debugging

A debugging guide for finding the cause of software problems, starting with simple checks and then choosing either a fast or a more detailed investigation.

In plain words
What is it for?
Use it when code fails, crashes, behaves unexpectedly, or produces an error message. It helps decide whether a small direct fix is enough or a fuller investigation is needed.
Why use it?
It reduces guesswork by checking common causes such as typos, missing dependencies, stale builds, wrong branches, and configuration errors first.

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

Made for: Claude Code, Codex.

Per session 6 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,023 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 $0.00006 $0.02023
Opus 5 $0.00003 $0.01012
Sonnet 5 $0.00001 $0.00405
Haiku 4.5 $0.00001 $0.00202

Measured 3d ago against content hash e0b3c7fce05b, 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 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/debugging/SKILL.md · 199 lines

How it starts

The opening of the file, as written. The whole thing — 199 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Debugging optimizes for certainty, not speed. Speed is a byproduct of certainty. Debugging always starts by ruling out trivial causes. If not sufficient, there are two different paths to pursue: Fast Path and Normal Path.

Quick Wins (30 seconds max)

First check the no brainers:

  • Typo / wrong variable name
  • Missing import / uninstalled dependency
  • Stale cache / needs rebuild
  • Wrong branch / uncommitted changes
  • Environment variable missing / misconfigured
  • Runtime / compiler version mismatch
  • Unexpected input shape / encoding / locale

If any of these is the cause → fix directly, no protocol needed.

Fast Path Debugging

Note: Regular tasks have their own FAST PATH (Rule 4).

Eligible when ALL true:

  • Bug conditions are obvious and need no report intake.
  • Stacktrace/error points directly to fault location (no inference needed)
  • Single hypothesis survives first inspection (no competing explanations)
  • Fix is self-evident from the bug (seeing the problem IS seeing the solution)
  • Localized (single file, single function)
  • Deterministic (not flaky)

Constraint: No refactor, no cleanup, no opportunistic improvements. Fix the bug and stop.

Format:

Mode: Debug (Fast)
Bug: [one-line: location + cause]
Fix: [one-line change]
Verify: [test/command] → [expected outcome]
Proceed (P)?

The above verification should be successful for the bug to be considered fixed.

Escalation: If fix fails on first attempt → undo the fix, then escalate to normal path. No second tries in fast mode. If new information contradicts the initial hypothesis → abandon Fast Path immediately. Don't bend the hypothesis to fit.

Normal Path Debugging

Bug Report Intake

Before qualification, ground the report:

  • Where? (local / CI / staging / prod)
  • What branch/version?
  • Since when? (always / recent / after X)
  • Who's affected? (just me / others / unknown)
  • What was already tried?

If critical context is missing, ask before proceeding.

Mode Selection

When debugging detected, ask: "Debugging in [collaboration mode] because [reason]. Override?"

Read the full file on GitHub · 199 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 · 199 lines · 6 tokens per session scan A e0b3c7fce05b

Subscribe to this mod's changes

debugging is a skill published in the GitHub repository liza-mas/liza (362 stars, last pushed 6d ago), licensed Apache-2.0. It adds 6 tokens to every session and 2,023 once invoked, about $0.0000 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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