Follow up PR #265: refine chapters, diagrams, and add S20 (#283)

* feat: s01-s14 docs quality overhaul — tool pipeline, single-agent, knowledge & resilience

Rewrite code.py and README (zh/en/ja) for s01-s14, each chapter building
incrementally on the previous. Key fixes across chapters:

- s01-s04: agent loop, tool dispatch, permission pipeline, hooks
- s05-s08: todo write, subagent, skill loading, context compact
- s09-s11: memory system, system prompt assembly, error recovery
- s12-s14: task graph, background tasks, cron scheduler

All chapters CC source-verified. Code inherits fixes forward (PROMPT_SECTIONS,
json.dumps cache, real-state context, can_start dep protection, etc.).

* feat: s15-s19 docs quality overhaul — multi-agent platform: teams, protocols, autonomy, worktree, MCP tools

Rewrite code.py and README (zh/en/ja) for s15-s19, the multi-agent platform
chapters. Each chapter inherits all previous fixes and adds one mechanism:

- s15: agent teams (TeamCreate, teammate threads, shared task list)
- s16: team protocols (plan approval, shutdown handshake, consume_inbox)
- s17: autonomous agents (idle polling, auto-claim, consume_lead_inbox)
- s18: worktree isolation (git worktree, bind_task, cwd switching, safety)
- s19: MCP tools (MCPClient, normalize_mcp_name, assemble_tool_pool, no cache)

All appendix source code references verified against CC source. Config priority
corrected: claude.ai < plugin < user < project < local.

* fix: 5 regressions across s05-s19 — glob safety, todo validation, memory extraction, protocol types, dep crash

- s05-s09: glob results now filter with is_relative_to(WORKDIR) (inherited from s02)
- s06-s08: todo_write validates content/status required fields (inherited from s05)
- s09: extract_memories uses pre-compression snapshot instead of compacted messages
- s16: submit_plan docstring clarifies protocol-only (not code-level gate)
- s17-s19: match_response restores type mismatch validation (from s16)
- s17-s19: claim_task deps list handles missing dep files without crashing

* fix: s12 Todo V2 logic reversal, s14/s15 cron range validation, s18/s19 worktree name validation

- s12 README (zh/en/ja): fix Todo V2 direction — interactive defaults to Task,
  non-interactive/SDK defaults to TodoWrite. Fix env var name to
  CLAUDE_CODE_ENABLE_TASKS (not TODO_V2).
- s14/s15: add _validate_cron_field with per-field range checks (minute 0-59,
  hour 0-23, dom 1-31, month 1-12, dow 0-6), step > 0, range lo <= hi.
  Replace old try/except validation that only caught exceptions.
- s18/s19: add validate_worktree_name() to remove_worktree and keep_worktree,
  not just create_worktree.

