fix(title): avoid default LLM call before stream end (#3885)

* fix(title): avoid default LLM call before stream end

* fix(title): keep default fallback local

* fix(title): harden fallback and replay e2e

* docs(title): align fallback title behavior

backend/AGENTS.md

@@ -581,7 +581,7 @@ Returns `{}` when Langfuse is not in the enabled providers — LangSmith-only de
 - `tool_groups[]` - Logical groupings for tools
 - `sandbox.use` - Sandbox provider class path
 - `skills.path` / `skills.container_path` - Host and container paths to skills directory
-- `title` - Auto-title generation (enabled, max_words, max_chars, prompt_template)
+- `title` - Auto-title generation (enabled, max_words, max_chars, model_name; null model_name uses fast local fallback, explicit model_name uses the prompt_template LLM path)
 - `summarization` - Context summarization (enabled, trigger conditions, keep policy)
 - `subagents.enabled` - Master switch for subagent delegation
 - `memory` - Memory system (enabled, storage_path, debounce_seconds, model_name, max_facts, fact_confidence_threshold, injection_enabled, max_injection_tokens)

backend/docs/AUTO_TITLE_GENERATION.md

@@ -9,7 +9,7 @@
 使用 `TitleMiddleware` 在 `after_model` 钩子中：
 1. 检测是否是首次对话（1个用户消息 + 1个助手回复）
 2. 检查 state 是否已有 title
-3. 调用 LLM 生成简洁的标题（默认最多6个词）
+3. 默认从首条用户消息生成本地 fallback 标题，避免在流式回复结束前额外等待一次 LLM 调用；显式配置 `model_name` 时才调用 LLM 生成标题（默认最多6个词）
 4. 将 title 存储到 `ThreadState` 中（会被 checkpointer 持久化）
 
 TitleMiddleware 会先把 LangChain message content 里的结构化 block/list 内容归一化为纯文本，再拼到 title prompt 里，避免把 Python/JSON 的原始 repr 泄漏到标题生成模型。
@@ -67,7 +67,7 @@ title:
   enabled: true
   max_words: 6
   max_chars: 60
-  model_name: null  # 使用默认模型
+  model_name: null  # null = 快速本地 fallback；填模型名才启用 LLM 标题
 ```
 
 或在代码中配置：
@@ -149,17 +149,21 @@ sequenceDiagram
     participant Client
     participant LangGraph
     participant TitleMiddleware
-    participant LLM
+    participant TitleModel as Title model (optional)
     participant Checkpointer
 
     User->>Client: 发送首条消息
     Client->>LangGraph: POST /threads/{id}/runs
     LangGraph->>Agent: 处理消息
     Agent-->>LangGraph: 返回回复
-    LangGraph->>TitleMiddleware: after_agent()
+    LangGraph->>TitleMiddleware: after_model()/aafter_model()
     TitleMiddleware->>TitleMiddleware: 检查是否需要生成 title
-    TitleMiddleware->>LLM: 生成 title
-    LLM-->>TitleMiddleware: 返回 title
+    alt title.model_name 为空（默认）
+        TitleMiddleware->>TitleMiddleware: 从首条用户消息生成本地 fallback title
+    else 显式配置 title.model_name
+        TitleMiddleware->>TitleModel: 生成 LLM title
+        TitleModel-->>TitleMiddleware: 返回 title
+    end
     TitleMiddleware->>LangGraph: return {"title": "..."}
     LangGraph->>Checkpointer: 保存 state (含 title)
     LangGraph-->>Client: 返回响应
@@ -178,20 +182,15 @@ sequenceDiagram
 ## 注意事项
 
 1. **读取方式不同**：Title 在 `state.values.title` 而非 `thread.metadata.title`
-2. **性能考虑**：title 生成会增加约 0.5-1 秒延迟，可通过使用更快的模型优化
-3. **并发安全**：middleware 在 agent 执行后运行，不会阻塞主流程
-4. **Fallback 策略**：如果 LLM 调用失败，会使用用户消息的前几个词作为 title
+2. **性能考虑**：默认配置不调用标题模型；只有显式配置 `title.model_name` 时，才会在首轮回复后额外等待一次 LLM title 生成
+3. **并发安全**：middleware 在 agent 首次完整回复后更新 state，不需要客户端额外请求
+4. **Fallback 策略**：默认使用用户消息前几个字符作为 title；如果显式启用的 LLM 调用失败，也会回退到该策略
 
 ## 测试
 
-```python
-# 测试 title 生成
-import pytest
-from deerflow.agents.title_middleware import TitleMiddleware
-
-def test_title_generation():
-    # TODO: 添加单元测试
-    pass
+```bash
+cd backend
+uv run pytest tests/test_title_middleware_core_logic.py tests/test_title_generation.py
 ```
 
