Code Design Rationale Investigator
cursor/plugins
Digs into why code is shaped the way it is by checking git history, pull requests and connected tools in parallel, then reporting a cited read on the tradeoffs.
When a fault is localized and the proximate cause is known but the systemic root is not, chain evidence-linked whys with a counterfactual stop and a countermeasure.
Install Thinking Five Whys Plus
$ npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install tjboudreaux/cc-thinking-skills thinking-five-whys-plus --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/tjboudreaux/cc-thinking-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/thinking-five-whys-plus .claude/skills/thinking-five-whys-plus && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "thinking-five-whys-plus" agent skill from https://github.com/tjboudreaux/cc-thinking-skills/tree/main/skills/thinking-five-whys-plus into .claude/skills/thinking-five-whys-plus/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "thinking-five-whys-plus", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/tjboudreaux/cc-thinking-skills/tree/main/skills/thinking-five-whys-plusType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install tjboudreaux/cc-thinking-skills thinking-five-whys-plus --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/tjboudreaux/cc-thinking-skills.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/thinking-five-whys-plus .agents/skills/thinking-five-whys-plus && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "thinking-five-whys-plus" agent skill from https://github.com/tjboudreaux/cc-thinking-skills/tree/main/skills/thinking-five-whys-plus into .agents/skills/thinking-five-whys-plus/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "thinking-five-whys-plus", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install tjboudreaux/cc-thinking-skills thinking-five-whys-plus --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/tjboudreaux/cc-thinking-skills.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/thinking-five-whys-plus .cursor/skills/thinking-five-whys-plus && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "thinking-five-whys-plus" agent skill from https://github.com/tjboudreaux/cc-thinking-skills/tree/main/skills/thinking-five-whys-plus into .cursor/skills/thinking-five-whys-plus/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "thinking-five-whys-plus", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/tjboudreaux/cc-thinking-skills.git --path skills/thinking-five-whys-plus--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install tjboudreaux/cc-thinking-skills thinking-five-whys-plus --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/tjboudreaux/cc-thinking-skills.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/thinking-five-whys-plus .gemini/skills/thinking-five-whys-plus && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "thinking-five-whys-plus" agent skill from https://github.com/tjboudreaux/cc-thinking-skills/tree/main/skills/thinking-five-whys-plus into .gemini/skills/thinking-five-whys-plus/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "thinking-five-whys-plus", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install tjboudreaux/cc-thinking-skills thinking-five-whys-plusInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/tjboudreaux/cc-thinking-skills.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/thinking-five-whys-plus .github/skills/thinking-five-whys-plus && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "thinking-five-whys-plus" agent skill from https://github.com/tjboudreaux/cc-thinking-skills/tree/main/skills/thinking-five-whys-plus into .github/skills/thinking-five-whys-plus/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "thinking-five-whys-plus", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install tjboudreaux/cc-thinking-skills thinking-five-whys-plus --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/tjboudreaux/cc-thinking-skills.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/thinking-five-whys-plus .opencode/skills/thinking-five-whys-plus && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "thinking-five-whys-plus" agent skill from https://github.com/tjboudreaux/cc-thinking-skills/tree/main/skills/thinking-five-whys-plus into .opencode/skills/thinking-five-whys-plus/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "thinking-five-whys-plus", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
thinking-five-whys-plus- GitHub stars
- 1.6k
- Token cost
- ~881 tokens
- SKILL.md length
- 430 words
- Files
- 1
- Skills in repo
- 26
- Repo updated
- First seen
- Licence
- MIT
At a glance
When a fault is localized and the proximate cause is known but the systemic root is not, chain evidence-linked whys with a counterfactual stop and a countermeasure.
- Works in 7 steps: State the localized problem. Record the… → Chain why with evidence. Make the prior… → Branch before descending. Ask what else… → …
- Tasks that involve Root cause analysis
- SKILL.md covers When to Use, When NOT to Use, Procedure and Output, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Thinking Five Whys Plus is an agent skill from tjboudreaux/cc-thinking-skills. When a fault is localized and the proximate cause is known but the systemic root is not, chain evidence-linked whys with a counterfactual stop and a countermeasure.
Its SKILL.md is about 880 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in Development, covering Root cause analysis. The repository describes itself as: 28 eval-informed mental models and critical-thinking skills for Claude Code, GitHub Copilot, Codex, Cursor, and other Agent Skills-compatible tools. The licence is MIT.
When your agent uses it
- Tasks that involve Root cause analysis
Example prompts
- “/thinking-five-whys-plus”
Workflow steps
7 steps, taken from the first numbered list in SKILL.md.
- State the localized problem. Record the observable symptom, confirmed component/path, time window, scope, and impact. Stop if localization…
- Chain why with evidence. Make the prior answer the new effect; propose a cause; cite logs, code, config, metrics, or witnesses; name and…
- Branch before descending. Ask what else could produce the same effect; keep every evidenced independent pathway. Treat the retained…
- Counterfactually test each pathway and the set. For each candidate ask, "Would removing this cause block this pathway?" Then ask, "Would…
- Enforce stop criteria per branch. Stop a branch only when its cause is evidenced, controllable, actionable, recurrence-preventing…
- Prescribe a countermeasure for every retained root. Name the systemic fix, owner-capable action, and how recurrence will be checked…
- Stop when verified or blocked. Halt when stop criteria pass and a countermeasure is specified, or when further steps lack evidence. Do not…
What it can do on your machine
Read from SKILL.md and the folder at commit 7b8fece. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Thinking Five Whys Plus loads about 881 tokens when it runs. Until then it costs about 47 tokens; SKILL.md has 430 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from tjboudreaux/cc-thinking-skills at commit 7b8fece, republished under its MIT licence (© tjboudreaux). 430 words, ~881 tokens.
