diff --git a/kez-chat/web/src/lib/inbox-service.svelte.ts b/kez-chat/web/src/lib/inbox-service.svelte.ts
index ef5412a..e15de70 100644
--- a/kez-chat/web/src/lib/inbox-service.svelte.ts
+++ b/kez-chat/web/src/lib/inbox-service.svelte.ts
@@ -54,20 +54,28 @@ class InboxService {
   #pollTimer: ReturnType<typeof setInterval> | null = null;
   /** Callbacks for "new message arrived" — Messages page subscribes to repaint. */
   #listeners = new Set<() => void>();
+  /** Highest seq we've already shown a notification for. Anything <= this
+   *  was either already-known on session start (so the user has seen it
+   *  on this or another device) or already notified about. */
+  #notifiedThroughSeq = -1;
 
   /** Start streaming for this session. Called from App.svelte on unlock. */
-  start(handle: string, seed: Uint8Array) {
+  async start(handle: string, seed: Uint8Array) {
     // No-op if already running for this handle.
     if (this.#handle === handle && this.#stream) return;
     this.stop();
     this.#handle = handle;
     this.#seed = seed;
     this.status = "connecting";
+    // Seed the notification watermark from the persisted cursor so we
+    // don't notify-storm for messages already in the conversation cache
+    // (which the user has either seen on this device or another).
+    this.#notifiedThroughSeq = await getGlobalCursor();
 
     this.#stream = streamInbox({
       handle,
       seed,
-      onMessage: (m) => void this.#ingest(m, /*viaPush=*/ true),
+      onMessage: (m) => void this.#ingest(m),
       onStatus: (s) => (this.status = s),
     });
     this.#pollTimer = setInterval(() => void this.#heartbeat(), POLL_INTERVAL_MS);
@@ -106,7 +114,7 @@ class InboxService {
         seed: this.#seed,
         since,
       });
-      for (const m of messages) await this.#ingest(m, /*viaPush=*/ false);
+      for (const m of messages) await this.#ingest(m);
       this.lastError = null;
       this.lastPolledAt = new Date().toISOString();
     } catch (e) {
@@ -114,7 +122,7 @@ class InboxService {
     }
   }
 
-  async #ingest(m: InboxMessage, viaPush: boolean) {
+  async #ingest(m: InboxMessage) {
     if (!this.#handle || !this.#seed) return;
     try {
       const pt = await decrypt(m.envelope, this.#handle, this.#seed);
@@ -138,9 +146,20 @@ class InboxService {
         body: pt.body,
         ts: pt.sent_at,
       });
-      this.unreadCount += 1;
-      this.#notifyListeners();
-      if (viaPush) this.#fireSystemNotification(displayName || pt.from, pt.body);
+      // Only fire UI side-effects (badge + system notification) for
+      // messages we haven't already notified about. This guards both:
+      //  • SSE+poll race: same seq comes in twice via different paths
+      //  • Startup catch-up: don't badge/notify the entire history
+      if (m.seq > this.#notifiedThroughSeq) {
+        this.#notifiedThroughSeq = m.seq;
+        this.unreadCount += 1;
+        this.#notifyListeners();
+        this.#fireSystemNotification(displayName || pt.from, pt.body);
+      } else {
+        // Still tell components so they repaint (avoid stale UI), but
+        // skip the noisy badge++ + system notification.
+        this.#notifyListeners();
+      }
     } catch (e) {
       console.error(`inbox-service: seq ${m.seq} decrypt failed`, e);
     }
@@ -201,3 +220,36 @@ export async function requestNotificationsPermission(): Promise<NotificationPerm
   if (!notificationsSupported()) return "unsupported";
   return await Notification.requestPermission();
 }
+
+/**
+ * Fire a one-shot notification right now so the user can verify their
+ * OS + browser settings actually deliver. Useful when debugging
+ * "I clicked Allow but I see nothing" — fails loud with a return value
+ * the caller can show.
+ *
+ * Notably this fires REGARDLESS of document.visibilityState — the user
+ * is testing while looking at the page, so suppressing would defeat
+ * the purpose.
+ */
+export function fireTestNotification(): { ok: boolean; reason?: string } {
+  if (!notificationsSupported()) {
+    return { ok: false, reason: "Notification API not available" };
+  }
+  if (Notification.permission !== "granted") {
+    return {
+      ok: false,
+      reason: `permission is "${Notification.permission}" — click Enable first`,
+    };
+  }
+  try {
+    new Notification("kez-chat · Test", {
+      body: "If you see this, notifications are working. New chat messages will look the same.",
+      icon: "/pwa-192x192.png",
+      badge: "/pwa-64x64.png",
+      tag: "kez-chat-test",
+    });
+    return { ok: true };
+  } catch (e) {
+    return { ok: false, reason: (e as Error).message };
+  }
+}
diff --git a/kez-chat/web/src/routes/Dashboard.svelte b/kez-chat/web/src/routes/Dashboard.svelte
index 8daacbb..7a7e79b 100644
--- a/kez-chat/web/src/routes/Dashboard.svelte
+++ b/kez-chat/web/src/routes/Dashboard.svelte
@@ -21,6 +21,7 @@
     notificationsSupported,
     notificationsPermission,
     requestNotificationsPermission,
+    fireTestNotification,
   } from "../lib/inbox-service.svelte.js";
 
   let registryRecord = $state<any | null>(null);
@@ -105,6 +106,13 @@
     notifPerm = await requestNotificationsPermission();
   }
 
+  let testNotifResult = $state<{ ok: boolean; reason?: string } | null>(null);
+  function sendTestNotification() {
+    testNotifResult = fireTestNotification();
+    // Auto-clear after a few seconds so the panel doesn't grow stale.
+    setTimeout(() => (testNotifResult = null), 5_000);
+  }
+
   async function disableBiometric() {
     if (!confirm("Disable biometric unlock for this device? You'll need your passphrase to unlock next time.")) return;
     await removeStoredBiometric();
@@ -329,10 +337,29 @@
           Notifications aren't supported in this browser.
         </p>
       {:else if notifPerm === "granted"}
-        <p class="mt-3 text-sm text-green-800 bg-green-50 border border-green-200 rounded p-3">
-          ✓ Notifications enabled. New messages will pop up when this tab
-          isn't visible.
-        </p>
+        <div class="mt-3 space-y-3">
+          <p class="text-sm text-green-800 bg-green-50 border border-green-200 rounded p-3">
+            ✓ Notifications enabled. New messages will pop up when this tab
+            isn't visible.
+          </p>
+          <button
+            class="px-3 py-1.5 text-sm border border-gray-300 rounded-md text-gray-700 hover:bg-gray-50"
+            onclick={sendTestNotification}
+          >
+            Send test notification
+          </button>
+          {#if testNotifResult?.ok === true}
+            <p class="text-xs text-green-700">
+              ✓ Sent. If you didn't see anything, check your OS notification
+              settings (System Settings → Notifications → Chrome on macOS,
+              Settings → Apps → Notifications on Windows/Android).
+            </p>
+          {:else if testNotifResult?.ok === false}
+            <p class="text-xs text-red-700">
+              ✗ {testNotifResult.reason}
+            </p>
+          {/if}
+        </div>
       {:else if notifPerm === "denied"}
         <p class="mt-3 text-sm text-amber-800 bg-amber-50 border border-amber-200 rounded p-3">
           You blocked notifications for this site. Re-enable them in your