Move to SSoT for message dedup to prevent phantom unreads

frontend/src/App.tsx

@@ -57,8 +57,6 @@ const MAX_RAW_PACKETS = 500;
 
 export function App() {
   const messageInputRef = useRef<MessageInputHandle>(null);
-  // Track seen message content to prevent duplicate unread increments
-  const seenMessageContentRef = useRef<Set<string>>(new Set());
   const [rawPackets, setRawPackets] = useState<RawPacket[]>([]);
   const [showNewMessage, setShowNewMessage] = useState(false);
   const [showSettings, setShowSettings] = useState(false);
@@ -248,25 +246,13 @@ export function App() {
 
         const contentKey = getMessageContentKey(msg);
 
-        // Dedup: check if we've already seen this content BEFORE marking it seen.
-        const alreadySeen = !msg.outgoing && seenMessageContentRef.current.has(contentKey);
-        if (!msg.outgoing) {
-          seenMessageContentRef.current.add(contentKey);
-
-          // Limit set size to prevent memory issues
-          if (seenMessageContentRef.current.size > 1000) {
-            const keys = Array.from(seenMessageContentRef.current);
-            seenMessageContentRef.current = new Set(keys.slice(-500));
-          }
-        }
-
         // For non-active conversations: update cache and count unreads
         if (!isForActiveConversation) {
-          // Update message cache (instant restore on switch)
-          messageCache.addMessage(msg.conversation_key, msg, contentKey);
+          // Update message cache (instant restore on switch) — returns true if new
+          const isNew = messageCache.addMessage(msg.conversation_key, msg, contentKey);
 
           // Count unread for incoming messages (skip duplicates from multiple mesh paths)
-          if (!msg.outgoing && !alreadySeen) {
+          if (!msg.outgoing && isNew) {
             let stateKey: string | null = null;
             if (msg.type === 'CHAN' && msg.conversation_key) {
               stateKey = getStateKey('channel', msg.conversation_key);

frontend/src/messageCache.ts

@@ -49,12 +49,25 @@ export function set(id: string, entry: CacheEntry): void {
   }
 }
 
-/** Add a message to a cached (non-active) conversation with dedup. */
-export function addMessage(id: string, msg: Message, contentKey: string): void {
+/** Add a message to a cached conversation with dedup. Returns true if new, false if duplicate. */
+export function addMessage(id: string, msg: Message, contentKey: string): boolean {
   const entry = cache.get(id);
-  if (!entry) return;
-  if (entry.seenContent.has(contentKey)) return;
-  if (entry.messages.some((m) => m.id === msg.id)) return;
+  if (!entry) {
+    // Auto-create a minimal entry for never-visited conversations
+    cache.set(id, {
+      messages: [msg],
+      seenContent: new Set([contentKey]),
+      hasOlderMessages: true,
+    });
+    // Evict LRU if over capacity
+    if (cache.size > MAX_CACHED_CONVERSATIONS) {
+      const lruKey = cache.keys().next().value as string;
+      cache.delete(lruKey);
+    }
+    return true;
+  }
+  if (entry.seenContent.has(contentKey)) return false;
+  if (entry.messages.some((m) => m.id === msg.id)) return false;
   entry.seenContent.add(contentKey);
   entry.messages = [...entry.messages, msg];
   // Trim if over limit (drop oldest by received_at)
@@ -63,6 +76,7 @@ export function addMessage(id: string, msg: Message, contentKey: string): void {
       .sort((a, b) => b.received_at - a.received_at)
       .slice(0, MAX_MESSAGES_PER_ENTRY);
   }
+  return true;
 }
 
 /** Scan all cached entries for a message ID and update its ack/paths. */

frontend/src/test/integration.test.ts

@@ -8,10 +8,11 @@
  * between backend and frontend - both sides test against the same data.
  */
 
-import { describe, it, expect } from 'vitest';
+import { describe, it, expect, beforeEach } from 'vitest';
 import fixtures from './fixtures/websocket_events.json';
 import { getMessageContentKey } from '../hooks/useConversationMessages';
 import { getStateKey } from '../utils/conversationState';
+import * as messageCache from '../messageCache';
 import type { Message, Contact, Channel } from '../types';
 
 /**
@@ -24,7 +25,8 @@ interface MockState {
   channels: Channel[];
   unreadCounts: Record<string, number>;
   lastMessageTimes: Record<string, number>;
-  seenMessageContent: Set<string>;
+  /** Active-conversation dedup (mirrors useConversationMessages internal set) */
+  seenActiveContent: Set<string>;
 }
 
 function createMockState(): MockState {
@@ -34,13 +36,16 @@ function createMockState(): MockState {
     channels: [],
     unreadCounts: {},
     lastMessageTimes: {},
-    seenMessageContent: new Set(),
+    seenActiveContent: new Set(),
   };
 }
 
