Develop on Python 3.14, support 3.11+, add non-blocking 3.15 lane

[tipatterson-dev]

Moves development to Python 3.14, extends the supported range downward to 3.11, and adds a non-blocking 3.15 preview lane.

Development version: 3.14

.python-version is now tracked (and removed from .gitignore, with a comment explaining why). This is the only change that makes "developed on 3.14" enforceable rather than aspirational.

Measured rationale: with no .python-version, uv selects the newest stable interpreter satisfying requires-python, regardless of PATH — verified by restricting PATH to a 3.11-only interpreter and watching uv still build the venv on 3.14. Since requires-python allows <4.0, every contributor's environment would silently move to 3.15 the day it ships (2026-10-01). 3.15 is meant to be a preview lane here, not the dev environment.

All pinned CI jobs moved 3.13 → 3.14: linting.yaml, docs_pages.yaml, and tests.yaml's core-install / docs / publish-test, plus publish.yml's two pinned steps. Those jobs run a bare uv sync with no --python, so they would have followed .python-version anyway — leaving them saying 3.13 would have been misleading dead weight.

Supported floor: 3.11, not 3.10

requires-python goes >=3.12 → >=3.11. The suite passes unmodified on 3.11 (479 tests).

3.10 was tested and rejected for a specific reason, recorded in a comment next to requires-python: datetime.fromisoformat only accepts arbitrary fractional-second precision from 3.11 onward. 3.10 rejects the 5-digit form OSH emits (…T17:12:58.51182Z), failing test_control_stream_resource. Reaching 3.10 is possible but needs a parsing shim in timemanagement.py — the comment says so, to save the next person the experiment.

Note 3.10 is separately blocked for contributors by myst-parser>=5.0.0 (docs-only dev dep, requires 3.11); runtime deps alone do resolve on 3.10.

3.15: preview lane, non-blocking

tests.yaml gains a matrix leg with continue-on-error: ${{ matrix.experimental }}, named pytest (Python 3.15 — experimental, non-blocking) so the check list is self-explanatory.

Expect it red for now, and the YAML comment says why: as of 3.15.0a8 it fails during dependency installation, not during our tests — shapely has no 3.15 wheels, so uv falls back to a source build needing numpy headers. That is an upstream packaging gap, not an OSHConnect incompatibility, and the leg should go green on its own once shapely ships 3.15 wheels. A failure for any other reason is worth investigating.

publish.yml's matrix deliberately does not get this leg — a release gate must not depend on a lane that is allowed to fail. It gets 3.11 only.

Verification

Ran locally on all four supported versions: 479 pass on each of 3.11, 3.12, 3.13, 3.14. flake8 src/ clean; strict Sphinx build (-W --keep-going) succeeds. Also confirmed uv 0.12.0 produces no uv.lock drift — relevant because astral-sh/setup-uv@v6 installs the latest uv, so runners will pick it up regardless.

Version

0.5.3a1 → 0.5.4a0. requires-python is a packaging-visible change, so this is a real patch bump rather than an alpha increment.

Note the restart is at a0, not a1 as on previous patch lines. All of a, a0, a1 are valid PEP 440, but a bare a normalizes to a0 — so pyproject.toml would disagree with the built wheel. a0 is the canonical first alpha. Ordering is unaffected: 0.5.3a1 < 0.5.4a0 < 0.5.4a1 < 0.5.4.