Sourced from zstandard's releases.

0.25.0

• PyO3 Rust created upgraded from 0.24 to 0.25. (#273)
• We now use Py_REFCNT(obj) instead of accessing (*obj)->ob_refcnt directly. This fixes a nogil / multi-threaded compile error. (#201, #275)
• A zstandard commit to fix qsort detection on BSD operating systems has been backported. (#272)
• The PYTHON_ZSTANDARD_IMPORT_POLICY environment variable now has leading and trailing whitespace stripped. Values like cffi and cffi are now equivalent to cffi.
• The CI jobs for building wheels have been overhauled to always use cibuildwheel and uv (where possible). This change should be backwards compatible. But wheel building for this project has historically been fragile and there may be unwanted changes. We're optimistic that standardizing on uv (except for musllinux ppc64le and s390x where uv isn't available) will lead to more stability over time.
• CI now runs tests against the wheels we distribute. Previously, we ran tests against a separate build that was theoretically identical. But the builds may have been subtly different, leading to preventable bugs in our wheels. (Enabling this test coverage did not uncover any failures.)
• The pyproject.toml build backend has been switched from setuptools.build_meta:__legacy__ to setuptools.build_meta.
• The setuptools build dependency has been upgraded from <69.0.0 to >=77.0.0. Modern versions of setuptools broke --config-settings=--build-option=... as part of implementing PEP 660. A workaround is to use --config-settings=--global-option=... instead. --global-option apparently is deprecated and the setuptools folks have yet to figure out how to thread config settings into setup.py invocations. (--build-option is sent to the build_wheel command but not the build_editable command.)
• Python 3.14 wheels are now built with manylinux_2_28 (versus manylinux2014) for older Python versions. This may raise the minimum glibc version, effectively dropping support for Debian 8 and 9, Ubuntu 13.10 through 18.04, Fedora 19 to 28, and RHEL/Centos 7. However, in practice most platforms don't container newer glibc symbols and are still ABI compatible with manylinux2014 and glibc 2.17.
• We now require cffi >= 2.0.0b on Python 3.14. <3.14 still requires 1.17. (#274)
• The cffi backend is now automatically disabled for free-threaded builds on Python <3.14, as cffi didn't implement free-threaded support until the 2.0 release. (#274)
• Added CI coverage for free-threaded CPython 3.13 and 3.14. We do not yet formally support free-threaded builds. (#276)
• The C and Rust backends now declare the GIL as unused.
• The pythoncapi_compat.h file has been upgraded to the latest version. (#278)
• setup.py now depends on packaging and uses packaging.version.Version for version comparisons. This removes some deprecation warnings from usage of legacy distutils Version classes.
• Relax run-time libzstd version checking in C extension from exactly 1.5.7 to >=1.5.6. (#254, #267)
• C extension types now (correctly) declare their fully qualified type names

... (truncated)

Sourced from zstandard's changelog.

0.25.0 (released 2025-09-14)

• PyO3 Rust created upgraded from 0.24 to 0.25. (#273)
• We now use Py_REFCNT(obj) instead of accessing (*obj)->ob_refcnt directly. This fixes a nogil / multi-threaded compile error. (#201, #275)
• A zstandard commit to fix qsort detection on BSD operating systems has been backported. (#272)
• The PYTHON_ZSTANDARD_IMPORT_POLICY environment variable now has leading and trailing whitespace stripped. Values like cffi and cffi are now equivalent to cffi.
• The CI jobs for building wheels have been overhauled to always use cibuildwheel and uv (where possible). This change should be backwards compatible. But wheel building for this project has historically been fragile and there may be unwanted changes. We're optimistic that standardizing on uv (except for musllinux ppc64le and s390x where uv isn't available) will lead to more stability over time.
• CI now runs tests against the wheels we distribute. Previously, we ran tests against a separate build that was theoretically identical. But the builds may have been subtly different, leading to preventable bugs in our wheels. (Enabling this test coverage did not uncover any failures.)
• The pyproject.toml build backend has been switched from setuptools.build_meta:__legacy__ to setuptools.build_meta.
• The setuptools build dependency has been upgraded from <69.0.0 to >=77.0.0. Modern versions of setuptools broke --config-settings=--build-option=... as part of implementing PEP 660. A workaround is to use --config-settings=--global-option=...`` instead. --global-optionapparently is deprecated and the setuptools folks have yet to figure out how to thread config settings intosetup.py invocations. (`--build-option is sent to the build_wheel command but not the build_editable command.)
• Python 3.14 wheels are now built with manylinux_2_28 (versus manylinux2014) for older Python versions. This may raise the minimum glibc version, effectively dropping support for Debian 8 and 9, Ubuntu 13.10 through 18.04, Fedora 19 to 28, and RHEL/Centos 7. However, in practice most platforms don't container newer glibc symbols and are still ABI compatible with manylinux2014 and glibc 2.17.
• We now require cffi >= 2.0.0b on Python 3.14. <3.14 still requires 1.17. (#274)
• The cffi backend is now automatically disabled for free-threaded builds on Python <3.14, as cffi didn't implement free-threaded support until the 2.0 release. (#274)
• Added CI coverage for free-threaded CPython 3.13 and 3.14. We do not yet formally support free-threaded builds. (#276)
• The C and Rust backends now declare the GIL as unused.
• The pythoncapi_compat.h file has been upgraded to the latest version. (#278)
• setup.py now depends on packaging and uses packaging.version.Version for version comparisons. This removes some deprecation warnings from usage of legacy distutils Version classes.
• Relax run-time libzstd version checking in C extension from exactly 1.5.7

... (truncated)

• 7a77a75 global: release 0.25.0
• 7935539 rust: cargo upgrade
• bc3074c rust: update dependencies
• 51a277a c-ext: correctly define fully qualified type names to zstandard.*
• 9ccbc39 docs: fix ReST in news.rst
• 58c68a1 zstd: synchronize qsort code with upstream
• 395f693 docs: document existence of compression.zstd in stdlib
• 6967817 docs: update comparisons to other implementations
• e4e829a docs: document new libzstd version constraint behaviors
• 604a65a Relax libzstd version checking
• Additional commits viewable in compare view

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