 ## 故障排查
@@ -199,8 +198,8 @@ def test_title_generation():
 ### Title 没有生成
 
 1. 检查配置是否启用：`get_title_config().enabled == True`
-2. 检查日志：查找 "Generated thread title" 或错误信息
-3. 确认是首次对话：只有 1 个用户消息和 1 个助手回复时才会触发
+2. 确认是首次对话：只有 1 个用户消息和 1 个助手回复时才会触发
+3. 如果显式配置了 `title.model_name`，检查标题模型是否可用；未配置时会走本地 fallback
 
 ### Title 生成但客户端看不到
 
@@ -231,16 +230,19 @@ def test_title_generation():
 ```python
 # TitleMiddleware 核心逻辑
 @override
-def after_agent(self, state: TitleMiddlewareState, runtime: Runtime) -> dict | None:
-    """Generate and set thread title after the first agent response."""
-    if self._should_generate_title(state, runtime):
-        title = self._generate_title(runtime)
-        print(f"Generated thread title: {title}")
-        
-        # ✅ 返回 state 更新，会被 checkpointer 自动持久化
-        return {"title": title}
-    
-    return None
+async def aafter_model(self, state: TitleMiddlewareState, runtime: Runtime) -> dict | None:
+    return await self._agenerate_title_result(state)
+
+async def _agenerate_title_result(self, state: TitleMiddlewareState) -> dict | None:
+    if not self._should_generate_title(state):
+        return None
+
+    config = self._get_title_config()
+    if not config.model_name:
+        return self._generate_title_result(state)
+
+    # 显式配置 title.model_name 时才调用标题模型；失败会回退到本地 title。
+    ...
 ```
 
 ## 相关文件

backend/docs/CONFIGURATION.md

@@ -387,7 +387,7 @@ title:
   enabled: true
   max_words: 6
   max_chars: 60
-  model_name: null  # Use first model in list
+  model_name: null  # null = fast local fallback; set a model name to use LLM title generation
 ```
 
 ### GitHub API Token (Optional for GitHub Deep Research Skill)

backend/docs/TITLE_GENERATION_IMPLEMENTATION.md

@@ -16,9 +16,9 @@
 #### [`packages/harness/deerflow/agents/middlewares/title_middleware.py`](../packages/harness/deerflow/agents/middlewares/title_middleware.py) (新建)
 - ✅ 创建 `TitleMiddleware` 类
 - ✅ 实现 `_should_generate_title()` 检查是否需要生成
-- ✅ 实现 `_generate_title()` 调用 LLM 生成标题
-- ✅ 实现 `after_agent()` 钩子，在首次对话后自动触发
-- ✅ 包含 fallback 策略（LLM 失败时使用用户消息前几个词）
+- ✅ 默认使用本地 fallback 生成标题，避免流式回复结束前等待额外 LLM 调用；显式配置 `model_name` 时可使用 LLM 标题
+- ✅ 实现 `after_model()` / `aafter_model()` 钩子，在首次对话后自动触发
+- ✅ 包含 fallback 策略（LLM 未配置或失败时使用用户消息前几个字符）
 
 #### [`packages/harness/deerflow/config/app_config.py`](../packages/harness/deerflow/config/app_config.py)
 - ✅ 导入 `load_title_config_from_dict`
@@ -37,7 +37,7 @@ title:
   enabled: true
   max_words: 6
   max_chars: 60
-  model_name: null
+  model_name: null  # null = 快速本地 fallback；填模型名才启用 LLM 标题
 ```
 
