Fix same-second same-message collision in room servers with per-sender disambiguation at DB level

frontend/src/test/useConversationMessages.test.ts

@@ -161,6 +161,80 @@ describe('getMessageContentKey', () => {
 
     expect(getMessageContentKey(msg1)).toBe(getMessageContentKey(msg2));
   });
+
+  it('PRIV messages with different sender_key produce different keys (room dedup)', () => {
+    const msg1 = createMessage({
+      type: 'PRIV',
+      conversation_key: 'room_pubkey',
+      text: 'ok',
+      sender_timestamp: 1700000000,
+      sender_key: 'alice_key',
+    });
+    const msg2 = createMessage({
+      type: 'PRIV',
+      conversation_key: 'room_pubkey',
+      text: 'ok',
+      sender_timestamp: 1700000000,
+      sender_key: 'bob_key',
+    });
+
+    expect(getMessageContentKey(msg1)).not.toBe(getMessageContentKey(msg2));
+  });
+
+  it('PRIV messages with same sender_key still dedup (true room echo)', () => {
+    const msg1 = createMessage({
+      type: 'PRIV',
+      conversation_key: 'room_pubkey',
+      text: 'ok',
+      sender_timestamp: 1700000000,
+      sender_key: 'alice_key',
+    });
+    const msg2 = createMessage({
+      type: 'PRIV',
+      conversation_key: 'room_pubkey',
+      text: 'ok',
+      sender_timestamp: 1700000000,
+      sender_key: 'alice_key',
+    });
+
+    expect(getMessageContentKey(msg1)).toBe(getMessageContentKey(msg2));
+  });
+
+  it('CHAN messages ignore sender_key (channel dedup unchanged)', () => {
+    const msg1 = createMessage({
+      type: 'CHAN',
+      text: 'hello',
+      sender_timestamp: 1700000000,
+      sender_key: 'alice_key',
+    });
+    const msg2 = createMessage({
+      type: 'CHAN',
+      text: 'hello',
+      sender_timestamp: 1700000000,
+      sender_key: 'bob_key',
+    });
+
+    expect(getMessageContentKey(msg1)).toBe(getMessageContentKey(msg2));
+  });
+
+  it('PRIV messages with null sender_key still dedup normally', () => {
+    const msg1 = createMessage({
+      type: 'PRIV',
+      conversation_key: 'contact_key',
+      text: 'hi',
+      sender_timestamp: 1700000000,
+      sender_key: null,
+    });
+    const msg2 = createMessage({
+      type: 'PRIV',
+      conversation_key: 'contact_key',
+      text: 'hi',
+      sender_timestamp: 1700000000,
+      sender_key: null,
+    });
+
+    expect(getMessageContentKey(msg1)).toBe(getMessageContentKey(msg2));
+  });
 });
 
 describe('mergePendingAck', () => {

frontend/src/utils/messageIdentity.ts

@@ -1,10 +1,14 @@
 import type { Message } from '../types';
 
-// Content identity matches the frontend's message-level dedup contract.
+// Content identity matches the backend's message-level dedup indexes.
 export function getMessageContentKey(msg: Message): string {
   // When sender_timestamp exists, dedup by content (catches radio-path duplicates with different IDs).
   // When null, include msg.id so each message gets a unique key — avoids silently dropping
   // different messages that share the same text and received_at second.
   const ts = msg.sender_timestamp ?? `r${msg.received_at}-${msg.id}`;
-  return `${msg.type}-${msg.conversation_key}-${msg.text}-${ts}`;
+  // For incoming PRIV messages (room-server posts), include sender_key so that
+  // two different room participants sending identical text in the same second
+  // are not collapsed.  Mirrors idx_messages_incoming_priv_dedup.
+  const senderSuffix = msg.type === 'PRIV' && msg.sender_key ? `-${msg.sender_key}` : '';
+  return `${msg.type}-${msg.conversation_key}-${msg.text}-${ts}${senderSuffix}`;
 }