Sourced from pip's changelog.

26.1 (2026年04月26日)

Deprecations and Removals

• Drop support for Python 3.9. ([#13795](https://github.com/pypa/pip/issues/13795) <https://github.com/pypa/pip/issues/13795>_)

Features

• Add experimental support to read requirements from standardized pylock.toml files (-r pylock.toml). ([#13876](https://github.com/pypa/pip/issues/13876) <https://github.com/pypa/pip/issues/13876>_)
• Allow --uploaded-prior-to to accept a duration in days (e.g., P3D for 3 days ago). ([#13674](https://github.com/pypa/pip/issues/13674) <https://github.com/pypa/pip/issues/13674>_)

Enhancements

• Speed up dependency resolution when there are complex conflicts. ([#13859](https://github.com/pypa/pip/issues/13859) <https://github.com/pypa/pip/issues/13859>_)
• Reduce memory usage when resolving large dependency trees. ([#13843](https://github.com/pypa/pip/issues/13843) <https://github.com/pypa/pip/issues/13843>_)
• Emit a deprecation warning when pip imports an unexpected module after installation of a distribution has started. ([#13912](https://github.com/pypa/pip/issues/13912) <https://github.com/pypa/pip/issues/13912>_)
• Allow URL constraints to apply to requirements with extras. ([#12018](https://github.com/pypa/pip/issues/12018) <https://github.com/pypa/pip/issues/12018>_)
• Allow unpinned requirements to use hashes from constraints. Constraints like {name}=={version} --hash=... feeds into hash verification for a corresponding requirement. ([#9243](https://github.com/pypa/pip/issues/9243) <https://github.com/pypa/pip/issues/9243>_)
• Improve conflict reports that involve direct URLs. ([#13932](https://github.com/pypa/pip/issues/13932) <https://github.com/pypa/pip/issues/13932>_)
• Show all errors instead of first error for faulty dependency_groups definitions. ([#13917](https://github.com/pypa/pip/issues/13917) <https://github.com/pypa/pip/issues/13917>_)

Bug Fixes

• Fix recovery hint for missing RECORD file to use --ignore-installed instead of --force-reinstall. ([#12645](https://github.com/pypa/pip/issues/12645) <https://github.com/pypa/pip/issues/12645>_)
• Fix misleading error message when a constraint file cannot be opened. ([#13226](https://github.com/pypa/pip/issues/13226) <https://github.com/pypa/pip/issues/13226>_)
• Show the filename rather than the full URL when downloading files from non-PyPI indexes in non-verbose mode. ([#13494](https://github.com/pypa/pip/issues/13494) <https://github.com/pypa/pip/issues/13494>_)
• Remove the adjacent __pycache__ directory when a .py file is removed. ([#13725](https://github.com/pypa/pip/issues/13725) <https://github.com/pypa/pip/issues/13725>_)
• Force UTF-8 encoding for :pep:723 metadata. ([#13861](https://github.com/pypa/pip/issues/13861) <https://github.com/pypa/pip/issues/13861>_)
• Minor performance improvement when filtering candidates during resolution. ([#13916](https://github.com/pypa/pip/issues/13916) <https://github.com/pypa/pip/issues/13916>_)
• Fix a hang on Windows when stdout is closed during verbose output. ([#13927](https://github.com/pypa/pip/issues/13927) <https://github.com/pypa/pip/issues/13927>_)
• Common path prefixes are determined by path segment, not character by character. ([#13847](https://github.com/pypa/pip/issues/13847) <https://github.com/pypa/pip/issues/13847>_)
• Fix installing .tar.gz source distributions that look like a zip file. ([#13867](https://github.com/pypa/pip/issues/13867) <https://github.com/pypa/pip/issues/13867>_)

Vendored Libraries

• Upgrade certifi to 2026年2月25日
• Upgrade packaging to 26.2
• Upgrade requests to 2.33.1
• Upgrade tomli to 2.3.1
• Upgrade urllib3 to 2.6.3

... (truncated)

• 90b2b3e Bump for release
• 193f289 Update AUTHORS.txt
• 63c3709 Merge pull request #13876 from sbidoul/install-from-pylock-reqs-sbi
• e5fe702 Merge pull request #13949 from pypa/revert-13888-resolver-editable-links
• 122a14a Revert "Allow editable installs to satisfy direct-URL dependencies (#13888)"
• c335252 -r pylock.toml: add pip-wheel -r pylock.toml test
• ba2fc12 -r pylock.toml: proper error with remote pylock.toml containing directory ent...
• 747c4ae Merge pull request #13948 from ichard26/reword-news
• 3517841 -r pylock: refine filename pylock-ness test
• 2f7ad8c -r pylock.toml: fix crash with pip wheel and pip lock
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