From b8fd326d96c3a57feff3a4fafcd2d1651001b109 Mon Sep 17 00:00:00 2001
From: Elliott Johnson <sejohnson@torchcloudconsulting.com>
Date: Wed, 17 Sep 2025 15:49:57 -0600
Subject: [PATCH] feat: async SSR (#16748)

* feat: First pass at payload

* first crack

* snapshots

* checkpoint

* fix: cloning

* add test option

* big dumb

* today's hard work; few tests left to fix

* improve

* tests passing no wayyyyy yo

* lots of progress, couple of failing tests around selects

* meh

* solve async tree stuff

* fix select/option stuff

* whoop, tests

* simplify

* feat: hoisting

* fix: `$effect.pending` sends updates to incorrect boundary

* changeset

* stuff from upstream

* feat: first hydrationgaa

* remove docs

* snapshots

* silly fix

* checkpoint

* meh

* ALKASJDFALSKDFJ the test passes

* chore: Update a bunch of tests for hydration markers

* chore: remove snippet and is_async

* naming

* better errors for sync-in-async

* test improvements

* idk man

* merge local branches (#16757)

* use fragment as async hoist boundary

* remove async_hoist_boundary

* only dewaterfall when necessary

* unused

* simplify/fix

* de-waterfall awaits in separate elements

* update snapshots

* remove unnecessary wrapper

* fix

* fix

* remove suspends_without_fallback

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>

* Update payload.js

Co-authored-by: Rich Harris <rich.harris@vercel.com>

* checkpoint

* got the extra children to go away

* just gonna go ahead and merge this as the review comments take up too much space

* chore: remove hoisted_promises (#16766)

* chore: remove hoisted_promises

* WIP optimise promises

* WIP

* fix <slot> with await in prop

* tweak

* fix type error

* Update packages/svelte/src/compiler/phases/3-transform/server/visitors/SvelteHead.js

* chore: fix hydration treeshaking (#16767)

* chore: fix hydration treeshaking

* fix

* remove await_outside_boundary error (#16762)

* chore: remove unused analysis.boundary (#16763)

* chore: simplify slots (#16765)

* chore: simplify slots

* unused

* Apply suggestions from code review

* chore: remove metadata.pending (#16764)

* Update packages/svelte/src/compiler/phases/3-transform/server/visitors/SnippetBlock.js

* put this back where it was, keep the diff small

* Update packages/svelte/src/compiler/phases/types.d.ts

Co-authored-by: Rich Harris <rich.harris@vercel.com>

* chore: remove analysis.state.title (#16771)

* chore: remove analysis.state.title

* unused

* chore: remove is_async (#16769)

* chore: remove is_async

* unused

* Apply suggestions from code review

Co-authored-by: Rich Harris <rich.harris@vercel.com>

* cleanup

* lint

* clean up payload a bit

* compiler work

* run ssr on sync and async

* prettier

* inline capture

* Update packages/svelte/src/compiler/phases/3-transform/server/visitors/EachBlock.js

* chore: simplify build_template (#16780)

* small tweak to aid greppability

* chore: fix SSR context (#16781)

* at least passing

* cleanup

* fix

* remove push/pop from exports, not needed with payload

* I think this is better but tbh not sure

* async SSR

* qualification

* errors:

* I have lost the plot

* finally

* ugh

* tweak error codes to better align with existing conventions, such as they are

* tweak messages

* remove unused args

* DRY out a bit

* unused

* unused

* unused

* simplify - we can enforce readonly at a type level

* unused

* simplify

* avoid magical accessors

* simplify algorithm

* unused

* unused

* reduce indirection

* TreeState -> SSRState

* mark deprecated methods

* grab this.local from parent directly

* rename render -> fn per conventions (fn indicates 'arbitrary code')

* reduce indirection

* Revert "reduce indirection"

This reverts commit 3ec461baad451654db6d518734aeeb7b366f7c2e.

* tweak

* okay works this time

* no way chat, it works

* fix context stuff

* tweak

* make it chainable

* lint

* clean up

* lint

* Update packages/svelte/src/internal/server/types.d.ts

Co-authored-by: Rich Harris <rich.harris@vercel.com>

* sunset html for async

* types

* we use 'deprecated' in other messages

* oops

---------

Co-authored-by: Rich Harris <rich.harris@vercel.com>
---
 .changeset/forty-insects-cheat.md             |   5 +
 .prettierignore                               |   1 +
 .../98-reference/.generated/server-errors.md  |  14 +
 .../.generated/server-warnings.md             |   9 +
 .../98-reference/.generated/shared-errors.md  |  20 -
 eslint.config.js                              |   1 +
 .../svelte/messages/server-errors/errors.md   |  15 +
 .../messages/server-errors/lifecycle.md       |   5 -
 .../messages/server-warnings/warnings.md      |   5 +
 .../svelte/messages/shared-errors/errors.md   |  18 -
 .../svelte/scripts/process-messages/index.js  |   1 +
 .../templates/server-warnings.js              |  20 +
 .../compiler/phases/1-parse/state/element.js  |   3 +-
 .../src/compiler/phases/2-analyze/index.js    |  15 +-
 .../src/compiler/phases/2-analyze/types.d.ts  |   5 +
 .../2-analyze/visitors/AwaitExpression.js     | 122 +++-
 .../2-analyze/visitors/CallExpression.js      |   1 +
 .../phases/2-analyze/visitors/ConstTag.js     |   6 +-
 .../2-analyze/visitors/RegularElement.js      |   2 +-
 .../2-analyze/visitors/VariableDeclarator.js  |   6 +
 .../3-transform/client/transform-client.js    |   2 -
 .../phases/3-transform/client/types.d.ts      |   8 +-
 .../client/visitors/AwaitExpression.js        | 106 +--
 .../client/visitors/CallExpression.js         |   4 +-
 .../3-transform/client/visitors/ConstTag.js   |   9 +-
 .../client/visitors/RegularElement.js         |  41 +-
 .../client/visitors/VariableDeclaration.js    |  14 +-
 .../3-transform/server/transform-server.js    |  26 +-
 .../3-transform/server/visitors/AwaitBlock.js |  38 +-
 .../server/visitors/AwaitExpression.js        |  22 +-
 .../3-transform/server/visitors/EachBlock.js  |  27 +-
 .../3-transform/server/visitors/IfBlock.js    |  22 +-
 .../server/visitors/RegularElement.js         |  76 ++-
 .../server/visitors/SlotElement.js            |  27 +-
 .../server/visitors/SvelteBoundary.js         |  26 +-
 .../server/visitors/TitleElement.js           |   4 +-
 .../server/visitors/shared/component.js       |  60 +-
 .../server/visitors/shared/utils.js           | 149 +++--
 .../svelte/src/compiler/phases/types.d.ts     |   4 +-
 .../svelte/src/compiler/types/template.d.ts   |   2 +
 packages/svelte/src/compiler/utils/ast.js     |  16 +
 .../svelte/src/compiler/utils/builders.js     |  12 +-
 packages/svelte/src/index-server.js           |   8 +-
 .../internal/client/dom/blocks/boundary.js    | 106 +--
 .../src/internal/client/reactivity/async.js   |   3 +-
 packages/svelte/src/internal/client/render.js |  55 +-
 .../src/internal/server/blocks/snippet.js     |   2 +-
 .../svelte/src/internal/server/context.js     |  58 +-
 packages/svelte/src/internal/server/dev.js    |  46 +-
 packages/svelte/src/internal/server/errors.js |  24 +
 packages/svelte/src/internal/server/index.js  | 232 ++++---
 .../svelte/src/internal/server/payload.js     | 625 ++++++++++++++++--
 .../src/internal/server/payload.test.ts       | 364 ++++++++++
 .../svelte/src/internal/server/types.d.ts     |  23 +-
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 packages/svelte/src/internal/shared/errors.js |  16 -
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 .../tests/runtime-browser/driver-ssr.js       |   6 +-
 .../after-render-prevents-loop/_config.js     |   2 +-
 .../after-render-triggers-update/_config.js   |   2 +-
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 .../_config.js                                |  18 +-
 .../_config.js                                |   6 +-
 .../samples/binding-select-late-2/_config.js  |   6 +-
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 .../binding-select-unmatched-2/_config.js     |  30 +-
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 .../_config.js                                |   2 +-
 .../samples/textarea-content/_config.js       |   4 +-
 .../svelte/tests/runtime-legacy/shared.ts     |  53 +-
 .../async-no-pending-throws-sync/_config.js   |   7 +
 .../async-no-pending-throws-sync/main.svelte  |   1 +
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 .../samples/async-no-pending/main.svelte      |   1 +
 .../samples/async-ondestroy-ordering/A.svelte |   9 +
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 .../samples/snippet-slot-let-error/_config.js |   1 +
 .../_config.js                                |   6 +
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 .../A.svelte                                  |   9 +
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 .../_config.js                                |   3 +
 .../_expected.html                            |   0
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 .../async-if-alternate-hoisting/main.svelte   |   5 +
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 .../samples/comment-preserve/_expected.html   |   2 +-
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 .../_expected.html                            |   2 +
 .../invalid-nested-svelte-element/_config.js  |   4 +-
 .../tests/server-side-rendering/test.ts       | 146 ++--
 .../async-each-fallback-hoisting/_config.js   |   3 +
 .../_expected/client/index.svelte.js          |  35 +
 .../_expected/server/index.svelte.js          |  25 +
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 .../samples/async-each-hoisting/index.svelte  |   9 +
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 .../_expected/client/index.svelte.js          |  30 +
 .../_expected/server/index.svelte.js          |  16 +
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 .../hmr/_expected/server/index.svelte.js      |   2 +-
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 .../purity/_expected/server/index.svelte.js   |   4 +-
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 .../_expected/server/index.svelte.js          |   2 +-
 packages/svelte/types/index.d.ts              |   4 +-
 playgrounds/sandbox/package.json              |   3 +-
 181 files changed, 2638 insertions(+), 901 deletions(-)
 create mode 100644 .changeset/forty-insects-cheat.md
 create mode 100644 documentation/docs/98-reference/.generated/server-warnings.md
 create mode 100644 packages/svelte/messages/server-errors/errors.md
 delete mode 100644 packages/svelte/messages/server-errors/lifecycle.md
 create mode 100644 packages/svelte/messages/server-warnings/warnings.md
 create mode 100644 packages/svelte/scripts/process-messages/templates/server-warnings.js
 create mode 100644 packages/svelte/src/internal/server/payload.test.ts
 create mode 100644 packages/svelte/src/internal/server/warnings.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-no-pending-throws-sync/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-no-pending-throws-sync/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-no-pending/_config.js
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-no-pending/main.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/A.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/B.svelte
 create mode 100644 packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/C.svelte
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diff --git a/.changeset/forty-insects-cheat.md b/.changeset/forty-insects-cheat.md
new file mode 100644
index 0000000000..993a8fdb24
--- /dev/null
+++ b/.changeset/forty-insects-cheat.md
@@ -0,0 +1,5 @@
+---
+'svelte': minor
+---
+
+feat: experimental async SSR
diff --git a/.prettierignore b/.prettierignore
index 5e1d9b1aa7..9cf9a4bfe1 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -15,6 +15,7 @@ packages/svelte/src/internal/client/warnings.js
 packages/svelte/src/internal/shared/errors.js
 packages/svelte/src/internal/shared/warnings.js
 packages/svelte/src/internal/server/errors.js
+packages/svelte/src/internal/server/warnings.js
 packages/svelte/tests/migrate/samples/*/output.svelte
 packages/svelte/tests/**/*.svelte
 packages/svelte/tests/**/_expected*
diff --git a/documentation/docs/98-reference/.generated/server-errors.md b/documentation/docs/98-reference/.generated/server-errors.md
index c3e8b53c31..6263032212 100644
--- a/documentation/docs/98-reference/.generated/server-errors.md
+++ b/documentation/docs/98-reference/.generated/server-errors.md
@@ -1,5 +1,19 @@
 <!-- This file is generated by scripts/process-messages/index.js. Do not edit! -->
 
+### await_invalid
+
+```
+Encountered asynchronous work while rendering synchronously.
+```
+
+You (or the framework you're using) called [`render(...)`](svelte-server#render) with a component containing an `await` expression. Either `await` the result of `render` or wrap the `await` (or the component containing it) in a [`<svelte:boundary>`](svelte-boundary) with a `pending` snippet.
+
+### html_deprecated
+
+```
+The `html` property of server render results has been deprecated. Use `body` instead.
+```
+
 ### lifecycle_function_unavailable
 
 ```
diff --git a/documentation/docs/98-reference/.generated/server-warnings.md b/documentation/docs/98-reference/.generated/server-warnings.md
new file mode 100644
index 0000000000..26b3628be9
--- /dev/null
+++ b/documentation/docs/98-reference/.generated/server-warnings.md
@@ -0,0 +1,9 @@
+<!-- This file is generated by scripts/process-messages/index.js. Do not edit! -->
+
+### experimental_async_ssr
+
+```
+Attempted to use asynchronous rendering without `experimental.async` enabled
+```
+
+Set `experimental.async: true` in your compiler options (usually in `svelte.config.js`) to use async server rendering. This render ran synchronously.
diff --git a/documentation/docs/98-reference/.generated/shared-errors.md b/documentation/docs/98-reference/.generated/shared-errors.md
index de34b3f5da..6c31aaafd0 100644
--- a/documentation/docs/98-reference/.generated/shared-errors.md
+++ b/documentation/docs/98-reference/.generated/shared-errors.md
@@ -1,25 +1,5 @@
 <!-- This file is generated by scripts/process-messages/index.js. Do not edit! -->
 
-### await_outside_boundary
-
-```
-Cannot await outside a `<svelte:boundary>` with a `pending` snippet
-```
-
-The `await` keyword can only appear in a `$derived(...)` or template expression, or at the top level of a component's `<script>` block, if it is inside a [`<svelte:boundary>`](/docs/svelte/svelte-boundary) that has a `pending` snippet:
-
-```svelte
-<svelte:boundary>
-	<p>{await getData()}</p>
-
-	{#snippet pending()}
-		<p>loading...</p>
-	{/snippet}
-</svelte:boundary>
-```
-
-This restriction may be lifted in a future version of Svelte.
-
 ### invalid_default_snippet
 
 ```
diff --git a/eslint.config.js b/eslint.config.js
index 5241cb43a6..0e0e0bc729 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -94,6 +94,7 @@ export default [
 			'packages/svelte/src/internal/client/errors.js',
 			'packages/svelte/src/internal/client/warnings.js',
 			'packages/svelte/src/internal/shared/warnings.js',
+			'packages/svelte/src/internal/server/warnings.js',
 			'packages/svelte/compiler/index.js',
 			// stuff we don't want to lint
 			'benchmarking/**',
diff --git a/packages/svelte/messages/server-errors/errors.md b/packages/svelte/messages/server-errors/errors.md
new file mode 100644
index 0000000000..49d2a310f6
--- /dev/null
+++ b/packages/svelte/messages/server-errors/errors.md
@@ -0,0 +1,15 @@
+## await_invalid
+
+> Encountered asynchronous work while rendering synchronously.
+
+You (or the framework you're using) called [`render(...)`](svelte-server#render) with a component containing an `await` expression. Either `await` the result of `render` or wrap the `await` (or the component containing it) in a [`<svelte:boundary>`](svelte-boundary) with a `pending` snippet.
+
+## html_deprecated
+
+> The `html` property of server render results has been deprecated. Use `body` instead.
+
+## lifecycle_function_unavailable
+
+> `%name%(...)` is not available on the server
+
+Certain methods such as `mount` cannot be invoked while running in a server context. Avoid calling them eagerly, i.e. not during render.
diff --git a/packages/svelte/messages/server-errors/lifecycle.md b/packages/svelte/messages/server-errors/lifecycle.md
deleted file mode 100644
index c3acdedf3d..0000000000
--- a/packages/svelte/messages/server-errors/lifecycle.md
+++ /dev/null
@@ -1,5 +0,0 @@
-## lifecycle_function_unavailable
-
-> `%name%(...)` is not available on the server
-
-Certain methods such as `mount` cannot be invoked while running in a server context. Avoid calling them eagerly, i.e. not during render.
diff --git a/packages/svelte/messages/server-warnings/warnings.md b/packages/svelte/messages/server-warnings/warnings.md
new file mode 100644
index 0000000000..4df89d0176
--- /dev/null
+++ b/packages/svelte/messages/server-warnings/warnings.md
@@ -0,0 +1,5 @@
+## experimental_async_ssr
+
+> Attempted to use asynchronous rendering without `experimental.async` enabled
+
+Set `experimental.async: true` in your compiler options (usually in `svelte.config.js`) to use async server rendering. This render ran synchronously.
diff --git a/packages/svelte/messages/shared-errors/errors.md b/packages/svelte/messages/shared-errors/errors.md
index f9160671d3..4b4d332202 100644
--- a/packages/svelte/messages/shared-errors/errors.md
+++ b/packages/svelte/messages/shared-errors/errors.md
@@ -1,21 +1,3 @@
-## await_outside_boundary
-
-> Cannot await outside a `<svelte:boundary>` with a `pending` snippet
-
-The `await` keyword can only appear in a `$derived(...)` or template expression, or at the top level of a component's `<script>` block, if it is inside a [`<svelte:boundary>`](/docs/svelte/svelte-boundary) that has a `pending` snippet:
-
-```svelte
-<svelte:boundary>
-	<p>{await getData()}</p>
-
-	{#snippet pending()}
-		<p>loading...</p>
-	{/snippet}
-</svelte:boundary>
-```
-
-This restriction may be lifted in a future version of Svelte.
-
 ## invalid_default_snippet
 
 > Cannot use `{@render children(...)}` if the parent component uses `let:` directives. Consider using a named snippet instead
diff --git a/packages/svelte/scripts/process-messages/index.js b/packages/svelte/scripts/process-messages/index.js
index e705a1c921..1904f1dfb4 100644
--- a/packages/svelte/scripts/process-messages/index.js
+++ b/packages/svelte/scripts/process-messages/index.js
@@ -401,6 +401,7 @@ function run() {
 
 	transform('client-warnings', 'src/internal/client/warnings.js');
 	transform('client-errors', 'src/internal/client/errors.js');
+	transform('server-warnings', 'src/internal/server/warnings.js');
 	transform('server-errors', 'src/internal/server/errors.js');
 	transform('shared-errors', 'src/internal/shared/errors.js');
 	transform('shared-warnings', 'src/internal/shared/warnings.js');
diff --git a/packages/svelte/scripts/process-messages/templates/server-warnings.js b/packages/svelte/scripts/process-messages/templates/server-warnings.js
new file mode 100644
index 0000000000..8a9b87b760
--- /dev/null
+++ b/packages/svelte/scripts/process-messages/templates/server-warnings.js
@@ -0,0 +1,20 @@
+import { DEV } from 'esm-env';
+
+var bold = 'font-weight: bold';
+var normal = 'font-weight: normal';
+
+/**
+ * MESSAGE
+ * @param {string} PARAMETER
+ */
+export function CODE(PARAMETER) {
+	if (DEV) {
+		console.warn(
+			`%c[svelte] ${'CODE'}\n%c${MESSAGE}\nhttps://svelte.dev/e/${'CODE'}`,
+			bold,
+			normal
+		);
+	} else {
+		console.warn(`https://svelte.dev/e/${'CODE'}`);
+	}
+}
diff --git a/packages/svelte/src/compiler/phases/1-parse/state/element.js b/packages/svelte/src/compiler/phases/1-parse/state/element.js
index ed1b047d55..b0db9ce178 100644
--- a/packages/svelte/src/compiler/phases/1-parse/state/element.js
+++ b/packages/svelte/src/compiler/phases/1-parse/state/element.js
@@ -177,7 +177,8 @@ export default function element(parser) {
 						mathml: false,
 						scoped: false,
 						has_spread: false,
-						path: []
+						path: [],
+						synthetic_value_node: null
 					}
 				}
 			: /** @type {AST.ElementLike} */ ({
diff --git a/packages/svelte/src/compiler/phases/2-analyze/index.js b/packages/svelte/src/compiler/phases/2-analyze/index.js
index de27c4623b..47fe37c44d 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/index.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/index.js
@@ -278,7 +278,8 @@ export function analyze_module(source, options) {
 		tracing: false,
 		async_deriveds: new Set(),
 		comments,
-		classes: new Map()
+		classes: new Map(),
+		pickled_awaits: new Set()
 	};
 
 	state.adjust({
@@ -304,7 +305,8 @@ export function analyze_module(source, options) {
 			options: /** @type {ValidatedCompileOptions} */ (options),
 			fragment: null,
 			parent_element: null,
-			reactive_statement: null
+			reactive_statement: null,
+			in_derived: false
 		},
 		visitors
 	);
@@ -540,7 +542,8 @@ export function analyze_component(root, source, options) {
 		source,
 		snippet_renderers: new Map(),
 		snippets: new Set(),
-		async_deriveds: new Set()
+		async_deriveds: new Set(),
+		pickled_awaits: new Set()
 	};
 
 	if (!runes) {
@@ -699,7 +702,8 @@ export function analyze_component(root, source, options) {
 				expression: null,
 				state_fields: new Map(),
 				function_depth: scope.function_depth,
-				reactive_statement: null
+				reactive_statement: null,
+				in_derived: false
 			};
 
 			walk(/** @type {AST.SvelteNode} */ (ast), state, visitors);
@@ -766,7 +770,8 @@ export function analyze_component(root, source, options) {
 				component_slots: new Set(),
 				expression: null,
 				state_fields: new Map(),
-				function_depth: scope.function_depth
+				function_depth: scope.function_depth,
+				in_derived: false
 			};
 
 			walk(/** @type {AST.SvelteNode} */ (ast), state, visitors);
diff --git a/packages/svelte/src/compiler/phases/2-analyze/types.d.ts b/packages/svelte/src/compiler/phases/2-analyze/types.d.ts
index 2d99a2e155..ae9c5911f6 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/types.d.ts
+++ b/packages/svelte/src/compiler/phases/2-analyze/types.d.ts
@@ -27,6 +27,11 @@ export interface AnalysisState {
 
 	// legacy stuff
 	reactive_statement: null | ReactiveStatement;
+
+	/**
+	 * True if we're directly inside a `$derived(...)` expression (but not `$derived.by(...)`)
+	 */
+	in_derived: boolean;
 }
 
 export type Context<State extends AnalysisState = AnalysisState> = import('zimmerframe').Context<
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/AwaitExpression.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/AwaitExpression.js
index b2f59b849b..9018623570 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/AwaitExpression.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/AwaitExpression.js
@@ -1,5 +1,6 @@
-/** @import { AwaitExpression } from 'estree' */
+/** @import { AwaitExpression, Expression, SpreadElement, Property } from 'estree' */
 /** @import { Context } from '../types' */
+/** @import { AST } from '#compiler' */
 import * as e from '../../../errors.js';
 
 /**
@@ -7,16 +8,25 @@ import * as e from '../../../errors.js';
  * @param {Context} context
  */
 export function AwaitExpression(node, context) {
-	let suspend = context.state.ast_type === 'instance' && context.state.function_depth === 1;
+	const tla = context.state.ast_type === 'instance' && context.state.function_depth === 1;
+
+	// preserve context for
+	//   a) top-level await and
+	//   b) awaits that precede other expressions in template or `$derived(...)`
+	if (
+		tla ||
+		(is_reactive_expression(context.path, context.state.in_derived) &&
+			!is_last_evaluated_expression(context.path, node))
+	) {
+		context.state.analysis.pickled_awaits.add(node);
+	}
+
+	let suspend = tla;
 
 	if (context.state.expression) {
 		context.state.expression.has_await = true;
 
-		if (
-			context.state.fragment &&
-			// TODO there's probably a better way to do this
-			context.path.some((node) => node.type === 'ConstTag')
-		) {
+		if (context.state.fragment && context.path.some((node) => node.type === 'ConstTag')) {
 			context.state.fragment.metadata.has_await = true;
 		}
 
@@ -37,3 +47,101 @@ export function AwaitExpression(node, context) {
 
 	context.next();
 }
+
+/**
+ * @param {AST.SvelteNode[]} path
+ * @param {boolean} in_derived
+ */
+export function is_reactive_expression(path, in_derived) {
+	if (in_derived) {
+		return true;
+	}
+
+	let i = path.length;
+
+	while (i--) {
+		const parent = path[i];
+
+		if (
+			parent.type === 'ArrowFunctionExpression' ||
+			parent.type === 'FunctionExpression' ||
+			parent.type === 'FunctionDeclaration'
+		) {
+			return false;
+		}
+
+		// @ts-expect-error we could probably use a neater/more robust mechanism
+		if (parent.metadata) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+/**
+ * @param {AST.SvelteNode[]} path
+ * @param {Expression | SpreadElement | Property} node
+ */
+export function is_last_evaluated_expression(path, node) {
+	let i = path.length;
+
+	while (i--) {
+		const parent = /** @type {Expression | Property | SpreadElement} */ (path[i]);
+
+		// @ts-expect-error we could probably use a neater/more robust mechanism
+		if (parent.metadata) {
+			return true;
+		}
+
+		switch (parent.type) {
+			case 'ArrayExpression':
+				if (node !== parent.elements.at(-1)) return false;
+				break;
+
+			case 'AssignmentExpression':
+			case 'BinaryExpression':
+			case 'LogicalExpression':
+				if (node === parent.left) return false;
+				break;
+
+			case 'CallExpression':
+			case 'NewExpression':
+				if (node !== parent.arguments.at(-1)) return false;
+				break;
+
+			case 'ConditionalExpression':
+				if (node === parent.test) return false;
+				break;
+
+			case 'MemberExpression':
+				if (parent.computed && node === parent.object) return false;
+				break;
+
+			case 'ObjectExpression':
+				if (node !== parent.properties.at(-1)) return false;
+				break;
+
+			case 'Property':
+				if (node === parent.key) return false;
+				break;
+
+			case 'SequenceExpression':
+				if (node !== parent.expressions.at(-1)) return false;
+				break;
+
+			case 'TaggedTemplateExpression':
+				if (node !== parent.quasi.expressions.at(-1)) return false;
+				break;
+
+			case 'TemplateLiteral':
+				if (node !== parent.expressions.at(-1)) return false;
+				break;
+
+			default:
+				return false;
+		}
+
+		node = parent;
+	}
+}
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
index 9b6337b9ed..53a89125a2 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/CallExpression.js
@@ -241,6 +241,7 @@ export function CallExpression(node, context) {
 		context.next({
 			...context.state,
 			function_depth: context.state.function_depth + 1,
+			in_derived: true,
 			expression
 		});
 
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/ConstTag.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/ConstTag.js
index d5f5f7b2e0..5849d828a3 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/ConstTag.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/ConstTag.js
@@ -35,5 +35,9 @@ export function ConstTag(node, context) {
 	const declaration = node.declaration.declarations[0];
 
 	context.visit(declaration.id);
-	context.visit(declaration.init, { ...context.state, expression: node.metadata.expression });
+	context.visit(declaration.init, {
+		...context.state,
+		expression: node.metadata.expression,
+		in_derived: true
+	});
 }
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js
index fab5d46e1b..4f41621db3 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js
@@ -70,7 +70,7 @@ export function RegularElement(node, context) {
 		)
 	) {
 		const child = node.fragment.nodes[0];
-		node.attributes.push(create_attribute('value', child.start, child.end, [child]));
+		node.metadata.synthetic_value_node = child;
 	}
 
 	const binding = context.state.scope.get(node.name);
diff --git a/packages/svelte/src/compiler/phases/2-analyze/visitors/VariableDeclarator.js b/packages/svelte/src/compiler/phases/2-analyze/visitors/VariableDeclarator.js
index 89320f3962..f56a665de8 100644
--- a/packages/svelte/src/compiler/phases/2-analyze/visitors/VariableDeclarator.js
+++ b/packages/svelte/src/compiler/phases/2-analyze/visitors/VariableDeclarator.js
@@ -49,6 +49,12 @@ export function VariableDeclarator(node, context) {
 			}
 		}
 
+		if (rune === '$derived') {
+			context.visit(node.id);
+			context.visit(/** @type {Expression} */ (node.init), { ...context.state, in_derived: true });
+			return;
+		}
+
 		if (rune === '$props') {
 			if (node.id.type !== 'ObjectPattern' && node.id.type !== 'Identifier') {
 				e.props_invalid_identifier(node);
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js b/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js
index 706d2b4e10..2629379f63 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/transform-client.js
@@ -166,7 +166,6 @@ export function client_component(analysis, options) {
 		state_fields: new Map(),
 		transform: {},
 		in_constructor: false,
-		in_derived: false,
 		instance_level_snippets: [],
 		module_level_snippets: [],
 
