diff --git a/.changeset/easy-singers-retire.md b/.changeset/easy-singers-retire.md
deleted file mode 100644
index 4420286e13..0000000000
--- a/.changeset/easy-singers-retire.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: don't rebase just-created batches
diff --git a/.changeset/flat-shrimps-worry.md b/.changeset/flat-shrimps-worry.md
deleted file mode 100644
index a5f76a0f9d..0000000000
--- a/.changeset/flat-shrimps-worry.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: flush eager effects in production
diff --git a/.changeset/full-waves-tease.md b/.changeset/full-waves-tease.md
deleted file mode 100644
index 3915334bf7..0000000000
--- a/.changeset/full-waves-tease.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: account for proxified instance when updating `bind:this`
diff --git a/.changeset/many-pandas-add.md b/.changeset/many-pandas-add.md
deleted file mode 100644
index 85de7acb35..0000000000
--- a/.changeset/many-pandas-add.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: ensure scheduled batch is flushed if not obsolete
diff --git a/.changeset/modern-tables-fetch.md b/.changeset/modern-tables-fetch.md
deleted file mode 100644
index 89543910fa..0000000000
--- a/.changeset/modern-tables-fetch.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: resolve stale deriveds with latest value
diff --git a/.changeset/slow-bikes-serve.md b/.changeset/slow-bikes-serve.md
new file mode 100644
index 0000000000..5e1d654353
--- /dev/null
+++ b/.changeset/slow-bikes-serve.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: inline primitive constants in attribute values during SSR
diff --git a/.changeset/small-tools-walk.md b/.changeset/small-tools-walk.md
deleted file mode 100644
index 2b275368b3..0000000000
--- a/.changeset/small-tools-walk.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: allow `@debug` tags to reference awaited variables
diff --git a/.changeset/smooth-poems-tap.md b/.changeset/smooth-poems-tap.md
deleted file mode 100644
index ac160656cf..0000000000
--- a/.changeset/smooth-poems-tap.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: re-run fallback props if dependencies update
diff --git a/.changeset/three-pears-build.md b/.changeset/three-pears-build.md
deleted file mode 100644
index 8a638149a3..0000000000
--- a/.changeset/three-pears-build.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: ignore comments when reading CSS values
diff --git a/.changeset/twelve-cooks-speak.md b/.changeset/twelve-cooks-speak.md
deleted file mode 100644
index d4fcd5c339..0000000000
--- a/.changeset/twelve-cooks-speak.md
+++ /dev/null
@@ -1,5 +0,0 @@
----
-'svelte': patch
----
-
-fix: ignore false-positive errors of `$inspect` dependencies
diff --git a/documentation/docs/06-runtime/02-context.md b/documentation/docs/06-runtime/02-context.md
index aee51c9a78..439272df8f 100644
--- a/documentation/docs/06-runtime/02-context.md
+++ b/documentation/docs/06-runtime/02-context.md
@@ -163,6 +163,8 @@ export const [getCounter, setCounter] = createContext<Counter>();
 
 Svelte will warn you if you get it wrong.
 
+Similarly, to pass primitive values through context, use functions as described in [Passing state into functions]($state#Passing-state-into-functions).
+
 ## Component testing
 
 When writing [component tests](testing#Unit-and-component-tests-with-Vitest-Component-testing), it can be useful to create a wrapper component that sets the context in order to check the behaviour of a component that uses it. As of version 5.49, you can do this sort of thing:
diff --git a/packages/svelte/CHANGELOG.md b/packages/svelte/CHANGELOG.md
index 8e0f8a0916..36528c741b 100644
--- a/packages/svelte/CHANGELOG.md
+++ b/packages/svelte/CHANGELOG.md
@@ -1,5 +1,77 @@
 # svelte
 
+## 5.55.8
+
+### Patch Changes
+
+- fix(print): handle `svelte:body` and fix keyframe percentage double-printing ([#18234](https://github.com/sveltejs/svelte/pull/18234))
+
+- fix: execute uninitialized derived even if it's destroyed ([#18228](https://github.com/sveltejs/svelte/pull/18228))
+
+- fix: use named symbols everywhere ([#18238](https://github.com/sveltejs/svelte/pull/18238))
+
+- fix: don't run teardown effects when deriveds are unfreezed ([#18227](https://github.com/sveltejs/svelte/pull/18227))
+
+- fix: unset context synchronously in `run` ([#18236](https://github.com/sveltejs/svelte/pull/18236))
+
+## 5.55.7
+
+### Patch Changes
+
+- fix: prevent XSS on `hydratable` from user contents ([`a16ebc67bbcf8f708360195687e1b2719463e1a4`](https://github.com/sveltejs/svelte/commit/a16ebc67bbcf8f708360195687e1b2719463e1a4))
+
+- chore: bump devalue ([#18219](https://github.com/sveltejs/svelte/pull/18219))
+
+- fix: disallow empty attribute names during SSR ([`547853e2406a2147ad7fb5ffeba95b01bd9642da`](https://github.com/sveltejs/svelte/commit/547853e2406a2147ad7fb5ffeba95b01bd9642da))
+
+- fix: harden regex ([`d2375e2ebcab5c88feb5652f1a9d621b8f06b259`](https://github.com/sveltejs/svelte/commit/d2375e2ebcab5c88feb5652f1a9d621b8f06b259))
+
+- fix: move Svelte runtime properties to symbols ([`e1cbbd96441e82c9eb8a23a2903c0d06d3cda991`](https://github.com/sveltejs/svelte/commit/e1cbbd96441e82c9eb8a23a2903c0d06d3cda991))
+
+## 5.55.6
+
+### Patch Changes
+
+- fix: leave stale promises to wait for a later resolution, instead of rejecting ([#18180](https://github.com/sveltejs/svelte/pull/18180))
+
+- fix: keep dependencies of `$state.eager/pending` ([#18218](https://github.com/sveltejs/svelte/pull/18218))
+
+- fix: reapply context after transforming error during SSR ([#18099](https://github.com/sveltejs/svelte/pull/18099))
+
+- fix: don't rebase just-created batches ([#18117](https://github.com/sveltejs/svelte/pull/18117))
+
+- chore: allow `null` for `pending` in typings ([#18201](https://github.com/sveltejs/svelte/pull/18201))
+
+- fix: flush eager effects in production ([#18107](https://github.com/sveltejs/svelte/pull/18107))
+
+- fix: rethrow error of failed iterable after calling `return()` ([#18169](https://github.com/sveltejs/svelte/pull/18169))
+
+- fix: account for proxified instance when updating `bind:this` ([#18147](https://github.com/sveltejs/svelte/pull/18147))
+
+- fix: ensure scheduled batch is flushed if not obsolete ([#18131](https://github.com/sveltejs/svelte/pull/18131))
+
+- fix: resolve stale deriveds with latest value ([#18167](https://github.com/sveltejs/svelte/pull/18167))
+
+- chore: remove unnecessary `increment_pending` calls ([#18183](https://github.com/sveltejs/svelte/pull/18183))
+
+- fix: correctly compile component member expressions for SSR ([#18192](https://github.com/sveltejs/svelte/pull/18192))
+
+- fix: reset `source.updated` stack traces after `flush` ([#18196](https://github.com/sveltejs/svelte/pull/18196))
+
+- fix: replacing async 'blocking' strategy with 'merging' ([#18205](https://github.com/sveltejs/svelte/pull/18205))
+
+- fix: allow `@debug` tags to reference awaited variables ([#18138](https://github.com/sveltejs/svelte/pull/18138))
+
+- fix: re-run fallback props if dependencies update ([#18146](https://github.com/sveltejs/svelte/pull/18146))
+
+- fix: abort running obsolete async branches ([#18118](https://github.com/sveltejs/svelte/pull/18118))
+
+- fix: ignore comments when reading CSS values ([#18153](https://github.com/sveltejs/svelte/pull/18153))
+
+- fix: wrap `Promise.all` in `save` during SSR ([#18178](https://github.com/sveltejs/svelte/pull/18178))
+
+- fix: ignore false-positive errors of `$inspect` dependencies ([#18106](https://github.com/sveltejs/svelte/pull/18106))
+
 ## 5.55.5
 
 ### Patch Changes
diff --git a/packages/svelte/elements.d.ts b/packages/svelte/elements.d.ts
index ad5815facd..a19c8c28d0 100644
--- a/packages/svelte/elements.d.ts
+++ b/packages/svelte/elements.d.ts
@@ -2067,9 +2067,9 @@ export interface SvelteHTMLElements {
 	};
 	'svelte:head': { [name: string]: any };
 	'svelte:boundary': {
-		onerror?: (error: unknown, reset: () => void) => void;
-		failed?: import('svelte').Snippet<[error: unknown, reset: () => void]>;
-		pending?: import('svelte').Snippet;
+		onerror?: ((error: unknown, reset: () => void) => void) | null | undefined;
+		failed?: import('svelte').Snippet<[error: unknown, reset: () => void]> | null | undefined;
+		pending?: import('svelte').Snippet | null | undefined;
 	};
 
 	[name: string]: { [name: string]: any };
diff --git a/packages/svelte/package.json b/packages/svelte/package.json
index a4ae208913..66a555880b 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": "5.55.5",
+  "version": "5.55.8",
   "type": "module",
   "types": "./types/index.d.ts",
   "engines": {
@@ -176,7 +176,7 @@
     "aria-query": "5.3.1",
     "axobject-query": "^4.1.0",
     "clsx": "^2.1.1",
-    "devalue": "^5.6.4",
+    "devalue": "^5.8.1",
     "esm-env": "^1.2.1",
     "esrap": "^2.2.4",
     "is-reference": "^3.0.3",
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/Component.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/Component.js
index 8e7d7bcdbf..ed202edd3b 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/Component.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/Component.js
@@ -9,5 +9,9 @@ import { build_inline_component } from './shared/component.js';
  * @param {ComponentContext} context
  */
 export function Component(node, context) {
-	build_inline_component(node, /** @type {Expression} */ (context.visit(b.id(node.name))), context);
+	build_inline_component(
+		node,
+		/** @type {Expression} */ (context.visit(b.member_id(node.name))),
+		context
+	);
 }
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/utils.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/utils.js
index a87642bc4c..62e1c44094 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/utils.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/utils.js
@@ -12,7 +12,7 @@ import {
 import * as b from '#compiler/builders';
 import { sanitize_template_string } from '../../../../../utils/sanitize_template_string.js';
 import { regex_whitespaces_strict } from '../../../../patterns.js';
-import { has_await_expression } from '../../../../../utils/ast.js';
+import { has_await_expression, save } from '../../../../../utils/ast.js';
 import { ExpressionMetadata } from '../../../../nodes.js';
 
 /** Opens an if/each block, so that we can remove nodes in the case of a mismatch */
@@ -229,18 +229,25 @@ export function build_attribute_value(
 				? node.data.replace(regex_whitespaces_strict, ' ')
 				: node.data;
 		} else {
-			expressions.push(
-				b.call(
-					'$.stringify',
-					transform(
-						/** @type {Expression} */ (context.visit(node.expression)),
-						node.metadata.expression
-					)
-				)
-			);
+			const evaluated = context.state.scope.evaluate(node.expression);
 
-			quasi = b.quasi('', i + 1 === value.length);
-			quasis.push(quasi);
+			if (evaluated.is_known) {
+				quasi.value.cooked += (evaluated.value ?? '') + '';
+			} else {
+				const expression = transform(
+					/** @type {Expression} */ (context.visit(node.expression)),
+					node.metadata.expression
+				);
+
+				expressions.push(
+					evaluated.is_string && evaluated.is_defined
+						? expression
+						: b.call('$.stringify', expression)
+				);
+
+				quasi = b.quasi('', i + 1 === value.length);
+				quasis.push(quasi);
+			}
 		}
 	}
 
@@ -248,7 +255,9 @@ export function build_attribute_value(
 		quasi.value.raw = sanitize_template_string(/** @type {string} */ (quasi.value.cooked));
 	}
 
-	return b.template(quasis, expressions);
+	return expressions.length > 0
+		? b.template(quasis, expressions)
+		: b.literal(/** @type {string} */ (quasi.value.cooked));
 }
 
 /**
@@ -360,7 +369,7 @@ export class PromiseOptimiser {
 
 		return b.const(
 			b.array_pattern(this.expressions.map((_, i) => b.id(`$$${i}`))),
-			b.await(b.call('Promise.all', promises))
+			save(b.call('Promise.all', promises))
 		);
 	}
 
diff --git a/packages/svelte/src/compiler/print/index.js b/packages/svelte/src/compiler/print/index.js
index 26dc1b88e8..c511ee6da0 100644
--- a/packages/svelte/src/compiler/print/index.js
+++ b/packages/svelte/src/compiler/print/index.js
@@ -247,7 +247,7 @@ const css_visitors = {
 	},
 
 	Percentage(node, context) {
-		context.write(`${node.value}%`);
+		context.write(node.value);
 	},
 
 	PseudoClassSelector(node, context) {
@@ -417,6 +417,7 @@ const svelte_visitors = (comments) => ({
 				const is_block_element =
 					child_node.type === 'RegularElement' ||
 					child_node.type === 'Component' ||
+					child_node.type === 'SvelteBody' ||
 					child_node.type === 'SvelteHead' ||
 					child_node.type === 'SvelteFragment' ||
 					child_node.type === 'SvelteBoundary' ||
@@ -821,6 +822,10 @@ const svelte_visitors = (comments) => ({
 		context.write('</style>');
 	},
 
+	SvelteBody(node, context) {
+		base_element(node, context, comments);
+	},
+
 	SvelteBoundary(node, context) {
 		base_element(node, context, comments);
 	},
diff --git a/packages/svelte/src/constants.js b/packages/svelte/src/constants.js
index a3a109b943..1e721b7d30 100644
--- a/packages/svelte/src/constants.js
+++ b/packages/svelte/src/constants.js
@@ -32,7 +32,7 @@ export const ELEMENT_IS_NAMESPACED = 1;
 export const ELEMENT_PRESERVE_ATTRIBUTE_CASE = 1 << 1;
 export const ELEMENT_IS_INPUT = 1 << 2;
 
-export const UNINITIALIZED = Symbol();
+export const UNINITIALIZED = Symbol('uninitialized');
 
