Sourced from mypy's changelog.

Mypy Release Notes

Next Release

Packaging changes

• No longer provide mypyc-accelerated wheels for macOS x86_64 [mypyc-wheels #119](mypyc/mypy_mypyc-wheels#119)

Mypy 2.3

We've just uploaded mypy 2.3.0 to the Python Package Index (PyPI). Mypy is a static type checker for Python. This release includes new features, performance improvements and bug fixes. You can install it as follows:

python3 -m pip install -U mypy

You can read the full documentation for this release on Read the Docs.

The Upcoming Switch to the New Native Parser

We are planning to enable the new native parser (--native-parser) by default soon. We recommend that you test the native parser in your projects and report any issues in the mypy issue tracker.

Mypyc Free-threading Memory Safety

Free-threaded Python builds that don't have the GIL require additional synchronization primitives or lock-free algorithms to ensure memory safety when there are race conditions (for example, when a thread reads a list item while another thread writes the same list item concurrently). This release greatly improves memory safety of free threading.

List operations are now memory-safe on free threaded Python builds, even in the presence of race conditions. This has some performance cost. For list-heavy workloads, using librt.vecs.vec instead of list is often significantly faster, but note that vec is not (and likely won't be) fully memory safe, and the user is expected to avoid race conditions. The newly introduced librt.threading.Lock helps with this. Using variable-length tuples can also be more efficient than lists, since tuples are immutable and don't require expensive synchronization to ensure memory safety.

Instance attribute access is also (mostly) memory safe now on free-threaded builds in the presence of race conditions. We are planning to fix the remaining unsafe cases in a future release.

Full list of changes:

• Make attribute access memory safe on free-threaded builds (Jukka Lehtosalo, PR 21705)
• Fix unsafe borrowing of instance attributes with free-threading (Jukka Lehtosalo, PR 21688)
• Make list get/set item more memory safe on free-threaded builds (Jukka Lehtosalo, PR 21683)
• Don't borrow list items on free-threaded builds (Jukka Lehtosalo, PR 21679)
• Make multiple assignment from list memory-safe on free-threaded builds (Jukka Lehtosalo, PR 21684)

... (truncated)

• 8aabf84 Drop +dev from version
• 4d8ad2a Update changelog for 2.3 release (#21728)
• 2c21546 [mypyc] Update documentation of race conditions under free threading (#21726)
• a9f62a3 [mypyc] Make attribute access memory safe on free-threaded builds (#21705)
• 0faa413 Use PYODIDE environment variable for Emscripten cross-compilation detection...
• 3d75cdb [mypyc] Borrow final attributes more aggressively (#21702)
• 24c237d [mypyc] Improve documentation of Final (#21713)
• b5be217 [mypyc] Update free threading Python compatibility docs (#21711)
• cbcb51a Narrow for frozendict membership check (#21709)
• af2bc0f Sync typeshed (#21707)
• Additional commits viewable in compare view

Sourced from nox's releases.

2026.07.11 🏪

This release drops Python 3.9 and brings a batch of performance improvements, like caching uv detection and interpreter discovery, plus lazy module imports on Python 3.15. Various bugs were fixed as well.

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

• @​henryiii
• @​davidhewitt
• @​SAY-5 (first contribution)
• @​Himanshuagrawal4 (first contribution)
• @​TejasAmle (first contribution)
• @​felixfontein (first contribution)

Features:

• Drop Python 3.9 by @​henryiii in wntrblm/nox#1049
• Add return_code property to CommandFailed exception by @​felixfontein in wntrblm/nox#1129

Performance:

• Cache session-name normalization, uv detection, interpreter discovery, and metadata reads by @​henryiii in wntrblm/nox#1113
• Lazy modules on Python 3.15 by @​henryiii in wntrblm/nox#1115

Fixes:

