From 52101003772ece741e114426c12c6ba4407199d5 Mon Sep 17 00:00:00 2001
From: schnellerhase <56360279+schnellerhase@users.noreply.github.com>
Date: Tue, 24 Feb 2026 18:49:07 +0100
Subject: [PATCH 01/15] Add post-install mypy check(s)

---
 .github/workflows/pythonapp.yml | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/pythonapp.yml b/.github/workflows/pythonapp.yml
index aac0403ee..4b87b3be4 100644
--- a/.github/workflows/pythonapp.yml
+++ b/.github/workflows/pythonapp.yml
@@ -152,7 +152,13 @@ jobs:
       - name: Install Python dependencies
         run: pip install nanobind scikit-build-core[pyproject]
       - name: Install Basix
-        run: pip install --no-build-isolation .
+        run: pip install --no-build-isolation -e .
+      - name: Run mypy (module)
+        run: mypy -p basix
+      - name: Run mypy (test)
+        run: mypy test
+      - name: Run mypy (demo)
+        run: mypy demo/python
 
   build-cmake:
     name: Build using C++ and Python parts separately and run tests

From ca2f162b3151675908132ec8b37d53b15afc13d2 Mon Sep 17 00:00:00 2001
From: schnellerhase <56360279+schnellerhase@users.noreply.github.com>
Date: Tue, 24 Feb 2026 18:51:17 +0100
Subject: [PATCH 02/15] Install mypy

---
 .github/workflows/pythonapp.yml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/.github/workflows/pythonapp.yml b/.github/workflows/pythonapp.yml
index 4b87b3be4..f82f65ad2 100644
--- a/.github/workflows/pythonapp.yml
+++ b/.github/workflows/pythonapp.yml
@@ -153,6 +153,8 @@ jobs:
         run: pip install nanobind scikit-build-core[pyproject]
       - name: Install Basix
         run: pip install --no-build-isolation -e .
+      - name: Install mypy
+        run: pip install mypy
       - name: Run mypy (module)
         run: mypy -p basix
       - name: Run mypy (test)

From 87c237bb6403c5136fa7ac588037f36213440ebd Mon Sep 17 00:00:00 2001
From: schnellerhase <56360279+schnellerhase@users.noreply.github.com>
Date: Tue, 24 Feb 2026 18:56:02 +0100
Subject: [PATCH 03/15] No demo

---
 .github/workflows/pythonapp.yml | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/pythonapp.yml b/.github/workflows/pythonapp.yml
index f82f65ad2..53018ea07 100644
--- a/.github/workflows/pythonapp.yml
+++ b/.github/workflows/pythonapp.yml
@@ -159,8 +159,8 @@ jobs:
         run: mypy -p basix
       - name: Run mypy (test)
         run: mypy test
-      - name: Run mypy (demo)
-        run: mypy demo/python
+      # - name: Run mypy (demo)
+      #   run: mypy demo/python
 
   build-cmake:
     name: Build using C++ and Python parts separately and run tests

From d4125a52ff872d6ff7341e23604682d443c7470d Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 11:19:00 +0100
Subject: [PATCH 04/15] Fix all errors except one

---
 python/basix/finite_element.py |  4 ++--
 python/basix/ufl.py            | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/python/basix/finite_element.py b/python/basix/finite_element.py
index c3e4fe7f7..c3783203a 100644
--- a/python/basix/finite_element.py
+++ b/python/basix/finite_element.py
@@ -548,7 +548,7 @@ def wcoeffs(self) -> npt.ArrayLike:
         return self._e.wcoeffs
 
     @property
-    def M(self) -> list[list[npt.NDArray]]:
+    def M(self) -> list[list[typing.Annotated[npt.ArrayLike, dict(writable=False)]]]:
         """Interpolation matrices for each sub-entity.
 
         See C++ documentation for details.
@@ -556,7 +556,7 @@ def M(self) -> list[list[npt.NDArray]]:
         return self._e.M
 
     @property
-    def x(self) -> list[list[npt.NDArray]]:
+    def x(self) -> list[list[typing.Annotated[npt.ArrayLike, dict(writable=False)]]]:
         """Interpolation points for each sub-entity.
 