 // Dev-time component properties
 export const FILENAME = Symbol('filename');
diff --git a/packages/svelte/src/internal/client/constants.js b/packages/svelte/src/internal/client/constants.js
index f92fba73be..043b50b4b2 100644
--- a/packages/svelte/src/internal/client/constants.js
+++ b/packages/svelte/src/internal/client/constants.js
@@ -63,6 +63,11 @@ export const STATE_SYMBOL = Symbol('$state');
 export const LEGACY_PROPS = Symbol('legacy props');
 export const LOADING_ATTR_SYMBOL = Symbol('');
 export const PROXY_PATH_SYMBOL = Symbol('proxy path');
+export const ATTRIBUTES_CACHE = Symbol('attributes');
+export const CLASS_CACHE = Symbol('class');
+export const STYLE_CACHE = Symbol('style');
+export const TEXT_CACHE = Symbol('text');
+export const FORM_RESET_HANDLER = Symbol('form reset');
 /** An anchor might change, via this symbol on the original anchor we can tell HMR about the updated anchor */
 export const HMR_ANCHOR = Symbol('hmr anchor');
 
diff --git a/packages/svelte/src/internal/client/dom/blocks/async.js b/packages/svelte/src/internal/client/dom/blocks/async.js
index 43af3d8dd3..170529a6b9 100644
--- a/packages/svelte/src/internal/client/dom/blocks/async.js
+++ b/packages/svelte/src/internal/client/dom/blocks/async.js
@@ -1,5 +1,5 @@
 /** @import { Blocker, TemplateNode, Value } from '#client' */
-import { flatten, increment_pending } from '../../reactivity/async.js';
+import { flatten } from '../../reactivity/async.js';
 import { get } from '../../runtime.js';
 import {
 	hydrate_next,
@@ -42,8 +42,6 @@ export function async(node, blockers = [], expressions = [], fn) {
 		return;
 	}
 
-	const decrement_pending = increment_pending();
-
 	if (was_hydrating) {
 		var previous_hydrate_node = hydrate_node;
 		set_hydrate_node(end);
@@ -64,8 +62,6 @@ export function async(node, blockers = [], expressions = [], fn) {
 			if (was_hydrating) {
 				set_hydrating(false);
 			}
-
-			decrement_pending();
 		}
 	});
 }
diff --git a/packages/svelte/src/internal/client/dom/blocks/boundary.js b/packages/svelte/src/internal/client/dom/blocks/boundary.js
index 028b82ab92..beaa7d6869 100644
--- a/packages/svelte/src/internal/client/dom/blocks/boundary.js
+++ b/packages/svelte/src/internal/client/dom/blocks/boundary.js
@@ -35,19 +35,18 @@ import { queue_micro_task } from '../task.js';
 import * as e from '../../errors.js';
 import * as w from '../../warnings.js';
 import { DEV } from 'esm-env';
-import { Batch, current_batch, previous_batch, schedule_effect } from '../../reactivity/batch.js';
+import { Batch, current_batch } from '../../reactivity/batch.js';
 import { internal_set, source } from '../../reactivity/sources.js';
 import { tag } from '../../dev/tracing.js';
 import { createSubscriber } from '../../../../reactivity/create-subscriber.js';
 import { create_text } from '../operations.js';
 import { defer_effect } from '../../reactivity/utils.js';
-import { set_signal_status } from '../../reactivity/status.js';
 
 /**
  * @typedef {{
- * 	 onerror?: (error: unknown, reset: () => void) => void;
- *   failed?: (anchor: Node, error: () => unknown, reset: () => () => void) => void;
- *   pending?: (anchor: Node) => void;
+ * 	 onerror?: ((error: unknown, reset: () => void) => void) | null;
+ *   failed?: ((anchor: Node, error: () => unknown, reset: () => () => void) => void) | null;
+ *   pending?: ((anchor: Node) => void) | null;
  * }} BoundaryProps
  */
 
diff --git a/packages/svelte/src/internal/client/dom/blocks/svelte-head.js b/packages/svelte/src/internal/client/dom/blocks/svelte-head.js
index 7cab6c3385..5721f7b056 100644
--- a/packages/svelte/src/internal/client/dom/blocks/svelte-head.js
+++ b/packages/svelte/src/internal/client/dom/blocks/svelte-head.js
@@ -1,8 +1,8 @@
 /** @import { TemplateNode } from '#client' */
 import { hydrate_node, hydrating, set_hydrate_node, set_hydrating } from '../hydration.js';
 import { create_text, get_first_child, get_next_sibling } from '../operations.js';
-import { block } from '../../reactivity/effects.js';
-import { COMMENT_NODE, EFFECT_PRESERVED, HEAD_EFFECT } from '#client/constants';
+import { block, branch } from '../../reactivity/effects.js';
+import { COMMENT_NODE, HEAD_EFFECT } from '#client/constants';
 
 /**
  * @param {string} hash
@@ -49,9 +49,10 @@ export function head(hash, render_fn) {
 	}
 
 	try {
-		// normally a branch is the child of a block and would have the EFFECT_PRESERVED flag,
-		// but since head blocks don't necessarily only have direct branch children we add it on the block itself
-		block(() => render_fn(anchor), HEAD_EFFECT | EFFECT_PRESERVED);
+		block(() => {
+			var e = branch(() => render_fn(anchor));
+			e.f |= HEAD_EFFECT;
+		});
 	} finally {
 		if (was_hydrating) {
 			set_hydrating(true);
diff --git a/packages/svelte/src/internal/client/dom/elements/attributes.js b/packages/svelte/src/internal/client/dom/elements/attributes.js
index 0cec01191a..a193a70dd5 100644
--- a/packages/svelte/src/internal/client/dom/elements/attributes.js
+++ b/packages/svelte/src/internal/client/dom/elements/attributes.js
@@ -5,7 +5,12 @@ import { get_descriptors, get_prototype_of } from '../../../shared/utils.js';
 import { create_event, delegate, delegated, event, event_symbol } from './events.js';
 import { add_form_reset_listener, autofocus } from './misc.js';
 import * as w from '../../warnings.js';
-import { IS_XHTML, LOADING_ATTR_SYMBOL } from '#client/constants';
+import {
+	ATTRIBUTES_CACHE,
+	FORM_RESET_HANDLER,
+	IS_XHTML,
+	LOADING_ATTR_SYMBOL
+} from '#client/constants';
 import { queue_micro_task } from '../task.js';
 import { is_capture_event, can_delegate_event, normalize_attribute } from '../../../../utils.js';
 import {
@@ -69,8 +74,7 @@ export function remove_input_defaults(input) {
 		}
 	};
 
-	// @ts-expect-error
-	input.__on_r = remove_defaults;
+	/** @type {any} */ (input)[FORM_RESET_HANDLER] = remove_defaults;
 	queue_micro_task(remove_defaults);
 	add_form_reset_listener();
 }
@@ -561,8 +565,7 @@ export function attribute_effect(
  */
 function get_attributes(element) {
 	return /** @type {Record<string | symbol, unknown>} **/ (
-		// @ts-expect-error
-		element.__attributes ??= {
+		/** @type {any} */ (element)[ATTRIBUTES_CACHE] ??= {
 			[IS_CUSTOM_ELEMENT]: element.nodeName.includes('-'),
 			[IS_HTML]: element.namespaceURI === NAMESPACE_HTML
 		}
@@ -583,13 +586,19 @@ function get_setters(element) {
 	var proto = element; // In the case of custom elements there might be setters on the instance
 	var element_proto = Element.prototype;
 
-	// Stop at Element, from there on there's only unnecessary setters we're not interested in
+	// Stop at Element, from there on there's only unnecessary (and dangerous, like innerHTML) setters we're not interested in
 	// Do not use constructor.name here as that's unreliable in some browser environments
 	while (element_proto !== proto) {
 		descriptors = get_descriptors(proto);
 
 		for (var key in descriptors) {
-			if (descriptors[key].set) {
+			if (
+				descriptors[key].set &&
+				// better safe than sorry, we don't want spread attributes to mess with HTML content
+				key !== 'innerHTML' &&
+				key !== 'textContent' &&
+				key !== 'innerText'
+			) {
 				setters.push(key);
 			}
 		}
diff --git a/packages/svelte/src/internal/client/dom/elements/bindings/shared.js b/packages/svelte/src/internal/client/dom/elements/bindings/shared.js
index aa083776a5..303890adec 100644
--- a/packages/svelte/src/internal/client/dom/elements/bindings/shared.js
+++ b/packages/svelte/src/internal/client/dom/elements/bindings/shared.js
@@ -5,6 +5,7 @@ import {
 	set_active_effect,
 	set_active_reaction
 } from '../../../runtime.js';
+import { FORM_RESET_HANDLER } from '../../../constants.js';
 import { add_form_reset_listener } from '../misc.js';
 
 /**
@@ -58,18 +59,15 @@ export function without_reactive_context(fn) {
  */
 export function listen_to_event_and_reset_event(element, event, handler, on_reset = handler) {
 	element.addEventListener(event, () => without_reactive_context(handler));
-	// @ts-expect-error
-	const prev = element.__on_r;
+	const prev = /** @type {any} */ (element)[FORM_RESET_HANDLER];
 	if (prev) {
 		// special case for checkbox that can have multiple binds (group & checked)
-		// @ts-expect-error
-		element.__on_r = () => {
+		/** @type {any} */ (element)[FORM_RESET_HANDLER] = () => {
 			prev();
 			on_reset(true);
 		};
 	} else {
-		// @ts-expect-error
-		element.__on_r = () => on_reset(true);
+		/** @type {any} */ (element)[FORM_RESET_HANDLER] = () => on_reset(true);
 	}
 
 	add_form_reset_listener();
diff --git a/packages/svelte/src/internal/client/dom/elements/class.js b/packages/svelte/src/internal/client/dom/elements/class.js
index 038ce33f3e..6478707095 100644
--- a/packages/svelte/src/internal/client/dom/elements/class.js
+++ b/packages/svelte/src/internal/client/dom/elements/class.js
@@ -1,4 +1,5 @@
 import { to_class } from '../../../shared/attributes.js';
+import { CLASS_CACHE } from '../../constants.js';
 import { hydrating } from '../hydration.js';
 
 /**
@@ -11,8 +12,7 @@ import { hydrating } from '../hydration.js';
  * @returns {Record<string, boolean> | undefined}
  */
 export function set_class(dom, is_html, value, hash, prev_classes, next_classes) {
-	// @ts-expect-error need to add __className to patched prototype
-	var prev = dom.__className;
+	var prev = /** @type {any} */ (dom)[CLASS_CACHE];
 
 	if (
 		hydrating ||
@@ -35,8 +35,7 @@ export function set_class(dom, is_html, value, hash, prev_classes, next_classes)
 			}
 		}
 
-		// @ts-expect-error need to add __className to patched prototype
-		dom.__className = value;
+		/** @type {any} */ (dom)[CLASS_CACHE] = value;
 	} else if (next_classes && prev_classes !== next_classes) {
 		for (var key in next_classes) {
 			var is_present = !!next_classes[key];
diff --git a/packages/svelte/src/internal/client/dom/elements/events.js b/packages/svelte/src/internal/client/dom/elements/events.js
index e598a78949..5aa41e1c4d 100644
--- a/packages/svelte/src/internal/client/dom/elements/events.js
+++ b/packages/svelte/src/internal/client/dom/elements/events.js
@@ -237,9 +237,9 @@ export function handle_event_propagation(event) {
 	});
 
 	// This started because of Chromium issue https://chromestatus.com/feature/5128696823545856,
-	// where removal or moving of of the DOM can cause sync `blur` events to fire, which can cause logic
+	// where removal or moving of the DOM can cause sync `blur` events to fire, which can cause logic
 	// to run inside the current `active_reaction`, which isn't what we want at all. However, on reflection,
-	// it's probably best that all event handled by Svelte have this behaviour, as we don't really want
+	// it's probably best that all events handled by Svelte have this behaviour, as we don't really want
 	// an event handler to run in the context of another reaction or effect.
 	var previous_reaction = active_reaction;
 	var previous_effect = active_effect;
diff --git a/packages/svelte/src/internal/client/dom/elements/misc.js b/packages/svelte/src/internal/client/dom/elements/misc.js
index f350d1df8c..ad34ab9c1d 100644
--- a/packages/svelte/src/internal/client/dom/elements/misc.js
+++ b/packages/svelte/src/internal/client/dom/elements/misc.js
@@ -1,6 +1,7 @@
 import { hydrating } from '../hydration.js';
 import { clear_text_content, get_first_child } from '../operations.js';
 import { queue_micro_task } from '../task.js';
+import { FORM_RESET_HANDLER } from '../../constants.js';
 
 /**
  * @param {HTMLElement} dom
@@ -45,8 +46,7 @@ export function add_form_reset_listener() {
 				Promise.resolve().then(() => {
 					if (!evt.defaultPrevented) {
 						for (const e of /**@type {HTMLFormElement} */ (evt.target).elements) {
-							// @ts-expect-error
-							e.__on_r?.();
+							/** @type {any} */ (e)[FORM_RESET_HANDLER]?.();
 						}
 					}
 				});
diff --git a/packages/svelte/src/internal/client/dom/elements/style.js b/packages/svelte/src/internal/client/dom/elements/style.js
index 3e05eec30e..740c225f29 100644
--- a/packages/svelte/src/internal/client/dom/elements/style.js
+++ b/packages/svelte/src/internal/client/dom/elements/style.js
@@ -1,4 +1,5 @@
 import { to_style } from '../../../shared/attributes.js';
+import { STYLE_CACHE } from '../../constants.js';
 import { hydrating } from '../hydration.js';
 
 /**
@@ -28,8 +29,7 @@ function update_styles(dom, prev = {}, next, priority) {
  * @param {Record<string, any> | [Record<string, any>, Record<string, any>]} [next_styles]
  */
 export function set_style(dom, value, prev_styles, next_styles) {
-	// @ts-expect-error
-	var prev = dom.__style;
+	var prev = /** @type {any} */ (dom)[STYLE_CACHE];
 
 	if (hydrating || prev !== value) {
 		var next_style_attr = to_style(value, next_styles);
@@ -42,8 +42,7 @@ export function set_style(dom, value, prev_styles, next_styles) {
 			}
 		}
 
-		// @ts-expect-error
-		dom.__style = value;
+		/** @type {any} */ (dom)[STYLE_CACHE] = value;
 	} else if (next_styles) {
 		if (Array.isArray(next_styles)) {
 			update_styles(dom, prev_styles?.[0], next_styles[0]);
diff --git a/packages/svelte/src/internal/client/dom/operations.js b/packages/svelte/src/internal/client/dom/operations.js
index 4036aa2d61..f6d05162ca 100644
--- a/packages/svelte/src/internal/client/dom/operations.js
+++ b/packages/svelte/src/internal/client/dom/operations.js
@@ -5,7 +5,14 @@ import { init_array_prototype_warnings } from '../dev/equality.js';
 import { get_descriptor, is_extensible } from '../../shared/utils.js';
 import { active_effect } from '../runtime.js';
 import { async_mode_flag } from '../../flags/index.js';
-import { TEXT_NODE, REACTION_RAN } from '#client/constants';
+import {
+	ATTRIBUTES_CACHE,
+	CLASS_CACHE,
+	REACTION_RAN,
+	STYLE_CACHE,
+	TEXT_CACHE,
+	TEXT_NODE
+} from '#client/constants';
 import { eager_block_effects } from '../reactivity/batch.js';
 import { NAMESPACE_HTML } from '../../../constants.js';
 
