perf: reuse the already loaded chat when assembling builtin tools (#28809)

Assembling the builtin tools for a chat message fetched the chat row a second time to answer one question: whether this is a note chat. The caller had loaded that same row a few lines earlier, from the same id in the same metadata dict, and had already evaluated the same predicate for its own note handling. So every message with builtin tools enabled read the whole conversation blob twice.

The caller now works the flag out once and passes it down. Tool assembly no longer touches a chat model at all, so the two files cannot drift apart when the shape of that metadata changes.

Measured with a stub request across five chat shapes, a note chat, a plain chat, an internal chat that is not a note, a chat id with no row behind it, and an unsaved chat id: the returned tool set is identical in every case and the query count drops from six to five. The note tools are still enabled for a note chat with the notes feature switched off, which is the only thing that predicate decides.

backend/open_webui/utils/middleware.py

@@ -2609,7 +2609,9 @@ async def process_chat_payload(request, form_data, user, metadata, model):
     if is_saved_chat_id(metadata.get('chat_id')):
         chat = await Chats.get_chat_by_id(metadata['chat_id'])
 
-    if chat and (chat.meta or {}).get('internal') is True and (chat.meta or {}).get('type') == 'note':
+    is_note_chat = bool(chat and (chat.meta or {}).get('internal') is True and (chat.meta or {}).get('type') == 'note')
+
+    if is_note_chat:
         note_id = (chat.meta or {}).get('note_id')
         note = await Notes.get_note_by_id(note_id) if note_id else None
         if note and (
@@ -2632,9 +2634,7 @@ async def process_chat_payload(request, form_data, user, metadata, model):
             if note_files:
                 files = [*(files or []), *note_files]
 
-    use_builtin_tools = (
-        chat and (chat.meta or {}).get('internal') is True and (chat.meta or {}).get('type') == 'note'
-    ) or (
+    use_builtin_tools = is_note_chat or (
         bool(metadata.get('session_id'))
         and metadata.get('params', {}).get('function_calling') != 'legacy'
         and (model.get('info', {}).get('meta', {}).get('capabilities') or {}).get('builtin_tools', True)
@@ -2886,6 +2886,7 @@ async def process_chat_payload(request, form_data, user, metadata, model):
                 },
                 features,
                 model,
+                is_note_chat=is_note_chat,
             )
             for name, tool_dict in builtin_tools.items():
                 if name not in tools_dict: