diff --git a/internal/server/clients.go b/internal/server/clients.go
index aa830ad..058c45d 100644
--- a/internal/server/clients.go
+++ b/internal/server/clients.go
@@ -9,14 +9,14 @@ import (
 
 // ClientRegistry manages connected WebSocket clients thread-safely
 type ClientRegistry struct {
-	clients map[*websocket.Conn]bool
+	clients map[*websocket.Conn]*sync.Mutex
 	mu      sync.RWMutex
 }
 
 // NewClientRegistry creates a new client registry
 func NewClientRegistry() *ClientRegistry {
 	return &ClientRegistry{
-		clients: make(map[*websocket.Conn]bool),
+		clients: make(map[*websocket.Conn]*sync.Mutex),
 	}
 }
 
@@ -24,7 +24,7 @@ func NewClientRegistry() *ClientRegistry {
 func (r *ClientRegistry) Add(conn *websocket.Conn) {
 	r.mu.Lock()
 	defer r.mu.Unlock()
-	r.clients[conn] = true
+	r.clients[conn] = &sync.Mutex{}
 }
 
 // Remove unregisters a client connection
@@ -43,6 +43,14 @@ func (r *ClientRegistry) Count() int {
 
 // Contains checks if a client is registered
 func (r *ClientRegistry) Contains(conn *websocket.Conn) bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	_, ok := r.clients[conn]
+	return ok
+}
+
+// GetMutex returns the mutex for a given connection, if it exists
+func (r *ClientRegistry) GetMutex(conn *websocket.Conn) *sync.Mutex {
 	r.mu.RLock()
 	defer r.mu.RUnlock()
 	return r.clients[conn]
@@ -51,9 +59,14 @@ func (r *ClientRegistry) Contains(conn *websocket.Conn) bool {
 // ForEach executes a function for each connected client
 func (r *ClientRegistry) ForEach(fn func(*websocket.Conn)) {
 	r.mu.RLock()
-	defer r.mu.RUnlock()
-
+	// Copy keys to avoid holding lock during iteration
+	conns := make([]*websocket.Conn, 0, len(r.clients))
 	for conn := range r.clients {
+		conns = append(conns, conn)
+	}
+	r.mu.RUnlock()
+
+	for _, conn := range conns {
 		fn(conn)
 	}
 }
@@ -61,9 +74,13 @@ func (r *ClientRegistry) ForEach(fn func(*websocket.Conn)) {
 // Broadcast sends a message to all connected clients
 func (r *ClientRegistry) Broadcast(fn func(*websocket.Conn) error) {
 	r.mu.RLock()
-	defer r.mu.RUnlock()
-
+	conns := make([]*websocket.Conn, 0, len(r.clients))
 	for conn := range r.clients {
+		conns = append(conns, conn)
+	}
+	r.mu.RUnlock()
+
+	for _, conn := range conns {
 		_ = fn(conn)
 	}
 }
diff --git a/internal/server/server.go b/internal/server/server.go
index 84ab1c9..6c6191d 100644
--- a/internal/server/server.go
+++ b/internal/server/server.go
@@ -324,6 +324,15 @@ func (s *Server) NotifyClient(conn *websocket.Conn, response Response) error {
 		return nil
 	}
 
+	mu := s.clients.GetMutex(conn)
+	if mu == nil {
+		// Client disconnected or not registered
+		return nil
+	}
+
+	mu.Lock()
+	defer mu.Unlock()
+
 	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
 	defer cancel()
 
diff --git a/internal/worker/processor.go b/internal/worker/processor.go
index 44f13ad..09d5d81 100644
--- a/internal/worker/processor.go
+++ b/internal/worker/processor.go
@@ -118,10 +118,10 @@ func (w *Worker) processJob(job *server.PrintJob) {
 	err := w.executePrint(job)
 
 	duration := time.Since(startTime)
-	w.lastJobTime = time.Now()
 
 	// Update statistics
 	w.mu.Lock()
+	w.lastJobTime = time.Now()
 	if err != nil {
 		w.jobsFailed++
 	} else {
@@ -154,11 +154,13 @@ func (w *Worker) processJob(job *server.PrintJob) {
 		}
 	}
 
-	// Notify client
+	// Notify client (async to not block worker loop)
 	if job.ClientConn != nil && w.notifier != nil {
-		if err := w.notifier.NotifyClient(job.ClientConn, response); err != nil {
-			log.Printf("[WORKER] ⚠️ Failed to notify client for job %s: %v", job.ID, err)
-		}
+		go func() {
+			if err := w.notifier.NotifyClient(job.ClientConn, response); err != nil {
+				log.Printf("[WORKER] ⚠️ Failed to notify client for job %s: %v", job.ID, err)
+			}
+		}()
 	}
 }
 
diff --git a/internal/worker/processor_test.go b/internal/worker/processor_test.go
new file mode 100644
index 0000000..90894c4
--- /dev/null
+++ b/internal/worker/processor_test.go
@@ -0,0 +1,76 @@
+package worker
+
+import (
+	"encoding/json"
+	"testing"
+	"time"
+
+	"github.com/adcondev/ticket-daemon/internal/server"
+	"github.com/coder/websocket"
+)
+
+// mockSlowNotifier simulates a slow network connection
+type mockSlowNotifier struct {
+	delay time.Duration
+}
+
+func (m *mockSlowNotifier) NotifyClient(_ *websocket.Conn, _ server.Response) error {
+	time.Sleep(m.delay)
+	return nil
+}
+
+func TestWorkerBlockingNotification(t *testing.T) {
+	// Setup
+	jobCount := 5
+	notifier := &mockSlowNotifier{delay: 200 * time.Millisecond} // 200ms delay per notification
+
+	// Create job queue
+	jobQueue := make(chan *server.PrintJob, jobCount)
+
+	// Create worker
+	config := Config{DefaultPrinter: "test"}
+	w := NewWorker(jobQueue, notifier, config)
+
+	// Start worker
+	w.Start()
+	defer w.Stop()
+
+	// Create dummy connection (we need a non-nil pointer)
+	dummyConn := &websocket.Conn{}
+
+	// Prepare jobs
+	for j := 0; j < jobCount; j++ {
+		job := &server.PrintJob{
+			ID:         "test-job",
+			ClientConn: dummyConn,
+			Document:   json.RawMessage("{}"), // Invalid document to trigger failure but still notify
+			ReceivedAt: time.Now(),
+		}
+		jobQueue <- job
+	}
+
+	start := time.Now()
+
+	// Wait for processing
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		stats := w.Stats()
+		if stats.JobsProcessed+stats.JobsFailed >= int64(jobCount) {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Fatalf("Timeout waiting for jobs to process. Processed: %d, Failed: %d", stats.JobsProcessed, stats.JobsFailed)
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+
+	duration := time.Since(start)
+
+	// With blocking notification: 5 jobs * 200ms = 1000ms (1s)
+	// We expect it to take at least 1s.
+	if duration > 500*time.Millisecond {
+		t.Errorf("Expected duration < 500ms (async), got %v", duration)
+	} else {
+		t.Logf("Blocking verified: Duration %v for %d jobs", duration, jobCount)
+	}
+}