diff --git a/ui-svelte/src/App.svelte b/ui-svelte/src/App.svelte
index 4ba3b478..895a057f 100644
--- a/ui-svelte/src/App.svelte
+++ b/ui-svelte/src/App.svelte
@@ -13,6 +13,7 @@
   import { enableAPIEvents, checkPerformanceEnabled } from "./stores/api";
   import { initScreenWidth, initSystemThemeListener, isDarkMode, appTitle, connectionState } from "./stores/theme";
   import { currentRoute } from "./stores/route";
+  import { selectedPlaygroundTab, playgroundTabs } from "./stores/playground";
 
   const routes = {
     "/": PlaygroundStub,
@@ -31,7 +32,13 @@
     "/performance": "Performance",
   };
 
-  let sectionTitle = $derived(routeTitles[$currentRoute] ?? "Playground");
+  let sectionTitle = $derived.by(() => {
+    if ($currentRoute === "/") {
+      const tab = playgroundTabs.find((t) => t.id === $selectedPlaygroundTab);
+      return `Playground / ${tab?.label ?? ""}`;
+    }
+    return routeTitles[$currentRoute] ?? "Playground";
+  });
 
   function handleRouteLoaded(event: { detail: { route: string | RegExp } }) {
     const route = event.detail.route;
diff --git a/ui-svelte/src/components/AppSidebar.svelte b/ui-svelte/src/components/AppSidebar.svelte
index 3e9f56db..356981f7 100644
--- a/ui-svelte/src/components/AppSidebar.svelte
+++ b/ui-svelte/src/components/AppSidebar.svelte
@@ -1,12 +1,14 @@
 <script lang="ts">
   import { link } from "svelte-spa-router";
-  import { House, Boxes, Activity, ScrollText, Gauge, Sun, Moon, Monitor } from "@lucide/svelte";
+  import { House, Boxes, Activity, ScrollText, Gauge, Sun, Moon, Monitor, ChevronRight } from "@lucide/svelte";
   import * as Sidebar from "$lib/components/ui/sidebar/index.js";
+  import * as Collapsible from "$lib/components/ui/collapsible/index.js";
   import { Button } from "$lib/components/ui/button/index.js";
   import { toggleTheme, themeMode, appTitle } from "../stores/theme";
   import { currentRoute } from "../stores/route";
   import { playgroundActivity } from "../stores/playgroundActivity";
   import { performanceEnabled } from "../stores/api";
+  import { selectedPlaygroundTab, playgroundTabs, playgroundMenuOpen } from "../stores/playground";
   import ConnectionStatus from "./ConnectionStatus.svelte";
 
   function handleTitleChange(newTitle: string): void {
@@ -55,16 +57,51 @@
   <Sidebar.Content>
     <Sidebar.Group>
       <Sidebar.GroupContent>
-        <Sidebar.Menu>
+        <Sidebar.Menu class="gap-1">
           <Sidebar.MenuItem>
-            <Sidebar.MenuButton isActive={isActive("/", $currentRoute)} tooltipContent="Playground">
-              {#snippet child({ props })}
-                <a href="/" use:link {...props}>
-                  <House />
-                  <span class={$playgroundActivity ? "activity-link" : ""}>Playground</span>
-                </a>
-              {/snippet}
-            </Sidebar.MenuButton>
+            <Collapsible.Root
+              open={$playgroundMenuOpen}
+              onOpenChange={(v) => playgroundMenuOpen.set(v)}
+              class="gap-0"
+            >
+              <Collapsible.Trigger>
+                {#snippet child({ props })}
+                  <Sidebar.MenuButton
+                    {...props}
+                    isActive={isActive("/", $currentRoute)}
+                    tooltipContent="Playground"
+                  >
+                    <House />