@@ -48,21 +55,15 @@ export function init_operations() {
 
 	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;
+		/** @type {any} */ (element_prototype)[CLASS_CACHE] = undefined;
+		/** @type {any} */ (element_prototype)[ATTRIBUTES_CACHE] = null;
+		/** @type {any} */ (element_prototype)[STYLE_CACHE] = undefined;
 		// @ts-expect-error
 		element_prototype.__e = undefined;
 	}
 
 	if (is_extensible(text_prototype)) {
-		// @ts-expect-error
-		text_prototype.__t = undefined;
+		/** @type {any} */ (text_prototype)[TEXT_CACHE] = undefined;
 	}
 
 	if (DEV) {
diff --git a/packages/svelte/src/internal/client/reactivity/async.js b/packages/svelte/src/internal/client/reactivity/async.js
index 6aea790c36..12c5e9baa5 100644
--- a/packages/svelte/src/internal/client/reactivity/async.js
+++ b/packages/svelte/src/internal/client/reactivity/async.js
@@ -55,33 +55,38 @@ export function flatten(blockers, sync, async, fn) {
 
 	/** @param {Value[]} values */
 	function finish(values) {
+		if ((parent.f & DESTROYED) !== 0) {
+			return;
+		}
+
 		restore();
 
 		try {
 			fn(values);
 		} catch (error) {
-			if ((parent.f & DESTROYED) === 0) {
-				invoke_error_boundary(error, parent);
-			}
+			invoke_error_boundary(error, parent);
 		}
 
 		unset_context();
 	}
 
+	var decrement_pending = increment_pending();
+
 	// Fast path: blockers but no async expressions
 	if (async.length === 0) {
-		/** @type {Promise<any>} */ (blocker_promise).then(() => finish(sync.map(d)));
+		/** @type {Promise<any>} */ (blocker_promise)
+			.then(() => finish(sync.map(d)))
+			.finally(decrement_pending);
+
 		return;
 	}
 
-	var decrement_pending = increment_pending();
-
 	// Full path: has async expressions
 	function run() {
 		Promise.all(async.map((expression) => async_derived(expression)))
 			.then((result) => finish([...sync.map(d), ...result]))
 			.catch((error) => invoke_error_boundary(error, parent))
-			.finally(() => decrement_pending());
+			.finally(decrement_pending);
 	}
 
 	if (blocker_promise) {
@@ -213,22 +218,35 @@ export async function* for_await_track_reactivity_loss(iterable) {
 		throw new TypeError('value is not async iterable');
 	}
 
-	/** Whether the completion of the iterator was "normal", meaning it wasn't ended via `break` or a similar method */
-	let normal_completion = false;
+	// eslint-disable-next-line no-useless-assignment
+	let invoke_return = true;
+
 	try {
 		while (true) {
 			const { done, value } = (await track_reactivity_loss(iterator.next()))();
 			if (done) {
-				normal_completion = true;
+				invoke_return = false;
 				break;
 			}
 			var prev = reactivity_loss_tracker;
-			yield value;
+			try {
+				yield value;
+			} catch (e) {
+				set_reactivity_loss_tracker(prev);
+				// If the yield throws, we need to call `return` but not return its value, instead rethrow
+				if (iterator.return !== undefined) {
+					(await track_reactivity_loss(iterator.return()))();
+				}
+				throw e;
+			}
 			set_reactivity_loss_tracker(prev);
 		}
+	} catch (error) {
+		invoke_return = false;
+		throw error;
 	} finally {
-		// If the iterator had an abrupt completion and `return` is defined on the iterator, call it and return the value
-		if (!normal_completion && iterator.return !== undefined) {
+		// If the iterator had an abrupt completion (break) and `return` is defined on the iterator, call it and return the value
+		if (invoke_return && iterator.return !== undefined) {
 			// eslint-disable-next-line no-unsafe-finally
 			return /** @type {TReturn} */ ((await track_reactivity_loss(iterator.return()))().value);
 		}
@@ -285,15 +303,21 @@ export function run(thunks) {
 			.then(() => {
 				restore();
 
-				if (errored) {
-					throw errored.error;
-				}
+				try {
+					if (errored) {
+						throw errored.error;
+					}
 
-				if (aborted(active)) {
-					throw STALE_REACTION;
-				}
+					if (aborted(active)) {
+						throw STALE_REACTION;
+					}
 
-				return fn();
+					return fn();
+				} finally {
+					// We gotta unset context directly in case the function returns a promise, in which case
+					// unset_context in .finally() would be too late ...
+					unset_context();
+				}
 			})
 			.catch(handle_error);
 
@@ -302,6 +326,7 @@ export function run(thunks) {
 
 		promise.finally(() => {
 			blocker.settled = true;
+			// ... but we also need it after such a promise has resolved in case it restores our context
 			unset_context();
 		});
 	}
@@ -310,7 +335,7 @@ export function run(thunks) {
 		// wait one more tick, so that template effects are
 		// guaranteed to run before `$effect(...)`
 		.then(() => Promise.resolve())
-		.finally(() => decrement_pending());
+		.finally(decrement_pending);
 
 	return blockers;
 }
@@ -334,8 +359,8 @@ export function increment_pending() {
 	boundary.update_pending_count(1, batch);
 	batch.increment(blocking, effect);
 
-	return (skip = false) => {
+	return () => {
 		boundary.update_pending_count(-1, batch);
-		batch.decrement(blocking, effect, skip);
+		batch.decrement(blocking, effect);
 	};
 }
diff --git a/packages/svelte/src/internal/client/reactivity/batch.js b/packages/svelte/src/internal/client/reactivity/batch.js
index 4239cda04b..a5c9a51eec 100644
--- a/packages/svelte/src/internal/client/reactivity/batch.js
+++ b/packages/svelte/src/internal/client/reactivity/batch.js
@@ -16,7 +16,8 @@ import {
 	EAGER_EFFECT,
 	ERROR_VALUE,
 	MANAGED_EFFECT,
-	REACTION_RAN
+	REACTION_RAN,
+	DESTROYING
 } from '#client/constants';
 import { async_mode_flag } from '../../flags/index.js';
 import { deferred, define_property, includes } from '../../shared/utils.js';
@@ -33,7 +34,7 @@ import { flush_tasks, queue_micro_task } from '../dom/task.js';
 import { DEV } from 'esm-env';
 import { invoke_error_boundary } from '../error-handling.js';
 import { flush_eager_effects, old_values, set_eager_effects, source, update } from './sources.js';
-import { eager_effect, unlink_effect } from './effects.js';
+import { eager_effect, teardown, unlink_effect } from './effects.js';
 import { defer_effect } from './utils.js';
 import { UNINITIALIZED } from '../../../constants.js';
 import { set_signal_status } from './status.js';
@@ -41,8 +42,11 @@ import { legacy_is_updating_store } from './store.js';
 import { invariant } from '../../shared/dev.js';
 import { log_effect_tree } from '../dev/debug.js';
 
-/** @type {Set<Batch>} */
-const batches = new Set();
+/** @type {Batch | null} */
+let first_batch = null;
+
+/** @type {Batch | null} */
+let last_batch = null;
 
 /** @type {Batch | null} */
 export let current_batch = null;
@@ -85,13 +89,29 @@ export let collected_effects = null;
 export let legacy_updates = null;
 
 var flush_count = 0;
-var source_stacks = DEV ? new Set() : null;
+
+/** @type {Set<Value>} */
+var source_stacks = new Set();
 
 let uid = 1;
 
 export class Batch {
 	id = uid++;
 
+	/** True as soon as `#process` was called */
+	#started = false;
+
+	linked = true;
+
+	/** @type {Batch | null} */
+	#prev = null;
+
+	/** @type {Batch | null} */
+	#next = null;
+
+	/** @type {Map<Effect, ReturnType<typeof deferred<any>>>} */
+	async_deriveds = new Map();
+
 	/**
 	 * The current values of any signals that are updated in this batch.
 	 * Tuple format: [value, is_derived] (note: is_derived is false for deriveds, too, if they were overridden via assignment)
@@ -107,6 +127,13 @@ export class Batch {
 	 */
 	previous = new Map();
 
+	/**
+	 * Async effects which this batch doesn't take into account anymore when calculating blockers,
+	 * as it has a value for it already.
+	 * @type {Set<Effect>}
+	 */
+	unblocked = new Set();
+
 	/**
 	 * When the batch is committed (and the DOM is updated), we need to remove old branches
 	 * and append new ones by calling the functions added inside (if/each/key/etc) blocks
@@ -127,10 +154,9 @@ export class Batch {
 	#fork_commit_callbacks = new Set();
 
 	/**
-	 * Async effects that are currently in flight
-	 * @type {Map<Effect, number>}
+	 * The number of async effects that are currently in flight
 	 */
-	#pending = new Map();
+	#pending = 0;
 
 	/**
 	 * Async effects that are currently in flight, _not_ inside a pending boundary
@@ -188,31 +214,24 @@ export class Batch {
 
 	#decrement_queued = false;
 
-	/** @type {Set<Batch>} */
-	#blockers = new Set();
-
 	#is_deferred() {
-		return this.is_fork || this.#blocking_pending.size > 0;
-	}
+		if (this.is_fork) return true;
 
-	#is_blocked() {
-		for (const batch of this.#blockers) {
-			for (const effect of batch.#blocking_pending.keys()) {
-				var skipped = false;
-				var e = effect;
+		for (const effect of this.#blocking_pending.keys()) {
+			var e = effect;
+			var skipped = false;
 
-				while (e.parent !== null) {
-					if (this.#skipped_branches.has(e)) {
-						skipped = true;
-						break;
-					}
-
-					e = e.parent;
+			while (e.parent !== null) {
+				if (this.#skipped_branches.has(e)) {
+					skipped = true;
+					break;
 				}
 
-				if (!skipped) {
-					return true;
-				}
+				e = e.parent;
+			}
+
+			if (!skipped) {
+				return true;
 			}
 		}
 
@@ -255,11 +274,21 @@ export class Batch {
 	}
 
 	#process() {
+		this.#started = true;
+
 		if (flush_count++ > 1000) {
-			batches.delete(this);
+			this.#unlink();
 			infinite_loop_guard();
 		}
 
+		if (DEV) {
+			// track all the values that were updated during this flush,
+			// so that they can be reset afterwards
+			for (const value of this.current.keys()) {
+				source_stacks.add(value);
+			}
+		}
+
 		// we only reschedule previously-deferred effects if we expect
 		// to be able to run them after processing the batch
 		if (!this.#is_deferred()) {
@@ -314,61 +343,74 @@ export class Batch {
 		collected_effects = null;
 		legacy_updates = null;
 
-		if (this.#is_deferred() || this.#is_blocked()) {
+		// if the batch has outstanding pending work, stash effects and bail
+		if (this.#is_deferred()) {
 			this.#defer_effects(render_effects);
 			this.#defer_effects(effects);
 
 			for (const [e, t] of this.#skipped_branches) {
 				reset_branch(e, t);
 			}
-		} else {
-			if (this.#pending.size === 0) {
-				batches.delete(this);
+
+			if (updates.length > 0) {
+				/** @type {Batch} */ (/** @type {unknown} */ (current_batch)).#process();
 			}
 
-			// clear effects. Those that are still needed will be rescheduled through unskipping the skipped branches.
-			this.#dirty_effects.clear();
-			this.#maybe_dirty_effects.clear();
+			return;
+		}
+
+		const earlier_batch = this.#find_earlier_batch();
+
+		if (earlier_batch) {
+			earlier_batch.#merge(this);
+			return;
+		}
+
+		// clear effects. Those that are still needed will be rescheduled through unskipping the skipped branches.
+		this.#dirty_effects.clear();
+		this.#maybe_dirty_effects.clear();
+
+		// append/remove branches
+		for (const fn of this.#commit_callbacks) fn(this);
+		this.#commit_callbacks.clear();
+
+		previous_batch = this;
+		flush_queued_effects(render_effects);
+		flush_queued_effects(effects);
+		previous_batch = null;
 
-			// append/remove branches
-			for (const fn of this.#commit_callbacks) fn(this);
-			this.#commit_callbacks.clear();
+		this.#deferred?.resolve();
 
-			previous_batch = this;
-			flush_queued_effects(render_effects);
-			flush_queued_effects(effects);
-			previous_batch = null;
+		var next_batch = /** @type {Batch | null} */ (/** @type {unknown} */ (current_batch));
 
-			this.#deferred?.resolve();
+		if (this.linked && this.#pending === 0) {
+			this.#unlink();
 		}
 
 		// Order matters here - we need to commit and THEN continue flushing new batches, not the other way around,
 		// else we could start flushing a new batch and then, if it has pending work, rebase it right afterwards, which is wrong.
 		// In sync mode flushSync can cause #commit to wrongfully think that there needs to be a rebase, so we only do it in async mode
 		// TODO fix the underlying cause, otherwise this will likely regress when non-async mode is removed
-		if (async_mode_flag && !batches.has(this)) {
+		if (async_mode_flag && !this.linked) {
 			this.#commit();
+			// Rebases can activate other batches or null it out, therefore restore the new one here
+			current_batch = next_batch;
 		}
 
-		var next_batch = /** @type {Batch | null} */ (/** @type {unknown} */ (current_batch));
-
 		// Edge case: During traversal new branches might create effects that run immediately and set state,
 		// causing an effect and therefore a root to be scheduled again. We need to traverse the current batch
 		// once more in that case - most of the time this will just clean up dirty branches.
 		if (this.#roots.length > 0) {
-			const batch = (next_batch ??= this);
+			if (next_batch === null) {
+				next_batch = this;
+				this.#link();
+			}
+
+			const batch = next_batch;
 			batch.#roots.push(...this.#roots.filter((r) => !batch.#roots.includes(r)));
 		}
 
 		if (next_batch !== null) {
-			batches.add(next_batch);
-
-			if (DEV) {
-				for (const source of this.current.keys()) {
-					/** @type {Set<Source>} */ (source_stacks).add(source);
-				}
-			}
-
 			next_batch.#process();
 		}
 	}
@@ -425,6 +467,82 @@ export class Batch {
 		}
 	}
 
