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:
gui-yue
2026-05-20 21:45:38 +08:00
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# s04: Hooks — 挂在循环上,不写进循环里
[中文](README.md) · [English](README.en.md) · [日本語](README.ja.md)
s01 → s02 → s03 → `s04` → [s05](../s05_todo_write/) → s06 → ... → s20
> *"挂在循环上, 不写进循环里"* — hook 在工具执行前后注入扩展逻辑。
>
> **Harness 层**: hook — 扩展点不侵入循环。
---
## 问题
s03 的 Agent 有权限检查了。但每次加一个新检查,比如"记录每次 bash 调用"、"操作后自动 git add",都要修改 `agent_loop` 函数。
循环很快就变成了这样:
```python
def agent_loop(messages):
while True:
# ... LLM call ...
for block in response.content:
if block.type == "tool_use":
log_to_file(block) # 加一行
check_permission(block) # 加一行
notify_slack(block) # 又加一行
output = execute(block)
auto_git_add(block) # 再加一行
# ... 很快循环就认不出来了
```
你想扩展的是 Agent 的行为,但你改的却是循环本身。循环应该是一个稳定的核心,扩展应该挂在外面。
---
## 解决方案
![Hooks Overview](images/hooks-overview.svg)
s03 的循环和权限逻辑完全保留。唯一的变动是把 `check_permission()` 从循环体内移到了 hook 上,循环不再直接调用任何检查函数,改为 `trigger_hooks("PreToolUse", block)`,由注册表决定跑什么。
四个事件,覆盖一个完整的 agent cycle
| 事件 | 触发时机 | 典型用途 |
|------|---------|---------|
| UserPromptSubmit | 用户输入提交后、进入 LLM 前 | 输入验证、注入上下文 |
| PreToolUse | 工具执行前 | 权限检查、日志记录 |
| PostToolUse | 工具执行后 | 副作用(自动 git add 等)、输出检查 |
| Stop | 循环即将退出时 | 收尾清理CC 还支持强制续跑) |
扩展通过 `register_hook()` 添加,循环只调用 `trigger_hooks()`
---
## 工作原理
**hook 注册表**:一个字典,事件名映射到回调列表。
```python
HOOKS = {
"UserPromptSubmit": [],
"PreToolUse": [],
"PostToolUse": [],
"Stop": [],
}
def register_hook(event: str, callback):
HOOKS[event].append(callback)
def trigger_hooks(event: str, *args):
for callback in HOOKS[event]:
result = callback(*args)
if result is not None: # 返回值 ≠ None → hook 说"停"
return result
return None
```
教学版中PreToolUse 的非 None 返回值会阻止本次工具执行Stop 的非 None 返回值会强制续跑。UserPromptSubmit 和 PostToolUse 的返回值未被使用。
**UserPromptSubmit**,用户输入提交后、进入 LLM 前触发。CC 中可以拦截或修改输入,教学版只做日志演示:
```python
def context_inject_hook(query: str) -> str | None:
"""Inject current working directory info into every prompt."""
print(f"\033[90m[HOOK] UserPromptSubmit: working in {WORKDIR}\033[0m")
return None # return None = no modification, let prompt through
register_hook("UserPromptSubmit", context_inject_hook)
```
在主循环中,用户输入后立即触发:
```python
query = input("s04 >> ")
trigger_hooks("UserPromptSubmit", query) # ← 进入 LLM 之前
history.append({"role": "user", "content": query})
agent_loop(history)
```
**PreToolUse / PostToolUse**,工具执行前后的 hook。s03 的权限检查逻辑现在包装成 PreToolUse hook再加一个日志 hook 和一个大输出提醒:
```python
# PreToolUse: 权限检查s03 的逻辑,从循环移到 hook
def permission_hook(block):
if block.name == "bash":
for pattern in DENY_LIST:
if pattern in block.input.get("command", ""):
return "Permission denied by deny list"
if block.name in ("write_file", "edit_file"):
path = block.input.get("path", "")
if not (WORKDIR / path).resolve().is_relative_to(WORKDIR):
choice = input(" Allow? [y/N] ").strip().lower()
if choice not in ("y", "yes"):
return "Permission denied by user"
return None
# PreToolUse: 日志
def log_hook(block):
print(f"[HOOK] {block.name}(...)")
