diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index ffeb139..62dadc5 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -26,7 +26,7 @@ jobs:
       fail-fast: false
       matrix:
         session: ["tests", "doctests-docs", "doctests-api"]
-        python-version: ["3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13", "3.14"]
         exclude:
           - session: "doctests-docs"
             python-version: "3.10"
@@ -34,12 +34,16 @@ jobs:
             python-version: "3.11"
           - session: "doctests-docs"
             python-version: "3.12"
+          - session: "doctests-docs"
+            python-version: "3.13"
           - session: "doctests-api"
             python-version: "3.10"
           - session: "doctests-api"
             python-version: "3.11"
           - session: "doctests-api"
             python-version: "3.12"
+          - session: "doctests-api"
+            python-version: "3.13"
 
     defaults:
       run:
diff --git a/docs/changelog_fragments/255.bug.rst b/docs/changelog_fragments/255.bug.rst
new file mode 100644
index 0000000..ada4570
--- /dev/null
+++ b/docs/changelog_fragments/255.bug.rst
@@ -0,0 +1 @@
+Fixes to work with Iris >= v3.16 and xarray > v2026.02.
diff --git a/docs/changelog_fragments/258.dev.rst b/docs/changelog_fragments/258.dev.rst
new file mode 100644
index 0000000..d6ba1cf
--- /dev/null
+++ b/docs/changelog_fragments/258.dev.rst
@@ -0,0 +1 @@
+Support and test against Python 3.14.
diff --git a/docs/details/interface_support.rst b/docs/details/interface_support.rst
index 08c95e1..5f0315b 100644
--- a/docs/details/interface_support.rst
+++ b/docs/details/interface_support.rst
@@ -5,7 +5,8 @@ Support for Interfaces and Dependencies
 
 Python Compatibility
 --------------------
-NcData currently supports Python >= 3.10, and is tested against 3.10, 3.11, 3.12 and 3.13.
+NcData currently supports Python >= 3.10, and is tested against
+3.10, 3.11, 3.12, 3.13 and 3.14.
 
 NetCDF4 Compatibility
 ---------------------
diff --git a/docs/userdocs/getting_started/introduction.rst b/docs/userdocs/getting_started/introduction.rst
index 0a4a51d..22d4e81 100644
--- a/docs/userdocs/getting_started/introduction.rst
+++ b/docs/userdocs/getting_started/introduction.rst
@@ -265,9 +265,9 @@ Example code snippets :
     Dimensions:  (dim0: 3)
     Dimensions without coordinates: dim0
     Data variables:
-        vx0      (dim0) int64 ... dask.array<chunksize=(3,), meta=numpy.ma.MaskedArray>
-        vx1      (dim0) int64 ... dask.array<chunksize=(3,), meta=numpy.ma.MaskedArray>
-        v_mag    (dim0) float64 ... dask.array<chunksize=(3,), meta=numpy.ma.MaskedArray>
+        vx0      (dim0) ... dask.array<chunksize=(3,), ...
+        vx1      (dim0) ... dask.array<chunksize=(3,), ...
+        v_mag    (dim0) ... dask.array<chunksize=(3,), ...
     Attributes:
         Conventions:  CF-1.7
 
diff --git a/lib/ncdata/dataset_like.py b/lib/ncdata/dataset_like.py
index 3702f95..4d58410 100644
--- a/lib/ncdata/dataset_like.py
+++ b/lib/ncdata/dataset_like.py
@@ -81,6 +81,11 @@ def __setattr__(self, attr, value):
         else:
             self.setncattr(attr, value)
 
+    def set_auto_chartostring(self, value):
+        if bool(value):
+            msg = "Cannot enable 'auto_chartostring' for Nc4Dataselike or Nc4VariableLike."
+            raise ValueError(msg)
+
 
