fix(repair): close active backend before rollback restore

Rollback cleanup was instantiating a fresh ChromaBackend, so the live backend that had opened the PersistentClient could keep file handles alive during restore. Close the active backend instance instead so rollback and CLI recovery can release Windows-safe locks before copying the backup back into place.

mempalace/cli.py

@@ -760,7 +760,7 @@ def cmd_repair(args):
         if getattr(e, "live_replaced", False):
             print("  Live collection was already replaced; restoring from backup...")
             try:
-                _close_chroma_handles(palace_path)
+                _close_chroma_handles(palace_path, backend=backend)
                 if os.path.exists(palace_path):
                     shutil.rmtree(palace_path)
                 shutil.copytree(backup_path, palace_path)

mempalace/repair.py

@@ -517,7 +517,7 @@ def rebuild_index(palace_path=None, confirm_truncation_ok: bool = False):
         if e.live_replaced and os.path.exists(backup_path):
             print(f"  Restoring from backup: {backup_path}")
             try:
-                _close_chroma_handles(palace_path)
+                _close_chroma_handles(palace_path, backend=backend)
                 _delete_collection_if_exists(backend, palace_path, COLLECTION_NAME)
                 shutil.copy2(backup_path, sqlite_path)
                 print("  Backup restored. Palace is back to pre-repair state.")
@@ -593,12 +593,18 @@ def status(palace_path=None) -> dict:
 # ---------------------------------------------------------------------------
 
 
-def _close_chroma_handles(palace_path: str) -> None:
-    """Drop ChromaBackend + chromadb singleton caches so OS mmap handles release."""
+def _close_chroma_handles(palace_path: str, backend: ChromaBackend | None = None) -> None:
+    """Drop ChromaBackend + chromadb singleton caches so OS mmap handles release.
+
+    When ``backend`` is provided, close the live instance so rollback/restore
+    releases the handles it was already using. Otherwise fall back to a
+    transient backend instance for the max-seq-id repair path.
+    """
     import gc
 
     try:
-        ChromaBackend().close_palace(palace_path)
+        closer = backend if backend is not None else ChromaBackend()
+        closer.close_palace(palace_path)
     except Exception:
         pass
     try:

tests/test_cli.py

@@ -799,17 +799,14 @@ def test_cmd_repair_restores_backup_on_live_rebuild_failure(mock_config_cls, tmp
     mock_temp_col.count.return_value = 2
     mock_backend = _mock_backend_for(col=mock_col)
     mock_backend.create_collection.side_effect = [mock_temp_col, RuntimeError("live build failed")]
-    with (
-        patch("mempalace.backends.chroma.ChromaBackend", return_value=mock_backend),
-        patch("mempalace.repair._close_chroma_handles") as mock_close_handles,
-    ):
+    with patch("mempalace.backends.chroma.ChromaBackend", return_value=mock_backend):
         with pytest.raises(SystemExit) as excinfo:
             cmd_repair(args)
     out = capsys.readouterr().out
     assert excinfo.value.code == 1
     assert "Repair failed" in out
     assert "restoring from backup" in out
-    mock_close_handles.assert_called_once_with(str(palace_dir))
+    mock_backend.close_palace.assert_called_once_with(str(palace_dir))
     assert mock_backend.delete_collection.call_args_list == [
         call(str(palace_dir), "mempalace_drawers__repair_tmp"),
         call(str(palace_dir), "mempalace_drawers"),

tests/test_repair.py

@@ -499,20 +499,25 @@ def test_rebuild_index_live_failure_restores_backup(mock_backend_cls, mock_shuti
     mock_temp_col.count.return_value = 2
     mock_new_col = MagicMock()
     mock_new_col.upsert.side_effect = RuntimeError("live upsert failed")
-    mock_backend = _install_mock_backend(mock_backend_cls, mock_col)
-    mock_backend.create_collection.side_effect = [mock_temp_col, mock_new_col]
+    active_backend = MagicMock()
+    active_backend.get_collection.return_value = mock_col
+    active_backend.create_collection.side_effect = [mock_temp_col, mock_new_col]
+    helper_backend = MagicMock()
+    mock_backend_cls.side_effect = [active_backend, helper_backend]
 
     with pytest.raises(repair.RebuildCollectionError) as excinfo:
         repair.rebuild_index(palace_path=str(tmp_path))
 
     assert excinfo.value.live_replaced is True
     assert mock_shutil.copy2.call_count == 2
-    assert mock_backend.delete_collection.call_args_list == [
+    assert active_backend.delete_collection.call_args_list == [
         call(str(tmp_path), "mempalace_drawers__repair_tmp"),
         call(str(tmp_path), "mempalace_drawers"),
         call(str(tmp_path), "mempalace_drawers__repair_tmp"),
         call(str(tmp_path), "mempalace_drawers"),
     ]
+    active_backend.close_palace.assert_called_once_with(str(tmp_path))
+    helper_backend.close_palace.assert_not_called()
 
 
 @patch("mempalace.repair.shutil")