From c7ce9fc004325d5e5c957943f4c5e342e8304905 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Thu, 20 Mar 2025 14:19:42 -0400
Subject: [PATCH 01/23] fix benchmarks (#15560)

---
 benchmarking/compare/index.js  | 1 -
 benchmarking/compare/runner.js | 4 ++--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/benchmarking/compare/index.js b/benchmarking/compare/index.js
index a5fc6d10a9..9d8d279c35 100644
--- a/benchmarking/compare/index.js
+++ b/benchmarking/compare/index.js
@@ -2,7 +2,6 @@ import fs from 'node:fs';
 import path from 'node:path';
 import { execSync, fork } from 'node:child_process';
 import { fileURLToPath } from 'node:url';
-import { benchmarks } from '../benchmarks.js';
 
 // if (execSync('git status --porcelain').toString().trim()) {
 // 	console.error('Working directory is not clean');
diff --git a/benchmarking/compare/runner.js b/benchmarking/compare/runner.js
index 6fa58e2bac..a2e8646379 100644
--- a/benchmarking/compare/runner.js
+++ b/benchmarking/compare/runner.js
@@ -1,7 +1,7 @@
-import { benchmarks } from '../benchmarks.js';
+import { reactivity_benchmarks } from '../benchmarks/reactivity/index.js';
 
 const results = [];
-for (const benchmark of benchmarks) {
+for (const benchmark of reactivity_benchmarks) {
 	const result = await benchmark();
 	console.error(result.benchmark);
 	results.push(result);

From 6915c12b583f4d62c125161be07f5d09573918c9 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Thu, 20 Mar 2025 16:04:00 -0400
Subject: [PATCH 02/23] feat: allow state created in deriveds/effects to be
 written/read locally without self-invalidation (#15553)

* move parent property onto Signal

* don't self-invalidate when updating a source create inside current reaction

* lazily create deep state with parent reaction

* no need to push_derived_source with mutable_state, as it never coexists with $.derived

* reduce indirection

* remove state_unsafe_local_read error

* changeset

* tests

* fix test

* inelegant fix

* remove arg

* tweak

* some progress

* more

* tidy up

* parent -> p

* tmp

* alternative approach

* tidy up

* reduce diff size

* more

* update comment
---
 .changeset/dirty-pianos-sparkle.md            |  5 ++
 .../98-reference/.generated/client-errors.md  |  6 --
 .../svelte/messages/client-errors/errors.md   |  4 --
 .../3-transform/client/transform-client.js    |  5 +-
 .../client/visitors/VariableDeclaration.js    |  4 +-
 .../svelte/src/internal/client/constants.js   |  1 +
 packages/svelte/src/internal/client/errors.js | 15 -----
 packages/svelte/src/internal/client/index.js  |  9 ++-
 packages/svelte/src/internal/client/proxy.js  | 67 +++++++++++++++----
 .../src/internal/client/reactivity/sources.js | 57 +++++-----------
 .../svelte/src/internal/client/runtime.js     | 30 +++++----
 packages/svelte/tests/signals/test.ts         | 49 ++++++++++++--
 12 files changed, 151 insertions(+), 101 deletions(-)
 create mode 100644 .changeset/dirty-pianos-sparkle.md

diff --git a/.changeset/dirty-pianos-sparkle.md b/.changeset/dirty-pianos-sparkle.md
new file mode 100644
index 0000000000..b3e4dd1d8c
--- /dev/null
+++ b/.changeset/dirty-pianos-sparkle.md
@@ -0,0 +1,5 @@
+---
+'svelte': minor
+---
+
+feat: allow state created in deriveds/effects to be written/read locally without self-invalidation
diff --git a/documentation/docs/98-reference/.generated/client-errors.md b/documentation/docs/98-reference/.generated/client-errors.md
index 0beb3cb9a9..62d9c3302a 100644
--- a/documentation/docs/98-reference/.generated/client-errors.md
+++ b/documentation/docs/98-reference/.generated/client-errors.md
@@ -122,12 +122,6 @@ Property descriptors defined on `$state` objects must contain `value` and always
 Cannot set prototype of `$state` object
 ```
 
-### state_unsafe_local_read
-
-```
-Reading state that was created inside the same derived is forbidden. Consider using `untrack` to read locally created state
-```
-
 ### state_unsafe_mutation
 
 ```
diff --git a/packages/svelte/messages/client-errors/errors.md b/packages/svelte/messages/client-errors/errors.md
index ab4d1519c1..bc8ec36256 100644
--- a/packages/svelte/messages/client-errors/errors.md
+++ b/packages/svelte/messages/client-errors/errors.md
@@ -80,10 +80,6 @@ See the [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-long
 
 > Cannot set prototype of `$state` object
 
-## state_unsafe_local_read
-
-> Reading state that was created inside the same derived is forbidden. Consider using `untrack` to read locally created state
-
 ## state_unsafe_mutation
 
 > Updating state inside a derived or a template expression is forbidden. If the value should not be reactive, declare it without `$state`
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js b/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js
index ac8263b916..0bdfbae746 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js
@@ -219,7 +219,10 @@ export function client_component(analysis, options) {
 	for (const [name, binding] of analysis.instance.scope.declarations) {
 		if (binding.kind === 'legacy_reactive') {
 			legacy_reactive_declarations.push(
-				b.const(name, b.call('$.mutable_state', undefined, analysis.immutable ? b.true : undefined))
+				b.const(
+					name,
+					b.call('$.mutable_source', undefined, analysis.immutable ? b.true : undefined)
+				)
 			);
 		}
 		if (binding.kind === 'store_sub') {
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
index baffc5dec3..3a914fb560 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
@@ -299,7 +299,7 @@ function create_state_declarators(declarator, { scope, analysis }, value) {
 		return [
 			b.declarator(
 				declarator.id,
-				b.call('$.mutable_state', value, analysis.immutable ? b.true : undefined)
+				b.call('$.mutable_source', value, analysis.immutable ? b.true : undefined)
 			)
 		];
 	}
@@ -314,7 +314,7 @@ function create_state_declarators(declarator, { scope, analysis }, value) {
 			return b.declarator(
 				path.node,
 				binding?.kind === 'state'
-					? b.call('$.mutable_state', value, analysis.immutable ? b.true : undefined)
+					? b.call('$.mutable_source', value, analysis.immutable ? b.true : undefined)
 					: value
 			);
 		})
diff --git a/packages/svelte/src/internal/client/constants.js b/packages/svelte/src/internal/client/constants.js
index a4840ce4eb..21377c1cc8 100644
--- a/packages/svelte/src/internal/client/constants.js
+++ b/packages/svelte/src/internal/client/constants.js
@@ -20,6 +20,7 @@ export const LEGACY_DERIVED_PROP = 1 << 17;
 export const INSPECT_EFFECT = 1 << 18;
 export const HEAD_EFFECT = 1 << 19;
 export const EFFECT_HAS_DERIVED = 1 << 20;
+export const EFFECT_IS_UPDATING = 1 << 21;
 
 export const STATE_SYMBOL = Symbol('$state');
 export const STATE_SYMBOL_METADATA = Symbol('$state metadata');
diff --git a/packages/svelte/src/internal/client/errors.js b/packages/svelte/src/internal/client/errors.js
index 682816e1d6..8a5b5033a7 100644
--- a/packages/svelte/src/internal/client/errors.js
+++ b/packages/svelte/src/internal/client/errors.js
@@ -307,21 +307,6 @@ export function state_prototype_fixed() {
 	}
 }
 
-/**
- * Reading state that was created inside the same derived is forbidden. Consider using `untrack` to read locally created state
- * @returns {never}
- */
-export function state_unsafe_local_read() {
-	if (DEV) {
-		const error = new Error(`state_unsafe_local_read\nReading state that was created inside the same derived is forbidden. Consider using \`untrack\` to read locally created state\nhttps://svelte.dev/e/state_unsafe_local_read`);
-
-		error.name = 'Svelte error';
-		throw error;
-	} else {
-		throw new Error(`https://svelte.dev/e/state_unsafe_local_read`);
-	}
-}
-
 /**
  * Updating state inside a derived or a template expression is forbidden. If the value should not be reactive, declare it without `$state`
  * @returns {never}
diff --git a/packages/svelte/src/internal/client/index.js b/packages/svelte/src/internal/client/index.js
index 31da00dbb4..723ff57678 100644
--- a/packages/svelte/src/internal/client/index.js
+++ b/packages/svelte/src/internal/client/index.js
@@ -113,7 +113,14 @@ export {
 	user_effect,
 	user_pre_effect
 } from './reactivity/effects.js';
-export { mutable_state, mutate, set, state, update, update_pre } from './reactivity/sources.js';
+export {
+	mutable_source,
+	mutate,
+	set,
+	source as state,
+	update,
+	update_pre
+} from './reactivity/sources.js';
 export {
 	prop,
 	rest_props,
diff --git a/packages/svelte/src/internal/client/proxy.js b/packages/svelte/src/internal/client/proxy.js
index 29828a7c99..9c3c0cf29f 100644
--- a/packages/svelte/src/internal/client/proxy.js
+++ b/packages/svelte/src/internal/client/proxy.js
@@ -1,6 +1,6 @@
 /** @import { ProxyMetadata, Source } from '#client' */
 import { DEV } from 'esm-env';
-import { get, active_effect } from './runtime.js';
+import { get, active_effect, active_reaction, set_active_reaction } from './runtime.js';
 import { component_context } from './context.js';
 import {
 	array_prototype,
@@ -17,14 +17,16 @@ import * as e from './errors.js';
 import { get_stack } from './dev/tracing.js';
 import { tracing_mode_flag } from '../flags/index.js';
 
+/** @type {ProxyMetadata | null} */
+var parent_metadata = null;
+
 /**
  * @template T
  * @param {T} value
- * @param {ProxyMetadata | null} [parent]
  * @param {Source<T>} [prev] dev mode only
  * @returns {T}
  */
-export function proxy(value, parent = null, prev) {
+export function proxy(value, prev) {
 	// if non-proxyable, or is already a proxy, return `value`
 	if (typeof value !== 'object' || value === null || STATE_SYMBOL in value) {
 		return value;
@@ -42,6 +44,31 @@ export function proxy(value, parent = null, prev) {
 	var version = source(0);
 
 	var stack = DEV && tracing_mode_flag ? get_stack('CreatedAt') : null;
+	var reaction = active_reaction;
+
+	/**
+	 * @template T
+	 * @param {() => T} fn
+	 */
+	var with_parent = (fn) => {
+		var previous_reaction = active_reaction;
+		set_active_reaction(reaction);
+
+		/** @type {T} */
+		var result;
+
+		if (DEV) {
+			var previous_metadata = parent_metadata;
+			parent_metadata = metadata;
+			result = fn();
+			parent_metadata = previous_metadata;
+		} else {
+			result = fn();
+		}
+
+		set_active_reaction(previous_reaction);
+		return result;
+	};
 
 	if (is_proxied_array) {
 		// We need to create the length source eagerly to ensure that
@@ -54,7 +81,7 @@ export function proxy(value, parent = null, prev) {
 
 	if (DEV) {
 		metadata = {
-			parent,
+			parent: parent_metadata,
 			owners: null
 		};
 
@@ -66,7 +93,7 @@ export function proxy(value, parent = null, prev) {
 			metadata.owners = prev_owners ? new Set(prev_owners) : null;
 		} else {
 			metadata.owners =
-				parent === null
+				parent_metadata === null
 					? component_context !== null
 						? new Set([component_context.function])
 						: null
@@ -92,10 +119,13 @@ export function proxy(value, parent = null, prev) {
 			var s = sources.get(prop);
 
 			if (s === undefined) {
-				s = source(descriptor.value, stack);
+				s = with_parent(() => source(descriptor.value, stack));
 				sources.set(prop, s);
 			} else {
-				set(s, proxy(descriptor.value, metadata));
+				set(
+					s,
+					with_parent(() => proxy(descriptor.value))
+				);
 			}
 
 			return true;
@@ -106,7 +136,10 @@ export function proxy(value, parent = null, prev) {
 
 			if (s === undefined) {
 				if (prop in target) {
-					sources.set(prop, source(UNINITIALIZED, stack));
+					sources.set(
+						prop,
+						with_parent(() => source(UNINITIALIZED, stack))
+					);
 				}
 			} else {
 				// When working with arrays, we need to also ensure we update the length when removing
@@ -140,7 +173,7 @@ export function proxy(value, parent = null, prev) {
 
 			// 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 = source(proxy(exists ? target[prop] : UNINITIALIZED, metadata), stack);
+				s = with_parent(() => source(proxy(exists ? target[prop] : UNINITIALIZED), stack));
 				sources.set(prop, s);
 			}
 
@@ -208,7 +241,7 @@ export function proxy(value, parent = null, prev) {
 				(active_effect !== null && (!has || get_descriptor(target, prop)?.writable))
 			) {
 				if (s === undefined) {
-					s = source(has ? proxy(target[prop], metadata) : UNINITIALIZED, stack);
+					s = with_parent(() => source(has ? proxy(target[prop]) : UNINITIALIZED, stack));
 					sources.set(prop, s);
 				}
 
