Add FAQ answer about API stability & backwards compatibility

doc/api.rst

@@ -10,7 +10,7 @@ This page provides an auto-generated summary of xarray's API. For more details
 and examples, refer to the relevant chapters in the main part of the
 documentation.
 
-See also: :ref:`public api`
+See also: :ref:`public api` and :ref:`api stability`.
 
 Top-level functions
 ===================

doc/getting-started-guide/faq.rst

@@ -416,6 +416,18 @@ would certainly appreciate it. We recommend two citations.
                  url    = {https://doi.org/10.5281/zenodo.59499}
                 }
 
+.. _api stability:
+
+How stable is Xarray's API?
+---------------------------
+
+Xarray tries very hard to maintain backwards compatibility in our :ref:`api` between released versions.
+Whilst we do occasionally make breaking changes in order to improve the library,
+we `signpost changes <https://docs.xarray.dev/en/stable/contributing.html#backwards-compatibility>`_ with ``DeprecationWarnings`` for many releases in advance.
+(An exception is bugs - whose behaviour we try to fix as soon as we notice them.)
+Our `test-driven development practices <https://docs.xarray.dev/en/stable/contributing.html#test-driven-development-code-writing>`_ help to ensure any accidental regressions are caught.
+This philosophy applies to everything in the `public API <https://docs.xarray.dev/en/stable/getting-started-guide/faq.html#what-parts-of-xarray-are-considered-public-api>`_.
+
 .. _public api:
 
 What parts of xarray are considered public API?

doc/whats-new.rst

@@ -54,6 +54,8 @@ Bug fixes
 Documentation
 ~~~~~~~~~~~~~
 
+- Clarified xarray's policy on API stability in the FAQ. (:issue:`9854`, :pull:`9855`)
+  By `Tom Nicholas <https://github.com/TomNicholas>`_.
 
 Internal Changes
 ~~~~~~~~~~~~~~~~