systematic-debugging

systematic-debugging is a skill for Claude Code, Codex from Bbeierle12/Skill-MCP-Claude. It costs 32 tokens per session (793 once invoked), scanned A, original, MIT.

A step-by-step method for finding the underlying cause of bugs, failed tests, and unexpected behavior.

In plain words
What is it for?
Use it to investigate failures, trace bad values back to their source, and choose fixes based on verified causes.
Why use it?
It replaces guesswork with evidence, reproduction steps, and comparisons with working code.

Skill for Claude CodeCodex

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

Good fit Use it to investigate failures, trace bad values back to their source, and choose fixes based on verified causes.

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Install with agentmods
npx agentmods add skills/bbeierle12/skill-mcp-claude/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 Bbeierle12/Skill-MCP-Claude --skill systematic-debugging
Clone the repo
git clone --depth 1 https://github.com/Bbeierle12/Skill-MCP-Claude

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/bbeierle12/skill-mcp-claude/systematic-debugging.svg)](https://agentmods.dev/skills/bbeierle12/skill-mcp-claude/systematic-debugging)
Your own site
<a href="https://agentmods.dev/skills/bbeierle12/skill-mcp-claude/systematic-debugging"><img src="https://agentmods.dev/badge/skills/bbeierle12/skill-mcp-claude/systematic-debugging.svg" alt="Measured on agentmods" height="20"></a>
Per session 32 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 793 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 $0.00032 $0.00793
Opus 5 $0.00016 $0.00396
Sonnet 5 $0.00006 $0.00159
Haiku 4.5 $0.00003 $0.00079

Measured 3d ago against content hash 622e382df549, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, 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 3d 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/systematic-debugging/SKILL.md · 140 lines

How it starts

The opening of the file, as written. The whole thing — 140 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Systematic Debugging

Core Principle

Don't guess. Investigate systematically.

After 3 failed fix attempts, STOP and question the architecture.

Phase 1: Understand the Problem

Gather Information

  1. What is the expected behavior?
  2. What is the actual behavior?
  3. When did it start failing?
  4. What changed recently?

Reproduce Consistently

  • Create minimal reproduction case
  • Document exact steps to reproduce
  • Identify if it's deterministic or intermittent

Check the Obvious First

  • Is it plugged in? (Services running, dependencies installed)
  • Are you in the right environment?
  • Did you save the file?
  • Is the cache cleared?

Phase 2: Root Cause Tracing

Backward Tracing Technique

  1. Where does the bad value appear?
  2. What called this with the bad value?
  3. Keep tracing up until you find the source
  4. Fix at source, not at symptom

Find Working Examples

  • Locate similar working code in same codebase
  • What works that's similar to what's broken?
  • Compare against references

Identify Differences

  • What's different between working and broken?
  • List every difference, however small
  • Don't assume "that can't matter"

Phase 3: Form Hypothesis

Scientific Method

  1. Form a SINGLE hypothesis
  2. Predict what you'd see if hypothesis is true
  3. Design a test to verify
  4. Run the test
  5. If wrong, form new hypothesis based on new data

Don't Multi-Hypothesis

  • One hypothesis at a time
  • Test it completely before moving on
  • Don't mix debugging approaches

Phase 4: Implement Fix

Write Failing Test First

  • Test that reproduces the bug
  • Test should fail before fix
  • Test should pass after fix

Single Fix at a Time

  • ONE change only
  • No "while I'm here" improvements
  • No bundled refactoring

Verify Completely

  • Original test passes
  • No other tests broken
  • Issue actually resolved
  • Edge cases covered

Phase 5: If Fix Doesn't Work

After Each Failed Attempt

  1. STOP
  2. Count: How many fixes have you tried?
  3. If < 3: Return to Phase 1, re-analyze with new information
  4. If ≥ 3: STOP and question the architecture

Read the full file on GitHub · 140 lines

Files

What ships with it

1 file 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. 3d ago First seen · 140 lines · 32 tokens per session scan A 622e382df549

Subscribe to this mod's changes

systematic-debugging is a skill published in the GitHub repository Bbeierle12/Skill-MCP-Claude (8 stars, last pushed yesterday), licensed MIT. It adds 32 tokens to every session and 793 once invoked, about $0.0002 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 2026-09-03.

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