diff --git a/clearing-parent/clearing-service/src/main/java/ru/spcex/clearing/service/EventsReceiver.java b/clearing-parent/clearing-service/src/main/java/ru/spcex/clearing/service/EventsReceiver.java
index 0471f96ee..5a4698be4 100644
--- a/clearing-parent/clearing-service/src/main/java/ru/spcex/clearing/service/EventsReceiver.java
+++ b/clearing-parent/clearing-service/src/main/java/ru/spcex/clearing/service/EventsReceiver.java
@@ -126,7 +126,11 @@ public class EventsReceiver extends QueueConsumerV2 implements InitializingBean
 
         callback(LauncherCommandRequest.class)
                 .setFunction(r -> {
-                    stateMachineWrapper.defineAndStartSession(r);
+                    try {
+                        stateMachineWrapper.defineAndStartSession(r);
+                    } catch (ValidationException e) {
+                        return makeErrorResponse(r, e);
+                    }
                     return null;
                 })
                 .forDestination(Task.startOfClearing.topic(), callbacks::put);
diff --git a/clearing-parent/clearing-service/src/main/java/ru/spcex/clearing/session/state/factory/SessionStateMachineWrapper.java b/clearing-parent/clearing-service/src/main/java/ru/spcex/clearing/session/state/factory/SessionStateMachineWrapper.java
index 8d1759e04..987812b5d 100644
--- a/clearing-parent/clearing-service/src/main/java/ru/spcex/clearing/session/state/factory/SessionStateMachineWrapper.java
+++ b/clearing-parent/clearing-service/src/main/java/ru/spcex/clearing/session/state/factory/SessionStateMachineWrapper.java
@@ -12,7 +12,9 @@ import org.springframework.statemachine.StateMachine;
 import org.springframework.statemachine.config.StateMachineFactory;
 import org.springframework.stereotype.Component;
 import ru.clearing.classes.statics.data.misc.Session;
+import ru.spcex.clearing.error.ClearingError;
 import ru.spcex.clearing.imdg.IMDGDistributedNames;
+import ru.spcex.clearing.notification.NotificationSender;
 import ru.spcex.clearing.platform.messaging.domain.BaseRequest;
 import ru.spcex.clearing.platform.messaging.domain.cud.schedule.LauncherCommandRequest;
 import ru.spcex.clearing.session.stage.TaskType;
@@ -20,13 +22,18 @@ import ru.spcex.clearing.session.state.DataEnum;
 import ru.spcex.clearing.session.state.SsnEvent;
 import ru.spcex.clearing.session.state.interceptor.SessionStatusChangingInterceptor;
 import ru.spcex.clearing.session.state.listener.MachineStopListener;
+import ru.spcex.platform.enumeration.ObjectType;
+import ru.spcex.platform.enumeration.Priority;
 import ru.spcex.platform.enumeration.Section;
 import ru.spcex.platform.enumeration.SessionType;
 import ru.spcex.platform.enumeration.WorkflowStatus;
 import ru.spcex.platform.imdg.api.Imdg;
 import ru.spcex.platform.imdg.api.ImdgProvider;
 import ru.spcex.platform.imdg.api.predicate.ImdgPredicateBuilder;
+import ru.spcex.platform.utils.enumeration.EnumMessage;
 import ru.spcex.platform.utils.enumeration.IEnumKey;
+import ru.spcex.platform.utils.enumeration.IMessageResolver;
+import ru.spcex.platform.utils.error.ValidationException;
 
 @Component
 public class SessionStateMachineWrapper {
@@ -36,12 +43,16 @@ public class SessionStateMachineWrapper {
     private final SessionStatusChangingInterceptor statusChangingInterceptor;
     private StateMachine<TaskType, SsnEvent> currentSession;
     private final Imdg<Session> ssnImdg;
+    private final NotificationSender notification;
+    private final IMessageResolver msgs;
 
     @Autowired
     public SessionStateMachineWrapper(
         ImdgProvider imdgProvider,
         Map<String, StateMachineFactory<TaskType, SsnEvent>> factories,
-        SessionStatusChangingInterceptor statusChangingInterceptor
+        SessionStatusChangingInterceptor statusChangingInterceptor,
+        NotificationSender notification,
+        IMessageResolver msgs
     ) {
         this.factories = factories
             .entrySet()
@@ -54,9 +65,11 @@ public class SessionStateMachineWrapper {
             .collect(Collectors.toMap(AbstractMap.SimpleEntry::getKey, AbstractMap.SimpleEntry::getValue));
         this.statusChangingInterceptor = statusChangingInterceptor;
         this.ssnImdg = imdgProvider.getImdg(IMDGDistributedNames.Map_Session, Session.class);
+        this.notification = notification;
+        this.msgs = msgs;
     }
 
-    public synchronized void defineAndStartSession(BaseRequest<LauncherCommandRequest> r) {
+    public synchronized void defineAndStartSession(BaseRequest<LauncherCommandRequest> r) throws ValidationException {
         LauncherCommandRequest payload = r.getRequestPayload();
         SessionType sessionType = IEnumKey.getEnumByKey(SessionType.class, payload.getSessionType());
         Section section = IEnumKey.getEnumByKey(Section.class, payload.getSection());
@@ -69,6 +82,7 @@ public class SessionStateMachineWrapper {
             log.info("no spring state machine factory for {}", sessionType);
             return;
         }
+        EnumMessage err = null;
         if (this.currentSession != null) {
             Session session = currentSession
                 .getExtendedState()
@@ -76,15 +90,20 @@ public class SessionStateMachineWrapper {
             Long id = session != null ? session.getId() : null;
             String ssnType = session != null ? session.getSessionType() : null;
             log.warn("Session already running: type={} id={}", ssnType, id);
-            return;
+            err = new EnumMessage(ClearingError.ActiveSessionIsPresent, String.valueOf(id));
         }
         Session activeSession = getActiveSession().orElse(null);
         if (activeSession != null) {
             log.warn("Session already running: type={} id={}",
                 activeSession.getSessionType(),
                 activeSession.getId());
-            return;
+            err = new EnumMessage(ClearingError.ActiveSessionIsPresent, String.valueOf(activeSession.getId()));
         }
+        if (err != null) {
+            notification.sendNotification(ObjectType.session, msgs.resolve(err), Priority.HIGH);
+            throw new ValidationException(err);
+        }
+
         this.currentSession = build(factory);
         this.currentSession.addStateListener(new MachineStopListener(
             this::clearCurrentMachine