* fix: align s16-s19 teaching tool consistency

* fix pr265 chapter diagrams

* Add comprehensive s20 harness chapter

* Fix chapter smoke test regressions

* Clarify README tutorial track transition

---------

Co-authored-by: Haoran <bill-billion@outlook.com>
This commit is contained in:
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2026-05-20 21:45:38 +08:00
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# s13: Background Tasks — 慢操作放后台
[中文](README.md) · [English](README.en.md) · [日本語](README.ja.md)
s01 → ... → s11 → s12 → `s13` → [s14](../s14_cron_scheduler/) → s15 → ... → s20
> *"慢操作丢后台, agent 继续处理"* — 后台线程跑命令, 完成后注入通知。
>
> **Harness 层**: 后台 — 异步执行, 不阻塞主循环。
---
## 问题
你用过洗衣机吗把衣服扔进去按下启动然后去干别的——做饭、回消息、看论文。30 分钟后洗衣机"滴滴滴"提醒你:好了。你不会站在洗衣机前面干等 30 分钟。
Agent 的 bash 工具也一样。`pip install torch` 要 10 分钟,`npm run build` 要 3 分钟。这些命令一跑Agent 就在等 bash 工具返回,没法利用这段时间处理别的任务。
读文件是毫秒级,不等。`git status` 一秒内返回,不等。但 `npm install`分钟级。Agent 等 10 分钟什么都不做,而 LLM 按 token 计费,空转就是浪费。
---
## 解决方案
![Background Tasks Overview](images/background-tasks-overview.svg)
教学代码沿用 S12 的简化任务系统和 prompt 组装为了聚焦后台任务省略完整错误恢复、记忆和技能系统。唯一的变动慢操作扔到后台线程Agent 继续跑循环,后台完成后把通知注入到对话里。
同步 vs 后台:
| | 同步 (s12) | 后台 (s13) |
|---|---|---|
| 慢操作 | Agent 干等 | 后台线程执行 |
| Agent 空闲 | 是 | 否,继续处理 |
| 结果 | 立即返回 | 下轮注入通知 |
| 判断标准 | — | `run_in_background` 参数(模型显式请求),启发式兜底 |
---
## 工作原理
### should_run_background: 显式请求优先,启发式兜底
模型通过 bash 工具的 `run_in_background` 参数显式请求后台执行。如果模型没指定,教学版用关键词启发式兜底:
```python
def is_slow_operation(tool_name: str, tool_input: dict) -> bool:
"""Fallback heuristic: commands likely to take > 30s."""
if tool_name != "bash":
return False
cmd = tool_input.get("command", "").lower()
slow_keywords = ["install", "build", "test", "deploy", "compile",
"docker build", "pip install", "npm install",
"cargo build", "pytest", "make"]
return any(kw in cmd for kw in slow_keywords)
def should_run_background(tool_name: str, tool_input: dict) -> bool:
"""Model explicit request takes priority; fallback to heuristic."""
if tool_input.get("run_in_background"):
return True
return is_slow_operation(tool_name, tool_input)
```
CC 的 bash 工具 schema 里有 `run_in_background: boolean` 参数(`BashTool.tsx:241`)。模型自己决定哪些命令丢后台,不靠关键词猜。教学版保留启发式作为兜底,但主路径是模型显式请求。
### start_background_task: 后台执行与生命周期
把工具调用包装成 worker 函数,扔到 daemon 线程里执行。每个后台任务有唯一 ID状态存在 `background_tasks` 字典里:
```python
_bg_counter = 0
background_tasks: dict[str, dict] = {} # bg_id → {tool_use_id, command, status}
background_results: dict[str, str] = {} # bg_id → output
background_lock = threading.Lock()
def start_background_task(block) -> str:
"""Run tool in a daemon thread. Returns background task ID."""
global _bg_counter
_bg_counter += 1
bg_id = f"bg_{_bg_counter:04d}"
def worker():
result = execute_tool(block)
with background_lock:
background_tasks[bg_id]["status"] = "completed"
background_results[bg_id] = result
with background_lock:
background_tasks[bg_id] = {
"tool_use_id": block.id,
"command": block.input.get("command", ""),
"status": "running",
}
thread = threading.Thread(target=worker, daemon=True)
thread.start()
return bg_id
```
返回 `bg_id` 而不是只返回 `[Running in background...]``daemon=True` 确保 Agent 进程退出时线程跟着退出。教学版用内存字典追踪状态;真实 CC 有 `LocalShellTaskState`,输出重定向到文件,支持停止任务、读取后续输出等完整生命周期。
### collect_background_results: 通知收集
后台任务完成后,收集结果并格式化为 `<task_notification>` 通知:
```python
def collect_background_results() -> list[str]:
"""Collect completed results as task_notification messages."""
with background_lock:
ready_ids = [bid for bid, task in background_tasks.items()
if task["status"] == "completed"]
notifications = []
for bg_id in ready_ids:
with background_lock:
task = background_tasks.pop(bg_id)
output = background_results.pop(bg_id, "")
notifications.append(
f"<task_notification>\n"
f" <task_id>{bg_id}</task_id>\n"
f" <status>completed</status>\n"
f" <command>{task['command']}</command>\n"
f" <summary>{output[:200]}</summary>\n"
f"</task_notification>")
return notifications
```
通知不复用原始 `tool_use_id`。原始 tool call 已经用占位 `tool_result` 回复了,后台完成是独立事件,用 `task_notification` 格式注入。这符合 Messages API 的工具配对语义:一个 `tool_use` 只对应一个 `tool_result`
