000
--- a/.changeset/clever-dodos-jam.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: untrack `$inspect.with` and add check for unsafe mutation
diff --git a/.changeset/cold-dingos-dream.md b/.changeset/cold-dingos-dream.md
deleted file mode 100644
index c48414abc2..0000000000
--- a/.changeset/cold-dingos-dream.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: use fine grained for template if the component is not explicitly in legacy mode
diff --git a/.changeset/fair-bats-visit.md b/.changeset/fair-bats-visit.md
deleted file mode 100644
index bc0a426395..0000000000
--- a/.changeset/fair-bats-visit.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-lift unsafe_state_mutation constraints for SvelteSet, SvelteMap, SvelteDate, SvelteURL and SvelteURLSearchParams created inside the derived
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index b29ecc3fe3..e254be754f 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,15 @@
 # svelte
 
+## 5.34.8
+
+### Patch Changes
+
+- fix: untrack `$inspect.with` and add check for unsafe mutation ([#16209](https://github.com/sveltejs/svelte/pull/16209))
+
+- fix: use fine grained for template if the component is not explicitly in legacy mode ([#16232](https://github.com/sveltejs/svelte/pull/16232))
+
+- lift unsafe_state_mutation constraints for SvelteSet, SvelteMap, SvelteDate, SvelteURL and SvelteURLSearchParams created inside the derived ([#16221](https://github.com/sveltejs/svelte/pull/16221))
+
 ## 5.34.7
 
 ### Patch Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index bdf7576e22..17a3e980c4 100644
--- a/packages/svelte/package.json
+++ b/packages/svelte/package.json
@@ -2,7 +2,7 @@
   "name": "svelte",
   "description": "Cybernetically enhanced web apps",
   "license": "MIT",
-  "version": "5.34.7",
+  "version": "5.34.8",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index 748cc3ddd6..ec0126b17d 100644
--- a/packages/svelte/src/version.js
+++ b/packages/svelte/src/version.js
@@ -4,5 +4,5 @@
  * The current version, as set in package.json.
  * @type {string}
  */
-export const VERSION = '5.34.7';
+export const VERSION = '5.34.8';
 export const PUBLIC_VERSION = '5';