systematic-debugger

systematic-debugger is a skill for Claude Code, Codex from bestdeejay-design/agent-skills. It costs 0 tokens per session (1,376 once invoked), scanned A, original, MIT.

A structured debugging method that finds the confirmed root cause of a software bug before changing code. It uses four phases: reproduce the problem, form hypotheses, isolate the cause, then make a fix and add a regression test.

In plain words
What is it for?
Use it when a bug can be reproduced but its cause is unclear. It helps create a debugging report and guide the work from observed failure to a tested fix.
Why use it?
It reduces guesswork, quick fixes, and changes based only on speculation. It also helps record the environment, evidence, hypotheses, and follow-up test plan for others.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/bestdeejay-design/agent-skills/systematic-debugger
Any agent
npx skills add bestdeejay-design/agent-skills --skill systematic-debugger
Clone the repo
git clone --depth 1 https://github.com/bestdeejay-design/agent-skills

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-debugger

README.md
[![agentmods](https://agentmods.dev/badge/skills/bestdeejay-design/agent-skills/systematic-debugger.svg)](https://agentmods.dev/skills/bestdeejay-design/agent-skills/systematic-debugger)
Your own site
<a href="https://agentmods.dev/skills/bestdeejay-design/agent-skills/systematic-debugger"><img src="https://agentmods.dev/badge/skills/bestdeejay-design/agent-skills/systematic-debugger.svg" alt="Measured on agentmods" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,376 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
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 $0.00000 $0.01376
Opus 5 $0.00000 $0.00688
Sonnet 5 $0.00000 $0.00275
Haiku 4.5 $0.00000 $0.00138

Measured 5d ago against content hash c4bf2f0acc2f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

systematic-debugger 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 5d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/debug_log.py), 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.

skills/systematic-debugger/SKILL.md · 91 lines

How it starts

The opening of the file, as written. The whole thing — 91 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Systematic Debugger

Отладка по методу «Железного закона»: не трогаем код, пока причина не подтверждена гипотезами и данными. 4 фазы, Red Flags, Rationalization Table, регресс-тест.

Загружай этот скилл когда есть баг/неожиданное поведение и нужно найти корневую причину (root cause), а не наколеночный фикс. Скилл ведёт процесс: воспроизведение, гипотезы, изоляция, минимальный фикс + тест-регрессия.

🎯 When to use

Use this skill when:

  • «Почему это не работает?», «что-то сломалось», «неожиданный результат»
  • Нужен структурированный поиск причины, а не «попробуй вот так»
  • Баг воспроизводится, но причина неочевидна; нужно зафиксировать факты
  • Нужен отчёт для передачи коллеге/агента: среда, шаги, гипотезы, регресс-план

Do NOT use when:

  • Правка тривиальна и причина очевидна — просто сделай минимальный фикс
  • Нужно просто «посмотреть как работает X» — это explore, не отладка
  • Произошёл сбой из-за инфраструктуры (нет кода) — сначала собери факты окружения

📦 Files

  • SKILL.md — этот файл
  • scripts/debug_log.py — формирование отчёта по фазам (Python 3 stdlib)

⚙️ Iron Law (Железный закон)

Никаких изменений кода, пока причина не подтверждена минимум одной воспроизводимой гипотезой. Один фикс за раз — после каждого изменения перепроверяй по фактам.

🔧 Workflow (4 фазы)

Фаза 1 — Воспроизведение

  1. Зафиксируй точные шаги, при которых баг проявляется.
  2. Зафиксируй «факт»: что происходит на самом деле (вывод, лог, скрин).
  3. Попробуй минимизировать: убрать переменные, пока баг воспроизводится.

Фаза 2 — Гипотезы

  1. Выдвини 1..3 гипотезы о причине (не больше).
  2. Для каждой — как её проверить (команда/тест/лог) и какой результат ожидаем.
  3. Заполни Rationalization Table: гипотеза → проверка → результат → вердикт.

Фаза 3 — Изоляция причины

  1. Проверяй гипотезы по одной; после каждой проверки обновляй таблицу.
  2. Используй минимальные вмешательства: точечный лог, изолированный репродюсер.
  3. Red Flag: если «внезапно заработало» без понимания почему — это НЕ фикс.

Read the full file on GitHub · 91 lines

Files

What ships with it

2 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.

  1. 5d ago First seen · 91 lines · 0 tokens per session scan A c4bf2f0acc2f

Subscribe to this mod's changes

systematic-debugger is a skill published in the GitHub repository bestdeejay-design/agent-skills (5 stars, last pushed today), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,376 tokens. 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.