@@ -235,7 +268,7 @@ export function proxy(value, parent = null, prev) {
 						// If the item exists in the original, we need to create a uninitialized source,
 						// else a later read of the property would result in a source being created with
 						// the value of the original item at that index.
-						other_s = source(UNINITIALIZED, stack);
+						other_s = with_parent(() => source(UNINITIALIZED, stack));
 						sources.set(i + '', other_s);
 					}
 				}
@@ -247,13 +280,19 @@ export function proxy(value, parent = null, prev) {
 			// object property before writing to that property.
 			if (s === undefined) {
 				if (!has || get_descriptor(target, prop)?.writable) {
-					s = source(undefined, stack);
-					set(s, proxy(value, metadata));
+					s = with_parent(() => source(undefined, stack));
+					set(
+						s,
+						with_parent(() => proxy(value))
+					);
 					sources.set(prop, s);
 				}
 			} else {
 				has = s.v !== UNINITIALIZED;
-				set(s, proxy(value, metadata));
+				set(
+					s,
+					with_parent(() => proxy(value))
+				);
 			}
 
 			if (DEV) {
diff --git a/packages/svelte/src/internal/client/reactivity/sources.js b/packages/svelte/src/internal/client/reactivity/sources.js
index 92508945c9..cac8431b4e 100644
--- a/packages/svelte/src/internal/client/reactivity/sources.js
+++ b/packages/svelte/src/internal/client/reactivity/sources.js
@@ -11,8 +11,8 @@ import {
 	untrack,
 	increment_write_version,
 	update_effect,
-	derived_sources,
-	set_derived_sources,
+	reaction_sources,
+	set_reaction_sources,
 	check_dirtiness,
 	untracking,
 	is_destroying_effect
@@ -27,7 +27,8 @@ import {
 	UNOWNED,
 	MAYBE_DIRTY,
 	BLOCK_EFFECT,
-	ROOT_EFFECT
+	ROOT_EFFECT,
+	EFFECT_IS_UPDATING
 } from '../constants.js';
 import * as e from '../errors.js';
 import { legacy_mode_flag, tracing_mode_flag } from '../../flags/index.js';
@@ -51,6 +52,7 @@ export function set_inspect_effects(v) {
  * @param {Error | null} [stack]
  * @returns {Source<V>}
  */
+// TODO rename this to `state` throughout the codebase
 export function source(v, stack) {
 	/** @type {Value} */
 	var signal = {
@@ -62,6 +64,14 @@ export function source(v, stack) {
 		wv: 0
 	};
 
+	if (active_reaction !== null && active_reaction.f & EFFECT_IS_UPDATING) {
+		if (reaction_sources === null) {
+			set_reaction_sources([signal]);
+		} else {
+			reaction_sources.push(signal);
+		}
+	}
+
 	if (DEV && tracing_mode_flag) {
 		signal.created = stack ?? get_stack('CreatedAt');
 		signal.debug = null;
@@ -70,14 +80,6 @@ export function source(v, stack) {
 	return signal;
 }
 
-/**
- * @template V
- * @param {V} v
- */
-export function state(v) {
-	return push_derived_source(source(v));
-}
-
 /**
  * @template V
  * @param {V} initial_value
@@ -100,33 +102,6 @@ export function mutable_source(initial_value, immutable = false) {
 	return s;
 }
 
-/**
- * @template V
- * @param {V} v
- * @param {boolean} [immutable]
- * @returns {Source<V>}
- */
-export function mutable_state(v, immutable = false) {
-	return push_derived_source(mutable_source(v, immutable));
-}
-
-/**
- * @template V
- * @param {Source<V>} source
- */
-/*#__NO_SIDE_EFFECTS__*/
-function push_derived_source(source) {
-	if (active_reaction !== null && !untracking && (active_reaction.f & DERIVED) !== 0) {
-		if (derived_sources === null) {
-			set_derived_sources([source]);
-		} else {
-			derived_sources.push(source);
-		}
-	}
-
-	return source;
-}
-
 /**
  * @template V
  * @param {Value<V>} source
@@ -153,14 +128,12 @@ export function set(source, value, should_proxy = false) {
 		!untracking &&
 		is_runes() &&
 		(active_reaction.f & (DERIVED | BLOCK_EFFECT)) !== 0 &&
-		// If the source was created locally within the current derived, then
-		// we allow the mutation.
-		(derived_sources === null || !derived_sources.includes(source))
+		!reaction_sources?.includes(source)
 	) {
 		e.state_unsafe_mutation();
 	}
 
-	let new_value = should_proxy ? proxy(value, null, source) : value;
+	let new_value = should_proxy ? proxy(value, source) : value;
 
 	return internal_set(source, new_value);
 }
diff --git a/packages/svelte/src/internal/client/runtime.js b/packages/svelte/src/internal/client/runtime.js
index 0a65c6e45a..74b58ee1a9 100644
--- a/packages/svelte/src/internal/client/runtime.js
+++ b/packages/svelte/src/internal/client/runtime.js
@@ -22,7 +22,8 @@ import {
 	ROOT_EFFECT,
 	LEGACY_DERIVED_PROP,
 	DISCONNECTED,
-	BOUNDARY_EFFECT
+	BOUNDARY_EFFECT,
+	EFFECT_IS_UPDATING
 } from './constants.js';
 import { flush_tasks } from './dom/task.js';
 import { internal_set, old_values } from './reactivity/sources.js';
@@ -87,17 +88,17 @@ export function set_active_effect(effect) {
 }
 
 /**
- * When sources are created within a derived, we record them so that we can safely allow
- * local mutations to these sources without the side-effect error being invoked unnecessarily.
+ * When sources are created within a reaction, reading and writing
+ * them should not cause a re-run
  * @type {null | Source[]}
  */
-export let derived_sources = null;
+export let reaction_sources = null;
 
 /**
  * @param {Source[] | null} sources
  */
-export function set_derived_sources(sources) {
-	derived_sources = sources;
+export function set_reaction_sources(sources) {
+	reaction_sources = sources;
 }
 
 /**
@@ -367,6 +368,9 @@ function schedule_possible_effect_self_invalidation(signal, effect, root = true)
 
 	for (var i = 0; i < reactions.length; i++) {
 		var reaction = reactions[i];
+
+		if (reaction_sources?.includes(signal)) continue;
+
 		if ((reaction.f & DERIVED) !== 0) {
 			schedule_possible_effect_self_invalidation(/** @type {Derived} */ (reaction), effect, false);
 		} else if (effect === reaction) {
@@ -391,9 +395,10 @@ export function update_reaction(reaction) {
 	var previous_untracked_writes = untracked_writes;
 	var previous_reaction = active_reaction;
 	var previous_skip_reaction = skip_reaction;
-	var prev_derived_sources = derived_sources;
+	var previous_reaction_sources = reaction_sources;
 	var previous_component_context = component_context;
 	var previous_untracking = untracking;
+
 	var flags = reaction.f;
 
 	new_deps = /** @type {null | Value[]} */ (null);
@@ -403,11 +408,13 @@ export function update_reaction(reaction) {
 		(flags & UNOWNED) !== 0 && (untracking || !is_updating_effect || active_reaction === null);
 	active_reaction = (flags & (BRANCH_EFFECT | ROOT_EFFECT)) === 0 ? reaction : null;
 
-	derived_sources = null;
+	reaction_sources = null;
 	set_component_context(reaction.ctx);
 	untracking = false;
 	read_version++;
 
+	reaction.f |= EFFECT_IS_UPDATING;
+
 	try {
 		var result = /** @type {Function} */ (0, reaction.fn)();
 		var deps = reaction.deps;
@@ -477,9 +484,11 @@ export function update_reaction(reaction) {
 		untracked_writes = previous_untracked_writes;
 		active_reaction = previous_reaction;
 		skip_reaction = previous_skip_reaction;
-		derived_sources = prev_derived_sources;
+		reaction_sources = previous_reaction_sources;
 		set_component_context(previous_component_context);
 		untracking = previous_untracking;
+
+		reaction.f ^= EFFECT_IS_UPDATING;
 	}
 }
 
@@ -866,9 +875,6 @@ export function get(signal) {
 
 	// Register the dependency on the current reaction signal.
 	if (active_reaction !== null && !untracking) {
-		if (derived_sources !== null && derived_sources.includes(signal)) {
-			e.state_unsafe_local_read();
-		}
 		var deps = active_reaction.deps;
 		if (signal.rv < read_version) {
 			signal.rv = read_version;
diff --git a/packages/svelte/tests/signals/test.ts b/packages/svelte/tests/signals/test.ts
index ef4cf16d3b..72f99c90e5 100644
--- a/packages/svelte/tests/signals/test.ts
+++ b/packages/svelte/tests/signals/test.ts
@@ -8,7 +8,12 @@ import {
 	render_effect,
 	user_effect
 } from '../../src/internal/client/reactivity/effects';
-import { state, set, update, update_pre } from '../../src/internal/client/reactivity/sources';
+import {
+	source as state,
+	set,
+	update,
+	update_pre
+} from '../../src/internal/client/reactivity/sources';
 import type { Derived, Effect, Value } from '../../src/internal/client/types';
 import { proxy } from '../../src/internal/client/proxy';
 import { derived } from '../../src/internal/client/reactivity/deriveds';
@@ -487,6 +492,26 @@ describe('signals', () => {
 		};
 	});
 
+	test('schedules rerun when updating deeply nested value', (runes) => {
+		if (!runes) return () => {};
+
+		const value = proxy({ a: { b: { c: 0 } } });
+		user_effect(() => {
+			value.a.b.c += 1;
+		});
+
+		return () => {
+			let errored = false;
+			try {
+				flushSync();
+			} catch (e: any) {
+				assert.include(e.message, 'effect_update_depth_exceeded');
+				errored = true;
+			}
+			assert.equal(errored, true);
+		};
+	});
+
 	test('schedules rerun when writing to signal before reading it', (runes) => {
 		if (!runes) return () => {};
 
@@ -958,14 +983,30 @@ describe('signals', () => {
 		};
 	});
 
-	test('deriveds cannot depend on state they own', () => {
+	test('deriveds do not depend on state they own', () => {
 		return () => {
+			let s;
+
 			const d = derived(() => {
-				const s = state(0);
+				s = state(0);
 				return $.get(s);
 			});
 
-			assert.throws(() => $.get(d), 'state_unsafe_local_read');
+			assert.equal($.get(d), 0);
+
+			set(s!, 1);
+			assert.equal($.get(d), 0);
+		};
+	});
+
+	test('effects do not depend on state they own', () => {
+		user_effect(() => {
+			const value = state(0);
+			set(value, $.get(value) + 1);
+		});
+
+		return () => {
+			flushSync();
 		};
 	});
 

From 1a5fb8fd51cdec1a72df9ec3100317bea83698aa Mon Sep 17 00:00:00 2001
From: Robert Gieseke <rob.g@web.de>
Date: Fri, 21 Mar 2025 14:28:44 +0100
Subject: [PATCH 03/23] fix: Keep inlined JSDoc comments in property conversion
 of svelte-migrate (#15567)

* Add failing JSDoc property svelte-migrate conversion tests

* Add further test case and remove default value in JSDoc output

* Look for inlined JSDoc comments after a hyphen

* Add changeset
---
 .changeset/happy-cameras-bow.md                    |  5 +++++
 packages/svelte/src/compiler/migrate/index.js      |  7 +++++--
 .../samples/jsdoc-with-comments/input.svelte       |  9 +++++++++
 .../samples/jsdoc-with-comments/output.svelte      | 14 +++++++++++++-
 4 files changed, 32 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/happy-cameras-bow.md

diff --git a/.changeset/happy-cameras-bow.md b/.changeset/happy-cameras-bow.md
new file mode 100644
index 0000000000..47188f4f6d
--- /dev/null
+++ b/.changeset/happy-cameras-bow.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+Keep inlined trailing JSDoc comments of properties when running svelte-migrate
diff --git a/packages/svelte/src/compiler/migrate/index.js b/packages/svelte/src/compiler/migrate/index.js
index 1bb7a69a20..02bb5b1443 100644
--- a/packages/svelte/src/compiler/migrate/index.js
+++ b/packages/svelte/src/compiler/migrate/index.js
@@ -1592,7 +1592,6 @@ function extract_type_and_comment(declarator, state, path) {
 	const comment_start = /** @type {any} */ (comment_node)?.start;
 	const comment_end = /** @type {any} */ (comment_node)?.end;
 	let comment = comment_node && str.original.substring(comment_start, comment_end);
-
 	if (comment_node) {
 		str.update(comment_start, comment_end, '');
 	}
@@ -1673,6 +1672,11 @@ function extract_type_and_comment(declarator, state, path) {
 		state.has_type_or_fallback = true;
 		const match = /@type {(.+)}/.exec(comment_node.value);
 		if (match) {
+			// try to find JSDoc comments after a hyphen `-`
+			const jsdocComment = /@type {.+} (?:\w+|\[.*?\]) - (.+)/.exec(comment_node.value);
+			if (jsdocComment) {
+				cleaned_comment += jsdocComment[1]?.trim();
+			}
 			return {
 				type: match[1],
 				comment: cleaned_comment,
@@ -1693,7 +1697,6 @@ function extract_type_and_comment(declarator, state, path) {
 			};
 		}
 	}
-
 	return {
 		type: 'any',
 		comment: state.uses_ts ? comment : cleaned_comment,
diff --git a/packages/svelte/tests/migrate/samples/jsdoc-with-comments/input.svelte b/packages/svelte/tests/migrate/samples/jsdoc-with-comments/input.svelte
index f2efb1db80..f138c3a070 100644
--- a/packages/svelte/tests/migrate/samples/jsdoc-with-comments/input.svelte
+++ b/packages/svelte/tests/migrate/samples/jsdoc-with-comments/input.svelte
@@ -21,6 +21,9 @@
 	 */
 	export let type_no_comment;
 
+	/** @type {boolean} type_with_comment - One-line declaration with comment */
+	export let type_with_comment;
+
 	/**
 	 * This is optional
 	 */
@@ -40,4 +43,10 @@
 	export let inline_multiline_trailing_comment = 'world'; /*
 	* this is a same-line trailing multiline comment
 	**/
+
+	/** @type {number} [default_value=1] */
+	export let default_value = 1;
+
+	/** @type {number} [comment_default_value=1] - This has a comment and an optional value. */
+	export let comment_default_value = 1;
 </script>
\ No newline at end of file
diff --git a/packages/svelte/tests/migrate/samples/jsdoc-with-comments/output.svelte b/packages/svelte/tests/migrate/samples/jsdoc-with-comments/output.svelte
index 19fbe38b50..32133ccd4c 100644
--- a/packages/svelte/tests/migrate/samples/jsdoc-with-comments/output.svelte
+++ b/packages/svelte/tests/migrate/samples/jsdoc-with-comments/output.svelte
@@ -9,12 +9,18 @@
 	
 
 	
+
+	
+	
+
 	
 
 	
