Systematic Debugging

Systematic Debugging is a skill for Claude Code, Codex from GuitarAlchemist/ga. It costs 29 tokens per session (947 once invoked), scanned A, original, MIT.

A step-by-step method for debugging software by finding the root cause before changing code. It applies to bugs, failed tests, builds, integrations, and unexpected behavior.

In plain words
What is it for?
Use it to read errors and stack traces, reproduce the issue, inspect recent changes, gather evidence, identify the cause, and only then choose a fix.
Why use it?
It reduces guesswork and avoids patches that hide the real problem or create new ones.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it to read errors and stack traces, reproduce the issue, inspect recent changes, gather evidence, identify the cause, and only then choose a fix.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/guitaralchemist/ga/systematic-debugging
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 GuitarAlchemist/ga --skill systematic-debugging
Clone the repo
git clone --depth 1 https://github.com/GuitarAlchemist/ga

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 Systematic Debugging

README.md
[![agentmods](https://agentmods.dev/badge/skills/guitaralchemist/ga/systematic-debugging/github.svg)](https://agentmods.dev/skills/guitaralchemist/ga/systematic-debugging)
Your own site
<a href="https://agentmods.dev/skills/guitaralchemist/ga/systematic-debugging"><img src="https://agentmods.dev/badge/skills/guitaralchemist/ga/systematic-debugging/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.

agentmods 80×15 button for Systematic Debugging

Your own site · 80×15
<a href="https://agentmods.dev/skills/guitaralchemist/ga/systematic-debugging"><img src="https://agentmods.dev/badge/skills/guitaralchemist/ga/systematic-debugging.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 29 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 947 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 $0.00029 $0.00947
Opus 5.5 $0.00012 $0.00379
Sonnet 5.5 $0.00006 $0.00189
Haiku 4.5 $0.00003 $0.00095

Measured 1mo ago against content hash e3125880d95a, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

Systematic Debugging 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.

.agent/skills/systematic-debugging/SKILL.md · 125 lines

How it starts

The opening of the file, as written. The whole thing — 125 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Systematic Debugging

Overview

Random fixes waste time and create new bugs. Quick patches mask underlying issues.

Core principle: ALWAYS find root cause before attempting fixes. Symptom fixes are failure.

The Iron Law

NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST

If you haven't completed Phase 1, you cannot propose fixes.

When to Use

Use for ANY technical issue:

  • Test failures
  • Bugs in production
  • Unexpected behavior
  • Performance problems
  • Build failures
  • Integration issues

Use ESPECIALLY when:

  • Under time pressure (emergencies make guessing tempting)
  • "Just one quick fix" seems obvious
  • You've already tried multiple fixes
  • Previous fix didn't work

The Four Phases

Complete each phase before proceeding to the next.

Phase 1: Root Cause Investigation

BEFORE attempting ANY fix:

  1. Read Error Messages Carefully

    • Don't skip past errors or warnings
    • Read stack traces completely
    • Note line numbers, file paths, error codes
  2. Reproduce Consistently

    • Can you trigger it reliably?
    • What are the exact steps?
    • If not reproducible → gather more data, don't guess
  3. Check Recent Changes

    • What changed that could cause this?
    • Git diff, recent commits
    • New dependencies, config changes
  4. Trace Data Flow

    • Where does bad value originate?
    • What called this with bad value?
    • Keep tracing up until you find the source

Phase 2: Pattern Analysis

  1. Find Working Examples - Locate similar working code in same codebase
  2. Compare Against References - Read reference implementation COMPLETELY
  3. Identify Differences - List every difference, however small
  4. Understand Dependencies - What settings, config, environment?

Phase 3: Hypothesis and Testing

  1. Form Single Hypothesis - "I think X is the root cause because Y"
  2. Test Minimally - Make the SMALLEST possible change
  3. Verify Before Continuing - Did it work? If not, form NEW hypothesis
  4. When You Don't Know - Say "I don't understand X", don't pretend

Read the full file on GitHub · 125 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. 1mo ago First seen · 125 lines · 29 tokens per session scan A e3125880d95a

Subscribe to this mod's changes

Systematic Debugging is a skill published in the GitHub repository GuitarAlchemist/ga (2 stars, last pushed yesterday), licensed MIT. It adds 29 tokens to every session and 947 once invoked, about $0.0001 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 2026-08-31.

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