[jonathansick]

Summary

The weekly Periodic CI run has failed since 2026-10-26 (runs 40374010460, 41526175906, 42705867116) in the test (3.12, dev) cell, at the Run nox step:

error: No solution found when resolving dependencies
  cause: Because the current Python version (3.12.16) does not satisfy Python>=3.13
         and sphinx==9.3.0 depends on Python>=3.13, we can conclude that sphinx==9.3.0 cannot be used.

Root cause: Sphinx's main branch dropped Python 3.12 on 2026-10-20 (sphinx-doc/sphinx#14762; main is now 9.3.0 development with requires-python = ">=3.13"). The dev sessions install Sphinx from git, so that override can no longer be installed on Python 3.12. Because the matrix used the default fail-fast, that one cell also cancelled the other 11 cells every week.

Changes

• Skip the Sphinx dev sessions on Python 3.12 (noxfile.py), and exclude the 3.12 / dev cell from the Periodic CI matrix (.github/workflows/ci-cron.yaml). Sphinx 8 and 9 are still tested on Python 3.12. The floor is a single _SPHINX_DEV_MIN_PYTHON constant in the noxfile.
• Set fail-fast: false on the Periodic CI test matrix so one broken cell no longer hides the rest.
• Update dependencies with make update-deps (uv.lock, ruff and prettier prek hooks). That update surfaced three more problems, fixed here:
  • tomlkit 0.15.2 serializes an empty array of tables as affiliations = [] (0.15.1 and earlier omitted it). Documenteer added an empty affiliations array to every author table it touched, so technote sync-authors stopped being a byte-for-byte no-op on a healthy file (tests/services/technoteauthor_test.py::test_sync_authors_leaves_a_healthy_file_byte_identical). src/documenteer/storage/technotetoml.py now only creates the array when there is an affiliation to add. This is a user-facing fix, since tomlkit is unpinned for PyPI installs.
  • sphinx-autodoc-typehints 3.14 and later import sphinx.ext.autodoc._dynamic, which Sphinx 8 doesn't have. The nox sessions overrode Sphinx but kept the locked sphinx-autodoc-typehints (3.17.5, resolved for Sphinx 9), so 94 tests failed or errored in the Sphinx 8 sessions. The override now installs sphinx-autodoc-typehints in the same uv pip install as Sphinx, so the resolver picks a release that supports that Sphinx (3.5.2 for Sphinx 8; the locked release is kept for Sphinx 9 and dev).
  • ruff 0.17 newly reports ISC004 and ICN001 (datetime as dt) and formats imports with trailing pragma comments differently. The code is fixed to comply; no rules were ignored.
• Changelog fragment and a note in docs/dev/development.rst.

Validation

Run locally (macOS) against the updated lockfile with uv run --only-group=nox nox -s ...:

• test, typing, and demo for 3.12(sphinx='dev'): skipped with an explanatory message (previously failed at dependency resolution, reproduced locally).
• test, typing, and demo for Sphinx dev on Python 3.13, 3.14, and 3.15: pass.
• test, typing, and demo for 3.13(sphinx='8'), 3.13(sphinx='9'), and 3.12(sphinx='9'); test-3.12(sphinx='8'), typing-3.12(sphinx='8'), and test-3.15(sphinx='8'): pass.
• lint, docs, and packaging: pass.

The Periodic CI workflow itself only runs on a schedule or by manual dispatch, so the dev cells aren't exercised by this pull request's checks. It can be run against this branch with gh workflow run ci-cron.yaml --ref tickets/DM-56905.

[github-actions]

Documentation preview

Edition	URL
DM-56905	https://documenteer.lsst.io/v/DM-56905/

Build 1xxx-n490-4p9f-65 processed successfully.