diff --git a/src/app/[locale]/layout.tsx b/src/app/[locale]/layout.tsx
index 81df8bb..2a20c72 100644
--- a/src/app/[locale]/layout.tsx
+++ b/src/app/[locale]/layout.tsx
@@ -44,7 +44,7 @@ export default async function RootLayout(props: {
         <Providers locale={locale} messages={messages} session={session}>
           <Navbar />
 
-          <main className="flex-1 pt-20 flex flex-col">{props.children}</main>
+          <main className="flex-1 pt-[var(--header-height)] flex flex-col">{props.children}</main>
 
           <Footer />
         </Providers>
diff --git a/src/app/[locale]/page.tsx b/src/app/[locale]/page.tsx
index 523ded9..b7f2185 100644
--- a/src/app/[locale]/page.tsx
+++ b/src/app/[locale]/page.tsx
@@ -1,17 +1,85 @@
+'use client';
+
+import { useSession } from 'next-auth/react';
 import { useTranslations } from 'next-intl';
+import { useEffect, useRef, useState, useSyncExternalStore } from 'react';
+import ChatUI from '@/components/chat/ChatUI';
+import { ModelInfo } from '@/types/chat-api';
+import { signIn } from 'next-auth/react';
+
+// ---------------------------------------------------------------------------
+// localStorage store for preferred model.
+// getServerSnapshot always returns null → SSR and first client render agree.
+// After hydration React switches to getSnapshot and reads the real value.
+// ---------------------------------------------------------------------------
+const STORAGE_KEY = 'preferred_model';
+
+function subscribeStorage(cb: () => void) {
+  window.addEventListener('storage', cb);
+  return () => window.removeEventListener('storage', cb);
+}
+const getStorageSnapshot = () => localStorage.getItem(STORAGE_KEY);
+const getStorageServerSnapshot = (): null => null;
+
+// ---------------------------------------------------------------------------
 
 export default function Home() {
+  const { data: session, status } = useSession();
   const t = useTranslations('home');
+  const isLoggedIn = status === 'authenticated';
+
+  const [models, setModels] = useState<ModelInfo[]>([]);
+
+  const savedModel = useSyncExternalStore(
+    subscribeStorage,
+    getStorageSnapshot,
+    getStorageServerSnapshot,
+  );
+
+  const [overrideModel, setOverrideModel] = useState<string | null>(null);
+
+  const selectedModel = overrideModel ?? savedModel ?? models[0]?.name ?? null;
+
+  const isFirstRender = useRef(true);
+  useEffect(() => {
+    if (isFirstRender.current) {
+      isFirstRender.current = false;
+      return;
+    }
+    if (overrideModel) {
+      localStorage.setItem(STORAGE_KEY, overrideModel);
+    }
+  }, [overrideModel]);
+
+  useEffect(() => {
+    if (!session?.accessToken) return;
+    fetch(process.env.NEXT_PUBLIC_API_URL + '/models', {
+      headers: { Authorization: `Bearer ${session.accessToken}` },
+    })
+      .then((res) => res.json())
+      .then((result: { models?: ModelInfo[] }) => {
+        setModels(result?.models ?? []);
+      });
+  }, [session]);
+
+  if (!isLoggedIn) {
+    return (
+      <div className="flex flex-col items-center justify-center">
+        <h1 className="text-5xl font-bold text-cyan-400">{t('name')}</h1>
+        <p className="mt-4 text-gray-400">{t('welcome')}</p>
+        <button className="mt-6 px-6 py-3 bg-cyan-500 rounded-xl" onClick={() => signIn('keycloak')}>
+          {t('start')}
+        </button>
+      </div>
+    );
+  }
 
   return (
-    <div className="min-h-screen flex flex-col items-center justify-center">
-      <h1 className="text-5xl font-bold text-cyan-400">{t('name')}</h1>
-
-      <p className="mt-4 text-gray-400">{t('welcome')}</p>
-
-      <button className="mt-6 px-6 py-3 bg-cyan-500 hover:bg-cyan-600 rounded-xl">
-        {t('start')}
-      </button>
-    </div>
+    <ChatUI
+      session={session}
+      models={models}
+      selectedModel={selectedModel}
+      setSelectedModel={setOverrideModel}
+    />
   );
 }
diff --git a/src/components/chat/ChatUI.tsx b/src/components/chat/ChatUI.tsx
new file mode 100644