 class Nc4DatasetLike(_Nc4DatalikeWithNcattrs):
     """
diff --git a/pyproject.toml b/pyproject.toml
index da7d6af..b8d60a7 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -37,6 +37,7 @@ classifiers = [
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
     "Topic :: Scientific/Engineering",
 ]
 dynamic = [
diff --git a/requirements/readthedocs.yml b/requirements/readthedocs.yml
index b7c80df..8570249 100644
--- a/requirements/readthedocs.yml
+++ b/requirements/readthedocs.yml
@@ -12,7 +12,7 @@ dependencies:
   - pip
   - pydata-sphinx-theme
   - pytest
-  - python<3.14
+  - python<3.15
   - sphinx
   - sphinxcontrib-napoleon
   - sphinx-copybutton
diff --git a/tests/__init__.py b/tests/__init__.py
index ac3feab..9d8ecca 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -25,3 +25,24 @@ def __getitem__(self, keys):
         """Fetch indexed data section."""
         self._accesses.append(keys)
         return self._data[keys]
+
+
+def version_tuple(version_string):
+    """Make a comparable tuple from a package version string.
+
+    Allows only the final segment to have non-numeric parts.
+    Returns a tuple of the parts.
+    """
+    parts = version_string.split(".")
+    last_part = parts[-1]
+    while len(last_part) and not last_part[-1].isdigit():
+        last_part = last_part[:-1]
+    if len(last_part):
+        parts[-1] = last_part
+    else:
+        parts = parts[:-1]
+    if any(str(int(part)) != part for part in parts):
+        raise ValueError(
+            f"invalid numerics in version string: {version_string!r}"
+        )
+    return tuple(int(part) for part in parts)
diff --git a/tests/data_testcase_schemas.py b/tests/data_testcase_schemas.py
index 7622da3..8212577 100644
--- a/tests/data_testcase_schemas.py
+++ b/tests/data_testcase_schemas.py
@@ -356,7 +356,7 @@ def _define_iris_testdata_testcases():
         #     "_ORCA2__votemper",
         # ]
         EXCLUDES = []
-        for filepath in _netcdf_testfile_paths:
+        for filepath in sorted(_netcdf_testfile_paths):
             param_name = str(filepath)
             # remove unwanted path elements
             param_name = param_name.replace(str(_testdirpath), "")
@@ -434,7 +434,7 @@ def _define_unit_dtype_testcases():
                     name="vx",
                     dims=["strlen"],
                     dtype="S1",
-                    data=np.array("abc", dtype="S1"),
+                    data=np.array(list("abc"), dtype="S1"),
                 )
             ],
         }
@@ -525,6 +525,7 @@ def standard_testcase(request, session_testdir):
             # """
             "small_rotPole_precipitation",
             "small_FC_167",
+            "test_monotonic_coordinate",
         ],
         # Xarray can save ~anything
         "save": [r"test_monotonic_coordinate"],
diff --git a/tests/integration/test_iris_load_and_save_equivalence.py b/tests/integration/test_iris_load_and_save_equivalence.py
index 238e456..922fe6d 100644
--- a/tests/integration/test_iris_load_and_save_equivalence.py
+++ b/tests/integration/test_iris_load_and_save_equivalence.py
@@ -14,6 +14,7 @@
 from ncdata.netcdf4 import from_nc4, to_nc4
 from ncdata.utils import dataset_differences
 
+from tests import version_tuple
 from tests.data_testcase_schemas import session_testdir, standard_testcase
 from tests.integration.equivalence_testing_utils import (
     adjust_chunks,
@@ -56,12 +57,15 @@ def test_load_direct_vs_viancdata(
         # yet account for this.
         # TODO: fix in Nc4VariableLike, when we are sure of the interpretation
         "label_and_climate__small_FC_167_mon_19601101",
-        # Some of the legacy UGRID unstructured files have incorrect encodings
-        # which are currently causing loading errors in Iris since UGRID loading
-        # became an always-on thing in v3.11
-        "unstructured_grid__theta_nodal_xios",
-        "ugrid__21_triangle_example",
     ]
+    if version_tuple(iris.__version__) < version_tuple("3.13"):
+        # TODO: remove backwards compatibility when we drop Python 3.10 support
+        specific_excludes.extend(
+            [
+                "ugrid__21_triangle_example",
+                "theta_nodal_xios",
+            ]
+        )
     if any(
         name_fragment in standard_testcase.name
         for name_fragment in specific_excludes
@@ -121,10 +125,12 @@ def test_save_direct_vs_viancdata(standard_testcase, tmp_path):
         # Some of the legacy UGRID unstructured files have incorrect encodings
         # which are currently causing loading errors in Iris since UGRID loading
         # became an always-on thing in v3.11
-        "unstructured_grid__theta_nodal_xios",
         "unstructured_grid__mesh_C12",
         "ugrid__21_triangle_example",
     ]
+    if version_tuple(iris.__version__) < version_tuple("3.13"):
+        # TODO: remove backwards compatibility when we drop Python 3.10 support
+        specific_excludes.append("theta_nodal_xios")
     if any(
         name_fragment in standard_testcase.name
         for name_fragment in specific_excludes
diff --git a/tests/integration/test_iris_xarray_roundtrips.py b/tests/integration/test_iris_xarray_roundtrips.py
index d0eb2bf..7554516 100644
--- a/tests/integration/test_iris_xarray_roundtrips.py
+++ b/tests/integration/test_iris_xarray_roundtrips.py
@@ -22,6 +22,7 @@
 from ncdata.utils import dataset_differences
 from ncdata.xarray import from_xarray
 
