python-version (internal)

Set a rhiza-managed Python project's standard interpreter version.

Not a slash command

This is an internal procedure (plugin/prompts/python-version.md), not something you invoke. The skeleton procedure reads and follows it at its step 6, which is itself reached from /rhiza:init.

Supported: 3.11, 3.12, 3.13, 3.14. Python 3.9 and 3.10 are not supported — the script rejects them.

requires-python is the upstream fact: .python-version is pinned from it, and ruff derives its target-version from it. Set that one field and the rest follows.

Known upstream issue: ruff's target-version

Ruff normally infers target-version from requires-python, but rhiza's synced ruff.toml hardcodes target-version = "py311", which overrides that inference. A repo retargeted to 3.13 therefore ends up with requires-python = ">=3.13" while ruff still lints as py311, so pyupgrade never suggests 3.12+ idioms.

The procedure detects and reports this mismatch but deliberately does not fix it: ruff.toml is template-owned, so a local edit is reverted by the next /rhiza:update sync. The fix is to drop the line upstream in jebel-quant/rhiza and let ruff infer.

What it does

Runs the bundled plugin/scripts/set_python_version.py — stdlib-only — which edits the pyproject.toml [project] table:

• pins requires-python = ">=X.Y" (corrected in place);
• rewrites the Programming Language :: Python :: X.Y trove classifiers to the supported range from the chosen version upward, dropping any stale or unsupported Python classifiers (including a bare Programming Language :: Python :: 3) while preserving non-Python classifiers.

It then re-pins .python-version with uv python pin --no-python-downloads — the tool that owns that file — rather than writing it by hand. The flag matters: without it uv downloads the interpreter (~25 MiB) if it isn't installed, which a metadata step has no business doing; with it, uv refuses a pin that contradicts the requires-python just written, giving a free consistency check.

Notes

• Works without the rhiza CLI installed.
• Idempotent — re-running with the same version changes nothing.
• uv python pin warns but still succeeds on a nonsense version, so it isn't the validation layer — the bundled script is, and it rejects anything outside 3.11–3.14.
• Out of scope: CI version matrices and other version references elsewhere in the repo. Check those separately when you drop or add a version.

Reference

Source	plugin/prompts/python-version.md
Invocation	not a slash command — reached with Read, never invoked
Read by	/rhiza:init, skeleton