diff --git a/src/static/css/style.css b/src/static/css/style.css
index d9c973f..dc4f859 100644
--- a/src/static/css/style.css
+++ b/src/static/css/style.css
@@ -4841,6 +4841,19 @@ a.map-popup-article:hover {
     }
 }
 
+/* Fullscreen */
+.chat-window.fullscreen {
+    bottom: 0;
+    right: 0;
+    left: 0;
+    top: 0;
+    width: 100%;
+    height: 100%;
+    border-radius: 0;
+    border: none;
+    z-index: 10000;
+}
+
 /* Light Theme */
 [data-theme="light"] .chat-window {
     box-shadow: 0 8px 32px rgba(0,0,0,0.12);
diff --git a/src/static/dashboard.html b/src/static/dashboard.html
index 849d203..ff3d583 100644
--- a/src/static/dashboard.html
+++ b/src/static/dashboard.html
@@ -595,7 +595,10 @@
                 <button class="chat-header-btn chat-reset-btn" id="chat-reset-btn" title="Neuer Chat" aria-label="Neuen Chat starten" style="display:none">
                     <svg viewBox="0 0 24 24" width="15" height="15"><path d="M17.65 6.35A7.958 7.958 0 0012 4c-4.42 0-7.99 3.58-7.99 8s3.57 8 7.99 8c3.73 0 6.84-2.55 7.73-6h-2.08A5.99 5.99 0 0112 18c-3.31 0-6-2.69-6-6s2.69-6 6-6c1.66 0 3.14.69 4.22 1.78L13 11h7V4l-2.35 2.35z" fill="currentColor"/></svg>
                 </button>
-            <button class="chat-header-btn chat-header-close" id="chat-close-btn" title="Schließen" aria-label="Chat schließen">&times;</button>
+                <button class="chat-header-btn" id="chat-fullscreen-btn" title="Vollbild" aria-label="Vollbild umschalten">
+                    <svg viewBox="0 0 24 24" width="15" height="15"><path d="M7 14H5v5h5v-2H7v-3zm-2-4h2V7h3V5H5v5zm12 7h-3v2h5v-5h-2v3zM14 5v2h3v3h2V5h-5z" fill="currentColor"/></svg>
+                </button>
+                <button class="chat-header-btn chat-header-close" id="chat-close-btn" title="Schließen" aria-label="Chat schließen">&times;</button>
             </div>
         </div>
         <div class="chat-messages" id="chat-messages"></div>
diff --git a/src/static/js/chat.js b/src/static/js/chat.js
index ccc822d..ff6c54f 100644
--- a/src/static/js/chat.js
+++ b/src/static/js/chat.js
@@ -6,6 +6,7 @@ const Chat = {
     _isOpen: false,
     _isLoading: false,
     _hasGreeted: false,
+    _isFullscreen: false,
 
     init() {
         const btn = document.getElementById('chat-toggle-btn');
@@ -21,6 +22,9 @@ const Chat = {
         const resetBtn = document.getElementById('chat-reset-btn');
         if (resetBtn) resetBtn.addEventListener('click', () => this.reset());
 
+        const fsBtn = document.getElementById('chat-fullscreen-btn');
+        if (fsBtn) fsBtn.addEventListener('click', () => this.toggleFullscreen());
+
         form.addEventListener('submit', (e) => {
             e.preventDefault();
             this.send();
@@ -74,8 +78,15 @@ const Chat = {
         const btn = document.getElementById('chat-toggle-btn');
         if (!win) return;
         win.classList.remove('open');
+        win.classList.remove('fullscreen');
         btn.classList.remove('active');
         this._isOpen = false;
+        this._isFullscreen = false;
+        const fsBtn = document.getElementById('chat-fullscreen-btn');
+        if (fsBtn) {
+            fsBtn.title = 'Vollbild';
+            fsBtn.innerHTML = '<svg viewBox="0 0 24 24" width="15" height="15"><path d="M7 14H5v5h5v-2H7v-3zm-2-4h2V7h3V5H5v5zm12 7h-3v2h5v-5h-2v3zM14 5v2h3v3h2V5h-5z" fill="currentColor"/></svg>';
+        }
     },
 
     reset() {
@@ -88,6 +99,20 @@ const Chat = {
         this.open();
     },
 
+    toggleFullscreen() {
+        const win = document.getElementById('chat-window');
+        const btn = document.getElementById('chat-fullscreen-btn');
+        if (!win) return;
+        this._isFullscreen = !this._isFullscreen;
+        win.classList.toggle('fullscreen', this._isFullscreen);
+        if (btn) {
+            btn.title = this._isFullscreen ? 'Vollbild beenden' : 'Vollbild';
+            btn.innerHTML = this._isFullscreen
+                ? '<svg viewBox="0 0 24 24" width="15" height="15"><path d="M5 16h3v3h2v-5H5v2zm3-8H5v2h5V5H8v3zm6 11h2v-3h3v-2h-5v5zm2-11V5h-2v5h5V8h-3z" fill="currentColor"/></svg>'
+                : '<svg viewBox="0 0 24 24" width="15" height="15"><path d="M7 14H5v5h5v-2H7v-3zm-2-4h2V7h3V5H5v5zm12 7h-3v2h5v-5h-2v3zM14 5v2h3v3h2V5h-5z" fill="currentColor"/></svg>';
+        }
+    },
+
     _updateResetBtn() {
         const btn = document.getElementById('chat-reset-btn');
         if (btn) btn.style.display = this._conversationId ? '' : 'none';