# PostToolUse: 大文件提醒
def large_output_hook(block, output):
if len(str(output)) > 100000:
print(f"[HOOK] ⚠ Large output from {block.name}")
register_hook("PreToolUse", permission_hook)
register_hook("PreToolUse", log_hook)
register_hook("PostToolUse", large_output_hook)
```
**Stop**,循环即将退出时触发(`stop_reason != "tool_use"`)。教学版用于打印收尾统计:
```python
def summary_hook(messages: list) -> str | None:
"""Print a summary when the loop is about to stop."""
tool_count = sum(1 for m in messages
for b in (m.get("content") if isinstance(m.get("content"), list) else [])
if isinstance(b, dict) and b.get("type") == "tool_result")
print(f"\033[90m[HOOK] Stop: session used {tool_count} tool calls\033[0m")
return None # return None = allow stop, return string = force continuation
register_hook("Stop", summary_hook)
```
在 agent_loop 中,退出前触发:
```python
if response.stop_reason != "tool_use":
force = trigger_hooks("Stop", messages) # ← 退出之前
if force:
# hook returned a message → inject it and continue
messages.append({"role": "user", "content": force})
continue
return
```
**循环里只改了一处**s03 直接调用 `check_permission(block)`s04 改为 `trigger_hooks("PreToolUse", block)`
```python
for block in response.content:
if block.type != "tool_use":
continue
# s03: if not check_permission(block): ...
# s04: hook 替代硬编码
blocked = trigger_hooks("PreToolUse", block)
if blocked:
results.append({"type": "tool_result", "tool_use_id": block.id,
"content": str(blocked)})
continue
handler = TOOL_HANDLERS.get(block.name)
output = handler(**block.input) if handler else f"Unknown: {block.name}"
trigger_hooks("PostToolUse", block, output)
results.append({"type": "tool_result", "tool_use_id": block.id,
"content": output})
```
四个 hook 覆盖了 agent cycle 的关键节点:输入→执行前→执行后→退出。循环只负责调用 trigger_hooks(),具体逻辑全在 hook 回调里。
---
## 相对 s03 的变更
| 组件 | 之前 (s03) | 之后 (s04) |
|------|-----------|-----------|
| 扩展方式 | check_permission() 硬编码在循环里 | HOOKS 注册表 + trigger_hooks() |
| 新函数 | — | register_hook, trigger_hooks |
| hook 回调 | — | context_inject_hook, permission_hook, log_hook, large_output_hook, summary_hook |
| 循环 | 直接调用 check_permission() | 调用 trigger_hooks("PreToolUse", ...) |
| 退出控制 | 无 | trigger_hooks("Stop", ...) 可阻止退出 |
| 输入拦截 | 无 | trigger_hooks("UserPromptSubmit", ...) 可注入上下文 |
---
## 试一下
```sh
cd learn-claude-code
python s04_hooks/code.py
```
试试这些 prompt
1. `Read the file README.md`(应该直接通过,观察 hook 日志)
2. `Create a file called test.txt`(通过后观察 PostToolUse 是否触发)
3. `Delete all temporary files in /tmp`bash + rm 触发权限 hook
观察重点:每次工具执行前,是否出现了 `[HOOK]` 日志?权限被拒时,是 hook 拦截的还是循环里硬编码的?
