Claude Code Thinking Skills is a catalogue of 28 portable skills that give coding agents structured procedures for reasoning about decisions, diagnosis, risk, strategy, and related problems. It is intended for Claude Code, GitHub Copilot, Codex, Cursor, and other tools that support Agent Skills.
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 skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plusgit clone --depth 1 https://github.com/tjboudreaux/cc-thinking-skillsWrote 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/tjboudreaux/cc-thinking-skills/thinking-five-whys-plus)<a href="https://agentmods.dev/skills/tjboudreaux/cc-thinking-skills/thinking-five-whys-plus"><img src="https://agentmods.dev/badge/skills/tjboudreaux/cc-thinking-skills/thinking-five-whys-plus/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/tjboudreaux/cc-thinking-skills/thinking-five-whys-plus"><img src="https://agentmods.dev/badge/skills/tjboudreaux/cc-thinking-skills/thinking-five-whys-plus.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
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 5.1 | $0.00041 | $0.00759 |
| Opus 5.5 | $0.00016 | $0.00304 |
| Sonnet 5.5 | $0.00008 | $0.00152 |
| Haiku 4.5 | $0.00004 | $0.00076 |
Grade A, and why
thinking-five-whys-plus 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 1mo 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 — 56 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Five Whys Plus
Build an evidence-linked causal chain from a known proximate fault to an actionable systemic root, then prescribe a countermeasure that would have blocked it.
When to Use
- A fault is already localized to a component, path, or subsystem.
- The proximate cause is known, but recurrence or systemic root is not.
- Prior symptom-only fixes failed and the failure returned.
- You need prevention that addresses why the proximate cause was possible.
When NOT to Use
- Fault is not localized or multiple candidate causes remain — discriminate first.
- Root is evidenced and actionable — fix it.
- No evidence can answer the next "why" — gather evidence.
- One-off error without a process, tooling, or design enabler.
- Selective defect needing IS/IS-NOT analysis.
- Forward failure forecasting before commitment.
Procedure
- State the localized problem. Record the observable symptom, confirmed component/path, time window, scope, and impact. Stop if localization is missing.
- Chain why with evidence. Make the prior answer the new effect; propose a cause; cite logs, code, config, metrics, or witnesses; name and rule out alternatives. Stop on speculation.
- Branch before descending. Ask what else could produce the same effect; keep every evidenced independent pathway. Treat the retained branches as a causal set rather than forcing one root.
- Counterfactually test each pathway and the set. For each candidate ask, "Would removing this cause block this pathway?" Then ask, "Would removing the retained set block the observed failure?" Retain independently sufficient branches whose removal blocks their own pathway; do not reject them merely because another branch could still cause the failure.
- Enforce stop criteria per branch. Stop a branch only when its cause is evidenced, controllable, actionable, recurrence-preventing, non-blame (not merely "someone erred"), and counterfactual-positive for that pathway. If it hits human error, ask why the error was possible.
- Prescribe a countermeasure for every retained root. Name the systemic fix, owner-capable action, and how recurrence will be checked. Prefer removing enabling conditions over only patching the proximate symptom.
- Stop when verified or blocked. Halt when stop criteria pass and a countermeasure is specified, or when further steps lack evidence. Do not pad by habit.
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.
- 1mo ago First seen · 56 lines · 41 tokens per session scan A 366f1d0c5e5e
thinking-five-whys-plus is a skill published in the GitHub repository tjboudreaux/cc-thinking-skills (1,674 stars, last pushed 2mo ago), licensed MIT. It adds 41 tokens to every session and 759 once invoked, about $0.0002 per session on Opus 5.5. 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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