fix(kernel): keep local path validation scoped to transfers

Signed-off-by: Aakash Saravanan <aakash.saravanan@databricks.com>

Author: aakash-saravanan-db

CHANGELOG.md

@@ -1,7 +1,7 @@
 # Release History
 
 # Unreleased
-- Support SQL PUT, GET, and REMOVE file transfers with a native kernel exposing `Statement.set_staging_allowed_local_paths`; older wheels reject transfers and continue to support ordinary queries.
+- Support SQL PUT, GET, and REMOVE file transfers with a native kernel exposing `Statement.set_staging_allowed_local_paths`; older wheels reject transfers and continue to support ordinary queries. Streaming PUT remains unsupported in kernel mode.
 - Fix inline parameters (`use_inline_params=True`) so a sequence directly after `IN` renders as a list again: `x IN %(ids)s` renders as `x IN (1,2,3)` instead of `x IN ARRAY(1,2,3)`, which Spark rejects. Inside the list, tuples render as rows for a multi-column `IN`, and a `set` or `frozenset` is accepted again. Sequences anywhere else still render as `ARRAY(...)` ([#629](https://github.com/databricks/databricks-sql-python/issues/629))
 
 # 4.9.0 (2026-11-04)

CONNECTION_PARAMETERS.md

@@ -171,7 +171,7 @@ to change without notice.
 | `use_inline_params`           | `bool` \| `"silent"`              |   ✅   |   ✅   | `False`       | Render parameters inline (legacy) vs. native bound params (DBR 14.1+). Shared cursor code performs the rendering before dispatch, so both backends honor it identically. |
 | `ignore_transactions`         | `bool`                            |   ✅   |   ✅   | `True`        | When `True`: `commit()` is a no-op, `rollback()` raises `NotSupportedError`, and setting `autocommit` is a no-op.          |
 | `fetch_autocommit_from_server`| `bool`                            |   ✅   |   ✅   | `False`       | Query the server (`SET AUTOCOMMIT`) for autocommit state instead of returning the cached value.                           |
-| `staging_allowed_local_path`  | `str` \| `List[str]`              |   ✅   |   ✅   | `None`        | Local path(s) permitted for Unity Catalog Volume `PUT`/`GET`. Kernel transfers require a wheel exposing `Statement.set_staging_allowed_local_paths` (kernel [#439](https://github.com/databricks/databricks-sql-kernel/pull/439)); older wheels reject transfer commands.          |
+| `staging_allowed_local_path`  | `str` \| `List[str]`              |   ✅   |   ✅   | `None`        | Local path(s) permitted for Unity Catalog Volume `PUT`/`GET`. Kernel transfers require a wheel exposing `Statement.set_staging_allowed_local_paths` (kernel [#439](https://github.com/databricks/databricks-sql-kernel/pull/439)); older wheels reject transfer commands. Kernel mode does not support streaming PUT.          |
 
 ## Telemetry
 

KERNEL_REV

@@ -1 +1 @@
-02283500d50e1bcd61007e0cf04a7e1e3d16ea86
+2f317d97212f00d73b89d947f5261a2145ea7a10

src/databricks/sql/backend/kernel/_errors.py

@@ -17,8 +17,8 @@
   "only PEP 249 exception types cross the boundary". Wrapped in
   ``OperationalError`` here.
 
-Local missing transfer files deliberately retain the built-in
-``FileNotFoundError`` contract.
+Local missing transfer files use the built-in ``FileNotFoundError`` class;
+the OS ``errno`` and ``filename`` attributes are unavailable.
 
 These primitives live in their own module so both ``client.py``
 (which orchestrates PyO3 calls) and ``result_set.py`` (which calls
@@ -192,7 +192,8 @@ def wrap_kernel_exception(
     """Map a PyO3 exception to the connector's public error contract.
 
     - ``KernelError`` → mapped class with structured attrs forwarded.
-      A local missing transfer file maps to ``FileNotFoundError``.
+      A local missing transfer file maps to ``FileNotFoundError`` without
+      the OS ``errno`` or ``filename`` attributes.
     - Already-PEP-249 ``Error`` (e.g. raised by an inner caller that
       already mapped) → passed through unchanged.
     - Anything else (``TypeError`` / ``ValueError`` / etc. from PyO3

src/databricks/sql/backend/kernel/client.py

@@ -588,7 +588,11 @@ def execute_command(
                         "Streaming PUT is not supported by the kernel backend."
                     )
                 stmt.set_sql(operation)
-                allowed_paths = cursor.connection.staging_allowed_local_path
+                allowed_paths = (
+                    cursor.connection.staging_allowed_local_path
+                    if _is_staging_statement(operation)
+                    else None
+                )
                 if isinstance(allowed_paths, (str, os.PathLike)):
                     allowed_paths = [allowed_paths]
                 set_paths = getattr(stmt, "set_staging_allowed_local_paths", None)

src/databricks/sql/client.py

@@ -1394,7 +1394,7 @@ def _handle_staging_put(
                 session_id_hex=self.connection.get_session_id_hex(),
             )
 
-        # The kernel completes configured transfers before reaching these handlers.
+        # Kernel backends transfer files natively and never dispatch to these handlers.
         assert self.connection.http_client is not None
         with open(local_file, "rb") as fh:
             r = self.connection.http_client.request(

tests/e2e/test_kernel_backend.py

@@ -367,9 +367,7 @@ def test_schemas_with_empty_string_filter_matches_nothing(conn):
         assert cur.fetchall() == []
 
 
-@pytest.mark.parametrize(
-    "empty_filter", ["schema_name", "table_name", "column_name"]
-)
+@pytest.mark.parametrize("empty_filter", ["schema_name", "table_name", "column_name"])
 def test_columns_with_empty_string_filter_matches_nothing(conn, empty_filter):
     filters = {
         "catalog_name": "system",

tests/unit/test_kernel_client.py

@@ -847,6 +847,24 @@ def test_execute_command_forwards_allowed_local_paths(allowed, expected, async_o
     (stmt.submit if async_op else stmt.execute).assert_called_once()
 
 
+@pytest.mark.parametrize("allowed", [123, [object()]])
+def test_non_transfer_query_ignores_malformed_local_paths(allowed):
+    c = _make_client()
+    c._kernel_session = MagicMock()
+    cursor = MagicMock()
+    cursor.connection.staging_allowed_local_path = allowed
+    stmt = c._kernel_session.statement.return_value
+    stmt.execute.return_value = MagicMock(
+        statement_id="00000000-0000-0000-0000-000000000001",
+        arrow_schema=MagicMock(return_value=pa.schema([("x", pa.int64())])),
+    )
+    c.execute_command(
+        "SELECT 1", MagicMock(), 1, 1, False, cursor, False, [], False, False
+    )
+    stmt.set_staging_allowed_local_paths.assert_called_once_with([])
+    stmt.execute.assert_called_once()
+
+
 @pytest.mark.parametrize(
     "query",
     [