diff --git a/wwwroot/css/chat.css b/wwwroot/css/chat.css
index 46a6806..ff563e4 100644
--- a/wwwroot/css/chat.css
+++ b/wwwroot/css/chat.css
@@ -1,5 +1,52 @@
 .chat-page .page-content {
   align-items: stretch;
+  position: relative;
+}
+
+/* Usage Badge Overlay */
+
+.chat-usage-overlay {
+  position: absolute;
+  top: var(--page-spacing);
+  left: 50%;
+  transform: translateX(-50%);
+  z-index: 50;
+  display: flex;
+  align-items: center;
+  gap: calc(var(--badge-spacing) / 2);
+  opacity: 1;
+  transition: opacity var(--transition-duration), transform var(--transition-duration);
+  cursor: pointer;
+}
+
+.chat-usage-overlay[hidden] {
+  display: none;
+}
+
+.chat-usage-overlay.hidden {
+  opacity: 0;
+  transform: translateX(-50%) translateY(-1em);
+  pointer-events: none;
+}
+
+.chat-usage-overlay .usage-badge {
+  margin-top: 0;
+  background: var(--chat-bg);
+  border-color: var(--f3-border);
+}
+
+.chat-usage-overlay .chat-usage-check {
+  background: var(--chat-bg);
+  border: var(--border-width) solid var(--f3-border);
+  border-radius: var(--border-radius);
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.chat-usage-overlay .chat-usage-check:hover {
+  background: var(--f2-bg);
 }
 