 /**
  * Simulate handling a message WebSocket event.
  * Mirrors the logic in App.tsx onMessage handler.
+ *
+ * Non-active conversation dedup uses messageCache.addMessage (single source of truth).
+ * Active conversation dedup uses seenActiveContent (mirrors useConversationMessages).
  */
 function handleMessageEvent(
   state: MockState,
@@ -57,8 +62,8 @@ function handleMessageEvent(
 
   // Add to messages if for active conversation (with deduplication)
   if (isForActiveConversation) {
-    if (!state.seenMessageContent.has(contentKey)) {
-      state.seenMessageContent.add(contentKey);
+    if (!state.seenActiveContent.has(contentKey)) {
+      state.seenActiveContent.add(contentKey);
       state.messages.push(msg);
       added = true;
     }
@@ -73,10 +78,10 @@ function handleMessageEvent(
   state.lastMessageTimes[stateKey] = msg.received_at;
 
   // Increment unread if not for active conversation and not outgoing
-  if (!msg.outgoing && !isForActiveConversation) {
-    // Deduplicate by content
-    if (!state.seenMessageContent.has(contentKey)) {
-      state.seenMessageContent.add(contentKey);
+  // Uses messageCache.addMessage as single source of truth for dedup
+  if (!isForActiveConversation) {
+    const isNew = messageCache.addMessage(msg.conversation_key, msg, contentKey);
+    if (!msg.outgoing && isNew) {
       state.unreadCounts[stateKey] = (state.unreadCounts[stateKey] || 0) + 1;
       unreadIncremented = true;
     }
@@ -111,6 +116,11 @@ function handleMessageAckedEvent(state: MockState, messageId: number, ackCount:
   return false;
 }
 
+// Clear messageCache between tests to avoid cross-test contamination
+beforeEach(() => {
+  messageCache.clear();
+});
+
 describe('Integration: Channel Message Events', () => {
   const fixture = fixtures.channel_message;
 
@@ -317,6 +327,61 @@ describe('Integration: ACK Events', () => {
   });
 });
 
+describe('Integration: No phantom unreads from mesh echoes (hitlist #8 regression)', () => {
+  it('does not increment unread when a mesh echo arrives after many unique messages', () => {
+    const state = createMockState();
+    const convKey = 'channel_busy';
+
+    // Deliver 1001 unique messages — exceeding the old global
+    // seenMessageContentRef prune threshold (1000→500). Under the old
+    // dual-set design the global set would drop msg-0's key during pruning,
+    // so a later mesh echo of msg-0 would pass the global check and
+    // phantom-increment unread. With the fix, messageCache's per-conversation
+    // seenContent is the single source of truth and is never pruned.
+    const MESSAGE_COUNT = 1001;
+    for (let i = 0; i < MESSAGE_COUNT; i++) {
+      const msg: Message = {
+        id: i,
+        type: 'CHAN',
+        conversation_key: convKey,
+        text: `msg-${i}`,
+        sender_timestamp: 1700000000 + i,
+        received_at: 1700000000 + i,
+        paths: null,
+        txt_type: 0,
+        signature: null,
+        outgoing: false,
+        acked: 0,
+      };
+      handleMessageEvent(state, msg, 'other_active_conv');
+    }
+
+    const stateKey = getStateKey('channel', convKey);
+    expect(state.unreadCounts[stateKey]).toBe(MESSAGE_COUNT);
+
+    // Now a mesh echo of msg-0 arrives (same content, different id).
+    // msg-0's key would have been evicted by the old 1000→500 prune.
+    const echo: Message = {
+      id: 9999,
+      type: 'CHAN',
+      conversation_key: convKey,
+      text: 'msg-0',
+      sender_timestamp: 1700000000, // same sender_timestamp as original
+      received_at: 1700001000,
+      paths: null,
+      txt_type: 0,
+      signature: null,
+      outgoing: false,
+      acked: 0,
+    };
+    const result = handleMessageEvent(state, echo, 'other_active_conv');
+
+    // Must NOT increment unread — the echo is a duplicate
+    expect(result.unreadIncremented).toBe(false);
+    expect(state.unreadCounts[stateKey]).toBe(MESSAGE_COUNT);
+  });
+});
+
 describe('Integration: Message Content Key Contract', () => {
   it('generates consistent keys for deduplication', () => {
     const msg = fixtures.channel_message.expected_ws_event.data as unknown as Message;

frontend/src/test/messageCache.test.ts

@@ -150,38 +150,45 @@ describe('messageCache', () => {
   });
 
   describe('addMessage', () => {
-    it('adds message to existing cached conversation', () => {
+    it('adds message to existing cached conversation and returns true', () => {
       messageCache.set('conv1', createEntry([]));
 
       const msg = createMessage({ id: 10, text: 'New message' });
-      messageCache.addMessage('conv1', msg, 'CHAN-channel123-New message-1700000000');
+      const result = messageCache.addMessage(
+        'conv1',
+        msg,
+        'CHAN-channel123-New message-1700000000'
+      );
 
