fix: close slow event subscribers safely

multiplayer-todo.md

@@ -1227,7 +1227,7 @@ the local/CI/community transport, not a silent production fallback.
 | # | Task | Acceptance |
 |---|---|---|
 | 8.39 `[D:8.3,8.14,8.17]` | **IN PROGRESS.** `MatchmakingState` now projects queue → proposal → allocation/process-ready/assignment-ready/connect/live plus terminal failure states; autoload `ControlPlaneClient` provides authenticated queue create/recovery/heartbeat/cancel and proposal response requests with idempotency/revision headers; `matchmaking.tscn`/`matchmaking.gd` expose the state and authoritative actions from the main menu; authenticated proposal recovery now reconciles missed proposal events and expires them at read time; the Go API now provides targeted authenticated revisioned event publication and the Godot client consumes state/proposal events | `test_matchmaking_state.gd`, `test_control_plane_client.gd`, `test_matchmaking_ui.gd`, `TestProposalRecoveryIsParticipantScopedAndExpiresAtReadBoundary` and `TestAuthenticatedWebSocketDeliversOnlyTargetedRevisionedEvents` reject stale/gapped/conflicting updates, validate endpoint/token/payload normalization, preserve idempotent duplicates, and guarantee visible phase/terminal copy; wiring durable allocation events into the outbox, wait/latency explanations and Godot runtime verification remain |
-| 8.40 `[D:8.3,8.14]` | **IN PROGRESS.** Pure Go revisioned replica reducer rejects gaps for REST resync, makes duplicate/out-of-order events idempotent, and resumes from the authoritative snapshot revision; authenticated queue-ticket recovery now has an owner-checked REST read; Godot client projection persists non-secret ticket/proposal state, forces authoritative recovery after restart, and can replay a lost queue-create response with the original ticket/idempotency key; the Go API now exposes an authenticated `/v1/events` WebSocket with bounded per-player queues, strict upgrade validation and REST-resync-safe slow-client failure; Godot `ControlPlaneClient` can connect to the stream, consume validated events, automatically reconnect with bounded backoff, and trigger REST recovery on projection gaps and stream return | `server/domain/sync.go`, `server/api/events.go`, `server/api/service.go`, `service_test.go`, `matchmaking_state.gd` and `control_plane_client.gd` cover gap, snapshot, replay, same-revision conflict, owner-only ticket recovery, expired-ticket terminal handling, malformed restart snapshots, API-level duplicate-create replay/conflict, authenticated handshake/key rejection and targeted event delivery; durable outbox fan-out and live Godot verification remain |
+| 8.40 `[D:8.3,8.14]` | **IN PROGRESS.** Pure Go revisioned replica reducer rejects gaps for REST resync, makes duplicate/out-of-order events idempotent, and resumes from the authoritative snapshot revision; authenticated queue-ticket recovery now has an owner-checked REST read; Godot client projection persists non-secret ticket/proposal state, forces authoritative recovery after restart, and can replay a lost queue-create response with the original ticket/idempotency key; the Go API now exposes an authenticated `/v1/events` WebSocket with bounded per-player queues, strict upgrade validation and REST-resync-safe slow-client failure; Godot `ControlPlaneClient` can connect to the stream, consume validated events, automatically reconnect with bounded backoff, and trigger REST recovery on projection gaps and stream return | `server/domain/sync.go`, `server/api/events.go`, `server/api/service.go`, `service_test.go`, `matchmaking_state.gd` and `control_plane_client.gd` cover gap, snapshot, replay, same-revision conflict, owner-only ticket recovery, expired-ticket terminal handling, malformed restart snapshots, API-level duplicate-create replay/conflict, authenticated handshake/key rejection, targeted event delivery and exactly-once slow-subscriber closure; durable outbox fan-out and live Godot verification remain |
 | 8.41 `[D:7.8,8.9,8.31,8.40]` | **IN PROGRESS.** Authenticated `GET /v1/assignments/{matchId}` now exposes only a validated, player-scoped assignment view; Godot `AssignmentState`/`ControlPlaneClient.fetch_assignment()` bind the response to the authenticated player, recheck expiry, preserve explicit transport/slot/join authorisation and do not connect before assignment-ready | `server/api/service.go`, `service_test.go`, `assignment_state.gd` and `test_assignment_state.gd` cover participant/identity/expiry/shape/transport boundaries and assignment recovery; signed manifest-to-player persistence, SDR relay-ticket installation, `hello` join-authorisation wiring, fencing integration and live Godot verification remain |
 | 8.42 `[D:8.22,8.23,8.24,8.40]` | **IN PROGRESS.** `RankedProfileState` and `ControlPlaneClient.fetch_ranked_profile()` expose the backend-authoritative rating/RD/volatility/games/tier/provisional/season view; matchmaking UI displays provisional/tier status without client-side rating math | `test_control_plane_client.gd` validates profile shape, numeric safety and provisional display; ranked profile fetch/display, committed revision after reconnect, abandon status and season countdown remain dependent on live auth/backend events and Godot runtime verification |
 | 8.43 `[D:8.39,8.40,8.41]` | **IN PROGRESS.** Matchmaking client now distinguishes expired queue recovery, session expiry, missing records and retryable control-plane outages; a 401 clears the in-memory token, emits `session_expired` and disables retry until a new session is configured; terminal messages remain visible and active searches are not falsely failed on transient errors | `MatchmakingState` and `ControlPlaneClient` tests cover explicit expiry and the existing terminal/retry-safe state paths; decline, version mismatch, regional outage retry UI, failed reconnect, duplicate-action recovery and live Godot verification remain |

server/api/events.go

@@ -60,6 +60,10 @@ func (h *eventHub) subscribe(playerID string) *eventSubscriber {
 
 func (h *eventHub) unsubscribe(subscriber *eventSubscriber) {
 	h.mu.Lock()
+	if _, subscribed := h.subscribers[subscriber]; !subscribed {
+		h.mu.Unlock()
+		return
+	}
 	delete(h.subscribers, subscriber)
 	close(subscriber.queue)
 	h.mu.Unlock()

server/api/service_test.go

@@ -257,6 +257,27 @@ func readServerWebSocketFrame(reader *bufio.Reader) ([]byte, error) {
 	return payload, err
 }
 
+func TestEventHubClosesSlowSubscribersExactlyOnce(t *testing.T) {
+	hub := newEventHub()
+	subscriber := hub.subscribe("player-1")
+	event := ControlPlaneEvent{Event: "state_changed", Revision: 1, ResourceID: "ticket-1234567890123456", OccurredAt: time.Unix(1000, 0).UTC(), State: "QUEUED", PlayerID: "player-1"}
+	for i := 0; i < eventQueueCapacity; i++ {
+		if err := hub.publish(event); err != nil {
+			t.Fatal(err)
+		}
+	}
+	if err := hub.publish(event); err != nil {
+		t.Fatal(err)
+	}
+	for {
+		_, open := <-subscriber.queue
+		if !open {
+			break
+		}
+	}
+	hub.unsubscribe(subscriber)
+}
+
 func TestQueueAPIRejectsUnauthenticatedUnknownAndOversizedInput(t *testing.T) {
 	service := &Service{Sessions: domain.NewSessionStore(), Queue: domain.NewQueue(), Candidate: func(string, string) (domain.Candidate, error) { return domain.Candidate{}, nil }}
 	server := httptest.NewServer(service.Handler())