diff --git a/.changeset/easy-paths-take.md b/.changeset/easy-paths-take.md
new file mode 100644
index 0000000000..1378322abe
--- /dev/null
+++ b/.changeset/easy-paths-take.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: take into account static blocks when determining transition locality
diff --git a/.changeset/huge-poets-tickle.md b/.changeset/huge-poets-tickle.md
new file mode 100644
index 0000000000..f2b1ba6f25
--- /dev/null
+++ b/.changeset/huge-poets-tickle.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: coordinate mount of snippets with await expressions
diff --git a/.changeset/odd-plants-lead.md b/.changeset/odd-plants-lead.md
new file mode 100644
index 0000000000..1df2236c2a
--- /dev/null
+++ b/.changeset/odd-plants-lead.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: better optimization of await expressions
diff --git a/.changeset/slimy-turtles-yell.md b/.changeset/slimy-turtles-yell.md
new file mode 100644
index 0000000000..e3f3a66264
--- /dev/null
+++ b/.changeset/slimy-turtles-yell.md
@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: flush pending changes after rendering `failed` snippet
diff --git a/packages/svelte/src/compiler/phases/2-analyze/index.js b/packages/svelte/src/compiler/phases/2-analyze/index.js
index 52be997374..b4c704c34d 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/index.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/index.js
@@ -6,7 +6,7 @@ import { walk } from 'zimmerframe';
 import { parse } from '../1-parse/acorn.js';
 import * as e from '../../errors.js';
 import * as w from '../../warnings.js';
-import { extract_identifiers } from '../../utils/ast.js';
+import { extract_identifiers, has_await_expression } from '../../utils/ast.js';
 import * as b from '#compiler/builders';
 import { Scope, ScopeRoot, create_scopes, get_rune, set_scope } from '../scope.js';
 import check_graph_for_cycles from './utils/check_graph_for_cycles.js';
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 f5132c1cf8..92653ed73c 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 } from '../../../../../utils/ast.js';
+import { has_await_expression } from '../../../../../utils/ast.js';
 
 /** Opens an if/each block, so that we can remove nodes in the case of a mismatch */
 export const block_open = b.literal(BLOCK_OPEN);
@@ -315,7 +315,7 @@ export class PromiseOptimiser {
 
 		const promises = b.array(
 			this.expressions.map((expression) => {
-				return expression.type === 'AwaitExpression' && !has_await(expression.argument)
+				return expression.type === 'AwaitExpression' && !has_await_expression(expression.argument)
 					? expression.argument
 					: b.call(b.thunk(expression, true));
 			})
diff --git a/packages/svelte/src/compiler/utils/ast.js b/packages/svelte/src/compiler/utils/ast.js
index 541921befb..bd92dda5d9 100644
--- a/packages/svelte/src/compiler/utils/ast.js
+++ b/packages/svelte/src/compiler/utils/ast.js
@@ -611,16 +611,20 @@ export function build_assignment_value(operator, left, right) {
 }
 
 /**
- * @param {ESTree.Expression} expression
+ * @param {ESTree.Node} node
  */
-export function has_await(expression) {
+export function has_await_expression(node) {
 	let has_await = false;
 
-	walk(expression, null, {
+	walk(node, null, {
 		AwaitExpression(_node, context) {
 			has_await = true;
 			context.stop();
-		}
+		},
+		// don't traverse into these
+		FunctionDeclaration() {},
+		FunctionExpression() {},
+		ArrowFunctionExpression() {}
 	});
 
 	return has_await;
diff --git a/packages/svelte/src/compiler/utils/builders.js b/packages/svelte/src/compiler/utils/builders.js
index 99306ce4d9..f21b0dc8b4 100644
--- a/packages/svelte/src/compiler/utils/builders.js
+++ b/packages/svelte/src/compiler/utils/builders.js
@@ -2,7 +2,7 @@
 import { walk } from 'zimmerframe';
 import { regex_is_valid_identifier } from '../phases/patterns.js';
 import { sanitize_template_string } from './sanitize_template_string.js';
-import { has_await } from './ast.js';
+import { has_await_expression } from './ast.js';
 
 /**
  * @param {Array<ESTree.Expression | ESTree.SpreadElement | null>} elements
@@ -451,7 +451,7 @@ export function thunk(expression, async = false) {
 export function unthunk(expression) {
 	// optimize `async () => await x()`, but not `async () => await x(await y)`
 	if (expression.async && expression.body.type === 'AwaitExpression') {
-		if (!has_await(expression.body.argument)) {
+		if (!has_await_expression(expression.body.argument)) {
 			return unthunk(arrow(expression.params, expression.body.argument));
 		}
 	}
diff --git a/packages/svelte/src/internal/client/constants.js b/packages/svelte/src/internal/client/constants.js
index 0fb4a44389..24dc9e4fb8 100644
--- a/packages/svelte/src/internal/client/constants.js
+++ b/packages/svelte/src/internal/client/constants.js
@@ -14,7 +14,10 @@ export const DESTROYED = 1 << 14;
 
