diff --git a/backend/open_webui/socket/main.py b/backend/open_webui/socket/main.py
index 59537f259e..bbcfaea4e2 100644
--- a/backend/open_webui/socket/main.py
+++ b/backend/open_webui/socket/main.py
@@ -719,12 +719,31 @@ async def resume_stream(sid, data):
     envelopes = []
     user = SESSION_POOL.get(sid)
     user_id = user.get('id') if user else None
-    if user_id and REDIS is not None:
+    # Gate read on REALTIME mode to match the write-side gate. Otherwise
+    # stale logs written before the flag was flipped (or by a mixed-
+    # version peer) would still get replayed on top of DB-backed content
+    # and double-apply.
+    if user_id and REDIS is not None and not ENABLE_REALTIME_CHAT_SAVE:
         try:
             last_seq = int(data.get('last_seq') or 0)
         except (TypeError, ValueError):
             last_seq = 0
-        envelopes = await _stream_log_read(user_id, message_id, last_seq)
+        # Defense-in-depth: validate chat ownership even though the log
+        # key is already user-scoped. Rejects only when we can *prove*
+        # ownership fails — a missing/unknown chat_id falls through to
+        # the user-scoped key guarantee so we don't regress the "stub
+        # not yet persisted in DB" refresh case.
+        chat_id = data.get('chat_id')
+        chat_ok = True
+        if chat_id:
+            try:
+                chat = await Chats.get_chat_by_id_and_user_id(chat_id, user_id)
+                chat_ok = chat is not None
+            except Exception as e:
+                log.warning(f'resume-stream chat ownership check failed: {e}')
+                chat_ok = True  # fail open to not regress legitimate callers
+        if chat_ok:
+            envelopes = await _stream_log_read(user_id, message_id, last_seq)
 
     await sio.emit(
         'resume-stream:replay',
diff --git a/src/lib/components/chat/Chat.svelte b/src/lib/components/chat/Chat.svelte
index 4fce682952..1b5449971e 100644
--- a/src/lib/components/chat/Chat.svelte
+++ b/src/lib/components/chat/Chat.svelte
@@ -699,6 +699,7 @@
 				: `${message.id}-${Date.now()}-${Math.random()}`;
 		resumeActiveRequestIdByMessageId.set(message.id, requestId);
 		$socket.emit('resume-stream', {
+			chat_id: $chatId,
 			message_id: message.id,
 			request_id: requestId,
 			last_seq: resumeSeqByMessageId.get(message.id) ?? 0
@@ -708,10 +709,12 @@
 	const onResumeStreamReplay = async (payload) => {
 		const messageId = payload?.message_id;
 		if (!messageId) return;
-		// Drop stale replies from superseded requests so they can't
-		// clear a fence that belongs to a newer in-flight request.
+		// Drop stale replies. If an active request_id is set for this
+		// message, require an exact match — a reply without a request_id,
+		// or with a mismatched one, belongs to a superseded request and
+		// must not clear the active fence.
 		const expected = resumeActiveRequestIdByMessageId.get(messageId);
-		if (expected && payload?.request_id && payload.request_id !== expected) {
+		if (expected && payload?.request_id !== expected) {
 			return;
 		}
 		resumeActiveRequestIdByMessageId.delete(messageId);