diagnosing-bugs

diagnosing-bugs is a skill for Claude Code, Codex from gtapps/claude-code-hermit. It costs 72 tokens per session (2,181 once invoked), scanned A, original, MIT.

A step-by-step method for finding the cause of difficult bugs and slowdowns by first creating a reliable way to reproduce and detect the problem.

In plain words
What is it for?
Use it to investigate broken, failing, throwing, or slow code with failing tests, HTTP requests, logs, stack traces, instrumentation, and related architecture notes.
Why use it?
It prevents guesswork by requiring a clear pass/fail signal before testing possible causes. It also separates temporary debugging evidence from reusable lessons.

Skill for Claude CodeCodex

Part of the claude-code-dev-hermit plugin — 7 skills, 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/gtapps/claude-code-hermit/diagnosing-bugs
Any agent
npx skills add gtapps/claude-code-hermit --skill diagnosing-bugs
Clone the repo
git clone --depth 1 https://github.com/gtapps/claude-code-hermit

Made for: Claude Code, Codex.

Or install claude-code-dev-hermit, the plugin that ships this one along with the rest of its 7 skills, 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 diagnosing-bugs

README.md
[![agentmods](https://agentmods.dev/badge/skills/gtapps/claude-code-hermit/diagnosing-bugs.svg)](https://agentmods.dev/skills/gtapps/claude-code-hermit/diagnosing-bugs)
Your own site
<a href="https://agentmods.dev/skills/gtapps/claude-code-hermit/diagnosing-bugs"><img src="https://agentmods.dev/badge/skills/gtapps/claude-code-hermit/diagnosing-bugs.svg" alt="Measured on agentmods" height="20"></a>
Per session 72 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,181 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 5.1 $0.00072 $0.02181
Opus 5 $0.00036 $0.01091
Sonnet 5 $0.00014 $0.00436
Haiku 4.5 $0.00007 $0.00218

Measured 5d ago against content hash d80f1dbdfa55, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-05, from the pricing page.

Security

Grade A, and why

diagnosing-bugs 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 5d 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.

Makes network callslowCapability

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

Phase 1 is done when the loop is **tight** and **red-capable**: you can name **one command** — a script path, a test invocation, a curl — that you have **already run at least once** (paste the invocation and its output),
plugins/claude-code-dev-hermit/skills/diagnosing-bugs/SKILL.md · 144 lines

How it starts

The opening of the file, as written. The whole thing — 144 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Diagnosing Bugs

A discipline for hard bugs. Skip phases only when explicitly justified.

When exploring the codebase, consult .claude-code-hermit/compiled/ (hermit knowledge base — architecture decisions and codebase health assessments) to build a mental model of relevant modules before reading source. Check any ADRs in the area you're touching.

Diagnostic byproducts (failing-test output, stack traces, repro snapshots, instrumentation logs) go in .claude-code-hermit/raw/ — ephemeral inputs under analysis, not .claude-code-hermit/compiled/. Reusable lessons from the diagnosis go to auto-memory.

Phase 1 — Build a feedback loop

This is the skill. Everything else is mechanical. If you have a tight pass/fail signal for the bug — one that goes red on this bug — you will find the cause; bisection, hypothesis-testing, and instrumentation all just consume it. If you don't have one, no amount of staring at code will save you.

Spend disproportionate effort here. Be aggressive. Be creative. Refuse to give up.

Ways to construct one — try them in roughly this order

  1. Failing test at whatever seam reaches the bug — unit, integration, e2e.
  2. Curl / HTTP script against a running dev server.
  3. CLI invocation with a fixture input, diffing stdout against a known-good snapshot.
  4. Headless browser script (Playwright / Puppeteer) — drives the UI, asserts on DOM/console/network.
  5. Replay a captured trace. Save a real network request / payload / event log to disk (in .claude-code-hermit/raw/); replay it through the code path in isolation.
  6. Throwaway harness. Spin up a minimal subset of the system (one service, mocked deps) that exercises the bug code path with a single function call.
  7. Property / fuzz loop. If the bug is "sometimes wrong output", run 1000 random inputs and look for the failure mode.
  8. Bisection harness. If the bug appeared between two known states (commit, dataset, version), automate "boot at state X, check, repeat" so you can git bisect run it.
  9. Differential loop. Run the same input through old-version vs new-version (or two configs) and diff outputs.
  10. HITL bash script. Last resort. If a human must click, write a script that documents the exact steps and captures output so the loop is still structured.

Read the full file on GitHub · 144 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. 5d ago First seen · 144 lines · 72 tokens per session scan A d80f1dbdfa55

Subscribe to this mod's changes

diagnosing-bugs is a skill published in the GitHub repository gtapps/claude-code-hermit (74 stars, last pushed today), licensed MIT. It adds 72 tokens to every session and 2,181 once invoked, about $0.0004 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 2026-08-30.

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