+from tests import version_tuple
 from tests.data_testcase_schemas import (
     BAD_LOADSAVE_TESTCASES,
     session_testdir,
@@ -70,20 +71,34 @@ def test_roundtrip_ixi(standard_testcase, use_irislock, adjust_chunks):
         + BAD_LOADSAVE_TESTCASES["xarray"]["load"]
         # TODO: remaining unresolved problems ...
         + [
-            # string dimension problem
-            "ds__dtype__string",
             # outstanding dims-mismatch problems.
             "testing__small_theta_colpex",
+            # all-masked variables --> changing dtype, since xarray>v2026.02.0
+            "testing__cell_methods",
             # coordinate attributes on mesh coordinate variables
-            "testdata____unstructured_grid__data_C4",
             "testdata____ugrid__21_triangle_example",
-            # Problem with units on time bounds
-            "label_and_climate__small_FC_167",
             # Broken UGRID files now won't load in Iris >= 3.10
             "unstructured_grid__mesh_C12",
-            "_unstructured_grid__theta_nodal_xios",
+            # **No** mesh files will now roundtrip, since xarray 2026.04.0.
+            # This is because  xarray now normalises the array type when loading
+            # from ncdata, removing masks and converting to nanarrays (thus making ints
+            # into floats).
+            # Previously we could create xarray Datasets with masked integer variables
+            # as data -- though that was alwaysobviously a bit tricksy.
+            # Iris can't accept the new form as it insists on integer types for
+            # mesh connectivities :-(
+            # TODO: do something to get this working again?
+            "unstructured",
         ]
     )
+    if version_tuple(iris.__version__) < version_tuple("3.16"):
+        # TODO: remove backwards compatibility when we drop Python 3.11 support
+        exclude_case_keys.extend(
+            [
+                "ds__dtype__string",
+                "ds__stringvar",
+            ]
+        )
     if any(key in standard_testcase.name for key in exclude_case_keys):
         pytest.skip("excluded testcase")
 
@@ -209,14 +224,6 @@ def test_roundtrip_xix(
         #   float time(time) ;
         #       time:bounds = 'time_bnds'
         #   float time_bnds(time, time_bnds) ;
-        "label_and_climate__small_FC_167",
-        "rotated__xyt__small_rotPole_precipitation",
-        # This one fails to load in xarray, for somewhat unclear reasons
-        #     NotImplementedError: Can not use auto rechunking with object dtype.
-        #     We are unable to estimate the size in bytes of object data
-        "unstructured_grid__lfric_surface_mean",
-        # Iris loses the name of the unstructured dimension, causing multiple problems
-        "unstructured_grid__data_C4",
     ]
     if any(key in standard_testcase.name for key in excluded_casename_keys):
         pytest.skip("excluded testcase")
diff --git a/tests/unit/tests/test_version_tuple.py b/tests/unit/tests/test_version_tuple.py
new file mode 100644
index 0000000..dabdbec
--- /dev/null
+++ b/tests/unit/tests/test_version_tuple.py
@@ -0,0 +1,37 @@
+"""
+Tests for the test utility :func:`tests.version_majorminor`.
+"""
+
+import pytest
+
+from tests import version_tuple
+
+
+def test_empty():
+    assert version_tuple("") == ()
+
+
+def test_basic():
+    assert version_tuple("1.2.3") == (1, 2, 3)
+
+
+def test_one():
+    assert version_tuple("1") == (1,)
+
+
+@pytest.mark.parametrize("tail", ["alpha", ".alpha", "."])
+@pytest.mark.parametrize("base", ["1", "1.2"])
+def test_valid_tails(tail, base):
+    assert version_tuple(base + tail) == version_tuple(base)
+
+
+@pytest.mark.parametrize("version", ["a1.", "1a.2", "a1.2", "1.2a."])
+def test_invalid_nonnumerics(version):
+    with pytest.raises(ValueError, match="invalid"):
+        version_tuple(version)
+
+
+def test_interlength_compares():
+    assert version_tuple("2") > version_tuple("1.99")
+    assert version_tuple("1.2.3") > version_tuple("1.1")
+    assert version_tuple("1.2.3") < version_tuple("1.3")