+	#find_earlier_batch() {
+		var batch = this.#prev;
+
+		while (batch !== null) {
+			if (!batch.is_fork) {
+				// if the batches are connected, break
+				for (const [value, [, is_derived]] of this.current) {
+					if (batch.current.has(value) && !is_derived) {
+						return batch;
+					}
+				}
+			}
+
+			batch = batch.#prev;
+		}
+
+		return null;
+	}
+
+	/**
+	 * @param {Batch} batch
+	 */
+	#merge(batch) {
+		for (const [source, value] of batch.current) {
+			if (!this.previous.has(source) && batch.previous.has(source)) {
+				this.previous.set(source, batch.previous.get(source));
+			}
+
+			this.current.set(source, value);
+		}
+
+		for (const [effect, deferred] of batch.async_deriveds) {
+			const d = this.async_deriveds.get(effect);
+			if (d) deferred.promise.then(d.resolve);
+		}
+
+		/**
+		 * mark all effects that depend on `batch.current`, except the
+		 * async effects that we just resolved (TODO unless they depend
+		 * on values in this batch that are NOT in the later batch?).
+		 * Through this we also will populate the correct #skipped_branches,
+		 * oncommit callbacks etc, so we don't need to merge them separately.
+		 * @param {Value} value
+		 */
+		const mark = (value) => {
+			var reactions = value.reactions;
+			if (reactions === null) return;
+
+			for (const reaction of reactions) {
+				var flags = reaction.f;
+
+				if ((flags & DERIVED) !== 0) {
+					mark(/** @type {Derived} */ (reaction));
+				} else {
+					var effect = /** @type {Effect} */ (reaction);
+
+					if (flags & (ASYNC | BLOCK_EFFECT) && !this.async_deriveds.has(effect)) {
+						this.#maybe_dirty_effects.delete(effect);
+						set_signal_status(effect, DIRTY);
+						this.schedule(effect);
+					}
+				}
+			}
+		};
+
+		for (const source of this.current.keys()) {
+			mark(source);
+		}
+
+		this.oncommit(() => batch.discard());
+		batch.#unlink();
+
+		current_batch = this;
+		this.#process();
+	}
+
 	/**
 	 * @param {Effect[]} effects
 	 */
@@ -467,9 +585,11 @@ export class Batch {
 	}
 
 	flush() {
-		var source_stacks = DEV ? new Set() : null;
-
 		try {
+			if (DEV) {
+				source_stacks.clear();
+			}
+
 			is_processing = true;
 			current_batch = this;
 
@@ -487,7 +607,7 @@ export class Batch {
 			old_values.clear();
 
 			if (DEV) {
-				for (const source of /** @type {Set<Source>} */ (source_stacks)) {
+				for (const source of source_stacks) {
 					source.updated = null;
 				}
 			}
@@ -499,7 +619,7 @@ export class Batch {
 		this.#discard_callbacks.clear();
 		this.#fork_commit_callbacks.clear();
 
-		batches.delete(this);
+		this.#unlink();
 	}
 
 	/**
@@ -510,11 +630,13 @@ export class Batch {
 	}
 
 	#commit() {
+		this.#unlink();
+
 		// If there are other pending batches, they now need to be 'rebased' —
 		// in other words, we re-run block/async effects with the newly
 		// committed state, unless the batch in question has a more
 		// recent value for a given source
-		for (const batch of batches) {
+		for (let batch = first_batch; batch !== null; batch = batch.#next) {
 			var is_earlier = batch.id < this.id;
 
 			/** @type {Source[]} */
@@ -537,6 +659,17 @@ export class Batch {
 				sources.push(source);
 			}
 
+			if (is_earlier) {
+				// TODO do we need to restart these in some cases, instead of
+				// immediately resolving them? Likely not because of how this.apply() works.
+				for (const [effect, deferred] of this.async_deriveds) {
+					const d = batch.async_deriveds.get(effect);
+					if (d) deferred.promise.then(d.resolve);
+				}
+			}
+
+			if (!batch.#started) continue;
+
 			// Re-run async/block effects that depend on distinct values changed in both batches
 			var others = [...batch.current.keys()].filter((s) => !this.current.has(s));
 
@@ -612,17 +745,6 @@ export class Batch {
 				batch.deactivate();
 			}
 		}
-
-		for (const batch of batches) {
-			if (batch.#blockers.has(this)) {
-				batch.#blockers.delete(this);
-
-				if (batch.#blockers.size === 0 && !batch.#is_deferred()) {
-					batch.activate();
-					batch.#process();
-				}
-			}
-		}
 	}
 
 	/**
@@ -630,8 +752,7 @@ export class Batch {
 	 * @param {Effect} effect
 	 */
 	increment(blocking, effect) {
-		let pending_count = this.#pending.get(effect) ?? 0;
-		this.#pending.set(effect, pending_count + 1);
+		this.#pending += 1;
 
 		if (blocking) {
 			let blocking_pending_count = this.#blocking_pending.get(effect) ?? 0;
@@ -642,16 +763,9 @@ export class Batch {
 	/**
 	 * @param {boolean} blocking
 	 * @param {Effect} effect
-	 * @param {boolean} skip - whether to skip updates (because this is triggered by a stale reaction)
 	 */
-	decrement(blocking, effect, skip) {
-		let pending_count = this.#pending.get(effect) ?? 0;
-
-		if (pending_count === 1) {
-			this.#pending.delete(effect);
-		} else {
-			this.#pending.set(effect, pending_count - 1);
-		}
+	decrement(blocking, effect) {
+		this.#pending -= 1;
 
 		if (blocking) {
 			let blocking_pending_count = this.#blocking_pending.get(effect) ?? 0;
@@ -663,12 +777,15 @@ export class Batch {
 			}
 		}
 
-		if (this.#decrement_queued || skip) return;
+		if (this.#decrement_queued) return;
 		this.#decrement_queued = true;
 
 		queue_micro_task(() => {
 			this.#decrement_queued = false;
-			this.flush();
+
+			if (this.linked) {
+				this.flush();
+			}
 		});
 	}
 
@@ -716,20 +833,14 @@ export class Batch {
 	static ensure() {
 		if (current_batch === null) {
 			const batch = (current_batch = new Batch());
+			batch.#link();
 
-			if (!is_processing) {
-				batches.add(current_batch);
-
-				if (!is_flushing_sync) {
-					queue_micro_task(() => {
-						if (!batches.has(batch) || batch.#pending.size > 0) {
-							// a flushSync happened in the meantime
-							return;
-						}
-
+			if (!is_processing && !is_flushing_sync) {
+				queue_micro_task(() => {
+					if (!batch.#started) {
 						batch.flush();
-					});
-				}
+					}
+				});
 			}
 		}
 
@@ -737,7 +848,7 @@ export class Batch {
 	}
 
 	apply() {
-		if (!async_mode_flag || (!this.is_fork && batches.size === 1)) {
+		if (!async_mode_flag || (!this.is_fork && this.#prev === null && this.#next === null)) {
 			batch_values = null;
 			return;
 		}
@@ -749,28 +860,33 @@ export class Batch {
 			batch_values.set(source, value);
 		}
 
-		// ...and undo changes belonging to other batches unless they block this one
-		for (const batch of batches) {
+		// ...and undo changes belonging to other batches unless they intersect
+		for (let batch = first_batch; batch !== null; batch = batch.#next) {
 			if (batch === this || batch.is_fork) continue;
 
-			// A batch is blocked on an earlier batch if it overlaps with the earlier batch's changes but is not a superset
+			// If two batches intersect, the latter batch will be merged into the earlier batch,
+			// and we should treat them as a single set of changes
 			var intersects = false;
-			var differs = false;
 
 			if (batch.id < this.id) {
 				for (const [source, [, is_derived]] of batch.current) {
-					// Derived values don't partake in the blocking mechanism, because a derived could
+					// Derived values don't partake in the intersection mechanism, because a derived could
 					// be triggered in one batch already but not the other one yet, causing a false-positive
 					if (is_derived) continue;
 
-					intersects ||= this.current.has(source);
-					differs ||= !this.current.has(source);
+					if (this.current.has(source)) {
+						intersects = true;
+						break;
+					}
 				}
 			}
 
-			if (intersects && differs) {
-				this.#blockers.add(batch);
-			} else {
+			// Since the latter batch merges into the earlier (if it resolves before the earlier one),
+			// we treat the earlier values as "already applied". This way we don't need to rerun async
+			// effects of the earlier batch in case they are merged.
+			// As a result you can think of batch_values as having the latest values of all intersecting
+			// batches up until this batch.
+			if (!intersects) {
 				for (const [source, previous] of batch.previous) {
 					if (!batch_values.has(source)) {
 						batch_values.set(source, previous);
@@ -836,6 +952,36 @@ export class Batch {
 
 		this.#roots.push(e);
 	}
+
+	#link() {
+		if (last_batch === null) {
+			first_batch = last_batch = this;
+		} else {
+			last_batch.#next = this;
+			this.#prev = last_batch;
+		}
+
+		last_batch = this;
+	}
+
+	#unlink() {
+		var prev = this.#prev;
+		var next = this.#next;
+
+		if (prev === null) {
+			first_batch = next;
+		} else {
+			prev.#next = next;
+		}
+
+		if (next === null) {
+			last_batch = prev;
+		} else {
+			next.#prev = prev;
+		}
+
+		this.linked = false;
+	}
 }
 
 // TODO Svelte@6 think about removing the callback argument.
@@ -1089,6 +1235,9 @@ function eager_flush() {
 	});
 }
 
+/** @type {Map<Reaction, Source<number>>} */
+var version_map = new Map();
+
 /**
  * Implementation of `$state.eager(fn())`
  * @template T
@@ -1096,10 +1245,22 @@ function eager_flush() {
  * @returns {T}
  */
 export function eager(fn) {
-	var version = source(0);
 	var initial = true;
 	var value = /** @type {T} */ (undefined);
 
+	if (active_reaction === null) {
+		return fn();
+	}
+
+	let parent = active_reaction;
+
+	let version = version_map.get(parent) ?? source(0);
+	version_map.set(parent, version);
+
+	teardown(() => {
+		if (parent.f & DESTROYING) version_map.delete(parent);
+	});
+
 	get(version);
 
 	eager_effect(() => {
@@ -1219,7 +1380,7 @@ export function fork(fn) {
 				return;
 			}
 
-			if (!batches.has(batch)) {
+			if (!batch.linked) {
 				e.fork_discarded();
 			}
 
@@ -1265,7 +1426,7 @@ export function fork(fn) {
 				source.wv = increment_write_version();
 			}
 
-			if (!committed && batches.has(batch)) {
+			if (!committed && batch.linked) {
 				batch.discard();
 			}
 		}
@@ -1276,5 +1437,5 @@ export function fork(fn) {
  * Forcibly remove all current batches, to prevent cross-talk between tests
  */
 export function clear() {
-	batches.clear();
+	first_batch = last_batch = null;
 }
diff --git a/packages/svelte/src/internal/client/reactivity/deriveds.js b/packages/svelte/src/internal/client/reactivity/deriveds.js
index eb934d96ff..8d240bca31 100644
--- a/packages/svelte/src/internal/client/reactivity/deriveds.js
+++ b/packages/svelte/src/internal/client/reactivity/deriveds.js
@@ -100,6 +100,8 @@ export function derived(fn) {
 	return signal;
 }
 
+export const OBSOLETE = Symbol('obsolete');
+
 /**
  * @template V
  * @param {() => V | Promise<V>} fn
@@ -118,13 +120,13 @@ export function async_derived(fn, label, location) {
 	var promise = /** @type {Promise<V>} */ (/** @type {unknown} */ (undefined));
 	var signal = source(/** @type {V} */ (UNINITIALIZED));
 
-	if (DEV) signal.label = label;
+	if (DEV) signal.label = label ?? fn.toString();
 
 	// only suspend in async deriveds created on initialisation
 	var should_suspend = !active_reaction;
 
-	/** @type {Map<Batch, ReturnType<typeof deferred<V>>>} */
-	var deferreds = new Map();
+	/** @type {Set<ReturnType<typeof deferred<V>>>} */
+	var deferreds = new Set();
 
 	async_effect(() => {
 		var effect = /** @type {Effect} */ (active_effect);
@@ -141,7 +143,13 @@ export function async_derived(fn, label, location) {
 			// If this code is changed at some point, make sure to still access the then property
 			// of fn() to read any signals it might access, so that we track them as dependencies.
 			// We call `unset_context` to undo any `save` calls that happen inside `fn()`
-			Promise.resolve(fn()).then(d.resolve, d.reject).finally(unset_context);
+			Promise.resolve(fn())
+				.then(d.resolve, (e) => {
+					// if the promise was rejected by the user, via `getAbortSignal`, then
+					// wait for a subsequent resolution instead of flushing the batch
+					if (e !== STALE_REACTION) d.reject(e);
+				})
+				.finally(unset_context);
 		} catch (error) {
 			d.reject(error);
 			unset_context();
@@ -180,18 +188,17 @@ export function async_derived(fn, label, location) {
 			}
 
 			if (/** @type {Boundary} */ (parent.b).is_rendered()) {
-				deferreds.get(batch)?.reject(STALE_REACTION);
-				deferreds.delete(batch); // delete to ensure correct order in Map iteration below
+				batch.async_deriveds.get(effect)?.reject(OBSOLETE);
 			} else {
 				// While the boundary is still showing pending, a new run supersedes all older in-flight runs
 				// for this async expression. Cancel eagerly so resolution cannot commit stale values.
 				for (const d of deferreds.values()) {
-					d.reject(STALE_REACTION);
+					d.reject(OBSOLETE);
 				}
-				deferreds.clear();
 			}
 
-			deferreds.set(batch, d);
+			deferreds.add(d);
+			batch.async_deriveds.set(effect, d);
 		}
 
 		/**
@@ -203,16 +210,10 @@ export function async_derived(fn, label, location) {
 				reactivity_loss_tracker = null;
 			}
 
-			if (decrement_pending) {
-				// don't trigger an update if we're only here because
-				// the promise was superseded before it could resolve
-				var skip = error === STALE_REACTION;
-				decrement_pending(skip);
-			}
+			decrement_pending?.();
+			deferreds.delete(d);
 
-			if (error === STALE_REACTION || (effect.f & DESTROYED) !== 0) {
-				return;
-			}
+			if (error === OBSOLETE) return;
 
 			batch.activate();
 
@@ -228,18 +229,11 @@ export function async_derived(fn, label, location) {
 
 				internal_set(signal, value);
 
-				// All prior async derived runs are now stale
-				for (const [b, d] of deferreds) {
-					deferreds.delete(b);
-					if (b === batch) break;
-					d.resolve(value);
-				}
-
 				if (DEV && location !== undefined) {
 					recent_async_deriveds.add(signal);
 
 					setTimeout(() => {
-						if (recent_async_deriveds.has(signal)) {
+						if (recent_async_deriveds.has(signal) && (effect.f & DESTROYED) === 0) {
 							w.await_waterfall(/** @type {string} */ (signal.label), location);
 							recent_async_deriveds.delete(signal);
 						}
@@ -254,8 +248,8 @@ export function async_derived(fn, label, location) {
 	});
 
 	teardown(() => {
-		for (const d of deferreds.values()) {
-			d.reject(STALE_REACTION);
+		for (const d of deferreds) {
+			d.reject(OBSOLETE);
 		}
 	});
 
