A full `pip install -r requirements.txt` on upgrade is fragile: the repo's
requirements list can contain entries that don't cleanly reinstall in the image
env (e.g. kokoro-tts has no py3.13 wheel — the image provisions it another way),
so reprocessing the whole file fails on a pre-existing line and aborts the
upgrade. Instead, diff the normalized requirement specs (old tree vs fetched) and
pip-install only the new/changed lines; satisfied/unclean existing lines are left
untouched. Empty delta => no pip run. --force no longer implies a full reinstall
(it forces the code refresh; deps still follow the delta).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EPLnsRpNBzWCHLgkXATqRz