fix: reconcile chat_message via explicit deletions

Author: Algorithm5838

backend/open_webui/models/chats.py

@@ -139,6 +139,8 @@ class ChatFileModel(BaseModel):
 class ChatForm(BaseModel):
     chat: dict
     folder_id: str | None = None
+    # Explicit deletions to prune; absent => upsert-only.
+    deleted_message_ids: list[str] | None = None
 
 
 class ChatImportForm(ChatForm):
@@ -499,22 +501,42 @@ async def backfill_messages_by_chat_id(self, chat_id: str, user_id: str, message
                 log.warning('Backfill failed for message %s in chat %s: %s', message_id, chat_id, e)
 
     async def reconcile_messages_by_chat_id(
-        self, chat_id: str, user_id: str, messages: dict[str, dict]
+        self,
+        chat_id: str,
+        user_id: str,
+        messages: dict[str, dict],
+        deleted_message_ids: list[str] | None = None,
     ) -> None:
-        """Sync ``chat_message`` rows with the committed JSON blob.
+        """Upsert blob messages, then prune only the IDs the client explicitly
+        deleted (plus their now-orphaned descendants).
 
-        Upserts current messages via ``backfill_messages_by_chat_id``
-        and deletes orphaned rows whose message_id no longer appears
-        in the blob.  Best-effort: errors are logged but never raised.
+        Rows merely missing from the blob are never inferred as deletions — a
+        lost write race would otherwise drop a still-valid message permanently.
+        Best-effort: errors are logged, not raised.
         """
         try:
             await self.backfill_messages_by_chat_id(chat_id, user_id, messages)
 
-            existing_map = await ChatMessages.get_messages_map_by_chat_id(chat_id)
-            if existing_map is not None:
-                orphaned_ids = set(existing_map.keys()) - set(messages.keys())
-                if orphaned_ids:
-                    await ChatMessages.delete_message_ids_by_chat_id(chat_id, orphaned_ids)
+            dead_ids = set(deleted_message_ids or [])
+            if not dead_ids:
+                return
+
+            existing_map = await ChatMessages.get_messages_map_by_chat_id(chat_id) or {}
+
+            # Reparented children reappear in the blob and survive; truly orphaned ones go with the parent.
+            changed = True
+            while changed:
+                changed = False
+                for message_id, message in existing_map.items():
+                    if message_id in dead_ids or message_id in messages:
+                        continue
+                    if message.get('parentId') in dead_ids:
+                        dead_ids.add(message_id)
+                        changed = True
+
+            dead_ids &= set(existing_map.keys())
+            if dead_ids:
+                await ChatMessages.delete_message_ids_by_chat_id(chat_id, dead_ids)
         except Exception as e:
             log.warning('Failed to reconcile chat_message rows for chat %s: %s', chat_id, e)
 

backend/open_webui/routers/chats.py

@@ -993,7 +993,9 @@ async def update_chat_by_id(
         # history with potential edits, deletions, or new branches.
         messages = (updated_chat.get('history') or {}).get('messages') or {}
         if messages:
-            await Chats.reconcile_messages_by_chat_id(id, user.id, messages)
+            await Chats.reconcile_messages_by_chat_id(
+                id, user.id, messages, deleted_message_ids=form_data.deleted_message_ids
+            )
 
         return ChatResponse(**chat.model_dump())
     else:

src/lib/apis/chats/index.ts

@@ -1039,7 +1039,12 @@ export const getChatAccessGrants = async (token: string, id: string) => {
 	return res;
 };
 
-export const updateChatById = async (token: string, id: string, chat: object) => {
+export const updateChatById = async (
+	token: string,
+	id: string,
+	chat: object,
+	deletedMessageIds: string[] | null = null
+) => {
 	let error = null;
 
 	const res = await fetch(`${WEBUI_API_BASE_URL}/chats/${id}`, {
@@ -1050,7 +1055,11 @@ export const updateChatById = async (token: string, id: string, chat: object) =>
 			...(token && { authorization: `Bearer ${token}` })
 		},
 		body: JSON.stringify({
-			chat: chat
+			chat: chat,
+			// Omit when empty so ordinary saves stay upsert-only.
+			...(deletedMessageIds && deletedMessageIds.length
+				? { deleted_message_ids: deletedMessageIds }
+				: {})
 		})
 	})
 		.then(async (res) => {

src/lib/components/chat/Messages.svelte

@@ -164,14 +164,24 @@
 		}
 	};
 
+	// Deletions buffered since the last save; the backend prunes exactly these.
+	let deletedMessageIds = new Set();
+
 	const updateChat = async () => {
 		if (!$temporaryChatEnabled) {
 			history = history;
 			await tick();
-			const res = await updateChatById(localStorage.token, chatId, {
-				history: history,
-				messages: messages
-			});
+			const res = await updateChatById(
+				localStorage.token,
+				chatId,
+				{
+					history: history,
+					messages: messages
+				},
+				Array.from(deletedMessageIds)
+			);
+			// Reached only on success (updateChatById throws otherwise); keep IDs for retry on failure.
+			deletedMessageIds.clear();
 
 			// Refresh local message content from backend (e.g. re-derived via serialize_output)
 			if (res?.chat?.history?.messages) {
@@ -461,9 +471,11 @@
 		// Delete the message and its children
 		[messageId, ...childMessageIds].forEach((id) => {
 			delete history.messages[id];
+			deletedMessageIds.add(id);
 		});
 
 		showMessage({ id: parentMessageId }, false);
+		await updateChat();
 	};
 
 	const triggerScroll = () => {