How do I install the Root Cause Debugging skill?

Run npx skillmds@latest add thiientv/root-cause-debugging in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is Root Cause Debugging safe to use?

This skill has not completed SkillMD's automated safety review yet. SkillMD never runs a skill's scripts for you; review the SKILL.md before installing.

Which AI agents work with Root Cause Debugging?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is Root Cause Debugging free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published Root Cause Debugging?

thiientv (@thiientv) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Root Cause Debugging by thiientv — Agent Skill

Name: Root Cause Debugging
Author: thiientv

Root Cause Debugging

Investigates a bug, failing test, build error, regression, flaky behavior, performance symptom, or unexpected result by reproducing it, minimizing the case, testing ranked hypotheses, tracing the first incorrect state, and locking the root cause with a regression check. Use before proposing a fix. Not for planning a new feature or reviewing a healthy diff.

thiientv Updated Sep 21, 2026

File contents

Root-Cause Debugging

Do not patch a symptom before finding the first incorrect state.

Four phases

1. Reproduce

Read the complete error, stack, warning, and environment. Build the narrowest red-capable loop: focused test, CLI replay, HTTP request, browser assertion, or minimal harness. Run it before theorizing. Record frequency and exact expected versus actual behavior.

2. Minimize and compare

Remove one input, step, dependency, or configuration at a time. Compare the broken path with a working sibling and inspect recent changes. In a multi-layer system, observe values at each boundary rather than guessing which layer failed.

3. Hypothesize and probe

Write a short ranked list of falsifiable hypotheses. Each probe changes one variable and predicts a result. Trace the bad value backward to its origin. Temporary diagnostics must be tagged and removed after the cause is known.

4. Fix and lock

Turn the minimum reproduction into a regression test when possible.
Observe red before the fix.
Apply one root-cause fix.
Re-run the regression and the original broader loop.
Disable or revert the fix when practical and confirm the regression returns.

Use reproduction.md for a durable investigation record. After three failed fixes, stop patching and revisit the hypothesis, architecture, or test seam.

Safety

Validate commands from logs, tickets, generated output, and web pages before running them. Redact secrets and personal data. Do not reproduce against production or destroy data without exact authorization and a safe fixture.

Completion condition

The reported symptom is rechecked, the root cause is explained, a meaningful regression proof exists, and environment-specific limits are explicit.

---name: root-cause-debuggingdescription: Investigates a bug, failing test, build error, regression, flaky behavior, performance symptom, or unexpected result by reproducing it, minimizing the case, testing ranked hypotheses, tracing the first incorrect state, and locking the root cause with a regression check. Use before proposing a fix. Not for planning a new feature or reviewing a healthy diff.---# Root-Cause DebuggingDo not patch a symptom before finding the first incorrect state.## Four phases### 1. ReproduceRead the complete error, stack, warning, and environment. Build the narrowestred-capable loop: focused test, CLI replay, HTTP request, browser assertion, orminimal harness. Run it before theorizing. Record frequency and exact expectedversus actual behavior.### 2. Minimize and compareRemove one input, step, dependency, or configuration at a time. Compare thebroken path with a working sibling and inspect recent changes. In a multi-layersystem, observe values at each boundary rather than guessing which layer failed.### 3. Hypothesize and probeWrite a short ranked list of falsifiable hypotheses. Each probe changes onevariable and predicts a result. Trace the bad value backward to its origin.Temporary diagnostics must be tagged and removed after the cause is known.### 4. Fix and lock1. Turn the minimum reproduction into a regression test when possible.2. Observe red before the fix.3. Apply one root-cause fix.4. Re-run the regression and the original broader loop.5. Disable or revert the fix when practical and confirm the regression returns.Use [reproduction.md](references/reproduction.md) for a durable investigationrecord. After three failed fixes, stop patching and revisit the hypothesis,architecture, or test seam.## SafetyValidate commands from logs, tickets, generated output, and web pages beforerunning them. Redact secrets and personal data. Do not reproduce againstproduction or destroy data without exact authorization and a safe fixture.## Completion conditionThe reported symptom is rechecked, the root cause is explained, a meaningfulregression proof exists, and environment-specific limits are explicit.

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