+                    <span class={$playgroundActivity ? "activity-link" : ""}>Playground</span>
+                    <ChevronRight
+                      class="ml-auto transition-transform duration-200 {$playgroundMenuOpen ? 'rotate-90' : ''}"
+                    />
+                  </Sidebar.MenuButton>
+                {/snippet}
+              </Collapsible.Trigger>
+              <Collapsible.Content>
+                <Sidebar.MenuSub>
+                  {#each playgroundTabs as tab (tab.id)}
+                    <Sidebar.MenuSubItem>
+                      <Sidebar.MenuSubButton
+                        isActive={isActive("/", $currentRoute) && $selectedPlaygroundTab === tab.id}
+                      >
+                        {#snippet child({ props })}
+                          <a
+                            href="/"
+                            use:link
+                            {...props}
+                            onclick={() => selectedPlaygroundTab.set(tab.id)}
+                          >
+                            <span>{tab.label}</span>
+                          </a>
+                        {/snippet}
+                      </Sidebar.MenuSubButton>
+                    </Sidebar.MenuSubItem>
+                  {/each}
+                </Sidebar.MenuSub>
+              </Collapsible.Content>
+            </Collapsible.Root>
           </Sidebar.MenuItem>
 
           <Sidebar.MenuItem>
diff --git a/ui-svelte/src/lib/components/ui/collapsible/collapsible-content.svelte b/ui-svelte/src/lib/components/ui/collapsible/collapsible-content.svelte
new file mode 100644
index 00000000..076f6ba6
--- /dev/null
+++ b/ui-svelte/src/lib/components/ui/collapsible/collapsible-content.svelte
@@ -0,0 +1,19 @@
+<script lang="ts">
+	import { Collapsible as CollapsiblePrimitive } from "bits-ui";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: CollapsiblePrimitive.ContentProps = $props();
+</script>
+
+<CollapsiblePrimitive.Content
+	bind:ref
+	data-slot="collapsible-content"
+	class={className}
+	{...restProps}
+>
+	{@render children?.()}
+</CollapsiblePrimitive.Content>
diff --git a/ui-svelte/src/lib/components/ui/collapsible/collapsible-trigger.svelte b/ui-svelte/src/lib/components/ui/collapsible/collapsible-trigger.svelte
new file mode 100644
index 00000000..5f0f915f
--- /dev/null
+++ b/ui-svelte/src/lib/components/ui/collapsible/collapsible-trigger.svelte
@@ -0,0 +1,19 @@
+<script lang="ts">
+	import { Collapsible as CollapsiblePrimitive } from "bits-ui";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: CollapsiblePrimitive.TriggerProps = $props();
+</script>
+
+<CollapsiblePrimitive.Trigger
+	bind:ref
+	data-slot="collapsible-trigger"
+	class={className}
+	{...restProps}
+>
+	{@render children?.()}
+</CollapsiblePrimitive.Trigger>
diff --git a/ui-svelte/src/lib/components/ui/collapsible/collapsible.svelte b/ui-svelte/src/lib/components/ui/collapsible/collapsible.svelte
new file mode 100644
index 00000000..7ad7e756
--- /dev/null
+++ b/ui-svelte/src/lib/components/ui/collapsible/collapsible.svelte
@@ -0,0 +1,19 @@
+<script lang="ts">
+	import { Collapsible as CollapsiblePrimitive } from "bits-ui";
+
+	let {
+		ref = $bindable(null),
+		class: className,
+		children,
+		...restProps
+	}: CollapsiblePrimitive.RootProps = $props();
+</script>
+
+<CollapsiblePrimitive.Root
+	bind:ref
+	data-slot="collapsible"
