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30 天从前端工程师到 Agent 工程师

D17 Planner–Executor–Critic + 共享工作区：workspace state、toolBudget、并行 fan-out、review 回路

• Critic 的评审回路怎么防止陷入死循环？除了次数上限还有什么要防的？How do you keep a Critic review loop from spinning forever, and what else needs guarding besides a retry cap?

  国内高频海外高频进阶#reflection#loop-guard#reliability

  分析过程 · 先想清楚再作答

  1. 问「除了次数上限还有什么」，说明面试官已经预设你会答上限，真正在考的是你有没有真的跑过这条回路。只答上限的人拿基础分，能说出另外两种失效方式的才算过。
  2. 第一种就是无限打回：每改一版评审者挑一个新毛病，永远收敛不了。上限的作用不是省钱，是**保证流程一定会结束**。本课取最多打回 2 次、共 3 次执行，这个量级的取法是「一次有效的修改通常在第二次就完成，第三次还不行说明判据本身有问题」。
  3. 第二种是打回不说人话：评审者只回一句「不合格」，执行者拿不到可执行信息，第二稿原样再交一遍，于是必然打满上限、白烧三倍的钱。所以打回必须带具体理由，而且理由要回写进子任务的目标里带给执行者——「缺了退款结论，请补上」才是可执行的，「质量不佳」不是。
  4. 第三种最危险也最少被提到：评审者和执行者用同一个模型、同一套提示词时，它倾向于认可自己的输出。同一个模型对「什么算好答案」的偏好是一致的，让它复核自己刚写的东西，通过率会高得离谱，这道工序等于没有。缓解手段按性价比排：给评审者一份可核对的客观验收要求；换一个不同的模型来评审，哪怕更便宜；把评审做成逐条打分而不是一句结论。
  5. 还要点一句框架的兜底与业务上限的区别：编排框架通常自带一个递归步数上限，但那是最后一道保险丝，不能当业务上限用——它是全图的，你不知道是哪条回路失控；而且它触发时抛异常，你连已有结果都拿不到，正好违背「降级返回」的原则。
  6. 可以预期的追问：上限用完了返回什么？答：返回已有结果并标记降级，同时把最后一次的评审意见一起带出去，让上层能判断要不要转人工——这条回路的价值不只是修好，还包括「修不好时说清楚差在哪」。

  How to reason about it · think before answering

  1. Asking what else besides a cap tells you the interviewer already expects the cap. What is really being tested is whether you have run this loop for real. The cap earns baseline credit; naming the other two failure modes is what passes.
  2. Failure one is infinite rejection: every revision draws a new complaint and nothing converges. The cap exists to guarantee termination, not to save money. Two rejections and three executions is a reasonable default, because an effective fix usually lands on the second attempt — if the third still fails, the rubric itself is the problem.
  3. Failure two is a rejection with no actionable content. If the reviewer only says not good enough, the executor has nothing to act on and resubmits the same thing, burning the full cap. Rejections must carry a specific reason, and that reason must be written back into the subtask goal. Missing the refund conclusion, please add it is actionable; poor quality is not.
  4. Failure three is the dangerous one people rarely mention: when reviewer and executor share a model and a prompt, the reviewer tends to approve its own output. A single model has consistent preferences about what a good answer looks like, so pass rates go implausibly high and the review step becomes theatre. Mitigations by value: give the reviewer an objective, checkable rubric; use a different model even a cheaper one; score item by item rather than emitting one verdict.
  5. Also distinguish the framework's safety net from your business cap: orchestration frameworks usually ship a recursion limit, but that is a last-resort fuse — it is graph-wide so you cannot tell which loop ran away, and it throws, which means you lose the partial results you were supposed to degrade to.
  6. Expect: what do you return once the cap is used up? Return what you have, flag it as degraded, and carry the last review comment out with it so the layer above can decide whether to escalate. The loop's value is not only fixing things — it is stating precisely what could not be fixed.

  答题要点

  • 次数上限的作用是保证流程一定会结束，不是省钱；本课取最多打回 2 次、共 3 次执行
  • 打回必须带具体、可执行的理由并回写进子任务目标，只说「不合格」会让执行者原样重交、必然打满上限
  • 最危险的是评审者与执行者同模型同提示词，它倾向于认可自己的输出，通过率虚高、这道工序等于没有
  • 缓解手段：给客观可核对的验收要求、换一个模型来评审、逐条打分而不是一句结论
  • 框架自带的递归上限只是保险丝，不能当业务上限：它是全图的、触发时抛异常，连已有结果都拿不到
  • 上限用完要返回已有结果加降级标记，并把最后一次评审意见带出去，供上层决定是否转人工

  Key points

  • A retry cap exists to guarantee termination, not to save money — two rejections, three executions total
  • Rejections must carry specific, actionable reasons written back into the subtask goal; not good enough guarantees an identical resubmission and a maxed-out cap
  • The most dangerous failure is a reviewer sharing model and prompt with the executor: it approves its own output, pass rates inflate, and the step becomes theatre
  • Mitigate with an objective checkable rubric, a different model for review, and item-by-item scoring instead of a single verdict
  • The framework's recursion limit is a fuse, not a business cap: it is graph-wide and it throws, so you lose the partial results you meant to degrade to
  • When the cap is spent, return what you have with a degraded flag plus the last review comment so the layer above can escalate