@@ -712,7 +711,6 @@ export function client_module(analysis, options) {
 		state_fields: new Map(),
 		transform: {},
 		in_constructor: false,
-		in_derived: false,
 		is_instance: false
 	};
 
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/types.d.ts b/packages/svelte/src/compiler/phases/3-transform/client/types.d.ts
index 59c024dfb7..932d353671 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/types.d.ts
+++ b/packages/svelte/src/compiler/phases/3-transform/client/types.d.ts
@@ -6,8 +6,7 @@ import type {
 	Expression,
 	AssignmentExpression,
 	UpdateExpression,
-	VariableDeclaration,
-	Declaration
+	VariableDeclaration
 } from 'estree';
 import type { AST, Namespace, ValidatedCompileOptions } from '#compiler';
 import type { TransformState } from '../types.js';
@@ -22,11 +21,6 @@ export interface ClientTransformState extends TransformState {
 	 */
 	readonly in_constructor: boolean;
 
-	/**
-	 * True if we're directly inside a `$derived(...)` expression (but not `$derived.by(...)`)
-	 */
-	readonly in_derived: boolean;
-
 	/** `true` if we're transforming the contents of `<script>` */
 	readonly is_instance: boolean;
 
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/AwaitExpression.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/AwaitExpression.js
index 803d317ad4..798d1bcdac 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/AwaitExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/AwaitExpression.js
@@ -1,4 +1,4 @@
-/** @import { AwaitExpression, Expression, Property, SpreadElement } from 'estree' */
+/** @import { AwaitExpression, Expression } from 'estree' */
 /** @import { Context } from '../types' */
 import { dev, is_ignored } from '../../../../state.js';
 import * as b from '../../../../utils/builders.js';
@@ -10,12 +10,7 @@ import * as b from '../../../../utils/builders.js';
 export function AwaitExpression(node, context) {
 	const argument = /** @type {Expression} */ (context.visit(node.argument));
 
-	const tla = context.state.is_instance && context.state.scope.function_depth === 1;
-
-	// preserve context for
-	//   a) top-level await and
-	//   b) awaits that precede other expressions in template or `$derived(...)`
-	if (tla || (is_reactive_expression(context) && !is_last_evaluated_expression(context, node))) {
+	if (context.state.analysis.pickled_awaits.has(node)) {
 		return b.call(b.await(b.call('$.save', argument)));
 	}
 
@@ -27,100 +22,3 @@ export function AwaitExpression(node, context) {
 
 	return argument === node.argument ? node : { ...node, argument };
 }
-
-/**
- * @param {Context} context
- */
-function is_reactive_expression(context) {
-	if (context.state.in_derived) {
-		return true;
-	}
-
-	let i = context.path.length;
-
-	while (i--) {
-		const parent = context.path[i];
-
-		if (
-			parent.type === 'ArrowFunctionExpression' ||
-			parent.type === 'FunctionExpression' ||
-			parent.type === 'FunctionDeclaration'
-		) {
-			return false;
-		}
-
-		// @ts-expect-error we could probably use a neater/more robust mechanism
-		if (parent.metadata) {
-			return true;
-		}
-	}
-
-	return false;
-}
-
-/**
- * @param {Context} context
- * @param {Expression | SpreadElement | Property} node
- */
-function is_last_evaluated_expression(context, node) {
-	let i = context.path.length;
-
-	while (i--) {
-		const parent = /** @type {Expression | Property | SpreadElement} */ (context.path[i]);
-
-		// @ts-expect-error we could probably use a neater/more robust mechanism
-		if (parent.metadata) {
-			return true;
-		}
-
-		switch (parent.type) {
-			case 'ArrayExpression':
-				if (node !== parent.elements.at(-1)) return false;
-				break;
-
-			case 'AssignmentExpression':
-			case 'BinaryExpression':
-			case 'LogicalExpression':
-				if (node === parent.left) return false;
-				break;
-
-			case 'CallExpression':
-			case 'NewExpression':
-				if (node !== parent.arguments.at(-1)) return false;
-				break;
-
-			case 'ConditionalExpression':
-				if (node === parent.test) return false;
-				break;
-
-			case 'MemberExpression':
-				if (parent.computed && node === parent.object) return false;
-				break;
-
-			case 'ObjectExpression':
-				if (node !== parent.properties.at(-1)) return false;
-				break;
-
-			case 'Property':
-				if (node === parent.key) return false;
-				break;
-
-			case 'SequenceExpression':
-				if (node !== parent.expressions.at(-1)) return false;
-				break;
-
-			case 'TaggedTemplateExpression':
-				if (node !== parent.quasi.expressions.at(-1)) return false;
-				break;
-
-			case 'TemplateLiteral':
-				if (node !== parent.expressions.at(-1)) return false;
-				break;
-
-			default:
-				return false;
-		}
-
-		node = parent;
-	}
-}
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
index c126742d3c..fcc385c2ba 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/CallExpression.js
@@ -44,9 +44,7 @@ export function CallExpression(node, context) {
 
 		case '$derived':
 		case '$derived.by': {
-			let fn = /** @type {Expression} */ (
-				context.visit(node.arguments[0], { ...context.state, in_derived: rune === '$derived' })
-			);
+			let fn = /** @type {Expression} */ (context.visit(node.arguments[0]));
 
 			return b.call('$.derived', rune === '$derived' ? b.thunk(fn) : fn);
 		}
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/ConstTag.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/ConstTag.js
index b550dae890..81dd9e07ed 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/ConstTag.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/ConstTag.js
@@ -16,11 +16,7 @@ export function ConstTag(node, context) {
 	const declaration = node.declaration.declarations[0];
 	// TODO we can almost certainly share some code with $derived(...)
 	if (declaration.id.type === 'Identifier') {
-		const init = build_expression(
-			{ ...context, state: { ...context.state, in_derived: true } },
-			declaration.init,
-			node.metadata.expression
-		);
+		const init = build_expression(context, declaration.init, node.metadata.expression);
 
 		let expression = create_derived(context.state, init, node.metadata.expression.has_await);
 
@@ -51,8 +47,7 @@ export function ConstTag(node, context) {
 
 		const child_state = /** @type {ComponentContext['state']} */ ({
 			...context.state,
-			transform,
-			in_derived: true
+			transform
 		});
 
 		// TODO optimise the simple `{ x } = y` case — we can just return `y`
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
index e906061650..e35b7cbe5a 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/RegularElement.js
@@ -11,7 +11,7 @@ import {
 import { is_ignored } from '../../../../state.js';
 import { is_event_attribute, is_text_attribute } from '../../../../utils/ast.js';
 import * as b from '#compiler/builders';
-import { is_custom_element_node } from '../../../nodes.js';
+import { create_attribute, is_custom_element_node } from '../../../nodes.js';
 import { clean_nodes, determine_namespace_for_children } from '../../utils.js';
 import { build_getter } from '../utils.js';
 import {
@@ -406,10 +406,24 @@ export function RegularElement(node, context) {
 	}
 
 	if (!has_spread && needs_special_value_handling) {
-		for (const attribute of /** @type {AST.Attribute[]} */ (attributes)) {
-			if (attribute.name === 'value') {
-				build_element_special_value_attribute(node.name, node_id, attribute, context);
-				break;
+		if (node.metadata.synthetic_value_node) {
+			const synthetic_node = node.metadata.synthetic_value_node;
+			const synthetic_attribute = create_attribute(
+				'value',
+				synthetic_node.start,
+				synthetic_node.end,
+				[synthetic_node]
+			);
+			// this node is an `option` that didn't have a `value` attribute, but had
+			// a single-expression child, so we treat the value of that expression as
+			// the value of the option
+			build_element_special_value_attribute(node.name, node_id, synthetic_attribute, context, true);
+		} else {
+			for (const attribute of /** @type {AST.Attribute[]} */ (attributes)) {
+				if (attribute.name === 'value') {
+					build_element_special_value_attribute(node.name, node_id, attribute, context);
+					break;
+				}
 			}
 		}
 	}
@@ -645,8 +659,15 @@ function build_custom_element_attribute_update_assignment(node_id, attribute, co
  * @param {Identifier} node_id
  * @param {AST.Attribute} attribute
  * @param {ComponentContext} context
+ * @param {boolean} [synthetic] - true if this should not sync to the DOM
  */
-function build_element_special_value_attribute(element, node_id, attribute, context) {
+function build_element_special_value_attribute(
+	element,
+	node_id,
+	attribute,
+	context,
+	synthetic = false
+) {
 	const state = context.state;
 	const is_select_with_value =
 		// attribute.metadata.dynamic would give false negatives because even if the value does not change,
@@ -660,7 +681,7 @@ function build_element_special_value_attribute(element, node_id, attribute, cont
 	const evaluated = context.state.scope.evaluate(value);
 	const assignment = b.assignment('=', b.member(node_id, '__value'), value);
 
-	const inner_assignment = b.assignment(
+	const set_value_assignment = b.assignment(
 		'=',
 		b.member(node_id, 'value'),
 		evaluated.is_defined ? assignment : b.logical('??', assignment, b.literal(''))
@@ -669,14 +690,16 @@ function build_element_special_value_attribute(element, node_id, attribute, cont
 	const update = b.stmt(
 		is_select_with_value
 			? b.sequence([
-					inner_assignment,
+					set_value_assignment,
 					// This ensures a one-way street to the DOM in case it's <select {value}>
 					// and not <select bind:value>. We need it in addition to $.init_select
 					// because the select value is not reflected as an attribute, so the
 					// mutation observer wouldn't notice.
 					b.call('$.select_option', node_id, value)
 				])
-			: inner_assignment
+			: synthetic
+				? assignment
+				: set_value_assignment
 	);
 
 	if (has_state) {
diff --git a/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js b/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
index 0998dc4778..db5fe5252e 100644
--- a/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
+++ b/packages/svelte/src/compiler/phases/3-transform/client/visitors/VariableDeclaration.js
@@ -202,12 +202,7 @@ export function VariableDeclaration(node, context) {
 				);
 
 				if (declarator.id.type === 'Identifier') {
-					let expression = /** @type {Expression} */ (
-						context.visit(value, {
-							...context.state,
-							in_derived: rune === '$derived'
-						})
-					);
+					let expression = /** @type {Expression} */ (context.visit(value));
 
 					if (is_async) {
 						const location = dev && !is_ignored(init, 'await_waterfall') && locate_node(init);
@@ -231,12 +226,7 @@ export function VariableDeclaration(node, context) {
 					}
 				} else {
 					const init = /** @type {CallExpression} */ (declarator.init);
-					let expression = /** @type {Expression} */ (
-						context.visit(value, {
-							...context.state,
-							in_derived: rune === '$derived'
-						})
-					);
+					let expression = /** @type {Expression} */ (context.visit(value));
 
 					let rhs = value;
 
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/transform-server.js b/packages/svelte/src/compiler/phases/3-transform/server/transform-server.js
index 10c92242d4..4486c6e7a3 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/transform-server.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/transform-server.js
@@ -6,7 +6,7 @@ import { walk } from 'zimmerframe';
 import { set_scope } from '../../scope.js';
 import { extract_identifiers } from '../../../utils/ast.js';
 import * as b from '#compiler/builders';
-import { dev, filename } from '../../../state.js';
+import { component_name, dev, filename } from '../../../state.js';
 import { render_stylesheet } from '../css/index.js';
 import { AssignmentExpression } from './visitors/AssignmentExpression.js';
 import { AwaitBlock } from './visitors/AwaitBlock.js';
@@ -40,6 +40,7 @@ import { TitleElement } from './visitors/TitleElement.js';
 import { UpdateExpression } from './visitors/UpdateExpression.js';
 import { VariableDeclaration } from './visitors/VariableDeclaration.js';
 import { SvelteBoundary } from './visitors/SvelteBoundary.js';
+import { call_child_payload, call_component_payload } from './visitors/shared/utils.js';
 
 /** @type {Visitors} */
 const global_visitors = {
@@ -197,13 +198,11 @@ export function server_component(analysis, options) {
 				b.unary('!', b.id('$$settled')),
 				b.block([
 					b.stmt(b.assignment('=', b.id('$$settled'), b.true)),
-					b.stmt(
-						b.assignment('=', b.id('$$inner_payload'), b.call('$.copy_payload', b.id('$$payload')))
-					),
+					b.stmt(b.assignment('=', b.id('$$inner_payload'), b.call('$$payload.copy'))),
 					b.stmt(b.call('$$render_inner', b.id('$$inner_payload')))
 				])
 			),
-			b.stmt(b.call('$.assign_payload', b.id('$$payload'), b.id('$$inner_payload')))
+			b.stmt(b.call('$$payload.subsume', b.id('$$inner_payload')))
 		];
 	}
 
@@ -239,11 +238,15 @@ export function server_component(analysis, options) {
 		template.body.push(b.stmt(b.call('$.bind_props', b.id('$$props'), b.object(props))));
 	}
 
-	const component_block = b.block([
+	let component_block = b.block([
 		.../** @type {Statement[]} */ (instance.body),
 		.../** @type {Statement[]} */ (template.body)
 	]);
 
+	if (analysis.instance.has_await) {
+		component_block = b.block([call_child_payload(component_block, true)]);
+	}
+
 	// trick esrap into including comments
 	component_block.loc = instance.loc;
 
@@ -257,8 +260,9 @@ export function server_component(analysis, options) {
 	let should_inject_context = dev || analysis.needs_context;
 
 	if (should_inject_context) {
-		component_block.body.unshift(b.stmt(b.call('$.push', dev && b.id(analysis.name))));
-		component_block.body.push(b.stmt(b.call('$.pop')));
+		component_block = b.block([
+			call_component_payload(component_block, dev && b.id(component_name))
+		]);
 	}
 
 	if (analysis.uses_rest_props) {
@@ -297,7 +301,7 @@ export function server_component(analysis, options) {
 		const code = b.literal(render_stylesheet(analysis.source, analysis, options).code);
 
 		body.push(b.const('$$css', b.object([b.init('hash', hash), b.init('code', code)])));
-		component_block.body.unshift(b.stmt(b.call('$$payload.css.add', b.id('$$css'))));
+		component_block.body.unshift(b.stmt(b.call('$$payload.global.css.add', b.id('$$css'))));
 	}
 
 	let should_inject_props =
@@ -377,6 +381,10 @@ export function server_component(analysis, options) {
 		);
 	}
 
+	if (options.experimental.async) {
+		body.unshift(b.imports([], 'svelte/internal/flags/async'));
+	}
+
 	return {
 		type: 'Program',
 		sourceType: 'module',
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/AwaitBlock.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/AwaitBlock.js
index 35e431f43d..ea60c95f68 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/AwaitBlock.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/AwaitBlock.js
@@ -1,29 +1,33 @@
-/** @import { BlockStatement, Expression, Pattern } from 'estree' */
+/** @import { BlockStatement, Expression, Pattern, Statement } from 'estree' */
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../types.js' */
 import * as b from '#compiler/builders';
-import { block_close } from './shared/utils.js';
+import { block_close, call_child_payload } from './shared/utils.js';
 
 /**
  * @param {AST.AwaitBlock} node
  * @param {ComponentContext} context
  */
 export function AwaitBlock(node, context) {
-	context.state.template.push(
-		b.stmt(
-			b.call(
-				'$.await',
-				b.id('$$payload'),
-				/** @type {Expression} */ (context.visit(node.expression)),
-				b.thunk(
-					node.pending ? /** @type {BlockStatement} */ (context.visit(node.pending)) : b.block([])
-				),
-				b.arrow(
-					node.value ? [/** @type {Pattern} */ (context.visit(node.value))] : [],
-					node.then ? /** @type {BlockStatement} */ (context.visit(node.then)) : b.block([])
-				)
+	/** @type {Statement} */
+	let statement = b.stmt(
+		b.call(
+			'$.await',
+			b.id('$$payload'),
+			/** @type {Expression} */ (context.visit(node.expression)),
+			b.thunk(
+				node.pending ? /** @type {BlockStatement} */ (context.visit(node.pending)) : b.block([])
+			),
+			b.arrow(
+				node.value ? [/** @type {Pattern} */ (context.visit(node.value))] : [],
+				node.then ? /** @type {BlockStatement} */ (context.visit(node.then)) : b.block([])
 			)
-		),
-		block_close
+		)
 	);
+
+	if (node.metadata.expression.has_await) {
+		statement = call_child_payload(b.block([statement]), true);
+	}
+
+	context.state.template.push(statement, block_close);
 }
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/AwaitExpression.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/AwaitExpression.js
index 9135892dbd..6384a6d4e7 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/AwaitExpression.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/AwaitExpression.js
@@ -1,5 +1,5 @@
-/** @import { AwaitExpression } from 'estree' */
-/** @import { Context } from '../types.js' */
+/** @import { AwaitExpression, Expression } from 'estree' */
+/** @import { Context } from '../types' */
 import * as b from '../../../../utils/builders.js';
 
 /**
@@ -7,19 +7,11 @@ import * as b from '../../../../utils/builders.js';
  * @param {Context} context
  */
 export function AwaitExpression(node, context) {
-	// if `await` is inside a function, or inside `<script module>`,
-	// allow it, otherwise error
-	if (
-		context.state.scope.function_depth === 0 ||
-		context.path.some(
-			(node) =>
-				node.type === 'ArrowFunctionExpression' ||
-				node.type === 'FunctionDeclaration' ||
-				node.type === 'FunctionExpression'
-		)
-	) {
-		return context.next();
+	const argument = /** @type {Expression} */ (context.visit(node.argument));
+
+	if (context.state.analysis.pickled_awaits.has(node)) {
+		return b.call(b.await(b.call('$.save', argument)));
 	}
 
-	return b.call('$.await_outside_boundary');
+	return argument === node.argument ? node : { ...node, argument };
 }
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/EachBlock.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/EachBlock.js
index ee0086de2e..eb0da55657 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/EachBlock.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/EachBlock.js
@@ -1,9 +1,8 @@
 /** @import { BlockStatement, Expression, Statement } from 'estree' */
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../types.js' */
-import { BLOCK_OPEN_ELSE } from '../../../../../internal/server/hydration.js';
 import * as b from '#compiler/builders';
-import { block_close, block_open } from './shared/utils.js';
+import { block_close, block_open, block_open_else, call_child_payload } from './shared/utils.js';
 
 /**
  * @param {AST.EachBlock} node
@@ -18,7 +17,9 @@ export function EachBlock(node, context) {
 		each_node_meta.contains_group_binding || !node.index ? each_node_meta.index : b.id(node.index);
 
 	const array_id = state.scope.root.unique('each_array');
-	state.init.push(b.const(array_id, b.call('$.ensure_array_like', collection)));
+
+	/** @type {Statement} */
+	let block = b.block([b.const(array_id, b.call('$.ensure_array_like', collection))]);
 
 	/** @type {Statement[]} */
 	const each = [];
@@ -44,23 +45,27 @@ export function EachBlock(node, context) {
 	);
 
 	if (node.fallback) {
-		const open = b.stmt(b.call(b.member(b.id('$$payload.out'), b.id('push')), block_open));
+		const open = b.stmt(b.call(b.id('$$payload.push'), block_open));
 
 		const fallback = /** @type {BlockStatement} */ (context.visit(node.fallback));
 
-		fallback.body.unshift(
-			b.stmt(b.call(b.member(b.id('$$payload.out'), b.id('push')), b.literal(BLOCK_OPEN_ELSE)))
-		);
+		fallback.body.unshift(b.stmt(b.call(b.id('$$payload.push'), block_open_else)));
 
-		state.template.push(
+		block.body.push(
 			b.if(
 				b.binary('!==', b.member(array_id, 'length'), b.literal(0)),
 				b.block([open, for_loop]),
 				fallback
-			),
-			block_close
+			)
 		);
 	} else {
-		state.template.push(block_open, for_loop, block_close);
+		state.template.push(block_open);
+		block.body.push(for_loop);
+	}
+
+	if (node.metadata.expression.has_await) {
+		state.template.push(call_child_payload(block, true), block_close);
+	} else {
+		state.template.push(...block.body, block_close);
 	}
 }
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/IfBlock.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/IfBlock.js
index 8c082f38d5..37d4585900 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/IfBlock.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/IfBlock.js
@@ -1,9 +1,8 @@
-/** @import { BlockStatement, Expression } from 'estree' */
+/** @import { BlockStatement, Expression, Statement } from 'estree' */
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../types.js' */
-import { BLOCK_OPEN_ELSE } from '../../../../../internal/server/hydration.js';
 import * as b from '#compiler/builders';
-import { block_close, block_open } from './shared/utils.js';
+import { block_close, block_open, block_open_else, call_child_payload } from './shared/utils.js';
 
 /**
  * @param {AST.IfBlock} node
@@ -17,13 +16,16 @@ export function IfBlock(node, context) {
 		? /** @type {BlockStatement} */ (context.visit(node.alternate))
 		: b.block([]);
 
-	consequent.body.unshift(
-		b.stmt(b.call(b.member(b.id('$$payload.out'), b.id('push')), block_open))
-	);
+	consequent.body.unshift(b.stmt(b.call(b.id('$$payload.push'), block_open)));
 
-	alternate.body.unshift(
-		b.stmt(b.call(b.member(b.id('$$payload.out'), b.id('push')), b.literal(BLOCK_OPEN_ELSE)))
-	);
+	alternate.body.unshift(b.stmt(b.call(b.id('$$payload.push'), block_open_else)));
 
-	context.state.template.push(b.if(test, consequent, alternate), block_close);
+	/** @type {Statement} */
+	let statement = b.if(test, consequent, alternate);
+
+	if (node.metadata.expression.has_await) {
+		statement = call_child_payload(b.block([statement]), true);
+	}
+
+	context.state.template.push(statement, block_close);
 }
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/RegularElement.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/RegularElement.js
index 0779195e2e..29aad94a31 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/RegularElement.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/RegularElement.js
@@ -1,4 +1,4 @@
-/** @import { Expression } from 'estree' */
+/** @import { Expression, Statement } from 'estree' */
 /** @import { Location } from 'locate-character' */
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext, ComponentServerTransformState } from '../types.js' */
@@ -8,7 +8,12 @@ import { dev, locator } from '../../../../state.js';
 import * as b from '#compiler/builders';
 import { clean_nodes, determine_namespace_for_children } from '../../utils.js';
 import { build_element_attributes, build_spread_object } from './shared/element.js';
-import { process_children, build_template, build_attribute_value } from './shared/utils.js';
+import {
+	process_children,
+	build_template,
+	build_attribute_value,
+	call_child_payload
+} from './shared/utils.js';
 
 /**
  * @param {AST.RegularElement} node
@@ -73,6 +78,8 @@ export function RegularElement(node, context) {
 	}
 
 	let select_with_value = false;
+	let select_with_value_async = false;
+	const template_start = state.template.length;
 
 	if (node.name === 'select') {
 		const value = node.attributes.find(
@@ -80,13 +87,17 @@ export function RegularElement(node, context) {
 				(attribute.type === 'Attribute' || attribute.type === 'BindDirective') &&
 				attribute.name === 'value'
 		);
-		if (node.attributes.some((attribute) => attribute.type === 'SpreadAttribute')) {
+
+		const spread = node.attributes.find((attribute) => attribute.type === 'SpreadAttribute');
+		if (spread) {
 			select_with_value = true;
+			select_with_value_async ||= spread.metadata.expression.has_await;
+
 			state.template.push(
 				b.stmt(
 					b.assignment(
 						'=',
-						b.id('$$payload.select_value'),
+						b.id('$$payload.local.select_value'),
 						b.member(
 							build_spread_object(
 								node,
@@ -107,7 +118,14 @@ export function RegularElement(node, context) {
 			);
 		} else if (value) {
 			select_with_value = true;
-			const left = b.id('$$payload.select_value');
+
+			if (value.type === 'Attribute' && value.value !== true) {
+				select_with_value_async ||= (Array.isArray(value.value) ? value.value : [value.value]).some(
+					(tag) => tag.type === 'ExpressionTag' && tag.metadata.expression.has_await
+				);
+			}
+
+			const left = b.id('$$payload.local.select_value');
 			if (value.type === 'Attribute') {
 				state.template.push(
 					b.stmt(b.assignment('=', left, build_attribute_value(value.value, context)))
@@ -137,18 +155,35 @@ export function RegularElement(node, context) {
 					attribute.name === 'value')
 		)
 	) {
-		const inner_state = { ...state, template: [], init: [] };
-		process_children(trimmed, { ...context, state: inner_state });
-
-		state.template.push(
-			b.stmt(
-				b.call(
-					'$.valueless_option',
-					b.id('$$payload'),
-					b.thunk(b.block([...inner_state.init, ...build_template(inner_state.template)]))
+		if (node.metadata.synthetic_value_node) {
+			state.template.push(
+				b.stmt(
+					b.call(
+						'$.simple_valueless_option',
+						b.id('$$payload'),
+						b.thunk(
+							node.metadata.synthetic_value_node.expression,
+							node.metadata.synthetic_value_node.metadata.expression.has_await
+						)
+					)
 				)
-			)
-		);
+			);
+		} else {
+			const inner_state = { ...state, template: [], init: [] };
+			process_children(trimmed, { ...context, state: inner_state });
+			state.template.push(
+				b.stmt(
+					b.call(
+						'$.valueless_option',
+						b.id('$$payload'),
+						b.arrow(
+							[b.id('$$payload')],
+							b.block([...inner_state.init, ...build_template(inner_state.template)])
+						)
+					)
+				)
+			);
+		}
 	} else if (body !== null) {
 		// if this is a `<textarea>` value or a contenteditable binding, we only add
 		// the body if the attribute/binding is falsy
@@ -175,7 +210,14 @@ export function RegularElement(node, context) {
 	}
 
 	if (select_with_value) {
-		state.template.push(b.stmt(b.assignment('=', b.id('$$payload.select_value'), b.void0)));
+		// we need to create a child scope so that the `select_value` only applies children of this select element
+		// in an async world, we could technically have two adjacent select elements with async children, in which case
+		// the second element's select_value would override the first element's select_value if the children of the first
+		// element hadn't resolved prior to hitting the second element.
+		const elements = state.template.splice(template_start, Infinity);
+		state.template.push(
+			call_child_payload(b.block(build_template(elements)), select_with_value_async)
+		);
 	}
 
 	if (!node_is_void) {
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/SlotElement.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/SlotElement.js
index fee7cb6e02..2d16a07b4e 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/SlotElement.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/SlotElement.js
@@ -2,7 +2,12 @@
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../types.js' */
 import * as b from '#compiler/builders';
-import { empty_comment, build_attribute_value } from './shared/utils.js';
+import {
+	empty_comment,
+	build_attribute_value,
+	PromiseOptimiser,
+	call_child_payload
+} from './shared/utils.js';
 
 /**
  * @param {AST.SlotElement} node
@@ -15,13 +20,22 @@ export function SlotElement(node, context) {
 	/** @type {Expression[]} */
 	const spreads = [];
 
+	const optimiser = new PromiseOptimiser();
+
 	let name = b.literal('default');
 
 	for (const attribute of node.attributes) {
 		if (attribute.type === 'SpreadAttribute') {
-			spreads.push(/** @type {Expression} */ (context.visit(attribute)));
+			let expression = /** @type {Expression} */ (context.visit(attribute));
+			spreads.push(optimiser.transform(expression, attribute.metadata.expression));
 		} else if (attribute.type === 'Attribute') {
-			const value = build_attribute_value(attribute.value, context, false, true);
+			const value = build_attribute_value(
+				attribute.value,
+				context,
+				false,
+				true,
+				optimiser.transform
+			);
 
 			if (attribute.name === 'name') {
 				name = /** @type {Literal} */ (value);
@@ -50,5 +64,10 @@ export function SlotElement(node, context) {
 		fallback
 	);
 