---
## 接下来
Agent 现在能安全执行操作了。但它有没有停下来想过"我应该先做什么,再做什么"?给它一个复杂任务,它是一上来就动手,还是先列个计划?
s05 TodoWrite → 给 Agent 一个计划工具。先列清单,再做。
<details>
<summary>深入 CC 源码</summary>
> 以下基于 CC 源码 `toolHooks.ts`650 行)、`hooks.ts`、`stopHooks.ts`、`coreTypes.ts` 的完整分析。
### 一、Hook 事件:不止这 4 个,而是 27 个
教学版只讲了 PreToolUse 和 PostToolUse。CC 实际有 27 个 hook 事件(`coreTypes.ts:25-53`
| 类别 | 事件 |
|------|------|
| 工具相关 | `PreToolUse`, `PostToolUse`, `PostToolUseFailure` |
| 会话相关 | `SessionStart`, `SessionEnd`, `Stop`, `StopFailure`, `Setup` |
| 用户交互 | `UserPromptSubmit`, `Notification`, `PermissionRequest`, `PermissionDenied` |
| 子 Agent | `SubagentStart`, `SubagentStop` |
| 压缩相关 | `PreCompact`, `PostCompact` |
| 团队相关 | `TeammateIdle`, `TaskCreated`, `TaskCompleted` |
| 其他 | `Elicitation`, `ElicitationResult`, `ConfigChange`, `WorktreeCreate`, `WorktreeRemove`, `InstructionsLoaded`, `CwdChanged`, `FileChanged` |
教学版只讲 4 个核心事件UserPromptSubmit、PreToolUse、PostToolUse、Stop因为它们覆盖了一个完整 agent cycle 的关键节点。其他 23 个都是同样的模式。
### 二、HookResult 常用字段摘录
CC 的 `HookResult``types/hooks.ts:260-275`)有 14 个字段,以下是常用字段:
| 字段 | 类型 | 用途 |
|------|------|------|
| `message` | Message | 可选 UI 消息 |
| `blockingError` | HookBlockingError | 阻塞错误 → 注入对话让模型自纠 |
| `outcome` | success/blocking/non_blocking_error/cancelled | 执行结果 |
| `preventContinuation` | boolean | 阻止后续执行 |
| `stopReason` | string | 停止原因描述 |
| `permissionBehavior` | allow/deny/ask/passthrough | hook 返回权限决策 |
| `updatedInput` | Record | 修改工具输入 |
| `additionalContext` | string | 附加上下文 |
| `updatedMCPToolOutput` | unknown | MCP 工具输出修改 |
### 三、关键不变式Hook 'allow' 不能绕过 deny/ask 规则
这是 CC 权限系统最重要的安全设计(`toolHooks.ts:325-331`**hook 返回 allow 时,仍然要检查 settings.json 的 deny/ask 规则**。即使用户的 hook 脚本说"允许",如果在 settings.json 中禁用了这个工具,操作仍然会被阻止。
教学版没有这个层次,只把 PreToolUse 的非 None 返回值解释为阻止本次工具执行。这在教学场景中够了,但在生产环境中会形成安全漏洞。
### 四、stopHookActive 机制
CC 的 Stop hooks 有一个防无限循环机制(`query.ts:212,1300``stopHookActive` 状态字段。当 stop hooks 产生 blockingError 时,循环带 `stopHookActive: true` 重入下一轮。后续迭代中 stop hooks 看到这个标志就不会再次触发。这防止了一个永不停机的 bug模型自纠后 stop hook 再次报错 → 模型再自纠 → stop hook 再报错...
### 五、hook_stopped_continuation
PostToolUse hooks 返回 `preventContinuation: true` 时,会产生一个 `hook_stopped_continuation` 附件(`toolHooks.ts:117-130`。query.tsL1388-1393检测到后设置 `shouldPreventContinuation = true`,循环退出。这是 "hook 优雅地让 Agent 停机" 的机制,不是崩溃,是完成。
### 教学版的简化是刻意的
- 27 个事件 → 4 个UserPromptSubmit/PreToolUse/PostToolUse/Stop覆盖 agent cycle 关键节点
- 14 个字段 → 简单的返回值None = 继续,非 None = 阻止/续跑):心智负担降到最低
- Hook allow vs deny/ask 不变式 → 省略:教学版没有 settings.json 层
- stopHookActive → 省略:教学版 Stop hook 只做简单续跑,不涉及防无限循环机制
</details>
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