What is systematic-debugging?

A step-by-step method for investigating bugs, failed tests, and unexpected software behavior. It requires finding and confirming the underlying cause before changing code.

Use it to read error details, reproduce failures, inspect recent changes, and work through a structured debugging process.

It prevents guess-and-check patches that hide the real problem or create new failures.

systematic-debugging — Skill for Claude Code and Codex by Go1c

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 Go1c/LumioAgent --skill systematic-debugging

Clone the repo

git clone --depth 1 https://github.com/Go1c/LumioAgent

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/go1c/lumioagent/systematic-debugging/github.svg)](https://agentmods.dev/skills/go1c/lumioagent/systematic-debugging)

Your own site

<a href="https://agentmods.dev/skills/go1c/lumioagent/systematic-debugging"><img src="https://agentmods.dev/badge/skills/go1c/lumioagent/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/go1c/lumioagent/systematic-debugging"><img src="https://agentmods.dev/badge/skills/go1c/lumioagent/systematic-debugging.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,200 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.

Model	Per session	Once invoked
Fable 5.1	$0.00021	$0.01200
Opus 5.5	$0.00008	$0.00480
Sonnet 5.5	$0.00004	$0.00240
Haiku 4.5	$0.00002	$0.00120

Measured 2mo ago against content hash 96814bb5c114, 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 2mo ago.

The scan reads SKILL.md. This mod also ships 2 executable files (condition-based-waiting-example.ts, find-polluter.sh), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

.spec/skills/systematic-debugging/SKILL.md · 102 lines

How it starts

The opening of the file, as written. The whole thing — 102 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.

Violating the letter of this process is violating the spirit of debugging.

The Iron Law

NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST

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

When to Use

Any technical issue: test failures, bugs, unexpected behavior, performance problems, build failures, integration issues.

ESPECIALLY when skipping is tempting: under time pressure, "just one quick fix" seems obvious, previous fixes didn't work, or the issue seems simple. Systematic debugging is faster than guess-and-check thrashing — and simple bugs have root causes too.

The Four Phases

Complete each phase before the next.

Phase 1: Root Cause Investigation

Read error messages carefully — full stack traces, line numbers, error codes. They often contain the exact solution.
Reproduce consistently — exact steps, reliable trigger. Not reproducible → gather more data, don't guess.
Check recent changes — git diff, recent commits, new dependencies, config, environment.
Gather evidence at component boundaries (multi-component systems: CI → build → signing, API → service → DB): before proposing fixes, log what enters and exits each component, run once, and let the evidence show WHERE it breaks — then investigate that component.
Trace data flow backward — where does the bad value originate? Keep tracing up the call stack to the source; fix at the source, not the symptom. Complete technique: root-cause-tracing.md in this directory.

Phase 2: Pattern Analysis

Find similar working code in the same codebase
Read reference implementations COMPLETELY — skimming guarantees partial understanding
List every difference between working and broken, however small; don't assume "that can't matter"
Understand the dependencies, config, and assumptions involved

Read the full file on GitHub · 102 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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.

2mo ago First seen · 102 lines · 21 tokens per session scan A 96814bb5c114

Subscribe to this mod's changes

systematic-debugging is a skill published in the GitHub repository Go1c/LumioAgent (20 stars, last pushed 4mo ago), licensed MIT. It adds 21 tokens to every session and 1,200 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 2026-08-30.

Debugging

systematic-debugging next to 6 skills from other repositories
Mod	Type	Stars	Last push	Licence	Scan	Tokens	Works with
systematic-debuggingGo1c/LumioAgent	Skill	20	4mo ago	MIT	A	21	Claude Code, Codex
systematic-debuggingopen-metadata/OpenMetadata	Skill	16k	today	Apache-2.0	A	37	Claude Code
log-error-digestzebbern/claude-code-guide	Skill	4.7k	today	MIT	A	71	Claude Code, Codex
cwv-optimizeradobe/skills	Skill	326	today	Apache-2.0	A	112	Claude Code
ci-fixersipyourdrink-ltd/bernstein	Skill	1.2k	today	Apache-2.0	A	15	Claude Code, Codex
diagnosing-missing-recordingsPostHog/posthog	Skill	41k	today	none	A	76	Claude Code, Codex
triaging-web-analytics-supportPostHog/posthog	Skill	41k	today	none	A	151	Claude Code, Codex