systematic-debugging

systematic-debugging is a skill for Claude Code from bdfinst/agentic-dev-team. It costs 73 tokens per session (1,847 once invoked), scanned A, original, MIT.

A four-phase method for handling test failures, bugs, and unexpected errors: reproduce the problem, investigate it, identify its root cause, and then fix it. A root cause is the underlying reason the failure happens.

In plain words
What is it for?
Use it whenever a test fails, a bug is reported, or implementation produces an unexpected result. It guides debugging from a minimal reproduction to a verified fix.
Why use it?
It prevents guess-and-check edits that create more problems or waste time. The method requires evidence of the failure before changes are made.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter.

Part of the dev-team plugin — 98 skills, 54 agents, 4 hooks shipped together

Good fit Use it whenever a test fails, a bug is reported, or implementation produces an unexpected result. It guides debugging from a minimal reproduction to a verified fix.

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

Made for: Claude Code.

Or install dev-team, the plugin that ships this one along with the rest of its 98 skills, 54 agents, 4 hooks.

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/bdfinst/agentic-dev-team/systematic-debugging/github.svg)](https://agentmods.dev/skills/bdfinst/agentic-dev-team/systematic-debugging)
Your own site
<a href="https://agentmods.dev/skills/bdfinst/agentic-dev-team/systematic-debugging"><img src="https://agentmods.dev/badge/skills/bdfinst/agentic-dev-team/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/bdfinst/agentic-dev-team/systematic-debugging"><img src="https://agentmods.dev/badge/skills/bdfinst/agentic-dev-team/systematic-debugging.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 73 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,847 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. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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 $0.00073 $0.01847
Opus 5.5 $0.00029 $0.00739
Sonnet 5.5 $0.00015 $0.00369
Haiku 4.5 $0.00007 $0.00185

Measured 1mo ago against content hash 46f036a7fa35, 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.

plugins/dev-team/skills/systematic-debugging/SKILL.md · 131 lines

How it starts

The opening of the file, as written. The whole thing — 131 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Systematic Debugging

Overview

When LLMs hit failures, they tend to guess at fixes — changing code, re-running, changing more code. This thrashing wastes context and often makes things worse. This skill enforces a four-phase protocol that requires understanding before action. Systematic debugging resolves issues in 15-30 minutes; guess-and-fix typically takes 2-3 hours with a 40% first-attempt success rate vs 95% systematic.

Iron Law

Find root cause before attempting fixes. Symptom fixes are failure. No fixes without root cause investigation first.

Constraints

  • Do not change code until you have a root cause hypothesis
  • Do not apply more than one fix at a time
  • Do not skip the reproduction step — a bug you can't reproduce is a bug you can't verify as fixed
  • Do not guess. Investigate.
  • After 3+ failed fix attempts, question the architecture — stop patching

The Four Phases

Phase 1: Reproduce

Goal: See the failure with your own eyes (tool output).

  1. Run the failing test or trigger the error condition
  2. Read error messages thoroughly — don't skim. Stack traces contain line numbers, file paths, and often the solution.
  3. Identify the minimal reproduction — strip away everything unrelated
  4. Determine if the issue is consistent or intermittent
  5. Gate: paste the reproduction output. If you can't reproduce it, gather more data — don't speculate.

Phase 2: Investigate & Pattern Analysis

Goal: Gather facts and find working reference points.

Investigate (use as many techniques as needed):

  • Read the error: Parse the stack trace. What file, line, and function? What's the actual error type?
  • Trace the data flow: Follow the input from entry point to failure point. Where does the actual value diverge from the expected value?
  • Graph-assisted tracing: prefer CodeGraph/Repowise over hand-walking the codebase to trace the call path from symptom to source — see knowledge/codegraph-vs-graphify.md for tool selection and the fallback contract.
  • Check recent changes: What changed since this last worked? (git diff, git log)
  • Add observation points: Temporary logging or print statements at key points to see actual values
  • Multi-component systems: Add diagnostics at each component boundary — log data entering and exiting each layer to find which layer fails
  • Bisect: If the failure surface is large, narrow it down by testing midpoints

Read the full file on GitHub · 131 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 · 131 lines · 73 tokens per session scan A 46f036a7fa35

Subscribe to this mod's changes

systematic-debugging is a skill published in the GitHub repository bdfinst/agentic-dev-team (295 stars, last pushed 4d ago), licensed MIT. It adds 73 tokens to every session and 1,847 once invoked, about $0.0003 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 2026-09-03.

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