systematic-debugging

systematic-debugging is a skill for Claude Code, Codex from GanyuanRan/Aegis. It costs 21 tokens per session (2,346 once invoked), scanned A, original, MIT.

A structured method for investigating bugs, failed tests, and unexpected behavior by reproducing the problem, tracing its cause, and identifying the responsible owner.

In plain words
What is it for?
Use it to examine errors and diffs, locate the source of incorrect behavior, assess effects across connected systems, and decide whether a code change is necessary.
Why use it?
It reduces guesswork and discourages applying fixes before understanding where the failure originates.

Skill for Claude CodeCodex

Part of the Aegis plugin — 22 skills, 3 commands, 1 hook shipped together

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/ganyuanran/aegis/systematic-debugging
Any agent
npx skills add GanyuanRan/Aegis --skill systematic-debugging
Clone the repo
git clone --depth 1 https://github.com/GanyuanRan/Aegis

Made for: Claude Code, Codex.

Or install Aegis, the plugin that ships this one along with the rest of its 22 skills, 3 commands, 1 hook.

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/ganyuanran/aegis/systematic-debugging.svg)](https://agentmods.dev/skills/ganyuanran/aegis/systematic-debugging)
Your own site
<a href="https://agentmods.dev/skills/ganyuanran/aegis/systematic-debugging"><img src="https://agentmods.dev/badge/skills/ganyuanran/aegis/systematic-debugging.svg" alt="Measured on agentmods" height="20"></a>
Per session 21 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,346 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 $0.00021 $0.02346
Opus 5 $0.00010 $0.01173
Sonnet 5 $0.00004 $0.00469
Haiku 4.5 $0.00002 $0.00235

Measured 4d ago against content hash 3416b67da9c4, 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 4d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (condition-based-waiting-example.ts, find-polluter.sh), 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-debugging/SKILL.md · 222 lines

How it starts

The opening of the file, as written. The whole thing — 222 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Execute

Bug, failure, or unexpected behavior:

  1. Isolate — read error, reproduce, inspect the diff, and drill upward through diagnostic layers: L1 symptom → L2 logic → L3 system → L4 architecture → L5 cross-system contract → L6 platform → L7 spec gap. Layers are observation altitudes, not one causal chain; the causal shape at the stop altitude is classified explicitly before any root claim. Stop only when causal proof accounts for the recurrence generator or reaches a T-class boundary.
  2. Identify owner — compare working behavior, trace the bad value, locate the canonical owner, and treat duplicate owners as a finding.
  3. Decide before editing — Before fixing, run Patch-Shape Triage and Ripple Signal Triage when shared logic, contracts, fallbacks, adapters, producer/consumer seams, or source-of-truth boundaries are involved. Surface Change Necessity for any new source-code path or non-trivial source edit. Run Minimality Check for a new branch, fallback, adapter, owner, or compatibility path, and Pre-Edit Complexity Check for an overloaded owner or complexity growth. After Change Necessity selects code-change and before the first repair edit, own the TDD Route for the repair slice: off skips automatic TDD; auto selects strict on any behavior, bugfix, shared/core, contract, persistence, permission, migration, producer/consumer, or meaningful regression signal. light requires every tiny/low-risk/single-owner/no-behavior-change condition; missing explicit user TDD wording is never auto-light evidence.
  4. Prove — test one hypothesis with the smallest reproduction or verification. A failing test first is required only by a recorded TDD Route: strict; with TDD Mode: off, do not require a failing test or RED/GREEN cycle. Three failed fixes means stop and question architecture.
  5. Repair and close — fix minimally at the canonical owner, verify in proportion to risk, review architecture, and close both repair and retirement tracks. If any symptom remains, stop and diagnose it separately.

Done: confidence ≥ B, causal status matches recurrence evidence or an external terminal, tracks explicit, no H signal, and required D evidence passes.

Read the full file on GitHub · 222 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. 4d ago First seen · 222 lines · 21 tokens per session scan A 3416b67da9c4

Subscribe to this mod's changes

systematic-debugging is a skill published in the GitHub repository GanyuanRan/Aegis (1,154 stars, last pushed 5d ago), licensed MIT. It adds 21 tokens to every session and 2,346 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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