From 6bb3f49ba4bcea1942d1b6d891cf2b64b3c0818e Mon Sep 17 00:00:00 2001
From: MUGUNDAN <mugunthan.selvanayagam@multicorewareinc.com>
Date: Mon, 12 Oct 2026 09:50:15 +0530
Subject: [PATCH 1/2] Add CI support for publishing Windows ARM64 Wheels

---
 .github/workflows/wheel.yaml | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/.github/workflows/wheel.yaml b/.github/workflows/wheel.yaml
index d8fa6ab11..a9ac8a512 100644
--- a/.github/workflows/wheel.yaml
+++ b/.github/workflows/wheel.yaml
@@ -20,7 +20,7 @@ jobs:
       fail-fast: false
       matrix:
         # macos-15-large is an intel runner, macos-14 is an arm64 runner
-        os: [ubuntu-latest, ubuntu-22.04-arm, windows-latest, macos-15-large, macos-14]
+        os: [ubuntu-latest, ubuntu-22.04-arm, windows-latest, windows-11-arm, macos-15-large, macos-14]
     env:
       # on free-threaded builds also check that no extension re-enables the GIL
       CIBW_TEST_COMMAND: python -c "import sys, sysconfig, numcodecs; assert not (sysconfig.get_config_var('Py_GIL_DISABLED') and sys._is_gil_enabled())"
@@ -34,6 +34,15 @@ jobs:
         with:
           submodules: true
           fetch-depth: 0  # required for version resolution for nightly wheels
+          
+      # Windows ARM64 builds fail immediately with the default GCC toolchain, 
+      # so use LLVM Clang to build wheels instead.
+      - name: Configure Clang for Windows ARM64 Builds
+        if: matrix.os == 'windows-11-arm'
+        shell: pwsh
+        run: |
+          "CC=clang-cl" >> $env:GITHUB_ENV
+          "CXX=clang-cl" >> $env:GITHUB_ENV
 
       - uses: pypa/cibuildwheel@v3.4.1
 

From 05b4a67c0c679d3d08dbeb7a72fd12d556ced2c3 Mon Sep 17 00:00:00 2001
From: MUGUNDAN <mugunthan.selvanayagam@multicorewareinc.com>
Date: Mon, 12 Oct 2026 11:09:50 +0530
Subject: [PATCH 2/2] Update xfail condition for Windows platform in tests

---
 tests/test_pickles.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tests/test_pickles.py b/tests/test_pickles.py
index fdabd459c..82afb999d 100644
--- a/tests/test_pickles.py
+++ b/tests/test_pickles.py
@@ -1,5 +1,6 @@
 import itertools
 import sys
+import platform
 
 import numpy as np
 import pytest
@@ -51,7 +52,7 @@ def test_repr():
 # https://stackoverflow.com/questions/58194852/modulenotfounderror-no-module-named-numpy-core-multiarray-r
 @pytest.mark.skipif(sys.byteorder != "little", reason="Pickle does not restore byte orders")
 @pytest.mark.xfail(
-    sys.platform == "win32",
+    sys.platform == "win32" and platform.machine().lower() != "arm64",
     reason=(
         "Pickle fails to read w/ Windows carriage return "
         "( https://github.com/zarr-developers/numcodecs/issues/271 )"