cups: fix sub/unsub race

port 1.5

core/internal/server/cups/manager.go

@@ -229,6 +229,9 @@ func (m *Manager) snapshotState() CUPSState {
 func (m *Manager) Subscribe(id string) chan CUPSState {
 	ch := make(chan CUPSState, 64)
 
+	m.subLifecycleMu.Lock()
+	defer m.subLifecycleMu.Unlock()
+
 	wasEmpty := true
 	m.subscribers.Range(func(key string, ch chan CUPSState) bool {
 		wasEmpty = false
@@ -237,19 +240,25 @@ func (m *Manager) Subscribe(id string) chan CUPSState {
 
 	m.subscribers.Store(id, ch)
 
-	if wasEmpty && m.subscription != nil {
+	if !wasEmpty || m.subscription == nil {
+		return ch
+	}
+
 	if err := m.subscription.Start(); err != nil {
 		log.Warnf("[CUPS] Failed to start subscription manager: %v", err)
-		} else {
+		return ch
+	}
+
 	m.eventWG.Add(1)
 	go m.eventHandler()
-		}
-	}
 
 	return ch
 }
 
 func (m *Manager) Unsubscribe(id string) {
+	m.subLifecycleMu.Lock()
+	defer m.subLifecycleMu.Unlock()
+
 	if val, ok := m.subscribers.LoadAndDelete(id); ok {
 		close(val)
 	}
@@ -260,18 +269,22 @@ func (m *Manager) Unsubscribe(id string) {
 		return false
 	})
 
-	if isEmpty && m.subscription != nil {
+	if !isEmpty || m.subscription == nil {
+		return
+	}
+
 	m.subscription.Stop()
 	m.eventWG.Wait()
-	}
 }
 
 func (m *Manager) Close() {
 	close(m.stopChan)
 
+	m.subLifecycleMu.Lock()
 	if m.subscription != nil {
 		m.subscription.Stop()
 	}
+	m.subLifecycleMu.Unlock()
 
 	m.eventWG.Wait()
 	m.notifierWg.Wait()

core/internal/server/cups/manager_test.go

@@ -1,6 +1,9 @@
 package cups
 
 import (
+	"errors"
+	"fmt"
+	"sync"
 	"testing"
 
 	mocks_cups "github.com/AvengeMedia/DankMaterialShell/core/internal/mocks/cups"
@@ -75,6 +78,67 @@ func TestManager_Subscribe(t *testing.T) {
 	assert.Equal(t, 0, count)
 }
 
+// mirrors the real managers: eventChan guarded by mu, conn/running deliberately
+// unsynchronized so overlapping Start/Stop trips the race detector
+type stubSubscription struct {
+	mu      sync.Mutex
+	events  chan SubscriptionEvent
+	conn    *int
+	running bool
+}
+
+func (s *stubSubscription) Start() error {
+	if s.running {
+		return errors.New("already running")
+	}
+	s.running = true
+
+	s.mu.Lock()
+	s.events = make(chan SubscriptionEvent)
+	s.mu.Unlock()
+
+	v := 0
+	s.conn = &v
+	*s.conn++
+
+	return nil
+}
+
+func (s *stubSubscription) Stop() {
+	if !s.running {
+		return
+	}
+	s.running = false
+	s.conn = nil
+
+	s.mu.Lock()
+	close(s.events)
+	s.mu.Unlock()
+}
+
+func (s *stubSubscription) Events() <-chan SubscriptionEvent {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return s.events
+}
+
+func TestManager_SubscribeUnsubscribeRace(t *testing.T) {
+	m := NewTestManager(mocks_cups.NewMockCUPSClientInterface(t), nil)
+	m.subscription = &stubSubscription{}
+
+	var wg sync.WaitGroup
+	for i := range 8 {
+		wg.Go(func() {
+			id := fmt.Sprintf("client-%d", i)
+			for range 50 {
+				m.Subscribe(id)
+				m.Unsubscribe(id)
+			}
+		})
+	}
+	wg.Wait()
+}
+
 func TestManager_Close(t *testing.T) {
 	mockClient := mocks_cups.NewMockCUPSClientInterface(t)
 

core/internal/server/cups/types.go

@@ -79,6 +79,7 @@ type Manager struct {
 	client            CUPSClientInterface
 	pkHelper          PkHelper
 	subscription      SubscriptionManagerInterface
+	subLifecycleMu    sync.Mutex
 	stateMutex        sync.RWMutex
 	subscribers       syncmap.Map[string, chan CUPSState]
 	stopChan          chan struct{}