 
+
 	
 
+	
 	/**
 	 * @typedef {Object} Props
 	 * @property {string} comment - My wonderful comment
@@ -22,11 +28,14 @@
 	 * @property {any} one_line - one line comment
 	 * @property {any} no_comment
 	 * @property {boolean} type_no_comment
+	 * @property {boolean} type_with_comment - One-line declaration with comment
 	 * @property {any} [optional] - This is optional
 	 * @property {any} inline_commented - this should stay a comment
 	 * @property {any} inline_commented_merged - This comment should be merged - with this inline comment
 	 * @property {string} [inline_multiline_leading_comment] - this is a same-line leading multiline comment
 	 * @property {string} [inline_multiline_trailing_comment] - this is a same-line trailing multiline comment
+	 * @property {number} [default_value]
+	 * @property {number} [comment_default_value] - This has a comment and an optional value.
 	 */
 
 	/** @type {Props} */
@@ -36,10 +45,13 @@
 		one_line,
 		no_comment,
 		type_no_comment,
+		type_with_comment,
 		optional = {stuff: true},
 		inline_commented,
 		inline_commented_merged,
 		inline_multiline_leading_comment = 'world',
-		inline_multiline_trailing_comment = 'world'
+		inline_multiline_trailing_comment = 'world',
+		default_value = 1,
+		comment_default_value = 1
 	} = $props();
 </script>
\ No newline at end of file

From 1d10a65b7858ca4da8d7ade113ec5b6f9c1afb43 Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <trueadm@users.noreply.github.com>
Date: Fri, 21 Mar 2025 13:30:17 +0000
Subject: [PATCH 04/23] fix: check if DOM prototypes are extensible (#15569)

---
 .changeset/dry-ducks-roll.md                  |  5 +++
 .../src/internal/client/dom/operations.js     | 35 +++++++++++--------
 packages/svelte/src/internal/shared/utils.js  |  1 +
 3 files changed, 26 insertions(+), 15 deletions(-)
 create mode 100644 .changeset/dry-ducks-roll.md

diff --git a/.changeset/dry-ducks-roll.md b/.changeset/dry-ducks-roll.md
new file mode 100644
index 0000000000..2dea8174dd
--- /dev/null
+++ b/.changeset/dry-ducks-roll.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: check if DOM prototypes are extensible
diff --git a/packages/svelte/src/internal/client/dom/operations.js b/packages/svelte/src/internal/client/dom/operations.js
index 0ad9045b20..aae44d4b39 100644
--- a/packages/svelte/src/internal/client/dom/operations.js
+++ b/packages/svelte/src/internal/client/dom/operations.js
@@ -2,7 +2,7 @@
 import { hydrate_node, hydrating, set_hydrate_node } from './hydration.js';
 import { DEV } from 'esm-env';
 import { init_array_prototype_warnings } from '../dev/equality.js';
-import { get_descriptor } from '../../shared/utils.js';
+import { get_descriptor, is_extensible } from '../../shared/utils.js';
 
 // export these for reference in the compiled code, making global name deduplication unnecessary
 /** @type {Window} */
@@ -34,26 +34,31 @@ export function init_operations() {
 
 	var element_prototype = Element.prototype;
 	var node_prototype = Node.prototype;
+	var text_prototype = Text.prototype;
 
 	// @ts-ignore
 	first_child_getter = get_descriptor(node_prototype, 'firstChild').get;
 	// @ts-ignore
 	next_sibling_getter = get_descriptor(node_prototype, 'nextSibling').get;
 
-	// the following assignments improve perf of lookups on DOM nodes
-	// @ts-expect-error
-	element_prototype.__click = undefined;
-	// @ts-expect-error
-	element_prototype.__className = undefined;
-	// @ts-expect-error
-	element_prototype.__attributes = null;
-	// @ts-expect-error
-	element_prototype.__style = undefined;
-	// @ts-expect-error
-	element_prototype.__e = undefined;
-
-	// @ts-expect-error
-	Text.prototype.__t = undefined;
+	if (is_extensible(element_prototype)) {
+		// the following assignments improve perf of lookups on DOM nodes
+		// @ts-expect-error
+		element_prototype.__click = undefined;
+		// @ts-expect-error
+		element_prototype.__className = undefined;
+		// @ts-expect-error
+		element_prototype.__attributes = null;
+		// @ts-expect-error
+		element_prototype.__style = undefined;
+		// @ts-expect-error
+		element_prototype.__e = undefined;
+	}
+
+	if (is_extensible(text_prototype)) {
+		// @ts-expect-error
+		text_prototype.__t = undefined;
+	}
 
 	if (DEV) {
 		// @ts-expect-error
diff --git a/packages/svelte/src/internal/shared/utils.js b/packages/svelte/src/internal/shared/utils.js
index f9d52cb065..5e7f3152d8 100644
--- a/packages/svelte/src/internal/shared/utils.js
+++ b/packages/svelte/src/internal/shared/utils.js
@@ -10,6 +10,7 @@ export var get_descriptors = Object.getOwnPropertyDescriptors;
 export var object_prototype = Object.prototype;
 export var array_prototype = Array.prototype;
 export var get_prototype_of = Object.getPrototypeOf;
+export var is_extensible = Object.isExtensible;
 
 /**
  * @param {any} thing

From d2e79326c7d3810cd4ec657660d4aeec464cd689 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 21 Mar 2025 09:31:03 -0400
Subject: [PATCH 05/23] fix: don't depend on deriveds created inside the
 current reaction (#15564)

* WIP

* WIP

* add test

* update test

* changeset

* oops

* lint
---
 .changeset/young-poets-wait.md                |  5 +++
 packages/svelte/src/internal/client/index.js  | 11 +----
 packages/svelte/src/internal/client/proxy.js  |  2 +-
 .../internal/client/reactivity/deriveds.js    | 16 ++++++-
 .../src/internal/client/reactivity/sources.js | 24 +++++++----
 .../svelte/src/internal/client/runtime.js     | 43 ++++++++++++-------
 .../samples/effect-cleanup/_config.js         |  2 +-
 .../samples/untrack-own-deriveds/_config.js   | 20 +++++++++
 .../samples/untrack-own-deriveds/main.svelte  | 26 +++++++++++
 packages/svelte/tests/signals/test.ts         |  7 +--
 10 files changed, 114 insertions(+), 42 deletions(-)
 create mode 100644 .changeset/young-poets-wait.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/main.svelte

diff --git a/.changeset/young-poets-wait.md b/.changeset/young-poets-wait.md
new file mode 100644
index 0000000000..479f5027ef
--- /dev/null
+++ b/.changeset/young-poets-wait.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: don't depend on deriveds created inside the current reaction
diff --git a/packages/svelte/src/internal/client/index.js b/packages/svelte/src/internal/client/index.js
index 723ff57678..a5f93e8b17 100644
--- a/packages/svelte/src/internal/client/index.js
+++ b/packages/svelte/src/internal/client/index.js
@@ -101,7 +101,7 @@ export {
 	text,
 	props_id
 } from './dom/template.js';
-export { derived, derived_safe_equal } from './reactivity/deriveds.js';
+export { user_derived as derived, derived_safe_equal } from './reactivity/deriveds.js';
 export {
 	effect_tracking,
 	effect_root,
@@ -113,14 +113,7 @@ export {
 	user_effect,
 	user_pre_effect
 } from './reactivity/effects.js';
-export {
-	mutable_source,
-	mutate,
-	set,
-	source as state,
-	update,
-	update_pre
-} from './reactivity/sources.js';
+export { mutable_source, mutate, set, state, update, update_pre } from './reactivity/sources.js';
 export {
 	prop,
 	rest_props,
diff --git a/packages/svelte/src/internal/client/proxy.js b/packages/svelte/src/internal/client/proxy.js
index 9c3c0cf29f..ffe63f4b77 100644
--- a/packages/svelte/src/internal/client/proxy.js
+++ b/packages/svelte/src/internal/client/proxy.js
@@ -10,7 +10,7 @@ import {
 	object_prototype
 } from '../shared/utils.js';
 import { check_ownership, widen_ownership } from './dev/ownership.js';
-import { source, set } from './reactivity/sources.js';
+import { state as source, set } from './reactivity/sources.js';
 import { STATE_SYMBOL, STATE_SYMBOL_METADATA } from './constants.js';
 import { UNINITIALIZED } from '../../constants.js';
 import * as e from './errors.js';
diff --git a/packages/svelte/src/internal/client/reactivity/deriveds.js b/packages/svelte/src/internal/client/reactivity/deriveds.js
index 795417cc0f..cd7bbba02f 100644
--- a/packages/svelte/src/internal/client/reactivity/deriveds.js
+++ b/packages/svelte/src/internal/client/reactivity/deriveds.js
@@ -8,7 +8,8 @@ import {
 	skip_reaction,
 	update_reaction,
 	increment_write_version,
-	set_active_effect
+	set_active_effect,
+	push_reaction_value
 } from '../runtime.js';
 import { equals, safe_equals } from './equality.js';
 import * as e from '../errors.js';
@@ -61,6 +62,19 @@ export function derived(fn) {
 	return signal;
 }
 
+/**
+ * @template V
+ * @param {() => V} fn
+ * @returns {Derived<V>}
+ */
+export function user_derived(fn) {
+	const d = derived(fn);
+
+	push_reaction_value(d);
+
+	return d;
+}
+
 /**
  * @template V
  * @param {() => V} fn
diff --git a/packages/svelte/src/internal/client/reactivity/sources.js b/packages/svelte/src/internal/client/reactivity/sources.js
index cac8431b4e..e4834902fe 100644
--- a/packages/svelte/src/internal/client/reactivity/sources.js
+++ b/packages/svelte/src/internal/client/reactivity/sources.js
@@ -15,7 +15,8 @@ import {
 	set_reaction_sources,
 	check_dirtiness,
 	untracking,
-	is_destroying_effect
+	is_destroying_effect,
+	push_reaction_value
 } from '../runtime.js';
 import { equals, safe_equals } from './equality.js';
 import {
@@ -64,14 +65,6 @@ export function source(v, stack) {
 		wv: 0
 	};
 
-	if (active_reaction !== null && active_reaction.f & EFFECT_IS_UPDATING) {
-		if (reaction_sources === null) {
-			set_reaction_sources([signal]);
-		} else {
-			reaction_sources.push(signal);
-		}
-	}
-
 	if (DEV && tracing_mode_flag) {
 		signal.created = stack ?? get_stack('CreatedAt');
 		signal.debug = null;
@@ -80,6 +73,19 @@ export function source(v, stack) {
 	return signal;
 }
 
+/**
+ * @template V
+ * @param {V} v
+ * @param {Error | null} [stack]
+ */
+export function state(v, stack) {
+	const s = source(v, stack);
+
+	push_reaction_value(s);
+
+	return s;
+}
+
 /**
  * @template V
  * @param {V} initial_value
diff --git a/packages/svelte/src/internal/client/runtime.js b/packages/svelte/src/internal/client/runtime.js
index 74b58ee1a9..a5d26412a4 100644
--- a/packages/svelte/src/internal/client/runtime.js
+++ b/packages/svelte/src/internal/client/runtime.js
@@ -101,6 +101,17 @@ export function set_reaction_sources(sources) {
 	reaction_sources = sources;
 }
 
+/** @param {Value} value */
+export function push_reaction_value(value) {
+	if (active_reaction !== null && active_reaction.f & EFFECT_IS_UPDATING) {
+		if (reaction_sources === null) {
+			set_reaction_sources([value]);
+		} else {
+			reaction_sources.push(value);
+		}
+	}
+}
+
 /**
  * The dependencies of the reaction that is currently being executed. In many cases,
  * the dependencies are unchanged between runs, and so this will be `null` unless
@@ -875,21 +886,23 @@ export function get(signal) {
 
 	// Register the dependency on the current reaction signal.
 	if (active_reaction !== null && !untracking) {
-		var deps = active_reaction.deps;
-		if (signal.rv < read_version) {
-			signal.rv = read_version;
-			// If the signal is accessing the same dependencies in the same
-			// order as it did last time, increment `skipped_deps`
-			// rather than updating `new_deps`, which creates GC cost
-			if (new_deps === null && deps !== null && deps[skipped_deps] === signal) {
-				skipped_deps++;
-			} else if (new_deps === null) {
-				new_deps = [signal];
-			} else if (!skip_reaction || !new_deps.includes(signal)) {
-				// Normally we can push duplicated dependencies to `new_deps`, but if we're inside
-				// an unowned derived because skip_reaction is true, then we need to ensure that
-				// we don't have duplicates
-				new_deps.push(signal);
+		if (!reaction_sources?.includes(signal)) {
+			var deps = active_reaction.deps;
+			if (signal.rv < read_version) {
+				signal.rv = read_version;
+				// If the signal is accessing the same dependencies in the same
+				// order as it did last time, increment `skipped_deps`
+				// rather than updating `new_deps`, which creates GC cost
+				if (new_deps === null && deps !== null && deps[skipped_deps] === signal) {
+					skipped_deps++;
+				} else if (new_deps === null) {
+					new_deps = [signal];
+				} else if (!skip_reaction || !new_deps.includes(signal)) {
+					// Normally we can push duplicated dependencies to `new_deps`, but if we're inside
+					// an unowned derived because skip_reaction is true, then we need to ensure that
+					// we don't have duplicates
+					new_deps.push(signal);
+				}
 			}
 		}
 	} else if (
diff --git a/packages/svelte/tests/runtime-runes/samples/effect-cleanup/_config.js b/packages/svelte/tests/runtime-runes/samples/effect-cleanup/_config.js
index 6a3d9eef77..e55733c148 100644
--- a/packages/svelte/tests/runtime-runes/samples/effect-cleanup/_config.js
+++ b/packages/svelte/tests/runtime-runes/samples/effect-cleanup/_config.js
@@ -10,6 +10,6 @@ export default test({
 		flushSync(() => {
 			b1.click();
 		});
-		assert.deepEqual(logs, ['init 0', 'cleanup 2', null, 'init 2', 'cleanup 4', null, 'init 4']);
+		assert.deepEqual(logs, ['init 0']);
 	}
 });
diff --git a/packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/_config.js b/packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/_config.js
new file mode 100644
index 0000000000..18062b86fb
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/_config.js
@@ -0,0 +1,20 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	test({ assert, target, logs }) {
+		const button = target.querySelector('button');
+
+		flushSync(() => button?.click());
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>increment</button>
+				<p>1/2</p
+			`
+		);
+
+		assert.deepEqual(logs, [0, 0]);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/main.svelte b/packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/main.svelte
new file mode 100644
index 0000000000..bbad2cdf4a
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/untrack-own-deriveds/main.svelte
@@ -0,0 +1,26 @@
+<script>
+	class Foo {
+		value = $state(0);
+		double = $derived(this.value * 2);
+
+		constructor() {
+			console.log(this.value, this.double);
+		}
+
+		increment() {
+			this.value++;
+		}
+	}
+
+	let foo = $state();
+
+	$effect(() => {
+		foo = new Foo();
+	});
+</script>
+
+<button onclick={() => foo.increment()}>increment</button>
+
+{#if foo}
+	<p>{foo.value}/{foo.double}</p>
+{/if}
diff --git a/packages/svelte/tests/signals/test.ts b/packages/svelte/tests/signals/test.ts
index 72f99c90e5..3977caae36 100644
--- a/packages/svelte/tests/signals/test.ts
+++ b/packages/svelte/tests/signals/test.ts
@@ -8,12 +8,7 @@ import {
 	render_effect,
 	user_effect
 } from '../../src/internal/client/reactivity/effects';
-import {
-	source as state,
-	set,
-	update,
-	update_pre
-} from '../../src/internal/client/reactivity/sources';
+import { state, set, update, update_pre } from '../../src/internal/client/reactivity/sources';
 import type { Derived, Effect, Value } from '../../src/internal/client/types';
 import { proxy } from '../../src/internal/client/proxy';
 import { derived } from '../../src/internal/client/reactivity/deriveds';

