pipenv 2026.9.0 on Python PyPI

🤖 AI-Generated Changelog

pipenv sync --clean: New flag to automatically uninstall packages that are present in the environment but missing from the lockfile, keeping environments in sync with declared dependencies
Pure-Python resolver backend: New experimental --backend CLI flag and [pipenv] resolver_backend Pipfile setting to opt into an alternative pure-Python dependency resolver (Initiative G), featuring:
- PEP 517 isolated environment builds for sdist metadata extraction
- PEP 658 metadata fetching with wheel-head fallback
- Parallel wheel pre-fetch before installation (~30% cold-install speedup)
- Transitive marker propagation via Requirement.introducing_marker
- Hash collection from all distfile siblings
- Yanked release support per PEP 592
Per-package config settings: pipenv install now persists configuration settings on a per-package basis, isolating options between packages

Pipfile package name recasing is now opt-in via [pipenv] package_name_case Pipfile setting (previously controlled by PIPENV_RECASE_PIPFILE env var); recasing is disabled by default for performance
virtualenv minimum version raised to >=21.14.6
Resolver round cap raised to pip's 200_000 to handle complex dependency graphs

Requirements export: PyPI mirror selection is now honored when exporting requirements, fixing cases where the configured mirror was ignored
Dependency markers: not in exclusions for python_version are no longer incorrectly collapsed; legacy not in exclusions are preserved exactly, and == version groups are version-sorted
pipenv sync --dry-run: No longer uninstalls packages; all lockfile sections are preserved during dry runs
pipenv --envs: Fixed broken documentation URL to point to a valid page
Redundant --upgrade flag dropped from pip install calls during sync
sdist archive names are now sanitized and urllib3 timeouts are applied correctly
Effective resolver backend is now included in the resolution cache key, preventing stale cache hits across backend switches
Pure-Python resolver now correctly threads extras through find_matches/get_dependencies and applies pip's narrow requirement selection

Added note that pipenv sync does not remove packages missing from the lockfile (addressed by new --clean flag)

🔗 Full Changelog: v2026.8.0...v2026.9.0