diff --git a/frontend/app/channel/[id]/page.tsx b/frontend/app/channel/[id]/page.tsx
index b9a83f6..41a195a 100644
--- a/frontend/app/channel/[id]/page.tsx
+++ b/frontend/app/channel/[id]/page.tsx
@@ -1,4 +1,5 @@
 import VideoCard from '../../components/VideoCard';
+import ChannelSubscribeButton from '../../components/ChannelSubscribeButton';
 import { notFound } from 'next/navigation';
 export const dynamic = 'force-dynamic';
 
@@ -93,9 +94,7 @@ export default async function ChannelPage({
                         <span style={{ opacity: 0.5 }}>•</span>
                         <span>{videos.length} videos</span>
                     </div>
-                    <button className="channel-subscribe-btn">
-                        Subscribe
-                    </button>
+                    <ChannelSubscribeButton channelId={info.id} channelName={info.title} />
                 </div>
             </div>
 
diff --git a/frontend/app/components/ChannelSubscribeButton.tsx b/frontend/app/components/ChannelSubscribeButton.tsx
new file mode 100644
index 0000000..3e7cf53
--- /dev/null
+++ b/frontend/app/components/ChannelSubscribeButton.tsx
@@ -0,0 +1,51 @@
+'use client';
+
+import { useState, useEffect } from 'react';
+
+export default function ChannelSubscribeButton({ channelId, channelName }: { channelId: string; channelName: string }) {
+    const [subscribed, setSubscribed] = useState(false);
+    const [loading, setLoading] = useState(false);
+
+    useEffect(() => {
+        fetch(`/api/subscribe?channel_id=${encodeURIComponent(channelId)}`)
+            .then(r => r.json())
+            .then(data => setSubscribed(data.subscribed))
+            .catch(() => setSubscribed(false));
+    }, [channelId]);
+
+    const handleSubscribe = async () => {
+        if (loading || !channelId) return;
+        setLoading(true);
+        try {
+            if (subscribed) {
+                const res = await fetch(`/api/subscribe?channel_id=${encodeURIComponent(channelId)}`, { method: 'DELETE' });
+                if (res.ok) setSubscribed(false);
+            } else {
+                const res = await fetch('/api/subscribe', {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({
+                        channel_id: channelId,
+                        channel_name: channelName || channelId,
+                        channel_avatar: channelName ? channelName[0].toUpperCase() : '?',
+                    }),
+                });
+                if (res.ok) setSubscribed(true);
+            }
+        } catch (error) {
+            console.error('Subscribe error:', error);
+        } finally {
+            setLoading(false);
+        }
+    };
+
+    return (
+        <button
+            className={`channel-subscribe-btn ${subscribed ? 'subscribed' : ''}`}
+            onClick={handleSubscribe}
+            disabled={loading}
+        >
+            {loading ? '...' : subscribed ? 'Subscribed' : 'Subscribe'}
+        </button>
+    );
+}
diff --git a/frontend/app/components/Header.tsx b/frontend/app/components/Header.tsx
index 2df77a4..7154db0 100644
--- a/frontend/app/components/Header.tsx
+++ b/frontend/app/components/Header.tsx
@@ -41,7 +41,6 @@ export default function Header() {
                     {/* Left */}
                     <div className="yt-header-left">
                         <button className="yt-icon-btn hamburger-btn" onClick={() => {
-                            toggleSidebar();
                             toggleMobileMenu();
                         }} title="Menu">
                             <IoMenuOutline size={22} />
diff --git a/frontend/app/context/SidebarContext.tsx b/frontend/app/context/SidebarContext.tsx
index ed16d8d..0c40814 100644
--- a/frontend/app/context/SidebarContext.tsx
+++ b/frontend/app/context/SidebarContext.tsx
@@ -16,23 +16,10 @@ interface SidebarContextType {
 const SidebarContext = createContext<SidebarContextType | undefined>(undefined);
 
 export function SidebarProvider({ children }: { children: ReactNode }) {
-    // Sidebar is collapsed by default on desktop
-    const [isSidebarOpen, setIsSidebarOpen] = useState(false);
+    // Sidebar is open by default on desktop (hidden on mobile via CSS)
+    const [isSidebarOpen, setIsSidebarOpen] = useState(true);
     const [isMobileMenuOpen, setIsMobileMenuOpen] = useState(false);
 
