feat(teacher): stream Yuxi reasoning and answer previews

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

@@ -759,6 +759,7 @@ it.each(['suggestions', 'reply-v1', 'discussion-v1'] as const)(
     let firstReads = 0, resumedReads = 0;
     const text = vi.fn();
     const activity = vi.fn();
+    const stream = vi.fn();
     const transport: TeacherCloudTransport = {
       json: vi.fn(async (url) => {
         if (url === '/questions') return { request_id: requestId, run_id: 'before-read' };
@@ -783,18 +784,31 @@ it.each(['suggestions', 'reply-v1', 'discussion-v1'] as const)(
           payload: { items: [{ stream_event: { type: 'message_delta', message_id: id, content } }] },
         });
         if (url.includes('/before-read/')) {
+          accept('message', { thread_id: 'teacher-thread', payload: { items: [{ stream_event: {
+            type: 'message_delta', message_id: 'preamble', reasoning_content: '需要先读取项目。',
+          } }] } }, '0-1');
           accept('message', message('teacher-thread', 'preamble', '我先检查重力。'), '1-0');
           accept('message', message('teacher-thread', 'draft', '{"reply":"读取前的草案"}'), '2-0');
         } else {
           accept('message', message('child-thread', 'child', '子线程内容'), '1-0');
+          accept('message', { thread_id: 'teacher-thread', payload: { items: [{ stream_event: {
+            type: 'message_delta', message_id: 'final', reasoning_content: '已经获得项目证据。',
+          } }] } }, '1-1');
           accept('message', message('teacher-thread', 'final', finalOutput.slice(0, 12)), '2-0');
+          expect(stream).toHaveBeenLastCalledWith({ response: finalOutput.slice(0, 12) });
+          expect(text).not.toHaveBeenCalled();
         }
       }),
     };
     await prepareCloudTeacher(
-      f.account, f.topic, requestId, f.access, f.progress, f.saveRequest, transport, activity
+      f.account, f.topic, requestId, f.access, f.progress, f.saveRequest, transport, activity, stream
     ).run([{ role: 'user', content: '一起讨论' }], new AbortController().signal, text);
     expect(text.mock.calls).toEqual([[finalOutput]]);
+    expect(stream.mock.calls).toContainEqual([{ response: '' }]);
+    expect(stream.mock.calls).toContainEqual([{ response: finalOutput.slice(0, 12) }]);
+    expect(stream.mock.calls.flatMap(([update]) => update.reasoning ?? []).join(''))
+      .toBe('需要先读取项目。\n\n已经获得项目证据。');
+    expect(JSON.stringify(stream.mock.calls)).not.toContain('子线程内容');
     expect(activity.mock.calls).toEqual([
       [{ id: requestId + ':file', name: 'read_project_file', status: 'running' }],
       [{ id: requestId + ':file', name: 'read_project_file', status: 'completed' }],
@@ -870,3 +884,38 @@ it('keeps only the cloud main-thread answer while advancing past child events on
   expect(transport.events).toHaveBeenCalledTimes(2);
   expect(streamUrls[1]).toContain('after_seq=2-0');
 });
+
+it('streams main-thread reasoning through reconnect and drains a completed run before finalizing', async () => {
+  const f = await fixture();
+  f.topic.requests.push({ id: requestId, text: '检查', references: [], createdAt: 'now',
+    sourceCursor: f.access.source.cursor, sourceCapturedAt: 'now', includedSourceMessageIds: [],
+    omittedMessages: 0, status: 'running', response: '', presentation: 'reply-v1' });
+  let reads = 0;
+  const stream = vi.fn(), text = vi.fn();
+  const transport: TeacherCloudTransport = {
+    json: vi.fn(async url => url === '/questions' ? { request_id: requestId, run_id: 'one' }
+      : ++reads === 1 ? { status: 'running', thread_id: 'teacher-thread' }
+        : { status: 'completed', thread_id: 'teacher-thread', output: '{"reply":"最后正文","quickReplies":[]}' }),
+    events: vi.fn(async (url, _signal, accept) => {
+      const event = (thread_id: string, message_id: string, fields: Record<string, string>) => ({
+        thread_id, payload: { chunk: { stream_event: { type: 'message_delta', message_id, ...fields } } },
+      });
+      if (url.endsWith('0-0')) {
+        accept('message', event('teacher-thread', 'answer', { reasoning_content: '先看代码。' }), '1-0');
+        expect(stream).toHaveBeenLastCalledWith({ reasoning: '先看代码。' });
+        accept('message', event('child-thread', 'child', { reasoning_content: 'child-private' }), '2-0');
+        throw new Error('stream interrupted');
+      }
+      expect(url).toContain('after_seq=2-0');
+      accept('message', event('teacher-thread', 'answer', { additional_reasoning_content: '再确认结果。' }), '3-0');
+      accept('message', event('teacher-thread', 'answer', { content: '{"reply":"最后' }), '4-0');
+      expect(stream).toHaveBeenLastCalledWith({ response: '{"reply":"最后' });
+      expect(text).not.toHaveBeenCalled();
+    }),
+  };
+  await prepareCloudTeacher(f.account, f.topic, requestId, f.access, f.progress, f.saveRequest,
+    transport, undefined, stream).run([], new AbortController().signal, text);
+  expect(stream.mock.calls.flatMap(([update]) => update.reasoning ?? []).join('')).toBe('先看代码。再确认结果。');
+  expect(text.mock.calls).toEqual([['{"reply":"最后正文","quickReplies":[]}']]);
+  expect(transport.events).toHaveBeenCalledTimes(2);
+});