index 0000000..8567785
--- /dev/null
+++ b/src/components/chat/ChatUI.tsx
@@ -0,0 +1,100 @@
+'use client';
+
+import { useState } from 'react';
+import ModelSelect from './ModelSelect';
+import Sidebar from '../Sidebar';
+import { SIDEBAR_PANELS } from './chat.panels';
+import { Session } from 'next-auth';
+import { Message, ModelInfo } from '@/types/chat-api';
+
+type Props = {
+  session: Session;
+  models: ModelInfo[];
+  selectedModel: string | null;
+  setSelectedModel: (v: string) => void;
+};
+
+export default function ChatUI({
+  session,
+  models,
+  selectedModel,
+  setSelectedModel,
+}: Props) {
+  const [messages, setMessages] = useState<Message[]>([]);
+  const [input, setInput] = useState('');
+  const [loading, setLoading] = useState(false);
+
+  const sendMessage = async () => {
+    if (!input.trim() || !selectedModel) return;
+    const userMessage = { role: 'user' as const, content: input };
+    const newMessages = [...messages, userMessage];
+    setMessages(newMessages);
+    setInput('');
+    setLoading(true);
+
+    try {
+      const res = await fetch(
+        process.env.NEXT_PUBLIC_API_URL + '/chat/completions',
+        {
+          method: 'POST',
+          headers: {
+            'Content-Type': 'application/json',
+            Authorization: `Bearer ${session?.accessToken}`,
+          },
+          body: JSON.stringify({ model: selectedModel, messages: newMessages }),
+        },
+      );
+      const data = await res.json();
+      const assistant = data?.choices?.[0]?.message;
+      if (assistant) setMessages((prev) => [...prev, assistant]);
+    } catch (err) {
+      console.error(err);
+    } finally {
+      setLoading(false);
+    }
+  };
+
+  return (
+    <div className="flex flex-1 bg-primary text-primary transition-theme">
+      {/* ── Sidebar (icon rail + sliding panel) ── */}
+      <Sidebar panels={SIDEBAR_PANELS} />
+
+      {/* ── Main chat area ── */}
+      <div className="flex-1 flex flex-col min-w-0">
+        {/* Top bar */}
+        <header className="p-4 flex justify-between items-center border-b border-white/10">
+          <ModelSelect
+            models={models}
+            selectedModel={selectedModel}
+            setSelectedModel={setSelectedModel}
+          />
+        </header>
+
+        {/* Messages */}
+        <main className="flex-1 overflow-y-auto flex flex-col justify-end p-6">
+          <div className="w-full max-w-2xl mx-auto space-y-3">
+            {messages.map((msg, i) => (
+              <div key={i} className="text-sm">
+                <b>{msg.role === 'user' ? 'You' : 'AI'}:</b> {msg.content}
+              </div>
+            ))}
+            {loading && <div className="text-xs text-muted">Thinking...</div>}
+          </div>
+        </main>
+
+        {/* Input */}
+        <div className="p-4 border-t border-white/10">
+          <div className="w-full max-w-2xl mx-auto">
+            <input
+              value={input}
+              onChange={(e) => setInput(e.target.value)}
+              onKeyDown={(e) => e.key === 'Enter' && sendMessage()}
+              className="w-full p-3 rounded-xl bg-black/20 border border-muted outline-none"
+              placeholder="Message..."
+            />
+          </div>
+        </div>
+      </div>
+    </div>
+  );
+}
diff --git a/src/components/chat/ModelSelect.tsx b/src/components/chat/ModelSelect.tsx
new file mode 100644
index 0000000..151441d
--- /dev/null
+++ b/src/components/chat/ModelSelect.tsx
@@ -0,0 +1,81 @@
+'use client';
+
+import { useMemo, useState } from 'react';
+
+type Model = {
+  name: string;
+};
+
+type Props = {
+  models: Model[];
+  selectedModel: string | null;
+  setSelectedModel: (v: string) => void;
+};
+
+export default function ModelSelect({
+  models,
+  selectedModel,
+  setSelectedModel,
+}: Props) {
+  const [open, setOpen] = useState(false);
+
+  const maxWidth = useMemo(() => {
+    const longest =
+      models?.reduce((a, b) => (a.length > b.name.length ? a : b.name), '') ??
