debugging

A coding guide for investigating software failures by reproducing symptoms, isolating causes, examining evidence, and fixing the underlying bug.

In plain words
What is it for?
Use it for broken tests, regressions, flaky or timing-sensitive behavior, production incidents, and unclear failures.
Why use it?
It keeps debugging focused on verified root causes instead of guesses or fixes that only hide symptoms.

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

Made for: Claude Code, Codex.

Per session 20 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 852 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 $0.00020 $0.00852
Opus 5 $0.00010 $0.00426
Sonnet 5 $0.00004 $0.00170
Haiku 4.5 $0.00002 $0.00085

Measured yesterday against content hash e7fb12f9d4c8, 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 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.

agents/.agents/skills/debugging/SKILL.md · 82 lines

How it starts

The opening of the file, as written. The whole thing — 82 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Debugging

Iron Law

NO FIX WITHOUT ROOT-CAUSE EVIDENCE.

When to Use

  • Investigating defects, flakes, timing-sensitive bugs, regressions, production incidents, unclear failures, or "stuck" debugging sessions.

When NOT to Use

  • Planned refactors with no failing behavior; use refactoring.
  • Performance investigation where the symptom is slowness; use performance.
  • Git-history regression search mechanics; pair with git-workflow.

Core Ideas

  1. Reproduce before fixing. Change one variable per experiment.
  2. Reduce the failing case until only the bug remains. Localize by boundary: data, service, integration, application, infrastructure.
  3. Debugging should improve the human's failure model with evidence.
  4. Fix causes, not symptoms.
  5. For incidents, produce blameless learning with owned follow-up actions, never "human error" as a root cause.

Workflow

  1. Capture the exact symptom: command, input, output, stack trace, timing, environment. Reproduce reliably or record why reproduction isn't yet possible.
  2. After the third experiment, keep a short debug log. Form one hypothesis at a time, predict what else must be true, run the smallest experiment that confirms or refutes it.
  3. Before editing, state the current failure model: likely cause, evidence for it, and the observation that would disprove it.
  4. Fix the identified cause. Add a regression test or operational guard before declaring fixed.

Verification

  • The bug reproduces on pre-fix code or non-reproducibility is documented.
  • The root cause is named in one sentence, explains all observed symptoms, and identifies evidence that ruled out main alternatives.
  • The fix is one atomic change aimed at that cause, with a regression test or equivalent guard that fails before and passes after.
  • Timing-sensitive bugs were verified with non-invasive observation or replay.
  • Incident follow-ups have owners and deadlines.
  • Unproven root-cause or fix claims are reported as unproven.

Read the full file on GitHub · 82 lines

Files

What ships with it

1 file 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. yesterday First seen · 82 lines · 20 tokens per session scan A e7fb12f9d4c8

Subscribe to this mod's changes

debugging is a skill published in the GitHub repository kreek/consult (1 stars, last pushed 6d ago), licensed MIT. It adds 20 tokens to every session and 852 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 2026-08-31.