fix(multiplayer): reject websocket caps before upgrade

multiplayer-next.md

@@ -1461,7 +1461,9 @@ Observability redaction now adds content-aware protection on top of denylisted f
 The authenticated control-plane WebSocket now caps each player at two
 simultaneous connections, releasing capacity on disconnect; this complements
 the bounded per-player event queue and prevents connection fan-out from
-becoming an unbounded account-level resource cost.
+becoming an unbounded account-level resource cost. Over-limit attempts fail
+before upgrade with `429 websocket_connection_limited`, rather than becoming
+ambiguous post-upgrade disconnects.
 
 Proposal explicit-decline cooldowns are now durable: the declining player is
 requeued for recovery, but a subsequent queue create is rejected until the

server/api/events.go

@@ -161,6 +161,13 @@ func (s *Service) controlPlaneEvent(w http.ResponseWriter, r *http.Request) {
 	if !ok {
 		return
 	}
+	hub := s.getEventHub()
+	subscriber := hub.subscribe(playerID)
+	if subscriber == nil {
+		writeError(w, http.StatusTooManyRequests, "websocket_connection_limited")
+		return
+	}
+	defer hub.unsubscribe(subscriber)
 	hijacker, ok := w.(http.Hijacker)
 	if !ok {
 		writeError(w, http.StatusNotImplemented, "websocket_unavailable")
@@ -178,12 +185,6 @@ func (s *Service) controlPlaneEvent(w http.ResponseWriter, r *http.Request) {
 	if err := buffered.Flush(); err != nil {
 		return
 	}
-	subscriber := s.getEventHub().subscribe(playerID)
-	if subscriber == nil {
-		return
-	}
-	defer s.getEventHub().unsubscribe(subscriber)
-
 	var writeMu sync.Mutex
 	done := make(chan struct{})
 	go func() {

server/api/events_connection_test.go

@@ -1,6 +1,10 @@
 package api
 
-import "testing"
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
 
 func TestEventHubCapsConnectionsPerPlayerAndReleasesCapacity(t *testing.T) {
 	hub := newEventHub()
@@ -20,3 +24,23 @@ func TestEventHubCapsConnectionsPerPlayerAndReleasesCapacity(t *testing.T) {
 	}
 	hub.unsubscribe(second)
 }
+
+func TestEventConnectionCapReturnsHTTP429BeforeUpgrade(t *testing.T) {
+	service := &Service{SessionBackend: &sessionBackendSpy{}}
+	hub := service.getEventHub()
+	first := hub.subscribe("player-1")
+	second := hub.subscribe("player-1")
+	defer hub.unsubscribe(first)
+	defer hub.unsubscribe(second)
+	request := httptest.NewRequest(http.MethodGet, "/v1/events", nil)
+	request.Header.Set("Upgrade", "websocket")
+	request.Header.Set("Connection", "Upgrade")
+	request.Header.Set("Sec-WebSocket-Version", "13")
+	request.Header.Set("Sec-WebSocket-Key", "dGhlIHNhbXBsZSBub25jZQ==")
+	request.Header.Set("Authorization", "Bearer session-1:token-1")
+	recorder := httptest.NewRecorder()
+	service.controlPlaneEvent(recorder, request)
+	if recorder.Code != http.StatusTooManyRequests {
+		t.Fatalf("connection-cap status = %d, want 429", recorder.Code)
+	}
+}