From e25c2812961f9bb74ab50f1b034d8e5a5d8ae412 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Fri, 21 Mar 2025 09:40:37 -0400
Subject: [PATCH 06/23] Version Packages (#15551)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 .changeset/dirty-pianos-sparkle.md |  5 -----
 .changeset/dry-ducks-roll.md       |  5 -----
 .changeset/happy-cameras-bow.md    |  5 -----
 .changeset/nine-laws-rush.md       |  5 -----
 .changeset/young-poets-wait.md     |  5 -----
 packages/svelte/CHANGELOG.md       | 16 ++++++++++++++++
 packages/svelte/package.json       |  2 +-
 packages/svelte/src/version.js     |  2 +-
 8 files changed, 18 insertions(+), 27 deletions(-)
 delete mode 100644 .changeset/dirty-pianos-sparkle.md
 delete mode 100644 .changeset/dry-ducks-roll.md
 delete mode 100644 .changeset/happy-cameras-bow.md
 delete mode 100644 .changeset/nine-laws-rush.md
 delete mode 100644 .changeset/young-poets-wait.md

diff --git a/.changeset/dirty-pianos-sparkle.md b/.changeset/dirty-pianos-sparkle.md
deleted file mode 100644
index b3e4dd1d8c..0000000000
--- a/.changeset/dirty-pianos-sparkle.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': minor
----
-
-feat: allow state created in deriveds/effects to be written/read locally without self-invalidation
diff --git a/.changeset/dry-ducks-roll.md b/.changeset/dry-ducks-roll.md
deleted file mode 100644
index 2dea8174dd..0000000000
--- a/.changeset/dry-ducks-roll.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: check if DOM prototypes are extensible
diff --git a/.changeset/happy-cameras-bow.md b/.changeset/happy-cameras-bow.md
deleted file mode 100644
index 47188f4f6d..0000000000
--- a/.changeset/happy-cameras-bow.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-Keep inlined trailing JSDoc comments of properties when running svelte-migrate
diff --git a/.changeset/nine-laws-rush.md b/.changeset/nine-laws-rush.md
deleted file mode 100644
index e0a0fc15a0..0000000000
--- a/.changeset/nine-laws-rush.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: simplify set calls for proxyable values
diff --git a/.changeset/young-poets-wait.md b/.changeset/young-poets-wait.md
deleted file mode 100644
index 479f5027ef..0000000000
--- a/.changeset/young-poets-wait.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: don't depend on deriveds created inside the current reaction
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index 6461df1d25..8cb7efd4ef 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,21 @@
 # svelte
 
+## 5.24.0
+
+### Minor Changes
+
+- feat: allow state created in deriveds/effects to be written/read locally without self-invalidation ([#15553](https://github.com/sveltejs/svelte/pull/15553))
+
+### Patch Changes
+
+- fix: check if DOM prototypes are extensible ([#15569](https://github.com/sveltejs/svelte/pull/15569))
+
+- Keep inlined trailing JSDoc comments of properties when running svelte-migrate ([#15567](https://github.com/sveltejs/svelte/pull/15567))
+
+- fix: simplify set calls for proxyable values ([#15548](https://github.com/sveltejs/svelte/pull/15548))
+
+- fix: don't depend on deriveds created inside the current reaction ([#15564](https://github.com/sveltejs/svelte/pull/15564))
+
 ## 5.23.2
 
 ### Patch Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index d005eca0b9..0aa6b29841 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": "5.23.2",
+  "version": "5.24.0",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index 191b52ecef..7cd43e74cb 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 = '5.23.2';
+export const VERSION = '5.24.0';
 export const PUBLIC_VERSION = '5';

From 6b23a7c4777a123dc1ea4db6cb87e03268fbb45b Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 21 Mar 2025 09:52:30 -0400
Subject: [PATCH 07/23] chore: camelCase -> snake_case (#15573)

---
 packages/svelte/src/compiler/migrate/index.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/packages/svelte/src/compiler/migrate/index.js b/packages/svelte/src/compiler/migrate/index.js
index 02bb5b1443..7f26d0d010 100644
--- a/packages/svelte/src/compiler/migrate/index.js
+++ b/packages/svelte/src/compiler/migrate/index.js
@@ -1673,9 +1673,9 @@ function extract_type_and_comment(declarator, state, path) {
 		const match = /@type {(.+)}/.exec(comment_node.value);
 		if (match) {
 			// try to find JSDoc comments after a hyphen `-`
-			const jsdocComment = /@type {.+} (?:\w+|\[.*?\]) - (.+)/.exec(comment_node.value);
-			if (jsdocComment) {
-				cleaned_comment += jsdocComment[1]?.trim();
+			const jsdoc_comment = /@type {.+} (?:\w+|\[.*?\]) - (.+)/.exec(comment_node.value);
+			if (jsdoc_comment) {
+				cleaned_comment += jsdoc_comment[1]?.trim();
 			}
 			return {
 				type: match[1],

From 83d0c5894dc26c92274f162c9f9495038cabe37d Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 21 Mar 2025 09:52:51 -0400
Subject: [PATCH 08/23] docs: add note on effect-local state (#15572)

---
 documentation/docs/02-runes/04-$effect.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/documentation/docs/02-runes/04-$effect.md b/documentation/docs/02-runes/04-$effect.md
index 6a2b565aea..75f59102f9 100644
--- a/documentation/docs/02-runes/04-$effect.md
+++ b/documentation/docs/02-runes/04-$effect.md
@@ -74,6 +74,8 @@ Teardown functions also run when the effect is destroyed, which happens when its
 
 `$effect` automatically picks up any reactive values (`$state`, `$derived`, `$props`) that are _synchronously_ read inside its function body (including indirectly, via function calls) and registers them as dependencies. When those dependencies change, the `$effect` schedules a re-run.
 
+If `$state` and `$derived` are used directly inside the `$effect` (for example, during creation of a [reactive class](https://svelte.dev/docs/svelte/$state#Classes)), those values will _not_ be treated as dependencies.
+
 Values that are read _asynchronously_ — after an `await` or inside a `setTimeout`, for example — will not be tracked. Here, the canvas will be repainted when `color` changes, but not when `size` changes ([demo](/playground/untitled#H4sIAAAAAAAAE31T246bMBD9lZF3pWSlBEirfaEQqdo_2PatVIpjBrDkGGQPJGnEv1e2IZfVal-wfHzmzJyZ4cIqqdCy9M-F0blDlnqArZjmB3f72XWRHVCRw_bc4me4aDWhJstSlllhZEfbQhekkMDKfwg5PFvihMvX5OXH_CJa1Zrb0-Kpqr5jkiwC48rieuDWQbqgZ6wqFLRcvkC-hYvnkWi1dWqa8ESQTxFRjfQWsOXiWzmr0sSLhEJu3p1YsoJkNUcdZUnN9dagrBu6FVRQHAM10sJRKgUG16bXcGxQ44AGdt7SDkTDdY02iqLHnJVU6hedlWuIp94JW6Tf8oBt_8GdTxlF0b4n0C35ZLBzXb3mmYn3ae6cOW74zj0YVzDNYXRHFt9mprNgHfZSl6mzml8CMoLvTV6wTZIUDEJv5us2iwMtiJRyAKG4tXnhl8O0yhbML0Wm-B7VNlSSSd31BG7z8oIZZ6dgIffAVY_5xdU9Qrz1Bnx8fCfwtZ7v8Qc9j3nB8PqgmMWlHIID6-bkVaPZwDySfWtKNGtquxQ23Qlsq2QJT0KIqb8dL0up6xQ2eIBkAg_c1FI_YqW0neLnFCqFpwmreedJYT7XX8FVOBfwWRhXstZrSXiwKQjUhOZeMIleb5JZfHWn2Yq5pWEpmR7Hv-N_wEqT8hEEAAA=)):
 
 ```ts

From ade66c6feade92cfd932dcb4be2812305e518d2b Mon Sep 17 00:00:00 2001
From: Paolo Ricciuti <ricciutipaolo@gmail.com>
Date: Fri, 21 Mar 2025 15:21:40 +0100
Subject: [PATCH 09/23] fix: use `get` in constructor for deriveds (#15300)

Co-authored-by: Rich Harris <rich.harris@vercel.com>
---
 .changeset/new-cherries-leave.md               |  5 +++++
 .../client/visitors/MemberExpression.js        |  4 +++-
 .../samples/deriveds-in-constructor/_config.js |  5 +++++
 .../deriveds-in-constructor/main.svelte        | 18 ++++++++++++++++++
 4 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/new-cherries-leave.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/deriveds-in-constructor/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/deriveds-in-constructor/main.svelte

diff --git a/.changeset/new-cherries-leave.md b/.changeset/new-cherries-leave.md
new file mode 100644
index 0000000000..738a78b4a3
--- /dev/null
+++ b/.changeset/new-cherries-leave.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: use `get` in constructor for deriveds
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/MemberExpression.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/MemberExpression.js
index 501ecda555..3f2aada1f5 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/MemberExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/MemberExpression.js
@@ -11,7 +11,9 @@ export function MemberExpression(node, context) {
 	if (node.property.type === 'PrivateIdentifier') {
 		const field = context.state.private_state.get(node.property.name);
 		if (field) {
-			return context.state.in_constructor ? b.member(node, 'v') : b.call('$.get', node);
+			return context.state.in_constructor && (field.kind === 'raw_state' || field.kind === 'state')
+				? b.member(node, 'v')
+				: b.call('$.get', node);
 		}
 	}
 
diff --git a/packages/svelte/tests/runtime-runes/samples/deriveds-in-constructor/_config.js b/packages/svelte/tests/runtime-runes/samples/deriveds-in-constructor/_config.js
new file mode 100644
index 0000000000..b364a989f4
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/deriveds-in-constructor/_config.js
@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	html: `<p>state,derived state,derived.by derived state</p>`
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/deriveds-in-constructor/main.svelte b/packages/svelte/tests/runtime-runes/samples/deriveds-in-constructor/main.svelte
new file mode 100644
index 0000000000..bc8efba7e7
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/deriveds-in-constructor/main.svelte
@@ -0,0 +1,18 @@
+<script>
+	class Foo {
+		#state = $state('state')
+		#derived = $derived('derived ' + this.#state);
+		#derivedBy = $derived.by(() => {
+			return 'derived.by ' + this.#derived 
+		});
+		
+		initial
+		
+		constructor() {
+			this.initial = [this.#state, this.#derived, this.#derivedBy]
+		}
+	}
+	const foo = new Foo()
+</script>
+
+<p>{foo.initial}</p>
\ No newline at end of file

From 1f37c02f918d6fa4d8a14de5d6868228e61dd05a Mon Sep 17 00:00:00 2001
From: Dominic Gannaway <trueadm@users.noreply.github.com>
Date: Fri, 21 Mar 2025 14:25:46 +0000
Subject: [PATCH 10/23] fix: ensure toStore root effect is connected to correct
 parent effect (#15574)

* fix: ensure toStore root effect is connected to correct parent effect

* prettier

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>
---
 .changeset/twelve-bananas-destroy.md          |  5 +++
 packages/svelte/src/store/index-client.js     | 35 +++++++++++++++----
 .../samples/toStore-subscribe2/_config.js     | 16 +++++++++
 .../samples/toStore-subscribe2/main.svelte    | 11 ++++++
 4 files changed, 60 insertions(+), 7 deletions(-)
 create mode 100644 .changeset/twelve-bananas-destroy.md
 create mode 100644 packages/svelte/tests/runtime-runes/samples/toStore-subscribe2/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/toStore-subscribe2/main.svelte

diff --git a/.changeset/twelve-bananas-destroy.md b/.changeset/twelve-bananas-destroy.md
new file mode 100644
index 0000000000..873ee21877
--- /dev/null
+++ b/.changeset/twelve-bananas-destroy.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: ensure toStore root effect is connected to correct parent effect
diff --git a/packages/svelte/src/store/index-client.js b/packages/svelte/src/store/index-client.js
index ae6806ec76..2f0a1a831a 100644
--- a/packages/svelte/src/store/index-client.js
+++ b/packages/svelte/src/store/index-client.js
@@ -6,6 +6,12 @@ import {
 } from '../internal/client/reactivity/effects.js';
 import { get, writable } from './shared/index.js';
 import { createSubscriber } from '../reactivity/create-subscriber.js';
+import {
+	active_effect,
+	active_reaction,
+	set_active_effect,
+	set_active_reaction
+} from '../internal/client/runtime.js';
 
 export { derived, get, readable, readonly, writable } from './shared/index.js';
 
@@ -39,19 +45,34 @@ export { derived, get, readable, readonly, writable } from './shared/index.js';
  * @returns {Writable<V> | Readable<V>}
  */
 export function toStore(get, set) {
-	let init_value = get();
+	var effect = active_effect;
+	var reaction = active_reaction;
+	var init_value = get();
+
 	const store = writable(init_value, (set) => {
 		// If the value has changed before we call subscribe, then
 		// we need to treat the value as already having run
-		let ran = init_value !== get();
+		var ran = init_value !== get();
 
 		// TODO do we need a different implementation on the server?
-		const teardown = effect_root(() => {
-			render_effect(() => {
-				const value = get();
-				if (ran) set(value);
+		var teardown;
+		// Apply the reaction and effect at the time of toStore being called
+		var previous_reaction = active_reaction;
+		var previous_effect = active_effect;
+		set_active_reaction(reaction);
+		set_active_effect(effect);
+
+		try {
+			teardown = effect_root(() => {
+				render_effect(() => {
+					const value = get();
+					if (ran) set(value);
+				});
 			});
-		});
+		} finally {
+			set_active_reaction(previous_reaction);
+			set_active_effect(previous_effect);
+		}
 
 		ran = true;
 
diff --git a/packages/svelte/tests/runtime-runes/samples/toStore-subscribe2/_config.js b/packages/svelte/tests/runtime-runes/samples/toStore-subscribe2/_config.js
new file mode 100644
index 0000000000..bc1793e7a4
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/toStore-subscribe2/_config.js
@@ -0,0 +1,16 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		let btn = target.querySelector('button');
+
+		btn?.click();
+		flushSync();
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`<div>Count 1!</div><div>Count from store 1!</div><button>Add 1</button>`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/toStore-subscribe2/main.svelte b/packages/svelte/tests/runtime-runes/samples/toStore-subscribe2/main.svelte
new file mode 100644
index 0000000000..82d20105b8
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/toStore-subscribe2/main.svelte
@@ -0,0 +1,11 @@
+<script>
+	import { toStore } from "svelte/store";
+
+	let counter = $state(0);
+	const count = toStore(() => counter, value => counter = value);
+</script>
+
+<div>Count {counter}!</div>
+<div>Count from store {$count}!</div>
+
+<button onclick={() => counter+=1}>Add 1</button>

From 842a7c6995f94f46b1839fcac91042fd541e52ca Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 21 Mar 2025 10:26:15 -0400
Subject: [PATCH 11/23] docs: update state_unsafe_mutation message (#15539)

* docs: update state_unsafe_mutation message

* regenerate

* fix example
---
 .../98-reference/.generated/client-errors.md  | 35 +++++++++++--------
 .../svelte/messages/client-errors/errors.md   | 35 +++++++++++--------
 2 files changed, 40 insertions(+), 30 deletions(-)

diff --git a/documentation/docs/98-reference/.generated/client-errors.md b/documentation/docs/98-reference/.generated/client-errors.md
index 62d9c3302a..901c49822c 100644
--- a/documentation/docs/98-reference/.generated/client-errors.md
+++ b/documentation/docs/98-reference/.generated/client-errors.md
@@ -128,26 +128,31 @@ Cannot set prototype of `$state` object
 Updating state inside a derived or a template expression is forbidden. If the value should not be reactive, declare it without `$state`
 ```
 
