systematic-debug

An evidence-based debugging command for finding the actual cause of a software problem.

In plain words
What is it for?
Use it to document a bug, narrow down its cause, plan a fix, and verify that the fix does not reintroduce the problem.
Why use it?
It replaces guesswork with reproduction steps, logs, tests, hypotheses, and targeted experiments that eliminate possible causes.

Command

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 commands/lab94/frenchie-skill/systematic-debug
Clone the repo
git clone --depth 1 https://github.com/Lab94/frenchie-skill
Per session 0 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 296 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 $0.00296
Opus 5 $0.00000 $0.00148
Sonnet 5 $0.00000 $0.00059
Haiku 4.5 $0.00000 $0.00030

Measured yesterday against content hash 61d89a437725, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

systematic-debug 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 yesterday.

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.

method/commands/systematic-debug.md · 38 lines

What it actually says

/systematic-debug

Debug by evidence, not guesswork.

Capture reproduction steps, expected vs actual behavior, observations, hypotheses, narrowing strategy, root cause, fix plan, and regression validation. Use logs/tests/tools to eliminate possibilities before changing code.

Aliases: /debug, /fix-bug, /frenchie-systematic-debug.

Workflow

Evidence

Collect exact error output, logs, screenshots, request/response samples, failing test output, environment details, and recent changes. Separate observed facts from assumptions.

Reproduction

Write the shortest reliable reproduction path. Include setup, command/input, expected behavior, actual behavior, and whether the issue reproduces on main/current branch.

Hypotheses

List plausible causes with confidence and the observation that would prove or disprove each one. Do not patch before at least one hypothesis has supporting evidence.

Narrowing Strategy

Use targeted tests, logging, bisecting, controlled input changes, dependency isolation, or minimal reproduction to eliminate causes. Prefer the cheapest experiment that can falsify a hypothesis.

Root Cause

State the actual mechanism, affected code path, why existing tests missed it, and why the issue appeared now.

Fix Plan

Describe the smallest safe change, files likely touched, required tests, rollback, and risk. Ask before widening scope.

Regression Validation

Add or update regression tests when feasible. Record commands, manual checks, and any residual risk in 06-test-report.md.

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. yesterday First seen · 38 lines · 0 tokens per session scan A 61d89a437725

Subscribe to this mod's changes

systematic-debug is a command published in the GitHub repository Lab94/frenchie-skill (0 stars, last pushed 3mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 296 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.