 // Flags exclusive to effects
 export const EFFECT_RAN = 1 << 15;
-/** 'Transparent' effects do not create a transition boundary */
+/**
+ * 'Transparent' effects do not create a transition boundary.
+ * This is on a block effect 99% of the time but may also be on a branch effect if its parent block effect was pruned
+ */
 export const EFFECT_TRANSPARENT = 1 << 16;
 export const EAGER_EFFECT = 1 << 17;
 export const HEAD_EFFECT = 1 << 18;
diff --git a/packages/svelte/src/internal/client/dom/blocks/boundary.js b/packages/svelte/src/internal/client/dom/blocks/boundary.js
index 3da9204571..febbc00898 100644
--- a/packages/svelte/src/internal/client/dom/blocks/boundary.js
+++ b/packages/svelte/src/internal/client/dom/blocks/boundary.js
@@ -30,7 +30,6 @@ import {
 	skip_nodes,
 	set_hydrate_node
 } from '../hydration.js';
-import { get_next_sibling } from '../operations.js';
 import { queue_micro_task } from '../task.js';
 import * as e from '../../errors.js';
 import * as w from '../../warnings.js';
@@ -39,6 +38,7 @@ import { Batch, effect_pending_updates } 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';
 
 /**
  * @typedef {{
@@ -93,6 +93,9 @@ export class Boundary {
 	/** @type {DocumentFragment | null} */
 	#offscreen_fragment = null;
 
+	/** @type {TemplateNode | null} */
+	#pending_anchor = null;
+
 	#local_pending_count = 0;
 	#pending_count = 0;
 
@@ -156,8 +159,10 @@ export class Boundary {
 					this.#hydrate_resolved_content();
 				}
 			} else {
+				var anchor = this.#get_anchor();
+
 				try {
-					this.#main_effect = branch(() => children(this.#anchor));
+					this.#main_effect = branch(() => children(anchor));
 				} catch (error) {
 					this.error(error);
 				}
@@ -168,6 +173,10 @@ export class Boundary {
 					this.#pending = false;
 				}
 			}
+
+			return () => {
+				this.#pending_anchor?.remove();
+			};
 		}, flags);
 
 		if (hydrating) {
@@ -195,9 +204,11 @@ export class Boundary {
 		this.#pending_effect = branch(() => pending(this.#anchor));
 
 		Batch.enqueue(() => {
+			var anchor = this.#get_anchor();
+
 			this.#main_effect = this.#run(() => {
 				Batch.ensure();
-				return branch(() => this.#children(this.#anchor));
+				return branch(() => this.#children(anchor));
 			});
 
 			if (this.#pending_count > 0) {
@@ -212,6 +223,19 @@ export class Boundary {
 		});
 	}
 
+	#get_anchor() {
+		var anchor = this.#anchor;
+
+		if (this.#pending) {
+			this.#pending_anchor = create_text();
+			this.#anchor.before(this.#pending_anchor);
+
+			anchor = this.#pending_anchor;
+		}
+
+		return anchor;
+	}
+
 	/**
 	 * Returns `true` if the effect exists inside a boundary whose pending snippet is shown
 	 * @returns {boolean}
@@ -253,6 +277,7 @@ export class Boundary {
 
 		if (this.#main_effect !== null) {
 			this.#offscreen_fragment = document.createDocumentFragment();
+			this.#offscreen_fragment.append(/** @type {TemplateNode} */ (this.#pending_anchor));
 			move_effect(this.#main_effect, this.#offscreen_fragment);
 		}
 
@@ -402,6 +427,7 @@ export class Boundary {
 		if (failed) {
 			queue_micro_task(() => {
 				this.#failed_effect = this.#run(() => {
+					Batch.ensure();
 					this.#is_creating_fallback = true;
 
 					try {
diff --git a/packages/svelte/src/internal/client/reactivity/effects.js b/packages/svelte/src/internal/client/reactivity/effects.js
index bd262258dc..4235e9cb24 100644
--- a/packages/svelte/src/internal/client/reactivity/effects.js
+++ b/packages/svelte/src/internal/client/reactivity/effects.js
@@ -149,6 +149,9 @@ function create_effect(type, fn, sync, push = true) {
 			(e.f & EFFECT_PRESERVED) === 0
 		) {
 			e = e.first;
+			if ((type & BLOCK_EFFECT) !== 0 && (type & EFFECT_TRANSPARENT) !== 0 && e !== null) {
+				e.f |= EFFECT_TRANSPARENT;
+			}
 		}
 
 		if (e !== null) {
@@ -604,7 +607,12 @@ export function pause_children(effect, transitions, local) {
 