-	context.state.template.push(empty_comment, b.stmt(slot), empty_comment);
+	const statement =
+		optimiser.expressions.length > 0
+			? call_child_payload(b.block([optimiser.apply(), b.stmt(slot)]), true)
+			: b.stmt(slot);
+
+	context.state.template.push(empty_comment, statement, empty_comment);
 }
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/SvelteBoundary.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/SvelteBoundary.js
index 6e814d6384..355b33aea7 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/SvelteBoundary.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/SvelteBoundary.js
@@ -1,17 +1,14 @@
 /** @import { BlockStatement } from 'estree' */
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../types' */
-import { BLOCK_CLOSE, BLOCK_OPEN } from '../../../../../internal/server/hydration.js';
 import * as b from '#compiler/builders';
-import { build_attribute_value } from './shared/utils.js';
+import { block_close, block_open, block_open_else, build_attribute_value } from './shared/utils.js';
 
 /**
  * @param {AST.SvelteBoundary} node
  * @param {ComponentContext} context
  */
 export function SvelteBoundary(node, context) {
-	context.state.template.push(b.literal(BLOCK_OPEN));
-
 	// if this has a `pending` snippet, render it
 	const pending_attribute = /** @type {AST.Attribute} */ (
 		node.attributes.find((node) => node.type === 'Attribute' && node.name === 'pending')
@@ -23,16 +20,17 @@ export function SvelteBoundary(node, context) {
 		)
 	);
 
-	if (pending_attribute) {
-		const value = build_attribute_value(pending_attribute.value, context, false, true);
-		context.state.template.push(b.call(value, b.id('$$payload')));
-	} else if (pending_snippet) {
-		context.state.template.push(
-			/** @type {BlockStatement} */ (context.visit(pending_snippet.body))
-		);
+	if (pending_attribute || pending_snippet) {
+		const pending = pending_attribute
+			? b.call(
+					build_attribute_value(pending_attribute.value, context, false, true),
+					b.id('$$payload')
+				)
+			: /** @type {BlockStatement} */ (context.visit(pending_snippet.body));
+
+		context.state.template.push(block_open_else, pending, block_close);
 	} else {
-		context.state.template.push(/** @type {BlockStatement} */ (context.visit(node.fragment)));
+		const block = /** @type {BlockStatement} */ (context.visit(node.fragment));
+		context.state.template.push(block_open, block, block_close);
 	}
-
-	context.state.template.push(b.literal(BLOCK_CLOSE));
 }
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/TitleElement.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/TitleElement.js
index c42df4c646..a3ffb2df3d 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/TitleElement.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/TitleElement.js
@@ -13,5 +13,7 @@ export function TitleElement(node, context) {
 	process_children(node.fragment.nodes, { ...context, state: { ...context.state, template } });
 	template.push(b.literal('</title>'));
 
-	context.state.init.push(...build_template(template, b.id('$$payload.title'), '='));
+	context.state.init.push(
+		b.stmt(b.call('$.build_title', b.id('$$payload'), b.thunk(b.block(build_template(template)))))
+	);
 }
diff --git a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
index 9bccf9e05e..614a2ed258 100644
--- a/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
+++ b/packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/component.js
@@ -1,7 +1,12 @@
 /** @import { BlockStatement, Expression, Pattern, Property, SequenceExpression, Statement } from 'estree' */
 /** @import { AST } from '#compiler' */
 /** @import { ComponentContext } from '../../types.js' */
-import { empty_comment, build_attribute_value } from './utils.js';
+import {
+	empty_comment,
+	build_attribute_value,
+	call_child_payload,
+	PromiseOptimiser
+} from './utils.js';
 import * as b from '#compiler/builders';
 import { is_element_node } from '../../../../nodes.js';
 import { dev } from '../../../../../state.js';
@@ -72,16 +77,26 @@ export function build_inline_component(node, expression, context) {
 		}
 	}
 
+	const optimiser = new PromiseOptimiser();
+
 	for (const attribute of node.attributes) {
 		if (attribute.type === 'LetDirective') {
 			if (!slot_scope_applies_to_itself) {
 				lets.default.push(attribute);
 			}
 		} else if (attribute.type === 'SpreadAttribute') {
-			props_and_spreads.push(/** @type {Expression} */ (context.visit(attribute)));
+			let expression = /** @type {Expression} */ (context.visit(attribute));
+			props_and_spreads.push(optimiser.transform(expression, attribute.metadata.expression));
 		} else if (attribute.type === 'Attribute') {
+			const value = build_attribute_value(
+				attribute.value,
+				context,
+				false,
+				true,
+				optimiser.transform
+			);
+
 			if (attribute.name.startsWith('--')) {
-				const value = build_attribute_value(attribute.value, context, false, true);
 				custom_css_props.push(b.init(attribute.name, value));
 				continue;
 			}
@@ -90,7 +105,6 @@ export function build_inline_component(node, expression, context) {
 				has_children_prop = true;
 			}
 
-			const value = build_attribute_value(attribute.value, context, false, true);
 			push_prop(b.prop('init', b.key(attribute.name), value));
 		} else if (attribute.type === 'BindDirective' && attribute.name !== 'this') {
 			if (attribute.expression.type === 'SequenceExpression') {
@@ -291,27 +305,29 @@ export function build_inline_component(node, expression, context) {
 		node.type === 'SvelteComponent' || (node.type === 'Component' && node.metadata.dynamic);
 
 	if (custom_css_props.length > 0) {
-		context.state.template.push(
-			b.stmt(
-				b.call(
-					'$.css_props',
-					b.id('$$payload'),
-					b.literal(context.state.namespace === 'svg' ? false : true),
-					b.object(custom_css_props),
-					b.thunk(b.block([statement])),
-					dynamic && b.true
-				)
+		statement = b.stmt(
+			b.call(
+				'$.css_props',
+				b.id('$$payload'),
+				b.literal(context.state.namespace === 'svg' ? false : true),
+				b.object(custom_css_props),
+				b.thunk(b.block([statement])),
+				dynamic && b.true
 			)
 		);
-	} else {
-		if (dynamic) {
-			context.state.template.push(empty_comment);
-		}
+	}
 
-		context.state.template.push(statement);
+	if (optimiser.expressions.length > 0) {
+		statement = call_child_payload(b.block([optimiser.apply(), statement]), true);
+	}
 
-		if (!context.state.skip_hydration_boundaries) {
-			context.state.template.push(empty_comment);
-		}
+	if (dynamic && custom_css_props.length === 0) {
+		context.state.template.push(empty_comment);
+	}
+
+	context.state.template.push(statement);
+
+	if (!context.state.skip_hydration_boundaries && custom_css_props.length === 0) {
+		context.state.template.push(empty_comment);
 	}
 }
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 8a8633dd1a..a48c19ae7c 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
@@ -1,20 +1,25 @@
-/** @import { AssignmentOperator, Expression, Identifier, Node, Statement } from 'estree' */
-/** @import { AST } from '#compiler' */
+/** @import { AssignmentOperator, Expression, Identifier, Node, Statement, BlockStatement } from 'estree' */
+/** @import { AST, ExpressionMetadata } from '#compiler' */
 /** @import { ComponentContext, ServerTransformState } from '../../types.js' */
 
 import { escape_html } from '../../../../../../escaping.js';
 import {
 	BLOCK_CLOSE,
 	BLOCK_OPEN,
+	BLOCK_OPEN_ELSE,
 	EMPTY_COMMENT
 } from '../../../../../../internal/server/hydration.js';
 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';
 
 /** 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);
 
+/** Opens an if/each block, so that we can remove nodes in the case of a mismatch */
+export const block_open_else = b.literal(BLOCK_OPEN_ELSE);
+
 /** Closes an if/each block, so that we can remove nodes in the case of a mismatch. Also serves as an anchor for these blocks */
 export const block_close = b.literal(BLOCK_CLOSE);
 
@@ -32,6 +37,10 @@ export function process_children(nodes, { visit, state }) {
 	let sequence = [];
 
 	function flush() {
+		if (sequence.length === 0) {
+			return;
+		}
+
 		let quasi = b.quasi('', false);
 		const quasis = [quasi];
 
@@ -63,26 +72,25 @@ export function process_children(nodes, { visit, state }) {
 		}
 
 		state.template.push(b.template(quasis, expressions));
+		sequence = [];
 	}
 
-	for (let i = 0; i < nodes.length; i += 1) {
-		const node = nodes[i];
-
-		if (node.type === 'Text' || node.type === 'Comment' || node.type === 'ExpressionTag') {
+	for (const node of nodes) {
+		if (node.type === 'ExpressionTag' && node.metadata.expression.has_await) {
+			flush();
+			const visited = /** @type {Expression} */ (visit(node.expression));
+			state.template.push(
+				b.stmt(b.call('$$payload.push', b.thunk(b.call('$.escape', visited), true)))
+			);
+		} else if (node.type === 'Text' || node.type === 'Comment' || node.type === 'ExpressionTag') {
 			sequence.push(node);
 		} else {
-			if (sequence.length > 0) {
-				flush();
-				sequence = [];
-			}
-
+			flush();
 			visit(node, { ...state });
 		}
 	}
 
-	if (sequence.length > 0) {
-		flush();
-	}
+	flush();
 }
 
 /**
@@ -95,11 +103,9 @@ function is_statement(node) {
 
 /**
  * @param {Array<Statement | Expression>} template
- * @param {Identifier} out
- * @param {AssignmentOperator | 'push'} operator
  * @returns {Statement[]}
  */
-export function build_template(template, out = b.id('$$payload.out'), operator = 'push') {
+export function build_template(template) {
 	/** @type {string[]} */
 	let strings = [];
 
@@ -110,32 +116,18 @@ export function build_template(template, out = b.id('$$payload.out'), operator =
 	const statements = [];
 
 	const flush = () => {
-		if (operator === 'push') {
-			statements.push(
-				b.stmt(
-					b.call(
-						b.member(out, b.id('push')),
-						b.template(
-							strings.map((cooked, i) => b.quasi(cooked, i === strings.length - 1)),
-							expressions
-						)
+		statements.push(
+			b.stmt(
+				b.call(
+					b.id('$$payload.push'),
+					b.template(
+						strings.map((cooked, i) => b.quasi(cooked, i === strings.length - 1)),
+						expressions
 					)
 				)
-			);
-		} else {
-			statements.push(
-				b.stmt(
-					b.assignment(
-						operator,
-						out,
-						b.template(
-							strings.map((cooked, i) => b.quasi(cooked, i === strings.length - 1)),
-							expressions
-						)
-					)
-				)
-			);
-		}
+			)
+		);
+
 		strings = [];
 		expressions = [];
 	};
@@ -180,13 +172,15 @@ export function build_template(template, out = b.id('$$payload.out'), operator =
  * @param {ComponentContext} context
  * @param {boolean} trim_whitespace
  * @param {boolean} is_component
+ * @param {(expression: Expression, metadata: ExpressionMetadata) => Expression} transform
  * @returns {Expression}
  */
 export function build_attribute_value(
 	value,
 	context,
 	trim_whitespace = false,
-	is_component = false
+	is_component = false,
+	transform = (expression) => expression
 ) {
 	if (value === true) {
 		return b.true;
@@ -203,7 +197,10 @@ export function build_attribute_value(
 			return b.literal(is_component ? data : escape_html(data, true));
 		}
 
-		return /** @type {Expression} */ (context.visit(chunk.expression));
+		return transform(
+			/** @type {Expression} */ (context.visit(chunk.expression)),
+			chunk.metadata.expression
+		);
 	}
 
 	let quasi = b.quasi('', false);
@@ -221,7 +218,13 @@ export function build_attribute_value(
 				: node.data;
 		} else {
 			expressions.push(
-				b.call('$.stringify', /** @type {Expression} */ (context.visit(node.expression)))
+				b.call(
+					'$.stringify',
+					transform(
+						/** @type {Expression} */ (context.visit(node.expression)),
+						node.metadata.expression
+					)
+				)
 			);
 
 			quasi = b.quasi('', i + 1 === value.length);
@@ -257,3 +260,61 @@ export function build_getter(node, state) {
 
 	return node;
 }
+
+/**
+ * @param {BlockStatement | Expression} body
+ * @param {boolean} async
+ * @returns {Statement}
+ */
+export function call_child_payload(body, async) {
+	return b.stmt(b.call('$$payload.child', b.arrow([b.id('$$payload')], body, async)));
+}
+
+/**
+ * @param {BlockStatement | Expression} body
+ * @param {Identifier | false} component_fn_id
+ * @returns {Statement}
+ */
+export function call_component_payload(body, component_fn_id) {
+	return b.stmt(
+		b.call('$$payload.component', b.arrow([b.id('$$payload')], body, false), component_fn_id)
+	);
+}
+
+export class PromiseOptimiser {
+	/** @type {Expression[]} */
+	expressions = [];
+
+	/**
+	 *
+	 * @param {Expression} expression
+	 * @param {ExpressionMetadata} metadata
+	 */
+	transform = (expression, metadata) => {
+		if (metadata.has_await) {
+			const length = this.expressions.push(expression);
+			return b.id(`$$${length - 1}`);
+		}
+
+		return expression;
+	};
+
+	apply() {
+		if (this.expressions.length === 1) {
+			return b.const('$$0', this.expressions[0]);
+		}
+
+		const promises = b.array(
+			this.expressions.map((expression) => {
+				return expression.type === 'AwaitExpression' && !has_await(expression.argument)
+					? expression.argument
+					: b.call(b.thunk(expression, true));
+			})
+		);
+
+		return b.const(
+			b.array_pattern(this.expressions.map((_, i) => b.id(`$$${i}`))),
+			b.await(b.call('Promise.all', promises))
+		);
+	}
+}
diff --git a/packages/svelte/src/compiler/phases/types.d.ts b/packages/svelte/src/compiler/phases/types.d.ts
index 4da78f1482..4e287fd199 100644
--- a/packages/svelte/src/compiler/phases/types.d.ts
+++ b/packages/svelte/src/compiler/phases/types.d.ts
@@ -1,10 +1,10 @@
 import type { AST, Binding, StateField } from '#compiler';
 import type {
+	AwaitExpression,
 	CallExpression,
 	ClassBody,
 	Identifier,
 	LabeledStatement,
-	Node,
 	Program
 } from 'estree';
 import type { Scope, ScopeRoot } from './scope.js';
@@ -47,6 +47,8 @@ export interface Analysis {
 
 	/** A set of deriveds that contain `await` expressions */
 	async_deriveds: Set<CallExpression>;
+	/** Awaits needing context preservation */
+	pickled_awaits: Set<AwaitExpression>;
 }
 
 export interface ComponentAnalysis extends Analysis {
diff --git a/packages/svelte/src/compiler/types/template.d.ts b/packages/svelte/src/compiler/types/template.d.ts
index 060df2dcb2..42048c3525 100644
--- a/packages/svelte/src/compiler/types/template.d.ts
+++ b/packages/svelte/src/compiler/types/template.d.ts
@@ -344,6 +344,8 @@ export namespace AST {
 			has_spread: boolean;
 			scoped: boolean;
 			path: SvelteNode[];
+			/** Synthetic value attribute for <option> with single expression child, used for client-only handling */
+			synthetic_value_node: ExpressionTag | null;
 		};
 	}
 
diff --git a/packages/svelte/src/compiler/utils/ast.js b/packages/svelte/src/compiler/utils/ast.js
index a20b6888c7..d988cd98fb 100644
--- a/packages/svelte/src/compiler/utils/ast.js
+++ b/packages/svelte/src/compiler/utils/ast.js
@@ -609,3 +609,19 @@ export function build_assignment_value(operator, left, right) {
 			? b.logical(/** @type {ESTree.LogicalOperator} */ (operator.slice(0, -1)), left, right)
 			: b.binary(/** @type {ESTree.BinaryOperator} */ (operator.slice(0, -1)), left, right);
 }
+
+/**
+ * @param {ESTree.Expression} expression
+ */
+export function has_await(expression) {
+	let has_await = false;
+
+	walk(expression, null, {
+		AwaitExpression(_node, context) {
+			has_await = true;
+			context.stop();
+		}
+	});
+
+	return has_await;
+}
diff --git a/packages/svelte/src/compiler/utils/builders.js b/packages/svelte/src/compiler/utils/builders.js
index 03a946ff9c..f69beed509 100644
--- a/packages/svelte/src/compiler/utils/builders.js
+++ b/packages/svelte/src/compiler/utils/builders.js
@@ -2,6 +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';
 
 /**
  * @param {Array<ESTree.Expression | ESTree.SpreadElement | null>} elements
@@ -443,16 +444,7 @@ 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') {
-		let has_await = false;
-
-		walk(expression.body.argument, null, {
-			AwaitExpression(_node, context) {
-				has_await = true;
-				context.stop();
-			}
-		});
-
-		if (!has_await) {
+		if (!has_await(expression.body.argument)) {
 			return unthunk(arrow(expression.params, expression.body.argument));
 		}
 	}
diff --git a/packages/svelte/src/index-server.js b/packages/svelte/src/index-server.js
index 1342e502d7..0b05fb6d12 100644
--- a/packages/svelte/src/index-server.js
+++ b/packages/svelte/src/index-server.js
@@ -1,12 +1,12 @@
-/** @import { Component } from '#server' */
-import { current_component } from './internal/server/context.js';
+/** @import { SSRContext } from '#server' */
+/** @import { Payload } from './internal/server/payload.js' */
+import { ssr_context } from './internal/server/context.js';
 import { noop } from './internal/shared/utils.js';
 import * as e from './internal/server/errors.js';
 
 /** @param {() => void} fn */
 export function onDestroy(fn) {
-	var context = /** @type {Component} */ (current_component);
-	(context.d ??= []).push(fn);
+	/** @type {Payload} */ (/** @type {SSRContext} */ (ssr_context).r).on_destroy(fn);
 }
 
 export {
diff --git a/packages/svelte/src/internal/client/dom/blocks/boundary.js b/packages/svelte/src/internal/client/dom/blocks/boundary.js
index 2a9736553c..0532f2ca1b 100644
--- a/packages/svelte/src/internal/client/dom/blocks/boundary.js
+++ b/packages/svelte/src/internal/client/dom/blocks/boundary.js
@@ -1,5 +1,11 @@
 /** @import { Effect, Source, TemplateNode, } from '#client' */
-import { BOUNDARY_EFFECT, EFFECT_PRESERVED, EFFECT_TRANSPARENT } from '#client/constants';
+import {
+	BOUNDARY_EFFECT,
+	COMMENT_NODE,
+	EFFECT_PRESERVED,
+	EFFECT_TRANSPARENT
+} from '#client/constants';
+import { HYDRATION_START_ELSE } from '../../../../constants.js';
 import { component_context, set_component_context } from '../../context.js';
 import { handle_error, invoke_error_boundary } from '../../error-handling.js';
 import { block, branch, destroy_effect, pause_effect } from '../../reactivity/effects.js';
@@ -57,8 +63,8 @@ export class Boundary {
 	/** @type {TemplateNode} */
 	#anchor;
 
-	/** @type {TemplateNode} */
-	#hydrate_open;
+	/** @type {TemplateNode | null} */
+	#hydrate_open = hydrating ? hydrate_node : null;
 
 	/** @type {BoundaryProps} */
 	#props;
@@ -83,6 +89,7 @@ export class Boundary {
 
 	#local_pending_count = 0;
 	#pending_count = 0;
+
 	#is_creating_fallback = false;
 
 	/**
@@ -122,8 +129,6 @@ export class Boundary {
 		this.#props = props;
 		this.#children = children;
 
-		this.#hydrate_open = hydrate_node;
-
 		this.parent = /** @type {Effect} */ (active_effect).b;
 
 		this.#pending = !!this.#props.pending;
@@ -132,34 +137,18 @@ export class Boundary {
 			/** @type {Effect} */ (active_effect).b = this;
 
 			if (hydrating) {
+				const comment = this.#hydrate_open;
 				hydrate_next();
-			}
 
-			const pending = this.#props.pending;
-
-			if (hydrating && pending) {
-				this.#pending_effect = branch(() => pending(this.#anchor));
-
-				// future work: when we have some form of async SSR, we will
-				// need to use hydration boundary comments to report whether
-				// the pending or main block was rendered for a given
-				// boundary, and hydrate accordingly
-				Batch.enqueue(() => {
-					this.#main_effect = this.#run(() => {
-						Batch.ensure();
-						return branch(() => this.#children(this.#anchor));
-					});
-
-					if (this.#pending_count > 0) {
-						this.#show_pending_snippet();
-					} else {
-						pause_effect(/** @type {Effect} */ (this.#pending_effect), () => {
-							this.#pending_effect = null;
-						});
+				const server_rendered_pending =
+					/** @type {Comment} */ (comment).nodeType === COMMENT_NODE &&
+					/** @type {Comment} */ (comment).data === HYDRATION_START_ELSE;
 
-						this.#pending = false;
-					}
-				});
+				if (server_rendered_pending) {
+					this.#hydrate_pending_content();
+				} else {
+					this.#hydrate_resolved_content();
+				}
 			} else {
 				try {
 					this.#main_effect = branch(() => children(this.#anchor));
@@ -180,6 +169,43 @@ export class Boundary {
 		}
 	}
 
+	#hydrate_resolved_content() {
+		try {
+			this.#main_effect = branch(() => this.#children(this.#anchor));
+		} catch (error) {
+			this.error(error);
+		}
+
+		// Since server rendered resolved content, we never show pending state
+		// Even if client-side async operations are still running, the content is already displayed
+		this.#pending = false;
+	}
+
+	#hydrate_pending_content() {
+		const pending = this.#props.pending;
+		if (!pending) {
+			return;
+		}
+		this.#pending_effect = branch(() => pending(this.#anchor));
+
+		Batch.enqueue(() => {
+			this.#main_effect = this.#run(() => {
+				Batch.ensure();
+				return branch(() => this.#children(this.#anchor));
+			});
+
+			if (this.#pending_count > 0) {
+				this.#show_pending_snippet();
+			} else {
+				pause_effect(/** @type {Effect} */ (this.#pending_effect), () => {
+					this.#pending_effect = null;
+				});
+
+				this.#pending = false;
+			}
+		});
+	}
+
 	/**
 	 * Returns `true` if the effect exists inside a boundary whose pending snippet is shown
 	 * @returns {boolean}
@@ -238,10 +264,10 @@ export class Boundary {
 		if (!this.has_pending_snippet()) {
 			if (this.parent) {
 				this.parent.#update_pending_count(d);
-				return;
 			}
 
-			e.await_outside_boundary();
+			// if there's no parent, we're in a scope with no pending snippet
+			return;
 		}
 
 		this.#pending_count += d;
@@ -307,7 +333,7 @@ export class Boundary {
 		}
 
 		if (hydrating) {
-			set_hydrate_node(this.#hydrate_open);
+			set_hydrate_node(/** @type {TemplateNode} */ (this.#hydrate_open));
 			next();
 			set_hydrate_node(remove_nodes());
 		}
@@ -330,7 +356,7 @@ export class Boundary {
 			// If the failure happened while flushing effects, current_batch can be null
 			Batch.ensure();
 
-			this.#pending_count = 0;
+			this.#local_pending_count = 0;
 
 			if (this.#failed_effect !== null) {
 				pause_effect(this.#failed_effect, () => {
@@ -338,7 +364,9 @@ export class Boundary {
 				});
 			}
 
-			this.#pending = true;
+			// we intentionally do not try to find the nearest pending boundary. If this boundary has one, we'll render it on reset
+			// but it would be really weird to show the parent's boundary on a child reset.
+			this.#pending = this.has_pending_snippet();
 
 			this.#main_effect = this.#run(() => {
 				this.#is_creating_fallback = false;
@@ -409,13 +437,7 @@ function move_effect(effect, fragment) {
 }
 
 export function get_boundary() {
-	const boundary = /** @type {Effect} */ (active_effect).b;
-
-	if (boundary === null) {
-		e.await_outside_boundary();
-	}
-
-	return boundary;
+	return /** @type {Boundary} */ (/** @type {Effect} */ (active_effect).b);
 }
 
 export function pending() {
diff --git a/packages/svelte/src/internal/client/reactivity/async.js b/packages/svelte/src/internal/client/reactivity/async.js
index a109a1f4d8..018ab701f2 100644
--- a/packages/svelte/src/internal/client/reactivity/async.js
+++ b/packages/svelte/src/internal/client/reactivity/async.js
@@ -39,7 +39,6 @@ export function flatten(sync, async, fn) {
 	var parent = /** @type {Effect} */ (active_effect);
 
 	var restore = capture();
-	var boundary = get_boundary();
 
 	Promise.all(async.map((expression) => async_derived(expression)))
 		.then((result) => {
@@ -60,7 +59,7 @@ export function flatten(sync, async, fn) {
 			unset_context();
 		})
 		.catch((error) => {
-			boundary.error(error);
+			invoke_error_boundary(error, parent);
 		});
 }
 
diff --git a/packages/svelte/src/internal/client/render.js b/packages/svelte/src/internal/client/render.js
index c5015875a8..0910c6d06c 100644
--- a/packages/svelte/src/internal/client/render.js
+++ b/packages/svelte/src/internal/client/render.js
@@ -11,7 +11,7 @@ import {
 import { HYDRATION_END, HYDRATION_ERROR, HYDRATION_START } from '../../constants.js';
 import { active_effect } from './runtime.js';
 import { push, pop, component_context } from './context.js';
-import { component_root, branch } from './reactivity/effects.js';
+import { component_root } from './reactivity/effects.js';
 import {
 	hydrate_next,
 	hydrate_node,
@@ -31,6 +31,7 @@ import * as e from './errors.js';
 import { assign_nodes } from './dom/template.js';
 import { is_passive_event } from '../../utils.js';
 import { COMMENT_NODE } from './constants.js';
+import { boundary } from './dom/blocks/boundary.js';
 
 /**
  * This is normally true — block effects should run their intro transitions —
@@ -218,35 +219,41 @@ function _mount(Component, { target, anchor, props = {}, events, context, intro
 	var unmount = component_root(() => {
 		var anchor_node = anchor ?? target.appendChild(create_text());
 
-		branch(() => {
-			if (context) {
-				push({});
-				var ctx = /** @type {ComponentContext} */ (component_context);
-				ctx.c = context;
-			}
+		boundary(
+			/** @type {TemplateNode} */ (anchor_node),
+			{
+				pending: () => {}
+			},
+			(anchor_node) => {
+				if (context) {
+					push({});
+					var ctx = /** @type {ComponentContext} */ (component_context);
+					ctx.c = context;
+				}
 
-			if (events) {
-				// We can't spread the object or else we'd lose the state proxy stuff, if it is one
-				/** @type {any} */ (props).$$events = events;
-			}
+				if (events) {
+					// We can't spread the object or else we'd lose the state proxy stuff, if it is one
+					/** @type {any} */ (props).$$events = events;
+				}
 
-			if (hydrating) {
-				assign_nodes(/** @type {TemplateNode} */ (anchor_node), null);
-			}
+				if (hydrating) {
+					assign_nodes(/** @type {TemplateNode} */ (anchor_node), null);
+				}
 
-			should_intro = intro;
-			// @ts-expect-error the public typings are not what the actual function looks like
-			component = Component(anchor_node, props) || {};
-			should_intro = true;
+				should_intro = intro;
+				// @ts-expect-error the public typings are not what the actual function looks like
+				component = Component(anchor_node, props) || {};
+				should_intro = true;
 
-			if (hydrating) {
-				/** @type {Effect} */ (active_effect).nodes_end = hydrate_node;
-			}
+				if (hydrating) {
+					/** @type {Effect} */ (active_effect).nodes_end = hydrate_node;
+				}
 
-			if (context) {
-				pop();
+				if (context) {
+					pop();
+				}
 			}
-		});
+		);
 
 		return () => {
 			for (var event_name of registered_events) {
diff --git a/packages/svelte/src/internal/server/blocks/snippet.js b/packages/svelte/src/internal/server/blocks/snippet.js
index bb82ca97d0..109dbf683a 100644
--- a/packages/svelte/src/internal/server/blocks/snippet.js
+++ b/packages/svelte/src/internal/server/blocks/snippet.js
@@ -15,7 +15,7 @@ export function createRawSnippet(fn) {
 	// @ts-expect-error the types are a lie
 	return (/** @type {Payload} */ payload, /** @type {Params} */ ...args) => {
 		var getters = /** @type {Getters<Params>} */ (args.map((value) => () => value));
-		payload.out.push(
+		payload.push(
 			fn(...getters)
 				.render()
 				.trim()
diff --git a/packages/svelte/src/internal/server/context.js b/packages/svelte/src/internal/server/context.js
index bae93beb53..c59b2d260a 100644
--- a/packages/svelte/src/internal/server/context.js
+++ b/packages/svelte/src/internal/server/context.js
@@ -1,10 +1,14 @@
-/** @import { Component } from '#server' */
+/** @import { SSRContext } from '#server' */
 import { DEV } from 'esm-env';
-import { on_destroy } from './index.js';
 import * as e from './errors.js';
 
