diff --git a/desktop/index.html b/desktop/index.html
index 40be90c..ea99676 100644
--- a/desktop/index.html
+++ b/desktop/index.html
@@ -151,6 +151,28 @@
           </div>
         </div>
       </div>
+      <!-- Key changed warning dialog -->
+      <div id="key-warning" class="hidden">
+        <div class="settings-card key-warning-card">
+          <div class="key-warning-icon">&#9888;</div>
+          <h2>Server Key Changed</h2>
+          <p class="key-warning-text">The relay's identity has changed since you last connected. This usually happens when the server was restarted, but could also indicate a security issue.</p>
+          <div class="key-warning-fps">
+            <div class="key-fp-row">
+              <span class="key-fp-label">Previously known</span>
+              <code id="kw-old-fp" class="key-fp"></code>
+            </div>
+            <div class="key-fp-row">
+              <span class="key-fp-label">New key</span>
+              <code id="kw-new-fp" class="key-fp"></code>
+            </div>
+          </div>
+          <div class="key-warning-actions">
+            <button id="kw-accept" class="primary">Accept New Key</button>
+            <button id="kw-cancel" class="secondary-btn">Cancel</button>
+          </div>
+        </div>
+      </div>
     </div>
     <script type="module" src="/src/main.ts"></script>
   </body>
diff --git a/desktop/src/main.ts b/desktop/src/main.ts
index 9a73c85..4abde04 100644
--- a/desktop/src/main.ts
+++ b/desktop/src/main.ts
@@ -76,6 +76,13 @@ const sFingerprint = document.getElementById("s-fingerprint")!;
 const sRecentRooms = document.getElementById("s-recent-rooms")!;
 const sClearRecent = document.getElementById("s-clear-recent")!;
 
+// Key warning dialog
+const keyWarning = document.getElementById("key-warning")!;
+const kwOldFp = document.getElementById("kw-old-fp")!;
+const kwNewFp = document.getElementById("kw-new-fp")!;
+const kwAccept = document.getElementById("kw-accept")!;
+const kwCancel = document.getElementById("kw-cancel")!;
+
 let statusInterval: number | null = null;
 let myFingerprint = "";
 let userDisconnected = false;
@@ -377,6 +384,28 @@ connectBtn.addEventListener("click", doConnect);
   el.addEventListener("keydown", (e) => { if (e.key === "Enter") doConnect(); })
 );
 
+function showKeyWarning(oldFp: string, newFp: string): Promise<boolean> {
+  return new Promise((resolve) => {
+    kwOldFp.textContent = oldFp;
+    kwNewFp.textContent = newFp;
+    keyWarning.classList.remove("hidden");
+
+    const cleanup = () => {
+      keyWarning.classList.add("hidden");
+      kwAccept.removeEventListener("click", onAccept);
+      kwCancel.removeEventListener("click", onCancel);
+      keyWarning.removeEventListener("click", onBackdrop);
+    };
+    const onAccept = () => { cleanup(); resolve(true); };
+    const onCancel = () => { cleanup(); resolve(false); };
+    const onBackdrop = (e: Event) => { if (e.target === keyWarning) { cleanup(); resolve(false); } };
+
+    kwAccept.addEventListener("click", onAccept);
+    kwCancel.addEventListener("click", onCancel);
+    keyWarning.addEventListener("click", onBackdrop);
+  });
+}
+
 async function doConnect() {
   const relay = getSelectedRelay();
   if (!relay) { connectError.textContent = "No relay selected"; return; }
@@ -384,13 +413,13 @@ async function doConnect() {
   // Warn on fingerprint mismatch
   const ls = lockStatus(relay);
   if (ls === "changed") {
-    if (!confirm(`Server fingerprint has changed!\n\nKnown: ${relay.knownFingerprint}\nNew: ${relay.serverFingerprint}\n\nThis could indicate a man-in-the-middle attack. Continue?`)) {
-      return;
-    }
+    const accepted = await showKeyWarning(relay.knownFingerprint || "", relay.serverFingerprint || "");
+    if (!accepted) return;
     // User accepted — update known fingerprint
     const s = loadSettings();
     s.relays[s.selectedRelay].knownFingerprint = relay.serverFingerprint;
     saveSettingsObj(s);
+    renderRelayButton();
   }
 
   // Don't block connect on offline — ping may have failed transiently
diff --git a/desktop/src/style.css b/desktop/src/style.css
index 02d3436..5d03216 100644
--- a/desktop/src/style.css
+++ b/desktop/src/style.css
@@ -652,6 +652,88 @@ button.primary:disabled { opacity: 0.5; cursor: not-allowed; }
 
 .secondary-btn:hover { border-color: var(--accent); color: var(--text); }
 
+/* ── Key warning dialog ── */
+#key-warning {
+  position: fixed;
+  inset: 0;
+  background: rgba(0, 0, 0, 0.7);
+  backdrop-filter: blur(6px);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 300;
+  padding: 20px;
+}
+
+.key-warning-card {
+  max-width: 360px;
+  text-align: center;
+  gap: 16px;
+}
+
+.key-warning-icon {
+  font-size: 48px;
+  color: var(--yellow);
+  line-height: 1;
+}
+
+.key-warning-card h2 {
+  font-size: 18px;
+  font-weight: 600;
+}
+
+.key-warning-text {
+  font-size: 13px;
+  color: var(--text-dim);
+  line-height: 1.5;
+}
+
+.key-warning-fps {
+  display: flex;
+  flex-direction: column;
+  gap: 8px;
+  background: var(--surface);
+  border-radius: 8px;
+  padding: 12px;
+}
+
+.key-fp-row {
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+  text-align: left;
+}
+
+.key-fp-label {
+  font-size: 10px;
+  text-transform: uppercase;
+  letter-spacing: 0.5px;
+  color: var(--text-dim);
+}
+
+.key-fp {
+  font-family: monospace;
+  font-size: 11px;
+  word-break: break-all;
+  color: var(--text);
+}
+
+.key-warning-actions {
+  display: flex;
+  gap: 10px;
+}
+
+.key-warning-actions .primary {
+  flex: 1;
+  background: var(--yellow);
+  color: #000;
+  font-weight: 600;
+}
+
+.key-warning-actions .secondary-btn {
+  flex: 1;
+}
+
 /* ── Quality slider ── */
 .quality-control {
   display: flex;