         The indices of this data are ``(tdim, entity index, point index,
diff --git a/python/basix/ufl.py b/python/basix/ufl.py
index 2ba6f599f..4ccaba6ee 100644
--- a/python/basix/ufl.py
+++ b/python/basix/ufl.py
@@ -358,12 +358,12 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         raise NotImplementedError()
 
     @property
-    def _x(self) -> list[list[_npt.NDArray]]:
+    def _x(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
         """The points used to define interpolation."""
         raise NotImplementedError()
 
     @property
-    def _M(self) -> list[list[_npt.NDArray]]:
+    def _M(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
         """The matrices used to define interpolation."""
         raise NotImplementedError()
 
@@ -555,11 +555,11 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         return self._element.wcoeffs
 
     @property
-    def _x(self) -> list[list[_npt.NDArray]]:
+    def _x(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
         return self._element.x
 
     @property
-    def _M(self) -> list[list[_npt.NDArray]]:
+    def _M(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
         return self._element.M
 
     @property
@@ -1182,11 +1182,11 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         return wcoeffs
 
     @property
-    def _x(self) -> list[list[_npt.NDArray]]:
+    def _x(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
         return self._sub_element._x
 
     @property
-    def _M(self) -> list[list[_npt.NDArray]]:
+    def _M(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
         M = []
         for M_list in self._sub_element._M:
             M_row = []

From d75a8615d2f33d126f94f056e97481b36c7fe32a Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 11:19:58 +0100
Subject: [PATCH 05/15] Get that error triggering in CI

---
 .github/workflows/pythonapp.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/.github/workflows/pythonapp.yml b/.github/workflows/pythonapp.yml
index 53018ea07..b0db1a7e1 100644
--- a/.github/workflows/pythonapp.yml
+++ b/.github/workflows/pythonapp.yml
@@ -152,7 +152,7 @@ jobs:
       - name: Install Python dependencies
         run: pip install nanobind scikit-build-core[pyproject]
       - name: Install Basix
-        run: pip install --no-build-isolation -e .
+        run: pip install --no-build-isolation .
       - name: Install mypy
         run: pip install mypy
       - name: Run mypy (module)

From 418acc6c7a4684697236216ac8232975000346fa Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 11:26:35 +0100
Subject: [PATCH 06/15] Backout

---
 python/basix/finite_element.py |  4 ++--
 python/basix/ufl.py            | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/python/basix/finite_element.py b/python/basix/finite_element.py
index c3783203a..c3e4fe7f7 100644
--- a/python/basix/finite_element.py
+++ b/python/basix/finite_element.py
@@ -548,7 +548,7 @@ def wcoeffs(self) -> npt.ArrayLike:
         return self._e.wcoeffs
 
     @property
-    def M(self) -> list[list[typing.Annotated[npt.ArrayLike, dict(writable=False)]]]:
+    def M(self) -> list[list[npt.NDArray]]:
         """Interpolation matrices for each sub-entity.
 
         See C++ documentation for details.
@@ -556,7 +556,7 @@ def M(self) -> list[list[typing.Annotated[npt.ArrayLike, dict(writable=False)]]]
         return self._e.M
 
     @property
-    def x(self) -> list[list[typing.Annotated[npt.ArrayLike, dict(writable=False)]]]:
+    def x(self) -> list[list[npt.NDArray]]:
         """Interpolation points for each sub-entity.
 