 ### 3. 文档
@@ -81,11 +81,13 @@ title:
   ↓
 Agent 处理并返回回复
   ↓
-TitleMiddleware.after_agent() 触发
+TitleMiddleware.after_model()/aafter_model() 触发
   ↓
 检查：是否首次对话？是否已有 title？
   ↓
-调用 LLM 生成 title
+默认从首条用户消息生成本地 fallback title
+  ↓
+如果显式配置 title.model_name，才调用 LLM 生成更精炼的 title
   ↓
 返回 {"title": "..."} 更新 state
   ↓
@@ -113,7 +115,7 @@ title:
   enabled: true
   max_words: 8      # 标题最多 8 个词
   max_chars: 80     # 标题最多 80 个字符
-  model_name: null  # 使用默认模型
+  model_name: null  # null = 快速本地 fallback；填模型名才启用 LLM 标题
 ```
 
 3. **配置持久化（可选）**
@@ -169,8 +171,8 @@ pytest
 ### Title 没有生成？
 
 1. 检查配置：`title.enabled = true`
-2. 查看日志：搜索 "Generated thread title"
-3. 确认是首次对话（1 个用户消息 + 1 个助手回复）
+2. 确认是首次对话（1 个用户消息 + 1 个助手回复）
+3. 如果显式配置了 `title.model_name`，检查标题模型是否可用；未配置时会走本地 fallback
 
 ### Title 生成但看不到？
 
@@ -188,22 +190,22 @@ pytest
 
 ## 📊 性能影响
 
-- **延迟增加**：约 0.5-1 秒（LLM 调用）
-- **并发安全**：在 `after_agent` 中运行，不阻塞主流程
+- **默认延迟**：默认 `title.model_name: null` 不会发起额外 LLM 调用，仅从首条用户消息生成本地 fallback title
+- **显式 LLM 标题延迟**：只有配置 `title.model_name` 时，首轮回复后才会等待一次标题模型调用
+- **并发安全**：在 `after_model()` / `aafter_model()` 中更新 state，不需要客户端额外请求
 - **资源消耗**：每个 thread 只生成一次
 
 ### 优化建议
 
-1. 使用更快的模型（如 `gpt-3.5-turbo`）
-2. 减少 `max_words` 和 `max_chars`
-3. 调整 prompt 使其更简洁
+1. 默认保持 `model_name: null`，避免流式回复结束前的额外 LLM 等待
+2. 如需更精炼标题，再显式配置较快的标题模型
+3. 减少 `max_words` 和 `max_chars`，并让 prompt 保持简洁
 
 ---
 
 ## 🚀 下一步
 
-- [ ] 添加集成测试（需要 mock LangGraph Runtime）
-- [ ] 支持自定义 prompt template
+- [ ] 补充 prompt template 的集成测试
 - [ ] 支持多语言 title 生成
 - [ ] 添加 title 重新生成功能
 - [ ] 监控 title 生成成功率和延迟

backend/packages/harness/deerflow/agents/middlewares/title_middleware.py

@@ -67,6 +67,11 @@ class TitleMiddleware(AgentMiddleware[TitleMiddlewareState]):
     def _is_user_message_for_title(message: object) -> bool:
         return getattr(message, "type", None) == "human" and not is_dynamic_context_reminder(message)
 
+    def _get_title_user_message(self, state: TitleMiddlewareState) -> str:
+        messages = state.get("messages", [])
+        user_msg_content = next((m.content for m in messages if self._is_user_message_for_title(m)), "")
+        return self._normalize_content(user_msg_content)
+
     def _should_generate_title(self, state: TitleMiddlewareState) -> bool:
         """Check if we should generate a title for this thread."""
         config = self._get_title_config()
@@ -97,10 +102,9 @@ class TitleMiddleware(AgentMiddleware[TitleMiddlewareState]):
         config = self._get_title_config()
         messages = state.get("messages", [])
 
-        user_msg_content = next((m.content for m in messages if self._is_user_message_for_title(m)), "")
         assistant_msg_content = next((m.content for m in messages if m.type == "ai"), "")
 
-        user_msg = self._normalize_content(user_msg_content)
+        user_msg = self._get_title_user_message(state)
         assistant_msg = self._strip_think_tags(self._normalize_content(assistant_msg_content))
 
         prompt = config.prompt_template.format(
@@ -153,18 +157,23 @@ class TitleMiddleware(AgentMiddleware[TitleMiddlewareState]):
         if not self._should_generate_title(state):
             return None
 
-        _, user_msg = self._build_title_prompt(state)
+        user_msg = self._get_title_user_message(state)
         return {"title": self._fallback_title(user_msg)}
 
     async def _agenerate_title_result(self, state: TitleMiddlewareState) -> dict | None:
-        """Generate a title asynchronously and fall back locally on failure."""
+        """Generate a configured LLM title asynchronously and fall back locally."""
         if not self._should_generate_title(state):
             return None
 
         config = self._get_title_config()
-        prompt, user_msg = self._build_title_prompt(state)
+        if not config.model_name:
+            user_msg = self._get_title_user_message(state)
+            return {"title": self._fallback_title(user_msg)}
+
+        user_msg = self._get_title_user_message(state)
 
         try:
+            prompt, user_msg = self._build_title_prompt(state)
             # attach_tracing=False because ``_get_runnable_config()`` inherits
