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),

backend/search.py

@@ -265,15 +265,22 @@ class InvertedIndex:
         self.tag_docs: Dict[str, set] = defaultdict(set)
         self._sorted_tokens: List[str] = []
         self._source_generation: int = -1
+        self._last_rebuild: float = 0
+        self._rebuild_cooldown: float = 3.0  # seconds
 
     def is_stale(self) -> bool:
         """Check if the inverted index needs rebuilding.
 
-        Uses the indexer's generation counter which increments on every
-        rebuild, instead of ``id(index)`` which never changes since the
-        global dict is mutated in-place.
+        Uses a cooldown (3s) to prevent rapid rebuilds from file watcher
+        events. Staleness is only reported if the generation has changed
+        AND the cooldown has elapsed since the last rebuild.
         """
-        return _indexer._index_generation != self._source_generation
+        import time
+        if _indexer._index_generation == self._source_generation:
+            return False
+        if time.time() - self._last_rebuild < self._rebuild_cooldown:
+            return False
+        return True
 
     def rebuild(self) -> None:
         """Rebuild inverted index from the global ``index`` dict.
@@ -281,6 +288,8 @@ class InvertedIndex:
         Tokenizes titles and content of every file, computes term frequencies,
         and builds auxiliary indexes for tag and title prefix suggestions.
         """
+        import time
+        self._last_rebuild = time.time()
         logger.info("Rebuilding inverted index...")
         self.word_index = defaultdict(dict)
         self.title_index = defaultdict(list)