2026.08.10 🔀

This release can run sessions in parallel with --parallel/-j (experimental for now, report any bugs!). Requires session opt-in, or use --allow-parallel. Interpreter discovery now uses the python-discovery package, which should be better at finding Python and supports version specifier sets. Using this, script mode reads requires-python. Many bugs were fixed, mostly in Python version handling, conda version specifiers, and option precedence. Unrecognized global options are now an error.

We'd like to thank the following folks who contributed to this release:

• @henryiii
• @Himanshuagrawal4
• @chuenchen309 (first contribution)
• @ColumbusLabs (first contribution)
• @deepakganesh78 (first contribution)
• @espressolee (first contribution)
• @Sanjays2402 (first contribution)
• @uttam12331 (first contribution)
• @yangfan-yf-yf (first contribution)

Features:

• Run sessions in parallel with --parallel/-j by @henryiii in #1131
• Use python-discovery for interpreter discovery by @henryiii in #1086
• Support requires-python in script mode by @henryiii in #1142
• Sort classifier-derived Python versions by @Himanshuagrawal4 in #1100

Fixes:

• Isolate script mode from inherited PYTHONPATH by @yangfan-yf-yf in #1157
• Require virtualenv 21+ on Python 3.15 by @henryiii in #1158
• Correct conda version constraints on Windows by @deepakganesh78 in #1146
• Make explicit command-line options beat noxfile and alias values by @henryiii in #1145
• Translate PEP 440 range interpreters to conda version specs by @henryiii in #1150
• Download upper-bound-only Python ranges by @henryiii in #1148
• Do not write ~/.local/bin shims when provisioning with uv by @henryiii in #1149
• Don't crash python_versions() on a major-only max_version by @chuenchen309 in #1140
• Correct python_versions() minimum for major-only and multiple lower bounds by @Sanjays2402 in #1127
• Don't crash building the manifest when a python-matrix session has an empty parametrize by @chuenchen309 in #1141
• Keep an empty inner @parametrize from being dropped when stacked by @chuenchen309 in #1138

Documentation:

• Add a multi-version pytest coverage recipe by @ColumbusLabs in #1143
• Fix broken examples, stale versions, and typos by @henryiii in #1154

Internal changes:

• Statically-typed option model as the single source of truth by @henryiii in #1144
• Fix flake8-lazy merge by @henryiii in #1147
• Drop stale type ignores for argcomplete 3.7.2 by @henryiii in #1155
• Make test_download_python_failed_install pass without uv installed by @uttam12331 in #1137
• Make the remaining uv download tests pass without uv installed by @espressolee in #1153
• Update the auto-release recipe to bump-my-version by @ColumbusLabs in #1136
• Bump the github-actions group with 5 updates by @dependabot in #1151
• Bump the pre-commit group with 6 updates by @dependabot in #1152