pyshark's pcap reader calls asyncio.get_event_loop_policy().get_event_loop(),
which raises RuntimeError on Python 3.14 (deprecated in 3.12, removed in
3.14). Symptom: the matrix run completes the actual interop test
successfully but the runner's pcap-validation step crashes before it can
emit the result, dropping a 100+ line traceback.
run-matrix.sh now scans for python3.13 → 3.12 → 3.11 → python3, picking
the first that's both installed and < 3.14, and creates the venv with it.
Existing venvs created with 3.14 keep working (only matters for fresh
clones); for an existing broken venv, rm -rf .venv and re-run.
https://claude.ai/code/session_01HcvfQq1ttPV9PkRoJb4nyT
Claude
2667e966d8