build: support Python 3.15

[MikeMcC399]

Situation

The Python list of supported versions includes Python 3.15 with planned first release date 2026-10-01 moved to 2026-10-09 (see PEP 790).

Node.js defines which versions of Python are supported in the configure script which covers Python 3.10 - 3.14, and currently excludes Python 3.15 for use in building and testing, since it is not yet explicitly listed under acceptable_versions.

Change

Add Python 3.15 to:

• configure &
• android-configure

acceptable_versions is spread over multiple lines to ease future backporting. Adding / removing versions can then be done independently without replacing the whole line. This will however need to be backported once manually before it becomes a benefit. For background see #60874 (comment).

Replace Python 3.14 with Python 3.15 in GitHub Actions workflows.

See Python 3.15 - what's new

Note

Windows configurations for automated installation should be separately updated after this PR has landed.

This change does not materially affect the Python versions used in Jenkins, which are determined by each OS' setup. Running in Jenkins only checks that the addition of Python 3.15 didn't prevent any of the existing lower versions from running.

[nodejs-github-bot]

Review requested:

• @nodejs/actions
• @nodejs/security-wg

[MikeMcC399]

This PR is intended to test Python 3.15.0rc2 initially, which states:

Release date: Sept. 1, 2026

It's the final 3.15 release candidate!

This is a candidate preview of Python 3.15

This release, 3.15.0rc2, is the final planned release candidate, containing around 144 bugfixes, build improvements and documentation changes from 76 contributors since 3.15.0rc1. Entering the release candidate phase, only reviewed code changes which are clear bug fixes are allowed between this release candidate and the final release.

The next release of Python 3.15 will be 3.15.0 final, scheduled for 2026-10-01.

Until Python 3.15 is officially released, the PR should stay blocked PRs that are blocked by other issues or PRs.

[MikeMcC399]

GItHub Actions is downloading the expected 3.15 rc2 version:

  Download from "https://github.com/actions/python-versions/releases/download/3.15.0-rc.2-33583724836/python-3.15.0-rc.2-linux-24.04-x64.tar.gz"

[MikeMcC399]

Currently Node.js allows the following, so a manual backport will be needed for 24.x & 22.x to avoid overwriting and dropping the lower versions, which need to be preserved:

Node.js branch	Python versions
main	3.10 - 3.14
26.x	3.10 - 3.14
24.x	3.9 - 3.14
22.x	3.8 - 3.14

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.00%. Comparing base (c988b7d) to head (e6989d6).
⚠️ Report is 39 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65750      +/-   ##
==========================================
+ Coverage   89.98%   90.00%   +0.02%     
==========================================
  Files         757      757              
  Lines      257739   257739              
  Branches    48877    48881       +4     
==========================================
+ Hits       231916   231976      +60     
+ Misses      16913    16847      -66     
- Partials     8910     8916       +6     

see 39 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/76934/

[gurgunday]

lgtm

[MikeMcC399]

https://www.python.org/downloads/ does not yet offer Python 3.15 for download. There was no 3.15 release on the planned date 2026-10-01. No new planned date has been published so far.

I will continue to monitor the 3.15 release.

There was however an EOL transition of Python 3.10 on 2026-10-01 . I plan to submit a PR to drop support for Python 3.10 in time for the upcoming Node.js 27 release. As in the past, this should not be backported to existing supported release lines. I'm holding back on this right now because submitting it whilst the PR for 3.15 is still pending will cause conflicts, and dropping the support for 3.10 is not urgently needed.

[richardlau]

python/peps#5160 has just pushed the release back another week.

[MikeMcC399]

When Python 3.15.0rc3 has been set up for download by github.com/actions/python-versions I plan to rebase to re-test with 3.15.0rc3.

PEP 790 shows the new expected 3.15.0 final: Friday, 2026-10-09 next week. I would expect it would be available from github.com/actions/python-versions on the following next working day, which would be Monday, 2026-10-12, since GitHub has to manually approve and release.