ui : render conversation tab bar in chat layout

Desktop-only tab bar above the chat screen, one tab per open
conversation or new-chat tab. The active tab follows the route id;
clicking navigates, middle-click or the close button closes (switching
to the left neighbor), and a trailing + starts a new chat. Tabs appear
only on chat-id routes; the bare #/ new-chat view has none. The bare
route stays put unless a prompt/model deep-link routes it to a new-chat
tab.

tools/ui/src/lib/components/app/chat/ChatTabs/ChatTabs.svelte

@@ -0,0 +1,109 @@
+<script lang="ts">
+	import { Loader2, Plus, SquarePen, X } from '@lucide/svelte';
+	import { page } from '$app/state';
+	import * as Tooltip from '$lib/components/ui/tooltip';
+	import { cn } from '$lib/components/ui/utils';
+	import { chatStore, conversationsStore, tabsStore } from '$lib/stores';
+
+	let activeId = $derived(page.params.id);
+
+	let tabs = $derived(
+		tabsStore.openTabs.map((id) => ({
+			id,
+			isNewChat: conversationsStore.isTemporaryConversation(id),
+			name:
+				conversationsStore.conversations.find((c) => c.id === id)?.name ??
+				(conversationsStore.isTemporaryConversation(id) ? 'New chat' : 'Chat')
+		}))
+	);
+
+	let loadingIds = $derived(new Set(chatStore.getAllLoadingChats()));
+
+	function handleClose(id: string) {
+		void tabsStore.close(id, activeId ?? null);
+	}
+
+	function handleAuxClick(id: string, event: MouseEvent) {
+		// middle-click closes, like browser tabs
+		if (event.button === 1) {
+			event.preventDefault();
+			handleClose(id);
+		}
+	}
+</script>
+
+<nav
+	class="sticky pl-1 top-0 pt-3.5 z-10 hidden md:block transition-colors ease-in-out"
+	aria-label="Open conversations"
+>
+	<div class="flex h-10 items-center gap-1.25 overflow-x-auto px-2">
+		{#each tabs as tab (tab.id)}
+			{@const isActive = tab.id === activeId}
+			{@const isLoading = loadingIds.has(tab.id)}
+
+			<div
+				class={cn(
+					'group flex h-8 max-w-52 min-w-0 shrink-0 items-center gap-1 rounded-lg pr-1 pl-3 text-sm transition-colors backdrop-blur-xl',
+					isActive
+						? 'bg-foreground/8 text-foreground'
+						: 'text-muted-foreground hover:bg-foreground/5 hover:text-foreground'
+				)}
+			>
+				<button
+					class="flex min-w-0 flex-1 cursor-pointer items-center gap-2"
+					onclick={() => tabsStore.activate(tab.id)}
+					onauxclick={(e) => handleAuxClick(tab.id, e)}
+					aria-current={isActive ? 'page' : undefined}
+				>
+					{#if isLoading}
+						<Loader2 class="h-3.5 w-3.5 shrink-0 animate-spin" />
+					{:else if tab.isNewChat}
+						<SquarePen class="h-3.5 w-3.5 shrink-0" />
+					{/if}
+
+					<span class="truncate">{tab.name}</span>
+				</button>
+
+				<Tooltip.Root>
+					<Tooltip.Trigger>
+						{#snippet child({ props })}
+							<button
+								{...props}
+								class={cn(
+									'flex h-5 w-5 shrink-0 cursor-pointer items-center justify-center rounded-sm text-muted-foreground transition-opacity hover:bg-foreground/10 hover:text-foreground'
+								)}
+								onclick={() => handleClose(tab.id)}
+								aria-label="Close tab"
+							>
+								<X class="h-3.5 w-3.5" />
+							</button>
+						{/snippet}
+					</Tooltip.Trigger>
+
+					<Tooltip.Content>
+						<p>Close tab</p>
+					</Tooltip.Content>
+				</Tooltip.Root>
+			</div>
+		{/each}
+
+		<Tooltip.Root>
+			<Tooltip.Trigger>
+				{#snippet child({ props })}
+					<button
+						{...props}
+						class="backdrop-blur-lg flex h-8 w-8 shrink-0 cursor-pointer items-center justify-center rounded-md text-muted-foreground transition-colors hover:bg-foreground/5 hover:text-foreground"
+						onclick={() => conversationsStore.openNewChatTab()}
+						aria-label="New chat"
+					>
+						<Plus class="h-4 w-4" />
+					</button>
+				{/snippet}
+			</Tooltip.Trigger>
+
+			<Tooltip.Content>
+				<p>New chat</p>
+			</Tooltip.Content>
+		</Tooltip.Root>
+	</div>
+</nav>

tools/ui/src/lib/components/app/chat/index.ts

@@ -686,6 +686,18 @@ export { default as ChatMessageSystem } from './ChatMessages/ChatMessage/ChatMes
  */
 export { default as ChatScreen } from './ChatScreen/ChatScreen.svelte';
 
+/**
+ * **ChatTabs** - Browser-style tab bar for open conversations
+ *
+ * Horizontal strip of tabs rendered above ChatScreen in the chat layout,
+ * one per conversation tracked by tabsStore. The active tab follows the
+ * route's conversation id; clicking a tab navigates to it, middle-click or
+ * the close button closes it (switching to the left neighbor when closing
+ * the active tab), and a trailing "+" button starts a new chat. Shows a
+ * spinner on tabs with a running generation. Desktop-only.
+ */
+export { default as ChatTabs } from './ChatTabs/ChatTabs.svelte';
+
 /**
  * Visual overlay displayed when user drags files over the chat screen.
  * Shows drop zone indicator to guide users where to release files.

