diff --git a/packages/editor/src/lib/Workspace.svelte.ts b/packages/editor/src/lib/Workspace.svelte.ts
index 8a730c23d3..8d6be150f5 100644
--- a/packages/editor/src/lib/Workspace.svelte.ts
+++ b/packages/editor/src/lib/Workspace.svelte.ts
@@ -78,6 +78,7 @@ const default_extensions = [
 interface ExposedCompilerOptions {
 	generate: 'client' | 'server';
 	dev: boolean;
+	modernAst: boolean;
 }
 
 export class Workspace {
@@ -87,7 +88,8 @@ export class Workspace {
 
 	#compiler_options = $state.raw<ExposedCompilerOptions>({
 		generate: 'client',
-		dev: false
+		dev: false,
+		modernAst: true
 	});
 	compiled = $state<Record<string, Compiled>>({});
 
diff --git a/packages/repl/src/lib/Output/AstNode.svelte b/packages/repl/src/lib/Output/AstNode.svelte
index 302721b04f..a1c02e1c80 100644
--- a/packages/repl/src/lib/Output/AstNode.svelte
+++ b/packages/repl/src/lib/Output/AstNode.svelte
@@ -1,55 +1,72 @@
 <script lang="ts">
+	import AstNode from './AstNode.svelte';
 	import { get_repl_context } from '../context';
 	import { tick } from 'svelte';
 	import type { CompileResult } from 'svelte/compiler';
 
 	type Ast = CompileResult['ast'];
 
-	export let key = '';
-	export let value: Ast;
-	export let collapsed = true;
-	export let path_nodes: Ast[] = [];
-	export let autoscroll = true;
+	interface Props {
+		key?: string;
+		value: Ast;
+		collapsed?: boolean;
+		path_nodes?: Ast[];
+		autoscroll?: boolean;
+	}
+
+	let {
+		key = '',
+		value,
+		collapsed = $bindable(true),
+		path_nodes = [],
+		autoscroll = true
+	}: Props = $props();
 
 	const { toggleable } = get_repl_context();
 
-	let list_item_el: HTMLLIElement;
+	let list_item_el = $state() as HTMLLIElement;
 
-	$: is_root = path_nodes[0] === value;
-	$: is_leaf = path_nodes[path_nodes.length - 1] === value;
-	$: is_ast_array = Array.isArray(value);
-	$: is_collapsable = value && typeof value === 'object';
-	$: is_markable =
+	let is_root = $derived(path_nodes[0] === value);
+	let is_leaf = $derived(path_nodes[path_nodes.length - 1] === value);
+	let is_ast_array = $derived(Array.isArray(value));
+	let is_collapsable = $derived(value && typeof value === 'object');
+	let is_markable = $derived(
 		is_collapsable &&
-		'start' in value &&
-		'end' in value &&
-		typeof value.start === 'number' &&
-		typeof value.end === 'number';
-	$: key_text = key ? `${key}:` : '';
+			'start' in value &&
+			'end' in value &&
+			typeof value.start === 'number' &&
+			typeof value.end === 'number'
+	);
+	let key_text = $derived(key ? `${key}:` : '');
+
+	let preview_text = $state('');
 
-	let preview_text = '';
-	$: {
-		if (!is_collapsable || !collapsed) break $;
+	$effect(() => {
+		if (!is_collapsable || !collapsed) return;
 
 		if (is_ast_array) {
-			if (!('length' in value)) break $;
+			if (!('length' in value)) return;
 
 			preview_text = `[ ${value.length} element${value.length === 1 ? '' : 's'} ]`;
 		} else {
 			preview_text = `{ ${Object.keys(value).join(', ')} }`;
 		}
-	}
-
-	$: collapsed = !path_nodes.includes(value);
-
-	$: if (autoscroll && is_leaf && !$toggleable) {
-		// wait for all nodes to render before scroll
-		tick().then(() => {
-			if (list_item_el) {
-				list_item_el.scrollIntoView();
-			}
-		});
-	}
+	});
+
+	$effect(() => {
+		collapsed = !path_nodes.includes(value);
+	});
+
+	$effect(() => {
+		if (autoscroll && is_leaf && !$toggleable) {
+			// wait for all nodes to render before scroll
+			tick().then(() => {
+				if (list_item_el) {
+					list_item_el.scrollIntoView();
+				}
+			});
+		}
+	});
 