-This error is thrown in a situation like this:
+This error occurs when state is updated while evaluating a `$derived`. You might encounter it while trying to 'derive' two pieces of state in one go:
 
 ```svelte
 <script>
-    let count = $state(0);
-    let multiple = $derived.by(() => {
-        const result = count * 2;
-        if (result > 10) {
-            count = 0;
-        }
-        return result;
-    });
+	let count = $state(0);
+
+	let even = $state(true);
+
+	let odd = $derived.by(() => {
+		even = count % 2 === 0;
+		return !even;
+	});
 </script>
 
-<button onclick={() => count++}>{count} / {multiple}</button>
+<button onclick={() => count++}>{count}</button>
+
+<p>{count} is even: {even}</p>
+<p>{count} is odd: {odd}</p>
 ```
 
-Here, the `$derived` updates `count`, which is `$state` and therefore forbidden to do. It is forbidden because the reactive graph could become unstable as a result, leading to subtle bugs, like values being stale or effects firing in the wrong order. To prevent this, Svelte errors when detecting an update to a `$state` variable.
+This is forbidden because it introduces instability: if `<p>{count} is even: {even}</p>` is updated before `odd` is recalculated, `even` will be stale. In most cases the solution is to make everything derived:
+
+```js
+let even = $derived(count % 2 === 0);
+let odd = $derived(!even);
+```
 
-To fix this:
-- See if it's possible to refactor your `$derived` such that the update becomes unnecessary
-- Think about why you need to update `$state` inside a `$derived` in the first place. Maybe it's because you're using `bind:`, which leads you down a bad code path, and separating input and output path (by splitting it up to an attribute and an event, or by using [Function bindings](bind#Function-bindings)) makes it possible avoid the update
-- If it's unavoidable, you may need to use an [`$effect`]($effect) instead. This could include splitting parts of the `$derived` into an [`$effect`]($effect) which does the updates
+If side-effects are unavoidable, use [`$effect`]($effect) instead.
diff --git a/packages/svelte/messages/client-errors/errors.md b/packages/svelte/messages/client-errors/errors.md
index bc8ec36256..572930843e 100644
--- a/packages/svelte/messages/client-errors/errors.md
+++ b/packages/svelte/messages/client-errors/errors.md
@@ -84,26 +84,31 @@ See the [migration guide](/docs/svelte/v5-migration-guide#Components-are-no-long
 
 > Updating state inside a derived or a template expression is forbidden. If the value should not be reactive, declare it without `$state`
 
-This error is thrown in a situation like this:
+This error occurs when state is updated while evaluating a `$derived`. You might encounter it while trying to 'derive' two pieces of state in one go:
 
 ```svelte
 <script>
-    let count = $state(0);
-    let multiple = $derived.by(() => {
-        const result = count * 2;
-        if (result > 10) {
-            count = 0;
-        }
-        return result;
-    });
+	let count = $state(0);
+
+	let even = $state(true);
+
+	let odd = $derived.by(() => {
+		even = count % 2 === 0;
+		return !even;
+	});
 </script>
 
-<button onclick={() => count++}>{count} / {multiple}</button>
+<button onclick={() => count++}>{count}</button>
+
+<p>{count} is even: {even}</p>
+<p>{count} is odd: {odd}</p>
 ```
 
-Here, the `$derived` updates `count`, which is `$state` and therefore forbidden to do. It is forbidden because the reactive graph could become unstable as a result, leading to subtle bugs, like values being stale or effects firing in the wrong order. To prevent this, Svelte errors when detecting an update to a `$state` variable.
+This is forbidden because it introduces instability: if `<p>{count} is even: {even}</p>` is updated before `odd` is recalculated, `even` will be stale. In most cases the solution is to make everything derived:
+
+```js
+let even = $derived(count % 2 === 0);
+let odd = $derived(!even);
+```
 
-To fix this:
-- See if it's possible to refactor your `$derived` such that the update becomes unnecessary
-- Think about why you need to update `$state` inside a `$derived` in the first place. Maybe it's because you're using `bind:`, which leads you down a bad code path, and separating input and output path (by splitting it up to an attribute and an event, or by using [Function bindings](bind#Function-bindings)) makes it possible avoid the update
-- If it's unavoidable, you may need to use an [`$effect`]($effect) instead. This could include splitting parts of the `$derived` into an [`$effect`]($effect) which does the updates
+If side-effects are unavoidable, use [`$effect`]($effect) instead.

From 2d3b65dfbd589416d94661bd34ed7a99896bcde2 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Fri, 21 Mar 2025 10:28:23 -0400
Subject: [PATCH 12/23] Version Packages (#15575)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 .changeset/new-cherries-leave.md     | 5 -----
 .changeset/twelve-bananas-destroy.md | 5 -----
 packages/svelte/CHANGELOG.md         | 8 ++++++++
 packages/svelte/package.json         | 2 +-
 packages/svelte/src/version.js       | 2 +-
 5 files changed, 10 insertions(+), 12 deletions(-)
 delete mode 100644 .changeset/new-cherries-leave.md
 delete mode 100644 .changeset/twelve-bananas-destroy.md

diff --git a/.changeset/new-cherries-leave.md b/.changeset/new-cherries-leave.md
deleted file mode 100644
index 738a78b4a3..0000000000
--- a/.changeset/new-cherries-leave.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: use `get` in constructor for deriveds
diff --git a/.changeset/twelve-bananas-destroy.md b/.changeset/twelve-bananas-destroy.md
deleted file mode 100644
index 873ee21877..0000000000
--- a/.changeset/twelve-bananas-destroy.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: ensure toStore root effect is connected to correct parent effect
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index 8cb7efd4ef..04ddfcadbd 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,13 @@
 # svelte
 
+## 5.24.1
+
+### Patch Changes
+
+- fix: use `get` in constructor for deriveds ([#15300](https://github.com/sveltejs/svelte/pull/15300))
+
+- fix: ensure toStore root effect is connected to correct parent effect ([#15574](https://github.com/sveltejs/svelte/pull/15574))
+
 ## 5.24.0
 
 ### Minor Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index 0aa6b29841..f321571e7a 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": "5.24.0",
+  "version": "5.24.1",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index 7cd43e74cb..565c190713 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 = '5.24.0';
+export const VERSION = '5.24.1';
 export const PUBLIC_VERSION = '5';

From 5a8fa69dbf46e99beed812157ed78609f8054331 Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 21 Mar 2025 12:54:53 -0400
Subject: [PATCH 13/23] feat: make deriveds writable (#15570)

* feat: make deriveds writable

* add optimistic UI example

* add note to when-not-to-use-effect

* add section on deep reactivity

* root-relative URL

* use hash URL

* mention const

* make handler async, move into script block
---
 .changeset/clever-terms-tell.md               |  5 ++
 documentation/docs/02-runes/03-$derived.md    | 42 +++++++++++++++++
 documentation/docs/02-runes/04-$effect.md     |  2 +
 .../phases/2-analyze/visitors/shared/utils.js | 31 +------------
 .../runes-no-derived-assignment/_config.js    |  8 ----
 .../runes-no-derived-assignment/main.svelte   |  5 --
 .../runes-no-derived-binding/_config.js       |  8 ----
 .../runes-no-derived-binding/main.svelte      |  6 ---
 .../_config.js                                |  8 ----
 .../main.svelte                               | 10 ----
 .../_config.js                                |  8 ----
 .../main.svelte                               | 10 ----
 .../runes-no-derived-update/_config.js        |  8 ----
 .../runes-no-derived-update/main.svelte       |  5 --
 .../samples/writable-derived/_config.js       | 46 +++++++++++++++++++
 .../samples/writable-derived/main.svelte      |  9 ++++
 .../reassign-derived-literal/errors.json      | 14 ------
 .../reassign-derived-literal/input.svelte     |  9 ----
 .../errors.json                               | 14 ------
 .../input.svelte                              |  9 ----
 .../reassign-derived-public-field/errors.json | 14 ------
 .../input.svelte                              |  9 ----
 22 files changed, 105 insertions(+), 175 deletions(-)
 create mode 100644 .changeset/clever-terms-tell.md
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-assignment/_config.js
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-assignment/main.svelte
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-binding/_config.js
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-binding/main.svelte
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-assignment/_config.js
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-assignment/main.svelte
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-update/_config.js
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-update/main.svelte
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-update/_config.js
 delete mode 100644 packages/svelte/tests/compiler-errors/samples/runes-no-derived-update/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/writable-derived/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/writable-derived/main.svelte
 delete mode 100644 packages/svelte/tests/validator/samples/reassign-derived-literal/errors.json
 delete mode 100644 packages/svelte/tests/validator/samples/reassign-derived-literal/input.svelte
 delete mode 100644 packages/svelte/tests/validator/samples/reassign-derived-private-field/errors.json
 delete mode 100644 packages/svelte/tests/validator/samples/reassign-derived-private-field/input.svelte
 delete mode 100644 packages/svelte/tests/validator/samples/reassign-derived-public-field/errors.json
 delete mode 100644 packages/svelte/tests/validator/samples/reassign-derived-public-field/input.svelte

diff --git a/.changeset/clever-terms-tell.md b/.changeset/clever-terms-tell.md
new file mode 100644
index 0000000000..606868bce3
--- /dev/null
+++ b/.changeset/clever-terms-tell.md
@@ -0,0 +1,5 @@
+---
+'svelte': minor
+---
+
+feat: make deriveds writable
diff --git a/documentation/docs/02-runes/03-$derived.md b/documentation/docs/02-runes/03-$derived.md
index 24ab643b68..2464aa9295 100644
--- a/documentation/docs/02-runes/03-$derived.md
+++ b/documentation/docs/02-runes/03-$derived.md
@@ -52,6 +52,48 @@ Anything read synchronously inside the `$derived` expression (or `$derived.by` f
 
 To exempt a piece of state from being treated as a dependency, use [`untrack`](svelte#untrack).
 