             # the graph-level RunnableConfig (set in ``_make_lead_agent``) whose
             # callbacks already carry tracing handlers; binding them again at
@@ -172,10 +181,7 @@ class TitleMiddleware(AgentMiddleware[TitleMiddlewareState]):
             model_kwargs = {"thinking_enabled": False, "attach_tracing": False}
             if self._app_config is not None:
                 model_kwargs["app_config"] = self._app_config
-            if config.model_name:
-                model = create_chat_model(name=config.model_name, **model_kwargs)
-            else:
-                model = create_chat_model(**model_kwargs)
+            model = create_chat_model(name=config.model_name, **model_kwargs)
             response = await model.ainvoke(prompt, config=self._get_runnable_config())
             title = self._parse_title(response.content)
             if title:

backend/packages/harness/deerflow/config/title_config.py

@@ -24,11 +24,11 @@ class TitleConfig(BaseModel):
     )
     model_name: str | None = Field(
         default=None,
-        description="Model name to use for title generation (None = use default model)",
+        description="Model name to use for LLM title generation (None = use local fallback title)",
     )
     prompt_template: str = Field(
         default=("Generate a concise title (max {max_words} words) for this conversation.\nUser: {user_msg}\nAssistant: {assistant_msg}\n\nReturn ONLY the title, no quotes, no explanation."),
-        description="Prompt template for title generation",
+        description="Prompt template for LLM title generation when model_name is set",
     )
 
 

backend/tests/_replay_fixture.py

@@ -82,7 +82,8 @@ tools:
     use: deerflow.sandbox.tools:write_file_tool
 # Memory + summarization make background / debounced model calls whose timing is
 # non-deterministic; disable them so record and replay see the same model-call
-# set. (Title stays — it is an in-graph, deterministic call we record.)
+# set. Title stays enabled, but the default title.model_name: null path is a
+# local state update rather than a recorded model call.
 memory:
   enabled: false
   injection_enabled: false

backend/tests/test_title_middleware_core_logic.py

@@ -94,7 +94,7 @@ class TestTitleMiddlewareCoreLogic:
         assert middleware._should_generate_title(state) is False
 
     def test_generate_title_uses_async_model_and_respects_max_chars(self, monkeypatch):
-        _set_test_title_config(max_chars=12, model_name=None)
+        _set_test_title_config(max_chars=12, model_name="title-model")
         middleware = TitleMiddleware()
         model = MagicMock()
         model.ainvoke = AsyncMock(return_value=AIMessage(content="短标题"))
@@ -110,7 +110,7 @@ class TestTitleMiddlewareCoreLogic:
         title = result["title"]
 
         assert title == "短标题"
-        title_middleware_module.create_chat_model.assert_called_once_with(thinking_enabled=False, attach_tracing=False)
+        title_middleware_module.create_chat_model.assert_called_once_with(name="title-model", thinking_enabled=False, attach_tracing=False)
         model.ainvoke.assert_awaited_once()
         assert model.ainvoke.await_args.kwargs["config"] == {
             "run_name": "title_agent",
@@ -160,7 +160,7 @@ class TestTitleMiddlewareCoreLogic:
         )
 
     def test_generate_title_normalizes_structured_message_content(self, monkeypatch):
-        _set_test_title_config(max_chars=20)
+        _set_test_title_config(max_chars=20, model_name="title-model")
         middleware = TitleMiddleware()
         model = MagicMock()
         model.ainvoke = AsyncMock(return_value=AIMessage(content="请帮我总结这段代码"))
@@ -179,7 +179,7 @@ class TestTitleMiddlewareCoreLogic:
         assert title == "请帮我总结这段代码"
 
     def test_generate_title_fallback_for_long_message(self, monkeypatch):
-        _set_test_title_config(max_chars=20)
+        _set_test_title_config(max_chars=20, model_name="title-model")
         middleware = TitleMiddleware()
         model = MagicMock()
         model.ainvoke = AsyncMock(side_effect=RuntimeError("model unavailable"))
@@ -199,6 +199,7 @@ class TestTitleMiddlewareCoreLogic:
         assert title.startswith("这是一个非常长的问题描述")
 