-/** @type {Component | null} */
-export var current_component = null;
+/** @type {SSRContext | null} */
+export var ssr_context = null;
+
+/** @param {SSRContext | null} v */
+export function set_ssr_context(v) {
+	ssr_context = v;
+}
 
 /**
  * @template T
@@ -47,42 +51,35 @@ export function getAllContexts() {
  * @returns {Map<unknown, unknown>}
  */
 function get_or_init_context_map(name) {
-	if (current_component === null) {
+	if (ssr_context === null) {
 		e.lifecycle_outside_component(name);
 	}
 
-	return (current_component.c ??= new Map(get_parent_context(current_component) || undefined));
+	return (ssr_context.c ??= new Map(get_parent_context(ssr_context) || undefined));
 }
 
 /**
  * @param {Function} [fn]
  */
 export function push(fn) {
-	current_component = { p: current_component, c: null, d: null };
+	ssr_context = { p: ssr_context, c: null, r: null };
+
 	if (DEV) {
-		// component function
-		current_component.function = fn;
+		ssr_context.function = fn;
+		ssr_context.element = ssr_context.p?.element;
 	}
 }
 
 export function pop() {
-	var component = /** @type {Component} */ (current_component);
-
-	var ondestroy = component.d;
-
-	if (ondestroy) {
-		on_destroy.push(...ondestroy);
-	}
-
-	current_component = component.p;
+	ssr_context = /** @type {SSRContext} */ (ssr_context).p;
 }
 
 /**
- * @param {Component} component_context
+ * @param {SSRContext} ssr_context
  * @returns {Map<unknown, unknown> | null}
  */
-function get_parent_context(component_context) {
-	let parent = component_context.p;
+function get_parent_context(ssr_context) {
+	let parent = ssr_context.p;
 
 	while (parent !== null) {
 		const context_map = parent.c;
@@ -94,3 +91,22 @@ function get_parent_context(component_context) {
 
 	return null;
 }
+
+/**
+ * Wraps an `await` expression in such a way that the component context that was
+ * active before the expression evaluated can be reapplied afterwards —
+ * `await a + b()` becomes `(await $.save(a))() + b()`, meaning `b()` will have access
+ * to the context of its component.
+ * @template T
+ * @param {Promise<T>} promise
+ * @returns {Promise<() => T>}
+ */
+export async function save(promise) {
+	var previous_context = ssr_context;
+	var value = await promise;
+
+	return () => {
+		ssr_context = previous_context;
+		return value;
+	};
+}
diff --git a/packages/svelte/src/internal/server/dev.js b/packages/svelte/src/internal/server/dev.js
index 2a0cb057a3..cc9f6496c0 100644
--- a/packages/svelte/src/internal/server/dev.js
+++ b/packages/svelte/src/internal/server/dev.js
@@ -1,30 +1,29 @@
-/** @import { Component } from '#server' */
+/** @import { SSRContext } from '#server' */
 import { FILENAME } from '../../constants.js';
 import {
 	is_tag_valid_with_ancestor,
 	is_tag_valid_with_parent
 } from '../../html-tree-validation.js';
-import { current_component } from './context.js';
+import { set_ssr_context, ssr_context } from './context.js';
 import * as e from './errors.js';
-import { HeadPayload, Payload } from './payload.js';
+import { Payload } from './payload.js';
 
+// TODO move this
 /**
  * @typedef {{
  * 	tag: string;
- * 	parent: null | Element;
- *  filename: null | string;
+ * 	parent: undefined | Element;
+ *  filename: undefined | string;
  *  line: number;
  *  column: number;
  * }} Element
  */
 
 /**
- * @type {Element | null}
+ * This is exported so that it can be cleared between tests
+ * @type {Set<string>}
  */
-let parent = null;
-
-/** @type {Set<string>} */
-let seen;
+export let seen;
 
 /**
  * @param {Payload} payload
@@ -40,15 +39,10 @@ function print_error(payload, message) {
 
 	// eslint-disable-next-line no-console
 	console.error(message);
-	payload.head.out.push(`<script>console.error(${JSON.stringify(message)})</script>`);
-}
-
-export function reset_elements() {
-	let old_parent = parent;
-	parent = null;
-	return () => {
-		parent = old_parent;
-	};
+	payload.child(
+		(payload) => payload.push(`<script>console.error(${JSON.stringify(message)})</script>`),
+		'head'
+	);
 }
 
 /**
@@ -58,10 +52,12 @@ export function reset_elements() {
  * @param {number} column
  */
 export function push_element(payload, tag, line, column) {
-	var filename = /** @type {Component} */ (current_component).function[FILENAME];
-	var child = { tag, parent, filename, line, column };
+	var context = /** @type {SSRContext} */ (ssr_context);
+	var filename = context.function[FILENAME];
+	var parent = context.element;
+	var element = { tag, parent, filename, line, column };
 
-	if (parent !== null) {
+	if (parent !== undefined) {
 		var ancestor = parent.parent;
 		var ancestors = [parent.tag];
 
@@ -86,11 +82,11 @@ export function push_element(payload, tag, line, column) {
 		}
 	}
 
-	parent = child;
+	set_ssr_context({ ...context, p: context, element });
 }
 
 export function pop_element() {
-	parent = /** @type {Element} */ (parent).parent;
+	set_ssr_context(/** @type {SSRContext} */ (ssr_context).p);
 }
 
 /**
@@ -100,7 +96,7 @@ export function validate_snippet_args(payload) {
 	if (
 		typeof payload !== 'object' ||
 		// for some reason typescript consider the type of payload as never after the first instanceof
-		!(payload instanceof Payload || /** @type {any} */ (payload) instanceof HeadPayload)
+		!(payload instanceof Payload)
 	) {
 		e.invalid_snippet_arguments();
 	}
diff --git a/packages/svelte/src/internal/server/errors.js b/packages/svelte/src/internal/server/errors.js
index 458937218f..bde49fe935 100644
--- a/packages/svelte/src/internal/server/errors.js
+++ b/packages/svelte/src/internal/server/errors.js
@@ -2,6 +2,30 @@
 
 export *  from '../shared/errors.js';
 
+/**
+ * Encountered asynchronous work while rendering synchronously.
+ * @returns {never}
+ */
+export function await_invalid() {
+	const error = new Error(`await_invalid\nEncountered asynchronous work while rendering synchronously.\nhttps://svelte.dev/e/await_invalid`);
+
+	error.name = 'Svelte error';
+
+	throw error;
+}
+
+/**
+ * The `html` property of server render results has been deprecated. Use `body` instead.
+ * @returns {never}
+ */
+export function html_deprecated() {
+	const error = new Error(`html_deprecated\nThe \`html\` property of server render results has been deprecated. Use \`body\` instead.\nhttps://svelte.dev/e/html_deprecated`);
+
+	error.name = 'Svelte error';
+
+	throw error;
+}
+
 /**
  * `%name%(...)` is not available on the server
  * @param {string} name
diff --git a/packages/svelte/src/internal/server/index.js b/packages/svelte/src/internal/server/index.js
index 3aa44f2daa..a2cf222da6 100644
--- a/packages/svelte/src/internal/server/index.js
+++ b/packages/svelte/src/internal/server/index.js
@@ -1,6 +1,7 @@
-/** @import { ComponentType, SvelteComponent } from 'svelte' */
-/** @import { Component, RenderOutput } from '#server' */
+/** @import { ComponentType, SvelteComponent, Component } from 'svelte' */
+/** @import { RenderOutput, SSRContext } from '#server' */
 /** @import { Store } from '#shared' */
+/** @import { AccumulatedContent } from './payload.js' */
 export { FILENAME, HMR } from '../../constants.js';
 import { attr, clsx, to_class, to_style } from '../shared/attributes.js';
 import { is_promise, noop } from '../shared/utils.js';
@@ -13,13 +14,14 @@ import {
 } from '../../constants.js';
 import { escape_html } from '../../escaping.js';
 import { DEV } from 'esm-env';
-import { current_component, pop, push } from './context.js';
+import { ssr_context, pop, push, set_ssr_context } from './context.js';
 import { EMPTY_COMMENT, BLOCK_CLOSE, BLOCK_OPEN, BLOCK_OPEN_ELSE } from './hydration.js';
 import { validate_store } from '../shared/validate.js';
 import { is_boolean_attribute, is_raw_text_element, is_void } from '../../utils.js';
-import { reset_elements } from './dev.js';
-import { Payload } from './payload.js';
+import { Payload, SSRState } from './payload.js';
 import { abort } from './abort-signal.js';
+import { async_mode_flag } from '../flags/index.js';
+import * as e from './errors.js';
 
 // https://html.spec.whatwg.org/multipage/syntax.html#attributes-2
 // https://infra.spec.whatwg.org/#noncharacter
@@ -34,102 +36,48 @@ const INVALID_ATTR_NAME_CHAR_REGEX =
  * @returns {void}
  */
 export function element(payload, tag, attributes_fn = noop, children_fn = noop) {
-	payload.out.push('<!---->');
+	payload.push('<!---->');
 
 	if (tag) {
-		payload.out.push(`<${tag}`);
+		payload.push(`<${tag}`);
 		attributes_fn();
-		payload.out.push(`>`);
+		payload.push(`>`);
 
 		if (!is_void(tag)) {
 			children_fn();
 			if (!is_raw_text_element(tag)) {
-				payload.out.push(EMPTY_COMMENT);
+				payload.push(EMPTY_COMMENT);
 			}
-			payload.out.push(`</${tag}>`);
+			payload.push(`</${tag}>`);
 		}
 	}
 
-	payload.out.push('<!---->');
+	payload.push('<!---->');
 }
 
-/**
- * Array of `onDestroy` callbacks that should be called at the end of the server render function
- * @type {Function[]}
- */
-export let on_destroy = [];
-
 /**
  * Only available on the server and when compiling with the `server` option.
  * Takes a component and returns an object with `body` and `head` properties on it, which you can use to populate the HTML when server-rendering your app.
  * @template {Record<string, any>} Props
- * @param {import('svelte').Component<Props> | ComponentType<SvelteComponent<Props>>} component
+ * @param {Component<Props> | ComponentType<SvelteComponent<Props>>} component
  * @param {{ props?: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any>; idPrefix?: string }} [options]
  * @returns {RenderOutput}
  */
 export function render(component, options = {}) {
-	try {
-		const payload = new Payload(options.idPrefix ? options.idPrefix + '-' : '');
-
-		const prev_on_destroy = on_destroy;
-		on_destroy = [];
-		payload.out.push(BLOCK_OPEN);
-
-		let reset_reset_element;
-
-		if (DEV) {
-			// prevent parent/child element state being corrupted by a bad render
-			reset_reset_element = reset_elements();
-		}
-
-		if (options.context) {
-			push();
-			/** @type {Component} */ (current_component).c = options.context;
-		}
-
-		// @ts-expect-error
-		component(payload, options.props ?? {}, {}, {});
-
-		if (options.context) {
-			pop();
-		}
-
-		if (reset_reset_element) {
-			reset_reset_element();
-		}
-
-		payload.out.push(BLOCK_CLOSE);
-		for (const cleanup of on_destroy) cleanup();
-		on_destroy = prev_on_destroy;
-
-		let head = payload.head.out.join('') + payload.head.title;
-
-		for (const { hash, code } of payload.css) {
-			head += `<style id="${hash}">${code}</style>`;
-		}
-
-		const body = payload.out.join('');
-
-		return {
-			head,
-			html: body,
-			body: body
-		};
-	} finally {
-		abort();
-	}
+	return Payload.render(/** @type {Component<Props>} */ (component), options);
 }
 
 /**
  * @param {Payload} payload
- * @param {(head_payload: Payload['head']) => void} fn
+ * @param {(payload: Payload) => Promise<void> | void} fn
  * @returns {void}
  */
 export function head(payload, fn) {
-	const head_payload = payload.head;
-	head_payload.out.push(BLOCK_OPEN);
-	fn(head_payload);
-	head_payload.out.push(BLOCK_CLOSE);
+	payload.child((payload) => {
+		payload.push(BLOCK_OPEN);
+		payload.child(fn);
+		payload.push(BLOCK_CLOSE);
+	}, 'head');
 }
 
 /**
@@ -144,21 +92,21 @@ export function css_props(payload, is_html, props, component, dynamic = false) {
 	const styles = style_object_to_string(props);
 
 	if (is_html) {
-		payload.out.push(`<svelte-css-wrapper style="display: contents; ${styles}">`);
+		payload.push(`<svelte-css-wrapper style="display: contents; ${styles}">`);
 	} else {
-		payload.out.push(`<g style="${styles}">`);
+		payload.push(`<g style="${styles}">`);
 	}
 
 	if (dynamic) {
-		payload.out.push('<!---->');
+		payload.push('<!---->');
 	}
 
 	component();
 
 	if (is_html) {
-		payload.out.push(`<!----></svelte-css-wrapper>`);
+		payload.push(`<!----></svelte-css-wrapper>`);
 	} else {
-		payload.out.push(`<!----></g>`);
+		payload.push(`<!----></g>`);
 	}
 }
 
@@ -451,13 +399,13 @@ export function bind_props(props_parent, props_now) {
  */
 function await_block(payload, promise, pending_fn, then_fn) {
 	if (is_promise(promise)) {
-		payload.out.push(BLOCK_OPEN);
+		payload.push(BLOCK_OPEN);
 		promise.then(null, noop);
 		if (pending_fn !== null) {
 			pending_fn();
 		}
 	} else if (then_fn !== null) {
-		payload.out.push(BLOCK_OPEN_ELSE);
+		payload.push(BLOCK_OPEN_ELSE);
 		then_fn(promise);
 	}
 }
@@ -503,8 +451,8 @@ export function once(get_value) {
  * @returns {string}
  */
 export function props_id(payload) {
-	const uid = payload.uid();
-	payload.out.push('<!--#' + uid + '-->');
+	const uid = payload.global.uid();
+	payload.push('<!--#' + uid + '-->');
 	return uid;
 }
 
@@ -512,12 +460,10 @@ export { attr, clsx };
 
 export { html } from './blocks/html.js';
 
-export { push, pop } from './context.js';
+export { save } from './context.js';
 
 export { push_element, pop_element, validate_snippet_args } from './dev.js';
 
-export { assign_payload, copy_payload } from './payload.js';
-
 export { snapshot } from '../shared/clone.js';
 
 export { fallback, to_array } from '../shared/utils.js';
@@ -531,8 +477,6 @@ export {
 
 export { escape_html as escape };
 
-export { await_outside_boundary } from '../shared/errors.js';
-
 /**
  * @template T
  * @param {()=>T} fn
@@ -557,29 +501,117 @@ export function derived(fn) {
 /**
  *
  * @param {Payload} payload
- * @param {*} value
+ * @param {unknown} value
  */
 export function maybe_selected(payload, value) {
-	return value === payload.select_value ? ' selected' : '';
+	return value === payload.local.select_value ? ' selected' : '';
 }
 
 /**
+ * When an `option` element has no `value` attribute, we need to treat the child
+ * content as its `value` to determine whether we should apply the `selected` attribute.
+ * This has to be done at runtime, for hopefully obvious reasons. It is also complicated,
+ * for sad reasons.
  * @param {Payload} payload
- * @param {() => void} children
+ * @param {((payload: Payload) => void | Promise<void>)} children
  * @returns {void}
  */
 export function valueless_option(payload, children) {
-	var i = payload.out.length;
+	const i = payload.length;
+
+	// prior to children, `payload` has some combination of string/unresolved payload that ends in `<option ...>`
+	payload.child(children);
+
+	// post-children, `payload` has child content, possibly also with some number of hydration comments.
+	// we can compact this last chunk of content to see if it matches the select value...
+	payload.compact({
+		start: i,
+		fn: (content) => {
+			if (content.body.replace(/<!---->/g, '') === payload.local.select_value) {
+				// ...and if it does match the select value, we can compact the part of the payload representing the `<option ...>`
+				// to add the `selected` attribute to the end.
+				payload.compact({
+					start: i - 1,
+					end: i,
+					fn: (content) => {
+						return { body: content.body.slice(0, -1) + ' selected>', head: content.head };
+					}
+				});
+			}
+			return content;
+		}
+	});
+}
 
-	children();
+/**
+ * In the special case where an `option` element has no `value` attribute but
+ * the children of the `option` element are a single expression, we can simplify
+ * by running the children and passing the resulting value, which means
+ * we don't have to do all of the same parsing nonsense. It also means we can avoid
+ * coercing everything to a string.
+ * @param {Payload} payload
+ * @param {(() => unknown)} child
+ */
+export function simple_valueless_option(payload, child) {
+	const result = child();
 
-	var body = payload.out.slice(i).join('');
+	/**
+	 * @param {AccumulatedContent} content
+	 * @param {unknown} child_value
+	 * @returns {AccumulatedContent}
+	 */
+	const mark_selected = (content, child_value) => {
+		if (child_value === payload.local.select_value) {
+			return { body: content.body.slice(0, -1) + ' selected>', head: content.head };
+		}
+		return content;
+	};
 
-	if (body.replace(/<!---->/g, '') === payload.select_value) {
-		// replace '>' with ' selected>' (closing tag will be added later)
-		var last_item = payload.out[i - 1];
-		payload.out[i - 1] = last_item.slice(0, -1) + ' selected>';
-		// Remove the old items after position i and add the body as a single item
-		payload.out.splice(i, payload.out.length - i, body);
-	}
+	payload.compact({
+		start: payload.length - 1,
+		fn: (content) => {
+			if (result instanceof Promise) {
+				return result.then((child_value) => mark_selected(content, child_value));
+			}
+			return mark_selected(content, result);
+		}
+	});
+
+	payload.child((child_payload) => {
+		if (result instanceof Promise) {
+			return result.then((child_value) => {
+				child_payload.push(escape_html(child_value));
+			});
+		}
+		child_payload.push(escape_html(result));
+	});
+}
+
+/**
+ * Since your document can only have one `title`, we have to have some sort of algorithm for determining
+ * which one "wins". To do this, we perform a depth-first comparison of where the title was encountered --
+ * later ones "win" over earlier ones, regardless of what order the promises resolve in. To accomodate this, we:
+ * - Figure out where we are in the content tree (`get_path`)
+ * - Render the title in its own child so that it has a defined "slot" in the payload
+ * - Compact that spot so that we get the entire rendered contents of the title
+ * - Attempt to set the global title (this is where the "wins" logic based on the path happens)
+ *
+ * TODO we could optimize this by not even rendering the title if the path wouldn't be accepted
+ *
+ * @param {Payload} payload
+ * @param {((payload: Payload) => void | Promise<void>)} children
+ */
+export function build_title(payload, children) {
+	const path = payload.get_path();
+	const i = payload.length;
+	payload.child(children);
+	payload.compact({
+		start: i,
+		fn: ({ head }) => {
+			payload.global.set_title(head, path);
+			// since we can only ever render the title in this chunk, and title rendering is handled specially,
+			// we can just ditch the results after we've saved them globally
+			return { head: '', body: '' };
+		}
+	});
 }
diff --git a/packages/svelte/src/internal/server/payload.js b/packages/svelte/src/internal/server/payload.js
index a7e40ad1db..ce8f312c21 100644
--- a/packages/svelte/src/internal/server/payload.js
+++ b/packages/svelte/src/internal/server/payload.js
@@ -1,80 +1,573 @@
-export class HeadPayload {
-	/** @type {Set<{ hash: string; code: string }>} */
-	css = new Set();
-	/** @type {string[]} */
-	out = [];
-	uid = () => '';
-	title = '';
-
-	constructor(
-		/** @type {Set<{ hash: string; code: string }>} */ css = new Set(),
-		/** @type {string[]} */ out = [],
-		title = '',
-		uid = () => ''
-	) {
-		this.css = css;
-		this.out = out;
-		this.title = title;
-		this.uid = uid;
+/** @import { Component } from 'svelte' */
+/** @import { RenderOutput, SSRContext, SyncRenderOutput } from './types.js' */
+import { async_mode_flag } from '../flags/index.js';
+import { abort } from './abort-signal.js';
+import { pop, push, set_ssr_context, ssr_context } from './context.js';
+import * as e from './errors.js';
+import * as w from './warnings.js';
+import { BLOCK_CLOSE, BLOCK_OPEN } from './hydration.js';
+
+/** @typedef {'head' | 'body'} PayloadType */
+/** @typedef {{ [key in PayloadType]: string }} AccumulatedContent */
+/**
+ * @template T
+ * @typedef {T | Promise<T>} MaybePromise<T>
+ */
+/**
+ * @typedef {string | Payload} PayloadItem
+ */
+
+/**
+ * Payloads are basically a tree of `string | Payload`s, where each `Payload` in the tree represents
+ * work that may or may not have completed. A payload can be {@link collect}ed to aggregate the
+ * content from itself and all of its children, but this will throw if any of the children are
+ * performing asynchronous work. To asynchronously collect a payload, just `await` it.
+ *
+ * The `string` values within a payload are always associated with the {@link type} of that payload. To switch types,
+ * call {@link child} with a different `type` argument.
+ */
+export class Payload {
+	/**
+	 * The contents of the payload.
+	 * @type {PayloadItem[]}
+	 */
+	#out = [];
+
+	/**
+	 * Any `onDestroy` callbacks registered during execution of this payload.
+	 * @type {(() => void)[] | undefined}
+	 */
+	#on_destroy = undefined;
+
+	/**
+	 * Whether this payload is a component body.
+	 * @type {boolean}
+	 */
+	#is_component_body = false;
+
+	/**
+	 * The type of string content that this payload is accumulating.
+	 * @type {PayloadType}
+	 */
+	type;
+
+	/** @type {Payload | undefined} */
+	#parent;
+
+	/**
+	 * Asynchronous work associated with this payload. `initial` is the promise from the function
+	 * this payload was passed to (if that function was async), and `followup` is any any additional
+	 * work from `compact` calls that needs to complete prior to collecting this payload's content.
+	 * @type {{ initial: Promise<void> | undefined, followup: Promise<void>[] }}
+	 */
+	promises = { initial: undefined, followup: [] };
+
+	/**
+	 * State which is associated with the content tree as a whole.
+	 * It will be re-exposed, uncopied, on all children.
+	 * @type {SSRState}
+	 * @readonly
+	 */
+	global;
+
+	/**
+	 * State that is local to the branch it is declared in.
+	 * It will be shallow-copied to all children.
+	 *
+	 * @type {{ select_value: string | undefined }}
+	 */
+	local;
+
+	/**
+	 * @param {SSRState} global
+	 * @param {Payload | undefined} [parent]
+	 * @param {PayloadType} [type]
+	 */
+	constructor(global, parent, type) {
+		this.global = global;
+		this.local = parent ? { ...parent.local } : { select_value: undefined };
+		this.#parent = parent;
+		this.type = type ?? parent?.type ?? 'body';
+	}
+
+	/**
+	 * Create a child payload. The child payload inherits the state from the parent,
+	 * but has its own content.
+	 * @param {(payload: Payload) => MaybePromise<void>} fn
+	 * @param {PayloadType} [type]
+	 */
+	child(fn, type) {
+		const child = new Payload(this.global, this, type);
+		this.#out.push(child);
+
+		const parent = ssr_context;
+
+		set_ssr_context({
+			...ssr_context,
+			p: parent,
+			c: null,
+			r: child
+		});
+
+		const result = fn(child);
+
+		set_ssr_context(parent);
+
+		if (result instanceof Promise) {
+			if (child.global.mode === 'sync') {
+				e.await_invalid();
+			}
+			// just to avoid unhandled promise rejections -- we'll end up throwing in `collect_async` if something fails
+			result.catch(() => {});
+			child.promises.initial = result;
+		}
+
+		return child;
+	}
+
+	/**
+	 * Create a component payload. The component payload inherits the state from the parent,
+	 * but has its own content. It is treated as an ordering boundary for ondestroy callbacks.
+	 * @param {(payload: Payload) => MaybePromise<void>} fn
+	 * @param {Function} [component_fn]
+	 * @returns {void}
+	 */
+	component(fn, component_fn) {
+		push(component_fn);
+		const child = this.child(fn);
+		child.#is_component_body = true;
+		pop();
+	}
+
+	/**
+	 * @param {string | (() => Promise<string>)} content
+	 */
+	push(content) {
+		if (typeof content === 'function') {
+			this.child(async (payload) => payload.push(await content()));
+		} else {
+			this.#out.push(content);
+		}
+	}
+
+	/**
+	 * Compact everything between `start` and `end` into a single payload, then call `fn` with the result of that payload.
+	 * The compacted payload will be sync if all of the children are sync and {@link fn} is sync, otherwise it will be async.
+	 * @param {{ start: number, end?: number, fn: (content: AccumulatedContent) => AccumulatedContent | Promise<AccumulatedContent> }} args
+	 */
+	compact({ start, end = this.#out.length, fn }) {
+		const child = new Payload(this.global, this);
+		const to_compact = this.#out.splice(start, end - start, child);
+
+		if (this.global.mode === 'sync') {
+			Payload.#compact(fn, child, to_compact, this.type);
+		} else {
+			this.promises.followup.push(Payload.#compact_async(fn, child, to_compact, this.type));
+		}
+	}
+
+	/**
+	 * @param {() => void} fn
+	 */
+	on_destroy(fn) {
+		(this.#on_destroy ??= []).push(fn);
+	}
+
+	/**
+	 * @returns {number[]}
+	 */
+	get_path() {
+		return this.#parent ? [...this.#parent.get_path(), this.#parent.#out.indexOf(this)] : [];
+	}
+
+	/**
+	 * @deprecated this is needed for legacy component bindings
+	 */
+	copy() {
+		const copy = new Payload(this.global, this.#parent, this.type);
+		copy.#out = this.#out.map((item) => (item instanceof Payload ? item.copy() : item));
+		copy.promises = this.promises;
+		return copy;
+	}
+
+	/**
+	 * @param {Payload} other
+	 * @deprecated this is needed for legacy component bindings
+	 */
+	subsume(other) {
+		if (this.global.mode !== other.global.mode) {
+			throw new Error(
+				"invariant: A payload cannot switch modes. If you're seeing this, there's a compiler bug. File an issue!"
+			);
+		}
+
+		this.local = other.local;
+		this.#out = other.#out.map((item) => {
+			if (item instanceof Payload) {
+				item.subsume(item);
+			}
+			return item;
+		});
+		this.promises = other.promises;
+		this.type = other.type;
+	}
+
+	get length() {
+		return this.#out.length;
+	}
+
+	/**
+	 * Only available on the server and when compiling with the `server` option.
+	 * Takes a component and returns an object with `body` and `head` properties on it, which you can use to populate the HTML when server-rendering your app.
+	 * @template {Record<string, any>} Props
+	 * @param {Component<Props>} component
+	 * @param {{ props?: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any>; idPrefix?: string }} [options]
+	 * @returns {RenderOutput}
+	 */
+	static render(component, options = {}) {
+		/** @type {AccumulatedContent | undefined} */
+		let sync;
+		/** @type {Promise<AccumulatedContent> | undefined} */
+		let async;
+
+		const result = /** @type {RenderOutput} */ ({});
+		// making these properties non-enumerable so that console.logging
+		// doesn't trigger a sync render
+		Object.defineProperties(result, {
+			html: {
+				get: () => {
+					return (sync ??= Payload.#render(component, options)).body;
+				}
+			},
+			head: {
+				get: () => {
+					return (sync ??= Payload.#render(component, options)).head;
+				}
+			},
+			body: {
+				get: () => {
+					return (sync ??= Payload.#render(component, options)).body;
+				}
+			},
+			then: {
+				value:
+					/**
+					 * this is not type-safe, but honestly it's the best I can do right now, and it's a straightforward function.
+					 *
+					 * @template TResult1
+					 * @template [TResult2=never]
+					 * @param { (value: SyncRenderOutput) => TResult1 } onfulfilled
+					 * @param { (reason: unknown) => TResult2 } onrejected
+					 */
+					(onfulfilled, onrejected) => {
+						if (!async_mode_flag) {
+							w.experimental_async_ssr();
+							const result = (sync ??= Payload.#render(component, options));
+							const user_result = onfulfilled({
+								head: result.head,
+								body: result.body,
+								html: result.body
+							});
+							return Promise.resolve(user_result);
+						}
+						async ??= Payload.#render_async(component, options);
+						return async.then((result) => {
+							Object.defineProperty(result, 'html', {
+								// eslint-disable-next-line getter-return
+								get: () => {
+									e.html_deprecated();
+								}
+							});
+							return onfulfilled(/** @type {SyncRenderOutput} */ (result));
+						}, onrejected);
+					}
+			}
+		});
+
+		return result;
+	}
+
+	/**
+	 * Collect all of the `onDestroy` callbacks regsitered during rendering. In an async context, this is only safe to call
+	 * after awaiting `collect_async`.
+	 *
+	 * Child payloads are "porous" and don't affect execution order, but component body payloads
+	 * create ordering boundaries. Within a payload, callbacks run in order until hitting a component boundary.
+	 * @returns {Iterable<() => void>}
+	 */
+	*#collect_on_destroy() {
+		for (const component of this.#traverse_components()) {
+			yield* component.#collect_ondestroy();
+		}
+	}
+
+	/**
+	 * Performs a depth-first search of payloads, yielding the deepest components first, then additional components as we backtrack up the tree.
+	 * @returns {Iterable<Payload>}
+	 */
+	*#traverse_components() {
+		for (const child of this.#out) {
+			if (typeof child !== 'string') {
+				yield* child.#traverse_components();
+			}
+		}
+		if (this.#is_component_body) {
+			yield this;
+		}
+	}
+
+	/**
+	 * @returns {Iterable<() => void>}
+	 */
+	*#collect_ondestroy() {
+		if (this.#on_destroy) {
+			for (const fn of this.#on_destroy) {
+				yield fn;
+			}
+		}
+		for (const child of this.#out) {
+			if (child instanceof Payload && !child.#is_component_body) {
+				yield* child.#collect_ondestroy();
+			}
+		}
+	}
+
+	/**
+	 * Render a component. Throws if any of the children are performing asynchronous work.
+	 *
+	 * @template {Record<string, any>} Props
+	 * @param {Component<Props>} component
+	 * @param {{ props?: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any>; idPrefix?: string }} options
+	 * @returns {AccumulatedContent}
+	 */
+	static #render(component, options) {
+		var previous_context = ssr_context;
+		try {
+			const payload = Payload.#open_render('sync', component, options);
+
+			const content = Payload.#collect_content([payload], payload.type);
+			return Payload.#close_render(content, payload);
+		} finally {
+			abort();
+			set_ssr_context(previous_context);
+		}
+	}
+
+	/**
+	 * Render a component.
+	 *
+	 * @template {Record<string, any>} Props
+	 * @param {Component<Props>} component
+	 * @param {{ props?: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any>; idPrefix?: string }} options
+	 * @returns {Promise<AccumulatedContent>}
+	 */
+	static async #render_async(component, options) {
+		var previous_context = ssr_context;
+		try {
+			const payload = Payload.#open_render('async', component, options);
+
+			const content = await Payload.#collect_content_async([payload], payload.type);
+			return Payload.#close_render(content, payload);
+		} finally {
+			abort();
+			set_ssr_context(previous_context);
+		}
+	}
+
+	/**
+	 * @param {(content: AccumulatedContent) => AccumulatedContent | Promise<AccumulatedContent>} fn
+	 * @param {Payload} child
+	 * @param {PayloadItem[]} to_compact
+	 * @param {PayloadType} type
+	 */
+	static #compact(fn, child, to_compact, type) {
+		const content = Payload.#collect_content(to_compact, type);
+		const transformed_content = fn(content);
+		if (transformed_content instanceof Promise) {
+			throw new Error(
+				"invariant: Somehow you've encountered asynchronous work while rendering synchronously. If you're seeing this, there's a compiler bug. File an issue!"
+			);
+		} else {
+			Payload.#push_accumulated_content(child, transformed_content);
+		}
+	}
+
+	/**
+	 * @param {(content: AccumulatedContent) => AccumulatedContent | Promise<AccumulatedContent>} fn
+	 * @param {Payload} child
+	 * @param {PayloadItem[]} to_compact
+	 * @param {PayloadType} type
+	 */
+	static async #compact_async(fn, child, to_compact, type) {
+		const content = await Payload.#collect_content_async(to_compact, type);
+		const transformed_content = await fn(content);
+		Payload.#push_accumulated_content(child, transformed_content);
+	}
+
+	/**
+	 * Collect all of the code from the `out` array and return it as a string, or a promise resolving to a string.
+	 * @param {PayloadItem[]} items
+	 * @param {PayloadType} current_type
+	 * @param {AccumulatedContent} content
+	 * @returns {AccumulatedContent}
+	 */
+	static #collect_content(items, current_type, content = { head: '', body: '' }) {
+		for (const item of items) {
+			if (typeof item === 'string') {
+				content[current_type] += item;
+			} else if (item instanceof Payload) {
+				Payload.#collect_content(item.#out, item.type, content);
+			}
+		}
+		return content;
+	}
+
+	/**
+	 * Collect all of the code from the `out` array and return it as a string.
+	 * @param {PayloadItem[]} items
+	 * @param {PayloadType} current_type
+	 * @param {AccumulatedContent} content
+	 * @returns {Promise<AccumulatedContent>}
+	 */
+	static async #collect_content_async(items, current_type, content = { head: '', body: '' }) {
+		// no danger to sequentially awaiting stuff in here; all of the work is already kicked off
+		for (const item of items) {
+			if (typeof item === 'string') {
+				content[current_type] += item;
+			} else {
+				if (item.promises.initial) {
+					// this represents the async function that's modifying this payload.
+					// we can't do anything until it's done and we know our `out` array is complete.
+					await item.promises.initial;
+				}
+				for (const followup of item.promises.followup) {
+					// this is sequential because `compact` could synchronously queue up additional followup work
+					await followup;
+				}
+				await Payload.#collect_content_async(item.#out, item.type, content);
+			}
+		}
+		return content;
+	}
+
+	/**
+	 * @param {Payload} tree
+	 * @param {AccumulatedContent} accumulated_content
+	 */
+	static #push_accumulated_content(tree, accumulated_content) {
+		for (const [type, content] of Object.entries(accumulated_content)) {
+			if (!content) continue;
+			const child = new Payload(tree.global, tree, /** @type {PayloadType} */ (type));
+			child.push(content);
+			tree.#out.push(child);
+		}
+	}
+
+	/**
+	 * @template {Record<string, any>} Props
+	 * @param {'sync' | 'async'} mode
+	 * @param {import('svelte').Component<Props>} component
+	 * @param {{ props?: Omit<Props, '$$slots' | '$$events'>; context?: Map<any, any>; idPrefix?: string }} options
+	 * @returns {Payload}
+	 */
+	static #open_render(mode, component, options) {
+		const payload = new Payload(new SSRState(mode, options.idPrefix ? options.idPrefix + '-' : ''));
+
+		payload.push(BLOCK_OPEN);
+
+		if (options.context) {
+			push();
+			/** @type {SSRContext} */ (ssr_context).c = options.context;
+			/** @type {SSRContext} */ (ssr_context).r = payload;
+		}
+
+		// @ts-expect-error
+		component(payload, options.props ?? {});
+
+		if (options.context) {
+			pop();
+		}
+
+		payload.push(BLOCK_CLOSE);
+
+		return payload;
+	}
+
+	/**
+	 * @param {AccumulatedContent} content
+	 * @param {Payload} payload
+	 */
+	static #close_render(content, payload) {
+		for (const cleanup of payload.#collect_on_destroy()) {
+			cleanup();
+		}
+
+		let head = content.head + payload.global.get_title();
+
+		const body = BLOCK_OPEN + content.body + BLOCK_CLOSE; // this inserts a fake boundary so hydration matches
+
+		for (const { hash, code } of payload.global.css) {
+			head += `<style id="${hash}">${code}</style>`;
+		}
+
+		return {
+			head,
+			body
+		};
 	}
 }
 