+## Overriding derived values
+
+Derived expressions are recalculated when their dependencies change, but you can temporarily override their values by reassigning them (unless they are declared with `const`). This can be useful for things like _optimistic UI_, where a value is derived from the 'source of truth' (such as data from your server) but you'd like to show immediate feedback to the user:
+
+```svelte
+<script>
+	let { post, like } = $props();
+
+	let likes = $derived(post.likes);
+
+	async function onclick() {
+		// increment the `likes` count immediately...
+		likes += 1;
+
+		// and tell the server, which will eventually update `post`
+		try {
+			await like();
+		} catch {
+			// failed! roll back the change
+			likes -= 1;
+		}
+	}
+</script>
+
+<button {onclick}>🧡 {likes}</button>
+```
+
+> [!NOTE] Prior to Svelte 5.25, deriveds were read-only.
+
+## Deriveds and reactivity
+
+Unlike `$state`, which converts objects and arrays to [deeply reactive proxies]($state#Deep-state), `$derived` values are left as-is. For example, [in a case like this](/playground/untitled#H4sIAAAAAAAAE4VU22rjMBD9lUHd3aaQi9PdstS1A3t5XvpQ2Ic4D7I1iUUV2UjjNMX431eS7TRdSosxgjMzZ45mjt0yzffIYibvy0ojFJWqDKCQVBk2ZVup0LJ43TJ6rn2aBxw-FP2o67k9oCKP5dziW3hRaUJNjoYltjCyplWmM1JIIAn3FlL4ZIkTTtYez6jtj4w8WwyXv9GiIXiQxLVs9pfTMR7EuoSLIuLFbX7Z4930bZo_nBrD1bs834tlfvsBz9_SyX6PZXu9XaL4gOWn4sXjeyzftv4ZWfyxubpzxzg6LfD4MrooxELEosKCUPigQCMPKCZh0OtQE1iSxcsmdHuBvCiHZXALLXiN08EL3RRkaJ_kDVGle0HcSD5TPEeVtj67O4Nrg9aiSNtBY5oODJkrL5QsHtN2cgXp6nSJMWzpWWGasdlsGEMbzi5jPr5KFr0Ep7pdeM2-TCelCddIhDxAobi1jqF3cMaC1RKp64bAW9iFAmXGIHfd4wNXDabtOLN53w8W53VvJoZLh7xk4Rr3CoL-UNoLhWHrT1JQGcM17u96oES5K-kc2XOzkzqGCKL5De79OUTyyrg1zgwXsrEx3ESfx4Bz0M5UjVMHB24mw9SuXtXFoN13fYKOM1tyUT3FbvbWmSWCZX2Er-41u5xPoml45svRahl9Wb9aasbINJixDZwcPTbyTLZSUsAvrg_cPuCR7s782_WU8343Y72Qtlb8OYatwuOQvuN13M_hJKNfxann1v1U_B1KZ_D_mzhzhz24fw85CSz2irtN9w9HshBK7AQAAA==)...
+
+```svelte
+let items = $state([...]);
+
+let index = $state(0);
+let selected = $derived(items[index]);
+```
+
+...you can change (or `bind:` to) properties of `selected` and it will affect the underlying `items` array. If `items` was _not_ deeply reactive, mutating `selected` would have no effect.
+
 ## Update propagation
 
 Svelte uses something called _push-pull reactivity_ — when state is updated, everything that depends on the state (whether directly or indirectly) is immediately notified of the change (the 'push'), but derived values are not re-evaluated until they are actually read (the 'pull').
diff --git a/documentation/docs/02-runes/04-$effect.md b/documentation/docs/02-runes/04-$effect.md
index 75f59102f9..ae1a2146c9 100644
--- a/documentation/docs/02-runes/04-$effect.md
+++ b/documentation/docs/02-runes/04-$effect.md
@@ -254,6 +254,8 @@ In general, `$effect` is best considered something of an escape hatch — useful
 
 > [!NOTE] For things that are more complicated than a simple expression like `count * 2`, you can also use `$derived.by`.
 
+If you're using an effect because you want to be able to reassign the derived value (to build an optimistic UI, for example) note that [deriveds can be directly overridden]($derived#Overriding-derived-values) as of Svelte 5.25.
+
 You might be tempted to do something convoluted with effects to link one value to another. The following example shows two inputs for "money spent" and "money left" that are connected to each other. If you update one, the other should update accordingly. Don't use effects for this ([demo](/playground/untitled#H4sIAAAAAAAACpVRy26DMBD8FcvKgUhtoIdeHBwp31F6MGSJkBbHwksEQvx77aWQqooq9bgzOzP7mGTdIHipPiZJowOpGJAv0po2VmfnDv4OSBErjYdneHWzBJaCjcx91TWOToUtCIEE3cig0OIty44r5l1oDtjOkyFIsv3GINQ_CNYyGegd1DVUlCR7oU9iilDUcP8S8roYs9n8p2wdYNVFm4csTx872BxNCcjr5I11fdgonEkXsjP2CoUUZWMv6m6wBz2x7yxaM-iJvWeRsvSbSVeUy5i0uf8vKA78NIeJLSZWv1I8jQjLdyK4XuTSeIdmVKJGGI4LdjVOiezwDu1yG74My8PLCQaSiroe5s_5C2PHrkVGAgAA)):
 
 ```svelte
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/shared/utils.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/shared/utils.js
index 04f4347a40..d6c74eddb6 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/shared/utils.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/shared/utils.js
@@ -21,10 +21,6 @@ export function validate_assignment(node, argument, state) {
 		const binding = state.scope.get(argument.name);
 
 		if (state.analysis.runes) {
-			if (binding?.kind === 'derived') {
-				e.constant_assignment(node, 'derived state');
-			}
-
 			if (binding?.node === state.analysis.props_id) {
 				e.constant_assignment(node, '$props.id()');
 			}
@@ -38,25 +34,6 @@ export function validate_assignment(node, argument, state) {
 			e.snippet_parameter_assignment(node);
 		}
 	}
-	if (
-		argument.type === 'MemberExpression' &&
-		argument.object.type === 'ThisExpression' &&
-		(((argument.property.type === 'PrivateIdentifier' || argument.property.type === 'Identifier') &&
-			state.derived_state.some(
-				(derived) =>
-					derived.name === /** @type {PrivateIdentifier | Identifier} */ (argument.property).name &&
-					derived.private === (argument.property.type === 'PrivateIdentifier')
-			)) ||
-			(argument.property.type === 'Literal' &&
-				argument.property.value &&
-				typeof argument.property.value === 'string' &&
-				state.derived_state.some(
-					(derived) =>
-						derived.name === /** @type {Literal} */ (argument.property).value && !derived.private
-				)))
-	) {
-		e.constant_assignment(node, 'derived state');
-	}
 }
 
 /**
@@ -81,7 +58,6 @@ export function validate_no_const_assignment(node, argument, scope, is_binding)
 	} else if (argument.type === 'Identifier') {
 		const binding = scope.get(argument.name);
 		if (
-			binding?.kind === 'derived' ||
 			binding?.declaration_kind === 'import' ||
 			(binding?.declaration_kind === 'const' && binding.kind !== 'each')
 		) {
@@ -96,12 +72,7 @@ export function validate_no_const_assignment(node, argument, scope, is_binding)
 			// );
 
 			// TODO have a more specific error message for assignments to things like `{:then foo}`
-			const thing =
-				binding.declaration_kind === 'import'
-					? 'import'
-					: binding.kind === 'derived'
-						? 'derived state'
-						: 'constant';
+			const thing = binding.declaration_kind === 'import' ? 'import' : 'constant';
 
 			if (is_binding) {
 				e.constant_binding(node, thing);
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-assignment/_config.js b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-assignment/_config.js
deleted file mode 100644
index 94985a9939..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-assignment/_config.js
+++ /dev/null
@@ -1,8 +0,0 @@
-import { test } from '../../test';
-
-export default test({
-	error: {
-		code: 'constant_assignment',
-		message: 'Cannot assign to derived state'
-	}
-});
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-assignment/main.svelte b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-assignment/main.svelte
deleted file mode 100644
index 3bf836f6c5..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-assignment/main.svelte
+++ /dev/null
@@ -1,5 +0,0 @@
-<script>
-	const a = $state(0);
-	let b = $derived(a);
-	b = 1;
-</script>
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-binding/_config.js b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-binding/_config.js
deleted file mode 100644
index 87b88d79cc..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-binding/_config.js
+++ /dev/null
@@ -1,8 +0,0 @@
-import { test } from '../../test';
-
-export default test({
-	error: {
-		code: 'constant_binding',
-		message: 'Cannot bind to derived state'
-	}
-});
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-binding/main.svelte b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-binding/main.svelte
deleted file mode 100644
index 6c198dc068..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-binding/main.svelte
+++ /dev/null
@@ -1,6 +0,0 @@
-<script>
-	let a = $state(0);
-	let b = $derived({ a });
-</script>
-
-<input type="number" bind:value={b} />
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-assignment/_config.js b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-assignment/_config.js
deleted file mode 100644
index 94985a9939..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-assignment/_config.js
+++ /dev/null
@@ -1,8 +0,0 @@
-import { test } from '../../test';
-
-export default test({
-	error: {
-		code: 'constant_assignment',
-		message: 'Cannot assign to derived state'
-	}
-});
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-assignment/main.svelte b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-assignment/main.svelte
deleted file mode 100644
index d44806757e..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-assignment/main.svelte
+++ /dev/null
@@ -1,10 +0,0 @@
-<script>
-	class Counter {
-		count = $state();
-		#doubled = $derived(this.count * 2);
-
-		nope() {
-			this.#doubled += 1;
-		}
-	}
-</script>
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-update/_config.js b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-update/_config.js
deleted file mode 100644
index 94985a9939..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-update/_config.js
+++ /dev/null
@@ -1,8 +0,0 @@
-import { test } from '../../test';
-
-export default test({
-	error: {
-		code: 'constant_assignment',
-		message: 'Cannot assign to derived state'
-	}
-});
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-update/main.svelte b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-update/main.svelte
deleted file mode 100644
index e4ee2e8635..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-state-field-update/main.svelte
+++ /dev/null
@@ -1,10 +0,0 @@
-<script>
-	class Counter {
-		count = $state();
-		#doubled = $derived(this.count * 2);
-
-		nope() {
-			this.#doubled++;
-		}
-	}
-</script>
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-update/_config.js b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-update/_config.js
deleted file mode 100644
index 94985a9939..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-update/_config.js
+++ /dev/null
@@ -1,8 +0,0 @@
-import { test } from '../../test';
-
-export default test({
-	error: {
-		code: 'constant_assignment',
-		message: 'Cannot assign to derived state'
-	}
-});
diff --git a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-update/main.svelte b/packages/svelte/tests/compiler-errors/samples/runes-no-derived-update/main.svelte
deleted file mode 100644
index d266c95bb8..0000000000
--- a/packages/svelte/tests/compiler-errors/samples/runes-no-derived-update/main.svelte
+++ /dev/null
@@ -1,5 +0,0 @@
-<script>
-	const a = $state(0);
-	let b = $derived(a);
-	b++;
-</script>
diff --git a/packages/svelte/tests/runtime-runes/samples/writable-derived/_config.js b/packages/svelte/tests/runtime-runes/samples/writable-derived/_config.js
new file mode 100644
index 0000000000..b48ccbdfd0
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/writable-derived/_config.js
@@ -0,0 +1,46 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	html: `
+		<input type="range"><input type="range"><p>0 * 2 = 0</p>
+	`,
+
+	ssrHtml: `
+		<input type="range" value="0"><input type="range" value="0"><p>0 * 2 = 0</p>
+	`,
+
+	test({ assert, target, window }) {
+		const [input1, input2] = target.querySelectorAll('input');
+
+		flushSync(() => {
+			input1.value = '10';
+			input1.dispatchEvent(new window.Event('input', { bubbles: true }));
+		});
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="range"><input type="range"><p>10 * 2 = 20</p>`
+		);
+
+		flushSync(() => {
+			input2.value = '99';
+			input2.dispatchEvent(new window.Event('input', { bubbles: true }));
+		});
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="range"><input type="range"><p>10 * 2 = 99</p>`
+		);
+
+		flushSync(() => {
+			input1.value = '20';
+			input1.dispatchEvent(new window.Event('input', { bubbles: true }));
+		});
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="range"><input type="range"><p>20 * 2 = 40</p>`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/writable-derived/main.svelte b/packages/svelte/tests/runtime-runes/samples/writable-derived/main.svelte
new file mode 100644
index 0000000000..ab1dde0b9b
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/writable-derived/main.svelte
@@ -0,0 +1,9 @@
+<script>
+	let count = $state(0);
+	let double = $derived(count * 2);
+</script>
+
+<input type="range" bind:value={count} />
+<input type="range" bind:value={double} />
+
+<p>{count} * 2 = {double}</p>
diff --git a/packages/svelte/tests/validator/samples/reassign-derived-literal/errors.json b/packages/svelte/tests/validator/samples/reassign-derived-literal/errors.json
deleted file mode 100644
index 8681d84ab2..0000000000
--- a/packages/svelte/tests/validator/samples/reassign-derived-literal/errors.json
+++ /dev/null
@@ -1,14 +0,0 @@
-[
-	{
-		"code": "constant_assignment",
-		"message": "Cannot assign to derived state",
-		"start": {
-			"column": 3,
-			"line": 6
-		},
-		"end": {
-			"column": 29,
-			"line": 6
-		}
-	}
-]
diff --git a/packages/svelte/tests/validator/samples/reassign-derived-literal/input.svelte b/packages/svelte/tests/validator/samples/reassign-derived-literal/input.svelte
deleted file mode 100644
index 8f109c9e1f..0000000000
--- a/packages/svelte/tests/validator/samples/reassign-derived-literal/input.svelte
+++ /dev/null
@@ -1,9 +0,0 @@
-<script>
-	class Test{
-		der = $derived({ test: 0 });
-
-		set test(v){
-			this["der"] = { test: 45 };
-		}
-	}
-</script>
\ No newline at end of file
diff --git a/packages/svelte/tests/validator/samples/reassign-derived-private-field/errors.json b/packages/svelte/tests/validator/samples/reassign-derived-private-field/errors.json
deleted file mode 100644
index c211aa4608..0000000000
--- a/packages/svelte/tests/validator/samples/reassign-derived-private-field/errors.json
+++ /dev/null
@@ -1,14 +0,0 @@
-[
-	{
-		"code": "constant_assignment",
-		"message": "Cannot assign to derived state",
-		"start": {
-			"column": 3,
-			"line": 6
-		},
-		"end": {
-			"column": 27,
-			"line": 6
-		}
-	}
-]
diff --git a/packages/svelte/tests/validator/samples/reassign-derived-private-field/input.svelte b/packages/svelte/tests/validator/samples/reassign-derived-private-field/input.svelte
deleted file mode 100644
index 62e2317e03..0000000000
--- a/packages/svelte/tests/validator/samples/reassign-derived-private-field/input.svelte
+++ /dev/null
@@ -1,9 +0,0 @@
-<script>
-	class Test{
-		#der = $derived({ test: 0 });
-
-		set test(v){
-			this.#der = { test: 45 };
-		}
-	}
-</script>
\ No newline at end of file
diff --git a/packages/svelte/tests/validator/samples/reassign-derived-public-field/errors.json b/packages/svelte/tests/validator/samples/reassign-derived-public-field/errors.json
deleted file mode 100644
index 98837589ac..0000000000
--- a/packages/svelte/tests/validator/samples/reassign-derived-public-field/errors.json
+++ /dev/null
@@ -1,14 +0,0 @@
-[
-	{
-		"code": "constant_assignment",
-		"message": "Cannot assign to derived state",
-		"start": {
-			"column": 3,
-			"line": 6
-		},
-		"end": {
-			"column": 26,
-			"line": 6
-		}
-	}
-]
diff --git a/packages/svelte/tests/validator/samples/reassign-derived-public-field/input.svelte b/packages/svelte/tests/validator/samples/reassign-derived-public-field/input.svelte
deleted file mode 100644
index e2c4693e86..0000000000
--- a/packages/svelte/tests/validator/samples/reassign-derived-public-field/input.svelte
+++ /dev/null
@@ -1,9 +0,0 @@
-<script>
-	class Test{
-		der = $derived({ test: 0 });
-
-		set test(v){
-			this.der = { test: 45 };
-		}
-	}
-</script>
\ No newline at end of file

From 6e343b9ad7bca473947cbee0c7ea9455d9485599 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Fri, 21 Mar 2025 13:01:58 -0400
Subject: [PATCH 14/23] Version Packages (#15578)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 .changeset/clever-terms-tell.md | 5 -----
 packages/svelte/CHANGELOG.md    | 6 ++++++
 packages/svelte/package.json    | 2 +-
 packages/svelte/src/version.js  | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)
 delete mode 100644 .changeset/clever-terms-tell.md

diff --git a/.changeset/clever-terms-tell.md b/.changeset/clever-terms-tell.md
deleted file mode 100644
index 606868bce3..0000000000
--- a/.changeset/clever-terms-tell.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': minor
----
-
-feat: make deriveds writable
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index 04ddfcadbd..4bac129169 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,11 @@
 # svelte
 
+## 5.25.0
+
+### Minor Changes
+
+- feat: make deriveds writable ([#15570](https://github.com/sveltejs/svelte/pull/15570))
+
 ## 5.24.1
 
 ### Patch Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index f321571e7a..e3824b89fb 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": "5.24.1",
+  "version": "5.25.0",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index 565c190713..a62190bb2e 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 = '5.24.1';
+export const VERSION = '5.25.0';
 export const PUBLIC_VERSION = '5';

From 441108b8ff28a6c1aa8e38f5c041a2583446167e Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 21 Mar 2025 13:06:46 -0400
Subject: [PATCH 15/23] fix docs

---
 documentation/docs/98-reference/.generated/client-errors.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/documentation/docs/98-reference/.generated/client-errors.md b/documentation/docs/98-reference/.generated/client-errors.md
index 901c49822c..fd9419176d 100644
--- a/documentation/docs/98-reference/.generated/client-errors.md
+++ b/documentation/docs/98-reference/.generated/client-errors.md
@@ -151,6 +151,8 @@ This error occurs when state is updated while evaluating a `$derived`. You might
 This is forbidden because it introduces instability: if `<p>{count} is even: {even}</p>` is updated before `odd` is recalculated, `even` will be stale. In most cases the solution is to make everything derived:
 
