Merge branch 'main' into pydap4_scale

Author: Mikejmnez

doc/whats-new.rst

@@ -7,36 +7,32 @@ What's New
 
 .. _whats-new.2025.10.0:
 
-v2025.10.0 (unreleased)
------------------------
-
-New Features
-~~~~~~~~~~~~
-
-- Improved ``pydap`` backend behavior and performance when using :py:func:`open_dataset`, :py:func:`open_datatree` when downloading dap4 (opendap) data (:issue:`10628`, :pull:`10629`).
-  ``batch=True|False`` is a new  ``backend_kwarg`` that further enables downloading multiple arrays in single response. In addition ``checksums`` is added as optional argument to be passed to ``pydap`` backend.
-  By `Miguel Jimenez-Urias <https://github.com/Mikejmnez>`_.
+v2025.10.0 (October 6, 2025)
+----------------------------
 
+This release reverts a breaking change to Xarray's preferred netCDF backend.
 
 Breaking changes
 ~~~~~~~~~~~~~~~~
 
-
-Deprecations
-~~~~~~~~~~~~
+- Xarray's default engine for reading/writing netCDF files has been reverted to
+  prefer netCDF4, which was the default before v2025.09.1. This change
+  had larger implications for the ecosystem than we anticipated. We are still
+  considering changing the default in the future, but will be a bit more careful
+  about the implications. See :issue:`10657` and linked issues for discussion.
+  The behavior can still be customized, e.g., with
+  ``xr.set_options(netcdf_engine_order=['h5netcdf', 'netcdf4', 'scipy'])``.
+  By `Stephan Hoyer <https://github.com/shoyer>`_.
 
 
 Bug fixes
 ~~~~~~~~~
 
-
-Documentation
-~~~~~~~~~~~~~
+- Fix error raised when writing scalar variables to Zarr with ``region={}``
+  (:pull:`10796`).
+  By `Stephan Hoyer <https://github.com/shoyer>`_.
 
 
-Internal Changes
-~~~~~~~~~~~~~~~~
-
 .. _whats-new.2025.09.1:
 
 v2025.09.1 (September 29, 2025)
@@ -121,9 +117,6 @@ Bug fixes
 - Allow ``combine_attrs="drop_conflicts"`` to handle objects with ``__eq__`` methods that return
   non-bool values (e.g., numpy arrays) without raising ``ValueError`` (:pull:`10726`).
   By `Maximilian Roos <https://github.com/max-sixty>`_.
-- Fix error raised when writing scalar variables to Zarr with ``region={}``
-  (:pull:`10796`).
-  By `Stephan Hoyer <https://github.com/shoyer>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/core/options.py

@@ -59,7 +59,7 @@ class T_Options(TypedDict):
         enable_cftimeindex: bool
         file_cache_maxsize: int
         keep_attrs: Literal["default"] | bool
-        netcdf_engine_order: Sequence[Literal["h5netcdf", "scipy", "netcdf4"]]
+        netcdf_engine_order: Sequence[Literal["netcdf4", "h5netcdf", "scipy"]]
         warn_for_unclosed_files: bool
         use_bottleneck: bool
         use_flox: bool