-export class Payload {
-	/** @type {Set<{ hash: string; code: string }>} */
+export class SSRState {
+	/** @readonly @type {'sync' | 'async'} */
+	mode;
+
+	/** @readonly @type {() => string} */
+	uid;
+
+	/** @readonly @type {Set<{ hash: string; code: string }>} */
 	css = new Set();
-	/** @type {string[]} */
-	out = [];
-	uid = () => '';
-	select_value = undefined;
 
-	head = new HeadPayload();
+	/** @type {{ path: number[], value: string }} */
+	#title = { path: [], value: '' };
 
-	constructor(id_prefix = '') {
-		this.uid = props_id_generator(id_prefix);
-		this.head.uid = this.uid;
+	/**
+	 * @param {'sync' | 'async'} mode
+	 * @param {string} [id_prefix]
+	 */
+	constructor(mode, id_prefix = '') {
+		this.mode = mode;
+
+		let uid = 1;
+		this.uid = () => `${id_prefix}s${uid++}`;
 	}
-}
 
-/**
- * Used in legacy mode to handle bindings
- * @param {Payload} to_copy
- * @returns {Payload}
- */
-export function copy_payload({ out, css, head, uid }) {
-	const payload = new Payload();
+	get_title() {
+		return this.#title.value;
+	}
 
-	payload.out = [...out];
-	payload.css = new Set(css);
-	payload.uid = uid;
+	/**
+	 * Performs a depth-first (lexicographic) comparison using the path. Rejects sets
+	 * from earlier than or equal to the current value.
+	 * @param {string} value
+	 * @param {number[]} path
+	 */
+	set_title(value, path) {
+		const current = this.#title.path;
 
-	payload.head = new HeadPayload();
-	payload.head.out = [...head.out];
-	payload.head.css = new Set(head.css);
-	payload.head.title = head.title;
-	payload.head.uid = head.uid;
+		let i = 0;
+		let l = Math.min(path.length, current.length);
 
-	return payload;
-}
+		// skip identical prefixes - [1, 2, 3, ...] === [1, 2, 3, ...]
+		while (i < l && path[i] === current[i]) i += 1;
 
-/**
- * Assigns second payload to first
- * @param {Payload} p1
- * @param {Payload} p2
- * @returns {void}
- */
-export function assign_payload(p1, p2) {
-	p1.out = [...p2.out];
-	p1.css = p2.css;
-	p1.head = p2.head;
-	p1.uid = p2.uid;
-}
+		if (path[i] === undefined) return;
 
-/**
- * Creates an ID generator
- * @param {string} prefix
- * @returns {() => string}
- */
-function props_id_generator(prefix) {
-	let uid = 1;
-	return () => `${prefix}s${uid++}`;
+		// replace title if
+		// - incoming path is longer - [7, 8, 9] > [7, 8]
+		// - incoming path is later  - [7, 8, 9] > [7, 8, 8]
+		if (current[i] === undefined || path[i] > current[i]) {
+			this.#title.path = path;
+			this.#title.value = value;
+		}
+	}
 }
diff --git a/packages/svelte/src/internal/server/payload.test.ts b/packages/svelte/src/internal/server/payload.test.ts
new file mode 100644
index 0000000000..9bf1028817
--- /dev/null
+++ b/packages/svelte/src/internal/server/payload.test.ts
@@ -0,0 +1,364 @@
+import { afterAll, beforeAll, describe, expect, test } from 'vitest';
+import { Payload, SSRState } from './payload.js';
+import type { Component } from 'svelte';
+import { disable_async_mode_flag, enable_async_mode_flag } from '../flags/index.js';
+
+test('collects synchronous body content by default', () => {
+	const component = (payload: Payload) => {
+		payload.push('a');
+		payload.child(($$payload) => {
+			$$payload.push('b');
+		});
+		payload.push('c');
+	};
+
+	const { head, body } = Payload.render(component as unknown as Component);
+	expect(head).toBe('');
+	expect(body).toBe('<!--[--><!--[-->abc<!--]--><!--]-->');
+});
+
+test('child type switches content area (head vs body)', () => {
+	const component = (payload: Payload) => {
+		payload.push('a');
+		payload.child(($$payload) => {
+			$$payload.push('<title>T</title>');
+		}, 'head');
+		payload.push('b');
+	};
+
+	const { head, body } = Payload.render(component as unknown as Component);
+	expect(head).toBe('<title>T</title>');
+	expect(body).toBe('<!--[--><!--[-->ab<!--]--><!--]-->');
+});
+
+test('child inherits parent type when not specified', () => {
+	const component = (payload: Payload) => {
+		payload.child((payload) => {
+			payload.push('<meta name="x"/>');
+			payload.child((payload) => {
+				payload.push('<style>/* css */</style>');
+			});
+		}, 'head');
+	};
+
+	const { head, body } = Payload.render(component as unknown as Component);
+	expect(body).toBe('<!--[--><!--[--><!--]--><!--]-->');
+	expect(head).toBe('<meta name="x"/><style>/* css */</style>');
+});
+
+test('get_path returns the path indexes to a payload', () => {
+	const root = new Payload(new SSRState('sync'));
+	let child_a: InstanceType<typeof Payload> | undefined;
+	let child_b: InstanceType<typeof Payload> | undefined;
+	let child_b_0: InstanceType<typeof Payload> | undefined;
+
+	root.child(($$payload) => {
+		child_a = $$payload;
+		$$payload.push('A');
+	});
+	root.child(($$payload) => {
+		child_b = $$payload;
+		$$payload.child(($$inner) => {
+			child_b_0 = $$inner;
+			$$inner.push('B0');
+		});
+		$$payload.push('B1');
+	});
+
+	expect(child_a!.get_path()).toEqual([0]);
+	expect(child_b!.get_path()).toEqual([1]);
+	expect(child_b_0!.get_path()).toEqual([1, 0]);
+});
+
+test('creating an async child in a sync context throws', () => {
+	const component = (payload: Payload) => {
+		payload.push('a');
+		payload.child(async ($$payload) => {
+			await Promise.resolve();
+			$$payload.push('x');
+		});
+	};
+
+	expect(() => Payload.render(component as unknown as Component).head).toThrow('await_invalid');
+	expect(() => Payload.render(component as unknown as Component).html).toThrow('await_invalid');
+	expect(() => Payload.render(component as unknown as Component).body).toThrow('await_invalid');
+});
+
+test('compact synchronously aggregates a range and can transform into head/body', () => {
+	const component = (payload: Payload) => {
+		const start = payload.length;
+		payload.push('a');
+		payload.push('b');
+		payload.push('c');
+		payload.compact({
+			start,
+			end: start + 2,
+			fn: (content) => {
+				return { head: '<h>H</h>', body: content.body + 'd' };
+			}
+		});
+	};
+
+	const { head, body } = Payload.render(component as unknown as Component);
+	expect(head).toBe('<h>H</h>');
+	expect(body).toBe('<!--[--><!--[-->abdc<!--]--><!--]-->');
+});
+
+test('local state is shallow-copied to children', () => {
+	const root = new Payload(new SSRState('sync'));
+	root.local.select_value = 'A';
+	let child: InstanceType<typeof Payload> | undefined;
+	root.child(($$payload) => {
+		child = $$payload;
+	});
+
+	expect(child!.local.select_value).toBe('A');
+	child!.local.select_value = 'B';
+	expect(root.local.select_value).toBe('A');
+});
+
+test('subsume replaces tree content and state from other', () => {
+	const a = new Payload(new SSRState('async'), undefined, 'head');
+	a.push('<meta />');
+	a.local.select_value = 'A';
+
+	const b = new Payload(new SSRState('async'));
+	b.child(async ($$payload) => {
+		await Promise.resolve();
+		$$payload.push('body');
+	});
+	b.global.css.add({ hash: 'h', code: 'c' });
+	b.global.set_title('Title', [1]);
+	b.local.select_value = 'B';
+	b.promises.initial = Promise.resolve();
+
+	a.subsume(b);
+
+	expect(a.type).toBe('body');
+	expect(a.local.select_value).toBe('B');
+	expect(a.promises).toBe(b.promises);
+});
+
+test('subsume refuses to switch modes', () => {
+	const a = new Payload(new SSRState('sync'), undefined, 'head');
+	a.push('<meta />');
+	a.local.select_value = 'A';
+
+	const b = new Payload(new SSRState('async'));
+	b.child(async ($$payload) => {
+		await Promise.resolve();
+		$$payload.push('body');
+	});
+	b.global.css.add({ hash: 'h', code: 'c' });
+	b.global.set_title('Title', [1]);
+	b.local.select_value = 'B';
+	b.promises.initial = Promise.resolve();
+
+	expect(() => a.subsume(b)).toThrow(
+		"invariant: A payload cannot switch modes. If you're seeing this, there's a compiler bug. File an issue!"
+	);
+});
+
+test('SSRState uid generator uses prefix', () => {
+	const state = new SSRState('sync', 'id-');
+	expect(state.uid()).toBe('id-s1');
+});
+
+test('SSRState title ordering favors later lexicographic paths', () => {
+	const state = new SSRState('sync');
+
+	state.set_title('A', [1]);
+	expect(state.get_title()).toBe('A');
+
+	// equal path -> unchanged
+	state.set_title('B', [1]);
+	expect(state.get_title()).toBe('A');
+
+	// earlier -> unchanged
+	state.set_title('C', [0, 9]);
+	expect(state.get_title()).toBe('A');
+
+	// later -> update
+	state.set_title('D', [2]);
+	expect(state.get_title()).toBe('D');
+
+	// longer but same prefix -> update
+	state.set_title('E', [2, 0]);
+	expect(state.get_title()).toBe('E');
+
+	// shorter (earlier) than current with same prefix -> unchanged
+	state.set_title('F', [2]);
+	expect(state.get_title()).toBe('E');
+});
+
+describe('async', () => {
+	beforeAll(() => {
+		enable_async_mode_flag();
+	});
+
+	afterAll(() => {
+		disable_async_mode_flag();
+	});
+
+	test('awaiting payload gets async content', async () => {
+		const component = (payload: Payload) => {
+			payload.push('1');
+			payload.child(async ($$payload) => {
+				await Promise.resolve();
+				$$payload.push('2');
+			});
+			payload.push('3');
+		};
+
+		const result = await Payload.render(component as unknown as Component);
+		expect(result.head).toBe('');
+		expect(result.body).toBe('<!--[--><!--[-->123<!--]--><!--]-->');
+		expect(() => result.html).toThrow('html_deprecated');
+	});
+
+	test('compact schedules followup when compaction input is async', async () => {
+		const component = (payload: Payload) => {
+			payload.push('a');
+			payload.child(async ($$payload) => {
+				await Promise.resolve();
+				$$payload.push('X');
+			});
+			payload.push('b');
+			payload.compact({
+				start: 0,
+				fn: async (content) => ({
+					body: content.body.toLowerCase(),
+					head: await Promise.resolve('')
+				})
+			});
+		};
+
+		const { body, head } = await Payload.render(component as unknown as Component);
+		expect(head).toBe('');
+		expect(body).toBe('<!--[--><!--[-->axb<!--]--><!--]-->');
+	});
+
+	test('push accepts async functions in async context', async () => {
+		const component = (payload: Payload) => {
+			payload.push('a');
+			payload.push(async () => {
+				await Promise.resolve();
+				return 'b';
+			});
+			payload.push('c');
+		};
+
+		const { head, body } = await Payload.render(component as unknown as Component);
+		expect(head).toBe('');
+		expect(body).toBe('<!--[--><!--[-->abc<!--]--><!--]-->');
+	});
+
+	test('push handles async functions with different timing', async () => {
+		const component = (payload: Payload) => {
+			payload.push(async () => {
+				await Promise.resolve();
+				return 'fast';
+			});
+			payload.push(async () => {
+				await new Promise((resolve) => setTimeout(resolve, 10));
+				return 'slow';
+			});
+			payload.push('sync');
+		};
+
+		const { head, body } = await Payload.render(component as unknown as Component);
+		expect(head).toBe('');
+		expect(body).toBe('<!--[--><!--[-->fastslowsync<!--]--><!--]-->');
+	});
+
+	test('push async functions work with head content type', async () => {
+		const component = (payload: Payload) => {
+			payload.child(($$payload) => {
+				$$payload.push(async () => {
+					await Promise.resolve();
+					return '<title>Async Title</title>';
+				});
+			}, 'head');
+		};
+
+		const { head, body } = await Payload.render(component as unknown as Component);
+		expect(body).toBe('<!--[--><!--[--><!--]--><!--]-->');
+		expect(head).toBe('<title>Async Title</title>');
+	});
+
+	test('push async functions can be mixed with child payloads', async () => {
+		const component = (payload: Payload) => {
+			payload.push('start-');
+			payload.push(async () => {
+				await Promise.resolve();
+				return 'async-';
+			});
+			payload.child(($$payload) => {
+				$$payload.push('child-');
+			});
+			payload.push('-end');
+		};
+
+		const { head, body } = await Payload.render(component as unknown as Component);
+		expect(head).toBe('');
+		expect(body).toBe('<!--[--><!--[-->start-async-child--end<!--]--><!--]-->');
+	});
+
+	test('push async functions work with compact operations', async () => {
+		const component = (payload: Payload) => {
+			payload.push('a');
+			payload.push(async () => {
+				await Promise.resolve();
+				return 'b';
+			});
+			payload.push('c');
+			payload.compact({
+				start: 0,
+				fn: (content) => ({ head: '', body: content.body.toUpperCase() })
+			});
+		};
+
+		const { head, body } = await Payload.render(component as unknown as Component);
+		expect(head).toBe('');
+		expect(body).toBe('<!--[--><!--[-->ABC<!--]--><!--]-->');
+	});
+
+	test('push async functions are not supported in sync context', () => {
+		const component = (payload: Payload) => {
+			payload.push('a');
+			payload.push(() => Promise.resolve('b'));
+		};
+
+		expect(() => Payload.render(component as unknown as Component).body).toThrow('await_invalid');
+		expect(() => Payload.render(component as unknown as Component).html).toThrow('await_invalid');
+		expect(() => Payload.render(component as unknown as Component).head).toThrow('await_invalid');
+	});
+
+	test('on_destroy yields callbacks in the correct order', async () => {
+		const destroyed: string[] = [];
+		const component = (payload: Payload) => {
+			payload.component((payload) => {
+				payload.on_destroy(() => destroyed.push('a'));
+				// children should not alter relative order
+				payload.child(async (payload) => {
+					await Promise.resolve();
+					payload.on_destroy(() => destroyed.push('b'));
+					payload.on_destroy(() => destroyed.push('b*'));
+				});
+				// but child components should
+				payload.component((payload) => {
+					payload.on_destroy(() => destroyed.push('c'));
+				});
+				payload.child((payload) => {
+					payload.on_destroy(() => destroyed.push('d'));
+				});
+				payload.component((payload) => {
+					payload.on_destroy(() => destroyed.push('e'));
+				});
+			});
+		};
+
+		await Payload.render(component as unknown as Component);
+		expect(destroyed).toEqual(['c', 'e', 'a', 'b', 'b*', 'd']);
+	});
+});
diff --git a/packages/svelte/src/internal/server/types.d.ts b/packages/svelte/src/internal/server/types.d.ts
index 6b0fc146c4..be27ea7bd3 100644
--- a/packages/svelte/src/internal/server/types.d.ts
+++ b/packages/svelte/src/internal/server/types.d.ts
@@ -1,17 +1,20 @@
-export interface Component {
+import type { Element } from './dev';
+import type { Payload } from './payload';
+
+export interface SSRContext {
 	/** parent */
-	p: null | Component;
-	/** context */
+	p: null | SSRContext;
+	/** component context */
 	c: null | Map<unknown, unknown>;
-	/** ondestroy */
-	d: null | Array<() => void>;
-	/**
-	 * dev mode only: the component function
-	 */
+	/** payload (renderer) */
+	r: null | Payload;
+	/** dev mode only: the current component function */
 	function?: any;
+	/** dev mode only: the current element */
+	element?: Element;
 }
 
-export interface RenderOutput {
+export interface SyncRenderOutput {
 	/** HTML that goes into the `<head>` */
 	head: string;
 	/** @deprecated use `body` instead */
@@ -19,3 +22,5 @@ export interface RenderOutput {
 	/** HTML that goes somewhere into the `<body>` */
 	body: string;
 }
+
+export type RenderOutput = SyncRenderOutput & PromiseLike<SyncRenderOutput>;
diff --git a/packages/svelte/src/internal/server/warnings.js b/packages/svelte/src/internal/server/warnings.js
new file mode 100644
index 0000000000..d8d9cd6d43
--- /dev/null
+++ b/packages/svelte/src/internal/server/warnings.js
@@ -0,0 +1,17 @@
+/* This file is generated by scripts/process-messages/index.js. Do not edit! */
+
+import { DEV } from 'esm-env';
+
+var bold = 'font-weight: bold';
+var normal = 'font-weight: normal';
+
+/**
+ * Attempted to use asynchronous rendering without `experimental.async` enabled
+ */
+export function experimental_async_ssr() {
+	if (DEV) {
+		console.warn(`%c[svelte] experimental_async_ssr\n%cAttempted to use asynchronous rendering without \`experimental.async\` enabled\nhttps://svelte.dev/e/experimental_async_ssr`, bold, normal);
+	} else {
+		console.warn(`https://svelte.dev/e/experimental_async_ssr`);
+	}
+}
\ No newline at end of file
diff --git a/packages/svelte/src/internal/shared/errors.js b/packages/svelte/src/internal/shared/errors.js
index 66685cb00b..6bcc35016a 100644
--- a/packages/svelte/src/internal/shared/errors.js
+++ b/packages/svelte/src/internal/shared/errors.js
@@ -2,22 +2,6 @@
 
 import { DEV } from 'esm-env';
 
