Use Python 3.15b2 for now until cibuildwheel is updated (#2433)

* Use Python 3.15b2 for now until cibuildwheel is updated

There actually *was* an ABI change in the thread_state struct
(adding a field) and Cython grabs `current_exception` from it directly
breaking Cython builds running on 3.15b4 but build prior to it.

There is no fix other than building with 3.15b4 but since cibuildwheel
is still on b2 the only "fix" is to pin to b2 for now (b3 would work
as well to be fair).

This *will* of course segfault again as soon as cibuildwheel is bumped
to b4+ and then we can remove the precise `b2` versioning for
setup-python.

I am trying to re-activate the windows 3.15 builds, IIRC they were
failing and skipped, so lets see.

* Remove windows 3.15 runs again (at least until using NumPy wheels)

(cherry picked from commit 3ef82d6)

Author: seberg

.github/workflows/build-wheel.yml

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 #
 # SPDX-License-Identifier: Apache-2.0
 
@@ -227,10 +227,19 @@ jobs:
         id: setup-python2
         uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1  # v6.3.0
         with:
+<<<<<<< HEAD
           # workaround for actions/runner-images#12377 (the cached 3.13.4 is buggy on Windows)
           python-version: ${{ matrix.python-version == '3.13' && '3.13.5' || matrix.python-version }}
           # allow prereleases only fetches prereleases for unreleased versions of Python
           allow-prereleases: true
+=======
+          # TODO: Pin beta.2 precisely until cibuildwheel catches up (b4 broke ABI for Cython);
+          # this precise pin requires the explicit `freethreaded`.
+          # When 3.15 is officially supported we can also remove the `allow-prereleases` override.
+          python-version: ${{ startsWith(matrix.python-version, '3.15') && '3.15.0-beta.2' || matrix.python-version }}
+          freethreaded: ${{ endsWith(matrix.python-version, 't') }}
+          allow-prereleases: ${{ startsWith(matrix.python-version, '3.15') }}
+>>>>>>> 3ef82d6892d (Use Python 3.15b2 for now until cibuildwheel is updated (#2433))
 
       - name: verify free-threaded build
         if: endsWith(matrix.python-verison, 't')

.github/workflows/test-wheel-linux.yml

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 #
 # SPDX-License-Identifier: Apache-2.0
 
@@ -214,8 +214,17 @@ jobs:
       - name: Set up Python ${{ matrix.PY_VER }}
         uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1  # v6.3.0
         with:
+<<<<<<< HEAD
           python-version: ${{ matrix.PY_VER }}
           allow-prereleases: true
+=======
+          # TODO: Pin beta.2 precisely until cibuildwheel catches up (b4 broke ABI for Cython)
+          # this precise pin requires the explicit `freethreaded`.
+          # When 3.15 is officially supported we can also remove the `allow-prereleases` override.
+          python-version: ${{ startsWith(matrix.PY_VER, '3.15') && '3.15.0-beta.2' || matrix.PY_VER }}
+          freethreaded: ${{ endsWith(matrix.PY_VER, 't') }}
+          allow-prereleases: ${{ startsWith(matrix.PY_VER, '3.15') }}
+>>>>>>> 3ef82d6892d (Use Python 3.15b2 for now until cibuildwheel is updated (#2433))
         env:
           # we use self-hosted runners on which setup-python behaves weirdly...
           AGENT_TOOLSDIRECTORY: "/opt/hostedtoolcache"

.github/workflows/test-wheel-windows.yml

@@ -1,4 +1,4 @@
-# SPDX-FileCopyrightText: Copyright (c) 2024-2025 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+# SPDX-FileCopyrightText: Copyright (c) 2024-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
 #
 # SPDX-License-Identifier: Apache-2.0
 
@@ -204,8 +204,26 @@ jobs:
       - name: Set up Python ${{ matrix.PY_VER }}
         uses: actions/setup-python@ece7cb06caefa5fff74198d8649806c4678c61a1  # v6.3.0
         with:
+<<<<<<< HEAD
           python-version: ${{ matrix.PY_VER }}
           allow-prereleases: true
+=======
+          # TODO: Pin beta.2 precisely until cibuildwheel catches up (b4 broke ABI for Cython)
+          # this precise pin requires the explicit `freethreaded`.
+          # When 3.15 is officially supported we can also remove the `allow-prereleases` override.
+          python-version: ${{ startsWith(matrix.PY_VER, '3.15') && '3.15.0-beta.2' || matrix.PY_VER }}
+          freethreaded: ${{ endsWith(matrix.PY_VER, 't') }}
+          allow-prereleases: ${{ startsWith(matrix.PY_VER, '3.15') }}
+
+      - name: Verify LongPathsEnabled
+        run: |
+          $val = (Get-ItemProperty -Path 'HKLM:\SYSTEM\CurrentControlSet\Control\FileSystem' -Name 'LongPathsEnabled').LongPathsEnabled
+          echo "LongPathsEnabled = $val"
+          if ($val -ne 1) {
+            echo "::error::LongPathsEnabled is not set to 1 (see issue #1820)"
+            exit 1
+          }
+>>>>>>> 3ef82d6892d (Use Python 3.15b2 for now until cibuildwheel is updated (#2433))
 
       - name: Set up mini CTK
         if: ${{ matrix.LOCAL_CTK == '1' }}