+      expect(result).toBe(true);
       const entry = messageCache.get('conv1');
       expect(entry!.messages).toHaveLength(1);
       expect(entry!.messages[0].text).toBe('New message');
     });
 
-    it('deduplicates by content key', () => {
+    it('deduplicates by content key and returns false', () => {
       messageCache.set('conv1', createEntry([]));
 
       const msg1 = createMessage({ id: 10, text: 'Hello' });
       const contentKey = 'CHAN-channel123-Hello-1700000000';
-      messageCache.addMessage('conv1', msg1, contentKey);
+      expect(messageCache.addMessage('conv1', msg1, contentKey)).toBe(true);
 
       // Same content key, different message id
       const msg2 = createMessage({ id: 11, text: 'Hello' });
-      messageCache.addMessage('conv1', msg2, contentKey);
+      expect(messageCache.addMessage('conv1', msg2, contentKey)).toBe(false);
 
       const entry = messageCache.get('conv1');
       expect(entry!.messages).toHaveLength(1);
     });
 
-    it('deduplicates by message id', () => {
+    it('deduplicates by message id and returns false', () => {
       messageCache.set('conv1', createEntry([createMessage({ id: 10, text: 'Original' })]));
 
       // Same id, different content key
       const msg = createMessage({ id: 10, text: 'Different' });
-      messageCache.addMessage('conv1', msg, 'CHAN-channel123-Different-1700000000');
+      expect(messageCache.addMessage('conv1', msg, 'CHAN-channel123-Different-1700000000')).toBe(
+        false
+      );
 
       const entry = messageCache.get('conv1');
       expect(entry!.messages).toHaveLength(1);
@@ -200,8 +207,13 @@ describe('messageCache', () => {
         text: 'newest',
         received_at: 1700000000 + MAX_MESSAGES_PER_ENTRY,
       });
-      messageCache.addMessage('conv1', newMsg, `CHAN-channel123-newest-${newMsg.sender_timestamp}`);
+      const result = messageCache.addMessage(
+        'conv1',
+        newMsg,
+        `CHAN-channel123-newest-${newMsg.sender_timestamp}`
+      );
 
+      expect(result).toBe(true);
       const entry = messageCache.get('conv1');
       expect(entry!.messages).toHaveLength(MAX_MESSAGES_PER_ENTRY);
       // Newest message should be kept
@@ -210,11 +222,34 @@ describe('messageCache', () => {
       expect(entry!.messages.some((m) => m.id === 0)).toBe(false);
     });
 
-    it('ignores messages for non-cached conversations', () => {
-      const msg = createMessage({ id: 10 });
-      // Should not throw
-      messageCache.addMessage('nonexistent', msg, 'key');
-      expect(messageCache.size()).toBe(0);
+    it('auto-creates a minimal entry for never-visited conversations and returns true', () => {
+      const msg = createMessage({ id: 10, text: 'First contact' });
+      const result = messageCache.addMessage(
+        'new_conv',
+        msg,
+        'CHAN-channel123-First contact-1700000000'
+      );
+
+      expect(result).toBe(true);
+      expect(messageCache.size()).toBe(1);
+      const entry = messageCache.get('new_conv');
+      expect(entry).toBeDefined();
+      expect(entry!.messages).toHaveLength(1);
+      expect(entry!.messages[0].text).toBe('First contact');
+      expect(entry!.hasOlderMessages).toBe(true);
+      expect(entry!.seenContent.has('CHAN-channel123-First contact-1700000000')).toBe(true);
+    });
+
+    it('returns false for duplicate delivery to auto-created entry', () => {
+      const msg = createMessage({ id: 10, text: 'Echo' });
+      const contentKey = 'CHAN-channel123-Echo-1700000000';
+
+      expect(messageCache.addMessage('new_conv', msg, contentKey)).toBe(true);
+      // Duplicate via mesh echo
+      expect(messageCache.addMessage('new_conv', msg, contentKey)).toBe(false);
+
+      const entry = messageCache.get('new_conv');
+      expect(entry!.messages).toHaveLength(1);
     });
   });