-/**
- * Cannot await outside a `<svelte:boundary>` with a `pending` snippet
- * @returns {never}
- */
-export function await_outside_boundary() {
-	if (DEV) {
-		const error = new Error(`await_outside_boundary\nCannot await outside a \`<svelte:boundary>\` with a \`pending\` snippet\nhttps://svelte.dev/e/await_outside_boundary`);
-
-		error.name = 'Svelte error';
-
-		throw error;
-	} else {
-		throw new Error(`https://svelte.dev/e/await_outside_boundary`);
-	}
-}
-
 /**
  * Cannot use `{@render children(...)}` if the parent component uses `let:` directives. Consider using a named snippet instead
  * @returns {never}
diff --git a/packages/svelte/src/legacy/legacy-server.js b/packages/svelte/src/legacy/legacy-server.js
index 60bd8c9fc6..92f8757d7a 100644
--- a/packages/svelte/src/legacy/legacy-server.js
+++ b/packages/svelte/src/legacy/legacy-server.js
@@ -31,6 +31,7 @@ export function asClassComponent(component) {
 			html: result.body
 		};
 	};
+
 	// @ts-expect-error this is present for SSR
 	component_constructor.render = _render;
 
diff --git a/packages/svelte/tests/hydration/samples/binding-input/_expected.html b/packages/svelte/tests/hydration/samples/binding-input/_expected.html
index e36735dc6b..7a73053b82 100644
--- a/packages/svelte/tests/hydration/samples/binding-input/_expected.html
+++ b/packages/svelte/tests/hydration/samples/binding-input/_expected.html
@@ -1 +1 @@
-<!--[--><input> <p>Hello world!</p><!--]-->
+<!--[--><!--[--><input> <p>Hello world!</p><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/cloudflare-mirage-borking-2/_override.html b/packages/svelte/tests/hydration/samples/cloudflare-mirage-borking-2/_override.html
index 2a1c323288..117d83d8eb 100644
--- a/packages/svelte/tests/hydration/samples/cloudflare-mirage-borking-2/_override.html
+++ b/packages/svelte/tests/hydration/samples/cloudflare-mirage-borking-2/_override.html
@@ -1 +1 @@
-<!--[--> <p>start</p><!--[--><p>cond</p><!--]--><!--]-->
+<!--[--><!--[--> <p>start</p><!--[--><p>cond</p><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/dynamic-text-changed/_expected.html b/packages/svelte/tests/hydration/samples/dynamic-text-changed/_expected.html
index 11e3f55d6b..04266bf7f3 100644
--- a/packages/svelte/tests/hydration/samples/dynamic-text-changed/_expected.html
+++ b/packages/svelte/tests/hydration/samples/dynamic-text-changed/_expected.html
@@ -1 +1 @@
-<!--[--><h1>Hello everybody!</h1><!--]-->
+<!--[--><!--[--><h1>Hello everybody!</h1><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/each-block-0-on-server-more-on-client/_expected.html b/packages/svelte/tests/hydration/samples/each-block-0-on-server-more-on-client/_expected.html
index 2b2a31b926..4b28b305d5 100644
--- a/packages/svelte/tests/hydration/samples/each-block-0-on-server-more-on-client/_expected.html
+++ b/packages/svelte/tests/hydration/samples/each-block-0-on-server-more-on-client/_expected.html
@@ -1 +1 @@
-<!--[--><ul><!--[--><li>a</li><!--]--></ul> <ul><!--[--><li>a</li><!--]--></ul> <ul><!--[--><li>a</li><!--]--></ul> <!--[--><li>a</li> <li>a</li><!--]--> <!--[--><li>a</li> <li>a</li><!--]--> <!--[--><li>a</li> <li>a</li><!--]--><!--]-->
+<!--[--><!--[--><ul><!--[--><li>a</li><!--]--></ul> <ul><!--[--><li>a</li><!--]--></ul> <ul><!--[--><li>a</li><!--]--></ul> <!--[--><li>a</li> <li>a</li><!--]--> <!--[--><li>a</li> <li>a</li><!--]--> <!--[--><li>a</li> <li>a</li><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/each-block-fallback-mismatch/_expected.html b/packages/svelte/tests/hydration/samples/each-block-fallback-mismatch/_expected.html
index af66d98b25..8ace6d0373 100644
--- a/packages/svelte/tests/hydration/samples/each-block-fallback-mismatch/_expected.html
+++ b/packages/svelte/tests/hydration/samples/each-block-fallback-mismatch/_expected.html
@@ -1 +1 @@
-<!--[--><!--[!--><p>a</p><!--]--> <!--[--><p>empty</p><!--]--><!--]-->
+<!--[--><!--[--><!--[!--><p>a</p><!--]--> <!--[--><p>empty</p><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/each-block-less-nodes-on-client/_expected.html b/packages/svelte/tests/hydration/samples/each-block-less-nodes-on-client/_expected.html
index 2b2a31b926..4b28b305d5 100644
--- a/packages/svelte/tests/hydration/samples/each-block-less-nodes-on-client/_expected.html
+++ b/packages/svelte/tests/hydration/samples/each-block-less-nodes-on-client/_expected.html
@@ -1 +1 @@
-<!--[--><ul><!--[--><li>a</li><!--]--></ul> <ul><!--[--><li>a</li><!--]--></ul> <ul><!--[--><li>a</li><!--]--></ul> <!--[--><li>a</li> <li>a</li><!--]--> <!--[--><li>a</li> <li>a</li><!--]--> <!--[--><li>a</li> <li>a</li><!--]--><!--]-->
+<!--[--><!--[--><ul><!--[--><li>a</li><!--]--></ul> <ul><!--[--><li>a</li><!--]--></ul> <ul><!--[--><li>a</li><!--]--></ul> <!--[--><li>a</li> <li>a</li><!--]--> <!--[--><li>a</li> <li>a</li><!--]--> <!--[--><li>a</li> <li>a</li><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/each-block-more-nodes-on-client/_expected.html b/packages/svelte/tests/hydration/samples/each-block-more-nodes-on-client/_expected.html
index fa72a80dcd..89cbd0b466 100644
--- a/packages/svelte/tests/hydration/samples/each-block-more-nodes-on-client/_expected.html
+++ b/packages/svelte/tests/hydration/samples/each-block-more-nodes-on-client/_expected.html
@@ -1 +1 @@
-<!--[--><ul><!--[--><li>a</li><li>b</li><!--]--></ul> <ul><!--[--><li>a</li><li>b</li><!--]--></ul> <ul><!--[--><li>a</li><li>b</li><!--]--></ul> <!--[--><li>a</li> <li>a</li><li>b</li> <li>b</li><!--]--> <!--[--><li>a</li> <li>a</li><li>b</li> <li>b</li><!--]--> <!--[--><li>a</li> <li>a</li><li>b</li> <li>b</li><!--]--><!--]-->
+<!--[--><!--[--><ul><!--[--><li>a</li><li>b</li><!--]--></ul> <ul><!--[--><li>a</li><li>b</li><!--]--></ul> <ul><!--[--><li>a</li><li>b</li><!--]--></ul> <!--[--><li>a</li> <li>a</li><li>b</li> <li>b</li><!--]--> <!--[--><li>a</li> <li>a</li><li>b</li> <li>b</li><!--]--> <!--[--><li>a</li> <li>a</li><li>b</li> <li>b</li><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/element-attribute-added/_expected.html b/packages/svelte/tests/hydration/samples/element-attribute-added/_expected.html
index 7d8e91c757..27f9299c54 100644
--- a/packages/svelte/tests/hydration/samples/element-attribute-added/_expected.html
+++ b/packages/svelte/tests/hydration/samples/element-attribute-added/_expected.html
@@ -1 +1 @@
-<!--[--><div class="bar"></div><!--]-->
+<!--[--><!--[--><div class="bar"></div><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/element-attribute-changed/_expected.html b/packages/svelte/tests/hydration/samples/element-attribute-changed/_expected.html
index 7d8e91c757..27f9299c54 100644
--- a/packages/svelte/tests/hydration/samples/element-attribute-changed/_expected.html
+++ b/packages/svelte/tests/hydration/samples/element-attribute-changed/_expected.html
@@ -1 +1 @@
-<!--[--><div class="bar"></div><!--]-->
+<!--[--><!--[--><div class="bar"></div><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/element-attribute-removed/_expected.html b/packages/svelte/tests/hydration/samples/element-attribute-removed/_expected.html
index a6c1be8b49..1a69c9fa30 100644
--- a/packages/svelte/tests/hydration/samples/element-attribute-removed/_expected.html
+++ b/packages/svelte/tests/hydration/samples/element-attribute-removed/_expected.html
@@ -1 +1 @@
-<!--[--><div></div> <!--[--><div></div> <div></div><!--]--><!--]-->
+<!--[--><!--[--><div></div> <!--[--><div></div> <div></div><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/if-block-mismatch-2/_expected.html b/packages/svelte/tests/hydration/samples/if-block-mismatch-2/_expected.html
index 08a3809de9..5620250623 100644
--- a/packages/svelte/tests/hydration/samples/if-block-mismatch-2/_expected.html
+++ b/packages/svelte/tests/hydration/samples/if-block-mismatch-2/_expected.html
@@ -1 +1 @@
-<!--[--><!--[--><!--]--> <div><!----><!----></div> hello<!--]-->
+<!--[--><!--[--><!--[--><!--]--> <div><!----><!----></div> hello<!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/if-block-mismatch/_expected.html b/packages/svelte/tests/hydration/samples/if-block-mismatch/_expected.html
index 79cf2cf35f..5ace45d895 100644
--- a/packages/svelte/tests/hydration/samples/if-block-mismatch/_expected.html
+++ b/packages/svelte/tests/hydration/samples/if-block-mismatch/_expected.html
@@ -1 +1 @@
-<!--[--><!--[!--><p>foo</p><!--]--><!--]-->
+<!--[--><!--[--><!--[!--><p>foo</p><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/input-checked-attribute-sibling/_expected.html b/packages/svelte/tests/hydration/samples/input-checked-attribute-sibling/_expected.html
index bcd53f8783..521f9c52b8 100644
--- a/packages/svelte/tests/hydration/samples/input-checked-attribute-sibling/_expected.html
+++ b/packages/svelte/tests/hydration/samples/input-checked-attribute-sibling/_expected.html
@@ -1 +1 @@
-<!--[--><!---->.<input><!--]-->
+<!--[--><!--[--><!---->.<input><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/input-value-changed/_expected.html b/packages/svelte/tests/hydration/samples/input-value-changed/_expected.html
index c5384e717e..c9bc1409d7 100644
--- a/packages/svelte/tests/hydration/samples/input-value-changed/_expected.html
+++ b/packages/svelte/tests/hydration/samples/input-value-changed/_expected.html
@@ -1 +1 @@
-<!--[--><input type="text"><!--]-->
+<!--[--><!--[--><input type="text"><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/noscript/_expected.html b/packages/svelte/tests/hydration/samples/noscript/_expected.html
index 990ce87303..a587a13af1 100644
--- a/packages/svelte/tests/hydration/samples/noscript/_expected.html
+++ b/packages/svelte/tests/hydration/samples/noscript/_expected.html
@@ -1 +1 @@
-<!--[--><noscript>JavaScript is required for this site.</noscript> <h1>Hello!</h1><p>Count: 1</p><!--]-->
+<!--[--><!--[--><noscript>JavaScript is required for this site.</noscript> <h1>Hello!</h1><p>Count: 1</p><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/pre-first-node-newline/_expected.html b/packages/svelte/tests/hydration/samples/pre-first-node-newline/_expected.html
index 26de34d1ed..a4d2df2147 100644
--- a/packages/svelte/tests/hydration/samples/pre-first-node-newline/_expected.html
+++ b/packages/svelte/tests/hydration/samples/pre-first-node-newline/_expected.html
@@ -1,7 +1,7 @@
-<!--[--><pre>static content no line</pre> <pre>	static content ignored line
+<!--[--><!--[--><pre>static content no line</pre> <pre>	static content ignored line
 </pre> <pre>
 	static content relevant line
 </pre> <pre><div><span></span></div>
 </pre> <pre>
 <div><span></span></div>
-</pre><!--]-->
+</pre><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/removes-undefined-attributes/_expected.html b/packages/svelte/tests/hydration/samples/removes-undefined-attributes/_expected.html
index cc789c8f51..4af6885faf 100644
--- a/packages/svelte/tests/hydration/samples/removes-undefined-attributes/_expected.html
+++ b/packages/svelte/tests/hydration/samples/removes-undefined-attributes/_expected.html
@@ -1 +1 @@
-<!--[--><div></div><!--]-->
+<!--[--><!--[--><div></div><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/repair-mismatched-a-href/_expected.html b/packages/svelte/tests/hydration/samples/repair-mismatched-a-href/_expected.html
index e1076af2ec..1755e9bfe2 100644
--- a/packages/svelte/tests/hydration/samples/repair-mismatched-a-href/_expected.html
+++ b/packages/svelte/tests/hydration/samples/repair-mismatched-a-href/_expected.html
@@ -1 +1 @@
-<!--[--><a href="/foo">foo</a> <a href="/foo">foo</a><!--]-->
+<!--[--><!--[--><a href="/foo">foo</a> <a href="/foo">foo</a><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/safari-borking/_override.html b/packages/svelte/tests/hydration/samples/safari-borking/_override.html
index 876815e7a9..b3665d1f80 100644
--- a/packages/svelte/tests/hydration/samples/safari-borking/_override.html
+++ b/packages/svelte/tests/hydration/samples/safari-borking/_override.html
@@ -1 +1 @@
-<!--[--><h1>call <a href="tel:+636-555-3226">+636-555-3226</a> now<span>!</span></h1><!--]-->
+<!--[--><!--[--><h1>call <a href="tel:+636-555-3226">+636-555-3226</a> now<span>!</span></h1><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/script/_expected.html b/packages/svelte/tests/hydration/samples/script/_expected.html
index b3a4d92219..ab881a6197 100644
--- a/packages/svelte/tests/hydration/samples/script/_expected.html
+++ b/packages/svelte/tests/hydration/samples/script/_expected.html
@@ -1 +1 @@
-<!--[--><!----><script>{}<!----></script><!----><!--]-->
+<!--[--><!--[--><!----><script>{}<!----></script><!----><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/snippet-raw-hydrate/_expected.html b/packages/svelte/tests/hydration/samples/snippet-raw-hydrate/_expected.html
index 8d9dde52c1..0629ab64c2 100644
--- a/packages/svelte/tests/hydration/samples/snippet-raw-hydrate/_expected.html
+++ b/packages/svelte/tests/hydration/samples/snippet-raw-hydrate/_expected.html
@@ -1 +1 @@
-<!--[--><p>hydrated</p><!--]-->
+<!--[--><!--[--><p>hydrated</p><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/standalone-component/_expected.html b/packages/svelte/tests/hydration/samples/standalone-component/_expected.html
index 96850f7bdf..119576aa73 100644
--- a/packages/svelte/tests/hydration/samples/standalone-component/_expected.html
+++ b/packages/svelte/tests/hydration/samples/standalone-component/_expected.html
@@ -1 +1 @@
-<!--[--><!--[--><p>child</p><!--]--> <!--[--><p>child</p><p>child</p><p>child</p><!--]--><!--]-->
+<!--[--><!--[--><!--[--><p>child</p><!--]--> <!--[--><p>child</p><p>child</p><p>child</p><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/standalone-snippet/_expected.html b/packages/svelte/tests/hydration/samples/standalone-snippet/_expected.html
index acb14818c2..61fc31a95e 100644
--- a/packages/svelte/tests/hydration/samples/standalone-snippet/_expected.html
+++ b/packages/svelte/tests/hydration/samples/standalone-snippet/_expected.html
@@ -1 +1 @@
-<!--[--><!--[--><p>thing</p><!--]--> <!--[--><p>thing</p><p>thing</p><p>thing</p><!--]--><!--]-->
+<!--[--><!--[--><!--[--><p>thing</p><!--]--> <!--[--><p>thing</p><p>thing</p><p>thing</p><!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/surrounding-whitespace/_expected.html b/packages/svelte/tests/hydration/samples/surrounding-whitespace/_expected.html
index e728b682d0..7b51bed662 100644
--- a/packages/svelte/tests/hydration/samples/surrounding-whitespace/_expected.html
+++ b/packages/svelte/tests/hydration/samples/surrounding-whitespace/_expected.html
@@ -1,2 +1,2 @@
 		<!-- unrelated comment -->
-		<!--[--><!--[-->hello<!--]--><!--]-->
+		<!--[--><!--[--><!--[-->hello<!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/surrounding-whitespace/_override.html b/packages/svelte/tests/hydration/samples/surrounding-whitespace/_override.html
index e728b682d0..7b51bed662 100644
--- a/packages/svelte/tests/hydration/samples/surrounding-whitespace/_override.html
+++ b/packages/svelte/tests/hydration/samples/surrounding-whitespace/_override.html
@@ -1,2 +1,2 @@
 		<!-- unrelated comment -->
-		<!--[--><!--[-->hello<!--]--><!--]-->
+		<!--[--><!--[--><!--[-->hello<!--]--><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/text-empty-2/_expected.html b/packages/svelte/tests/hydration/samples/text-empty-2/_expected.html
index ff12f10bfb..e14014c2f0 100644
--- a/packages/svelte/tests/hydration/samples/text-empty-2/_expected.html
+++ b/packages/svelte/tests/hydration/samples/text-empty-2/_expected.html
@@ -1 +1 @@
-<!--[--><span><span></span></span><!--]-->
+<!--[--><!--[--><span><span></span></span><!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/text-empty/_expected.html b/packages/svelte/tests/hydration/samples/text-empty/_expected.html
index 2e03580f42..c4d823410f 100644
--- a/packages/svelte/tests/hydration/samples/text-empty/_expected.html
+++ b/packages/svelte/tests/hydration/samples/text-empty/_expected.html
@@ -1 +1 @@
-<!--[--><!---->x<!--]-->
+<!--[--><!--[--><!---->x<!--]--><!--]-->
diff --git a/packages/svelte/tests/hydration/samples/whitespace-at-block-start/_override.html b/packages/svelte/tests/hydration/samples/whitespace-at-block-start/_override.html
index 90ca4ef4b8..7402247877 100644
--- a/packages/svelte/tests/hydration/samples/whitespace-at-block-start/_override.html
+++ b/packages/svelte/tests/hydration/samples/whitespace-at-block-start/_override.html
@@ -1,2 +1,2 @@
-<!--[-->
-<main><p>nested</p><!----></main><!--]-->
\ No newline at end of file
+<!--[--><!--[-->
+<main><p>nested</p><!----></main><!--]--><!--]-->
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-browser/driver-ssr.js b/packages/svelte/tests/runtime-browser/driver-ssr.js
index 7067e48a1f..35aaca3ad3 100644
--- a/packages/svelte/tests/runtime-browser/driver-ssr.js
+++ b/packages/svelte/tests/runtime-browser/driver-ssr.js
@@ -6,5 +6,9 @@ import config from '__CONFIG__';
 import { render } from 'svelte/server';
 
 export default function () {
-	return render(SvelteComponent, { props: config.props || {}, idPrefix: config?.id_prefix });
+	const { head, body, html } = render(SvelteComponent, {
+		props: config.props || {},
+		idPrefix: config?.id_prefix
+	});
+	return { head, body, html };
 }
diff --git a/packages/svelte/tests/runtime-legacy/samples/after-render-prevents-loop/_config.js b/packages/svelte/tests/runtime-legacy/samples/after-render-prevents-loop/_config.js
index 39c0ef7f53..7a0943c3f4 100644
--- a/packages/svelte/tests/runtime-legacy/samples/after-render-prevents-loop/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/after-render-prevents-loop/_config.js
@@ -1,7 +1,7 @@
 import { test } from '../../test';
 
 export default test({
-	skip_mode: ['server'],
+	skip_mode: ['server', 'async-server'],
 
 	get props() {
 		return { value: 'hello!' };
diff --git a/packages/svelte/tests/runtime-legacy/samples/after-render-triggers-update/_config.js b/packages/svelte/tests/runtime-legacy/samples/after-render-triggers-update/_config.js
index 39c0ef7f53..7a0943c3f4 100644
--- a/packages/svelte/tests/runtime-legacy/samples/after-render-triggers-update/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/after-render-triggers-update/_config.js
@@ -1,7 +1,7 @@
 import { test } from '../../test';
 
 export default test({
-	skip_mode: ['server'],
+	skip_mode: ['server', 'async-server'],
 
 	get props() {
 		return { value: 'hello!' };
diff --git a/packages/svelte/tests/runtime-legacy/samples/before-render-prevents-loop/_config.js b/packages/svelte/tests/runtime-legacy/samples/before-render-prevents-loop/_config.js
index 39c0ef7f53..7a0943c3f4 100644
--- a/packages/svelte/tests/runtime-legacy/samples/before-render-prevents-loop/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/before-render-prevents-loop/_config.js
@@ -1,7 +1,7 @@
 import { test } from '../../test';
 
 export default test({
-	skip_mode: ['server'],
+	skip_mode: ['server', 'async-server'],
 
 	get props() {
 		return { value: 'hello!' };
diff --git a/packages/svelte/tests/runtime-legacy/samples/binding-select-implicit-option-value/_config.js b/packages/svelte/tests/runtime-legacy/samples/binding-select-implicit-option-value/_config.js
index dd88c10c71..2b866bc8ce 100644
--- a/packages/svelte/tests/runtime-legacy/samples/binding-select-implicit-option-value/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/binding-select-implicit-option-value/_config.js
@@ -8,9 +8,9 @@ export default test({
 
 	ssrHtml: `
 		<select>
-			<option value="1">1</option>
-			<option selected value="2">2</option>
-			<option value="3">3</option>
+			<option>1</option>
+			<option selected>2</option>
+			<option>3</option>
 		</select>
 
 		<p>foo: 2</p>
@@ -21,9 +21,9 @@ export default test({
 			target.innerHTML,
 			`
 			<select>
-				<option value="1">1</option>
-				<option ${variant === 'hydrate' ? 'selected ' : ''}value="2">2</option>
-				<option value="3">3</option>
+				<option>1</option>
+				<option ${variant === 'hydrate' ? 'selected ' : ''}>2</option>
+				<option>3</option>
 			</select>
 
 			<p>foo: 2</p>
@@ -47,9 +47,9 @@ export default test({
 			target.innerHTML,
 			`
 			<select>
-				<option value="1">1</option>
-				<option ${variant === 'hydrate' ? 'selected ' : ''}value="2">2</option>
-				<option value="3">3</option>
+				<option>1</option>
+				<option ${variant === 'hydrate' ? 'selected ' : ''}>2</option>
+				<option>3</option>
 			</select>
 
 			<p>foo: 3</p>
diff --git a/packages/svelte/tests/runtime-legacy/samples/binding-select-initial-value-undefined-3/_config.js b/packages/svelte/tests/runtime-legacy/samples/binding-select-initial-value-undefined-3/_config.js
index 9b25c0bc58..c48298229e 100644
--- a/packages/svelte/tests/runtime-legacy/samples/binding-select-initial-value-undefined-3/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/binding-select-initial-value-undefined-3/_config.js
@@ -8,9 +8,9 @@ export default test({
 
 		<select>
 			<option disabled=''>x</option>
-			<option value="a">a</option>
-			<option value="b">b</option>
-			<option value="c">c</option>
+			<option>a</option>
+			<option>b</option>
+			<option>c</option>
 		</select>
 	`,
 
diff --git a/packages/svelte/tests/runtime-legacy/samples/binding-select-late-2/_config.js b/packages/svelte/tests/runtime-legacy/samples/binding-select-late-2/_config.js
index ab2db4b07d..72e06190ba 100644
--- a/packages/svelte/tests/runtime-legacy/samples/binding-select-late-2/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/binding-select-late-2/_config.js
@@ -28,9 +28,9 @@ export default test({
 			target.innerHTML,
 			`
 			<select>
-				<option value="one">one</option>
-				<option value="two">two</option>
-				<option value="three">three</option>
+				<option>one</option>
+				<option>two</option>
+				<option>three</option>
 			</select>
 			<p>selected: two</p>
 		`
diff --git a/packages/svelte/tests/runtime-legacy/samples/binding-select-late-3/_config.js b/packages/svelte/tests/runtime-legacy/samples/binding-select-late-3/_config.js
index 234c2a1040..72e06190ba 100644
--- a/packages/svelte/tests/runtime-legacy/samples/binding-select-late-3/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/binding-select-late-3/_config.js
@@ -28,9 +28,9 @@ export default test({
 			target.innerHTML,
 			`
 			<select>
-				<option value='one'>one</option>
-				<option value='two'>two</option>
-				<option value='three'>three</option>
+				<option>one</option>
+				<option>two</option>
+				<option>three</option>
 			</select>
 			<p>selected: two</p>
 		`
diff --git a/packages/svelte/tests/runtime-legacy/samples/binding-select-late/_config.js b/packages/svelte/tests/runtime-legacy/samples/binding-select-late/_config.js
index 9c3cd8765a..6c7662def3 100644
--- a/packages/svelte/tests/runtime-legacy/samples/binding-select-late/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/binding-select-late/_config.js
@@ -28,9 +28,9 @@ export default test({
 			target.innerHTML,
 			`
 			<select>
-				<option value="one">one</option>
-				<option value="two">two</option>
-				<option value="three">three</option>
+				<option>one</option>
+				<option>two</option>
+				<option>three</option>
 			</select>
 			<p>selected: two</p>
 		`
diff --git a/packages/svelte/tests/runtime-legacy/samples/binding-select-unmatched-2/_config.js b/packages/svelte/tests/runtime-legacy/samples/binding-select-unmatched-2/_config.js
index 85d61eeeec..b0bbed9c92 100644
--- a/packages/svelte/tests/runtime-legacy/samples/binding-select-unmatched-2/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/binding-select-unmatched-2/_config.js
@@ -6,9 +6,9 @@ export default test({
 		<p>selected: </p>
 
 		<select>
-			<option value="a">a</option>
-			<option value="b">b</option>
-			<option value="c">c</option>
+			<option>a</option>
+			<option>b</option>
+			<option>c</option>
 		</select>
 
 		<p>selected: </p>
@@ -37,9 +37,9 @@ export default test({
 			<p>selected: a</p>
 
 			<select>
-				<option value="a">a</option>
-				<option value="b">b</option>
-				<option value="c">c</option>
+				<option>a</option>
+				<option>b</option>
+				<option>c</option>
 			</select>
 
 			<p>selected: a</p>
@@ -59,9 +59,9 @@ export default test({
 			<p>selected: d</p>
 
 			<select>
-				<option value="a">a</option>
-				<option value="b">b</option>
-				<option value="c">c</option>
+				<option>a</option>
+				<option>b</option>
+				<option>c</option>
 			</select>
 
 			<p>selected: d</p>
@@ -78,9 +78,9 @@ export default test({
 			<p>selected: b</p>
 
 			<select>
-				<option value="a">a</option>
-				<option value="b">b</option>
-				<option value="c">c</option>
+				<option>a</option>
+				<option>b</option>
+				<option>c</option>
 			</select>
 
 			<p>selected: b</p>
@@ -100,9 +100,9 @@ export default test({
 			<p>selected: </p>
 
 			<select>
-				<option value="a">a</option>
-				<option value="b">b</option>
-				<option value="c">c</option>
+				<option>a</option>
+				<option>b</option>
+				<option>c</option>
 			</select>
 
 			<p>selected: </p>
diff --git a/packages/svelte/tests/runtime-legacy/samples/binding-select-unmatched-3/_config.js b/packages/svelte/tests/runtime-legacy/samples/binding-select-unmatched-3/_config.js
index c0e64521d1..d616d9bc26 100644
--- a/packages/svelte/tests/runtime-legacy/samples/binding-select-unmatched-3/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/binding-select-unmatched-3/_config.js
@@ -4,7 +4,7 @@ import { ok, test } from '../../test';
 export default test({
 	mode: ['client', 'hydrate'],
 
-	html: `<p>selected: a</p><select><option value="a">a</option><option value="b">b</option><option value="c">c</option></select>`,
+	html: `<p>selected: a</p><select><option>a</option><option>b</option><option>c</option></select>`,
 
 	async test({ assert, component, target }) {
 		const select = target.querySelector('select');
@@ -29,7 +29,7 @@ export default test({
 		// model of selected value should be kept around, even if it is not in the list
 		assert.htmlEqual(
 			target.innerHTML,
-			`<p>selected: a</p><select><option value="b">b</option><option value="c">c</option></select>`
+			`<p>selected: a</p><select><option>b</option><option>c</option></select>`
 		);
 	}
 });
diff --git a/packages/svelte/tests/runtime-legacy/samples/constructor-prefer-passed-context/_config.js b/packages/svelte/tests/runtime-legacy/samples/constructor-prefer-passed-context/_config.js
index e05bb35637..7c49960afd 100644
--- a/packages/svelte/tests/runtime-legacy/samples/constructor-prefer-passed-context/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/constructor-prefer-passed-context/_config.js
@@ -1,7 +1,7 @@
 import { test } from '../../test';
 
 export default test({
-	skip_mode: ['server'],
+	skip_mode: ['server', 'async-server'],
 
 	html: `
 		<div><div>Value in child component: </div></div>
diff --git a/packages/svelte/tests/runtime-legacy/samples/textarea-content/_config.js b/packages/svelte/tests/runtime-legacy/samples/textarea-content/_config.js
index 7cd7c553e0..dac6ee4fb8 100644
--- a/packages/svelte/tests/runtime-legacy/samples/textarea-content/_config.js
+++ b/packages/svelte/tests/runtime-legacy/samples/textarea-content/_config.js
@@ -4,7 +4,7 @@ export default test({
 	withoutNormalizeHtml: true,
 	// Unable to test `html` with `<textarea>` content
 	// as the textarea#value will not show within `innerHtml`
-	ssrHtml: `<!--[--><textarea id="textarea">  A
+	ssrHtml: `<!--[--><!--[--><textarea id="textarea">  A
   B
 </textarea> <div id="div-with-textarea"><textarea>    A
     B
@@ -14,7 +14,7 @@ newline after leading space</textarea></div> <textarea id="textarea-with-multipl
 
 multiple leading newlines</textarea> <div id="div-with-textarea-with-multiple-leading-newlines"><textarea>
 
