diff --git a/src/components/ChatBox/index.tsx b/src/components/ChatBox/index.tsx
index a95f183b..e35c18e9 100644
--- a/src/components/ChatBox/index.tsx
+++ b/src/components/ChatBox/index.tsx
@@ -139,6 +139,19 @@ export default function ChatBox(): JSX.Element {
     const _taskId = taskId || chatStore.activeTaskId;
     if (message.trim() === '' && !messageStr) return;
     const tempMessageContent = messageStr || message;
+
+    if (executionId && projectStore.activeProjectId) {
+      const project = projectStore.getProjectById(projectStore.activeProjectId);
+      const isInQueue = project?.queuedMessages?.some(
+        (m) => m.executionId === executionId
+      );
+      if (isInQueue) {
+        console.warn(
+          `[handleSend] Skipping message with executionId ${executionId} - already in queue, will be processed by useBackgroundTaskProcessor`
+        );
+        return;
+      }
+    }
     chatStore.setHasMessages(_taskId as string, true);
     if (!_taskId) return;
 
diff --git a/src/hooks/useBackgroundTaskProcessor.ts b/src/hooks/useBackgroundTaskProcessor.ts
index a9ab0e50..eed81a64 100644
--- a/src/hooks/useBackgroundTaskProcessor.ts
+++ b/src/hooks/useBackgroundTaskProcessor.ts
@@ -14,6 +14,10 @@
 
 import { generateUniqueId } from '@/lib';
 import { proxyUpdateTriggerExecution } from '@/service/triggerApi';
+import {
+  closeSSEConnectionsForTasks,
+  hasActiveSSEConnection,
+} from '@/store/chatStore';
 import { useProjectStore } from '@/store/projectStore';
 import { useTriggerTaskStore } from '@/store/triggerTaskStore';
 import { ExecutionStatus } from '@/types';
@@ -107,7 +111,44 @@ export function useBackgroundTaskProcessor() {
         continue;
       }
 
-      const msg = projectData.queuedMessages.find((m) => m.executionId);
+      // If SSE is active, starting a new task would duplicate trigger processing.
+      // Wait for the active task to finish; if task is done but SSE lingers, close it
+      // so the trigger can start fresh on the next poll.
+      const allTaskIds = Object.values(projectData.chatStores || {}).flatMap(
+        (cs) => Object.keys(cs.getState().tasks)
+      );
+      if (hasActiveSSEConnection(allTaskIds)) {
+        const activeChatStore = projectStore.getChatStore(project.id);
+        const activeState = activeChatStore?.getState();
+        const activeTaskId = activeState?.activeTaskId;
+        const activeTask = activeTaskId
+          ? activeState?.tasks[activeTaskId]
+          : null;
+
+        const isActiveTaskDone =
+          activeTask?.status === ChatTaskStatus.FINISHED ||
+          activeTask?.hasWaitComfirm;
+
+        if (isActiveTaskDone) {
+          console.log(
+            '[BackgroundTaskProcessor] Closing stale SSE for project',
+            project.id,
+            '- active task done, trigger waiting in queue'
+          );
+          closeSSEConnectionsForTasks(allTaskIds);
+        } else {
+          console.log(
+            '[BackgroundTaskProcessor] Skipping project',
+            project.id,
+            '- SSE active, task still in progress'
+          );
+        }
+        continue;
+      }
+
+      const msg = projectData.queuedMessages.find(
+        (m) => m.executionId && !m.processing
+      );
       if (msg && msg.executionId) {
         messageToProcess = {
           projectId: project.id,
@@ -137,7 +178,14 @@ export function useBackgroundTaskProcessor() {
       triggerName,
     } = messageToProcess;
 
-    projectStore.removeQueuedMessage(projectId, task_id);
+    projectStore.markQueuedMessageAsProcessing(projectId, task_id);
+
+    console.log(
+      '[BackgroundTaskProcessor] Marked message as processing:',
+      task_id,
+      'executionId:',
+      executionId
+    );
 
     try {
       // Get the latest project's chatStore
@@ -196,6 +244,8 @@ export function useBackgroundTaskProcessor() {
             '[BackgroundTaskProcessor] Background task completed:',
             executionId
           );
+          // Remove from queue after successful completion
+          projectStore.removeQueuedMessage(projectId, task_id);
           activeTasksRef.current.delete(executionId);
         })
         .catch((err: any) => {
@@ -203,6 +253,8 @@ export function useBackgroundTaskProcessor() {
             '[BackgroundTaskProcessor] Background task error:',
             err
           );
+          // Remove from queue on error as well
+          projectStore.removeQueuedMessage(projectId, task_id);
           // Report failure to backend
           proxyUpdateTriggerExecution(
             executionId,
@@ -239,6 +291,8 @@ export function useBackgroundTaskProcessor() {
         '[BackgroundTaskProcessor] Failed to start background task:',
         error
       );
+      // Remove from queue on error
+      projectStore.removeQueuedMessage(projectId, task_id);
       // Report failure to backend
       proxyUpdateTriggerExecution(
         executionId,
@@ -270,12 +324,13 @@ export function useBackgroundTaskProcessor() {
       for (const chatStore of Object.values(project.chatStores)) {
         const state = chatStore.getState();
         const t = state.tasks[task.chatTaskId];
-        if (
-          t &&
-          t.status !== ChatTaskStatus.RUNNING &&
-          t.status !== ChatTaskStatus.PAUSE
-        ) {
-          toRemove.push(executionId);
+        if (t) {
+          if (
+            t.status !== ChatTaskStatus.RUNNING &&
+            t.status !== ChatTaskStatus.PAUSE
+          ) {
+            toRemove.push(executionId);
+          }
           break;
         }
       }
diff --git a/src/hooks/useTriggerTaskExecutor.ts b/src/hooks/useTriggerTaskExecutor.ts
index dc52b450..1d493cfc 100644
--- a/src/hooks/useTriggerTaskExecutor.ts
+++ b/src/hooks/useTriggerTaskExecutor.ts
@@ -182,11 +182,6 @@ export function useTriggerTaskExecutor() {
         // Format the message with all context
         const formattedMessage = formatTriggeredTaskMessage(task);
 