 #chat {
@@ -1328,3 +1375,41 @@
   text-overflow: ellipsis;
   white-space: nowrap;
 }
+
+/* ── Key Switch Modal ── */
+
+.key-switch-list {
+  display: flex;
+  flex-direction: column;
+  gap: var(--badge-spacing);
+}
+
+.key-switch-row {
+  display: flex;
+  align-items: center;
+  gap: var(--badge-spacing);
+  padding: var(--badge-padding);
+  border: var(--border-width) solid var(--f3-border);
+  border-radius: var(--border-radius);
+  background: var(--f3-bg);
+}
+
+.key-switch-row.active {
+  border-color: var(--primary);
+  background: rgb(from var(--primary) r g b / .2);
+}
+
+.key-switch-info {
+  flex: 1;
+  min-width: 0;
+}
+
+.key-switch-name {
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.key-switch-meta {
+  opacity: var(--semi-transparent);
+}
diff --git a/wwwroot/index.html b/wwwroot/index.html
index 7e3d685..1967bc1 100644
--- a/wwwroot/index.html
+++ b/wwwroot/index.html
@@ -379,6 +379,7 @@
       </div>
     </header>
     <div class="page-content">
+      <div id="chatUsageBadge" class="chat-usage-overlay" hidden></div>
       <div id="chat"></div>
       <div class="meta-bar" id="meta"></div>
       <div id="filePreview" class="file-preview" hidden></div>
diff --git a/wwwroot/js/history.js b/wwwroot/js/history.js
index 9f2af22..5f104eb 100644
--- a/wwwroot/js/history.js
+++ b/wwwroot/js/history.js
@@ -482,6 +482,7 @@ async function pollHistory(force = false) {
     if (newMessages.length > 0) {
       renderMessages(newMessages, true);
       scrollDown();
+      if (typeof _refreshChatUsageBadge === 'function') _refreshChatUsageBadge();
     }
   } catch (e) {
     console.error('History poll fehlgeschlagen:', e);
diff --git a/wwwroot/js/pages/chat-page.js b/wwwroot/js/pages/chat-page.js
index 67e99ba..56ffbb4 100644
--- a/wwwroot/js/pages/chat-page.js
+++ b/wwwroot/js/pages/chat-page.js
@@ -4,6 +4,183 @@ let _streamingPollInterval = null;
 let _recoveryChainId = null;
 let _emojiPickerEl = null;
 let _emojiPickerCloseHandler = null;
+let _chatUsageKeyId = null;
+let _chatUsageScrollHandler = null;
+
+// ── Chat Usage Badge ──
+
+function _createChatUsageBadge(usage5h, usage7d) {
+  if (usage5h == null && usage7d == null) return null;
+  var badge = document.createElement('div');
+  badge.className = 'usage-badge';
+
+  function addRow(label, pct) {
+    if (pct == null) return;
+    var row = document.createElement('div');
+    row.className = 'usage-row';
+    var lbl = document.createElement('span');
+    lbl.className = 'usage-label';
+    lbl.textContent = label;
+    var track = document.createElement('div');
+    track.className = 'usage-track';
+    var fill = document.createElement('div');
+    fill.className = 'usage-fill';
+    if (pct >= 90) fill.className += ' danger';
+    else if (pct >= 70) fill.className += ' warn';
+    fill.style.width = Math.min(pct, 100) + '%';
+    track.appendChild(fill);
+    var val = document.createElement('span');
+    val.className = 'usage-pct';
+    val.textContent = pct + '%';
+    row.appendChild(lbl);
+    row.appendChild(track);
+    row.appendChild(val);
+    badge.appendChild(row);
+  }
+
+  addRow('Sitzung', usage5h);
+  addRow('Woche', usage7d);
+  return badge;
+}
+
+async function _initChatUsageBadge() {
+  if (!currentUser || !currentUser.isAdmin) return;
+  var container = document.getElementById('chatUsageBadge');
+  if (!container) return;
+
+  try {
+    var keys = await apiGetApiKeys();
+    var activeKey = keys.find(function(k) { return k.isActive; });
+    if (!activeKey) { container.hidden = true; return; }
+
+    _chatUsageKeyId = activeKey.keyId;
+    _renderChatUsageBadge(container, activeKey);
+    container.hidden = false;
+
+    // Scroll-Listener: Badge ausblenden wenn User nach oben scrollt
+    var chatEl = document.getElementById('chat');
+    if (chatEl) {
+      _chatUsageScrollHandler = function() {
+        var threshold = 60;
+        var atBottom = chatEl.scrollHeight - chatEl.scrollTop - chatEl.clientHeight <= threshold;
+        container.classList.toggle('hidden', !atBottom);
+      };
+      chatEl.addEventListener('scroll', _chatUsageScrollHandler);
+    }
+  } catch(e) {
+    console.error('Usage badge load failed:', e);
+  }
+}
+
+async function _refreshChatUsageBadge() {
+  if (!currentUser || !currentUser.isAdmin) return;
+  var container = document.getElementById('chatUsageBadge');
+  if (!container || !_chatUsageKeyId) return;
+  try {
+    var keys = await apiGetApiKeys();
+    var activeKey = keys.find(function(k) { return k.isActive; });
+    if (activeKey) _renderChatUsageBadge(container, activeKey);
+  } catch(e) { /* ignore */ }
+}
+
+function _renderChatUsageBadge(container, key) {
+  container.innerHTML = '';
+
+  var badge = _createChatUsageBadge(key.usage5h, key.usage7d);
+  if (badge) {
+    badge.addEventListener('click', function(e) {
+      e.stopPropagation();
+      _showKeySwitchModal();
+    });
+    badge.title = (key.name || 'API Key') + ' · ' + (key.plan || '?');
+    container.appendChild(badge);
+  }
+
+  var checkBtn = document.createElement('button');
+  checkBtn.className = 'chat-usage-check icon-btn';
+  checkBtn.innerHTML = '<i class="fa fa-refresh"></i>';
+  checkBtn.title = 'Key prüfen';
+  checkBtn.addEventListener('click', async function(e) {
+    e.stopPropagation();
+    checkBtn.disabled = true;
+    checkBtn.querySelector('i').className = 'fa fa-spinner fa-spin';
+    try {
+      var result = await apiCheckApiKey(_chatUsageKeyId);
+      if (result) {
+        var keys = await apiGetApiKeys();
+        var activeKey = keys.find(function(k) { return k.isActive; });
+        if (activeKey) _renderChatUsageBadge(container, activeKey);
+      }
+    } catch(e) {
+      console.error('Key check failed:', e);
+    }
+    checkBtn.disabled = false;
+    checkBtn.querySelector('i').className = 'fa fa-refresh';
+  });
+  container.appendChild(checkBtn);
+}
+
+async function _showKeySwitchModal() {
+  var keys = [];
+  try { keys = await apiGetApiKeys(); } catch(e) { return; }
+
+  var { body, close } = _createModal('API Key wechseln', { modal: 'key-switch-modal' });
+
+  var list = document.createElement('div');
+  list.className = 'key-switch-list';
+
+  keys.forEach(function(key) {
+    var row = document.createElement('div');
+    row.className = 'key-switch-row';
+    if (key.isActive) row.classList.add('active');
+
+    var info = document.createElement('div');
+    info.className = 'key-switch-info';
+
+    var name = document.createElement('div');
+    name.className = 'key-switch-name';
+    name.textContent = key.name || key.keyId;
+    info.appendChild(name);
+
+    var meta = document.createElement('div');
+    meta.className = 'key-switch-meta';
+    var parts = [];
+    if (key.plan) parts.push(key.plan);
+    if (key.status) parts.push(key.status === 'valid' ? '✅' : '⚠️');
+    meta.textContent = parts.join(' · ');
+    info.appendChild(meta);
+
+    row.appendChild(info);
+
+    var badge = _createChatUsageBadge(key.usage5h, key.usage7d);
+    if (badge) {
+      row.appendChild(badge);
+    }
+
+    if (!key.isActive) {
+      row.style.cursor = 'pointer';
+      row.addEventListener('click', async function() {
+        row.style.opacity = '0.5';
+        row.style.pointerEvents = 'none';
+        try {
+          var activeKey = keys.find(function(k) { return k.isActive; });
+          if (activeKey) await apiDeactivateApiKey(activeKey.keyId);
+          await apiActivateApiKey(key.keyId);
+          close();
+          await _initChatUsageBadge();
+        } catch(e) {
+          console.error('Key switch failed:', e);
+          row.style.opacity = '';
+          row.style.pointerEvents = '';
+        }
+      });
+    }
+
+    list.appendChild(row);
+  });
+
+  body.appendChild(list);
+}
 
 function _buildEmojiPicker() {
   const picker = document.createElement('div');
@@ -374,6 +551,9 @@ registerPage('chat', {
 
     await loadHistory();
 
+    // Usage Badge laden (Admin only)
+    _initChatUsageBadge();
+
     // Nach Font-Loading nochmal scrollen (Schriftart kann Höhe verändern)
     document.fonts.ready.then(() => {
       requestAnimationFrame(() => scrollDown());
@@ -402,6 +582,13 @@ registerPage('chat', {
     stopTypingIndicator();
     setCurrentAgentName(null);
     closeEmojiPicker();
+    // Usage Badge cleanup
+    if (_chatUsageScrollHandler) {
+      var chatEl = document.getElementById('chat');
+      if (chatEl) chatEl.removeEventListener('scroll', _chatUsageScrollHandler);
+      _chatUsageScrollHandler = null;
+    }
+    _chatUsageKeyId = null;
     if (this._closeMenu) {
       document.removeEventListener('click', this._closeMenu);
       this._closeMenu = null;