         The indices of this data are ``(tdim, entity index, point index,
diff --git a/python/basix/ufl.py b/python/basix/ufl.py
index 4ccaba6ee..2ba6f599f 100644
--- a/python/basix/ufl.py
+++ b/python/basix/ufl.py
@@ -358,12 +358,12 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         raise NotImplementedError()
 
     @property
-    def _x(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
+    def _x(self) -> list[list[_npt.NDArray]]:
         """The points used to define interpolation."""
         raise NotImplementedError()
 
     @property
-    def _M(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
+    def _M(self) -> list[list[_npt.NDArray]]:
         """The matrices used to define interpolation."""
         raise NotImplementedError()
 
@@ -555,11 +555,11 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         return self._element.wcoeffs
 
     @property
-    def _x(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
+    def _x(self) -> list[list[_npt.NDArray]]:
         return self._element.x
 
     @property
-    def _M(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
+    def _M(self) -> list[list[_npt.NDArray]]:
         return self._element.M
 
     @property
@@ -1182,11 +1182,11 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         return wcoeffs
 
     @property
-    def _x(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
+    def _x(self) -> list[list[_npt.NDArray]]:
         return self._sub_element._x
 
     @property
-    def _M(self) -> list[list[_typing.Annotated[_npt.ArrayLike, dict(writable=False)]]]:
+    def _M(self) -> list[list[_npt.NDArray]]:
         M = []
         for M_list in self._sub_element._M:
             M_row = []

From 81b322e6ccee43f64f64f51185db7039888b03d8 Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 11:39:57 +0100
Subject: [PATCH 07/15] Remove INSTALL_TIME, not needed.

---
 python/CMakeLists.txt | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index 8a946a2e3..d37587b3b 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -112,15 +112,15 @@ else()
   set_target_properties(_basixcpp PROPERTIES INSTALL_RPATH ${_basix_dir})
 endif()
 
-install(TARGETS _basixcpp LIBRARY DESTINATION basix)
-
 # and the nanobind typing stubs.
 nanobind_add_stub(
   _basixcpp_stub
   MODULE basix._basixcpp
   DEPENDS _basixcpp
   VERBOSE
-  INSTALL_TIME
   OUTPUT
-    basix/_basixcpp.pyi
+    _basixcpp.pyi
 )
+
+install(TARGETS _basixcpp LIBRARY DESTINATION basix)
+install(FILES ${CMAKE_CURRENT_BINARY_DIR}/_basixcpp.pyi DESTINATION basix)

From 51ce838bc7cf5d87013b04343eaf1071b8e253df Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 11:41:28 +0100
Subject: [PATCH 08/15] Apply pattern file - doesn't match, but at least it
 applies.

---
 python/CMakeLists.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index d37587b3b..6134905cb 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -117,6 +117,7 @@ nanobind_add_stub(
   _basixcpp_stub
   MODULE basix._basixcpp
   DEPENDS _basixcpp
+  PATTERN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/pattern_stub.txt
   VERBOSE
   OUTPUT
     _basixcpp.pyi

From 78f5bbdead9b3c91d40b136fd530b10111a160a3 Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 11:48:41 +0100
Subject: [PATCH 09/15] Fix isolated install

---
 pyproject.toml        | 2 +-
 python/CMakeLists.txt | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/pyproject.toml b/pyproject.toml
index ae09da0aa..cf48e48fe 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["scikit-build-core[pyproject]>=0.10.0", "nanobind>=2.5.0"]
+requires = ["scikit-build-core[pyproject]>=0.10.0", "nanobind>=2.5.0", "numpy"]
 build-backend = "scikit_build_core.build"
 
 [project]
diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index 6134905cb..5030e0ade 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -115,7 +115,8 @@ endif()
 # and the nanobind typing stubs.
 nanobind_add_stub(
   _basixcpp_stub
-  MODULE basix._basixcpp
+  MODULE _basixcpp
+  PYTHON_PATH $<TARGET_FILE_DIR:_basixcpp>
   DEPENDS _basixcpp
   PATTERN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/pattern_stub.txt
   VERBOSE

From 3ae73cf458f5ccaa8163302483fab8aa2e0de17c Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 11:49:16 +0100
Subject: [PATCH 10/15] numpy not needed

---
 pyproject.toml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pyproject.toml b/pyproject.toml
index cf48e48fe..ae09da0aa 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["scikit-build-core[pyproject]>=0.10.0", "nanobind>=2.5.0", "numpy"]
+requires = ["scikit-build-core[pyproject]>=0.10.0", "nanobind>=2.5.0"]
 build-backend = "scikit_build_core.build"
 
 [project]

