A remote/cold client added NetworkStreamInGame the instant it got a
NetworkId, before the gameplay subscene's ghost prefabs finished
streaming. The server's first ghost snapshot then hit a client that
couldn't resolve those prefabs -> "ghost ... ENTITY_NOT_FOUND" ->
forced disconnect ("nothing loads"). On loopback / fast LAN the
go-in-game handshake beats the ~0.4s entity-subscene stream. The host
never hit it (it shares the server's loaded subscene); every remote
join did -- MPPM virtual players and real networked clients alike.
GoInGameClientSystem now gates full-client go-in-game on the gameplay
subscene being loaded (HasSingleton<PlayerSpawner>); thin clients skip
the gate. Verified cross-process in a standalone build over loopback:
join ghost-prefab errors 15->0, disconnects 1->0, client stays
connected and resolves all server ghosts.
Also adds a -mhost / -mjoin <ip> command-line hook to MainMenuController
for headless co-op testing (drives WorldLauncher.StartSession, no UI).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Luis Gonzalez
86575dd5bc