     def test_aafter_model_delegates_to_async_helper(self, monkeypatch):
+        _set_test_title_config(model_name="title-model")
         middleware = TitleMiddleware()
 
         monkeypatch.setattr(middleware, "_agenerate_title_result", AsyncMock(return_value={"title": "异步标题"}))
@@ -208,6 +209,78 @@ class TestTitleMiddlewareCoreLogic:
         monkeypatch.setattr(middleware, "_agenerate_title_result", AsyncMock(return_value=None))
         assert asyncio.run(middleware.aafter_model({"messages": []}, runtime=MagicMock())) is None
 
+    def test_aafter_model_uses_local_fallback_when_no_title_model_is_configured(self, monkeypatch):
+        """Default async path must not block stream completion on a second LLM call."""
+        _set_test_title_config(max_chars=20, model_name=None)
+        middleware = TitleMiddleware()
+        create_chat_model = MagicMock()
+        monkeypatch.setattr(title_middleware_module, "create_chat_model", create_chat_model)
+
+        state = {
+            "messages": [
+                HumanMessage(content="请帮我写测试"),
+                AIMessage(content="好的"),
+            ]
+        }
+        result = asyncio.run(middleware.aafter_model(state, runtime=MagicMock()))
+
+        assert result == {"title": "请帮我写测试"}
+        create_chat_model.assert_not_called()
+
+    def test_async_generate_title_result_uses_local_fallback_without_model_name(self, monkeypatch):
+        """The default async helper path avoids the hidden title-model LLM call."""
+        _set_test_title_config(max_chars=20, model_name=None)
+        middleware = TitleMiddleware()
+        create_chat_model = MagicMock()
+        monkeypatch.setattr(title_middleware_module, "create_chat_model", create_chat_model)
+
+        state = {
+            "messages": [
+                HumanMessage(content="流式回答结束后不要再等待标题模型"),
+                AIMessage(content="好的"),
+            ]
+        }
+        result = asyncio.run(middleware._agenerate_title_result(state))
+
+        assert result == {"title": "流式回答结束后不要再等待标题模型"}
+        create_chat_model.assert_not_called()
+
+    def test_async_local_fallback_does_not_format_unused_prompt_template(self, monkeypatch):
+        """Local fallback should not depend on the LLM prompt template."""
+        _set_test_title_config(max_chars=20, model_name=None, prompt_template="{missing_placeholder}")
+        middleware = TitleMiddleware()
+        create_chat_model = MagicMock()
+        monkeypatch.setattr(title_middleware_module, "create_chat_model", create_chat_model)
+
+        state = {
+            "messages": [
+                HumanMessage(content="默认标题路径不应读取模型 prompt"),
+                AIMessage(content="好的"),
+            ]
+        }
+        result = asyncio.run(middleware._agenerate_title_result(state))
+
+        assert result == {"title": "默认标题路径不应读取模型 prompt"}
+        create_chat_model.assert_not_called()
+
+    def test_async_title_model_falls_back_when_prompt_template_is_invalid(self, monkeypatch):
+        """Opt-in LLM title generation still degrades locally on template errors."""
+        _set_test_title_config(max_chars=20, model_name="title-model", prompt_template="{usr_msg}")
+        middleware = TitleMiddleware()
+        create_chat_model = MagicMock()
+        monkeypatch.setattr(title_middleware_module, "create_chat_model", create_chat_model)
+
+        state = {
+            "messages": [
+                HumanMessage(content="请帮我写测试"),
+                AIMessage(content="好的"),
+            ]
+        }
+        result = asyncio.run(middleware._agenerate_title_result(state))
+
+        assert result == {"title": "请帮我写测试"}
+        create_chat_model.assert_not_called()
+
     def test_after_model_sync_delegates_to_sync_helper(self, monkeypatch):
         middleware = TitleMiddleware()
 
@@ -296,7 +369,7 @@ class TestTitleMiddlewareCoreLogic:
 
     def test_generate_title_async_strips_think_tags_in_response(self, monkeypatch):
         """Async title generation strips <think> blocks from the model response."""
-        _set_test_title_config(max_chars=50)
+        _set_test_title_config(max_chars=50, model_name="title-model")