From e3ab5cd64afa1ba6cec33b35ea9d026625567647 Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 12:12:46 +0100
Subject: [PATCH 11/15] Windows 'static linking' requires INSTALL_TIME

---
 python/CMakeLists.txt | 42 ++++++++++++++++++++++++++++--------------
 1 file changed, 28 insertions(+), 14 deletions(-)

diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index 5030e0ade..8d351411b 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -7,7 +7,7 @@ endif()
 
 project(basix_nanobind VERSION "0.9.0.0" LANGUAGES CXX)
 
-if (WIN32)
+if(WIN32)
     # Windows requires all symbols to be manually exported.
     # This flag exports all symbols automatically, as in Unix.
     set(CMAKE_WINDOWS_EXPORT_ALL_SYMBOLS TRUE)
@@ -113,16 +113,30 @@ else()
 endif()
 
 # and the nanobind typing stubs.
-nanobind_add_stub(
-  _basixcpp_stub
-  MODULE _basixcpp
-  PYTHON_PATH $<TARGET_FILE_DIR:_basixcpp>
-  DEPENDS _basixcpp
-  PATTERN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/pattern_stub.txt
-  VERBOSE
-  OUTPUT
-    _basixcpp.pyi
-)
-
-install(TARGETS _basixcpp LIBRARY DESTINATION basix)
-install(FILES ${CMAKE_CURRENT_BINARY_DIR}/_basixcpp.pyi DESTINATION basix)
+if (WIN32)
+  install(TARGETS _basixcpp LIBRARY DESTINATION basix)
+  nanobind_add_stub(
+    _basixcpp_stub
+    MODULE basix._basixcpp
+    DEPENDS _basixcpp
+    INSTALL_TIME
+    PATTERN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/pattern_stub.txt
+    VERBOSE
+    OUTPUT
+      basix/_basixcpp.pyi
+  )
+else()
+  nanobind_add_stub(
+    _basixcpp_stub
+    MODULE _basixcpp
+    PYTHON_PATH $<TARGET_FILE_DIR:_basixcpp>
+    DEPENDS _basixcpp
+    PATTERN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/pattern_stub.txt
+    VERBOSE
+    OUTPUT
+      _basixcpp.pyi
+  )
+
+  install(TARGETS _basixcpp LIBRARY DESTINATION basix)
+  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/_basixcpp.pyi DESTINATION basix)
+endif()

From f43ae2192812955bf055d8b7622dc5c1e3fb43cc Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 14:16:28 +0100
Subject: [PATCH 12/15] Comments - it's a bit complicated!

---
 python/CMakeLists.txt | 18 ++++++++++++++++--
 python/basix/py.typed |  0
 2 files changed, 16 insertions(+), 2 deletions(-)
 delete mode 100644 python/basix/py.typed

diff --git a/python/CMakeLists.txt b/python/CMakeLists.txt
index 8d351411b..54f5600d1 100644
--- a/python/CMakeLists.txt
+++ b/python/CMakeLists.txt
@@ -114,29 +114,43 @@ endif()
 
 # and the nanobind typing stubs.
 if (WIN32)
+  # On Windows we cannot import basix._basixcpp without installing the package
+  # alongside its external dlls.
+
+  # This *must* be called prior to nanobind_add_stub
   install(TARGETS _basixcpp LIBRARY DESTINATION basix)
+  # nanobind automatically installs into ${CMAKE_INSTALL_PREFIX} in
+  # INSTALL_TIME mode.
+  # DEPENDS is redundant in INSTALL_TIME mode - _basixcpp must be installed.
   nanobind_add_stub(
     _basixcpp_stub
     MODULE basix._basixcpp
-    DEPENDS _basixcpp
     INSTALL_TIME
     PATTERN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/pattern_stub.txt
+    MARKER_FILE basix/py.typed
     VERBOSE
     OUTPUT
       basix/_basixcpp.pyi
   )
 else()
+  # On UNIX-like systems we can import the cpp compiled module before
+  # installing and rely on dynamic linking at import time.
   nanobind_add_stub(
     _basixcpp_stub
     MODULE _basixcpp
     PYTHON_PATH $<TARGET_FILE_DIR:_basixcpp>
     DEPENDS _basixcpp
     PATTERN_FILE ${CMAKE_CURRENT_SOURCE_DIR}/pattern_stub.txt
+    MARKER_FILE ${CMAKE_CURRENT_SOURCE_DIR}/basix/py.typed
     VERBOSE
     OUTPUT
       _basixcpp.pyi
   )
 
