Observed 2026-08-20 01:05 at sint-niklaas-tourism-office testing: two iPads launched mercator-talks ~7s apart and BOTH landed on cosmic-pretzel-98 while boom-pickle-38 sat idle. stream_count in /api/v1/bodies/eligible comes from body heartbeats, so within the lag window both heads saw cosmic as idle and picked it. Sunshine accepted the second concurrent session (see companion hydraheadipad issue about the shared uniqueid). Options: optimistic session reservation at discovery time (head claims the body via the session store before probing), or have eligible consult the live session store instead of heartbeat stream_count.
2026-09-05: confirmed in production at sint-niklaas-tourism-office with THREE iPads on one body (cosmic-pretzel-98), 204 UUID mismatch log lines. Full evidence, mechanism and direction in #660.