         middleware = TitleMiddleware()
         model = MagicMock()
         model.ainvoke = AsyncMock(return_value=AIMessage(content="<think>用户想研究贵阳。</think>贵阳发展研究"))

config.example.yaml

@@ -1114,7 +1114,7 @@ title:
   enabled: true
   max_words: 6
   max_chars: 60
-  model_name: null # Use default model (first model in models list)
+  model_name: null # null = fast local fallback; set a model name to use LLM title generation
 
 # ============================================================================
 # Summarization Configuration

frontend/playwright.real-backend.config.ts

@@ -1,15 +1,21 @@
 import { defineConfig, devices } from "@playwright/test";
 
+const frontendPort = process.env.E2E_FRONTEND_PORT ?? "3000";
+const gatewayPort = process.env.E2E_GATEWAY_PORT ?? "8011";
+const frontendUrl = `http://localhost:${frontendPort}`;
+const gatewayUrl = `http://localhost:${gatewayPort}`;
+const gatewayInternalUrl = `http://127.0.0.1:${gatewayPort}`;
+
 /**
  * Layer 2 of the record/replay e2e: the REAL Next.js frontend rendering data
  * from a REAL gateway whose LLM is the deterministic `ReplayChatModel` (no API
  * key). This is separate from `playwright.config.ts` (which mocks the backend)
  * so the mock-based suite is untouched.
  *
- * Two webServers are started: the replay gateway (:8011) and the frontend
- * (:3000, pointed at the gateway). Auth-disabled mode is enabled on both
- * servers so the no-cookie e2e contract is covered; specs that need session
- * cookies still register a throwaway test account at runtime.
+ * Two webServers are started: the replay gateway and the frontend pointed at
+ * it. Auth-disabled mode is enabled on both servers so the no-cookie e2e
+ * contract is covered; specs that need session cookies still register a
+ * throwaway test account at runtime.
  */
 export default defineConfig({
   testDir: "./tests/e2e-real-backend",
@@ -21,7 +27,7 @@ export default defineConfig({
   timeout: 90_000,
 
   use: {
-    baseURL: "http://localhost:3000",
+    baseURL: frontendUrl,
     trace: "on-first-retry",
   },
 
@@ -29,9 +35,9 @@ export default defineConfig({
 
   webServer: [
     {
-      command: "uv run python scripts/run_replay_gateway.py --port 8011",
+      command: `uv run python scripts/run_replay_gateway.py --port ${gatewayPort} --cors ${frontendUrl}`,
       cwd: "../backend",
-      url: "http://localhost:8011/health",
+      url: `${gatewayUrl}/health`,
       reuseExistingServer: !process.env.CI,
       timeout: 180_000,
       stdout: "pipe",
@@ -46,10 +52,11 @@ export default defineConfig({
     },
     {
       command: "pnpm build && pnpm start",
-      url: "http://localhost:3000",
+      url: frontendUrl,
       reuseExistingServer: !process.env.CI,
       timeout: 240_000,
       env: {
+        PORT: frontendPort,
         SKIP_ENV_VALIDATION: "1",
         DEER_FLOW_AUTH_DISABLED: "1",
         BETTER_AUTH_SECRET: "local-dev-secret",
@@ -57,7 +64,7 @@ export default defineConfig({
         // next.config rewrites (same-origin proxy) instead of talking to the
         // gateway cross-origin — cross-origin fetches drop the auth cookies.
         // Just point that proxy at the replay gateway.
-        DEER_FLOW_INTERNAL_GATEWAY_BASE_URL: "http://127.0.0.1:8011",
+        DEER_FLOW_INTERNAL_GATEWAY_BASE_URL: gatewayInternalUrl,
       },
     },
   ],

frontend/src/content/en/harness/middlewares.mdx

@@ -82,7 +82,7 @@ Limits the number of parallel subagent task calls the agent can make in a single
 
 ### TitleMiddleware
 
-Automatically generates a title for the thread after the first exchange. The title is derived from the user's first message and the agent's response.
+Automatically generates a title for the thread after the first exchange. By default, the title is a fast local fallback derived from the user's first message. Set `title.model_name` only when you want the optional LLM title path.
 
 **Configuration**: `title:` section in `config.yaml`.
 
@@ -91,7 +91,7 @@ title:
   enabled: true
   max_words: 6
   max_chars: 60
-  model_name: null # use default model
+  model_name: null # local fallback; set a model name to use LLM title generation
 ```
 
