fix(search): wrap group_ids OR clause in parentheses for BM25 queries

Without parentheses around the OR clause, Lucene operator precedence
causes AND to bind tighter than OR, so only the last group_id is
effectively filtered when multiple group_ids are provided.

Before: group_id:"g1" OR group_id:"g2" AND (query)
 → parsed as: g1 OR (g2 AND query)

After: (group_id:"g1" OR group_id:"g2") AND (query)
 → correctly filters by all group_ids

Fixes #1249

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: giulio-leone

graphiti_core/search/search_utils.py

@@ -98,7 +98,8 @@ def fulltext_query(query: str, group_ids: list[str] | None, driver: GraphDriver)
     for f in group_ids_filter_list:
         group_ids_filter += f if not group_ids_filter else f' OR {f}'
 
-    group_ids_filter += ' AND ' if group_ids_filter else ''
+    if group_ids_filter:
+        group_ids_filter = '(' + group_ids_filter + ') AND '
 
     lucene_query = lucene_sanitize(query)
     # If the lucene query is too long return no query

tests/utils/search/search_utils_test.py

@@ -1,10 +1,10 @@
-from unittest.mock import AsyncMock, patch
+from unittest.mock import AsyncMock, MagicMock, patch
 
 import pytest
 
 from graphiti_core.nodes import EntityNode
 from graphiti_core.search.search_filters import SearchFilters
-from graphiti_core.search.search_utils import hybrid_node_search
+from graphiti_core.search.search_utils import fulltext_query, hybrid_node_search
 
 
 @pytest.mark.asyncio
@@ -161,3 +161,37 @@ async def test_hybrid_node_search_with_limit_and_duplicates():
         mock_similarity_search.assert_called_with(
             mock_driver, [0.1, 0.2, 0.3], SearchFilters(), ['1'], 4
         )
+
+
+class TestFulltextQueryGroupIds:
+    """Regression tests for group_ids filter parenthesization (issue #1249)."""
+
+    @staticmethod
+    def _neo4j_driver() -> MagicMock:
+        from graphiti_core.driver.driver import GraphProvider
+
+        driver = MagicMock()
+        driver.provider = GraphProvider.NEO4J
+        driver.fulltext_syntax = ''
+        return driver
+
+    def test_single_group_id(self):
+        driver = self._neo4j_driver()
+        result = fulltext_query('hello', ['g1'], driver)
+        assert result == '(group_id:"g1") AND (hello)'
+
+    def test_multiple_group_ids_parenthesized(self):
+        """The OR clause must be wrapped in parentheses so AND binds correctly."""
+        driver = self._neo4j_driver()
+        result = fulltext_query('hello', ['g1', 'g2', 'g3'], driver)
+        assert result == '(group_id:"g1" OR group_id:"g2" OR group_id:"g3") AND (hello)'
+
+    def test_no_group_ids(self):
+        driver = self._neo4j_driver()
+        result = fulltext_query('hello', None, driver)
+        assert result == '(hello)'
+
+    def test_empty_group_ids(self):
+        driver = self._neo4j_driver()
+        result = fulltext_query('hello', [], driver)
+        assert result == '(hello)'