fix: notifications are deduped in memory, not just in persistant storage

src/renderer/src/moss-store.ts

@@ -70,6 +70,7 @@ import {
 } from './electron-api.js';
 import {
   devModeToolLibraryFromDevConfig,
+  encodeAndStringify,
   findAppForDnaHash,
   getNotificationState,
   sortVersionsDescending,
@@ -167,6 +168,13 @@ export type DevModeToolLibrary = {
   devCollective: DeveloperCollective;
 };
 
+function getNotificationFeedEntryId({ source, notification }: MossNotification): string {
+  const sourceKey =
+    source.type === 'applet' ? `applet:${source.appletId}` : `group:${source.groupDnaHash}`;
+
+  return `${sourceKey}:${encodeAndStringify(notification)}`;
+}
+
 export class MossStore {
   constructor(
     public adminWebsocket: AdminWebsocket,
@@ -698,12 +706,25 @@ export class MossStore {
   ): Promise<void> {
     const mainWindowFocused = await window.electronAPI.isMainWindowFocused();
 
-    for (const notification of notifications) {
-      // 1. Persist if requested (tools do this, foyer doesn't)
-      if (options.persist && source.type === 'applet') {
-        storeAppletNotifications([notification], source.appletId, true, this.persistedStore);
-      }
+    // 1. Persist if requested (tools do this, foyer doesn't)
+    if (options.persist && source.type === 'applet') {
+      storeAppletNotifications(notifications, source.appletId, true, this.persistedStore);
+    }
 
+    // Deduplicate incoming notifications against what's already in the feed so that
+    // OS notifications, sounds, and unread counts are not triggered for duplicates.
+    const existingFeedIds = new Set(
+      get(this._notificationFeed).map((entry) => getNotificationFeedEntryId(entry)),
+    );
+    const seenInBatch = new Set<string>();
+    const newNotifications = notifications.filter((notification) => {
+      const id = getNotificationFeedEntryId({ source, notification, sourceName: options.sourceName });
+      if (existingFeedIds.has(id) || seenInBatch.has(id)) return false;
+      seenInBatch.add(id);
+      return true;
+    });
+
+    for (const notification of newNotifications) {
       // 2. Update unread count for sidebar dot
       if (options.updateUnreadCount) {
         if (source.type === 'applet') {
@@ -727,16 +748,6 @@ export class MossStore {
         }
       }
 
-      // 3. Add to activity feed
-      if (options.showInFeed) {
-        this._notificationFeed.update((feed) => {
-          const newNotification: MossNotification = { source, notification, sourceName: options.sourceName };
-          return [newNotification, ...feed].sort(
-            (a, b) => b.notification.timestamp - a.notification.timestamp,
-          );
-        });
-      }
-
       // 4. Send OS notification if conditions are met
       if (
         options.sendOSNotification &&
@@ -764,6 +775,20 @@ export class MossStore {
       }
     }
 
+    // 3. Add to activity feed (done once after the loop to avoid O(k*n²))
+    if (options.showInFeed && newNotifications.length > 0) {
+      this._notificationFeed.update((feed) => {
+        const newEntries: MossNotification[] = newNotifications.map((notification) => ({
+          source,
+          notification,
+          sourceName: options.sourceName,
+        }));
+        return [...newEntries, ...feed].sort(
+          (a, b) => b.notification.timestamp - a.notification.timestamp,
+        );
+      });
+    }
+
   }
 
   /**