   install(TARGETS _basixcpp LIBRARY DESTINATION basix)
-  install(FILES ${CMAKE_CURRENT_BINARY_DIR}/_basixcpp.pyi DESTINATION basix)
+  install(FILES
+    ${CMAKE_CURRENT_SOURCE_DIR}/basix/py.typed
+    ${CMAKE_CURRENT_BINARY_DIR}/_basixcpp.pyi
+    DESTINATION basix
+  )
 endif()
diff --git a/python/basix/py.typed b/python/basix/py.typed
deleted file mode 100644
index e69de29bb..000000000

From fc1de2f3658da65dbd5b61cde876f5e98eb14a55 Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 15:21:00 +0100
Subject: [PATCH 13/15] Remove trivial return types

---
 python/pattern_stub.txt | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/python/pattern_stub.txt b/python/pattern_stub.txt
index 24d5707f6..10c317831 100644
--- a/python/pattern_stub.txt
+++ b/python/pattern_stub.txt
@@ -1,2 +1,7 @@
-basix._basixcpp.tabulate_polynomial_set:
-    def tabulate_polynomial_set(celltype: CellType, polytype: PolysetType, d: int, n: int, x: Annotated[ArrayLike, dict(dtype='float64', writable=False, shape=(None, None), order='C')]) -> Annotated[ArrayLike, dict(dtype='float64', )]: ...
\ No newline at end of file
+tabulate_polynomial_set:
+    \from typing import TypeVar
+    \from numpy.typing import NDArray as _NDArray
+    \from numpy import float32 as _f32, float64 as _f64
+    _polynomial_set_floats = TypeVar("_polynomial_set_floats", _f32, _f64)
+
+    def tabulate_polynomial_set(celltype: CellType, polytype: PolysetType, d: int, n: int, x: _NDArray[_polynomial_set_floats],) -> _NDArray[_polynomial_set_floats]: ...

From 54d852e7cdedffbebbe3ef2f002080721417d89a Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 15:34:53 +0100
Subject: [PATCH 14/15] Fix typing

---
 python/basix/finite_element.py |  4 ++--
 python/basix/ufl.py            | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/python/basix/finite_element.py b/python/basix/finite_element.py
index c3e4fe7f7..a088d2749 100644
--- a/python/basix/finite_element.py
+++ b/python/basix/finite_element.py
@@ -548,7 +548,7 @@ def wcoeffs(self) -> npt.ArrayLike:
         return self._e.wcoeffs
 
     @property
-    def M(self) -> list[list[npt.NDArray]]:
+    def M(self) -> list[list[npt.ArrayLike]]:
         """Interpolation matrices for each sub-entity.
 
         See C++ documentation for details.
@@ -556,7 +556,7 @@ def M(self) -> list[list[npt.NDArray]]:
         return self._e.M
 
     @property
-    def x(self) -> list[list[npt.NDArray]]:
+    def x(self) -> list[list[npt.ArrayLike]]:
         """Interpolation points for each sub-entity.
 
         The indices of this data are ``(tdim, entity index, point index,
diff --git a/python/basix/ufl.py b/python/basix/ufl.py
index 2ba6f599f..998d157cc 100644
--- a/python/basix/ufl.py
+++ b/python/basix/ufl.py
@@ -358,12 +358,12 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         raise NotImplementedError()
 
     @property
-    def _x(self) -> list[list[_npt.NDArray]]:
+    def _x(self) -> list[list[_npt.ArrayLike]]:
         """The points used to define interpolation."""
         raise NotImplementedError()
 