 	function handle_mark_text(e: MouseEvent | FocusEvent) {
 		if (is_markable) {
@@ -79,12 +96,12 @@
 <li
 	bind:this={list_item_el}
 	class:marked={!is_root && is_leaf}
-	on:mouseover={handle_mark_text}
-	on:focus={handle_mark_text}
-	on:mouseleave={handle_unmark_text}
+	onmouseover={handle_mark_text}
+	onfocus={handle_mark_text}
+	onmouseleave={handle_unmark_text}
 >
 	{#if !is_root && is_collapsable}
-		<button class="ast-toggle" class:open={!collapsed} on:click={() => (collapsed = !collapsed)}>
+		<button class="ast-toggle" class:open={!collapsed} onclick={() => (collapsed = !collapsed)}>
 			{key_text}
 		</button>
 	{:else if key_text}
@@ -92,14 +109,14 @@
 	{/if}
 	{#if is_collapsable}
 		{#if collapsed && !is_root}
-			<button class="preview" on:click={() => (collapsed = !collapsed)}>
+			<button class="preview" onclick={() => (collapsed = !collapsed)}>
 				{preview_text}
 			</button>
 		{:else}
 			<span>{is_ast_array ? '[' : '{'}</span>
 			<ul>
 				{#each Object.entries(value) as [k, v]}
-					<svelte:self key={is_ast_array ? '' : k} value={v} {path_nodes} {autoscroll} />
+					<AstNode key={is_ast_array ? '' : k} value={v} {path_nodes} {autoscroll} />
 				{/each}
 			</ul>
 			<span>{is_ast_array ? ']' : '}'}</span>
diff --git a/packages/repl/src/lib/Output/AstView.svelte b/packages/repl/src/lib/Output/AstView.svelte
index ae469f1cea..b1cacf4af3 100644
--- a/packages/repl/src/lib/Output/AstView.svelte
+++ b/packages/repl/src/lib/Output/AstView.svelte
@@ -1,12 +1,19 @@
 <script lang="ts">
+	import { Checkbox } from '@sveltejs/site-kit/components';
 	import Message from '../Message.svelte';
 	import AstNode from './AstNode.svelte';
 	import type { CompileResult } from 'svelte/compiler';
+	import type { Workspace } from 'editor';
 
 	type Ast = CompileResult['ast'];
 
-	export let ast: Ast;
-	export let autoscroll = true;
+	interface Props {
+		workspace: Workspace;
+		ast: Ast;
+		autoscroll?: boolean;
+	}
+
+	let { workspace, ast, autoscroll = true }: Props = $props();
 
 	// $cursor_index may go over the max since ast computation is usually slower.
 	// clamping this helps prevent the collapse view flashing
@@ -14,7 +21,7 @@
 	let max_cursor_index = 0;
 	// $: max_cursor_index = !ast ? $cursorIndex : Math.min($cursorIndex, get_ast_max_end(ast));
 
-	$: path_nodes = find_deepest_path(max_cursor_index, [ast]) || [];
+	let path_nodes = $derived(find_deepest_path(max_cursor_index, [ast]) || []);
 
 	function find_deepest_path(cursor: number, paths: Ast[]): Ast[] | undefined {
 		const value = paths[paths.length - 1];
@@ -65,7 +72,19 @@
 			{/if}
 		</code>
 	</pre>
+
 	<Message kind="info">The AST is not public API and may change at any point in time</Message>
+
+	<label>
+		modern
+
+		<Checkbox
+			checked={workspace.compiler_options.modernAst}
+			onchange={(modernAst) => {
+				workspace.update_compiler_options({ modernAst });
+			}}
+		/>
+	</label>
 </div>
 
 <style>
@@ -99,4 +118,14 @@
 		margin: 0;
 		list-style-type: none;
 	}
+
+	label {
+		position: absolute;
+		top: 1rem;
+		right: 1rem;
+		display: inline-flex;
+		gap: 1rem;
+		align-items: center;
+		font: var(--sk-font-ui-small);
+	}
 </style>
diff --git a/packages/repl/src/lib/Output/Output.svelte b/packages/repl/src/lib/Output/Output.svelte
index 809498ecd2..4b353c6f13 100644
--- a/packages/repl/src/lib/Output/Output.svelte
+++ b/packages/repl/src/lib/Output/Output.svelte
@@ -81,8 +81,6 @@
 			css_workspace.update_file(css);
 		});
 	});
-
-	let ast = $derived(current?.result?.ast);
 </script>
 
 <div class="view-toggle">
@@ -132,9 +130,9 @@
 </div>
 
 <!-- ast output -->
-{#if ast}
+{#if current?.result}
 	<div class="tab-content" class:visible={!is_markdown && view === 'ast'}>
-		<AstView {ast} autoscroll={!is_markdown && view === 'ast'} />
+		<AstView {workspace} ast={current.result.ast} autoscroll={!is_markdown && view === 'ast'} />
 	</div>
 {/if}
 
diff --git a/packages/site-kit/src/lib/components/Checkbox.svelte b/packages/site-kit/src/lib/components/Checkbox.svelte
index 34033cbf24..6e54349421 100644
--- a/packages/site-kit/src/lib/components/Checkbox.svelte
+++ b/packages/site-kit/src/lib/components/Checkbox.svelte
@@ -12,8 +12,7 @@
 		/* display: block; */
 		position: relative;
 		height: 1em;
-		width: calc(100% - 0.6em);
-		max-width: 2em;
+		width: 2em;
 		top: -2px;
 		border-radius: 0.5em;
 		-webkit-appearance: none;