• Script-mode pip resolution on Windows and --download-python fallback by @​henryiii in wntrblm/nox#1110
• Don't crash when a parametrized session has an empty parameter list by @​henryiii in wntrblm/nox#1109
• Hash fully non-ASCII session names instead of returning the envdir by @​henryiii in wntrblm/nox#1108
• Interpreter-resolution edge cases in virtualenv.py by @​henryiii in wntrblm/nox#1111
• Create missing parent directories for the session cache dir by @​henryiii in wntrblm/nox#1104
• Enforce --error-on-external-run even when log=False by @​henryiii in wntrblm/nox#1107
• Handle = in set_env values and out-of-tree change_dir in tox-to-nox by @​henryiii in wntrblm/nox#1105
• Return empty dict from load_toml when script file is missing by @​SAY-5 in wntrblm/nox#1096
• Show envvars in CLI help by @​henryiii in wntrblm/nox#1085

Documentation:

• Add PyO3 as a user by @​davidhewitt in wntrblm/nox#1123
• List micromamba in --default-venv-backend supported names by @​SAY-5 in wntrblm/nox#1092
• Clarify session.notify target docs by @​Himanshuagrawal4 in wntrblm/nox#1099
• Document venv backend for EOL Python by @​Himanshuagrawal4 in wntrblm/nox#1101
• Fix typo in README installation section by @​TejasAmle in wntrblm/nox#1097

Internal changes:

• Add Python 3.15 to the test matrix and classifiers by @​henryiii in wntrblm/nox#1133
• Isolate run_nox envdir to fix flaky test_main_requires by @​henryiii in wntrblm/nox#1134
• Assorted simplifications and dead-code removal by @​henryiii in wntrblm/nox#1112
• Remove Python 3.9-era pins/backports and tighten generator annotations by @​henryiii in wntrblm/nox#1106
• Run tests in parallel by @​henryiii in wntrblm/nox#965

... (truncated)

Sourced from nox's changelog.

Changelog

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 wntrblm/nox#1131
• Use python-discovery for interpreter discovery by @​henryiii in wntrblm/nox#1086
• Support requires-python in script mode by @​henryiii in wntrblm/nox#1142
• Sort classifier-derived Python versions by @​Himanshuagrawal4 in wntrblm/nox#1100

Fixes:

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

Documentation:

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

... (truncated)

• 3284968 chore: prepare release 2026.07.11 (#1132)
• d73f96a ci: add Python 3.15 to the test matrix and classifiers (#1133)
• 5391985 test: isolate run_nox envdir to fix flaky test_main_requires (#1134)
• 390d817 feat: add return_code to CommandFailed. (#1129)
• f1d5210 chore(deps): bump the github-actions group with 2 updates (#1125)
• 0894b73 chore(deps): bump the pre-commit group with 4 updates (#1126)
• 9b747ed ci: experimental MSYS2/MinGW test run (#1122)
• 8a44270 docs: add PyO3 as a user (#1123)
• 5bd0f83 perf: lazy modules on Python 3.15 (#1115)
• 982fcfa chore(deps): bump dependency-groups in the pre-commit group (#1121)
• Additional commits viewable in compare view

• deb4d49 Bump hypothesis version to 6.165.2 and update changelog
• a9eff28 Merge pull request #4842 from HypothesisWorks/claude/invert-everything
• c555e58 Cover the remaining _invert error paths in tests
• f9882a3 Apply review feedback: type ValueHole.value as object, polish docs and tests
• 8dca9e1 Restructure timezones() so its draws can be re-encoded
• 7e309df Invert dictionaries, unique lists with tuple_suffixes, and fixed_dictionaries
• 77ca292 Implement _invert for most remaining strategy combinators
• 5b20755 Bump hypothesis version to 6.165.1 and update changelog
• b4f2e92 Merge pull request #4806 from HypothesisWorks/claude/widening-shrinks
• 9431e20 Apply suggestions from code review
• Additional commits viewable in compare view