+      '';
+    return Math.min(Math.max(longest.length * 8, 140), 300);
+  }, [models]);
+
+  return (
+    <div className="relative inline-block">
+      {/* Trigger */}
+      <button
+        onClick={() => setOpen((v) => !v)}
+        className="flex items-center gap-2 bg-secondary border border-muted rounded-lg px-3 py-2 text-sm text-primary transition-fast"
+      >
+        <span>{selectedModel || 'Select model'}</span>
+
+        {/* Chevron */}
+        <svg
+          className={`w-4 h-4 transition-transform duration-200 ease-in-out ${
+            open ? 'rotate-180' : 'rotate-0'
+          }`}
+          viewBox="0 0 20 20"
+          fill="none"
+          stroke="currentColor"
+          strokeWidth="2"
+        >
+          <path d="M6 8l4 4 4-4" />
+        </svg>
+      </button>
+
+      {/* Dropdown */}
+      <div
+        style={{ width: maxWidth }}
+        className={`
+          absolute mt-2 bg-secondary border border-muted rounded-lg
+          overflow-hidden origin-top
+          transition-all duration-200 ease-in-out
+          ${
+            open
+              ? 'opacity-100 scale-100 translate-y-0'
+              : 'opacity-0 scale-95 -translate-y-1 pointer-events-none'
+          }
+        `}
+      >
+        {models?.map((model) => (
+          <div
+            key={model.name}
+            onClick={() => {
+              setSelectedModel(model.name);
+              setOpen(false);
+            }}
+            className="px-3 py-2 text-sm hover:bg-black/20 cursor-pointer whitespace-nowrap"
+          >
+            {model.name}
+          </div>
+        ))}
+      </div>
+    </div>
+  );
+}
diff --git a/src/components/chat/chat.panels.tsx b/src/components/chat/chat.panels.tsx
new file mode 100644
index 0000000..bb6b1e4
--- /dev/null
+++ b/src/components/chat/chat.panels.tsx
@@ -0,0 +1,136 @@
+import { useState } from 'react';
+import { SidebarPanel } from '../Sidebar';
+
+// ─── Example panels ───────────────────────────────────────────────────────────
+
+function ConversationHistoryPanel() {
+  const history = [
+    { id: 1, title: 'What is TypeScript?', time: '2m ago' },
+    { id: 2, title: 'Fix my React hook bug', time: '1h ago' },
+    { id: 3, title: 'Explain REST vs GraphQL', time: 'Yesterday' },
+  ];
+  return (
+    <ul className="space-y-1">
+      {history.map((h) => (
+        <li
+          key={h.id}
+          className="flex flex-col px-3 py-2 rounded-lg hover:bg-white/10 cursor-pointer transition-colors"
+        >
+          <span className="text-sm font-medium truncate">{h.title}</span>
+          <span className="text-xs text-white/40">{h.time}</span>
+        </li>
+      ))}
+    </ul>
+  );
+}
+
+function SettingsPanel() {
+  const [temp, setTemp] = useState(0.7);
+  const [stream, setStream] = useState(true);
+
+  return (
+    <div className="space-y-4 px-1">
+      <div>
+        <label className="text-xs text-primary uppercase tracking-widest transition-theme">
+          Temperature
+        </label>
+        <div className="flex items-center gap-3 mt-2">
+          <input
+            type="range"
+            min={0}
+            max={2}
+            step={0.1}
+            value={temp}
+            onChange={(e) => setTemp(Number(e.target.value))}
+            className="flex-1 accent-violet-400"
+          />
+          <span className="text-sm w-8 text-right">{temp}</span>
+        </div>
+      </div>
+      <div className="flex items-center justify-between">
+        <span className="text-sm">Streaming</span>
+        <button
+          onClick={() => setStream((s) => !s)}