 ```js
+let count = 0;
+// ---cut---
 let even = $derived(count % 2 === 0);
 let odd = $derived(!even);
 ```

From ef98ccae8b27dbac393623c166ea890b515d5e1d Mon Sep 17 00:00:00 2001
From: Rich Harris <rich.harris@vercel.com>
Date: Fri, 21 Mar 2025 15:44:23 -0400
Subject: [PATCH 16/23] doh

---
 documentation/docs/98-reference/.generated/client-errors.md | 2 --
 1 file changed, 2 deletions(-)

diff --git a/documentation/docs/98-reference/.generated/client-errors.md b/documentation/docs/98-reference/.generated/client-errors.md
index fd9419176d..901c49822c 100644
--- a/documentation/docs/98-reference/.generated/client-errors.md
+++ b/documentation/docs/98-reference/.generated/client-errors.md
@@ -151,8 +151,6 @@ This error occurs when state is updated while evaluating a `$derived`. You might
 This is forbidden because it introduces instability: if `<p>{count} is even: {even}</p>` is updated before `odd` is recalculated, `even` will be stale. In most cases the solution is to make everything derived:
 
 ```js
-let count = 0;
-// ---cut---
 let even = $derived(count % 2 === 0);
 let odd = $derived(!even);
 ```

From d1bd32ec9ec06e6505740a0de5f5b2281546787c Mon Sep 17 00:00:00 2001
From: Blade Barringer <blade@crookedneighbor.com>
Date: Fri, 21 Mar 2025 14:46:20 -0500
Subject: [PATCH 17/23] fix: allow get_proxied_value to return original value
 when error (#15577)

* fix: allow get_proxied_value to return original value when error

closes #15546

* Update packages/svelte/src/internal/client/proxy.js

---------

Co-authored-by: Rich Harris <hello@rich-harris.dev>
---
 .changeset/afraid-penguins-battle.md         |  5 +++++
 packages/svelte/src/internal/client/proxy.js | 14 ++++++++++++--
 2 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 .changeset/afraid-penguins-battle.md

diff --git a/.changeset/afraid-penguins-battle.md b/.changeset/afraid-penguins-battle.md
new file mode 100644
index 0000000000..2cc5059b9a
--- /dev/null
+++ b/.changeset/afraid-penguins-battle.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: prevent dev server from throwing errors when attempting to retrieve the proxied value of an iframe's contentWindow
diff --git a/packages/svelte/src/internal/client/proxy.js b/packages/svelte/src/internal/client/proxy.js
index ffe63f4b77..fab271c916 100644
--- a/packages/svelte/src/internal/client/proxy.js
+++ b/packages/svelte/src/internal/client/proxy.js
@@ -366,8 +366,18 @@ function update_version(signal, d = 1) {
  * @param {any} value
  */
 export function get_proxied_value(value) {
-	if (value !== null && typeof value === 'object' && STATE_SYMBOL in value) {
-		return value[STATE_SYMBOL];
+	try {
+		if (value !== null && typeof value === 'object' && STATE_SYMBOL in value) {
+			return value[STATE_SYMBOL];
+		}
+	} catch {
+		// the above if check can throw an error if the value in question
+		// is the contentWindow of an iframe on another domain, in which
+		// case we want to just return the value (because it's definitely
+		// not a proxied value) so we don't break any JavaScript interacting
+		// with that iframe (such as various payment companies client side
+		// JavaScript libraries interacting with their iframes on the same
+		// domain)
 	}
 
 	return value;

From c1ae8953aaa81b9191d8d944c4bf0df7fdf4f2ee Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Fri, 21 Mar 2025 17:04:59 -0400
Subject: [PATCH 18/23] Version Packages (#15580)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 .changeset/afraid-penguins-battle.md | 5 -----
 packages/svelte/CHANGELOG.md         | 6 ++++++
 packages/svelte/package.json         | 2 +-
 packages/svelte/src/version.js       | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)
 delete mode 100644 .changeset/afraid-penguins-battle.md

diff --git a/.changeset/afraid-penguins-battle.md b/.changeset/afraid-penguins-battle.md
deleted file mode 100644
index 2cc5059b9a..0000000000
--- a/.changeset/afraid-penguins-battle.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: prevent dev server from throwing errors when attempting to retrieve the proxied value of an iframe's contentWindow
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index 4bac129169..9e99e91b8e 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,11 @@
 # svelte
 
+## 5.25.1
+
+### Patch Changes
+
+- fix: prevent dev server from throwing errors when attempting to retrieve the proxied value of an iframe's contentWindow ([#15577](https://github.com/sveltejs/svelte/pull/15577))
+
 ## 5.25.0
 
 ### Minor Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index e3824b89fb..9d3902696d 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": "5.25.0",
+  "version": "5.25.1",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index a62190bb2e..a4f5a15c8f 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 = '5.25.0';
+export const VERSION = '5.25.1';
 export const PUBLIC_VERSION = '5';

From 33d118f8a29a376e4490f2d31b0b444bf8fa0c7c Mon Sep 17 00:00:00 2001
From: Paolo Ricciuti <ricciutipaolo@gmail.com>
Date: Fri, 21 Mar 2025 23:47:26 +0100
Subject: [PATCH 19/23] feat: migrate reassigned deriveds to `$derived`
 (#15581)

---
 .changeset/forty-snakes-lay.md                  |  5 +++++
 packages/svelte/src/compiler/migrate/index.js   | 17 ++++++++++++++++-
 .../samples/reassigned-deriveds/input.svelte    | 10 ++++++++++
 .../samples/reassigned-deriveds/output.svelte   | 10 ++++++++++
 4 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/forty-snakes-lay.md
 create mode 100644 packages/svelte/tests/migrate/samples/reassigned-deriveds/input.svelte
 create mode 100644 packages/svelte/tests/migrate/samples/reassigned-deriveds/output.svelte

diff --git a/.changeset/forty-snakes-lay.md b/.changeset/forty-snakes-lay.md
new file mode 100644
index 0000000000..6cb4c2d761
--- /dev/null
+++ b/.changeset/forty-snakes-lay.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+feat: migrate reassigned deriveds to `$derived`
diff --git a/packages/svelte/src/compiler/migrate/index.js b/packages/svelte/src/compiler/migrate/index.js
index 7f26d0d010..b336ebb2b8 100644
--- a/packages/svelte/src/compiler/migrate/index.js
+++ b/packages/svelte/src/compiler/migrate/index.js
@@ -19,6 +19,7 @@ import { migrate_svelte_ignore } from '../utils/extract_svelte_ignore.js';
 import { validate_component_options } from '../validate-options.js';
 import { is_reserved, is_svg, is_void } from '../../utils.js';
 import { regex_is_valid_identifier } from '../phases/patterns.js';
+import { VERSION } from 'svelte/compiler';
 
 const regex_style_tags = /(<style[^>]+>)([\S\s]*?)(<\/style>)/g;
 const style_placeholder = '/*$$__STYLE_CONTENT__$$*/';
@@ -113,6 +114,16 @@ function find_closing_parenthesis(start, code) {
 	return end;
 }
 
+function check_support_writable_deriveds() {
+	const [major, minor, patch] = VERSION.split('.');
+
+	if (+major < 5) return false;
+	if (+minor < 25) return false;
+	return true;
+}
+
+const support_writable_derived = check_support_writable_deriveds();
+
 /**
  * Does a best-effort migration of Svelte code towards using runes, event attributes and render tags.
  * May throw an error if the code is too complex to migrate automatically.
@@ -952,7 +963,11 @@ const instance_script = {
 			const reassigned_bindings = bindings.filter((b) => b?.reassigned);
 
 			if (
-				reassigned_bindings.length === 0 &&
+				// on version 5.25.0 deriveds are writable so we can use them even if
+				// reassigned (but if the right side is a literal we want to use `$state`)
+				(support_writable_derived
+					? node.body.expression.right.type !== 'Literal'
+					: reassigned_bindings.length === 0) &&
 				!bindings.some((b) => b?.kind === 'store_sub') &&
 				node.body.expression.left.type !== 'MemberExpression'
 			) {
diff --git a/packages/svelte/tests/migrate/samples/reassigned-deriveds/input.svelte b/packages/svelte/tests/migrate/samples/reassigned-deriveds/input.svelte
new file mode 100644
index 0000000000..024f719fb9
--- /dev/null
+++ b/packages/svelte/tests/migrate/samples/reassigned-deriveds/input.svelte
@@ -0,0 +1,10 @@
+<script>
+	let name = 'world';
+
+	$: upper = name.toUpperCase();
+</script>
+
+<input bind:value={name} />
+<input bind:value={upper} />
+
+{upper}
\ No newline at end of file
diff --git a/packages/svelte/tests/migrate/samples/reassigned-deriveds/output.svelte b/packages/svelte/tests/migrate/samples/reassigned-deriveds/output.svelte
new file mode 100644
index 0000000000..0903299d95
--- /dev/null
+++ b/packages/svelte/tests/migrate/samples/reassigned-deriveds/output.svelte
@@ -0,0 +1,10 @@
+<script>
+	let name = $state('world');
+
+	let upper = $derived(name.toUpperCase());
+</script>
+
+<input bind:value={name} />
+<input bind:value={upper} />
+
+{upper}
\ No newline at end of file

From 78d238c5a34396afcc9edf02bb767d0936440ad9 Mon Sep 17 00:00:00 2001
From: Paolo Ricciuti <ricciutipaolo@gmail.com>
Date: Sat, 22 Mar 2025 00:03:38 +0100
Subject: [PATCH 20/23] chore: revert version check in migrate (#15583)

---
 packages/svelte/src/compiler/migrate/index.js | 17 +----------------
 1 file changed, 1 insertion(+), 16 deletions(-)

diff --git a/packages/svelte/src/compiler/migrate/index.js b/packages/svelte/src/compiler/migrate/index.js
index b336ebb2b8..9d79d88b23 100644
--- a/packages/svelte/src/compiler/migrate/index.js
+++ b/packages/svelte/src/compiler/migrate/index.js
@@ -19,7 +19,6 @@ import { migrate_svelte_ignore } from '../utils/extract_svelte_ignore.js';
 import { validate_component_options } from '../validate-options.js';
 import { is_reserved, is_svg, is_void } from '../../utils.js';
 import { regex_is_valid_identifier } from '../phases/patterns.js';
-import { VERSION } from 'svelte/compiler';
 
 const regex_style_tags = /(<style[^>]+>)([\S\s]*?)(<\/style>)/g;
 const style_placeholder = '/*$$__STYLE_CONTENT__$$*/';
@@ -114,16 +113,6 @@ function find_closing_parenthesis(start, code) {
 	return end;
 }
 
-function check_support_writable_deriveds() {
-	const [major, minor, patch] = VERSION.split('.');
-
-	if (+major < 5) return false;
-	if (+minor < 25) return false;
-	return true;
-}
-
-const support_writable_derived = check_support_writable_deriveds();
-
 /**
  * Does a best-effort migration of Svelte code towards using runes, event attributes and render tags.
  * May throw an error if the code is too complex to migrate automatically.
@@ -963,11 +952,7 @@ const instance_script = {
 			const reassigned_bindings = bindings.filter((b) => b?.reassigned);
 
 			if (
-				// on version 5.25.0 deriveds are writable so we can use them even if
-				// reassigned (but if the right side is a literal we want to use `$state`)
-				(support_writable_derived
-					? node.body.expression.right.type !== 'Literal'
-					: reassigned_bindings.length === 0) &&
+				node.body.expression.right.type !== 'Literal' &&
 				!bindings.some((b) => b?.kind === 'store_sub') &&
 				node.body.expression.left.type !== 'MemberExpression'
 			) {

From 7fe9bf524bbf060a0acf8b91c8ca322b105423b4 Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Sat, 22 Mar 2025 00:04:01 +0100
Subject: [PATCH 21/23] Version Packages (#15582)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 .changeset/forty-snakes-lay.md | 5 -----
 packages/svelte/CHANGELOG.md   | 6 ++++++
 packages/svelte/package.json   | 2 +-
 packages/svelte/src/version.js | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)
 delete mode 100644 .changeset/forty-snakes-lay.md

diff --git a/.changeset/forty-snakes-lay.md b/.changeset/forty-snakes-lay.md
deleted file mode 100644
index 6cb4c2d761..0000000000
--- a/.changeset/forty-snakes-lay.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-feat: migrate reassigned deriveds to `$derived`
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index 9e99e91b8e..86e1179029 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,11 @@
 # svelte
 
+## 5.25.2
+
+### Patch Changes
+
+- feat: migrate reassigned deriveds to `$derived` ([#15581](https://github.com/sveltejs/svelte/pull/15581))
+
 ## 5.25.1
 
 ### Patch Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index 9d3902696d..56fa949391 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": "5.25.1",
+  "version": "5.25.2",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index a4f5a15c8f..e2dc6c2c09 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 = '5.25.1';
+export const VERSION = '5.25.2';
 export const PUBLIC_VERSION = '5';

From 3080c1334e8efc65756488c0cc36b6dec5fca00f Mon Sep 17 00:00:00 2001
From: Paolo Ricciuti <ricciutipaolo@gmail.com>
Date: Sat, 22 Mar 2025 01:56:31 +0100
Subject: [PATCH 22/23] fix: prevent state runes from being called with spread
 (#15585)

* fix: prevent state runes from being called with spread

* prevent spread arguments for all runes except $inspect

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>
---
 .changeset/nice-pianos-punch.md                    |  5 +++++
 .../docs/98-reference/.generated/compile-errors.md |  6 ++++++
 packages/svelte/messages/compile-errors/script.md  |  4 ++++
 packages/svelte/src/compiler/errors.js             | 10 ++++++++++
 .../phases/2-analyze/visitors/CallExpression.js    |  8 ++++++++
 .../rune-invalid-spread-derived-by/errors.json     | 14 ++++++++++++++
 .../rune-invalid-spread-derived-by/input.svelte    |  4 ++++
 .../rune-invalid-spread-derived/errors.json        | 14 ++++++++++++++
 .../rune-invalid-spread-derived/input.svelte       |  4 ++++
 .../rune-invalid-spread-state-raw/errors.json      | 14 ++++++++++++++
 .../rune-invalid-spread-state-raw/input.svelte     |  4 ++++
 .../samples/rune-invalid-spread-state/errors.json  | 14 ++++++++++++++
 .../samples/rune-invalid-spread-state/input.svelte |  4 ++++
 13 files changed, 105 insertions(+)
 create mode 100644 .changeset/nice-pianos-punch.md
 create mode 100644 packages/svelte/tests/validator/samples/rune-invalid-spread-derived-by/errors.json
 create mode 100644 packages/svelte/tests/validator/samples/rune-invalid-spread-derived-by/input.svelte
 create mode 100644 packages/svelte/tests/validator/samples/rune-invalid-spread-derived/errors.json
 create mode 100644 packages/svelte/tests/validator/samples/rune-invalid-spread-derived/input.svelte
 create mode 100644 packages/svelte/tests/validator/samples/rune-invalid-spread-state-raw/errors.json
 create mode 100644 packages/svelte/tests/validator/samples/rune-invalid-spread-state-raw/input.svelte
 create mode 100644 packages/svelte/tests/validator/samples/rune-invalid-spread-state/errors.json
 create mode 100644 packages/svelte/tests/validator/samples/rune-invalid-spread-state/input.svelte

diff --git a/.changeset/nice-pianos-punch.md b/.changeset/nice-pianos-punch.md
new file mode 100644
index 0000000000..f70af9eb04
--- /dev/null
+++ b/.changeset/nice-pianos-punch.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: prevent state runes from being called with spread
diff --git a/documentation/docs/98-reference/.generated/compile-errors.md b/documentation/docs/98-reference/.generated/compile-errors.md
index ea116014e7..a8c39aaf97 100644
--- a/documentation/docs/98-reference/.generated/compile-errors.md
+++ b/documentation/docs/98-reference/.generated/compile-errors.md
@@ -660,6 +660,12 @@ Cannot access a computed property of a rune
 `%name%` is not a valid rune
 ```
 
