Coalesce index generation increments and add rebuild cooldown

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)