面试题库

5 天提示词工程零基础

D1 提示词是什么、不是什么：模型如何读指令；角色 / 任务 / 格式 / 约束四要素

• 为什么规则要放系统提示而不是用户消息？请从遵从度、管控和成本三个角度说明，并指出系统提示做不到什么。Why do rules belong in the system prompt rather than the user message? Cover adherence, control, and cost, and name what the system prompt cannot guarantee.

  国内高频海外高频进阶#system-prompt#prompt-basics

  分析过程 · 先想清楚再作答

  1. 题眼在「三个角度」和「做不到什么」。只答「系统提示权重高」是背概念，面试官要看的是你有没有在生产里拼过系统提示。
  2. 拆法：遵从度看多轮稀释——用户消息会被后续对话淹没，系统提示全程生效；管控看谁能改——系统提示由后端统一拼装、用户碰不到，规则放这里才能对所有用户一致；成本看缓存——提示缓存按前缀命中，系统提示是最稳定的前缀。
  3. 「做不到什么」是区分度所在：系统提示遵从度高不等于绝对，提示注入可以让模型跑偏，所以安全边界不能只靠系统提示，要在模型外用代码兜底。
  4. 结论：规则进系统提示是为了稳定、一致、省钱；但它是「强建议」不是「硬约束」，硬约束必须在代码层实现。
  5. 追问方向：系统提示可以放在对话末尾吗？可以但不推荐——多数模型对靠前指令更敏感，且会破坏缓存前缀；另一个追问是「哪些内容不该进系统提示」，答案是每次都变的任务细节，放进去会让缓存失效且难以复用。

  How to reason about it · think before answering

  1. The tell is whether you cover all three angles and name a limitation. 'System prompts carry more weight' alone reads as memorized.
  2. Adherence: user turns get diluted as the conversation grows, the system prompt stays in force. Control: the backend assembles the system prompt and users cannot touch it, so rules apply uniformly. Cost: prompt caching matches on prefixes, and the system prompt is the most stable prefix.
  3. The limitation is the differentiator: higher adherence is not a guarantee, prompt injection can still steer the model, so security boundaries need code-level enforcement outside the model.
  4. Conclusion: rules go in the system prompt for stability, consistency and cost, but it is a strong suggestion, not a hard constraint.
  5. Follow-ups: can the system prompt go last? Possible but unwise — models weight early instructions more and it breaks the cache prefix. What should stay out? Per-request task details, which would bust the cache and hurt reuse.

  答题要点

  • 遵从度：用户消息会被多轮对话稀释，系统提示全程生效
  • 管控：系统提示由后端统一拼装，用户碰不到，规则才能对所有人一致
  • 成本：提示缓存按前缀命中，系统提示是最稳定的前缀，不变的内容集中在这里最省钱
  • 做不到的：它不是安全边界，提示注入可以绕过，硬约束必须在代码层兜底

  Key points

  • Adherence: user turns get diluted over a long conversation, the system prompt stays in force
  • Control: the backend assembles it and users cannot edit it, so rules apply to everyone
  • Cost: prompt caching matches prefixes, so stable content in the system prompt maximizes cache hits
  • Limit: it is not a security boundary; prompt injection can bypass it, so enforce hard rules in code

D5 跨模型迁移：Claude / GPT / 国产模型的差异、system prompt 组织；进入 Claude 课与 Codex 课

• 系统提示应该怎么组织才方便跨模型复用？怎么判断某一句该放哪一块？How should a system prompt be organized so it ports across models, and how do you decide which block a given sentence belongs to?

  国内高频海外高频进阶#system-prompt#model-migration

  分析过程 · 先想清楚再作答

  1. 这题看似问结构，实际在考「有没有维护过多家模型共用的一份提示词」。答「写清楚一点就能通用」的人没维护过；维护过的人会先说分块。
  2. 拆法：三块各回答一个问题。通用规则——这一句换一家模型还成立吗，成立放这里（角色、任务、完成标准、带理由的约束、schema）；厂商适配——这一句是不是只对某一家成立，是的放这里（输入包裹方式、示例风格、长度提示、拒答边界表述、结构化输出开关），每家一份整块替换；任务变量——每次调用都在变吗，是的做成参数。
  3. 两条自检是区分度：把厂商块整块删掉，剩下的还是不是一份能读懂的提示词；通用块里搜有没有任何一家的专属词（标签名、API 参数名、风格偏好）。
  4. 结论：分块的收益不只是迁移——通用块是最长最稳定的前缀，放最前面缓存命中最高；厂商块每家固定；任务变量放最后。这跟 D1 讲系统提示要放稳定内容是同一条原则的延伸。
  5. 追问：few-shot 示例算哪一块？示例的内容属于通用规则，示例的书写风格（包裹标签、代码块风格）属于厂商适配，所以示例最好也拆成「内容 + 渲染」两层，或者至少不带厂商专属标签。

  How to reason about it · think before answering

  1. It looks structural but tests whether you have maintained one prompt across vendors. 'Just write it clearly' means no; experienced people start with blocks.
  2. Three blocks, one question each. Common rules — would this sentence still hold on another vendor? Role, task, done-criteria, reasoned constraints, schema. Vendor adaptation — is this true for one vendor only? Input wrapping, example style, length hints, refusal wording, structured-output switch; one per vendor, swapped wholesale. Task variables — does this change per call? Make it a parameter.
  3. Two self-checks are the differentiator: delete the vendor block entirely and see if what remains is still a readable prompt; grep the common block for any vendor-specific token — tag names, API parameter names, style preferences.
  4. Conclusion: the payoff goes beyond migration — the common block is the longest, most stable prefix, so leading with it maximizes prompt-cache hits; vendor block fixed per vendor; variables last. It extends the D1 principle of keeping stable content in the system prompt.
  5. Follow-up: where do few-shot examples go? Their content is common, their rendering (wrapping tags, code-block style) is vendor-specific, so split examples into content plus rendering, or at least keep vendor tags out of them.

  答题要点

  • 三块：通用规则（换模型仍成立）、厂商适配（每家一份整块替换）、任务变量（每次调用的参数）
  • 判据是两个问题：换一家还成立吗；每次调用都在变吗
  • 自检：删掉厂商块剩下的仍可读；通用块里没有任何一家的专属词
  • 顺序通用、厂商、变量，最稳定的前缀在前，缓存命中最高

  Key points

  • Three blocks: common rules that hold across vendors, a per-vendor adaptation block swapped wholesale, and per-call task variables
  • Two deciding questions: does it still hold on another vendor; does it change every call
  • Self-checks: the prompt stays readable with the vendor block removed; no vendor-specific tokens in the common block
  • Order common, vendor, variables so the most stable prefix leads and cache hits are maximized