 ---

frontend/src/content/zh/harness/middlewares.mdx

@@ -82,7 +82,7 @@ memory:
 
 ### TitleMiddleware
 
-在第一次交互后自动为线程生成标题。标题从用户的第一条消息和 Agent 的响应中派生。
+在第一次交互后自动为线程生成标题。默认从用户的第一条消息生成快速本地 fallback 标题；只有设置 `title.model_name` 时，才启用可选的 LLM 标题路径。
 
 **配置**：`config.yaml` 中的 `title:` 部分。
 
@@ -91,7 +91,7 @@ title:
   enabled: true
   max_words: 6
   max_chars: 60
-  model_name: null # 使用默认模型
+  model_name: null # 本地 fallback；填模型名才启用 LLM 标题
 ```
 
 ---

frontend/tests/e2e-real-backend/auth-disabled-contract.spec.ts

@@ -2,7 +2,9 @@ import { expect, test } from "@playwright/test";
 
 import { AUTH_DISABLED_USER } from "../../src/core/auth/auth-disabled-user";
 
-const APP = "http://localhost:3000";
+const APP =
+  process.env.E2E_APP_URL ??
+  `http://localhost:${process.env.E2E_FRONTEND_PORT ?? "3000"}`;
 
 test.describe("auth-disabled contract (real backend)", () => {
   test("gateway /auth/me returns the frontend synthetic user without a cookie", async ({

frontend/tests/e2e-real-backend/multi-run-order.spec.ts

@@ -20,7 +20,9 @@ import { expect, test } from "@playwright/test";
  * No model, no recording, no API key — the runs are seeded via a test-only
  * endpoint mounted only on the replay gateway.
  */
-const APP = "http://localhost:3000";
+const APP =
+  process.env.E2E_APP_URL ??
+  `http://localhost:${process.env.E2E_FRONTEND_PORT ?? "3000"}`;
 
 // Distinctive markers so getByText can't collide with UI chrome.
 const ALPHA = "ALPHA-FIRST-QUESTION-7f3a2c";

frontend/tests/e2e-real-backend/real-backend-render.spec.ts

@@ -11,13 +11,15 @@ const here = dirname(fileURLToPath(import.meta.url));
  * API key) and assert the browser renders the backend's data correctly.
  *
  * The prompt is read from the same fixture the gateway replays, so the input
- * hash matches and the recorded turns (write_file -> auto-title -> read_file ->
- * final answer) reproduce deterministically.
+ * hash matches and the recorded model turns reproduce deterministically. The
+ * default auto-title is local fallback state, not a replayed model turn.
  */
 // Register through the frontend origin (same-origin proxy) so the auth cookies
-// are stored for and sent to localhost:3000 — the gateway is reached via the
+// are stored for and sent to the browser origin — the gateway is reached via the
 // next.config rewrite, never cross-origin from the browser.
-const APP = "http://localhost:3000";
+const APP =
+  process.env.E2E_APP_URL ??
+  `http://localhost:${process.env.E2E_FRONTEND_PORT ?? "3000"}`;
 const fixture = JSON.parse(
   readFileSync(
     join(
@@ -32,10 +34,17 @@ const fixture = JSON.parse(
 };
 
 const PROMPT = fixture.prompt;
-// Derive the assertions from the fixture so a re-record auto-updates them. Both
-// are model-generated strings absent from the user prompt, so a pass proves the
-// replay drove the render (not a prompt echo): the first plain-text turn is the
-// in-graph auto-title; the JSON-array turn is the follow-up suggestions.
+const FALLBACK_TITLE_MAX_CHARS = 50;
+
+function fallbackTitle(userMsg: string): string {
+  if (!userMsg) return "New Conversation";
+  if (userMsg.length <= FALLBACK_TITLE_MAX_CHARS) return userMsg;
+  return `${userMsg.slice(0, FALLBACK_TITLE_MAX_CHARS).trimEnd()}...`;