Download SKILL.mdSave it as
.claude/skills/thinking-five-whys-plus/SKILL.md (or your agent's skills folder).- name
- thinking-five-whys-plus
- description
- When a fault is localized and the proximate cause is known but the systemic root is not, chain evidence-linked whys with a counterfactual stop and a countermeasure.
- disable-model-invocation
- true
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.
Show full SKILL.md (77 more words)Show less
Output
Problem: <localized symptom + component>
Chain:
Why1: <cause> | Evidence: <...> | Ruled out: <...>
WhyN: ...
Causal set check: would removing all retained roots block the failure? yes/no
Roots:
- <systemic cause> | Pathway counterfactual: <...>
Countermeasure: <action that removes the enabling condition>
Verification: <how to confirm this pathway is blocked>Verification
- Falsify the chain if any step lacks evidence, if alternatives were never considered, if a retained root does not pass its pathway counterfactual, or if the full causal set does not explain the failure.
- Stop applying this skill once the root is fixed and verified, or when the problem is still pre-localization.
- Over-application guard: skip a full chain for a single known one-line defect; do not end at blame; do not invent depth without data.
© tjboudreaux, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in skills/thinking-five-whys-plus of tjboudreaux/cc-thinking-skills.
Open the folder on GitHubat commit 7b8fece
Compare with similar skills
Thinking Five Whys Plus next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Thinking Five Whys Plus this skilltjboudreaux/cc-thinking-skills | 1.6k | — | ~881 | Automated safety check: Pass | MIT | |
| Code Design Rationale Investigatorcursor/plugins | 11k | 9 repos | ~2.6k | Automated safety check: Pass | None | |
| OpenLogi macOS Permissions TriageAprilNEA/OpenLogi | 23k | — | ~2.5k | Automated safety check: Notes | Apache-2.0 | |
| Bug Finder for daisyUIsaadeghi/daisyui | 43k | — | ~2.3k | Automated safety check: Pass | MIT | |
| Root Cause Debugginggarrytan/gstack | 136k | — | ~1.4k | Automated safety check: Pass | MIT | |
| Review PRapache/shardingsphere | 21k | — | ~6.4k | Automated safety check: Pass | Apache-2.0 |
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- Official
OpenLogi macOS Permissions Triage
AprilNEA/OpenLogi
Decides whether an OpenLogi device problem on macOS is a privacy-permission (TCC) problem, using agent log lines, and says which identity needs which grant.
Bug Finder for daisyUI
saadeghi/daisyui
Investigates suspected bugs in the daisyUI monorepo through read-only analysis, then writes a decision-ready fix plan in tmp/bugs without changing any product code.
Root Cause Debugging
garrytan/gstack
Investigates bugs, errors and stack traces in phases and requires a root-cause hypothesis to be confirmed before any fix is written.
Review PR
apache/shardingsphere
Review Apache ShardingSphere or user-authorized downstream pull requests and PR discussions from public or authorized repository evidence.
Graph-Based Bug Tracing
tirth8205/code-review-graph
Traces a bug through a code knowledge graph, following callers, callees and execution flow before opening source files, within a small token budget.
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Related
Categories
Questions about Thinking Five Whys Plus
What does Thinking Five Whys Plus do?
When a fault is localized and the proximate cause is known but the systemic root is not, chain evidence-linked whys with a counterfactual stop and a countermeasure. Thinking Five Whys Plus is an agent skill from tjboudreaux/cc-thinking-skills. When a fault is localized and the proximate cause is known but the systemic root is not, chain evidence-linked whys with a counterfactual stop and a countermeasure.
When should I use Thinking Five Whys Plus?
Thinking Five Whys Plus fits situations like: tasks that involve Root cause analysis.
How do I install Thinking Five Whys Plus in Claude Code?
Run `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a claude-code`. Or copy the skill folder (skills/thinking-five-whys-plus in tjboudreaux/cc-thinking-skills) into .claude/skills/thinking-five-whys-plus in your project. Claude Code loads it when a task matches its description.
How do I install Thinking Five Whys Plus in Codex?
Run `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a codex`. Or copy the skill folder (skills/thinking-five-whys-plus in tjboudreaux/cc-thinking-skills) into .agents/skills/thinking-five-whys-plus in your project. Codex loads it when a task matches its description.
Can I use Thinking Five Whys Plus in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add tjboudreaux/cc-thinking-skills --skill thinking-five-whys-plus -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/thinking-five-whys-plus, .gemini/skills/thinking-five-whys-plus, .github/skills/thinking-five-whys-plus and .opencode/skills/thinking-five-whys-plus in your project.
What does Thinking Five Whys Plus need to run?
SKILL.md names no scripts, command-line tools or credentials: Thinking Five Whys Plus is instructions for the agent only.
Does Thinking Five Whys Plus access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Thinking Five Whys Plus safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Thinking Five Whys Plus use?
Thinking Five Whys Plus is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Thinking Five Whys Plus use?
About 881 tokens (SKILL.md is roughly 3.5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Thinking Five Whys Plus?
Skills that share tags, products or a category with Thinking Five Whys Plus: Code Design Rationale Investigator (cursor/plugins, 11k stars), OpenLogi macOS Permissions Triage (AprilNEA/OpenLogi, 23k stars), Bug Finder for daisyUI (saadeghi/daisyui, 43k stars) and Root Cause Debugging (garrytan/gstack, 136k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Thinking Five Whys Plus?
tjboudreaux (a GitHub user) maintains it in tjboudreaux/cc-thinking-skills, which has 1,613 GitHub stars. The repository holds 26 skills in this directory. The repository was last updated on August 7, 2026.
Source: tjboudreaux/cc-thinking-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.