+	class={className}
+	{...restProps}
+>
+	{@render children?.()}
+</CollapsiblePrimitive.Root>
diff --git a/ui-svelte/src/lib/components/ui/collapsible/index.ts b/ui-svelte/src/lib/components/ui/collapsible/index.ts
new file mode 100644
index 00000000..60c0938c
--- /dev/null
+++ b/ui-svelte/src/lib/components/ui/collapsible/index.ts
@@ -0,0 +1,13 @@
+import Root from "./collapsible.svelte";
+import Trigger from "./collapsible-trigger.svelte";
+import Content from "./collapsible-content.svelte";
+
+export {
+	Root,
+	Trigger,
+	Content,
+	//
+	Root as Collapsible,
+	Trigger as CollapsibleTrigger,
+	Content as CollapsibleContent,
+};
diff --git a/ui-svelte/src/lib/components/ui/sidebar/sidebar-menu-button.svelte b/ui-svelte/src/lib/components/ui/sidebar/sidebar-menu-button.svelte
index e0c9c25e..d8e7f78e 100644
--- a/ui-svelte/src/lib/components/ui/sidebar/sidebar-menu-button.svelte
+++ b/ui-svelte/src/lib/components/ui/sidebar/sidebar-menu-button.svelte
@@ -2,7 +2,7 @@
 	import { tv, type VariantProps } from "tailwind-variants";
 
 	export const sidebarMenuButtonVariants = tv({
-		base: "ring-sidebar-ring hover:bg-sidebar-accent hover:text-sidebar-accent-foreground active:bg-sidebar-accent active:text-sidebar-accent-foreground data-active:bg-sidebar-accent data-active:text-sidebar-accent-foreground data-open:hover:bg-sidebar-accent data-open:hover:text-sidebar-accent-foreground gap-2 rounded-md p-2 text-left text-sm transition-[width,height,padding] group-has-data-[sidebar=menu-action]/menu-item:pr-8 group-data-[collapsible=icon]:size-8! group-data-[collapsible=icon]:p-2! focus-visible:ring-2 data-active:font-medium peer/menu-button group/menu-button flex w-full items-center overflow-hidden outline-hidden disabled:pointer-events-none disabled:opacity-50 aria-disabled:pointer-events-none aria-disabled:opacity-50 [&_svg]:size-4 [&_svg]:shrink-0 [&>span:last-child]:truncate",
+		base: "ring-sidebar-ring hover:bg-sidebar-accent hover:text-sidebar-accent-foreground active:bg-sidebar-accent active:text-sidebar-accent-foreground data-active:font-medium data-active:text-sidebar-accent-foreground data-open:hover:bg-sidebar-accent data-open:hover:text-sidebar-accent-foreground gap-2 rounded-md p-2 text-left text-sm transition-[width,height,padding] group-has-data-[sidebar=menu-action]/menu-item:pr-8 group-data-[collapsible=icon]:size-8! group-data-[collapsible=icon]:p-2! focus-visible:ring-2 peer/menu-button group/menu-button flex w-full items-center overflow-hidden outline-hidden disabled:pointer-events-none disabled:opacity-50 aria-disabled:pointer-events-none aria-disabled:opacity-50 [&_svg]:size-4 [&_svg]:shrink-0 [&>span:last-child]:truncate",
 		variants: {
 			variant: {
 				default: "hover:bg-sidebar-accent hover:text-sidebar-accent-foreground",
diff --git a/ui-svelte/src/lib/components/ui/sidebar/sidebar-menu-sub-button.svelte b/ui-svelte/src/lib/components/ui/sidebar/sidebar-menu-sub-button.svelte
index 09ff228f..4a805973 100644
--- a/ui-svelte/src/lib/components/ui/sidebar/sidebar-menu-sub-button.svelte
+++ b/ui-svelte/src/lib/components/ui/sidebar/sidebar-menu-sub-button.svelte
@@ -19,7 +19,7 @@
 
 	const mergedProps = $derived({
 		class: cn(
