$CONTAINER/$EA_DIR only lived in the shell session where they were typed by hand — a new terminal or enough time between test steps left them empty, and an empty $CONTAINER silently collapsed "docker exec -it $CONTAINER asterisk -rx ..." into "docker exec -it asterisk -rx ...", failing with "No such container: asterisk" instead of an obviously-unset-variable error. Confirmed live. Replaced the manual pick with a docker ps auto-detect so a stale/forgotten variable can't silently break every command in the checklist. Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01H4k6J1qXXyYxhGEgnJaMvn