-    // Load saved preference from localStorage
-    useEffect(() => {
-        const saved = localStorage.getItem('sidebarOpen');
-        if (saved !== null) {
-            setIsSidebarOpen(saved === 'true');
-        }
-    }, []);
-
-    // Save preference to localStorage
-    useEffect(() => {
-        localStorage.setItem('sidebarOpen', isSidebarOpen.toString());
-    }, [isSidebarOpen]);
-
     const toggleSidebar = () => setIsSidebarOpen(prev => !prev);
     const openSidebar = () => setIsSidebarOpen(true);
     const closeSidebar = () => setIsSidebarOpen(false);
diff --git a/frontend/app/watch/ClientWatchPage.tsx b/frontend/app/watch/ClientWatchPage.tsx
index fcdf087..7bd5a2f 100644
--- a/frontend/app/watch/ClientWatchPage.tsx
+++ b/frontend/app/watch/ClientWatchPage.tsx
@@ -5,7 +5,7 @@ import { useSearchParams, useRouter } from 'next/navigation';
 import YouTubePlayer from './YouTubePlayer';
 import { getVideoDetailsClient, getRelatedVideosClient, getCommentsClient, searchVideosClient } from '../clientActions';
 import { VideoData } from '../constants';
-import { isSubscribed, toggleSubscription, addToHistory, isVideoSaved, toggleSaveVideo } from '../storage';
+import { isVideoSaved, toggleSaveVideo } from '../storage';
 import LoadingSpinner from '../components/LoadingSpinner';
 import Link from 'next/link';
 
@@ -39,33 +39,44 @@ function VideoInfo({ video }: { video: any }) {
     const [isSaved, setIsSaved] = useState(false);
     const [subscribing, setSubscribing] = useState(false);
 
-    // Check subscription and save status on mount
+    // Check subscription status via API and save status on mount
     useEffect(() => {
         if (video?.channelId) {
-            setSubscribed(isSubscribed(video.channelId));
+            fetch(`/api/subscribe?channel_id=${encodeURIComponent(video.channelId)}`)
+                .then(r => r.json())
+                .then(data => setSubscribed(data.subscribed))
+                .catch(() => setSubscribed(false));
         }
         if (video?.id) {
             setIsSaved(isVideoSaved(video.id));
         }
     }, [video?.channelId, video?.id]);
 
-    const handleSubscribe = useCallback(() => {
+    const handleSubscribe = useCallback(async () => {
         if (!video?.channelId || subscribing) return;
-        
         setSubscribing(true);
         try {
-            const nowSubscribed = toggleSubscription({
-                channelId: video.channelId,
-                channelName: video.channelTitle,
-                channelAvatar: '',
-            });
-            setSubscribed(nowSubscribed);
+            if (subscribed) {
+                const res = await fetch(`/api/subscribe?channel_id=${encodeURIComponent(video.channelId)}`, { method: 'DELETE' });
+                if (res.ok) setSubscribed(false);
+            } else {
+                const res = await fetch('/api/subscribe', {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({
+                        channel_id: video.channelId,
+                        channel_name: video.channelTitle || video.channelId,
+                        channel_avatar: '',
+                    }),
+                });
+                if (res.ok) setSubscribed(true);
+            }
         } catch (error) {
             console.error('Subscribe error:', error);
         } finally {
             setSubscribing(false);
         }
-    }, [video?.channelId, video?.channelTitle, subscribing]);
+    }, [video?.channelId, video?.channelTitle, subscribed, subscribing]);
 
     const handleSave = useCallback(() => {
         if (!video?.id) return;
@@ -636,14 +647,17 @@ export default function ClientWatchPage() {
                 }
                 setVideoInfo(video);
                 
-                // Add to watch history (localStorage)
+                // Add to watch history via API
                 if (video) {
-                    addToHistory({
-                        videoId: videoId,
-                        title: video.title,
-                        thumbnail: video.thumbnail,
-                        channelTitle: video.channelTitle,
-                    });
+                    fetch('/api/history', {
+                        method: 'POST',
+                        headers: { 'Content-Type': 'application/json' },
+                        body: JSON.stringify({
+                            video_id: videoId,
+                            title: video.title,
+                            thumbnail: video.thumbnail,
+                        }),
+                    }).catch(() => {});
                 }
                 
                 // Get related videos - use channel name and video title for better results