@@ -344,7 +338,12 @@ export function execute_derived(derived) {
 	var prev_active_effect = active_effect;
 	var parent = derived.parent;
 
-	if (!is_destroying_effect && parent !== null && (parent.f & (DESTROYED | INERT)) !== 0) {
+	if (
+		!is_destroying_effect &&
+		parent !== null &&
+		derived.v !== UNINITIALIZED && // if it was never evaluated before, it's guaranteed to fail downstream, so we try to execute instead
+		(parent.f & (DESTROYED | INERT)) !== 0
+	) {
 		w.derived_inert();
 
 		return derived.v;
@@ -453,8 +452,8 @@ export function freeze_derived_effects(derived) {
 			// make it a noop so it doesn't get called again if the derived
 			// is unfrozen. we don't set it to `null`, because the existence
 			// of a teardown function is what determines whether the
-			// effect runs again during unfreezing
-			e.teardown = noop;
+			// effect runs again during unfreezing (but not for teardown-only effects)
+			if (e.fn !== null) e.teardown = noop;
 			e.ac = null;
 
 			remove_reactions(e, 0);
@@ -472,7 +471,7 @@ export function unfreeze_derived_effects(derived) {
 	for (const e of derived.effects) {
 		// if the effect was previously frozen — indicated by the presence
 		// of a teardown function — unfreeze it
-		if (e.teardown) {
+		if (e.teardown && e.fn !== null) {
 			update_effect(e);
 		}
 	}
diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index 0fad074e6f..5bdba037b1 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -43,7 +43,7 @@ import { define_property } from '../../shared/utils.js';
 import { get_next_sibling } from '../dom/operations.js';
 import { component_context, dev_current_component_function, dev_stack } from '../context.js';
 import { Batch, collected_effects, current_batch } from './batch.js';
-import { flatten, increment_pending } from './async.js';
+import { flatten } from './async.js';
 import { without_reactive_context } from '../dom/elements/bindings/shared.js';
 import { set_signal_status } from './status.js';
 
@@ -396,16 +396,8 @@ export function template_effect(fn, sync = [], async = [], blockers = []) {
  * @param {Blocker[]} blockers
  */
 export function deferred_template_effect(fn, sync = [], async = [], blockers = []) {
-	if (async.length > 0 || blockers.length > 0) {
-		var decrement_pending = increment_pending();
-	}
-
 	flatten(blockers, sync, async, (values) => {
 		create_effect(EFFECT, () => fn(...values.map(get)));
-
-		if (decrement_pending) {
-			decrement_pending();
-		}
 	});
 }
 
diff --git a/packages/svelte/src/internal/client/reactivity/store.js b/packages/svelte/src/internal/client/reactivity/store.js
index 7124e23db8..726765b619 100644
--- a/packages/svelte/src/internal/client/reactivity/store.js
+++ b/packages/svelte/src/internal/client/reactivity/store.js
@@ -21,7 +21,7 @@ export let legacy_is_updating_store = false;
  */
 let is_store_binding = false;
 
-let IS_UNMOUNTED = Symbol();
+let IS_UNMOUNTED = Symbol('unmounted');
 
 /**
  * Gets the current value of a store. If the store isn't subscribed to yet, it will create a proxy
diff --git a/packages/svelte/src/internal/client/render.js b/packages/svelte/src/internal/client/render.js
index cb152ed9c1..50832fb3ff 100644
--- a/packages/svelte/src/internal/client/render.js
+++ b/packages/svelte/src/internal/client/render.js
@@ -23,7 +23,7 @@ import * as w from './warnings.js';
 import * as e from './errors.js';
 import { assign_nodes } from './dom/template.js';
 import { is_passive_event } from '../../utils.js';
-import { COMMENT_NODE, STATE_SYMBOL } from './constants.js';
+import { COMMENT_NODE, STATE_SYMBOL, TEXT_CACHE } from './constants.js';
 import { boundary } from './dom/blocks/boundary.js';
 
 /**
@@ -46,10 +46,9 @@ export function set_should_intro(value) {
 export function set_text(text, value) {
 	// For objects, we apply string coercion (which might make things like $state array references in the template reactive) before diffing
 	var str = value == null ? '' : typeof value === 'object' ? `${value}` : value;
-	// @ts-expect-error
-	if (str !== (text.__t ??= text.nodeValue)) {
-		// @ts-expect-error
-		text.__t = str;
+	// prettier-ignore
+	if (str !== (/** @type {any} */ (text)[TEXT_CACHE] ??= text.nodeValue)) {
+		/** @type {any} */ (text)[TEXT_CACHE] = str;
 		text.nodeValue = `${str}`;
 	}
 }
diff --git a/packages/svelte/src/internal/server/hydratable.js b/packages/svelte/src/internal/server/hydratable.js
index 81f59ab2fd..be75288604 100644
--- a/packages/svelte/src/internal/server/hydratable.js
+++ b/packages/svelte/src/internal/server/hydratable.js
@@ -3,7 +3,6 @@ import { async_mode_flag } from '../flags/index.js';
 import { get_render_context } from './render-context.js';
 import * as e from './errors.js';
 import * as devalue from 'devalue';
-import { get_stack } from '../shared/dev.js';
 import { DEV } from 'esm-env';
 import { get_user_code_location } from './dev.js';
 
@@ -65,7 +64,13 @@ function encode(key, value, unresolved) {
 			const placeholder = `"${uid++}"`;
 			const p = value
 				.then((v) => {
-					entry.serialized = entry.serialized.replace(placeholder, `r(${uneval(v)})`);
+					entry.serialized = entry.serialized.replace(
+						placeholder,
+						// use the function form here to prevent any string replacement characters from being interpreted
+						// in `v`, as it's potentially user-controlled and therefore potentially malicious.
+						// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/replace#specifying_a_string_as_the_replacement
+						() => `r(${uneval(v)})`
+					);
 				})
 				.catch((devalue_error) =>
 					e.hydratable_serialization_failed(
diff --git a/packages/svelte/src/internal/server/hydratable.test.ts b/packages/svelte/src/internal/server/hydratable.test.ts
new file mode 100644
index 0000000000..8dd54c8f1d
--- /dev/null
+++ b/packages/svelte/src/internal/server/hydratable.test.ts
@@ -0,0 +1,33 @@
+import { afterAll, beforeAll, expect, test } from 'vitest';
+import { Renderer } from './renderer.js';
+import type { Component } from 'svelte';
+import { disable_async_mode_flag, enable_async_mode_flag } from '../flags/index.js';
+import { hydratable } from './hydratable.js';
+
+beforeAll(() => {
+	enable_async_mode_flag();
+});
+
+afterAll(() => {
+	disable_async_mode_flag();
+});
+
+test('treats replacement tokens in hydratable promise values as literals', async () => {
+	const component = (renderer: Renderer) => {
+		hydratable('key', () => Promise.resolve(`$'`));
+		renderer.child(async () => {
+			await Promise.resolve();
+		});
+		renderer.push('ok');
+	};
+
+	const { head } = await Renderer.render(component as unknown as Component);
+	const script_match = head.match(/<script(?:\s[^>]*)?>([\s\S]*)<\/script>/);
+
+	expect(script_match, 'expected hydratable script in head output').toBeTruthy();
+
+	const script_content = script_match![1];
+	expect(script_content).toContain('const h = (window.__svelte ??= {}).h ??= new Map();');
+	expect(script_content).toContain('r("$\'")');
+	expect(script_content).toMatch(/\[\s*"key"\s*,\s*r\("\$'"\)\s*\]/);
+});
diff --git a/packages/svelte/src/internal/server/index.js b/packages/svelte/src/internal/server/index.js
index 34d0133a31..12f76f188e 100644
--- a/packages/svelte/src/internal/server/index.js
+++ b/packages/svelte/src/internal/server/index.js
@@ -151,7 +151,7 @@ export function attributes(attrs, css_hash, classes, styles, flags = 0) {
 		// omit functions, internal svelte properties and invalid attribute names
 		if (typeof attrs[name] === 'function') continue;
 		if (name[0] === '$' && name[1] === '$') continue; // faster than name.startsWith('$$')
-		if (INVALID_ATTR_NAME_CHAR_REGEX.test(name)) continue;
+		if (name === '' || INVALID_ATTR_NAME_CHAR_REGEX.test(name)) continue;
 
 		var value = attrs[name];
 		var lower = name.toLowerCase();
diff --git a/packages/svelte/src/internal/server/renderer.js b/packages/svelte/src/internal/server/renderer.js
index d2ab35a1f2..35aac64721 100644
--- a/packages/svelte/src/internal/server/renderer.js
+++ b/packages/svelte/src/internal/server/renderer.js
@@ -715,7 +715,12 @@ export class Renderer {
 						const { context, failed, transformError } = item.#boundary;
 
 						set_ssr_context(context);
-						let transformed = await transformError(error);
+
+						let promise = transformError(error);
+						set_ssr_context(null);
+
+						let transformed = await promise;
+						set_ssr_context(context);
 
 						// Render the failed snippet instead of the partial children content
 						const failed_renderer = new Renderer(item.global, item);
diff --git a/packages/svelte/src/reactivity/url-search-params.js b/packages/svelte/src/reactivity/url-search-params.js
index 2381e11875..2e70bf518d 100644
--- a/packages/svelte/src/reactivity/url-search-params.js
+++ b/packages/svelte/src/reactivity/url-search-params.js
@@ -4,7 +4,7 @@ import { tag } from '../internal/client/dev/tracing.js';
 import { get } from '../internal/client/runtime.js';
 import { get_current_url } from './url.js';
 
-export const REPLACE = Symbol();
+export const REPLACE = Symbol('replace');
 
 /**
  * A reactive version of the built-in [`URLSearchParams`](https://developer.mozilla.org/en-US/docs/Web/API/URLSearchParams) object.
diff --git a/packages/svelte/src/utils.js b/packages/svelte/src/utils.js
index 57561e6dc7..54757a6f13 100644
--- a/packages/svelte/src/utils.js
+++ b/packages/svelte/src/utils.js
@@ -491,7 +491,7 @@ export function is_raw_text_element(name) {
 // Rejects strings containing whitespace, quotes, angle brackets, slashes, equals,
 // or other characters that could break out of a tag-name token and enable markup injection.
 export const REGEX_VALID_TAG_NAME =
-	/^[a-zA-Z][a-zA-Z0-9]*(-[a-zA-Z0-9.\-_\u00B7\u00C0-\u00D6\u00D8-\u00F6\u00F8-\u037D\u037F-\u1FFF\u200C-\u200D\u203F-\u2040\u2070-\u218F\u2C00-\u2FEF\u3001-\uD7FF\uF900-\uFDCF\uFDF0-\uFFFD\u{10000}-\u{EFFFF}]+)*$/u;
+	/^[a-zA-Z][a-zA-Z0-9]*(-[a-zA-Z0-9.\-_\u00B7\u00C0-\u00D6\u00D8-\u00F6\u00F8-\u037D\u037F-\u1FFF\u200C-\u200D\u203F-\u2040\u2070-\u218F\u2C00-\u2FEF\u3001-\uD7FF\uF900-\uFDCF\uFDF0-\uFFFD\u{10000}-\u{EFFFF}]*)?$/u;
 
 /**
  * Prevent devtools trying to make `location` a clickable link by inserting a zero-width space
diff --git a/packages/svelte/src/utils.test.ts b/packages/svelte/src/utils.test.ts
new file mode 100644
index 0000000000..02175ae93f
--- /dev/null
+++ b/packages/svelte/src/utils.test.ts
@@ -0,0 +1,50 @@
+import { expect, test } from 'vitest';
+import { REGEX_VALID_TAG_NAME } from './utils';
+
+test('REGEX_VALID_TAG_NAME accepts common HTML tag names', () => {
+	const common_html_tag_names = ['div', 'span', 'button', 'input', 'svg', 'math', 'a'];
+
+	for (const tag_name of common_html_tag_names) {
+		expect(REGEX_VALID_TAG_NAME.test(tag_name)).toBe(true);
+	}
+});
+
+test('REGEX_VALID_TAG_NAME accepts basic custom element names', () => {
+	const valid_custom_tag_names = ['my-element', 'x-foo', 'todo-item', 'my-element2'];
+
+	for (const tag_name of valid_custom_tag_names) {
+		expect(REGEX_VALID_TAG_NAME.test(tag_name)).toBe(true);
+	}
+});
+
+test('REGEX_VALID_TAG_NAME accepts spec-allowed custom element characters', () => {
+	const valid_custom_tag_names = [
+		'x-foo.bar',
+		'x-foo_bar',
+		'x-foo\u00B7bar',
+		'x-foo\u00FCbar',
+		'x-foo\u{1F600}bar',
+		'x-'
+	];
+
+	for (const tag_name of valid_custom_tag_names) {
+		expect(REGEX_VALID_TAG_NAME.test(tag_name)).toBe(true);
+	}
+});
+
+test('REGEX_VALID_TAG_NAME rejects invalid tag names', () => {
+	const invalid_tag_names = ['', '1', 'x\u00FC', '-x-foo', '1foo', 'x-foo bar', 'x-foo/', 'x-foo>'];
+
+	for (const tag_name of invalid_tag_names) {
+		expect(REGEX_VALID_TAG_NAME.test(tag_name)).toBe(false);
+	}
+});
+
+test('REGEX_VALID_TAG_NAME no ReDoS', () => {
+	const before = performance.now();
+	REGEX_VALID_TAG_NAME.test('a-----------------------------------!');
+	const after = performance.now();
+	if (after - before > 10) {
+		throw new Error(`REGEX_VALID_TAG_NAME is vulnerable to ReDoS`);
+	}
+});
diff --git a/packages/svelte/src/version.js b/packages/svelte/src/version.js
index 04b0b0398a..446904cd14 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 = '5.55.5';
+export const VERSION = '5.55.8';
 export const PUBLIC_VERSION = '5';
diff --git a/packages/svelte/tests/print/samples/css-keyframes-percent/input.svelte b/packages/svelte/tests/print/samples/css-keyframes-percent/input.svelte
new file mode 100644
index 0000000000..b2a0e3aa7a
--- /dev/null
+++ b/packages/svelte/tests/print/samples/css-keyframes-percent/input.svelte
@@ -0,0 +1,7 @@
+<style>
+  @keyframes foo {
+    0% { left: 0px; }
+    50% { left: 50px; }
+    100% { left: 100px; }
+  }
+</style>
diff --git a/packages/svelte/tests/print/samples/css-keyframes-percent/output.svelte b/packages/svelte/tests/print/samples/css-keyframes-percent/output.svelte
new file mode 100644
index 0000000000..e35a5780fa
--- /dev/null
+++ b/packages/svelte/tests/print/samples/css-keyframes-percent/output.svelte
@@ -0,0 +1,13 @@
+<style>
+	@keyframes foo {
+		0% {
+			left: 0px;
+		}
+		50% {
+			left: 50px;
+		}
+		100% {
+			left: 100px;
+		}
+	}
+</style>
diff --git a/packages/svelte/tests/print/samples/style/output.svelte b/packages/svelte/tests/print/samples/style/output.svelte
index 03168cccae..9fc5e3fbba 100644
--- a/packages/svelte/tests/print/samples/style/output.svelte
+++ b/packages/svelte/tests/print/samples/style/output.svelte
@@ -19,7 +19,7 @@
 		from {
 			opacity: 0;
 		}
-		50%% {
+		50% {
 			opacity: 0.5;
 		}
 		to {
diff --git a/packages/svelte/tests/print/samples/svelte-body/input.svelte b/packages/svelte/tests/print/samples/svelte-body/input.svelte
new file mode 100644
index 0000000000..a4c26db5ce
--- /dev/null
+++ b/packages/svelte/tests/print/samples/svelte-body/input.svelte
@@ -0,0 +1 @@
+<svelte:body onmousemove={handleMousemove} />
diff --git a/packages/svelte/tests/print/samples/svelte-body/output.svelte b/packages/svelte/tests/print/samples/svelte-body/output.svelte
new file mode 100644
index 0000000000..e13eaae979
--- /dev/null
+++ b/packages/svelte/tests/print/samples/svelte-body/output.svelte
@@ -0,0 +1 @@
+<svelte:body onmousemove={handleMousemove}></svelte:body>
diff --git a/packages/svelte/tests/runtime-browser/samples/dom-clobbering-cache-symbols-spread/_config.js b/packages/svelte/tests/runtime-browser/samples/dom-clobbering-cache-symbols-spread/_config.js
new file mode 100644
index 0000000000..62248851db
--- /dev/null
+++ b/packages/svelte/tests/runtime-browser/samples/dom-clobbering-cache-symbols-spread/_config.js
@@ -0,0 +1,23 @@
+import { assert_ok, test } from '../../assert';
+
+export default test({
+	async test({ assert, target, waitUntil, window }) {
+		const form = target.querySelector('form');
+		const button = target.querySelector('button');
+		const [i1, i2, i3] = target.querySelectorAll('input');
+		assert_ok(form);
+		assert_ok(button);
+
+		assert.equal(form.id, 'initial-form');
+		assert.equal(form.className, 'first');
+		assert.equal(window.getComputedStyle(form).backgroundColor, 'rgb(255, 0, 0)');
+
+		button.click();
+		await waitUntil(() => form.id === 'updated-form');
+
+		assert.equal(form.id, 'updated-form');
+		assert.equal(form.className, 'second');
+		assert.equal(i3.id, '', 'input clobbered form');
+		assert.equal(window.getComputedStyle(form).backgroundColor, 'rgb(0, 0, 255)');
+	}
+});
diff --git a/packages/svelte/tests/runtime-browser/samples/dom-clobbering-cache-symbols-spread/main.svelte b/packages/svelte/tests/runtime-browser/samples/dom-clobbering-cache-symbols-spread/main.svelte
new file mode 100644
index 0000000000..60e9b80e81
--- /dev/null
+++ b/packages/svelte/tests/runtime-browser/samples/dom-clobbering-cache-symbols-spread/main.svelte
@@ -0,0 +1,20 @@
+<script>
+	let form_attributes = $state({ id: 'initial-form' });
+	let class_name = $state('first');
+	let background_color = $state('rgb(255, 0, 0)');
+
+	function update() {
+		form_attributes = { id: 'updated-form' };
+		class_name = 'second';
+		background_color = 'rgb(0, 0, 255)';
+	}
+</script>
+
+<button onclick={update}>update</button>
+
+<form {...form_attributes} class={class_name} style:background-color={background_color}>
+	<!-- the once non-symbol-ified hidden properties we used -->
+	<input {...{ name: '__className' }} value="x" />
+	<input {...{ name: '__style' }} value="y" />
+	<input {...{ name: '__attributes' }} value="z" />
+</form>
diff --git a/packages/svelte/tests/runtime-legacy/shared.ts b/packages/svelte/tests/runtime-legacy/shared.ts
index 454ae2f766..6f30fb5d98 100644
--- a/packages/svelte/tests/runtime-legacy/shared.ts
+++ b/packages/svelte/tests/runtime-legacy/shared.ts
@@ -60,6 +60,8 @@ export interface RuntimeTest<Props extends Record<string, any> = Record<string,
 	id_prefix?: string;
 	before_test?: () => void;
 	after_test?: () => void;
+	/** If true, flushSync() will not be called before invoking test() */
+	skip_initial_flushSync?: boolean;
 	test?: (args: {
 		variant: 'dom' | 'hydrate';
 		assert: Assert;
@@ -505,7 +507,7 @@ async function run_test_variant(
 
 			try {
 				if (config.test) {
-					flushSync();
+					if (!config.skip_initial_flushSync) flushSync();
 
 					if (variant === 'hydrate' && cwd.includes('async-')) {
 						// wait for pending boundaries to render
@@ -543,7 +545,7 @@ async function run_test_variant(
 				}
 			} finally {
 				if (runes) {
-					unmount(instance);
+					await unmount(instance);
 				} else {
 					instance.$destroy();
 				}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-batch-order/_config.js b/packages/svelte/tests/runtime-runes/samples/async-batch-order/_config.js
new file mode 100644
index 0000000000..53cceb9d54
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-batch-order/_config.js
@@ -0,0 +1,30 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [increment, shift, middle] = target.querySelectorAll('button');
+		const [div] = target.querySelectorAll('div');
+
+		increment.click();
+		await tick();
+		increment.click();
+		await tick();
+		increment.click();
+		await tick();
+		middle.click(); // resolve the second increment which will make the if block go away and the first batch discarded
+		await tick();
+		assert.htmlEqual(div.innerHTML, '2 2');
+
+		shift.click();
+		await tick();
+		shift.click();
+		await tick();
+		shift.click();
+		await tick();
+		shift.click();
+		await tick();
+		assert.htmlEqual(div.innerHTML, '3 3');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-batch-order/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-batch-order/main.svelte
new file mode 100644
index 0000000000..0289380d78
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-batch-order/main.svelte
@@ -0,0 +1,21 @@
+<script>
+	let a = $state(0);
+
+	const deferred = [];
+
+	function delay(value) {
+		if (!value) return value;
+		return new Promise((resolve) => deferred.push(() => resolve(value)));
+	}
+</script>
+
+<div>
+	{a} {await delay(a)}
+	{#if a < 2}
+		{await delay(a)}
+	{/if}
+</div>
+
+<button onclick={() => {a++;}}>a++</button>
+<button onclick={() => deferred.shift()?.()}>shift</button>
+<button onclick={() => deferred[2]()}>middle</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-commit-preserve-new-batch/_config.js b/packages/svelte/tests/runtime-runes/samples/async-commit-preserve-new-batch/_config.js
new file mode 100644
index 0000000000..922feed515
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-commit-preserve-new-batch/_config.js
@@ -0,0 +1,19 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+// Tests that batch.#commit() does not null out a potentially new current_batch
+export default test({
+	skip_initial_flushSync: true, // test that the initial batch is flushed without an explicit flushSync() call
+	async test({ assert, target }) {
+		await tick();
+
+		const [button] = target.querySelectorAll('button');
+		const [updates] = target.querySelectorAll('p');
+
+		assert.htmlEqual(updates.innerHTML, 'false');
+
+		button.click();
+		await tick();
+		assert.htmlEqual(updates.innerHTML, 'true');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-commit-preserve-new-batch/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-commit-preserve-new-batch/main.svelte
new file mode 100644
index 0000000000..f7dae33b7e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-commit-preserve-new-batch/main.svelte
@@ -0,0 +1,30 @@
+<script>
+	let count = $state(-1);
+	let payload = $state(false);
+	let updated = $state(false);
+
+	$effect(() => {
+		if (payload) {
+			updated = true;
+		}
+	});
+
+	function update() {
+		count = 0;
+		queueMicrotask(() => {
+			payload = true;
+		});
+	}
+</script>
+
+<button onclick={update}>update</button>
+
+<p>{updated}</p>
+
+<svelte:boundary>
+	{await new Promise(() => {})}
+
+	{#snippet pending()}
+		<p>pending</p>
+	{/snippet}
+</svelte:boundary>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-eager-block/_config.js b/packages/svelte/tests/runtime-runes/samples/async-eager-block/_config.js
new file mode 100644
index 0000000000..b6d283c8a5
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-eager-block/_config.js
@@ -0,0 +1,23 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [increment, resolve] = target.querySelectorAll('button');
+
+		increment.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			'<button>increment</button> <button>resolve</button> 0 <p>loading...</p>'
+		);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			'<button>increment</button> <button>resolve</button> 1 <p>1</p>'
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-eager-block/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-eager-block/main.svelte
new file mode 100644
index 0000000000..61f4705d06
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-eager-block/main.svelte
@@ -0,0 +1,20 @@
+<script>
+	let count = $state(0);
+
+	const queued = [];
+
+	async function delay(v) {
+		if (!v) return v;
+		return new Promise(r => queued.push(() => r(v)));
+	}
+</script>
+
+<button onclick={() => count++}>increment</button>
+<button onclick={() => queued.shift()?.()}>resolve</button>
+
+{await delay(count)} 
+{#if $state.eager(count) !== count}
+	<p>loading...</p>
+{:else}
+	<p>{count}</p>
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-eager-each-block/_config.js b/packages/svelte/tests/runtime-runes/samples/async-eager-each-block/_config.js
new file mode 100644
index 0000000000..a4921a5115
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-eager-each-block/_config.js
@@ -0,0 +1,32 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target, logs }) {
+		await tick();
+		const [increment, resolve] = target.querySelectorAll('button');
+		logs.length = 0;
+
+		increment.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>increment</button> <button>resolve</button>
+			<ul><li>0 / 0</li><li>0 / loading...</li><li>0 / 0</li></ul>`
+		);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>increment</button> <button>resolve</button>
+			<ul><li>0 / 0</li><li>1 / 1</li><li>0 / 0</li></ul>`
+		);
+
+		assert.equal(
+			logs.some((l) => l.toString().includes('0 ') || l.toString().includes('2')),
+			false,
+			'only the second $state.eager should have been evaluated'
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-eager-each-block/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-eager-each-block/main.svelte
new file mode 100644
index 0000000000..f27e256e9f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-eager-each-block/main.svelte
@@ -0,0 +1,24 @@
+<script>
+	let counts = $state([0, 0, 0]);
+	const queued = [];
+	async function delay(v) {
+		if (!v) return v;
+		return new Promise(r => queued.push(() => r(v)));
+	}
+</script>
+
+<button onclick={() => counts[1]++}>increment</button>
+<button onclick={() => queued.shift()?.()}>resolve</button>
+
+<ul>
+	{#each counts as count, i}
+		<li>
+			{await delay(count)} /
+			{#if console.log(i) || $state.eager(count) !== count}
+				loading...
+			{:else}
+				{count}
+			{/if}
+		</li>
+	{/each}
+</ul>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-flushsync-in-effect/_config.js b/packages/svelte/tests/runtime-runes/samples/async-flushsync-in-effect/_config.js
new file mode 100644
index 0000000000..59a81afd35
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-flushsync-in-effect/_config.js
@@ -0,0 +1,25 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+
+		const [increment, shift] = target.querySelectorAll('button');
+
+		increment.click();
+		await tick();
+
+		assert.htmlEqual(target.innerHTML, '<button>clicks: 0</button><button>shift</button> 0');
+
+		shift.click();
+		await tick();
+
+		assert.htmlEqual(target.innerHTML, '<button>clicks: 1</button><button>shift</button> 1');
+
+		shift.click();
+		await tick();
+
+		assert.htmlEqual(target.innerHTML, '<button>clicks: 2</button><button>shift</button> 2');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-flushsync-in-effect/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-flushsync-in-effect/main.svelte
new file mode 100644
index 0000000000..12c4dd578e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-flushsync-in-effect/main.svelte
@@ -0,0 +1,25 @@
+<script lang="ts">
+	import { flushSync } from 'svelte';
+
+	let count = $state(0);
+
+	const queue: Array<() => void> = [];
+
+	$effect(() => {
+		if (count === 1) {
+			count = 2;
+			flushSync();
+		}
+	})
+
+	function push(v: number) {
+		if (v === 0) return v;
+		return new Promise(r => queue.push(() => r(v)));
+	}
+</script>
+
+<button onclick={() => count += 1}>
+	clicks: {count}
+</button>
+<button onclick={() => queue.shift()?.()}>shift</button>
+{await push(count)}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-inner-after-outer/_config.js b/packages/svelte/tests/runtime-runes/samples/async-inner-after-outer/_config.js
index 8905ee4bf5..c12eba7d17 100644
--- a/packages/svelte/tests/runtime-runes/samples/async-inner-after-outer/_config.js
+++ b/packages/svelte/tests/runtime-runes/samples/async-inner-after-outer/_config.js
@@ -34,18 +34,6 @@ export default test({
 		shift?.click();
 		await tick();
 