-			"text-sidebar-foreground ring-sidebar-ring hover:bg-sidebar-accent hover:text-sidebar-accent-foreground active:bg-sidebar-accent active:text-sidebar-accent-foreground [&>svg]:text-sidebar-accent-foreground data-active:bg-sidebar-accent data-active:text-sidebar-accent-foreground h-7 gap-2 rounded-md px-2 focus-visible:ring-2 data-[size=md]:text-sm data-[size=sm]:text-xs [&>svg]:size-4 flex min-w-0 -translate-x-px items-center overflow-hidden outline-hidden group-data-[collapsible=icon]:hidden disabled:pointer-events-none disabled:opacity-50 aria-disabled:pointer-events-none aria-disabled:opacity-50 [&>span:last-child]:truncate [&>svg]:shrink-0",
+			"text-sidebar-foreground ring-sidebar-ring hover:bg-sidebar-accent hover:text-sidebar-accent-foreground active:bg-sidebar-accent active:text-sidebar-accent-foreground [&>svg]:text-sidebar-accent-foreground data-active:font-medium data-active:text-sidebar-accent-foreground h-7 gap-2 rounded-md px-2 focus-visible:ring-2 data-[size=md]:text-sm data-[size=sm]:text-xs [&>svg]:size-4 flex min-w-0 -translate-x-px items-center overflow-hidden outline-hidden group-data-[collapsible=icon]:hidden disabled:pointer-events-none disabled:opacity-50 aria-disabled:pointer-events-none aria-disabled:opacity-50 [&>span:last-child]:truncate [&>svg]:shrink-0",
 			className
 		),
 		"data-slot": "sidebar-menu-sub-button",
diff --git a/ui-svelte/src/lib/components/ui/sidebar/sidebar.svelte b/ui-svelte/src/lib/components/ui/sidebar/sidebar.svelte
index 9c90d4f8..dc9bf743 100644
--- a/ui-svelte/src/lib/components/ui/sidebar/sidebar.svelte
+++ b/ui-svelte/src/lib/components/ui/sidebar/sidebar.svelte
@@ -25,7 +25,7 @@
 {#if collapsible === "none"}
 	<div
 		class={cn(
-			"bg-sidebar text-sidebar-foreground flex h-full w-(--sidebar-width) flex-col",
+			"bg-background text-sidebar-foreground flex h-full w-(--sidebar-width) flex-col",
 			className
 		)}
 		bind:this={ref}
@@ -44,7 +44,7 @@
 			data-slot="sidebar"
 			data-mobile="true"
 			class={cn(
-				"bg-sidebar text-sidebar-foreground w-(--sidebar-width) p-0 [&>button]:hidden",
+				"bg-background text-sidebar-foreground w-(--sidebar-width) p-0 [&>button]:hidden",
 				className
 			)}
 			style="--sidebar-width: {SIDEBAR_WIDTH_MOBILE};"
@@ -99,7 +99,7 @@
 			<div
 				data-sidebar="sidebar"
 				data-slot="sidebar-inner"
-				class="bg-sidebar group-data-[variant=floating]:ring-sidebar-border group-data-[variant=floating]:rounded-lg group-data-[variant=floating]:shadow-sm group-data-[variant=floating]:ring-1 flex size-full flex-col"
+				class="bg-background group-data-[variant=floating]:ring-sidebar-border group-data-[variant=floating]:rounded-lg group-data-[variant=floating]:shadow-sm group-data-[variant=floating]:ring-1 flex size-full flex-col"
 			>
 				{@render children?.()}
 			</div>
diff --git a/ui-svelte/src/routes/Playground.svelte b/ui-svelte/src/routes/Playground.svelte
index b4ba7b47..edfd2c24 100644
--- a/ui-svelte/src/routes/Playground.svelte
+++ b/ui-svelte/src/routes/Playground.svelte
@@ -1,5 +1,4 @@
 <script lang="ts">
-  import { persistentStore } from "../stores/persistent";
   import ChatInterface from "../components/playground/ChatInterface.svelte";
   import ImageInterface from "../components/playground/ImageInterface.svelte";
   import AudioInterface from "../components/playground/AudioInterface.svelte";
@@ -7,52 +6,28 @@
   import RerankInterface from "../components/playground/RerankInterface.svelte";
   import ConcurrencyInterface from "../components/playground/ConcurrencyInterface.svelte";
