use-context-root-cause-analysis

use-context-root-cause-analysis is a skill for Claude Code, Codex from thkt/dotclaude. It costs 20 tokens per session (779 once invoked), scanned A, original, MIT.

A root-cause analysis method that tests competing explanations until one is supported by evidence.

In plain words
What is it for?
Comparing working and broken code, creating and testing at least three hypotheses, identifying the confirmed underlying cause, and checking whether the same cause appears elsewhere.
Why use it?
It helps prevent treating only the visible symptom or stopping at the first plausible explanation, reducing the chance that the problem returns.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/thkt/dotclaude/use-context-root-cause-analysis
Any agent
npx skills add thkt/dotclaude --skill use-context-root-cause-analysis
Clone the repo
git clone --depth 1 https://github.com/thkt/dotclaude

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 use-context-root-cause-analysis

README.md
[![agentmods](https://agentmods.dev/badge/skills/thkt/dotclaude/use-context-root-cause-analysis.svg)](https://agentmods.dev/skills/thkt/dotclaude/use-context-root-cause-analysis)
Your own site
<a href="https://agentmods.dev/skills/thkt/dotclaude/use-context-root-cause-analysis"><img src="https://agentmods.dev/badge/skills/thkt/dotclaude/use-context-root-cause-analysis.svg" alt="Measured on agentmods" height="20"></a>
Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 779 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00020 $0.00779
Opus 5 $0.00010 $0.00390
Sonnet 5 $0.00004 $0.00156
Haiku 4.5 $0.00002 $0.00078

Measured 4d ago against content hash 2d17d72c6aec, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

use-context-root-cause-analysis 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.

.ja/skills/use-context-root-cause-analysis/SKILL.md · 58 lines

What it actually says

use-context-root-cause-analysis

原則

症状ではなく根本原因を修正する。対症療法は複雑性を増やし、根本原因の修正は再発を防ぐ。

手法

${CLAUDE_SKILL_DIR}/../../rules/core/OPERATION.md § Debug Investigation Protocol が正。fork 実行では常時ロードの rules が届かないので、手順をここに写す。

  1. 動く類似コードと壊れたコードを差分比較し、違いを列挙する
  2. 原因の仮説を 3 つ以上立てる。候補の出どころは ${CLAUDE_SKILL_DIR}/references/symptom-patterns.md
  3. 各仮説を検証で潰す。1 つに絞れないうちは結論を出さない
  4. 残った仮説が根本原因。「これを直せば症状が消えるか」で確かめる
落とし穴 扱い
最初の仮説で止まる 3 つ揃うまで検証を始めない
仮説を検証せず消す 消す根拠は実行結果か証拠。もっともらしさでは消さない
抽象へ流れる アクションが取れる高さで止める。設計論まで遡らない
仮説が全部残る 差分比較の粒度を上げ、違いを 1 つずつ切り分けて再度潰す

Pattern の判定

Pattern は原因の深さでなく再発経路の有無で決まる。root cause と同じ形のコードが他にあるかを走査して分類する。

判定
Isolated 同じ形が他に無い
Recurring 近くに同じ形がある
Systematic 設計から生じ、同じ形が層をまたいで現れる

出力フォーマット

利用側は Pattern で分岐する。/fix は defense-in-depth を適用するか /research へ委譲するかを決める。

フィールド 説明
Symptom ユーザーから見た失敗
Root cause 検証で残った仮説
Pattern Isolated / Recurring / Systematic

参照ファイル

迷うこと ファイル
仮説をどう立てるか ${CLAUDE_SKILL_DIR}/references/symptom-patterns.md
消去がどう進むか ${CLAUDE_SKILL_DIR}/references/hypothesis-examples.md
Files

What ships with it

2 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.

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. 4d ago First seen · 58 lines · 20 tokens per session scan A 2d17d72c6aec

Subscribe to this mod's changes

use-context-root-cause-analysis is a skill published in the GitHub repository thkt/dotclaude (12 stars, last pushed yesterday), licensed MIT. It adds 20 tokens to every session and 779 once invoked, about $0.0001 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 2026-08-30.

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