+}
+
+// Suggestions still come from the recorded model fixture. The default title no
+// longer does: TitleMiddleware uses a local fallback when title.model_name is
+// unset, so derive that expected title from the prompt.
 const textTurns = fixture.turns
   .map((t) => t.output?.data?.content)
   .filter((c): c is string => typeof c === "string" && c.trim().length > 0);
@@ -52,7 +61,7 @@ const EXPECTED_SUGGESTION = ((): string => {
     return "";
   }
 })();
-const EXPECTED_TITLE = textTurns.find((c) => !c.trim().startsWith("[")) ?? "";
+const EXPECTED_TITLE = fallbackTitle(PROMPT);
 
 test.describe("real backend render (replay, no API key)", () => {
   test.beforeEach(async ({ context }) => {
@@ -66,7 +75,7 @@ test.describe("real backend render (replay, no API key)", () => {
     expect(resp.status(), await resp.text()).toBe(201);
   });
 
-  test("renders the replayed auto-title + suggestions from a real backend", async ({
+  test("renders the local auto-title + replayed suggestions from a real backend", async ({
     page,
   }) => {
     // ultra mode so the context the frontend sends (is_plan_mode + subagent_enabled)
@@ -85,17 +94,13 @@ test.describe("real backend render (replay, no API key)", () => {
     await textarea.fill(PROMPT);
     await textarea.press("Enter");
 
-    // Replay-only DOM assertions (derived from the fixture): both are
-    // model-generated strings absent from the user prompt, so they render only if
-    // the recorded turns replayed AND the real frontend rendered them — the
-    // in-graph auto-title and the post-answer follow-up suggestion. Together they
-    // prove the whole pipeline (replay backend -> real frontend render). The
-    // record spec waits for the /suggestions response, so a re-recorded fixture
-    // always captures the suggestion turn — a missing one is a broken recording
-    // and must fail loud here, not pass silently.
+    // The title is the default local fallback, while the suggestion is a
+    // replayed model output absent from the prompt. Together they prove the
+    // backend state update and the replayed post-answer model call both render
+    // through the real frontend.
     expect(
       EXPECTED_TITLE,
-      "fixture should contain an auto-title turn",
+      "default local fallback title should be derived from the prompt",
     ).not.toBe("");
     expect(
       EXPECTED_SUGGESTION,

frontend/tests/e2e-record/record-write-read-file.spec.ts

@@ -6,9 +6,9 @@ import { expect, test } from "@playwright/test";
  * RECORD driver (Plan A): drive the real frontend through the write/read-file
  * scenario against the real-model gateway. The gateway captures every model
  * call to DEERFLOW_RECORD_OUT; this just needs to drive the flow and wait until
- * the captures stop arriving (main turns + in-graph title + follow-up
- * suggestions all fired). It asserts nothing about content — it produces the
- * fixture, it doesn't verify it.
+ * the captures stop arriving (main turns + follow-up suggestions all fired;
+ * the default auto-title is local state). It asserts nothing about content —
+ * it produces the fixture, it doesn't verify it.
  */
 const APP = "http://localhost:3000";
 const SCENARIO = "write_read_file";