Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/tienenwu/fables/backend-servernpx skills add tienenwu/fables --skill backend-servergit clone --depth 1 https://github.com/tienenwu/fablesWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/tienenwu/fables/backend-server)<a href="https://agentmods.dev/skills/tienenwu/fables/backend-server"><img src="https://agentmods.dev/badge/skills/tienenwu/fables/backend-server.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00089 | $0.01757 |
| Opus 5 | $0.00044 | $0.00879 |
| Sonnet 5 | $0.00018 | $0.00351 |
| Haiku 4.5 | $0.00009 | $0.00176 |
Grade A, and why
backend-server-playbook scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 63 lines — stays where its author put it; the contents beside it link to each section on GitHub.
🌐 English version · 繁體中文（正本 / canonical）
後端 Server 開發判準手冊
主線為 Node.js/TypeScript；Go 為獨立參考檔（references/go.md），帶著 Node/TS 思維寫 Go 的坑集中在那。
核心原則
- 邊界不信任、內層信任型別：所有外部輸入（HTTP body、query、DB 以外的來源）只在進入邊界時驗一次（zod/struct tag），驗過就相信型別，內層不重複防禦性檢查。
- 狀態碼與錯誤格式是 API 契約：狀態碼不是裝飾，用錯（把 403 當 404、把驗證失敗回 500）會讓呼叫端無法自動化處理；錯誤一律走單一 envelope 含 machine-readable code。
- 交易邊界＝一個請求內、一個一致性單位：跨請求維持交易是紅線；一個 HTTP 請求對應一個交易，出邊界即提交或回滾。
- 本機綠燈不算數的東西：graceful shutdown、migration 順序、連線池耗盡、時區、secrets 遮罩——這些只在部署/高併發才爆，本機零證據力。
- 並發下沒有「應該不會同時發生」：check-then-act 一定要用 DB 約束、樂觀鎖或
SELECT FOR UPDATE收斂，不能靠「先查再寫中間沒人插入」的祈禱。
開工分流
| 情境 | 路徑 | 先讀 |
|---|---|---|
| 設計/改 endpoint、狀態碼、錯誤格式、分頁、冪等 | 先定契約再寫 handler | references/api-design.md |
| 寫 query、加 index、交易、migration | 先問鎖與相容性，再動 schema | references/data-layer.md |
| 列表變慢、query 數暴增 | 不要先加快取，先查 N+1 | references/data-layer.md §N+1 |
| 登入、授權、密碼、token、secrets | 逐條對紅線 | references/auth-security.md |
| Node/TS 的 async、型別、event loop、依賴 | 查傳播模式與邊界驗證 | references/node-ts.md |
| 寫 Go（尤其剛從 Node/TS 過來） | 先讀「Node 思維會踩的坑」 | references/go.md |
| 出 release / 部署 / 改啟動流程 | 逐條跑必查清單 | references/release-checklist.md |
| 部署後才爆、本機正常 | 先假設 shutdown/migration 順序/連線池/env | references/release-checklist.md |
紅線（絕對禁止）
- 禁止跨 HTTP 請求持有開著的 DB 交易——連線被一個使用者鎖住，連線池很快耗盡，全服務 hang。
- 禁止對驗證失敗、找不到、沒權限一律回 500 或一律回 200——狀態碼是契約，呼叫端靠它決定重試/報錯/導登入。
- 禁止用可逆 hash 或 SHA-256 存密碼——必須 bcrypt/argon2id；外洩時可逆 hash 等於明文。
- 禁止 secrets 進 git、進日誌、進錯誤回應——一次 commit 就永久外洩（git 歷史），token 進 logcat/APM 是真實資安事故。
- 禁止 Go 裡
_ = err或空if err != nil {}吞錯——每個 error 都要決定處理/包裝上拋/真的可忽略，吞掉＝把生產故障變成靜默資料損毀。 - 禁止 migration 用「先刪舊欄位／改名」一步到位——舊版程式還在跑時就讀不到欄位，部署窗口內 500 風暴；一律先加後刪兩步走。
- 禁止改測試斷言讓 CI 變綠——連紅兩次是方向錯誤訊號，退回上一決策點。
失敗訊號（該回頭，不是重試）
| 徵兆 | 多半是 | 退回 |
|---|---|---|
| 每修一個慢 query 又冒出下一個 | ORM lazy-load 造成 N+1，逐條治標 | 改 eager load / batch，見 data-layer §N+1 |
| 競態修了還偶發，加了更多 re-check | check-then-act 沒收斂到 DB 層 | 改約束/樂觀鎖/FOR UPDATE |
| 部署就有一小段 5xx 尖峰 | 沒有 graceful shutdown 或 migrate/deploy 順序錯 | release-checklist §shutdown/順序 |
| 連線池 timeout 偶發於高峰 | 交易開太久或池太小/太大 | data-layer §交易、release §連線池 |
| Go 服務記憶體緩慢上漲 | goroutine 洩漏（沒人讀的 channel、缺 context 取消） | go.md §goroutine 洩漏 |
| catch/error 分支越加越多才不炸 | 錯誤沒在邊界統一，散落各層 | node-ts §錯誤傳播 / go.md §error |
What ships with it
7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 4d ago First seen · 63 lines · 89 tokens per session scan A 76b84c76407a
backend-server-playbook is a skill published in the GitHub repository tienenwu/fables (4 stars, last pushed 1mo ago), licensed MIT. It adds 89 tokens to every session and 1,757 once invoked, about $0.0004 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.
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