+          className={`w-10 h-5 rounded-full transition-colors ${
+            stream ? 'bg-violet-500' : 'bg-white/20'
+          } relative`}
+        >
+          <span
+            className={`absolute top-0.5 w-4 h-4 rounded-full bg-white transition-all ${
+              stream ? 'left-5' : 'left-0.5'
+            }`}
+          />
+        </button>
+      </div>
+    </div>
+  );
+}
+
+function InfoPanel() {
+  return (
+    <div className="space-y-3 px-1 text-sm text-white/70">
+      <div className="rounded-lg bg-white/5 p-3 space-y-1">
+        <div className="flex justify-between">
+          <span>Tokens used</span>
+          <span className="text-white">1,240</span>
+        </div>
+        <div className="flex justify-between">
+          <span>Context left</span>
+          <span className="text-white">126k</span>
+        </div>
+        <div className="flex justify-between">
+          <span>Messages</span>
+          <span className="text-white">8</span>
+        </div>
+      </div>
+      <p className="text-xs text-white/30">Session started 14 min ago</p>
+    </div>
+  );
+}
+
+// ─── Panel registry — add yours here ─────────────────────────────────────────
+
+export const SIDEBAR_PANELS: SidebarPanel[] = [
+  {
+    id: 'history',
+    label: 'History',
+    icon: (
+      <svg viewBox="0 0 20 20" fill="currentColor" className="w-4 h-4">
+        <path
+          fillRule="evenodd"
+          d="M10 18a8 8 0 100-16 8 8 0 000 16zm.75-13a.75.75 0 00-1.5 0v5c0 .414.336.75.75.75h4a.75.75 0 000-1.5h-3.25V5z"
+          clipRule="evenodd"
+        />
+      </svg>
+    ),
+    component: <ConversationHistoryPanel />,
+  },
+  {
+    id: 'settings',
+    label: 'Settings',
+    icon: (
+      <svg viewBox="0 0 20 20" fill="currentColor" className="w-4 h-4">
+        <path
+          fillRule="evenodd"
+          d="M7.84 1.804A1 1 0 018.82 1h2.36a1 1 0 01.98.804l.331 1.652a6.993 6.993 0 011.929 1.115l1.598-.54a1 1 0 011.186.447l1.18 2.044a1 1 0 01-.205 1.251l-1.267 1.113a7.047 7.047 0 010 2.228l1.267 1.113a1 1 0 01.205 1.251l-1.18 2.044a1 1 0 01-1.186.447l-1.598-.54a6.993 6.993 0 01-1.929 1.115l-.33 1.652a1 1 0 01-.98.804H8.82a1 1 0 01-.98-.804l-.331-1.652a6.993 6.993 0 01-1.929-1.115l-1.598.54a1 1 0 01-1.186-.447l-1.18-2.044a1 1 0 01.205-1.251l1.267-1.114a7.05 7.05 0 010-2.227L1.821 7.773a1 1 0 01-.206-1.25l1.18-2.045a1 1 0 011.187-.447l1.598.54A6.993 6.993 0 017.51 3.456l.33-1.652zM10 13a3 3 0 100-6 3 3 0 000 6z"
+          clipRule="evenodd"
+        />
+      </svg>
+    ),
+    component: <SettingsPanel />,
+  },
+  {
+    id: 'info',
+    label: 'Info',
+    icon: (
+      <svg viewBox="0 0 20 20" fill="currentColor" className="w-4 h-4">
+        <path
+          fillRule="evenodd"
+          d="M18 10a8 8 0 11-16 0 8 8 0 0116 0zm-7-4a1 1 0 11-2 0 1 1 0 012 0zM9 9a.75.75 0 000 1.5h.253a.25.25 0 01.244.304l-.459 2.066A1.75 1.75 0 0010.747 15H11a.75.75 0 000-1.5h-.253a.25.25 0 01-.244-.304l.459-2.066A1.75 1.75 0 009.253 9H9z"
+          clipRule="evenodd"
+        />
+      </svg>
+    ),
+    component: <InfoPanel />,
+  },
+];
diff --git a/src/types/chat-api.tsx b/src/types/chat-api.tsx
new file mode 100644
index 0000000..b38e5a6
--- /dev/null
+++ b/src/types/chat-api.tsx
@@ -0,0 +1,17 @@
+export type ModelInfo = {
+  name: string;
+  family?: string | null;
+  parameter_size?: string | null;
+  quantization?: string | null;
+};
+
+export type ModelsResponse = {
+  models: ModelInfo[];
+};
+
+export type Role = 'system' | 'user' | 'assistant';
+
+export type Message = {
+  role: Role;
+  content: string;
+};