### 循环中的集成
agent_loop 里,工具执行分两条路,通知和结果合并为一条 user 消息:
```python
results = []
for block in response.content:
if block.type != "tool_use":
continue
if should_run_background(block.name, block.input):
bg_id = start_background_task(block)
results.append({"type": "tool_result",
"tool_use_id": block.id,
"content": f"[Background task {bg_id} started] "
f"Result will be available when complete."})
else:
output = execute_tool(block)
results.append({"type": "tool_result",
"tool_use_id": block.id, "content": output})
# 通知和工具结果合入同一条 user 消息
user_content = []
bg_notifications = collect_background_results()
if bg_notifications:
for notif in bg_notifications:
user_content.append({"type": "text", "text": notif})
user_content.extend(results)
messages.append({"role": "user", "content": user_content})
```
慢操作先回一个带 `bg_id` 的占位 tool_resultLLM 知道这个命令还在跑,可以先做别的事。后台完成后,通知作为独立 text block 和当前轮的 tool_result 一起组成 user 消息。
教学版在 agent loop 继续运行时轮询后台结果。真实 CC 通过通知队列(`messageQueueManager.ts`)把后台完成事件送入后续 turn不需要等工具循环。
### 合起来跑
```
Turn 1:
LLM → bash "npm install" (run_in_background=true)
→ start_background_task → bg_0001
→ tool_result: "[Background task bg_0001 started]..."
→ LLM: "OK, I'll check later. Let me also read the config."
Turn 2:
LLM → read_file "package.json" (fast, sync)
→ tool_result: file content
→ collect: bg_0001 done! inject <task_notification>
→ LLM sees: config file + install notification in one message
```
Agent 没干等npm install 跑后台的时候,它去读了配置文件。
---
## 相对 s12 的变更
| 组件 | 之前 (s12) | 之后 (s13) |
|------|-----------|-----------|
| 执行模型 | 全部同步 | 慢操作后台线程 + 通知注入 |
| bash schema | `command` | `command` + `run_in_background` |
| 新函数 | — | `should_run_background`, `is_slow_operation`, `start_background_task`, `collect_background_results` |
| 新类型 | — | `background_tasks: dict`, `background_results: dict`, `background_lock: Lock` |
| 通知格式 | — | `<task_notification>`(不复用 tool_use_id |
| 循环行为 | 工具串行执行 | 慢操作异步,快操作同步,通知每轮收集 |
| 工具 | 8 (s12) | 8不变执行策略变了 |
---
## 试一下
```sh
cd learn-claude-code
python s13_background_tasks/code.py
```
试试这些 prompt
1. `Run pip list in the background and find all Python files in this directory`
2. `Run npm install (use run_in_background) and while waiting, read package.json`
3. `Create a task to setup the project, then run pip list in the background`
观察重点:慢操作有没有被送到后台?`bg_id` 是否返回?后台通知有没有以 `<task_notification>` 格式注入?
---
## 接下来
后台任务解决了"慢操作不阻塞"。但如果想定时做某件事呢?比如"每天早上 9 点跑测试"、"每 5 分钟检查一次服务器状态"。
s14 Cron Scheduler → 给 Agent 装一个闹钟。
<details>
<summary>深入 CC 源码</summary>
> 以下基于 CC 源码 `query.ts`211, 1054-1060, 1411-1482 行)、`services/toolUseSummary/toolUseSummaryGenerator.ts`L15 prompt 文本)、`LocalShellTask.tsx`L24-25 常量, L59-98 看门狗逻辑)、`messageQueueManager.ts`(通知队列)、`utils/task/framework.ts`L267 `enqueueTaskNotification`)的完整分析。
### 一、pendingToolUseSummaryHaiku 后台生成
CC 在每批工具执行完后,启动一个 Haiku side-query 生成工具使用摘要。发起代码在 `query.ts:1411-1482`prompt 文本定义在 `services/toolUseSummary/toolUseSummaryGenerator.ts:15`(变量名 `TOOL_USE_SUMMARY_SYSTEM_PROMPT`)。提示是 "Write a short summary label... think git-commit-subject, not sentence",过去时态,约 30 字符。
Haiku 摘要(~1s在主模型流式生成5-30s期间完成。下一轮开始前把摘要 yield 出去。SDK 消费这些摘要做移动端进度展示。
### 二、线程模型:没有真正的线程
CC 运行在 Node.js/Bun 单线程事件循环中。"后台"只是 "不 await"。`ShellCommand.background(taskId)` 把 stdout/stderr 重定向到文件,让进程独立运行。
### 三、七种后台任务类型
CC 定义了 7 种后台任务(`Task.ts:7-13``local_bash``local_agent``remote_agent``in_process_teammate``local_workflow``monitor_mcp``dream`。每种有自己的注册、生命周期和通知机制。
### 四、通知注入:命令队列
后台任务完成后通过 `enqueueTaskNotification``utils/task/framework.ts:267`)或 `enqueuePendingNotification``messageQueueManager.ts`)入队到共享命令队列。通知格式是结构化的 XML
```xml
<task_notification>
<status>completed</status>
<summary>Background command "npm test" completed (exit code 0)</summary>
</task_notification>
```
优先级分 `next` > `later``messageQueueManager.ts`)。后台任务默认 `later`(不阻塞用户输入)。消费点在 `query.ts:1566-1593`
### 五、停滞看门狗
后台 bash 任务有一个看门狗(`LocalShellTask.tsx` L24-25 常量, L59-98 逻辑定期检查输出是否停滞45 秒无增长后检测交互式提示(`(y/n)` 等),防止后台任务卡在无人响应的交互式对话框。
### 六、并发限制
前台工具调用:`CLAUDE_CODE_MAX_TOOL_USE_CONCURRENCY`(默认 10 个并发安全工具)。后台 bash 任务:没有硬性限制,它们是独立的子进程。
</details>
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