fix(teacher): 隔离子智能体流式消息与老师正文

tests/unit/coding-teacher-cloud.test.ts

@@ -257,10 +257,13 @@ it('reconnects from the last cursor and fills the final message after an earlier
   const transport: TeacherCloudTransport = {
     json: vi.fn(async (url) => {
       if (url === '/questions') return { request_id: 'question', run_id: 'one' };
-      return ++reads < 3 ? { status: 'running' } : { status: 'completed', output: '最终建议' };
+      return ++reads < 3
+        ? { status: 'running', thread_id: 'teacher-thread' }
+        : { status: 'completed', output: '最终建议' };
     }),
     events: vi.fn(async (url, _signal, accept) => {
       const message = (id: string, content: string) => ({
+        thread_id: 'teacher-thread',
         payload: { items: [{ stream_event: { type: 'message_delta', message_id: id, content } }] },
       });
       if (++streams === 1) {
@@ -285,3 +288,62 @@ it('reconnects from the last cursor and fills the final message after an earlier
   expect(text.join('')).toBe('我先检查。\n\n最终建议');
   expect(f.progress).toHaveBeenCalledWith('连接中断，正在恢复老师回复…');
 });
+
+it('keeps only the cloud main-thread answer while advancing past child events on reconnect', async () => {
+  const f = await fixture();
+  let reads = 0;
+  let streams = 0;
+  const text: string[] = [];
+  const streamUrls: string[] = [];
+  const transport: TeacherCloudTransport = {
+    json: vi.fn(async (url) => {
+      if (url === '/questions') return { request_id: 'question', run_id: 'one' };
+      return ++reads < 3
+        ? { status: 'running', thread_id: 'teacher-thread' }
+        : { status: 'completed', output: '老师最终答复' };
+    }),
+    events: vi.fn(async (url, _signal, accept) => {
+      streamUrls.push(url);
+      const message = (threadId: string, id: string, content: string) => ({
+        thread_id: threadId,
+        payload: { items: [{ stream_event: { type: 'message_delta', message_id: id, content } }] },
+      });
+      if (++streams === 1) {
+        accept('message', message('teacher-thread', 'answer', '老师'), '1-0');
+        accept('message', message('child-thread', 'child-answer', '子智能体内容'), '2-0');
+        throw new Error('connection interrupted');
+      }
+      accept(
+        'message',
+        {
+          thread_id: 'child-thread',
+          payload: {
+            chunk: {
+              stream_event: {
+                type: 'message_delta',
+                message_id: 'child-answer',
+                content: '子智能体后续内容',
+              },
+            },
+          },
+        },
+        '3-0'
+      );
+      accept('message', message('teacher-thread', 'answer', '最终答复'), '4-0');
+    }),
+  };
+  await prepareCloudTeacher(
+    f.account,
+    f.topic,
+    requestId,
+    f.access,
+    f.progress,
+    f.saveRequest,
+    transport
+  ).run([{ role: 'user', content: '检查' }], new AbortController().signal, (delta) =>
+    text.push(delta)
+  );
+  expect(text.join('')).toBe('老师最终答复');
+  expect(transport.events).toHaveBeenCalledTimes(2);
+  expect(streamUrls[1]).toContain('after_seq=2-0');
+});