[PSA] VPython: Unbundling deprecated Python 3.8 & bundling Python 3.14

[Alex Ovsienko]

Hello Chromium developers,

Python 3.8 reached upstream end-of-life in October 2024, and wheel building for Python 3.8 in dockerbuild was frozen in June 2026 (crrev.com/c/7930845).

We are planning to unbundle Python 3.8 from the default vpython3 CIPD package (moving it to on-demand CIPD download for remaining legacy callers) and bundle Python 3.14 alongside Python 3.11 (proposal).

What this means for you:

• Python 3.11 workflows (current default): No action required. Python 3.11 remains bundled directly inside vpython3 with no change to existing vpython.toml, PEP 723, or .vpython3 workflows.
• Python 3.8 workflows (deprecated): Fetched on demand from CIPD. Existing legacy .vpython3 specs targeting python_version: "3.8" will continue to work by automatically fetching the frozen Python 3.8 interpreter from CIPD on first run, rather than shipping Python 3.8 in every vpython3 download. We strongly encourage remaining Python 3.8 users to upgrade to Python 3.11+ and migrate legacy .vpython3 specs to vpython.toml or PEP 723 inline metadata.
• Python 3.14 support (bundled, uv-only): Once Python 3.8 is unbundled, Python 3.14 will be bundled in vpython3 alongside Python 3.11 for vpython.toml and PEP 723 (# /// script) workflows (requires-python = ">=3.14"). Legacy .vpython3 files will not support Python 3.14, and intermediate Python versions (3.12 and 3.13) are skipped.

Helpful commands & documentation:

• Proposal: vpython 3.8 Unbundling & Python 3.14 Bundle Proposal
• Migrate a remaining legacy .vpython3 spec: vpython3 -vpython-tool upgrade -legacy
• One-page quick guide: vpython_one_page.md
• Full VPython user manual: vpython.md

If this change affects your workflow or if you have any questions or concerns, please reply to this thread or comment in crbug.com/568132932.

• Alex Ovsienko