-multiple leading newlines</textarea></div><!--]-->`,
+multiple leading newlines</textarea></div><!--]--><!--]-->`,
 	test({ assert, target }) {
 		// Test for <textarea> tag
 		const elementTextarea = /** @type {HTMLTextAreaElement} */ (target.querySelector('#textarea'));
diff --git a/packages/svelte/tests/runtime-legacy/shared.ts b/packages/svelte/tests/runtime-legacy/shared.ts
index 05c1a982ec..7144543242 100644
--- a/packages/svelte/tests/runtime-legacy/shared.ts
+++ b/packages/svelte/tests/runtime-legacy/shared.ts
@@ -43,9 +43,9 @@ Promise.withResolvers = () => {
 export interface RuntimeTest<Props extends Record<string, any> = Record<string, any>>
 	extends BaseTest {
 	/** Use e.g. `mode: ['client']` to indicate that this test should never run in server/hydrate modes */
-	mode?: Array<'server' | 'client' | 'hydrate'>;
+	mode?: Array<'server' | 'async-server' | 'client' | 'hydrate'>;
 	/** Temporarily skip specific modes, without skipping the entire test */
-	skip_mode?: Array<'server' | 'client' | 'hydrate'>;
+	skip_mode?: Array<'server' | 'async-server' | 'client' | 'hydrate'>;
 	/** Skip if running with process.env.NO_ASYNC */
 	skip_no_async?: boolean;
 	/** Skip if running without process.env.NO_ASYNC */
@@ -83,7 +83,11 @@ export interface RuntimeTest<Props extends Record<string, any> = Record<string,
 		errors: any[];
 		hydrate: Function;
 	}) => void | Promise<void>;
-	test_ssr?: (args: { logs: any[]; assert: Assert }) => void | Promise<void>;
+	test_ssr?: (args: {
+		logs: any[];
+		assert: Assert;
+		variant: 'ssr' | 'async-ssr';
+	}) => void | Promise<void>;
 	accessors?: boolean;
 	immutable?: boolean;
 	intro?: boolean;
@@ -124,8 +128,8 @@ let console_warn = console.warn;
 let console_error = console.error;
 
 export function runtime_suite(runes: boolean) {
-	return suite_with_variants<RuntimeTest, 'hydrate' | 'ssr' | 'dom', CompileOptions>(
-		['dom', 'hydrate', 'ssr'],
+	return suite_with_variants<RuntimeTest, 'hydrate' | 'ssr' | 'async-ssr' | 'dom', CompileOptions>(
+		['dom', 'hydrate', 'ssr', 'async-ssr'],
 		(variant, config, test_name) => {
 			if (!async_mode && (config.skip_no_async || test_name.startsWith('async-'))) {
 				return true;
@@ -162,6 +166,22 @@ export function runtime_suite(runes: boolean) {
 				if (config.skip_mode?.includes('server')) return true;
 			}
 
+			if (variant === 'async-ssr') {
+				if (!runes || !async_mode) return 'no-test';
+				if (
+					(config.mode && !config.mode.includes('async-server')) ||
+					(!config.test_ssr &&
+						config.html === undefined &&
+						config.ssrHtml === undefined &&
+						config.error === undefined &&
+						config.runtime_error === undefined &&
+						!config.mode?.includes('async-server'))
+				) {
+					return 'no-test';
+				}
+				if (config.skip_mode?.includes('async-server')) return true;
+			}
+
 			return false;
 		},
 		(config, cwd) => {
@@ -207,7 +227,7 @@ async function common_setup(cwd: string, runes: boolean | undefined, config: Run
 async function run_test_variant(
 	cwd: string,
 	config: RuntimeTest,
-	variant: 'dom' | 'hydrate' | 'ssr',
+	variant: 'dom' | 'hydrate' | 'ssr' | 'async-ssr',
 	compileOptions: CompileOptions,
 	runes: boolean
 ) {
@@ -310,20 +330,26 @@ async function run_test_variant(
 
 		let snapshot = undefined;
 
-		if (variant === 'hydrate' || variant === 'ssr') {
+		if (variant === 'hydrate' || variant === 'ssr' || variant === 'async-ssr') {
 			config.before_test?.();
 			// ssr into target
 			const SsrSvelteComponent = (await import(`${cwd}/_output/server/main.svelte.js`)).default;
-			const { html, head } = render(SsrSvelteComponent, {
+			const render_result = render(SsrSvelteComponent, {
 				props: config.server_props ?? config.props ?? {},
 				idPrefix: config.id_prefix
 			});
+			const rendered =
+				variant === 'async-ssr' || (variant === 'hydrate' && compileOptions.experimental?.async)
+					? await render_result
+					: render_result;
+			const { body, head } = rendered;
 
-			fs.writeFileSync(`${cwd}/_output/rendered.html`, html);
-			target.innerHTML = html;
+			const prefix = variant === 'async-ssr' ? 'async_' : '';
+			fs.writeFileSync(`${cwd}/_output/${prefix}rendered.html`, body);
+			target.innerHTML = body;
 
 			if (head) {
-				fs.writeFileSync(`${cwd}/_output/rendered_head.html`, head);
+				fs.writeFileSync(`${cwd}/_output/${prefix}rendered_head.html`, head);
 				window.document.head.innerHTML = window.document.head.innerHTML + head;
 			}
 
@@ -338,7 +364,7 @@ async function run_test_variant(
 			target.innerHTML = '';
 		}
 
-		if (variant === 'ssr') {
+		if (variant === 'ssr' || variant === 'async-ssr') {
 			if (config.ssrHtml) {
 				assert_html_equal_with_options(target.innerHTML, config.ssrHtml, {
 					preserveComments:
@@ -361,7 +387,8 @@ async function run_test_variant(
 						...assert,
 						htmlEqual: assert_html_equal,
 						htmlEqualWithOptions: assert_html_equal_with_options
-					}
+					},
+					variant
 				});
 			}
 		} else {
diff --git a/packages/svelte/tests/runtime-runes/samples/async-no-pending-throws-sync/_config.js b/packages/svelte/tests/runtime-runes/samples/async-no-pending-throws-sync/_config.js
new file mode 100644
index 0000000000..366477d197
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-no-pending-throws-sync/_config.js
@@ -0,0 +1,7 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['server'],
+
+	error: 'await_invalid'
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-no-pending-throws-sync/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-no-pending-throws-sync/main.svelte
new file mode 100644
index 0000000000..4b8cd7203b
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-no-pending-throws-sync/main.svelte
@@ -0,0 +1 @@
+<p>{await Promise.resolve('hello')}</p>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-no-pending/_config.js b/packages/svelte/tests/runtime-runes/samples/async-no-pending/_config.js
new file mode 100644
index 0000000000..91b516e7c9
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-no-pending/_config.js
@@ -0,0 +1,17 @@
+import { tick } from 'svelte';
+import { ok, test } from '../../test';
+
+export default test({
+	skip_mode: ['server'],
+
+	ssrHtml: '<p>hello</p>',
+
+	html: '',
+
+	async test({ assert, target }) {
+		await tick();
+		const p = target.querySelector('p');
+		ok(p);
+		assert.htmlEqual(p.outerHTML, '<p>hello</p>');
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-no-pending/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-no-pending/main.svelte
new file mode 100644
index 0000000000..4b8cd7203b
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-no-pending/main.svelte
@@ -0,0 +1 @@
+<p>{await Promise.resolve('hello')}</p>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/A.svelte b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/A.svelte
new file mode 100644
index 0000000000..f73e368fc8
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/A.svelte
@@ -0,0 +1,9 @@
+<script lang="ts">
+	import { onDestroy } from 'svelte';
+	import { destroyed } from './destroyed.js';
+	import C from './C.svelte';
+	onDestroy(() => destroyed.push('A'));
+</script>
+
+<div>A</div>
+<C/>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/B.svelte b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/B.svelte
new file mode 100644
index 0000000000..8b107601c4
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/B.svelte
@@ -0,0 +1,9 @@
+<script lang="ts">
+	import { onDestroy } from 'svelte';
+	import { destroyed } from './destroyed.js';
+
+	onDestroy(() => destroyed.push('B'));
+  onDestroy(() => destroyed.push('B*'))
+</script>
+
+<div>B</div>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/C.svelte b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/C.svelte
new file mode 100644
index 0000000000..8b616d6e94
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/C.svelte
@@ -0,0 +1,5 @@
+<script lang="ts">
+	import { onDestroy } from 'svelte';
+	import { destroyed } from './destroyed.js';
+	onDestroy(() => destroyed.push('C'));
+</script>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/_config.js b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/_config.js
new file mode 100644
index 0000000000..32def88537
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/_config.js
@@ -0,0 +1,14 @@
+import { test } from '../../test';
+import { destroyed, reset } from './destroyed.js';
+
+export default test({
+	mode: ['async-server'],
+
+	before_test() {
+		reset();
+	},
+
+	test_ssr({ assert }) {
+		assert.deepEqual(destroyed, ['C', 'A', 'B', 'B*', 'root']);
+	}
+});
diff --git a/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/destroyed.js b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/destroyed.js
new file mode 100644
index 0000000000..1afebed3bd
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/destroyed.js
@@ -0,0 +1,4 @@
+/** @type {string[]} */
+export const destroyed = [];
+
+export const reset = () => (destroyed.length = 0);
diff --git a/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/main.svelte b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/main.svelte
new file mode 100644
index 0000000000..8503a54681
--- /dev/null
+++ b/packages/svelte/tests/runtime-runes/samples/async-ondestroy-ordering/main.svelte
@@ -0,0 +1,13 @@
+<script lang="ts">
+	import { onDestroy } from 'svelte';
+	import { destroyed } from './destroyed.js';
+	import A from './A.svelte';
+	import B from './B.svelte';
+
+	onDestroy(() => destroyed.push('root'));
+</script>
+
+{#if await Promise.resolve(true)}
+	<A/>
+{/if}
+<B/>
\ No newline at end of file
diff --git a/packages/svelte/tests/runtime-runes/samples/snippet-slot-let-error/_config.js b/packages/svelte/tests/runtime-runes/samples/snippet-slot-let-error/_config.js
index e8adfb38f2..4d892bd140 100644
--- a/packages/svelte/tests/runtime-runes/samples/snippet-slot-let-error/_config.js
+++ b/packages/svelte/tests/runtime-runes/samples/snippet-slot-let-error/_config.js
@@ -1,6 +1,7 @@
 import { test } from '../../test';
 
 export default test({
+	skip_mode: ['hydrate', 'server'],
 	compileOptions: {
 		dev: true
 	},
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-context-throws-after-await/_config.js b/packages/svelte/tests/server-side-rendering/samples/async-context-throws-after-await/_config.js
new file mode 100644
index 0000000000..a1b52a2df9
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-context-throws-after-await/_config.js
@@ -0,0 +1,6 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['async'],
+	error: 'lifecycle_outside_component'
+});
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-context-throws-after-await/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-context-throws-after-await/main.svelte
new file mode 100644
index 0000000000..8e770c214b
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-context-throws-after-await/main.svelte
@@ -0,0 +1,7 @@
+<script>
+	import { setContext } from 'svelte';
+
+	await Promise.resolve('hi');
+
+	setContext('key', 'value');
+</script>
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-each-fallback-hoisting/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-each-fallback-hoisting/_expected.html
new file mode 100644
index 0000000000..bf0d87ab1b
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-each-fallback-hoisting/_expected.html
@@ -0,0 +1 @@
+4
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-each-fallback-hoisting/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-each-fallback-hoisting/main.svelte
new file mode 100644
index 0000000000..e580345a2e
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-each-fallback-hoisting/main.svelte
@@ -0,0 +1,5 @@
+{#each await Promise.resolve([]) as item}
+  {await Promise.reject('This should never be reached')}
+{:else}
+  {await Promise.resolve(4)}
+{/each}
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-each-hoisting/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-each-hoisting/_expected.html
new file mode 100644
index 0000000000..d800886d9c
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-each-hoisting/_expected.html
@@ -0,0 +1 @@
+123
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-each-hoisting/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-each-hoisting/main.svelte
new file mode 100644
index 0000000000..4b6bf7eadc
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-each-hoisting/main.svelte
@@ -0,0 +1,9 @@
+<script lang="ts">
+  const first = Promise.resolve(1);
+  const second = Promise.resolve(2);
+  const third = Promise.resolve(3);
+</script>
+
+{#each await Promise.resolve([first, second, third]) as item}
+  {await item}
+{/each}
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/A.svelte b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/A.svelte
new file mode 100644
index 0000000000..5ddccbe17c
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/A.svelte
@@ -0,0 +1,9 @@
+<script>
+	let { promise } = $props();
+</script>
+
+<svelte:head>
+	{#if await promise}
+		<title>A</title>
+	{/if}
+</svelte:head>
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/B.svelte b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/B.svelte
new file mode 100644
index 0000000000..95b102e680
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/B.svelte
@@ -0,0 +1,7 @@
+<script>
+	let { promise } = $props();
+</script>
+
+<svelte:head>
+		<title>{(await promise) && 'B'}</title>
+</svelte:head>
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/_config.js b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/_config.js
new file mode 100644
index 0000000000..f47bee71df
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({});
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/_expected.html
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/_expected_head.html b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/_expected_head.html
new file mode 100644
index 0000000000..af5c5feba4
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/_expected_head.html
@@ -0,0 +1 @@
+<title>B</title>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/main.svelte
new file mode 100644
index 0000000000..9b49cf1c22
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-head-multiple-title-order-preserved/main.svelte
@@ -0,0 +1,27 @@
+<script>
+	import { tick } from 'svelte';
+	import A from './A.svelte';
+	import B from './B.svelte';
+
+	const main = Promise.withResolvers();
+	const a = Promise.withResolvers();
+	const b = Promise.withResolvers();
+
+	// regardless of resolution order, title should be the result of B, because it's the last-encountered
+	tick().then(() => {
+		main.resolve(true);
+		tick().then(() => {
+			b.resolve(true);
+		}).then(() => {
+			a.resolve(true);
+		});
+	})
+</script>
+
+<svelte:head>
+	{#if await main.promise}
+		<title>Main</title>
+	{/if}
+</svelte:head>
+<A promise={a.promise}/>
+<B promise={b.promise}/>
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-if-alternate-hoisting/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-if-alternate-hoisting/_expected.html
new file mode 100644
index 0000000000..c3b0e19566
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-if-alternate-hoisting/_expected.html
@@ -0,0 +1 @@
+yes yes yes
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-if-alternate-hoisting/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-if-alternate-hoisting/main.svelte
new file mode 100644
index 0000000000..a97f32f034
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-if-alternate-hoisting/main.svelte
@@ -0,0 +1,5 @@
+{#if await Promise.resolve(false)}
+  {await Promise.reject('no no no')}
+{:else}
+  {await Promise.resolve('yes yes yes')}
+{/if}
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-if-hoisting/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-if-hoisting/_expected.html
new file mode 100644
index 0000000000..c3b0e19566
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-if-hoisting/_expected.html
@@ -0,0 +1 @@
+yes yes yes
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-if-hoisting/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-if-hoisting/main.svelte
new file mode 100644
index 0000000000..4ca3462771
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-if-hoisting/main.svelte
@@ -0,0 +1,5 @@
+{#if await Promise.resolve(true)}
+  {await Promise.resolve('yes yes yes')}
+{:else}
+  {await Promise.reject('no no no')}
+{/if}
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-complex-value/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-complex-value/_expected.html
new file mode 100644
index 0000000000..f2fd8e71b9
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-complex-value/_expected.html
@@ -0,0 +1,3 @@
+<select>
+  <option selected>421</option>
+</select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-complex-value/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-complex-value/main.svelte
new file mode 100644
index 0000000000..2ad9b64509
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-complex-value/main.svelte
@@ -0,0 +1,3 @@
+<select value="421">
+  <option>{await Promise.resolve(42)}1</option>
+</select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-simple-value/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-simple-value/_expected.html
new file mode 100644
index 0000000000..f642109218
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-simple-value/_expected.html
@@ -0,0 +1,3 @@
+<select>
+  <option selected>42</option>
+</select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-simple-value/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-simple-value/main.svelte
new file mode 100644
index 0000000000..a5d91424cb
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-option-implicit-simple-value/main.svelte
@@ -0,0 +1,3 @@
+<select value={42}>
+  <option>{await Promise.resolve(42)}</option>
+</select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/Option.svelte b/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/Option.svelte
new file mode 100644
index 0000000000..a17413bd8d
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/Option.svelte
@@ -0,0 +1,5 @@
+<script>
+	let props = $props();
+</script>
+
+<option {...props}>{@render props.children?.()}</option>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/_expected.html
new file mode 100644
index 0000000000..96d1d8b233
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/_expected.html
@@ -0,0 +1 @@
+<select><option value="">--Please choose an option--</option><option value="dog" selected>Dog</option><option value="cat">Cat</option></select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/main.svelte
new file mode 100644
index 0000000000..aaf10c2cb3
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-select-value-component/main.svelte
@@ -0,0 +1,8 @@
+<script lang="ts">
+	import Option from './Option.svelte';
+</script>
+<select value={await Promise.resolve('dog')}>
+	<Option value="">--Please choose an option--</Option>
+	<Option value={await Promise.resolve('dog')}>Dog</Option>
+	<Option value="cat">Cat</Option>
+</select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value-complex/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value-complex/_expected.html
new file mode 100644
index 0000000000..de7cba8837
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value-complex/_expected.html
@@ -0,0 +1 @@
+<select><option>--Please choose an option--</option><option selected>dog</option><option>cat</option></select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value-complex/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value-complex/main.svelte
new file mode 100644
index 0000000000..2cc4065eb6
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value-complex/main.svelte
@@ -0,0 +1,13 @@
+<select value={await Promise.resolve('dog')}>
+	<option>
+		{@render option("--Please choose an option--")}
+	</option>
+	<option>
+		{@render option(Promise.resolve('dog'))}
+	</option>
+	<option>
+		{@render option(Promise.resolve('cat'))}
+	</option>
+</select>
+
+{#snippet option(val)}{await val}{/snippet}
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value/_expected.html b/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value/_expected.html
new file mode 100644
index 0000000000..de7cba8837
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value/_expected.html
@@ -0,0 +1 @@
+<select><option>--Please choose an option--</option><option selected>dog</option><option>cat</option></select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value/main.svelte b/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value/main.svelte
new file mode 100644
index 0000000000..8d9393cf6c
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/async-select-value-implicit-value/main.svelte
@@ -0,0 +1,5 @@
+<select value={await Promise.resolve('dog')}>
+	<option>--Please choose an option--</option>
+	<option>{await Promise.resolve('dog')}</option>
+	<option>cat</option>
+</select>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/comment-preserve/_expected.html b/packages/svelte/tests/server-side-rendering/samples/comment-preserve/_expected.html
index 3eb11afc34..df372583b1 100644
--- a/packages/svelte/tests/server-side-rendering/samples/comment-preserve/_expected.html
+++ b/packages/svelte/tests/server-side-rendering/samples/comment-preserve/_expected.html
@@ -1 +1 @@
-<!--[--><p>before</p><!-- a comment --><p>after</p><!--]-->
+<!--[--><!--[--><p>before</p><!-- a comment --><p>after</p><!--]--><!--]-->
diff --git a/packages/svelte/tests/server-side-rendering/samples/context/Child.svelte b/packages/svelte/tests/server-side-rendering/samples/context/Child.svelte
new file mode 100644
index 0000000000..fab18ea195
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/context/Child.svelte
@@ -0,0 +1,8 @@
+<script>
+	import { setContext, getContext } from 'svelte';
+
+	setContext('key', 'child value');
+	await Promise.resolve();
+</script>
+
+<div>{getContext('key')}</div>
diff --git a/packages/svelte/tests/server-side-rendering/samples/context/_config.js b/packages/svelte/tests/server-side-rendering/samples/context/_config.js
new file mode 100644
index 0000000000..05de37a8bd
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/context/_config.js
@@ -0,0 +1,5 @@
+import { test } from '../../test';
+
+export default test({
+	mode: ['async']
+});
diff --git a/packages/svelte/tests/server-side-rendering/samples/context/_expected.html b/packages/svelte/tests/server-side-rendering/samples/context/_expected.html
new file mode 100644
index 0000000000..554133d8d9
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/context/_expected.html
@@ -0,0 +1,3 @@
+<div>value</div>
+<div>value</div>
+<div>child value</div>
\ No newline at end of file
diff --git a/packages/svelte/tests/server-side-rendering/samples/context/main.svelte b/packages/svelte/tests/server-side-rendering/samples/context/main.svelte
new file mode 100644
index 0000000000..fd75a6cbae
--- /dev/null
+++ b/packages/svelte/tests/server-side-rendering/samples/context/main.svelte
@@ -0,0 +1,11 @@
+<script>
+	import { getContext, setContext } from 'svelte';
+	import Child from './Child.svelte';
+
+	setContext('key', 'value');
+	await Promise.resolve();
+</script>
+
+<div>{getContext('key')}</div>
+<div>{(await Promise.resolve(true)) && getContext('key')}</div>
+<Child />
diff --git a/packages/svelte/tests/server-side-rendering/samples/head-meta-hydrate-duplicate/_expected.html b/packages/svelte/tests/server-side-rendering/samples/head-meta-hydrate-duplicate/_expected.html
index 8fb1be347c..0919060246 100644
--- a/packages/svelte/tests/server-side-rendering/samples/head-meta-hydrate-duplicate/_expected.html
+++ b/packages/svelte/tests/server-side-rendering/samples/head-meta-hydrate-duplicate/_expected.html
@@ -1 +1 @@
-<!--[--><div>Just a dummy page.</div><!--]-->
+<!--[--><!--[--><div>Just a dummy page.</div><!--]--><!--]-->
diff --git a/packages/svelte/tests/server-side-rendering/samples/head-svelte-components-raw-content/_expected.html b/packages/svelte/tests/server-side-rendering/samples/head-svelte-components-raw-content/_expected.html
index 290179a702..8c9e75c033 100644
--- a/packages/svelte/tests/server-side-rendering/samples/head-svelte-components-raw-content/_expected.html
+++ b/packages/svelte/tests/server-side-rendering/samples/head-svelte-components-raw-content/_expected.html
@@ -1,4 +1,5 @@
 <!--[-->
+<!--[-->
 <!---->
 <title>lorem</title>
 <!---->
@@ -15,3 +16,4 @@
 </script>
 <!---->
 <!--]-->
+<!--]-->
diff --git a/packages/svelte/tests/server-side-rendering/samples/invalid-nested-svelte-element/_config.js b/packages/svelte/tests/server-side-rendering/samples/invalid-nested-svelte-element/_config.js
index 71edff6a68..6325ea7d0e 100644
--- a/packages/svelte/tests/server-side-rendering/samples/invalid-nested-svelte-element/_config.js
+++ b/packages/svelte/tests/server-side-rendering/samples/invalid-nested-svelte-element/_config.js
@@ -4,8 +4,6 @@ export default test({
 	compileOptions: {
 		dev: true
 	},
-
-	errors: [
+	error:
 		'node_invalid_placement_ssr: `<p>` (packages/svelte/tests/server-side-rendering/samples/invalid-nested-svelte-element/main.svelte:2:1) cannot be a child of `<p>` (packages/svelte/tests/server-side-rendering/samples/invalid-nested-svelte-element/main.svelte:1:0)\n\nThis can cause content to shift around as the browser repairs the HTML, and will likely result in a `hydration_mismatch` warning.'
-	]
 });
diff --git a/packages/svelte/tests/server-side-rendering/test.ts b/packages/svelte/tests/server-side-rendering/test.ts
index 3e57539427..7eede332a7 100644
--- a/packages/svelte/tests/server-side-rendering/test.ts
+++ b/packages/svelte/tests/server-side-rendering/test.ts
@@ -9,79 +9,133 @@ import { assert } from 'vitest';
 import { render } from 'svelte/server';
 import { compile_directory, should_update_expected, try_read_file } from '../helpers.js';
 import { assert_html_equal_with_options } from '../html_equal.js';
-import { suite, type BaseTest } from '../suite.js';
+import { suite_with_variants, type BaseTest } from '../suite.js';
 import type { CompileOptions } from '#compiler';
+import { seen } from '../../src/internal/server/dev.js';
 
 interface SSRTest extends BaseTest {
+	mode?: ('sync' | 'async')[];
 	compileOptions?: Partial<CompileOptions>;
+	load_compiled?: boolean;
 	props?: Record<string, any>;
 	id_prefix?: string;
 	withoutNormalizeHtml?: boolean;
-	errors?: string[];
+	error?: string;
 }
 
-// eslint-disable-next-line no-console
-let console_error = console.error;
+// TODO remove this shim when we can
+// @ts-expect-error
+Promise.withResolvers = () => {
+	let resolve;
+	let reject;
+
+	const promise = new Promise((f, r) => {
+		resolve = f;
+		reject = r;
+	});
+
+	return { promise, resolve, reject };
+};
+
+const { test, run } = suite_with_variants<SSRTest, 'sync' | 'async', CompileOptions>(
+	['sync', 'async'],
+	(variant, config, test_name) => {
+		if (config.mode && !config.mode.includes(variant)) {
+			return 'no-test';
+		}
 
-const { test, run } = suite<SSRTest>(async (config, test_dir) => {
-	await compile_directory(test_dir, 'server', config.compileOptions);
+		if (test_name.startsWith('async') && variant === 'sync') {
+			return 'no-test';
+		}
 
-	const errors: string[] = [];
+		return false;
+	},
+	async (config, test_dir) => {
+		const compile_options = {
+			experimental: {
+				async: true,
+				...config.compileOptions?.experimental
+			},
+			...config.compileOptions
+		};
+
+		if (!config.load_compiled) {
+			await compile_directory(test_dir, 'server', compile_options);
+		}
 
-	console.error = (...args) => {
-		errors.push(...args);
-	};
+		return compile_options;
+	},
+	async (config, test_dir, variant, compile_options) => {
+		const Component = (await import(`${test_dir}/_output/server/main.svelte.js`)).default;
+		const expected_html = try_read_file(`${test_dir}/_expected.html`);
+		const is_async = variant === 'async';
 
-	const Component = (await import(`${test_dir}/_output/server/main.svelte.js`)).default;
-	const expected_html = try_read_file(`${test_dir}/_expected.html`);
-	const rendered = render(Component, { props: config.props || {}, idPrefix: config.id_prefix });
-	const { body, head } = rendered;
+		seen?.clear();
+
+		let rendered;
+		try {
+			const render_result = render(Component, {
+				props: config.props || {},
+				idPrefix: config.id_prefix
+			});
+			rendered = is_async ? await render_result : render_result;
+		} catch (error) {
+			if (config.error) {
+				assert.deepEqual((error as Error).message, config.error);
+				return;
+			} else {
+				throw error;
+			}
+		}
 
-	fs.writeFileSync(`${test_dir}/_output/rendered.html`, body);
+		const { body, head } = rendered;
 
-	if (head) {
-		fs.writeFileSync(`${test_dir}/_output/rendered_head.html`, head);
-	}
+		fs.writeFileSync(
+			`${test_dir}/_output/${is_async ? 'async_rendered.html' : 'rendered.html'}`,
+			body
+		);
 
-	try {
-		assert_html_equal_with_options(body, expected_html || '', {
-			preserveComments: config.compileOptions?.preserveComments,
-			withoutNormalizeHtml: config.withoutNormalizeHtml
-		});
-	} catch (error: any) {
-		if (should_update_expected()) {
-			fs.writeFileSync(`${test_dir}/_expected.html`, body);
-			console.log(`Updated ${test_dir}/_expected.html.`);
-		} else {
-			error.message += '\n' + `${test_dir}/main.svelte`;
-			throw error;
+		if (head) {
+			fs.writeFileSync(
+				`${test_dir}/_output/${is_async ? 'async_rendered_head.html' : 'rendered_head.html'}`,
+				head
+			);
 		}
-	}
 
-	if (fs.existsSync(`${test_dir}/_expected_head.html`)) {
 		try {
-			assert_html_equal_with_options(
-				head,
-				fs.readFileSync(`${test_dir}/_expected_head.html`, 'utf-8'),
-				{}
-			);
+			assert_html_equal_with_options(body, expected_html || '', {
+				preserveComments: compile_options.preserveComments,
+				withoutNormalizeHtml: config.withoutNormalizeHtml
+			});
 		} catch (error: any) {
 			if (should_update_expected()) {
-				fs.writeFileSync(`${test_dir}/_expected_head.html`, head);
-				console.log(`Updated ${test_dir}/_expected_head.html.`);
-				error.message += '\n' + `${test_dir}/main.svelte`;
+				fs.writeFileSync(`${test_dir}/_expected.html`, body);
+				console.log(`Updated ${test_dir}/_expected.html.`);
 			} else {
+				error.message += '\n' + `${test_dir}/main.svelte`;
 				throw error;
 			}
 		}
-	}
 