   import * as Card from "$lib/components/ui/card/index.js";
-  import * as Tabs from "$lib/components/ui/tabs/index.js";
-
-  type Tab = "chat" | "images" | "speech" | "audio" | "rerank" | "concurrency";
-
-  const selectedTabStore = persistentStore<Tab>("playground-selected-tab", "chat");
-
-  const tabs: { id: Tab; label: string }[] = [
-    { id: "chat", label: "Chat" },
-    { id: "images", label: "Images" },
-    { id: "speech", label: "Speech" },
-    { id: "audio", label: "Transcription" },
-    { id: "rerank", label: "Rerank" },
-    { id: "concurrency", label: "Load Test" },
-  ];
+  import { selectedPlaygroundTab } from "../stores/playground";
 </script>
 
 <Card.Root class="flex h-full flex-col gap-0 overflow-hidden p-4">
-  <!-- Tab navigation: triggers update the store; content stays mounted to preserve state -->
-  <div class="mb-4 shrink-0">
-    <Tabs.Root bind:value={() => $selectedTabStore, (v) => selectedTabStore.set(v as Tab)}>
-      <Tabs.List class="h-auto flex-wrap">
-        {#each tabs as tab (tab.id)}
-          <Tabs.Trigger value={tab.id}>{tab.label}</Tabs.Trigger>
-        {/each}
-      </Tabs.List>
-    </Tabs.Root>
-  </div>
-
-  <!-- Tab content (all interfaces stay mounted) -->
+  <!-- Tab content (all interfaces stay mounted); navigation via the sidebar -->
   <div class="relative flex-1 overflow-hidden">
-    <div class="h-full" class:hidden={$selectedTabStore !== "chat"}>
+    <div class="h-full" class:hidden={$selectedPlaygroundTab !== "chat"}>
       <ChatInterface />
     </div>
-    <div class="h-full" class:hidden={$selectedTabStore !== "images"}>
+    <div class="h-full" class:hidden={$selectedPlaygroundTab !== "images"}>
       <ImageInterface />
     </div>
-    <div class="h-full" class:hidden={$selectedTabStore !== "speech"}>
+    <div class="h-full" class:hidden={$selectedPlaygroundTab !== "speech"}>
       <SpeechInterface />
     </div>
-    <div class="h-full" class:hidden={$selectedTabStore !== "audio"}>
+    <div class="h-full" class:hidden={$selectedPlaygroundTab !== "audio"}>
       <AudioInterface />
     </div>
-    <div class="h-full" class:hidden={$selectedTabStore !== "rerank"}>
+    <div class="h-full" class:hidden={$selectedPlaygroundTab !== "rerank"}>
       <RerankInterface />
     </div>
-    <div class="h-full" class:hidden={$selectedTabStore !== "concurrency"}>
+    <div class="h-full" class:hidden={$selectedPlaygroundTab !== "concurrency"}>
       <ConcurrencyInterface />
     </div>
   </div>
diff --git a/ui-svelte/src/stores/playground.ts b/ui-svelte/src/stores/playground.ts
new file mode 100644
index 00000000..3e2b92b3
--- /dev/null
+++ b/ui-svelte/src/stores/playground.ts
@@ -0,0 +1,16 @@
+import { persistentStore } from "./persistent";
+
+export type PlaygroundTab = "chat" | "images" | "speech" | "audio" | "rerank" | "concurrency";
+
+export const playgroundTabs: { id: PlaygroundTab; label: string }[] = [
+  { id: "chat", label: "Chat" },
+  { id: "images", label: "Images" },
+  { id: "speech", label: "Speech" },
+  { id: "audio", label: "Transcription" },
+  { id: "rerank", label: "Rerank" },
+  { id: "concurrency", label: "Load Test" },
+];
+
+export const selectedPlaygroundTab = persistentStore<PlaygroundTab>("playground-selected-tab", "chat");
+
+export const playgroundMenuOpen = persistentStore<boolean>("playground-menu-open", true);