refactor(todo): 统一子代理 scope_key 为全局唯一的 task_id

- 修改 list_todos 处理器，子代理使用 task_id 作为 scope_key，替代原先的 sub:{parent_session_id}:{task_id}
- 调整 todo_write 的 scope_key_from_context 函数，子/孙代理使用 task_id 隔离，避免与父代理污染
- 修正子任务消息的 task_id 传递逻辑，在 useChat hook 中为子代理视图的孙子任务回填正确的 task_id
- 清理 MessageBubble 组件中多余的 isSubAgent 变量声明

src/command/handlers/list_todos.rs

@@ -41,10 +41,10 @@ impl CommandHandler for ListTodosCommandHandler {
             _ => None,
         };
 
-        // 子代理：scope_key = sub:{parent_session_id}:{task_id}
+        // 子代理：scope_key = task_id（全局唯一，与 todo_write 保持一致）
         // 主代理：scope_key = topic_id.unwrap_or(session_id)
-        let scope_key = if let (Some(tid), Some(parent_sid)) = (task_id.as_deref(), ctx.session_id.as_deref()) {
-            format!("sub:{}:{}", parent_sid, tid)
+        let scope_key = if let Some(tid) = task_id.as_deref() {
+            tid.to_string()
         } else {
             ctx.topic_id
                 .as_deref()

src/tools/todo_write.rs

@@ -330,10 +330,14 @@ impl Tool for TodoWriteTool {
 
 /// 计算 scope_key：
 /// - 主代理 (nesting_depth == 0)：优先 topic_id，否则 session_id
-/// - 子/孙代理 (nesting_depth > 0)：使用 session_id 隔离，避免污染父代理 todo
+/// - 子/孙代理 (nesting_depth > 0)：使用 task_id 隔离（全局唯一，与 list_todos 保持一致）
 pub(crate) fn scope_key_from_context(context: &ToolContext) -> Option<String> {
     if context.nesting_depth > 0 {
-        context.session_id.clone().filter(|s| !s.is_empty())
+        // 使用 task_id 而不是 session_id 作为 scope_key。
+        // session_id 对于孙智能体包含父链（如 sub:sub:root:parent:task），
+        // 而 list_todos handler 用根 session + task_id 拼接，两者不匹配。
+        // task_id 是全局唯一的 UUID（task:xxx），直接使用可避免层级不一致。
+        context.task_id.clone().filter(|s| !s.is_empty())
     } else {
         let tid = context.topic_id.as_deref().filter(|t| !t.is_empty());
         let sid = context.session_id.as_deref().filter(|s| !s.is_empty());

web/src/components/Chat/MessageBubble.tsx

@@ -364,7 +364,6 @@ export function MessageBubble({ message, onNavigateToSubAgent, showThinking = tr
 
     const isTaskTool = message.toolName === 'task'
     const taskResult = isTaskTool && hasResult ? parseTaskResult(displayContent) : null
-    const isSubAgent = !!message.subagentTaskId
     const subagentType = (message.arguments as Record<string, unknown> | null)?.subagent_type as string || 'general'
     const taskDescription = (message.arguments as Record<string, unknown> | null)?.description as string || ''
     const taskPrompt = (message.arguments as Record<string, unknown> | null)?.prompt as string || ''

web/src/hooks/useChat.ts

@@ -395,6 +395,34 @@ 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.
+      if (message.type === 'task_started') {
+        const msg = message as TaskStarted
+        if (msg.parent_task_id === currentSubAgentView.taskId) {
+          setSubAgentStack((prev) => {
+            if (prev.length === 0) return prev
+            const top = prev[prev.length - 1]
+            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 }
+                break
+              }
+            }
+            const newStack = [...prev]
+            newStack[newStack.length - 1] = { ...top, messages: updatedMessages }
+            return newStack
+          })
+          return
+        }
+      }
+
       // Only accept messages explicitly tagged with matching subagent_task_id.
       // History messages are now tagged by the backend (send_task_messages),
       // and live sub-agent messages are tagged by SubAgentEmitter.