diff --git a/src/tools/task/runtime.rs b/src/tools/task/runtime.rs
index 70f118d..eeab6bc 100644
--- a/src/tools/task/runtime.rs
+++ b/src/tools/task/runtime.rs
@@ -110,7 +110,8 @@ struct SubAgentEmitter {
     chat_id: String,
     metadata: HashMap<String, String>,
     store: Arc<SessionStore>,
-    sub_session_id: String,
+    /// 子/孙智能体自身的 task_id，用于持久化时作为 scope_key
+    task_id: String,
     stream_message_id: std::sync::Mutex<Option<String>>,
 }
 
@@ -159,7 +160,7 @@ impl EmittedMessageHandler for SubAgentEmitter {
             }
         }
 
-        // 拦截 todo_write 结果：持久化到 SQLite（子代理用 session_id 作为 scope_key）
+        // 拦截 todo_write 结果：持久化到 SQLite（子代理用 task_id 作为 scope_key，与 list_todos 保持一致）
         if message.tool_name.as_deref() == Some("todo_write") {
             self.persist_todo_write_result(&message);
         }
@@ -212,7 +213,7 @@ impl SubAgentEmitter {
             return;
         };
 
-        let scope_key = &self.sub_session_id;
+        let scope_key = &self.task_id;
 
         let now = std::time::SystemTime::now()
             .duration_since(std::time::UNIX_EPOCH)
@@ -366,7 +367,7 @@ impl DefaultSubAgentRuntime {
                         chat_id: session.parent_chat_id.clone(),
                         metadata,
                         store: self.store.clone(),
-                        sub_session_id: session.session_id.clone(),
+                        task_id: session.id.clone(),
                         stream_message_id: std::sync::Mutex::new(None),
                     },
                     self.conversation_repository.clone(),
diff --git a/web/src/components/Chat/MessageBubble.tsx b/web/src/components/Chat/MessageBubble.tsx
index 9fe6555..2126747 100644
--- a/web/src/components/Chat/MessageBubble.tsx
+++ b/web/src/components/Chat/MessageBubble.tsx
@@ -480,12 +480,12 @@ export function MessageBubble({ message, onNavigateToSubAgent, showThinking = tr
                     </button>
                   </div>
                 )}
-                {isTaskTool && message.subagentTaskId && !taskResult && (
+                {isTaskTool && message.navigateToTaskId && !taskResult && (
                   <div className="px-3 pb-1">
                     <button
                       onClick={(e) => {
                         e.stopPropagation()
-                        onNavigateToSubAgent?.(message.subagentTaskId!, taskDescription || '子智能体任务', subagentType)
+                        onNavigateToSubAgent?.(message.navigateToTaskId!, taskDescription || '子智能体任务', subagentType)
                       }}
                       className="text-xs text-[var(--accent-cyan)] hover:text-[var(--accent-cyan)]/80 hover:underline transition-colors flex items-center gap-1"
                     >
@@ -494,7 +494,7 @@ export function MessageBubble({ message, onNavigateToSubAgent, showThinking = tr
                     </button>
                   </div>
                 )}
-                {isTaskTool && !taskResult && !message.subagentTaskId && (
+                {isTaskTool && !taskResult && !message.navigateToTaskId && (
                   <div className="px-3 pb-2 text-xs text-[var(--text-muted)]">
                     子智能体正在执行...
                   </div>
@@ -571,11 +571,11 @@ export function MessageBubble({ message, onNavigateToSubAgent, showThinking = tr
                         </pre>
                       </div>
                     )}
-                    {isTaskTool && message.subagentTaskId && (
+                    {isTaskTool && message.navigateToTaskId && (
                       <button
                         onClick={(e) => {
                           e.stopPropagation()
-                          onNavigateToSubAgent?.(message.subagentTaskId!, taskDescription || '子智能体任务', subagentType)
+                          onNavigateToSubAgent?.(message.navigateToTaskId!, taskDescription || '子智能体任务', subagentType)
                         }}
                         className="text-xs text-[var(--accent-cyan)] hover:text-[var(--accent-cyan)]/80 hover:underline transition-colors flex items-center gap-1"
                       >
diff --git a/web/src/hooks/useChat.ts b/web/src/hooks/useChat.ts
index 17e94e7..28f3496 100644
--- a/web/src/hooks/useChat.ts
+++ b/web/src/hooks/useChat.ts
@@ -206,15 +206,6 @@ export function useChat(): UseChatReturn {
     return undefined
   }
 