-        console.log(
-          '[TriggerTaskExecutor] Adding message to project queue:',
-          formattedMessage.substring(0, 100) + '...'
-        );
-
         // Add message directly to projectStore's queuedMessages
         // useBackgroundTaskProcessor will pick it up and execute it
         const queuedTaskId = store.addQueuedMessage(
@@ -229,7 +224,7 @@ export function useTriggerTaskExecutor() {
     if (webSocketEvent) {
       console.log(
         '[TriggerTaskExecutor] WebSocket event received:',
-        webSocketEvent
+        webSocketEvent.executionId
       );
 
       const task: TriggeredTask = {
diff --git a/src/store/chatStore.ts b/src/store/chatStore.ts
index 5605dcc6..9138f857 100644
--- a/src/store/chatStore.ts
+++ b/src/store/chatStore.ts
@@ -3448,3 +3448,26 @@ export const useChatStore = chatStore;
 export const createChatStoreInstance = chatStore;
 
 export const getToolStore = () => chatStore().getState();
+
+/** Returns true if any task has an active SSE connection. */
+export function hasActiveSSEConnection(taskIds: string[]): boolean {
+  return taskIds.some((taskId) => !!activeSSEControllers[taskId]);
+}
+
+/** Close SSE for given tasks (e.g. after completion, so triggers can start fresh). */
+export function closeSSEConnectionsForTasks(taskIds: string[]): void {
+  for (const taskId of taskIds) {
+    if (activeSSEControllers[taskId]) {
+      console.log(
+        '[closeSSEConnectionsForTasks] Closing SSE for task:',
+        taskId
+      );
+      try {
+        activeSSEControllers[taskId].abort();
+      } catch (_e) {
+        // Ignore if already aborted
+      }
+      delete activeSSEControllers[taskId];
+    }
+  }
+}
diff --git a/src/store/projectStore.ts b/src/store/projectStore.ts
index 24369dba..a5b4ff24 100644
--- a/src/store/projectStore.ts
+++ b/src/store/projectStore.ts
@@ -31,6 +31,7 @@ interface TaskQueue {
   triggerTaskId?: string;
   triggerId?: number;
   triggerName?: string;
+  processing?: boolean;
 }
 
 interface Project {
@@ -112,6 +113,7 @@ interface ProjectStore {
   removeQueuedMessage: (projectId: string, taskId: string) => TaskQueue;
   restoreQueuedMessage: (projectId: string, messageData: TaskQueue) => void;
   clearQueuedMessages: (projectId: string) => void;
+  markQueuedMessageAsProcessing: (projectId: string, taskId: string) => void;
 
   // Chat store state management
   createChatStore: (projectId: string, chatName?: string) => string | null;
@@ -873,6 +875,10 @@ const projectStore = create<ProjectStore>()((set, get) => ({
       },
     }));
 
+    console.log(
+      `[addQueuedMessage] Message added successfully: task_id=${actual_task_id}, queue length now: ${get().projects[projectId].queuedMessages.length}`
+    );
+
     return actual_task_id;
   },
 
@@ -966,6 +972,43 @@ const projectStore = create<ProjectStore>()((set, get) => ({
     }));
   },
 
+  markQueuedMessageAsProcessing: (projectId: string, taskId: string) => {
+    const { projects } = get();
+
+    if (!projects[projectId]) {
+      console.warn(`Project ${projectId} not found`);
+      return;
+    }
+
+    const message = projects[projectId].queuedMessages.find(
+      (m) => m.task_id === taskId
+    );
+
+    if (!message) {
+      console.warn(
+        `Message with task_id ${taskId} not found in project ${projectId}`
+      );
+      return;
+    }
+
+    set((state) => ({
+      projects: {
+        ...state.projects,
+        [projectId]: {
+          ...state.projects[projectId],
+          queuedMessages: state.projects[projectId].queuedMessages.map((m) =>
+            m.task_id === taskId ? { ...m, processing: true } : m
+          ),
+          updatedAt: Date.now(),
+        },
+      },
+    }));
+
+    console.log(
+      `[ProjectStore] Marked message as processing: ${taskId} in project ${projectId}`
+    );
+  },
+
   getAllChatStores: (projectId: string) => {
     const { projects } = get();