tools/ui/src/routes/(chat)/+layout.svelte

@@ -1,12 +1,34 @@
 <script lang="ts">
 	import { page } from '$app/state';
-	import { ChatScreen } from '$lib/components/app';
+	import { ChatScreen, ChatTabs } from '$lib/components/app';
+	import { conversationsStore, tabsStore } from '$lib/stores';
 
 	let { children } = $props();
 
-	let showCenteredEmpty = $derived(!page.params.id);
+	// the new-chat screen is a temporary conversation (unsaved) or the bare `#/` route
+	let showCenteredEmpty = $derived(
+		page.params.id ? conversationsStore.isTemporaryConversation(page.params.id) : true
+	);
+
+	// tabs appear only on chat-id routes; the bare `#/` new-chat view has none
+	let showTabs = $derived(!!page.params.id);
+
+	// any navigation to a conversation or new-chat tab opens a tab for it
+	$effect(() => {
+		const id = page.params.id;
+
+		if (id) {
+			tabsStore.syncWithRoute(id);
+		}
+	});
 </script>
 
-<ChatScreen {showCenteredEmpty} />
+<div class={showTabs ? 'md:[--chat-tabs-height:2.5rem]' : ''}>
+	{#if showTabs}
+		<ChatTabs />
+	{/if}
+
+	<ChatScreen {showCenteredEmpty} />
+</div>
 
 {@render children?.()}

tools/ui/src/routes/(chat)/+page.svelte

@@ -1,79 +1,11 @@
 <script lang="ts">
-	import { replaceState } from '$app/navigation';
 	import { page } from '$app/state';
-	import { DialogModelNotAvailable } from '$lib/components/app';
 	import { APP_NAME, URL_PARAMS } from '$lib/constants';
-	import { chatStore, conversationsStore, modelsStore, serverStore } from '$lib/stores';
+	import { chatStore, conversationsStore, modelsStore } from '$lib/stores';
 	import { onMount } from 'svelte';
 
 	let qParam = $derived(page.url.searchParams.get(URL_PARAMS.QUERY));
 	let modelParam = $derived(page.url.searchParams.get(URL_PARAMS.MODEL));
-	let newChatParam = $derived(page.url.searchParams.get(URL_PARAMS.NEW_CHAT));
-	let loadParam = $derived(page.url.searchParams.get(URL_PARAMS.LOAD));
-
-	// Dialog state for model not available error
-	let showModelNotAvailable = $state(false);
-	let requestedModelName = $state('');
-	let availableModelNames = $derived(modelsStore.models.map((m) => m.model));
-
-	/**
-	 * Clear URL params after message is sent to prevent re-sending on refresh
-	 */
-	function clearUrlParams() {
-		const url = new URL(page.url);
-
-		url.searchParams.delete(URL_PARAMS.QUERY);
-		url.searchParams.delete(URL_PARAMS.MODEL);
-		url.searchParams.delete(URL_PARAMS.LOAD);
-		url.searchParams.delete(URL_PARAMS.NEW_CHAT);
-
-		replaceState(url.toString(), {});
-	}
-
-	async function handleUrlParams() {
-		await modelsStore.fetch();
-
-		if (modelParam) {
-			const model = modelsStore.findModelByName(modelParam);
-
-			if (model) {
-				try {
-					await modelsStore.selectModelById(model.id);
-
-					// with ?load=true, start loading right away so the model is ready sooner;
-					// not awaited, so the UI stays usable during the load
-					if (
-						loadParam === 'true' &&
-						serverStore.isRouterMode &&
-						!modelsStore.isModelLoaded(model.id)
-					) {
-						modelsStore.status
-							.load(model.id)
-							.catch((error) => console.error('Failed to load model:', error));
-					}
-				} catch (error) {
-					console.error('Failed to select model:', error);
-					requestedModelName = modelParam;
-					showModelNotAvailable = true;
-
-					return;
-				}
-			} else {
-				requestedModelName = modelParam;
-				showModelNotAvailable = true;
-
-				return;
-			}
-		}
-
-		// Handle ?q= parameter - create new conversation and send message
-		if (qParam !== null) {
-			await conversationsStore.createConversation();
-			clearUrlParams();
-		} else if (modelParam || newChatParam === 'true') {
-			clearUrlParams();
-		}
-	}
 
 	onMount(async () => {
 		if (!conversationsStore.isInitialized) {
@@ -85,8 +17,10 @@
 
 		await modelsStore.fetch();
 
-		if (qParam !== null || modelParam !== null || newChatParam === 'true') {
-			await handleUrlParams();
+		// a prompt/model deep-link routes to a new-chat tab, which sends it;
+		// otherwise `#/` is a plain new-chat view with no tabs
+		if (qParam !== null || modelParam !== null) {
+			await conversationsStore.openNewChatTab();
 		}
 
 		await modelsStore.ensureFirstModelSelected();
@@ -96,9 +30,3 @@
 <svelte:head>
 	<title>{APP_NAME}</title>
 </svelte:head>
-
-<DialogModelNotAvailable
-	bind:open={showModelNotAvailable}
-	modelName={requestedModelName}
-	availableModels={availableModelNames}
-/>