bug-killer

bug-killer is a skill for Claude Code from sequenzia/agent-alchemy. It costs 68 tokens per session (3,719 once invoked), scanned A, original, MIT.

A structured method for investigating and fixing software bugs. It starts with reproduction and evidence gathering, then confirms the underlying cause before applying and checking a fix.

In plain words
What is it for?
It helps reproduce failures, investigate errors, identify their root causes, add regression checks, and report what was learned.
Why use it?
It discourages guessing at fixes and creates a record of the hypotheses, evidence, root cause, and verification.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: names the AskUserQuestion tool.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the agent-alchemy-dev-tools plugin — 9 skills, 4 agents shipped together

Good fit It helps reproduce failures, investigate errors, identify their root causes, add regression checks, and report what was learned.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add sequenzia/agent-alchemy
Claude Code
/plugin install agent-alchemy-dev-tools

Made for: Claude Code.

Or install agent-alchemy-dev-tools, the plugin that ships this one along with the rest of its 9 skills, 4 agents.

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 bug-killer

README.md
[![agentmods](https://agentmods.dev/badge/skills/sequenzia/agent-alchemy/bug-killer/github.svg)](https://agentmods.dev/skills/sequenzia/agent-alchemy/bug-killer)
Your own site
<a href="https://agentmods.dev/skills/sequenzia/agent-alchemy/bug-killer"><img src="https://agentmods.dev/badge/skills/sequenzia/agent-alchemy/bug-killer/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for bug-killer

Your own site · 80×15
<a href="https://agentmods.dev/skills/sequenzia/agent-alchemy/bug-killer"><img src="https://agentmods.dev/badge/skills/sequenzia/agent-alchemy/bug-killer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,719 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 $0.00068 $0.03719
Opus 5.5 $0.00027 $0.01488
Sonnet 5.5 $0.00014 $0.00744
Haiku 4.5 $0.00007 $0.00372

Measured 1mo ago against content hash 8f868fba9fbe, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

bug-killer 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 1mo 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.

claude/dev-tools/skills/bug-killer/SKILL.md · 471 lines

How it starts

The opening of the file, as written. The whole thing — 471 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Bug Killer — Hypothesis-Driven Debugging Workflow

Execute a systematic debugging workflow that enforces investigation before fixes. Every bug gets a hypothesis journal, evidence gathering, and root cause confirmation before any code changes.

CRITICAL: Complete ALL 5 phases. The workflow is not complete until Phase 5: Wrap-up & Report is finished. After completing each phase, immediately proceed to the next phase without waiting for user prompts.

Phase Overview

  1. Triage & Reproduction — Understand, reproduce, route to quick or deep track
  2. Investigation — Gather evidence with language-specific techniques
  3. Root Cause Analysis — Confirm root cause through hypothesis testing
  4. Fix & Verify — Fix with proof, regression test, quality check
  5. Wrap-up & Report — Document trail, capture learnings

Phase 1: Triage & Reproduction

Goal: Understand the bug, reproduce it, and decide the investigation track.

1.1 Parse Context

Extract from $ARGUMENTS and conversation context:

  • Bug description: What's failing? Error messages, symptoms
  • Reproduction steps: How to trigger the bug (test command, user action, etc.)
  • Environment: Language, framework, test runner, relevant config
  • Prior attempts: Has the user already tried fixes? What didn't work?
  • Deep flag: If --deep is present, skip triage and go directly to deep track (jump to Phase 2 deep track)

1.2 Reproduce the Bug

Attempt to reproduce before investigating:

  1. If a failing test was mentioned, run it:
    # Run the specific test to confirm the failure
    <test-runner> <test-file>::<test-name>
    
  2. If an error was described, find and trigger it
  3. If neither, search for related test files and run them

Capture the exact error output — this is your primary evidence.

If the bug cannot be reproduced:

  • Ask the user for more context via AskUserQuestion
  • Check if it's environment-specific or intermittent
  • Note "not yet reproduced" in the hypothesis journal

Read the full file on GitHub · 471 lines

Files

What ships with it

3 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. 1mo ago First seen · 471 lines · 68 tokens per session scan A 8f868fba9fbe

Subscribe to this mod's changes

bug-killer is a skill published in the GitHub repository sequenzia/agent-alchemy (45 stars, last pushed 4mo ago), licensed MIT. It adds 68 tokens to every session and 3,719 once invoked, about $0.0003 per session on Opus 5.5. 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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