Coalesce index generation increments and add rebuild cooldown

backend/main.py

@@ -379,9 +379,14 @@ async def _on_vault_change(events: list):
     Processes each event (create/modify/delete/move) and updates the index
     incrementally, then broadcasts SSE notifications.
     """
+    import backend.indexer as idx
     updated_vaults = set()
     changes = []
 
+    # Temporarily suppress per-file generation increments to coalesce them
+    # into a single increment at the end of the batch.
+    old_gen = idx._index_generation
+
     for event in events:
         vault_name = event["vault"]
         event_type = event["type"]
@@ -410,6 +415,11 @@ async def _on_vault_change(events: list):
         except Exception as e:
             logger.error(f"Error processing {event_type} event for {src}: {e}")
 
+    # Restore generation to only increment by 1 for the whole batch
+    # (unless it was already incremented by other operations)
+    if idx._index_generation > old_gen + 1:
+        idx._index_generation = old_gen + 1
+
     if changes:
         await sse_manager.broadcast("index_updated", {
             "vaults": list(updated_vaults),