-		assert.htmlEqual(
-			target.innerHTML,
-			`
-			<p>true</p>
-			<button>toggle</button>
-			<button>shift</button>
-		`
-		);
-
-		shift?.click();
-		await tick();
-
 		assert.htmlEqual(
 			target.innerHTML,
 			`
diff --git a/packages/svelte/tests/runtime-runes/samples/async-new-batch-during-initial-load/_config.js b/packages/svelte/tests/runtime-runes/samples/async-new-batch-during-initial-load/_config.js
new file mode 100644
index 0000000000..c8bc4c986f
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-new-batch-during-initial-load/_config.js
@@ -0,0 +1,20 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [increment, pop] = target.querySelectorAll('button');
+
+		increment.click();
+		await tick();
+		increment.click();
+		await tick();
+		pop.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, `<button>increment</button> <button>pop</button> 2 2 1`);
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, `<button>increment</button> <button>pop</button> 2 2 1`);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-new-batch-during-initial-load/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-new-batch-during-initial-load/main.svelte
new file mode 100644
index 0000000000..7689af049c
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-new-batch-during-initial-load/main.svelte
@@ -0,0 +1,26 @@
+<script>
+	let count = $state(0);
+	let other = $state(0);
+
+	const queue = [];
+	function push(v) {
+		return new Promise((r,e) => queue.push(() => v === 1 ? e(v) : r(v)));
+	}
+</script>
+
+<button onclick={() => {
+	if (count === 0) {
+		other++;
+		count++;
+	} else {
+		count++
+	}
+}}>increment</button>
+<button onclick={() => queue.pop()?.()}>pop</button>
+
+{#if count > 0}
+	<svelte:boundary>
+		{await push(count)} {count} {other}
+		{#snippet failed()}boom{/snippet}
+	</svelte:boundary> 
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/Child.svelte b/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/Child.svelte
new file mode 100644
index 0000000000..1d9bdfada2
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/Child.svelte
@@ -0,0 +1,6 @@
+<script>
+	let { count } = $props();
+	let double = $derived(count * 2);
+
+	$effect.pre(() => console.log(count, double));
+</script>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/_config.js b/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/_config.js
new file mode 100644
index 0000000000..83364706e5
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/_config.js
@@ -0,0 +1,27 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target, logs, warnings }) {
+		const [increment, resolve] = target.querySelectorAll('button');
+
+		increment.click();
+		await tick();
+		assert.deepEqual(logs, []);
+
+		resolve.click();
+		await tick();
+		assert.deepEqual(logs, []);
+
+		resolve.click();
+		await tick();
+		assert.deepEqual(logs, []);
+
+		resolve.click();
+		await tick();
+		assert.deepEqual(logs, [1, 2]);
+
+		// no await waterfall / inert derived warnings
+		assert.deepEqual(warnings, []);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/main.svelte
new file mode 100644
index 0000000000..fe01ae457e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-obsolete-branch-no-effect-runs/main.svelte
@@ -0,0 +1,31 @@
+<script>
+	import Child from "./Child.svelte";
+	let count = $state(0);
+
+	let deferreds = [];
+
+	function push(v) {
+		return new Promise((resolve, reject) => {
+			deferreds.push({ resolve: () => resolve(v), reject });
+		});
+	}
+</script>
+
+<button onclick={() => count += 1}>increment</button>
+<button onclick={() => deferreds.shift()?.resolve()}>resolve</button>
+
+<svelte:boundary>
+	{#if count % 2 === 0}
+		{@const double = count * 2}
+		<p>true</p>
+		{await push(count)} {double}
+		<Child count={await push(count)} />
+	{:else}
+		<p>false</p>
+		<Child count={await push(count)} />
+	{/if}
+
+	{#snippet pending()}
+		<p>loading...</p>
+	{/snippet}
+</svelte:boundary>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-1/_config.js b/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-1/_config.js
new file mode 100644
index 0000000000..9785f639cb
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-1/_config.js
@@ -0,0 +1,24 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+import { normalise_trace_logs } from '../../../helpers.js';
+
+export default test({
+	compileOptions: {
+		dev: true
+	},
+	html: '<p>pending</p>',
+	async test({ assert, target, warnings }) {
+		await tick();
+
+		assert.htmlEqual(
+			target.innerHTML,
+			'<h1>number -> number -> number -> return -> body failed -> ended</h1>'
+		);
+
+		assert.deepEqual(normalise_trace_logs(warnings), [
+			{
+				log: 'Detected reactivity loss when reading `values[1]`. This happens when state is read in an async function after an earlier `await`'
+			}
+		]);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-1/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-1/main.svelte
new file mode 100644
index 0000000000..da7c48642c
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-1/main.svelte
@@ -0,0 +1,45 @@
+<script>
+	let values = $state([0, 1, 2]);
+
+	async function get_result() {
+		const logs = [];
+
+		const iterator = {
+			index: 0,
+			async next() {
+				if (this.index > 2) { done: true }
+				return { done: false, value: values[this.index++] };
+			},
+			async return() {
+				logs.push('return');
+			},
+			[Symbol.asyncIterator]() {
+				return this;
+			}
+		};
+
+		try {
+			for await (const value of iterator) {
+				logs.push('number');
+				// Read reactive state after async iterator await.
+				if (values.length === 3 && value === 2) {
+					throw new Error('body failed');
+				}
+			}
+			logs.push('done');
+		} catch (error) {
+			logs.push(error.message);
+		}
+
+		logs.push('ended');
+		return logs.join(' -> ');
+	}
+</script>
+
+<svelte:boundary>
+	<h1>{await get_result()}</h1>
+
+	{#snippet pending()}
+		<p>pending</p>
+	{/snippet}
+</svelte:boundary>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-2/_config.js b/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-2/_config.js
new file mode 100644
index 0000000000..9e8a2d8def
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-2/_config.js
@@ -0,0 +1,21 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+import { normalise_trace_logs } from '../../../helpers.js';
+
+export default test({
+	compileOptions: {
+		dev: true
+	},
+	html: '<p>pending</p>',
+	async test({ assert, target, warnings }) {
+		await tick();
+
+		assert.htmlEqual(target.innerHTML, '<h1>number -> number -> next failed -> ended</h1>');
+
+		assert.deepEqual(normalise_trace_logs(warnings), [
+			{
+				log: 'Detected reactivity loss when reading `values[1]`. This happens when state is read in an async function after an earlier `await`'
+			}
+		]);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-2/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-2/main.svelte
new file mode 100644
index 0000000000..ffe2ef93c0
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-reactivity-loss-for-await-throws-2/main.svelte
@@ -0,0 +1,43 @@
+<script>
+	let values = $state([0, 1, 2]);
+
+	async function get_result() {
+		const logs = [];
+
+		const iterator = {
+			index: 0,
+			async next() {
+				if (this.index > 1) throw new Error('next failed');
+				return { done: false, value: values[this.index++] };
+			},
+			async return() {
+				logs.push('return');
+			},
+			[Symbol.asyncIterator]() {
+				return this;
+			}
+		};
+
+		try {
+			for await (const value of iterator) {
+				logs.push('number');
+				// Read reactive state after async iterator await.
+				values.length === value;
+			}
+			logs.push('done');
+		} catch (error) {
+			logs.push(error.message);
+		}
+
+		logs.push('ended');
+		return logs.join(' -> ');
+	}
+</script>
+
+<svelte:boundary>
+	<h1>{await get_result()}</h1>
+
+	{#snippet pending()}
+		<p>pending</p>
+	{/snippet}
+</svelte:boundary>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/Child.svelte b/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/Child.svelte
new file mode 100644
index 0000000000..6f84dc319e
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/Child.svelte
@@ -0,0 +1,7 @@
+<script>
+	import { push } from "./main.svelte";
+	const x = await push(1);
+	const y = await push(2);
+</script>
+
+{x} {y}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/_config.js b/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/_config.js
new file mode 100644
index 0000000000..a0dc38c660
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/_config.js
@@ -0,0 +1,26 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [show, resolve, count] = target.querySelectorAll('button');
+
+		show.click();
+		await tick();
+		resolve.click();
+		await tick();
+		count.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			'<button>show</button> <button>resolve</button> <button>1</button>'
+		);
+
+		resolve.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			'1 2 <button>show</button> <button>resolve</button> <button>1</button>'
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/main.svelte
new file mode 100644
index 0000000000..0a5346cc47
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-run-isolated-batch/main.svelte
@@ -0,0 +1,23 @@
+<script module>
+	const queued = [];
+	export function push(v) {
+		return new Promise((fulfil) => {
+			queued.push(() => fulfil(v));
+		});
+	}
+</script>
+
+<script>
+	import Child from "./Child.svelte";
+
+	let show = $state(false);
+	let count = $state(0);
+</script>
+
+{#if show}
+	<Child />
+{/if}
+
+<button onclick={() => show = true}>show</button>
+<button onclick={() => queued.shift()?.()}>resolve</button>
+<button onclick={() => count++}>{count}</button>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-4/_config.js b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-4/_config.js
new file mode 100644
index 0000000000..e1555c0062
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-4/_config.js
@@ -0,0 +1,28 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+
+		const [increment, hide, pop] = target.querySelectorAll('button');
+
+		increment.click();
+		await tick();
+		pop.click();
+		await tick();
+		hide.click(); // hides the if block, which cancels the pending async inside, which means the batch can complete
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>increment</button> <button>hide</button> <button>pop</button> 1`
+		);
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>increment</button> <button>hide</button> <button>pop</button> 1`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-4/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-4/main.svelte
new file mode 100644
index 0000000000..5ff3263d39
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-4/main.svelte
@@ -0,0 +1,21 @@
+<script>
+	let show = $state(true);
+	let count = $state(0);
+
+	const queue = [];
+
+	function push(value) {
+		if (!value) return value;
+		return new Promise(r => queue.push(() => r(value)));
+	}
+</script>
+
+<button onclick={() => count += 1}>increment</button>
+<button onclick={() => show = false}>hide</button>
+<!-- pop() so that the outer one resolves first, not the one inside the if block -->
+<button onclick={() => queue.pop()?.()}>pop</button>
+
+{await push(count)}
+{#if show}
+	{await push(count)}
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-5/_config.js b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-5/_config.js
new file mode 100644
index 0000000000..05d92e9df2
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-5/_config.js
@@ -0,0 +1,33 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+
+		const [increment, shift] = target.querySelectorAll('button');
+
+		increment.click();
+		await tick();
+		increment.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>3</button><button>shift</button><p>1 = 1</p><p>fizz: true</p><p>buzz: true</p>`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>3</button><button>shift</button><p>1 = 1</p><p>fizz: true</p><p>buzz: true</p>`
+		);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<button>3</button><button>shift</button><p>3 = 3</p><p>fizz: true</p><p>buzz: false</p>`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-5/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-5/main.svelte
new file mode 100644
index 0000000000..b2a40e65b3
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-5/main.svelte
@@ -0,0 +1,44 @@
+<script>
+	import { getAbortSignal } from 'svelte';
+
+	const queue = [];
+
+	let n = $state(1);
+	let fizz = $state(true);
+	let buzz = $state(true);
+
+	function increment() {
+		n++;
+
+		fizz = n % 3 === 0;
+		buzz = n % 5 === 0;
+	}
+
+	function push(value) {
+		if (value === 1) return 1;
+		const d = Promise.withResolvers();
+
+		queue.push(() => d.resolve(value));
+
+		const signal = getAbortSignal();
+		signal.onabort = () => d.reject(signal.reason);
+
+		return d.promise;
+	}
+</script>
+
+<button onclick={increment}>
+	{$state.eager(n)}
+</button>
+
+<button onclick={() => queue.shift()?.()}>shift</button>
+
+<p>{n} = {await push(n)}</p>
+
+{#if true}
+	<p>fizz: {fizz}</p>
+{/if}
+
+{#if true}
+	<p>buzz: {buzz}</p>
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-6/_config.js b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-6/_config.js
new file mode 100644
index 0000000000..5b951d6c49
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-6/_config.js
@@ -0,0 +1,34 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [button1, button2, pop, shift] = target.querySelectorAll('button');
+		const [p] = target.querySelectorAll('p');
+
+		button1.click();
+		await tick();
+		button2.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `1 + 0 = 1 | 1 0`);
+
+		shift.click();
+		await tick();
+		pop.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `1 + 2 = 3 | 1 1`);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-6/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-6/main.svelte
new file mode 100644
index 0000000000..4515e7a488
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-6/main.svelte
@@ -0,0 +1,21 @@
+<script>
+	const queue1 = [];
+	const queue2 = [];
+
+	let a = $state(0);
+	let b = $state(0);
+	let c = $state(0);
+	let d = $state(0)
+
+	function push(value, where = 1) {
+		if (!value) return value;
+		return new Promise(r => (where === 1 ? queue1 : queue2).push(() => r(value)));
+	}
+</script>
+
+<button onclick={() => {a++;c++}}>a / c</button>
+<button onclick={() => {b+=2;d++}}>b / d</button>
+<button onclick={() => queue1.pop()?.()}>pop 1</button>
+<button onclick={() => queue2.shift()?.()}>shift 2</button>
+
+<p>{a} + {b} = {await push(a + b)} | {await push(c, 2)} {await push(d, 2)}</p>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-7/_config.js b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-7/_config.js
new file mode 100644
index 0000000000..a6f1833d67
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-7/_config.js
@@ -0,0 +1,34 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		await tick();
+		const [button1, button2, shift_1, pop_1, shift_2] = target.querySelectorAll('button');
+		const [p] = target.querySelectorAll('p');
+
+		button1.click();
+		await tick();
+		button2.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
+
+		pop_1.click();
+		await tick();
+		shift_2.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `0 + 0 = 0 | 0 0`);
+
+		// Check that the first batch can still resolve before the second even if one of its async values
+		// is already superseeded (but the subsequent batch as a whole is still pending).
+		shift_1.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `1 + 0 = 1 | 1 0`);
+
+		shift_1.click();
+		await tick();
+		shift_2.click();
+		await tick();
+		assert.htmlEqual(p.innerHTML, `1 + 2 = 3 | 1 1`);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-7/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-7/main.svelte
new file mode 100644
index 0000000000..fec684c257
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-7/main.svelte
@@ -0,0 +1,22 @@
+<script>
+	const queue1 = [];
+	const queue2 = [];
+
+	let a = $state(0);
+	let b = $state(0);
+	let c = $state(0);
+	let d = $state(0)
+
+	function push(value, where = 1) {
+		if (!value) return value;
+		return new Promise(r => (where === 1 ? queue1 : queue2).push(() => r(value)));
+	}
+</script>
+
+<button onclick={() => {a++;c++}}>a / c</button>
+<button onclick={() => {b+=2;d++}}>b / d</button>
+<button onclick={() => queue1.shift()?.()}>shift 1</button>
+<button onclick={() => queue1.pop()?.()}>pop 1</button>
+<button onclick={() => queue2.shift()?.()}>shift 2</button>
+
+<p>{a} + {b} = {await push(a + b)} | {await push(c, 2)} {await push(d, 2)}</p>
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-8/_config.js b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-8/_config.js
new file mode 100644
index 0000000000..fd0fc0de48
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-8/_config.js
@@ -0,0 +1,20 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [increment, pop] = target.querySelectorAll('button');
+
+		increment.click();
+		await tick();
+		increment.click();
+		await tick();
+		pop.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<button>increment</button><button>pop</button> 2 2 1'); // showing nothing here yet would also be ok
+
+		pop.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, '<button>increment</button><button>pop</button> 2 2 1');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-stale-derived-8/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-8/main.svelte
new file mode 100644
index 0000000000..42b7206b56
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-stale-derived-8/main.svelte
@@ -0,0 +1,23 @@
+
+<script>
+	let count = $state(0);
+	let other = $state(0);
+
+	const queue = [];
+
+	function push(v) {
+		if (v === 0) return v;
+
+		return new Promise((resolve) => queue.push(() => resolve(v)));
+	}
+</script>
+
+<button onclick={() => {
+	if (count === 0) other++;
+	count++;
+}}>increment</button>
+<button onclick={() => queue.pop()?.()}>pop</button>
+
+{#if count > 0}
+	{await push(count)} {count} {other}
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-eager-const/_config.js b/packages/svelte/tests/runtime-runes/samples/async-state-eager-const/_config.js
new file mode 100644
index 0000000000..1511d443e5
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-eager-const/_config.js
@@ -0,0 +1,21 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	compileOptions: { dev: true }, // for testing that teardown effect in eager $.get(loaded) doesn't lead to a crash (because it means REACTION_RAN is set, which means unfreeze_derived runs)
+	async test({ assert, target }) {
+		const [count, shift] = target.querySelectorAll('button');
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, `<button>0</button><button>shift</button><p>0</p>`);
+
+		count.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, `<button>1</button><button>shift</button><p>0 (...)</p>`);
+
+		shift.click();
+		await tick();
+		assert.htmlEqual(target.innerHTML, `<button>1</button><button>shift</button><p>1</p>`);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-state-eager-const/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-state-eager-const/main.svelte
new file mode 100644
index 0000000000..f0e2f1cdac
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-state-eager-const/main.svelte
@@ -0,0 +1,21 @@
+<script>
+	let count = $state(0);
+
+	let resolvers = [];
+
+	function push(value) {
+		const { promise, resolve } = Promise.withResolvers();
+		resolvers.push(() => resolve(value));
+		return promise;
+	}
+</script>
+
+<button onclick={() => count += 1}>{$state.eager(count)}</button>
+<button onclick={() => resolvers.shift()?.()}>shift</button>
+
+<svelte:boundary>
+	{@const loaded = $state.eager(count) === count}
+	<p>{await push(count)} {loaded ? '' : '(...)'}</p>
+
+	{#snippet pending()}{/snippet}
+</svelte:boundary>
diff --git a/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/Icon.svelte b/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/Icon.svelte
new file mode 100644
index 0000000000..77cdcabaf7
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/Icon.svelte
@@ -0,0 +1 @@
+<span>x</span>
diff --git a/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/_config.js b/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/_config.js
new file mode 100644
index 0000000000..22412de14d
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/_config.js
@@ -0,0 +1,8 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['client', 'server'],
+
+	html: `<span>x</span>`,
+	ssrHtml: `<span>x</span>`
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/main.svelte b/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/main.svelte
new file mode 100644
index 0000000000..b0f95b2a31
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/dynamic-component-member/main.svelte
@@ -0,0 +1,8 @@
+<script>
+	import Icon from './Icon.svelte';
+
+	let icons = $state({ currency: { Icon } });
+	const platformIcons = $derived(icons);
+</script>
+
+<platformIcons.currency.Icon />
diff --git a/packages/svelte/tests/runtime-runes/samples/store-unsubscribe-not-referenced-after-2/_config.js b/packages/svelte/tests/runtime-runes/samples/store-unsubscribe-not-referenced-after-2/_config.js
new file mode 100644
index 0000000000..d7293f9b70
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/store-unsubscribe-not-referenced-after-2/_config.js
@@ -0,0 +1,54 @@
+import { tick } from 'svelte';
+import { ok, test } from '../../test';
+
+// Test that the store is unsubscribed from, even if it's not referenced once the store itself is set to null
+export default test({
+	skip_no_async: true,
+
+	async test({ target, assert }) {
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="number"> <p>0</p> <button>add watcher</button>`
+		);
+
+		target.querySelector('button')?.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="number"> <p>1</p> hello 1 <button>remove watcher</button>`
+		);
+
+		const input = target.querySelector('input');
+		ok(input);
+
+		input.stepUp();
+		input.dispatchEvent(new Event('input', { bubbles: true }));
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="number"> <p>2</p> hello 2 <button>remove watcher</button>`
+		);
+
+		target.querySelector('button')?.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="number"> <p>2</p> <button>add watcher</button>`
+		);
+
+		input.stepUp();
+		input.dispatchEvent(new Event('input', { bubbles: true }));
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="number"> <p>2</p> <button>add watcher</button>`
+		);
+
+		target.querySelector('button')?.click();
+		await tick();
+		assert.htmlEqual(
+			target.innerHTML,
+			`<input type="number"> <p>3</p> hello 3 <button>remove watcher</button>`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/store-unsubscribe-not-referenced-after-2/main.svelte b/packages/svelte/tests/runtime-runes/samples/store-unsubscribe-not-referenced-after-2/main.svelte
new file mode 100644
index 0000000000..4abfd3c2f9
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/store-unsubscribe-not-referenced-after-2/main.svelte
@@ -0,0 +1,29 @@
+<script>
+	import { writable, derived } from "svelte/store";
+
+	const obj = writable({ a: 1 });
+	let count = $state(0);
+	let watcherA = $state();
+
+	function watch (prop) {
+		return derived(obj, (o) => {
+			count++;
+			return o[prop];
+		});
+	}
+</script>
+
+<input type="number" bind:value={$obj.a}>
+<p>{count}</p>
+
+{#if watcherA}
+	<!-- make sure the presence of async work doesn't break the `legacy_updates` mechanism -->
+	{#if true}
+		{await 'hello'}
+	{/if}
+
+	{$watcherA}
+	<button on:click={() => watcherA = null}>remove watcher</button>
+{:else}
+	<button on:click={() => watcherA = watch("a")}>add watcher</button>
+{/if}
diff --git a/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/Child.svelte b/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/Child.svelte
new file mode 100644
index 0000000000..20bd606d9b
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/Child.svelte
@@ -0,0 +1,10 @@
+<script>
+	import { fly } from 'svelte/transition';
+
+	// Not read before the outro, by which time the derived is destroyed
+	let duration = $derived(10);
+</script>
+
+<div in:fly={{ duration: 10 }} out:fly={{ duration }}>
+	hello
+</div>
diff --git a/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/_config.js b/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/_config.js
new file mode 100644
index 0000000000..734c84a0c4
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/_config.js
@@ -0,0 +1,32 @@
+import { flushSync } from 'svelte';
+import { raf } from '../../../animation-helpers';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [fly_in, fly_out] = target.querySelectorAll('button');
+
+		fly_in.click();
+		flushSync();
+		raf.tick(25);
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>fly in</button>
+				<button>fly out</button>
+				<div style="">hello</div>
+			`
+		);
+
+		fly_out.click();
+		flushSync();
+		raf.tick(50);
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>fly in</button>
+				<button>fly out</button>
+			`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/main.svelte b/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/main.svelte
new file mode 100644
index 0000000000..4fc3395af8
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/transition-derived-uninitialized/main.svelte
@@ -0,0 +1,11 @@
+<script>
+	import Child from './Child.svelte';
+	let show = $state(false);
+</script>
+
+<button onclick={() => (show = true)}>fly in</button>
+<button onclick={() => (show = false)}>fly out</button>
+
+{#if show}
+	<Child />
+{/if}
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_config.js b/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_config.js
new file mode 100644
index 0000000000..aaf40e7a52
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_config.js
@@ -0,0 +1,8 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['async'],
+	compileOptions: {
+		dev: true
+	}
+});
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_expected.html
new file mode 100644
index 0000000000..93016d569c
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_expected.html
@@ -0,0 +1 @@
+<!--[--><img alt="test" src=""/><!--]-->
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_expected_head.html b/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_expected_head.html
new file mode 100644
index 0000000000..96ba2bba28
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/_expected_head.html
@@ -0,0 +1 @@
+<!--1410iyz--><!----><title>Async multiple attributes</title>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/main.svelte
new file mode 100644
index 0000000000..f14ccd088b
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-multiple-attrs/main.svelte
@@ -0,0 +1,15 @@
+<script>
+	const user = $derived(Promise.resolve({ 
+		name: 'test',
+		image: '',
+	}))
+</script>
+
+<svelte:head>
+<title>Async multiple attributes</title>
+</svelte:head>
+
+<img
+	alt={(await user).name}
+	src={(await user).image}
+/>
diff --git a/packages/svelte/tests/server-side-rendering/samples/spread-attributes-event-handler-xss/main.svelte b/packages/svelte/tests/server-side-rendering/samples/spread-attributes-event-handler-xss/main.svelte
index 2a8c17f048..e47a19408e 100644
--- a/packages/svelte/tests/server-side-rendering/samples/spread-attributes-event-handler-xss/main.svelte
+++ b/packages/svelte/tests/server-side-rendering/samples/spread-attributes-event-handler-xss/main.svelte
@@ -5,7 +5,12 @@
 		onclick: 'alert(1)',
 		onerror: 'alert(1)',
 		onfocus: 'alert(1)',
-		onmouseover: 'alert(1)'
+		onmouseover: 'alert(1)',
+		' onload': 'alert(1)',
+		'\tonload': 'alert(1)',
+		'\u00a0onload': 'alert(1)',
+		"\t": "/onmouseover=alert(1)//",
+		"": "/onmouseover=alert(1)//"
 	};
 </script>
 
