debugging

A step-by-step method for finding and fixing software bugs by reproducing the failure, tracing its root cause, testing one explanation at a time, and verifying the fix.

In plain words
What is it for?
Use it for errors, broken or flaky tests, regressions, stack traces, and unexpected behavior.
Why use it?
It helps avoid guessing at fixes that hide the problem or create new bugs.

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

Made for: Claude Code, Codex.

Per session 65 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 842 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 $0.00065 $0.00842
Opus 5 $0.00032 $0.00421
Sonnet 5 $0.00013 $0.00168
Haiku 4.5 $0.00006 $0.00084

Measured 2d ago against content hash 17865b87fc46, 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 2d 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.

distillery/generated-skills/debugging/SKILL.md · 74 lines

How it starts

The opening of the file, as written. The whole thing — 74 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Debugging

The Iron Law

Never propose a fix without first identifying the root cause. "Quick fix now, investigate later" is forbidden — it creates harder bugs.

Process

1. Reproduce — make the bug consistent. If intermittent, run N times under stress or simulate poor conditions (slow network, low memory) until it triggers reliably.

2. Investigate — trace backward through the call chain from the symptom. Add diagnostic logging at each component boundary. Compare working vs broken state using a differential table (environment, version, data, timing — what changed?).

3. Hypothesize and test — one change at a time. If a hypothesis is wrong, fully revert before testing the next. Use git bisect to find regressions efficiently.

4. Fix and verify — create a failing test FIRST, then fix. Run the test. Confirm the original reproduction case passes. No completion claims without fresh verification evidence.

Three-Fix Threshold

After 3 failed fix attempts, STOP. The problem is likely architectural, not a surface bug. Step back and question assumptions about how the system works. Read the actual code path end-to-end instead of spot-checking.

Escalation: Competing Hypotheses

When the cause is unclear across multiple components, use Analysis of Competing Hypotheses:

  • Generate hypotheses across failure modes: logic error, data issue, state problem, integration failure, resource exhaustion, environment
  • Investigate each with evidence: Direct (strong), Correlational (medium), Testimonial (weak)
  • Cite evidence with file:line references
  • Rank by confidence. If multiple hypotheses are equally supported, suspect compound causes.

Intermittent Issues

  • Track with correlation IDs across distributed components
  • Race conditions: look for shared mutable state, check-then-act patterns, missing locks
  • Resource exhaustion: monitor memory growth, connection pool depletion, file descriptor leaks
  • Timing-dependent: replace arbitrary sleep() with condition-based polling — wait for the actual state, not a duration

Read the full file on GitHub · 74 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. 2d ago First seen · 74 lines · 65 tokens per session scan A 17865b87fc46

Subscribe to this mod's changes

debugging is a skill published in the GitHub repository iliaal/whetstone (32 stars, last pushed 3d ago), licensed MIT. It adds 65 tokens to every session and 842 once invoked, about $0.0003 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.