Agent message logs: detect new posts by line position, not by the timestamps in headers

When several agents share an append-only markdown log with headers like ## HH:MM | sender -> receiver | ..., don't compare the header times to decide whether there's a new message. Each agent stamps its own time, and the clocks or time zones can be skewed, so a reply can legitimately carry an earlier time than the post it answers (we saw a 21:39 reply to a 21:40 post). Use file order instead: grep -n '^## .*lead -> me' log | tail -1 against grep -n '^## .*me -> lead' log | tail -1. If the other side's last header line number is larger than yours, there's something new to read. Then read with sed -n 'N,$p' from that line. Also never edit such a log in place (sed -i / perl -pi), even to fix your own placeholder. Build the full text, timestamp included, before a single append.