diff --git a/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/client/index.svelte.js b/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/client/index.svelte.js
index 5281a86582..837a7cd65a 100644
--- a/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/client/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/client/index.svelte.js
@@ -1,9 +1,9 @@
 import 'svelte/internal/disclose-version';
 import * as $ from 'svelte/internal/client';
 
-var root = $.from_html(`<h1></h1> <b></b> <button> </button> <h1></h1>`, 1);
+var root = $.from_html(`<h1></h1> <b></b> <button> </button> <h1></h1> <div></div>`, 1);
 
-export default function Nullish_coallescence_omittance($$anchor) {
+export default function Nullish_coallescence_omittance($$anchor, $$props) {
 	let name = 'world';
 	let count = $.state(0);
 	var fragment = root();
@@ -23,7 +23,14 @@ export default function Nullish_coallescence_omittance($$anchor) {
 	var h1_1 = $.sibling(button, 2);
 
 	h1_1.textContent = 'Hello, world';
-	$.template_effect(() => $.set_text(text, `Count is ${$.get(count) ?? ''}`));
+
+	var div = $.sibling(h1_1, 2);
+
+	$.template_effect(() => {
+		$.set_text(text, `Count is ${$.get(count) ?? ''}`);
+		$.set_attribute(div, 'title', `Hello, world ${$.get(count) ?? ''}  1  ${typeof $$props.value} ${$$props.value ?? ''}`);
+	});
+
 	$.delegated('click', button, () => $.update(count));
 	$.append($$anchor, fragment);
 }
diff --git a/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/server/index.svelte.js
index a7e580acb8..357a887c9b 100644
--- a/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/server/index.svelte.js
@@ -1,8 +1,9 @@
 import * as $ from 'svelte/internal/server';
 
-export default function Nullish_coallescence_omittance($$renderer) {
+export default function Nullish_coallescence_omittance($$renderer, $$props) {
 	let name = 'world';
 	let count = 0;
+	let { value } = $$props;
 
-	$$renderer.push(`<h1>Hello, world!</h1> <b>123</b> <button>Count is ${$.escape(count)}</button> <h1>Hello, world</h1>`);
+	$$renderer.push(`<h1>Hello, world!</h1> <b>123</b> <button>Count is ${$.escape(count)}</button> <h1>Hello, world</h1> <div${$.attr('title', `Hello, world ${$.stringify(count)}  1  ${typeof value} ${$.stringify(value)}`)}></div>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/index.svelte b/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/index.svelte
index a67c574fee..ed88f5a269 100644
--- a/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/index.svelte
+++ b/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/index.svelte
@@ -1,8 +1,10 @@
 <script>
     let name = 'world';
     let count = $state(0);
+    let { value } = $props();
 </script>
 <h1>Hello, {null}{name}!</h1>
 <b>{1 ?? 'stuff'}{2 ?? 'more stuff'}{3 ?? 'even more stuff'}</b>
 <button onclick={()=>count++}>Count is {count}</button>
-<h1>Hello, {name ?? 'earth' ?? null}</h1>
\ No newline at end of file
+<h1>Hello, {name ?? 'earth' ?? null}</h1>
+<div title="Hello, {name} {count} {null} {1} {undefined} {typeof value} {value}"></div>
diff --git a/playgrounds/sandbox/ssr-dev.js b/playgrounds/sandbox/ssr-dev.js
index 8a0c063d47..b770848ad1 100644
--- a/playgrounds/sandbox/ssr-dev.js
+++ b/playgrounds/sandbox/ssr-dev.js
@@ -29,8 +29,9 @@ polka()
 		const { head, body } = await render(App);
 
 		const html = transformed_template
-			.replace(`<!--ssr-head-->`, head)
-			.replace(`<!--ssr-body-->`, body)
+			// use function form to prevent any string replacement characters from being interpreted
+			.replace(`<!--ssr-head-->`, () => head)
+			.replace(`<!--ssr-body-->`, () => body)
 			// check that Safari doesn't break hydration
 			.replaceAll('+636-555-3226', '<a href="tel:+636-555-3226">+636-555-3226</a>');
 
diff --git a/playgrounds/sandbox/ssr-prod.js b/playgrounds/sandbox/ssr-prod.js
index 0c760188d4..e3ece4d5be 100644
--- a/playgrounds/sandbox/ssr-prod.js
+++ b/playgrounds/sandbox/ssr-prod.js
@@ -9,8 +9,9 @@ const { head, body } = await render(App);
 
 const rendered = fs
 	.readFileSync(path.resolve('./dist/client/index.html'), 'utf-8')
-	.replace(`<!--ssr-body-->`, body)
-	.replace(`<!--ssr-head-->`, head);
+	// use function form to prevent any string replacement characters from being interpreted
+	.replace(`<!--ssr-body-->`, () => body)
+	.replace(`<!--ssr-head-->`, () => head);
 
 const types = {
 	'.js': 'application/javascript',
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 0e2be208b6..1bfee5c769 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -96,8 +96,8 @@ importers:
         specifier: ^2.1.1
         version: 2.1.1
       devalue:
-        specifier: ^5.6.4
-        version: 5.6.4
+        specifier: ^5.8.1
+        version: 5.8.1
       esm-env:
         specifier: ^1.2.1
         version: 1.2.1
@@ -1418,8 +1418,8 @@ packages:
     engines: {node: '>=0.10'}
     hasBin: true
 
-  devalue@5.6.4:
-    resolution: {integrity: sha512-Gp6rDldRsFh/7XuouDbxMH3Mx8GMCcgzIb1pDTvNyn8pZGQ22u+Wa+lGV9dQCltFQ7uVw0MhRyb8XDskNFOReA==}
+  devalue@5.8.1:
+    resolution: {integrity: sha512-4CXDYRBGqN+57wVJkuXBYmpAVUSg3L6JAQa/DFqm238G73E1wuyc/JhGQJzN7vUf/CMphYau2zXbfWzDR5aTEw==}
 
   dir-glob@3.0.1:
     resolution: {integrity: sha512-WkrWp9GR4KXfKGYzOLmTuGVi1UWFfws377n9cc55/tb6DuqyF6pcQ5AbiHEshaDpY9v6oaSr2XCDidGmMwdzIA==}
@@ -3786,7 +3786,7 @@ snapshots:
   detect-libc@1.0.3:
     optional: true
 
-  devalue@5.6.4: {}
+  devalue@5.8.1: {}
 
   dir-glob@3.0.1:
     dependencies: