A pod launched with no BT_SELF asks the relay for a seat before joining:
new control frames SEAT_REQUEST (-6) -> relay reserves the lowest roster
seat not claimed or reserved (60s reservation so simultaneous joiners
can't race onto one seat) -> SEAT_ASSIGN (-7, int32 hostID + NUL tag)
becomes relaySelf; everything downstream (egg self-match, HELLO) runs
exactly as if BT_SELF had been set. Roster full -> SEAT_FULL (-8) ->
clean Fail(). A real HELLO pops the reservation; a pod drop frees the
seat. Explicit BT_SELF still claims a specific seat (the operator's
local launches use it).
Client: L4NetworkManager::RelayRequestSeat (throwaway TCP dial to the
relay game port, 10s reply window). Relay: SEAT_REQUEST branch in
_handle_game_frame. Operator exporter collapsed from per-seat
join_as_playerN.bat to ONE universal join.bat (+ join_lan.bat with
BT_RELAY=auto) -- every player gets the same file, first come first
served, the arcade walk-up-to-a-pod model. players/ regenerated.
Verified: 8/8 seat stub tests (distinct seats in roster order, FULL on
exhaustion, claimed+reserved stays FULL, HELLO claim accepted, duplicate
HELLO refused); 2-node localhost e2e with NO BT_SELF on either pod ->
both seated, full ladder, RunMission pair, UDP flowing post-launch;
regression smoke: explicit-BT_SELF relay session clean with zero seat
requests, classic mesh (no BT_RELAY) un-regressed.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
