Bug Root Cause Analyzer

Bug Root Cause Analyzer is a skill for Claude Code, Codex from Notysoty/openagentskills. It costs 20 tokens per session (1,643 once invoked), scanned A, original, MIT.

A methodical bug investigation guide that follows the program’s execution path to separate the underlying cause from visible symptoms. It uses the 5-Why technique, which repeatedly asks why a failure happened.

In plain words
What is it for?
Use it to diagnose unclear errors, recurring failures, flaky tests, or bugs that remained after an earlier fix.
Why use it?
It helps prevent quick patches that hide a problem without fixing the reason it occurred.

Skill for Claude CodeCodex

Which agent this was written for is unclear — built for cline. Also seen: positional $N argument; mentions Claude Code; built for cline.

Good fit Use it to diagnose unclear errors, recurring failures, flaky tests, or bugs that remained after an earlier fix.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/notysoty/openagentskills/bug-root-cause-analyzer
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.

Any agent
npx skills add Notysoty/openagentskills --skill bug-root-cause-analyzer
Clone the repo
git clone --depth 1 https://github.com/Notysoty/openagentskills

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 Bug Root Cause Analyzer

README.md
[![agentmods](https://agentmods.dev/badge/skills/notysoty/openagentskills/bug-root-cause-analyzer.svg)](https://agentmods.dev/skills/notysoty/openagentskills/bug-root-cause-analyzer)
Your own site
<a href="https://agentmods.dev/skills/notysoty/openagentskills/bug-root-cause-analyzer"><img src="https://agentmods.dev/badge/skills/notysoty/openagentskills/bug-root-cause-analyzer.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 1,643 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 $0.00020 $0.01643
Opus 5 $0.00010 $0.00822
Sonnet 5 $0.00004 $0.00329
Haiku 4.5 $0.00002 $0.00164

Measured 7d ago against content hash 2ccafd1ae844, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

Bug Root Cause Analyzer 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.

skills/bug-root-cause-analyzer/SKILL.md · 170 lines

How it starts

The opening of the file, as written. The whole thing — 170 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Bug Root Cause Analyzer

What this skill does

This skill directs the agent to work through a bug methodically — distinguishing the root cause from the symptoms, tracing the execution path that led to the failure, and producing a clear diagnosis before suggesting a fix. It applies the 5-Why technique, reads stack traces carefully, and avoids the trap of patching the symptom without understanding the cause.

Use this when you have a bug that isn't immediately obvious, when a quick fix didn't hold, or when you want to understand why something broke before deciding how to fix it.

How to use

Claude Code / Cline

Copy this file to .agents/skills/bug-root-cause-analyzer/SKILL.md in your project root.

Then ask:

  • "I'm getting a TypeError in checkout. Use the Bug Root Cause Analyzer skill to diagnose it."
  • "This test is flaky and I don't know why. Use the Bug Root Cause Analyzer skill."

Provide as much context as you can: the error message, the stack trace, the relevant code, and what you expected to happen.

Cursor

Add the instructions below to your .cursorrules or paste them into the Cursor AI pane before describing the bug.

The Prompt / Instructions for the Agent

When asked to diagnose a bug, follow this process:

Phase 1 — Gather information

Before analyzing, make sure you have:

  • The exact error message (not paraphrased)
  • The full stack trace if available
  • The code where the error originates
  • What the user expected to happen vs what actually happened
  • When the bug started (after a deploy? a specific change?)

If any of these are missing, ask for them before proceeding.

Phase 2 — Read the stack trace

  1. Start at the top of the stack trace — this is where the error was thrown, not necessarily where the bug lives.
  2. Work downward through the frames until you reach application code (skip framework internals unless you have good reason to look there).
  3. Identify the last application-code frame before the error — this is usually where the bug lives.
  4. Note the call chain from entry point to failure point.

Read the full file on GitHub · 170 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 · 170 lines · 20 tokens per session scan A 2ccafd1ae844

Subscribe to this mod's changes

Bug Root Cause Analyzer is a skill published in the GitHub repository Notysoty/openagentskills (9 stars, last pushed 23d ago), licensed MIT. It adds 20 tokens to every session and 1,643 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 2026-08-31.

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