systematic-debugging

A four-phase method for debugging software: reproduce the problem, trace where it fails, challenge your explanation, and compare all test runs. TDD, or test-driven development, means using tests to guide changes, but this add-on's excerpt focuses on investigation before fixes.

In plain words
What is it for?
Use it to investigate reproducible bugs, flaky tests, error paths, and proposed fixes that need evidence before implementation.
Why use it?
It prevents symptom-only patches that hide the real cause or create new bugs. It also stops work when the failure cannot be reproduced or the cause is not confirmed.

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/baphuongna/pi-crew/systematic-debugging
Any agent
npx skills add baphuongna/pi-crew --skill systematic-debugging
Clone the repo
git clone --depth 1 https://github.com/baphuongna/pi-crew

Made for: Claude Code, Codex.

Per session 13 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,081 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 $0.00013 $0.01081
Opus 5 $0.00006 $0.00541
Sonnet 5 $0.00003 $0.00216
Haiku 4.5 $0.00001 $0.00108

Measured 3d ago against content hash 6ffffe4d7771, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, 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 · 126 lines

How it starts

The opening of the file, as written. The whole thing — 126 lines — stays where its author put it; the contents beside it link to each section on GitHub.

systematic-debugging

Core principle: no fixes without root-cause investigation first. Symptom patches create new bugs and hide the real failure.

Distilled from detailed reads of systematic-debugging, root-cause tracing, TDD, and error-analysis skill patterns.

Invocation — Read Before Debugging

Before beginning any debug session, recite these four steps:

1. First is reproducibility. Can the issue be reproduced reliably? 2. Know the fail path. Where does the code break and what stops it from breaking? 3. Question your hypothesis. What would disprove it? 4. Every run is a breadcrumb. Cross-reference all of them.

If the user says "skip the ritual" → skip the recitation but still apply the four phases silently.

Refuse Gate — Do NOT Proceed Without These

Before proposing ANY fix:

  • Can you reproduce the issue reliably? (deterministic or >50% flake rate)
  • Do you know the root cause? (confirmed mechanism, not a hypothesis)
  • Have you tried to FALSIFY your hypothesis first? (disproof before proof)

If ANY answer is NO: → Stop. → State what's missing. → Do not propose a fix.

Exception: if the user explicitly says "just patch the symptom" — proceed but flag it as a symptom patch, not a root-cause fix.

Four Phases

1. Root Cause Investigation

Before any fix:

  • read error messages, stack traces, failing assertions, task status, and logs completely;
  • reproduce narrowly and record the exact command/steps;
  • check recent diffs, commits, config changes, dependency changes, and environment differences;
  • trace data/control flow across component boundaries;
  • add temporary diagnostics only when they answer a specific question.

For pi-crew, trace:

user/tool params → config resolution → team/workflow/agent discovery → model/runtime routing → child args/env → state/events/artifacts → status/UI

2. Pattern Analysis

  • Find a similar working path in the codebase.
  • Compare working vs broken behavior field-by-field.
  • Identify dependencies: config home, project root markers, env vars, locks, stale caches, provider model capabilities.
  • Do not assume small differences are irrelevant.

Read the full file on GitHub · 126 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. 3d ago First seen · 126 lines · 13 tokens per session scan A 6ffffe4d7771

Subscribe to this mod's changes

systematic-debugging is a skill published in the GitHub repository baphuongna/pi-crew (50 stars, last pushed 3d ago), licensed MIT. It adds 13 tokens to every session and 1,081 once invoked, about $0.0001 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 2026-08-30.

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