-	if (errors.length > 0) {
-		assert.deepEqual(config.errors, errors);
+		if (fs.existsSync(`${test_dir}/_expected_head.html`)) {
+			try {
+				assert_html_equal_with_options(
+					head,
+					fs.readFileSync(`${test_dir}/_expected_head.html`, 'utf-8'),
+					{}
+				);
+			} catch (error: any) {
+				if (should_update_expected()) {
+					fs.writeFileSync(`${test_dir}/_expected_head.html`, head);
+					console.log(`Updated ${test_dir}/_expected_head.html.`);
+					error.message += '\n' + `${test_dir}/main.svelte`;
+				} else {
+					throw error;
+				}
+			}
+		}
 	}
-
-	console.error = console_error;
-});
+);
 
 export { test };
 
diff --git a/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_config.js b/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_config.js
new file mode 100644
index 0000000000..2e30bbeb16
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({ compileOptions: { experimental: { async: true } } });
diff --git a/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_expected/client/index.svelte.js b/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_expected/client/index.svelte.js
new file mode 100644
index 0000000000..cf667e1624
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_expected/client/index.svelte.js
@@ -0,0 +1,35 @@
+import 'svelte/internal/disclose-version';
+import 'svelte/internal/flags/async';
+import * as $ from 'svelte/internal/client';
+
+export default function Async_each_fallback_hoisting($$anchor) {
+	var fragment = $.comment();
+	var node = $.first_child(fragment);
+
+	$.async(node, [() => Promise.resolve([])], (node, $$collection) => {
+		$.each(
+			node,
+			16,
+			() => $.get($$collection),
+			$.index,
+			($$anchor, item) => {
+				$.next();
+
+				var text = $.text();
+
+				$.template_effect(($0) => $.set_text(text, $0), void 0, [() => Promise.reject('This should never be reached')]);
+				$.append($$anchor, text);
+			},
+			($$anchor) => {
+				$.next();
+
+				var text_1 = $.text();
+
+				$.template_effect(($0) => $.set_text(text_1, $0), void 0, [() => Promise.resolve(4)]);
+				$.append($$anchor, text_1);
+			}
+		);
+	});
+
+	$.append($$anchor, fragment);
+}
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_expected/server/index.svelte.js
new file mode 100644
index 0000000000..808818cc9e
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/_expected/server/index.svelte.js
@@ -0,0 +1,25 @@
+import 'svelte/internal/flags/async';
+import * as $ from 'svelte/internal/server';
+
+export default function Async_each_fallback_hoisting($$payload) {
+	$$payload.child(async ($$payload) => {
+		const each_array = $.ensure_array_like(await Promise.resolve([]));
+
+		if (each_array.length !== 0) {
+			$$payload.push('<!--[-->');
+
+			for (let $$index = 0, $$length = each_array.length; $$index < $$length; $$index++) {
+				let item = each_array[$$index];
+
+				$$payload.push(`<!---->`);
+				$$payload.push(async () => $.escape(await Promise.reject('This should never be reached')));
+			}
+		} else {
+			$$payload.push('<!--[!-->');
+			$$payload.push(`<!---->`);
+			$$payload.push(async () => $.escape(await Promise.resolve(4)));
+		}
+	});
+
+	$$payload.push(`<!--]-->`);
+}
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/index.svelte b/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/index.svelte
new file mode 100644
index 0000000000..e580345a2e
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-each-fallback-hoisting/index.svelte
@@ -0,0 +1,5 @@
+{#each await Promise.resolve([]) as item}
+  {await Promise.reject('This should never be reached')}
+{:else}
+  {await Promise.resolve(4)}
+{/each}
diff --git a/packages/svelte/tests/snapshot/samples/async-each-hoisting/_config.js b/packages/svelte/tests/snapshot/samples/async-each-hoisting/_config.js
new file mode 100644
index 0000000000..2e30bbeb16
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-each-hoisting/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({ compileOptions: { experimental: { async: true } } });
diff --git a/packages/svelte/tests/snapshot/samples/async-each-hoisting/_expected/client/index.svelte.js b/packages/svelte/tests/snapshot/samples/async-each-hoisting/_expected/client/index.svelte.js
new file mode 100644
index 0000000000..a1535d6886
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-each-hoisting/_expected/client/index.svelte.js
@@ -0,0 +1,24 @@
+import 'svelte/internal/disclose-version';
+import 'svelte/internal/flags/async';
+import * as $ from 'svelte/internal/client';
+
+export default function Async_each_hoisting($$anchor) {
+	const first = Promise.resolve(1);
+	const second = Promise.resolve(2);
+	const third = Promise.resolve(3);
+	var fragment = $.comment();
+	var node = $.first_child(fragment);
+
+	$.async(node, [() => Promise.resolve([first, second, third])], (node, $$collection) => {
+		$.each(node, 17, () => $.get($$collection), $.index, ($$anchor, item) => {
+			$.next();
+
+			var text = $.text();
+
+			$.template_effect(($0) => $.set_text(text, $0), void 0, [() => $.get(item)]);
+			$.append($$anchor, text);
+		});
+	});
+
+	$.append($$anchor, fragment);
+}
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/async-each-hoisting/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/async-each-hoisting/_expected/server/index.svelte.js
new file mode 100644
index 0000000000..6c2f837954
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-each-hoisting/_expected/server/index.svelte.js
@@ -0,0 +1,23 @@
+import 'svelte/internal/flags/async';
+import * as $ from 'svelte/internal/server';
+
+export default function Async_each_hoisting($$payload) {
+	const first = Promise.resolve(1);
+	const second = Promise.resolve(2);
+	const third = Promise.resolve(3);
+
+	$$payload.push(`<!--[-->`);
+
+	$$payload.child(async ($$payload) => {
+		const each_array = $.ensure_array_like(await Promise.resolve([first, second, third]));
+
+		for (let $$index = 0, $$length = each_array.length; $$index < $$length; $$index++) {
+			let item = each_array[$$index];
+
+			$$payload.push(`<!---->`);
+			$$payload.push(async () => $.escape(await item));
+		}
+	});
+
+	$$payload.push(`<!--]-->`);
+}
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/async-each-hoisting/index.svelte b/packages/svelte/tests/snapshot/samples/async-each-hoisting/index.svelte
new file mode 100644
index 0000000000..4b6bf7eadc
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-each-hoisting/index.svelte
@@ -0,0 +1,9 @@
+<script lang="ts">
+  const first = Promise.resolve(1);
+  const second = Promise.resolve(2);
+  const third = Promise.resolve(3);
+</script>
+
+{#each await Promise.resolve([first, second, third]) as item}
+  {await item}
+{/each}
diff --git a/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_config.js b/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_config.js
new file mode 100644
index 0000000000..2e30bbeb16
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({ compileOptions: { experimental: { async: true } } });
diff --git a/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_expected/client/index.svelte.js b/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_expected/client/index.svelte.js
new file mode 100644
index 0000000000..e385f5d234
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_expected/client/index.svelte.js
@@ -0,0 +1,30 @@
+import 'svelte/internal/disclose-version';
+import 'svelte/internal/flags/async';
+import * as $ from 'svelte/internal/client';
+
+export default function Async_if_alternate_hoisting($$anchor) {
+	var fragment = $.comment();
+	var node = $.first_child(fragment);
+
+	$.async(node, [() => Promise.resolve(false)], (node, $$condition) => {
+		var consequent = ($$anchor) => {
+			var text = $.text();
+
+			$.template_effect(($0) => $.set_text(text, $0), void 0, [() => Promise.reject('no no no')]);
+			$.append($$anchor, text);
+		};
+
+		var alternate = ($$anchor) => {
+			var text_1 = $.text();
+
+			$.template_effect(($0) => $.set_text(text_1, $0), void 0, [() => Promise.resolve('yes yes yes')]);
+			$.append($$anchor, text_1);
+		};
+
+		$.if(node, ($$render) => {
+			if ($.get($$condition)) $$render(consequent); else $$render(alternate, false);
+		});
+	});
+
+	$.append($$anchor, fragment);
+}
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_expected/server/index.svelte.js
new file mode 100644
index 0000000000..a645882a54
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/_expected/server/index.svelte.js
@@ -0,0 +1,16 @@
+import 'svelte/internal/flags/async';
+import * as $ from 'svelte/internal/server';
+
+export default function Async_if_alternate_hoisting($$payload) {
+	$$payload.child(async ($$payload) => {
+		if (await Promise.resolve(false)) {
+			$$payload.push('<!--[-->');
+			$$payload.push(async () => $.escape(await Promise.reject('no no no')));
+		} else {
+			$$payload.push('<!--[!-->');
+			$$payload.push(async () => $.escape(await Promise.resolve('yes yes yes')));
+		}
+	});
+
+	$$payload.push(`<!--]-->`);
+}
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/index.svelte b/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/index.svelte
new file mode 100644
index 0000000000..a97f32f034
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-if-alternate-hoisting/index.svelte
@@ -0,0 +1,5 @@
+{#if await Promise.resolve(false)}
+  {await Promise.reject('no no no')}
+{:else}
+  {await Promise.resolve('yes yes yes')}
+{/if}
diff --git a/packages/svelte/tests/snapshot/samples/async-if-hoisting/_config.js b/packages/svelte/tests/snapshot/samples/async-if-hoisting/_config.js
new file mode 100644
index 0000000000..2e30bbeb16
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-if-hoisting/_config.js
@@ -0,0 +1,3 @@
+import { test } from '../../test';
+
+export default test({ compileOptions: { experimental: { async: true } } });
diff --git a/packages/svelte/tests/snapshot/samples/async-if-hoisting/_expected/client/index.svelte.js b/packages/svelte/tests/snapshot/samples/async-if-hoisting/_expected/client/index.svelte.js
new file mode 100644
index 0000000000..356e8e9607
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-if-hoisting/_expected/client/index.svelte.js
@@ -0,0 +1,30 @@
+import 'svelte/internal/disclose-version';
+import 'svelte/internal/flags/async';
+import * as $ from 'svelte/internal/client';
+
+export default function Async_if_hoisting($$anchor) {
+	var fragment = $.comment();
+	var node = $.first_child(fragment);
+
+	$.async(node, [() => Promise.resolve(true)], (node, $$condition) => {
+		var consequent = ($$anchor) => {
+			var text = $.text();
+
+			$.template_effect(($0) => $.set_text(text, $0), void 0, [() => Promise.resolve('yes yes yes')]);
+			$.append($$anchor, text);
+		};
+
+		var alternate = ($$anchor) => {
+			var text_1 = $.text();
+
+			$.template_effect(($0) => $.set_text(text_1, $0), void 0, [() => Promise.reject('no no no')]);
+			$.append($$anchor, text_1);
+		};
+
+		$.if(node, ($$render) => {
+			if ($.get($$condition)) $$render(consequent); else $$render(alternate, false);
+		});
+	});
+
+	$.append($$anchor, fragment);
+}
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/async-if-hoisting/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/async-if-hoisting/_expected/server/index.svelte.js
new file mode 100644
index 0000000000..1d75b5ad96
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-if-hoisting/_expected/server/index.svelte.js
@@ -0,0 +1,16 @@
+import 'svelte/internal/flags/async';
+import * as $ from 'svelte/internal/server';
+
+export default function Async_if_hoisting($$payload) {
+	$$payload.child(async ($$payload) => {
+		if (await Promise.resolve(true)) {
+			$$payload.push('<!--[-->');
+			$$payload.push(async () => $.escape(await Promise.resolve('yes yes yes')));
+		} else {
+			$$payload.push('<!--[!-->');
+			$$payload.push(async () => $.escape(await Promise.reject('no no no')));
+		}
+	});
+
+	$$payload.push(`<!--]-->`);
+}
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/async-if-hoisting/index.svelte b/packages/svelte/tests/snapshot/samples/async-if-hoisting/index.svelte
new file mode 100644
index 0000000000..4ca3462771
--- /dev/null
+++ b/packages/svelte/tests/snapshot/samples/async-if-hoisting/index.svelte
@@ -0,0 +1,5 @@
+{#if await Promise.resolve(true)}
+  {await Promise.resolve('yes yes yes')}
+{:else}
+  {await Promise.reject('no no no')}
+{/if}
diff --git a/packages/svelte/tests/snapshot/samples/await-block-scope/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/await-block-scope/_expected/server/index.svelte.js
index cc2628c852..c0e3512178 100644
--- a/packages/svelte/tests/snapshot/samples/await-block-scope/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/await-block-scope/_expected/server/index.svelte.js
@@ -8,7 +8,7 @@ export default function Await_block_scope($$payload) {
 		counter.count += 1;
 	}
 
-	$$payload.out.push(`<button>clicks: ${$.escape(counter.count)}</button> `);
+	$$payload.push(`<button>clicks: ${$.escape(counter.count)}</button> `);
 	$.await($$payload, promise, () => {}, (counter) => {});
-	$$payload.out.push(`<!--]--> ${$.escape(counter.count)}`);
+	$$payload.push(`<!--]--> ${$.escape(counter.count)}`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/bind-component-snippet/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/bind-component-snippet/_expected/server/index.svelte.js
index c0db7d2fd5..f2b687489b 100644
--- a/packages/svelte/tests/snapshot/samples/bind-component-snippet/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/bind-component-snippet/_expected/server/index.svelte.js
@@ -2,7 +2,7 @@ import * as $ from 'svelte/internal/server';
 import TextInput from './Child.svelte';
 
 function snippet($$payload) {
-	$$payload.out.push(`<!---->Something`);
+	$$payload.push(`<!---->Something`);
 }
 
 export default function Bind_component_snippet($$payload) {
@@ -23,14 +23,14 @@ export default function Bind_component_snippet($$payload) {
 			}
 		});
 
-		$$payload.out.push(`<!----> value: ${$.escape(value)}`);
+		$$payload.push(`<!----> value: ${$.escape(value)}`);
 	}
 
 	do {
 		$$settled = true;
-		$$inner_payload = $.copy_payload($$payload);
+		$$inner_payload = $$payload.copy();
 		$$render_inner($$inner_payload);
 	} while (!$$settled);
 
-	$.assign_payload($$payload, $$inner_payload);
+	$$payload.subsume($$inner_payload);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/class-state-field-constructor-assignment/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/class-state-field-constructor-assignment/_expected/server/index.svelte.js
index abfc264fea..e426a08989 100644
--- a/packages/svelte/tests/snapshot/samples/class-state-field-constructor-assignment/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/class-state-field-constructor-assignment/_expected/server/index.svelte.js
@@ -1,38 +1,36 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Class_state_field_constructor_assignment($$payload, $$props) {
-	$.push();
-
-	class Foo {
-		a = 0;
-		#b;
-		#foo = $.derived(() => ({ bar: this.a * 2 }));
-
-		get foo() {
-			return this.#foo();
-		}
-
-		set foo($$value) {
-			return this.#foo($$value);
-		}
-
-		#bar = $.derived(() => ({ baz: this.foo }));
-
-		get bar() {
-			return this.#bar();
-		}
-
-		set bar($$value) {
-			return this.#bar($$value);
+	$$payload.component(($$payload) => {
+		class Foo {
+			a = 0;
+			#b;
+			#foo = $.derived(() => ({ bar: this.a * 2 }));
+
+			get foo() {
+				return this.#foo();
+			}
+
+			set foo($$value) {
+				return this.#foo($$value);
+			}
+
+			#bar = $.derived(() => ({ baz: this.foo }));
+
+			get bar() {
+				return this.#bar();
+			}
+
+			set bar($$value) {
+				return this.#bar($$value);
+			}
+
+			constructor() {
+				this.a = 1;
+				this.#b = 2;
+				this.foo.bar = 3;
+				this.bar = 4;
+			}
 		}
-
-		constructor() {
-			this.a = 1;
-			this.#b = 2;
-			this.foo.bar = 3;
-			this.bar = 4;
-		}
-	}
-
-	$.pop();
+	});
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/delegated-locally-declared-shadowed/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/delegated-locally-declared-shadowed/_expected/server/index.svelte.js
index ac3dfcd2cb..a17c437cd9 100644
--- a/packages/svelte/tests/snapshot/samples/delegated-locally-declared-shadowed/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/delegated-locally-declared-shadowed/_expected/server/index.svelte.js
@@ -1,13 +1,13 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Delegated_locally_declared_shadowed($$payload) {
-	const each_array = $.ensure_array_like({ length: 1 });
+	$$payload.push(`<!--[-->`);
 
-	$$payload.out.push(`<!--[-->`);
+	const each_array = $.ensure_array_like({ length: 1 });
 
 	for (let index = 0, $$length = each_array.length; index < $$length; index++) {
-		$$payload.out.push(`<button type="button"${$.attr('data-index', index)}>B</button>`);
+		$$payload.push(`<button type="button"${$.attr('data-index', index)}>B</button>`);
 	}
 
-	$$payload.out.push(`<!--]-->`);
+	$$payload.push(`<!--]-->`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/dynamic-attributes-casing/_expected/server/main.svelte.js b/packages/svelte/tests/snapshot/samples/dynamic-attributes-casing/_expected/server/main.svelte.js
index 9c837d4e1d..deaeaf6bfa 100644
--- a/packages/svelte/tests/snapshot/samples/dynamic-attributes-casing/_expected/server/main.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/dynamic-attributes-casing/_expected/server/main.svelte.js
@@ -6,5 +6,5 @@ export default function Main($$payload) {
 
 	let y = () => 'test';
 
-	$$payload.out.push(`<div${$.attr('foobar', x)}></div> <svg${$.attr('viewBox', x)}></svg> <custom-element${$.attr('foobar', x)}></custom-element> <div${$.attr('foobar', y())}></div> <svg${$.attr('viewBox', y())}></svg> <custom-element${$.attr('foobar', y())}></custom-element>`);
+	$$payload.push(`<div${$.attr('foobar', x)}></div> <svg${$.attr('viewBox', x)}></svg> <custom-element${$.attr('foobar', x)}></custom-element> <div${$.attr('foobar', y())}></div> <svg${$.attr('viewBox', y())}></svg> <custom-element${$.attr('foobar', y())}></custom-element>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/each-index-non-null/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/each-index-non-null/_expected/server/index.svelte.js
index 8fa0c5f28c..abec4f42fa 100644
--- a/packages/svelte/tests/snapshot/samples/each-index-non-null/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/each-index-non-null/_expected/server/index.svelte.js
@@ -1,13 +1,13 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Each_index_non_null($$payload) {
-	const each_array = $.ensure_array_like(Array(10));
+	$$payload.push(`<!--[-->`);
 
-	$$payload.out.push(`<!--[-->`);
+	const each_array = $.ensure_array_like(Array(10));
 
 	for (let i = 0, $$length = each_array.length; i < $$length; i++) {
-		$$payload.out.push(`<p>index: ${$.escape(i)}</p>`);
+		$$payload.push(`<p>index: ${$.escape(i)}</p>`);
 	}
 
-	$$payload.out.push(`<!--]-->`);
+	$$payload.push(`<!--]-->`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/each-string-template/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/each-string-template/_expected/server/index.svelte.js
index 6dbe8130da..fda6e5fbb3 100644
--- a/packages/svelte/tests/snapshot/samples/each-string-template/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/each-string-template/_expected/server/index.svelte.js
@@ -1,15 +1,15 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Each_string_template($$payload) {
-	const each_array = $.ensure_array_like(['foo', 'bar', 'baz']);
+	$$payload.push(`<!--[-->`);
 
-	$$payload.out.push(`<!--[-->`);
+	const each_array = $.ensure_array_like(['foo', 'bar', 'baz']);
 
 	for (let $$index = 0, $$length = each_array.length; $$index < $$length; $$index++) {
 		let thing = each_array[$$index];
 
-		$$payload.out.push(`<!---->${$.escape(thing)}, `);
+		$$payload.push(`<!---->${$.escape(thing)}, `);
 	}
 
-	$$payload.out.push(`<!--]-->`);
+	$$payload.push(`<!--]-->`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/function-prop-no-getter/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/function-prop-no-getter/_expected/server/index.svelte.js
index ce4f09ed1d..a9fa4efd50 100644
--- a/packages/svelte/tests/snapshot/samples/function-prop-no-getter/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/function-prop-no-getter/_expected/server/index.svelte.js
@@ -15,7 +15,7 @@ export default function Function_prop_no_getter($$payload) {
 		onmouseenter: () => count = plusOne(count),
 
 		children: ($$payload) => {
-			$$payload.out.push(`<!---->clicks: ${$.escape(count)}`);
+			$$payload.push(`<!---->clicks: ${$.escape(count)}`);
 		},
 
 		$$slots: { default: true }
diff --git a/packages/svelte/tests/snapshot/samples/functional-templating/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/functional-templating/_expected/server/index.svelte.js
index b1a0a5f9e6..e23a50cff5 100644
--- a/packages/svelte/tests/snapshot/samples/functional-templating/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/functional-templating/_expected/server/index.svelte.js
@@ -1,5 +1,5 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Functional_templating($$payload) {
-	$$payload.out.push(`<h1>hello</h1> <div class="potato"><p>child element</p> <p>another child element</p></div>`);
+	$$payload.push(`<h1>hello</h1> <div class="potato"><p>child element</p> <p>another child element</p></div>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/hello-world/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/hello-world/_expected/server/index.svelte.js
index 30f6d6b74a..6bdf5b4495 100644
--- a/packages/svelte/tests/snapshot/samples/hello-world/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/hello-world/_expected/server/index.svelte.js
@@ -1,5 +1,5 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Hello_world($$payload) {
-	$$payload.out.push(`<h1>hello world</h1>`);
+	$$payload.push(`<h1>hello world</h1>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/hmr/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/hmr/_expected/server/index.svelte.js
index ea1d12c83b..99813a32b1 100644
--- a/packages/svelte/tests/snapshot/samples/hmr/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/hmr/_expected/server/index.svelte.js
@@ -1,5 +1,5 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Hmr($$payload) {
-	$$payload.out.push(`<h1>hello world</h1>`);
+	$$payload.push(`<h1>hello world</h1>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/server/index.svelte.js
index 18e01b4f72..f096ddd3ba 100644
--- a/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/nullish-coallescence-omittance/_expected/server/index.svelte.js
@@ -4,5 +4,5 @@ export default function Nullish_coallescence_omittance($$payload) {
 	let name = 'world';
 	let count = 0;
 
-	$$payload.out.push(`<h1>Hello, world!</h1> <b>123</b> <button>Count is ${$.escape(count)}</button> <h1>Hello, world</h1>`);
+	$$payload.push(`<h1>Hello, world!</h1> <b>123</b> <button>Count is ${$.escape(count)}</button> <h1>Hello, world</h1>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/props-identifier/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/props-identifier/_expected/server/index.svelte.js
index 33a3633939..7871172433 100644
--- a/packages/svelte/tests/snapshot/samples/props-identifier/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/props-identifier/_expected/server/index.svelte.js
@@ -1,16 +1,15 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Props_identifier($$payload, $$props) {
-	$.push();
+	$$payload.component(($$payload) => {
+		let { $$slots, $$events, ...props } = $$props;
 
-	let { $$slots, $$events, ...props } = $$props;
-
-	props.a;
-	props[a];
-	props.a.b;
-	props.a.b = true;
-	props.a = true;
-	props[a] = true;
-	props;
-	$.pop();
+		props.a;
+		props[a];
+		props.a.b;
+		props.a.b = true;
+		props.a = true;
+		props[a] = true;
+		props;
+	});
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/purity/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/purity/_expected/server/index.svelte.js
index 29b0d0d594..b19e3aac52 100644
--- a/packages/svelte/tests/snapshot/samples/purity/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/purity/_expected/server/index.svelte.js
@@ -1,7 +1,7 @@
 import * as $ from 'svelte/internal/server';
 
 export default function Purity($$payload) {
-	$$payload.out.push(`<p>0</p> <p>${$.escape(location.href)}</p> `);
+	$$payload.push(`<p>0</p> <p>${$.escape(location.href)}</p> `);
 	Child($$payload, { prop: encodeURIComponent('hello') });
-	$$payload.out.push(`<!---->`);
+	$$payload.push(`<!---->`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/skip-static-subtree/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/skip-static-subtree/_expected/server/index.svelte.js
index bad475ec86..e49480f682 100644
--- a/packages/svelte/tests/snapshot/samples/skip-static-subtree/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/skip-static-subtree/_expected/server/index.svelte.js
@@ -3,5 +3,5 @@ import * as $ from 'svelte/internal/server';
 export default function Skip_static_subtree($$payload, $$props) {
 	let { title, content } = $$props;
 
-	$$payload.out.push(`<header><nav><a href="/">Home</a> <a href="/away">Away</a></nav></header> <main><h1>${$.escape(title)}</h1> <div class="static"><p>we don't need to traverse these nodes</p></div> <p>or</p> <p>these</p> <p>ones</p> ${$.html(content)} <p>these</p> <p>trailing</p> <p>nodes</p> <p>can</p> <p>be</p> <p>completely</p> <p>ignored</p></main> <cant-skip><custom-elements with="attributes"></custom-elements></cant-skip> <div><input autofocus/></div> <div><source muted/></div> <select><option value="a"${$.maybe_selected($$payload, 'a')}>a</option></select> <img src="..." alt="" loading="lazy"/> <div><img src="..." alt="" loading="lazy"/></div>`);
+	$$payload.push(`<header><nav><a href="/">Home</a> <a href="/away">Away</a></nav></header> <main><h1>${$.escape(title)}</h1> <div class="static"><p>we don't need to traverse these nodes</p></div> <p>or</p> <p>these</p> <p>ones</p> ${$.html(content)} <p>these</p> <p>trailing</p> <p>nodes</p> <p>can</p> <p>be</p> <p>completely</p> <p>ignored</p></main> <cant-skip><custom-elements with="attributes"></custom-elements></cant-skip> <div><input autofocus/></div> <div><source muted/></div> <select><option value="a"${$.maybe_selected($$payload, 'a')}>a</option></select> <img src="..." alt="" loading="lazy"/> <div><img src="..." alt="" loading="lazy"/></div>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/state-proxy-literal/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/state-proxy-literal/_expected/server/index.svelte.js
index c2736b0f43..2c66dc5759 100644
--- a/packages/svelte/tests/snapshot/samples/state-proxy-literal/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/state-proxy-literal/_expected/server/index.svelte.js
@@ -11,5 +11,5 @@ export default function State_proxy_literal($$payload) {
 		tpl = ``;
 	}
 
-	$$payload.out.push(`<input${$.attr('value', str)}/> <input${$.attr('value', tpl)}/> <button>reset</button>`);
+	$$payload.push(`<input${$.attr('value', str)}/> <input${$.attr('value', tpl)}/> <button>reset</button>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/tests/snapshot/samples/text-nodes-deriveds/_expected/server/index.svelte.js b/packages/svelte/tests/snapshot/samples/text-nodes-deriveds/_expected/server/index.svelte.js
index f7dc586026..1ed2b812db 100644
--- a/packages/svelte/tests/snapshot/samples/text-nodes-deriveds/_expected/server/index.svelte.js
+++ b/packages/svelte/tests/snapshot/samples/text-nodes-deriveds/_expected/server/index.svelte.js
@@ -12,5 +12,5 @@ export default function Text_nodes_deriveds($$payload) {
 		return count2;
 	}
 
-	$$payload.out.push(`<p>${$.escape(text1())}${$.escape(text2())}</p>`);
+	$$payload.push(`<p>${$.escape(text1())}${$.escape(text2())}</p>`);
 }
\ No newline at end of file
diff --git a/packages/svelte/types/index.d.ts b/packages/svelte/types/index.d.ts
index 9888de59b2..2c015b5a10 100644
--- a/packages/svelte/types/index.d.ts
+++ b/packages/svelte/types/index.d.ts
@@ -2493,7 +2493,7 @@ declare module 'svelte/server' {
 					}
 				]
 	): RenderOutput;
-	interface RenderOutput {
+	interface SyncRenderOutput {
 		/** HTML that goes into the `<head>` */
 		head: string;
 		/** @deprecated use `body` instead */
@@ -2502,6 +2502,8 @@ declare module 'svelte/server' {
 		body: string;
 	}
 
+	type RenderOutput = SyncRenderOutput & PromiseLike<SyncRenderOutput>;
+
 	export {};
 }
 
diff --git a/playgrounds/sandbox/package.json b/playgrounds/sandbox/package.json
index 8100084832..a5a28879e0 100644
--- a/playgrounds/sandbox/package.json
+++ b/playgrounds/sandbox/package.json
@@ -12,7 +12,8 @@
     "preview": "vite preview",
     "download": "node scripts/download.js",
     "hash": "node scripts/hash.js",
-    "create-test": "node scripts/create-test.js"
+    "create-test": "node scripts/create-test.js",
+    "start": "node run.js"
   },
   "devDependencies": {
     "@sveltejs/vite-plugin-svelte": "^4.0.0-next.6",