+### rune_invalid_spread
+
+```
+`%rune%` cannot be called with a spread argument
+```
+
 ### rune_invalid_usage
 
 ```
diff --git a/packages/svelte/messages/compile-errors/script.md b/packages/svelte/messages/compile-errors/script.md
index 795c0b007d..aabcbeae48 100644
--- a/packages/svelte/messages/compile-errors/script.md
+++ b/packages/svelte/messages/compile-errors/script.md
@@ -162,6 +162,10 @@ This turned out to be buggy and unpredictable, particularly when working with de
 
 > `%name%` is not a valid rune
 
+## rune_invalid_spread
+
+> `%rune%` cannot be called with a spread argument
+
 ## rune_invalid_usage
 
 > Cannot use `%rune%` rune in non-runes mode
diff --git a/packages/svelte/src/compiler/errors.js b/packages/svelte/src/compiler/errors.js
index 677b99fcff..6bf973948b 100644
--- a/packages/svelte/src/compiler/errors.js
+++ b/packages/svelte/src/compiler/errors.js
@@ -383,6 +383,16 @@ export function rune_invalid_name(node, name) {
 	e(node, 'rune_invalid_name', `\`${name}\` is not a valid rune\nhttps://svelte.dev/e/rune_invalid_name`);
 }
 
+/**
+ * `%rune%` cannot be called with a spread argument
+ * @param {null | number | NodeLike} node
+ * @param {string} rune
+ * @returns {never}
+ */
+export function rune_invalid_spread(node, rune) {
+	e(node, 'rune_invalid_spread', `\`${rune}\` cannot be called with a spread argument\nhttps://svelte.dev/e/rune_invalid_spread`);
+}
+
 /**
  * Cannot use `%rune%` rune in non-runes mode
  * @param {null | number | NodeLike} node
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
index 6ef323725b..2eac934b33 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
@@ -17,6 +17,14 @@ export function CallExpression(node, context) {
 
 	const rune = get_rune(node, context.state.scope);
 
+	if (rune && rune !== '$inspect') {
+		for (const arg of node.arguments) {
+			if (arg.type === 'SpreadElement') {
+				e.rune_invalid_spread(node, rune);
+			}
+		}
+	}
+
 	switch (rune) {
 		case null:
 			if (!is_safe_identifier(node.callee, context.state.scope)) {
diff --git a/packages/svelte/tests/validator/samples/rune-invalid-spread-derived-by/errors.json b/packages/svelte/tests/validator/samples/rune-invalid-spread-derived-by/errors.json
new file mode 100644
index 0000000000..be59da95fa
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/rune-invalid-spread-derived-by/errors.json
@@ -0,0 +1,14 @@
+[
+	{
+		"code": "rune_invalid_spread",
+		"end": {
+			"column": 35,
+			"line": 3
+		},
+		"message": "`$derived.by` cannot be called with a spread argument",
+		"start": {
+			"column": 15,
+			"line": 3
+		}
+	}
+]
diff --git a/packages/svelte/tests/validator/samples/rune-invalid-spread-derived-by/input.svelte b/packages/svelte/tests/validator/samples/rune-invalid-spread-derived-by/input.svelte
new file mode 100644
index 0000000000..49e8057aa5
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/rune-invalid-spread-derived-by/input.svelte
@@ -0,0 +1,4 @@
+<script>
+	const args = [0];
+	const count = $derived.by(...args);
+</script>
\ No newline at end of file
diff --git a/packages/svelte/tests/validator/samples/rune-invalid-spread-derived/errors.json b/packages/svelte/tests/validator/samples/rune-invalid-spread-derived/errors.json
new file mode 100644
index 0000000000..6a333bc362
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/rune-invalid-spread-derived/errors.json
@@ -0,0 +1,14 @@
+[
+	{
+		"code": "rune_invalid_spread",
+		"end": {
+			"column": 32,
+			"line": 3
+		},
+		"message": "`$derived` cannot be called with a spread argument",
+		"start": {
+			"column": 15,
+			"line": 3
+		}
+	}
+]
diff --git a/packages/svelte/tests/validator/samples/rune-invalid-spread-derived/input.svelte b/packages/svelte/tests/validator/samples/rune-invalid-spread-derived/input.svelte
new file mode 100644
index 0000000000..9155493e17
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/rune-invalid-spread-derived/input.svelte
@@ -0,0 +1,4 @@
+<script>
+	const args = [0];
+	const count = $derived(...args);
+</script>
\ No newline at end of file
diff --git a/packages/svelte/tests/validator/samples/rune-invalid-spread-state-raw/errors.json b/packages/svelte/tests/validator/samples/rune-invalid-spread-state-raw/errors.json
new file mode 100644
index 0000000000..e08b498fcb
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/rune-invalid-spread-state-raw/errors.json
@@ -0,0 +1,14 @@
+[
+	{
+		"code": "rune_invalid_spread",
+		"end": {
+			"column": 34,
+			"line": 3
+		},
+		"message": "`$state.raw` cannot be called with a spread argument",
+		"start": {
+			"column": 15,
+			"line": 3
+		}
+	}
+]
diff --git a/packages/svelte/tests/validator/samples/rune-invalid-spread-state-raw/input.svelte b/packages/svelte/tests/validator/samples/rune-invalid-spread-state-raw/input.svelte
new file mode 100644
index 0000000000..d06fb053b3
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/rune-invalid-spread-state-raw/input.svelte
@@ -0,0 +1,4 @@
+<script>
+	const args = [0];
+	const count = $state.raw(...args);
+</script>
\ No newline at end of file
diff --git a/packages/svelte/tests/validator/samples/rune-invalid-spread-state/errors.json b/packages/svelte/tests/validator/samples/rune-invalid-spread-state/errors.json
new file mode 100644
index 0000000000..11ae2abce5
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/rune-invalid-spread-state/errors.json
@@ -0,0 +1,14 @@
+[
+	{
+		"code": "rune_invalid_spread",
+		"end": {
+			"column": 30,
+			"line": 3
+		},
+		"message": "`$state` cannot be called with a spread argument",
+		"start": {
+			"column": 15,
+			"line": 3
+		}
+	}
+]
diff --git a/packages/svelte/tests/validator/samples/rune-invalid-spread-state/input.svelte b/packages/svelte/tests/validator/samples/rune-invalid-spread-state/input.svelte
new file mode 100644
index 0000000000..02feac893f
--- /dev/null
+++ b/packages/svelte/tests/validator/samples/rune-invalid-spread-state/input.svelte
@@ -0,0 +1,4 @@
+<script>
+	const args = [0];
+	const count = $state(...args);
+</script>
\ No newline at end of file

From f498a21063894e6e515e62d753396410624b2e0f Mon Sep 17 00:00:00 2001
From: "github-actions[bot]"
 <41898282+github-actions[bot]@users.noreply.github.com>
Date: Sun, 23 Mar 2025 09:59:21 -0400
Subject: [PATCH 23/23] Version Packages (#15587)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
---
 .changeset/nice-pianos-punch.md | 5 -----
 packages/svelte/CHANGELOG.md    | 6 ++++++
 packages/svelte/package.json    | 2 +-
 packages/svelte/src/version.js  | 2 +-
 4 files changed, 8 insertions(+), 7 deletions(-)
 delete mode 100644 .changeset/nice-pianos-punch.md

diff --git a/.changeset/nice-pianos-punch.md b/.changeset/nice-pianos-punch.md
deleted file mode 100644
index f70af9eb04..0000000000
--- a/.changeset/nice-pianos-punch.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: prevent state runes from being called with spread
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index 86e1179029..e6b5de7e5f 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,11 @@
 # svelte
 
+## 5.25.3
+
+### Patch Changes
+
+- fix: prevent state runes from being called with spread ([#15585](https://github.com/sveltejs/svelte/pull/15585))
+
 ## 5.25.2
 
 ### Patch Changes
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index 56fa949391..0410520634 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": "5.25.2",
+  "version": "5.25.3",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index e2dc6c2c09..e4ae33a9b1 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 = '5.25.2';
+export const VERSION = '5.25.3';
 export const PUBLIC_VERSION = '5';