-  // Extract topic_id from a message if present
-  const getTopicId = (message: WsOutbound): string | undefined => {
-    if (message.type === 'tool_call' || message.type === 'tool_result'
-        || message.type === 'tool_pending' || message.type === 'assistant_response') {
-      return (message as ToolCall | ToolResult | ToolPending | AssistantResponse).topic_id
-    }
-    return undefined
-  }
-
   // Convert a server message to ChatMessage (extracted from handleServerMessage logic)
   const serverMessageToChatMessage = (message: WsOutbound): ChatMessage | null => {
     switch (message.type) {
@@ -395,12 +386,8 @@ export function useChat(): UseChatReturn {
         return
       }
 
-      // Backfill grandchild task_id on task tool_call in sub-agent view.
-      // When the sub-agent spawns a grandchild via the task tool, the
-      // protocol's subagent_task_id field carries the parent task_id for
-      // routing, not the new child task_id. We must update it to the
-      // child's task_id from the task_started event so that "查看实时进度"
-      // navigates to the correct (grandchild) session.
+      // When the sub-agent spawns a grandchild, set navigateToTaskId
+      // on the task tool_call so "查看实时进度" navigates correctly.
       if (message.type === 'task_started') {
         const msg = message as TaskStarted
         if (msg.parent_task_id === currentSubAgentView.taskId) {
@@ -410,8 +397,8 @@ export function useChat(): UseChatReturn {
             const updatedMessages = [...top.messages]
             for (let i = updatedMessages.length - 1; i >= 0; i--) {
               const m = updatedMessages[i]
-              if (m.type === 'tool_call' && m.toolName === 'task' && m.subagentTaskId === currentSubAgentView.taskId) {
-                updatedMessages[i] = { ...m, subagentTaskId: msg.task_id }
+              if (m.type === 'tool_call' && m.toolName === 'task' && !m.navigateToTaskId) {
+                updatedMessages[i] = { ...m, navigateToTaskId: msg.task_id }
                 break
               }
             }
@@ -443,23 +430,8 @@ export function useChat(): UseChatReturn {
     }
 
     // In main view, skip sub-agent messages (they belong to sub-agent view).
-    // But use the task_id to associate with the running task tool card.
     const msgSubagentTaskId = getSubagentTaskId(message)
     if (msgSubagentTaskId) {
-      // 只 backfill 当前话题的 task tool_call，避免跨话题串扰
-      const msgTopicId = getTopicId(message)
-      if (msgTopicId && msgTopicId !== selectedTopicRef.current) return
-
-      setMessages((prev) => {
-        for (let i = prev.length - 1; i >= 0; i--) {
-          if (prev[i].type === 'tool_call' && prev[i].toolName === 'task' && !prev[i].subagentTaskId) {
-            const updated = [...prev]
-            updated[i] = { ...updated[i], subagentTaskId: msgSubagentTaskId }
-            return updated
-          }
-        }
-        return prev
-      })
       return
     }
 
@@ -478,12 +450,12 @@ export function useChat(): UseChatReturn {
         // 孙智能体的 TaskStarted 不应 backfill 到主视图
         if (msg.parent_task_id) break
 
-        // 立即更新对应的 task tool_call，让用户可以点击查看实时进度
+        // 设置 navigateToTaskId，让用户可以点击查看实时进度
         setMessages((prev) => {
           for (let i = prev.length - 1; i >= 0; i--) {
-            if (prev[i].type === 'tool_call' && prev[i].toolName === 'task' && !prev[i].subagentTaskId) {
+            if (prev[i].type === 'tool_call' && prev[i].toolName === 'task' && !prev[i].navigateToTaskId) {
               const updated = [...prev]
-              updated[i] = { ...updated[i], subagentTaskId: msg.task_id }
+              updated[i] = { ...updated[i], navigateToTaskId: msg.task_id }
               return updated
             }
           }
diff --git a/web/src/types/protocol.ts b/web/src/types/protocol.ts
index 1701900..776cd3b 100644
--- a/web/src/types/protocol.ts
+++ b/web/src/types/protocol.ts
@@ -453,7 +453,10 @@ export interface ChatMessage {
   status?: 'calling' | 'result' | 'pending'
   resultContent?: string
   callContent?: string
+  /** 路由字段：标识消息属于哪个子智能体会话（与后端 subagent_task_id 一致） */
   subagentTaskId?: string
+  /** 导航字段：仅 task 工具卡片使用，由 task_started 事件设置，指向新创建的子/孙智能体 task_id */
+  navigateToTaskId?: string
   durationMs?: number
   reasoningContent?: string
 }