 	while (child !== null) {
 		var sibling = child.next;
-		var transparent = (child.f & EFFECT_TRANSPARENT) !== 0 || (child.f & BRANCH_EFFECT) !== 0;
+		var transparent =
+			(child.f & EFFECT_TRANSPARENT) !== 0 ||
+			// If this is a branch effect without a block effect parent,
+			// it means the parent block effect was pruned. In that case,
+			// transparency information was transferred to the branch effect.
+			((child.f & BRANCH_EFFECT) !== 0 && (effect.f & BLOCK_EFFECT) !== 0);
 		// TODO we don't need to call pause_children recursively with a linked list in place
 		// it's slightly more involved though as we have to account for `transparent` changing
 		// through the tree.
diff --git a/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/Child.svelte b/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/Child.svelte
new file mode 100644
index 0000000000..7085219a5a
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/Child.svelte
@@ -0,0 +1,7 @@
+<script>
+	let { children, push } = $props();
+	let message = await push('hello from child');
+</script>
+
+<p>message: {message}</p>
+{@render children()}
diff --git a/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/_config.js b/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/_config.js
new file mode 100644
index 0000000000..b6ca2ae3d2
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/_config.js
@@ -0,0 +1,25 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const [shift] = target.querySelectorAll('button');
+
+		shift.click();
+		await tick();
+
+		assert.htmlEqual(target.innerHTML, `<button>shift</button><p>loading...</p>`);
+
+		shift.click();
+		await tick();
+
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+				<button>shift</button>
+				<p>message: hello from child</p>
+				<p>hello from parent</p>
+			`
+		);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/main.svelte
new file mode 100644
index 0000000000..3ad2c9572a
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-snippet-coordinated-mount/main.svelte
@@ -0,0 +1,21 @@
+<script>
+	import Child from './Child.svelte';
+	const resolvers = [];
+	function push(value) {
+		const { promise, resolve } = Promise.withResolvers();
+		resolvers.push(() => resolve(value));
+		return promise;
+	}
+</script>
+
+<button onclick={() => resolvers.shift()?.()}>shift</button>
+
+<svelte:boundary>
+	<Child {push}>
+		<p>{await push('hello from parent')}</p>
+	</Child>
+
+	{#snippet pending()}
+		<p>loading...</p>
+	{/snippet}
+</svelte:boundary>
diff --git a/packages/svelte/tests/runtime-runes/samples/error-boundary-23/_config.js b/packages/svelte/tests/runtime-runes/samples/error-boundary-23/_config.js
new file mode 100644
index 0000000000..7a6a66eb66
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/error-boundary-23/_config.js
@@ -0,0 +1,12 @@
+import { tick } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target, logs }) {
+		const btn = target.querySelector('button');
+		btn?.click();
+		await tick();
+
+		assert.deepEqual(logs, ['attachment']);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/error-boundary-23/main.svelte b/packages/svelte/tests/runtime-runes/samples/error-boundary-23/main.svelte
new file mode 100644
index 0000000000..c1fe20d931
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/error-boundary-23/main.svelte
@@ -0,0 +1,20 @@
+<script>
+	let fail = $state(false);
+
+	function error() {
+		throw new Error('oops');
+	}
+
+	function attachment() {
+		console.log('attachment');
+	}
+</script>
+
+<svelte:boundary>
+	{fail ? error() : 'all good'}
+	<button onclick={() => fail = true}>fail</button>
+	
+	{#snippet failed()}
+		<div {@attach attachment}>oops!</div>
+	{/snippet}
+</svelte:boundary>
diff --git a/packages/svelte/tests/runtime-runes/samples/transition-if-nested-static/_config.js b/packages/svelte/tests/runtime-runes/samples/transition-if-nested-static/_config.js
new file mode 100644
index 0000000000..900d6daff8
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/transition-if-nested-static/_config.js
@@ -0,0 +1,22 @@
+import { flushSync } from 'svelte';
+import { test } from '../../test';
+
+export default test({
+	async test({ assert, target }) {
+		const btn = target.querySelector('button');
+
+		btn?.click();
+		flushSync();
+		assert.htmlEqual(
+			target.innerHTML,
+			`
+			<button>Toggle</button>
+			<div>Should not transition out</div>
+		`
+		);
+
+		btn?.click();
+		flushSync();
+		assert.htmlEqual(target.innerHTML, '<button>Toggle</button>');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/transition-if-nested-static/main.svelte b/packages/svelte/tests/runtime-runes/samples/transition-if-nested-static/main.svelte
new file mode 100644
index 0000000000..84f6ee77af
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/transition-if-nested-static/main.svelte
@@ -0,0 +1,18 @@
+
+<script>
+	import { slide } from 'svelte/transition';
+	let showText = $state(false);
+	let show = $state(true);
+</script>
+
+<button onclick={() => showText = !showText}>
+	Toggle
+</button>
+
+{#if showText}
+	{#if show}
+		<div transition:slide>
+			Should not transition out
+		</div>
+	{/if}
+{/if}