Add Python 3.15 support

.github/workflows/external-zstd.yml

@@ -61,4 +61,11 @@ jobs:
 
       - name: Build
         run: |
+          # Homebrew's prefix (/opt/homebrew on Apple Silicon) isn't on the
+          # default compiler search paths, and its libzstd is arm64 only, so
+          # don't build the universal2 binary the Python framework asks for.
+          ZSTD_PREFIX="$(brew --prefix zstd)"
+          export CFLAGS="-I${ZSTD_PREFIX}/include"
+          export LDFLAGS="-L${ZSTD_PREFIX}/lib"
+          export ARCHFLAGS="-arch arm64"
           python -m pip install --config-settings=--global-option=--system-zstd .

.github/workflows/test.yml

@@ -29,6 +29,8 @@ jobs:
           - '3.13t'
           - '3.14'
           - '3.14t'
+          - '3.15'
+          - '3.15t'
         arch:
           - 'arm64'
           - 'x86'

.github/workflows/typing.yml

@@ -22,6 +22,8 @@ jobs:
           - '3.13t'
           - '3.14'
           - '3.14t'
+          - '3.15'
+          - '3.15t'
     runs-on: 'ubuntu-24.04'
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1

.github/workflows/wheel.yml

@@ -22,6 +22,8 @@ jobs:
           - 'cp313'
           - 'cp314'
           - 'cp314t'
+          - 'cp315'
+          - 'cp315t'
         arch:
           - 'aarch64'
           - 'i686'
@@ -66,11 +68,19 @@ jobs:
             image: 'manylinux2014'
           - py: 'cp314t'
             image: 'manylinux2014'
+          - py: 'cp315'
+            image: 'manylinux2014'
+          - py: 'cp315t'
+            image: 'manylinux2014'
           # Drop support for musllinux_1_1 on 3.14+
           - py: 'cp314'
             image: 'musllinux_1_1'
           - py: 'cp314t'
             image: 'musllinux_1_1'
+          - py: 'cp315'
+            image: 'musllinux_1_1'
+          - py: 'cp315t'
+            image: 'musllinux_1_1'
     runs-on: ${{ matrix.arch == 'aarch64' && 'ubuntu-24.04-arm' || 'ubuntu-24.04' }}
     env:
       CIBW_ARCHS: ${{ matrix.arch }}
@@ -124,6 +134,8 @@ jobs:
           - 'cp313'
           - 'cp314'
           - 'cp314t'
+          - 'cp315'
+          - 'cp315t'
         arch:
           - 'arm64'
           - 'x86_64'
@@ -164,6 +176,8 @@ jobs:
           - 'cp313'
           - 'cp314'
           - 'cp314t'
+          - 'cp315'
+          - 'cp315t'
         arch:
           - 'win32'
           - 'win_amd64'

Cargo.toml

@@ -26,5 +26,5 @@ version = "2.0.16"
 features = ["experimental", "legacy", "zstdmt"]
 
 [dependencies.pyo3]
-version = "0.25.1"
+version = "0.29.3"
 features = ["extension-module"]

ci/conda/meta.yaml

@@ -1,8 +1,12 @@
-{% set data = load_setup_py_data() %}
+# Don't use load_setup_py_data(): it runs setup.py inside the conda-build
+# process, and setup.py's sys.path.insert(0, ".") then makes the unbuilt
+# zstandard package in the source tree shadow the zstandard bindings that
+# conda-package-handling needs for .conda support.
+{% set version_match = load_file_regex(load_file="../../c-ext/python-zstandard.h", regex_pattern='PYTHON_ZSTANDARD_VERSION "([^"]+)"', from_recipe_dir=True) %}
 
 package:
   name: zstandard
-  version: "{{ data.get('version') }}"
+  version: "{{ version_match.group(1) }}"
 
 source:
   path: ../../

docs/installing.rst

@@ -22,10 +22,10 @@ this package with ``conda``.
 Requirements
 ============
 
-This package is designed to run with Python 3.10, 3.11, 3.12, 3.13, and 3.14
-on common platforms (Linux, Windows, and OS X). On PyPy (both PyPy2 and PyPy3)
-we support version 6.0.0 and above. x86 and x86_64 are well-tested on Windows.
-Only x86_64 is well-tested on Linux and macOS.
+This package is designed to run with Python 3.10, 3.11, 3.12, 3.13, 3.14,
+and 3.15 on common platforms (Linux, Windows, and OS X). On PyPy (both PyPy2
+and PyPy3) we support version 6.0.0 and above. x86 and x86_64 are well-tested
+on Windows. Only x86_64 is well-tested on Linux and macOS.
 
 CFFI Backend
 ============

docs/news.rst

@@ -17,6 +17,15 @@ Backwards Compatibility Notes
 * cibuildwheel upgrade required us to drop generating the CPython 3.13 free-threaded
   wheels.
 
+Changes
+-------
+
+* Python 3.15 support. We build wheels (including free-threaded ``cp315t``
+  wheels) and have CI test coverage. Like 3.14, Linux wheels are built with
+  ``manylinux_2_28`` and ``musllinux_1_2``.
+* PyO3 Rust crate upgraded from 0.25 to 0.29, which is required for
+  Python 3.15 support in the Rust backend.
+
 0.25.0 (released 2025-09-14)
 ============================
 

pyproject.toml

@@ -17,6 +17,7 @@ classifiers = [
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
     "Programming Language :: Python :: 3.14",
+    "Programming Language :: Python :: 3.15",
     "Programming Language :: Python :: Free Threading :: 1 - Unstable",
 ]
 keywords = ["zstandard", "zstd", "compression"]
@@ -42,14 +43,20 @@ requires = [
 build-backend = "setuptools.build_meta"
 
 [dependency-groups]
-dev = [
+# Dependencies needed to run the test suite. cibuildwheel installs this group
+# unlocked inside its build containers, so keep it free of packages (like mypy)
+# without wheels for every platform we build.
+test = [
     "cffi~=1.17; platform_python_implementation != 'PyPy' and python_version < '3.14'",
     "cffi>=2.0.0b; platform_python_implementation != 'PyPy' and python_version >= '3.14'",
     "hypothesis==6.111.0",
-    "mypy>=1.17.1",
     "pytest>=8.4.1",
     "pytest-xdist>=3.8.0",
 ]
+dev = [
+    { include-group = "test" },
+    "mypy>=1.17.1",
+]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
@@ -71,7 +78,7 @@ test-command = [
     "pytest -v --numprocesses=auto",
     "PYTHON_ZSTANDARD_IMPORT_POLICY=cffi pytest -v --numprocesses=auto",
 ]
-test-groups = ["dev"]
+test-groups = ["test"]
 test-sources = ["tests"]
 
 [tool.cibuildwheel.linux]