     @property
-    def _M(self) -> list[list[_npt.NDArray]]:
+    def _M(self) -> list[list[_npt.ArrayLike]]:
         """The matrices used to define interpolation."""
         raise NotImplementedError()
 
@@ -555,11 +555,11 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         return self._element.wcoeffs
 
     @property
-    def _x(self) -> list[list[_npt.NDArray]]:
+    def _x(self) -> list[list[_npt.ArrayLike]]:
         return self._element.x
 
     @property
-    def _M(self) -> list[list[_npt.NDArray]]:
+    def _M(self) -> list[list[_npt.ArrayLike]]:
         return self._element.M
 
     @property
@@ -1182,11 +1182,11 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         return wcoeffs
 
     @property
-    def _x(self) -> list[list[_npt.NDArray]]:
+    def _x(self) -> list[list[_npt.ArrayLike]]:
         return self._sub_element._x
 
     @property
-    def _M(self) -> list[list[_npt.NDArray]]:
+    def _M(self) -> list[list[_npt.ArrayLike]]:
         M = []
         for M_list in self._sub_element._M:
             M_row = []

From ce8313cc6ed673af5170839702bf29dafe9166ea Mon Sep 17 00:00:00 2001
From: "Jack S. Hale" <mail@jackhale.co.uk>
Date: Wed, 25 Feb 2026 15:45:56 +0100
Subject: [PATCH 15/15] Revert - mysterious how it works in CI and not locally

---
 python/basix/finite_element.py |  4 ++--
 python/basix/ufl.py            | 12 ++++++------
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/python/basix/finite_element.py b/python/basix/finite_element.py
index a088d2749..c3e4fe7f7 100644
--- a/python/basix/finite_element.py
+++ b/python/basix/finite_element.py
@@ -548,7 +548,7 @@ def wcoeffs(self) -> npt.ArrayLike:
         return self._e.wcoeffs
 
     @property
-    def M(self) -> list[list[npt.ArrayLike]]:
+    def M(self) -> list[list[npt.NDArray]]:
         """Interpolation matrices for each sub-entity.
 
         See C++ documentation for details.
@@ -556,7 +556,7 @@ def M(self) -> list[list[npt.ArrayLike]]:
         return self._e.M
 
     @property
-    def x(self) -> list[list[npt.ArrayLike]]:
+    def x(self) -> list[list[npt.NDArray]]:
         """Interpolation points for each sub-entity.
 
         The indices of this data are ``(tdim, entity index, point index,
diff --git a/python/basix/ufl.py b/python/basix/ufl.py
index 998d157cc..2ba6f599f 100644
--- a/python/basix/ufl.py
+++ b/python/basix/ufl.py
@@ -358,12 +358,12 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         raise NotImplementedError()
 
     @property
-    def _x(self) -> list[list[_npt.ArrayLike]]:
+    def _x(self) -> list[list[_npt.NDArray]]:
         """The points used to define interpolation."""
         raise NotImplementedError()
 
     @property
-    def _M(self) -> list[list[_npt.ArrayLike]]:
+    def _M(self) -> list[list[_npt.NDArray]]:
         """The matrices used to define interpolation."""
         raise NotImplementedError()
 
@@ -555,11 +555,11 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         return self._element.wcoeffs
 
     @property
-    def _x(self) -> list[list[_npt.ArrayLike]]:
+    def _x(self) -> list[list[_npt.NDArray]]:
         return self._element.x
 
     @property
-    def _M(self) -> list[list[_npt.ArrayLike]]:
+    def _M(self) -> list[list[_npt.NDArray]]:
         return self._element.M
 
     @property
@@ -1182,11 +1182,11 @@ def _wcoeffs(self) -> _npt.ArrayLike:
         return wcoeffs
 
     @property
-    def _x(self) -> list[list[_npt.ArrayLike]]:
+    def _x(self) -> list[list[_npt.NDArray]]:
         return self._sub_element._x
 
     @property
-    def _M(self) -> list[list[_npt.ArrayLike]]:
+    def _M(self) -> list[list[_npt.NDArray]]:
         M = []
         for M_list in self._sub_element._M:
             M_row = []