fix(games): reject duplicate queue entries

cmd/agentbbs/games.go

@@ -70,6 +70,9 @@ func (a *app) handleGame(s ssh.Session) {
 	case errors.Is(err, games.ErrNoOpponent):
 		_ = conn.Send(errEnvelope("no opponent found — try again later"))
 		_ = s.Exit(1)
+	case errors.Is(err, games.ErrAlreadyQueued):
+		_ = conn.Send(errEnvelope("this account is already queued for that game"))
+		_ = s.Exit(1)
 	case err != nil && !errors.Is(err, games.ErrUnknownGame):
 		// Unknown-game is already handled above; anything else is a wait abort
 		// (e.g. the agent disconnected) and needs no message.

cmd/agentbbs/gamesws.go

@@ -77,9 +77,13 @@ func (a *app) handleGameWS(w http.ResponseWriter, r *http.Request) {
 	defer func() { _ = a.st.EndSession(sessID) }()
 
 	_ = p.Send(map[string]any{"type": "queued", "game": gameID})
-	if err := a.mm.Play(context.Background(), gameID, p); errors.Is(err, games.ErrNoOpponent) {
+	err = a.mm.Play(context.Background(), gameID, p)
+	if errors.Is(err, games.ErrNoOpponent) {
 		_ = p.Send(errEnvelope("no opponent found — try again later"))
 	}
+	if errors.Is(err, games.ErrAlreadyQueued) {
+		_ = p.Send(errEnvelope("this account is already queued for that game"))
+	}
 }
 
 // wsPlayer adapts a gorilla WebSocket connection to games.PlayerIO. The match

internal/games/matchmaker.go

@@ -13,6 +13,9 @@ var ErrNoOpponent = errors.New("no opponent found")
 // ErrUnknownGame means the requested game id is not in the registry.
 var ErrUnknownGame = errors.New("unknown game")
 
+// ErrAlreadyQueued means the same player already has a connection waiting for this game.
+var ErrAlreadyQueued = errors.New("player already queued")
+
 // Store persists finished matches and tracks per-game ELO ratings. The SQLite
 // store implements it; the matchmaker stays storage-agnostic.
 type Store interface {
@@ -77,7 +80,11 @@ func (mm *Matchmaker) Play(ctx context.Context, gameID string, io PlayerIO) erro
 	}
 
 	mm.mu.Lock()
-	if w, waiting := mm.queue[gameID]; waiting && w.io.Name() != io.Name() {
+	if w, waiting := mm.queue[gameID]; waiting {
+		if w.io.Name() == io.Name() {
+			mm.mu.Unlock()
+			return ErrAlreadyQueued
+		}
 		// An opponent is waiting — pair up and run the match.
 		delete(mm.queue, gameID)
 		mm.mu.Unlock()