design-gate

design-gate is a skill for Claude Code, Codex from s977043/PlanGate. It costs 73 tokens per session (2,592 once invoked), scanned A, original, MIT.

A pre-coding design review for high-risk tasks that produces and evaluates a structured design document before implementation.

In plain words
What is it for?
Use it when a task is risky or complex and needs a design gate before implementation begins.
Why use it?
It prevents coding from starting without an approved description of the problem, goals, structure, failure handling, and other key decisions.

Skill for Claude CodeCodex

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable. Also seen: installed under .agents/ (shared by several agents); mentions Codex.

Runs only inside a plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else, and the catalogue could not identify which plugin ships it.

Good fit Use it when a task is risky or complex and needs a design gate before implementation begins.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

There is no command for this one: it runs only inside a plugin, and the catalogue could not identify which plugin ships it. The source is linked below.

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for design-gate

README.md
[![agentmods](https://agentmods.dev/badge/skills/s977043/plangate/design-gate.svg)](https://agentmods.dev/skills/s977043/plangate/design-gate)
Your own site
<a href="https://agentmods.dev/skills/s977043/plangate/design-gate"><img src="https://agentmods.dev/badge/skills/s977043/plangate/design-gate.svg" alt="Measured on agentmods" height="20"></a>
Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,592 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00073 $0.02592
Opus 5 $0.00036 $0.01296
Sonnet 5 $0.00015 $0.00518
Haiku 4.5 $0.00007 $0.00259

Measured 7d ago against content hash e6fbf3311edf, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

design-gate 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 7d 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.

.agents/skills/design-gate/SKILL.md · 196 lines

How it starts

The opening of the file, as written. The whole thing — 196 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Design Gate

high-risk 以上のタスクで実装前に設計書(Design Artifact)を生成・評価する。

参照解決順(.claude/rules/*.md / 導入先で必ずこの順に探す)

本 Skill は Mode 判定の正本として .claude/rules/mode-classification.md を参照する(§関連)。 このパスは上流リポジトリ基準のため、導入先では 次の順で探索する:

  1. 導入先リポジトリの .claude/rules/mode-classification.md
  2. 無ければ plugin root 配下 <plugin_root>/rules/mode-classification.md<plugin_root>Bash で ls "${CLAUDE_PLUGIN_ROOT}/rules/" を実行して展開・確認した 絶対パス(Read ツールは絶対パスを要求し環境変数を展開しないため、${CLAUDE_PLUGIN_ROOT}/... という文字列をそのまま Read しない)。変数が空・未設定ならキャッシュを glob で推測せず 3 へ進む
  3. どちらにも無い場合は 「正本 mode-classification.md を参照できなかった」と明示し、 推測で内容を補わない

Iron Law

NO CODE WITHOUT APPROVED DESIGN FIRST

high-risk 以上のモードでは、Design Artifact の 8 項目が揃い承認されるまで実装を開始しない。

Common Rationalizations

こう思ったら 現実
「シンプルだから設計不要」 シンプルなほど設計は速い。10 分の設計が数時間の手戻りを防ぐ
「急いでいるから省略」 設計なしの実装は後で手戻りになる。急ぐほど設計が必要
「前に似たことをやった」 コードベースは変化する。前回の前提が今回も成立するとは限らない
「PoC だから後で直す」 PoC は往々にして本番コードになる。設計の借金は複利で増える

Design Artifact 8 項目の入力フォーム

以下の質問にすべて答えることで Design Artifact が完成する。

1. 問題定義

質問: 何が問題か?

  • 現状はどうなっているか
  • どのような課題・不便が発生しているか
  • なぜ今対応が必要か(背景・トリガー)

2. 目的

質問: なぜ解決するか?

  • このタスクで達成したいゴールは何か
  • 解決後にどのような状態になっていてほしいか(期待効果)

3. 非目的

質問: 今回対応しないことは?

  • スコープ外として明示的に除外するもの
  • 「やらない」と決めた理由

4. 仕様

質問: 何を作るか?(具体的な機能要件)

  • 実装する機能・コンポーネントを列挙する
  • 入力・処理・出力を明示する
  • 受入基準(Acceptance Criteria)を記述する

5. 代替案

質問: 他に検討したアプローチは?(最低 2 案)

概要 メリット デメリット
案 1 ... ... ...
案 2 ... ... ...

6. 採用案

質問: 選んだアプローチと選択理由は?

  • 採用するアプローチを明示する
  • 代替案と比較した場合の優位点を述べる
  • トレードオフを認識した上で選択した旨を記述する

7. リスク

質問: 実装・運用上のリスクは?(影響度・対策付き)

リスク 影響度 発生確率 対策
リスク 1 High / Medium / Low High / Medium / Low ...
リスク 2 ... ... ...

8. テスト方針

質問: どう検証するか?

レイヤー テスト種別 カバー範囲
Unit Unit ...
Integration Integration ...
E2E E2E ...

Read the full file on GitHub · 196 lines

Changes

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.

  1. 7d ago First seen · 196 lines · 73 tokens per session scan A e6fbf3311edf

Subscribe to this mod's changes

design-gate is a skill published in the GitHub repository s977043/PlanGate (2 stars, last pushed today), licensed MIT. It adds 73 tokens to every session and 2,592 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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