debugging

A structured method for finding the cause of bugs, failed tests, broken builds, or unexpected behavior. It uses evidence, small reproductions, hypotheses, and regression tests.

In plain words
What is it for?
Use it to preserve error evidence, narrow down failures, inspect logs, test possible causes, and verify a fix.
Why use it?
It prevents guesses and further changes from hiding the original problem or making it worse.

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/int2t05/engineering-skills/debugging
Any agent
npx skills add int2t05/engineering-skills --skill debugging
Clone the repo
git clone --depth 1 https://github.com/int2t05/engineering-skills

Made for: Claude Code, Codex.

Per session 105 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,774 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. 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 $0.00105 $0.01774
Opus 5 $0.00053 $0.00887
Sonnet 5 $0.00021 $0.00355
Haiku 4.5 $0.00011 $0.00177

Measured 2d ago against content hash 9dc7b4da3b6d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

debugging scanned grade A with 1 finding 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 2d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (references/hitl-loop-template.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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

Build a **tight feedback loop** that goes red on this bug. This is the skill — everything else is mechanical. If you have a tight pass/fail signal for _this_ bug, you will find the cause; if you don't, no amount of stari
skills/07-verify/debugging/SKILL.md · 90 lines

How it starts

The opening of the file, as written. The whole thing — 90 lines — stays where its author put it; the contents beside it link to each section on GitHub.

When to use

  • Tests fail, the build breaks, or runtime behavior doesn't match expectations
  • A bug report arrives or an error appears in logs/console
  • Something worked before and stopped
  • A performance regression needs diagnosing
  • Before proposing a fix — discipline beats guessing
  • Reading error output or logs to triage before building a full reproduction loop (see references/log-triage.md)
  • Triggers on "debug", "bug", "test failure", "unexpected behavior", "调试", "排查 bug", "读日志", "排查错误日志"

Not for: performance optimization (use performance); profiling measured slowness (use performance). Production incidents where containment must precede diagnosis (use incident-response).

Steps

Stop the line. When anything unexpected happens, stop adding features. Preserve evidence (error output, logs, repro steps). Diagnose the root cause; resume only after verification passes. Don't push past a failing test or broken build — errors compound.

Redact every secret in command output, logs, and captured artifacts before showing them — write <REDACTED> in its place. Build loops against env vars so credentials stay in the environment. If redacted output isn't enough to diagnose, say so and ask the user.

1. Reproduce (go red)

Build a tight feedback loop that goes red on this bug. This is the skill — everything else is mechanical. If you have a tight pass/fail signal for this bug, you will find the cause; if you don't, no amount of staring at code will save you. Try in roughly this order: failing test → curl/HTTP script → CLI invocation with fixture → headless browser script → replay a captured trace → throwaway harness → property/fuzz loop → bisection harness → differential loop → HITL bash script (last resort, via references/hitl-loop-template.sh).

Tighten the loop: faster (cache setup, narrow scope), sharper signal (assert the specific symptom, not "didn't crash"), more deterministic (pin time, seed RNG, isolate filesystem).

Non-deterministic bugs: the goal is a higher reproduction rate, not a clean repro. Loop the trigger 100×, parallelise, inject sleeps, narrow timing windows. A 50%-flake bug is debuggable; 1% is not.

Read the full file on GitHub · 90 lines

Files

What ships with it

4 files 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. 2d ago First seen · 90 lines · 0 tokens per session scan A 9dc7b4da3b6d

Subscribe to this mod's changes

debugging is a skill published in the GitHub repository int2t05/engineering-skills (3 stars, last pushed 13d ago), licensed MIT. It adds 105 tokens to every session and 1,774 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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