reproduce-bug

reproduce-bug is a skill for Claude Code from marchatton/agent-skills. It costs 27 tokens per session (754 once invoked), scanned A, original, MIT.

A bug-investigation workflow that starts with a test showing the problem, then uses logs, browser checks, and screenshots to reproduce it.

In plain words
What is it for?
Investigating GitHub issues, examining application logs, reproducing browser-related problems, and verifying fixes with tests.
Why use it?
It helps developers understand and prove a bug before attempting a fix, so changes can be checked against the original failure.

Skill for Claude Code

Written for Claude Code: $ARGUMENTS substitution. Also seen: mentions subagents; installed under .agents/ (shared by several agents).

Good fit Investigating GitHub issues, examining application logs, reproducing browser-related problems, and verifying fixes with tests.

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Install with agentmods
npx agentmods add skills/marchatton/agent-skills/reproduce-bug
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.

Any agent
npx skills add marchatton/agent-skills --skill reproduce-bug
Clone the repo
git clone --depth 1 https://github.com/marchatton/agent-skills

Made for: Claude Code.

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 reproduce-bug

README.md
[![agentmods](https://agentmods.dev/badge/skills/marchatton/agent-skills/reproduce-bug/github.svg)](https://agentmods.dev/skills/marchatton/agent-skills/reproduce-bug)
Your own site
<a href="https://agentmods.dev/skills/marchatton/agent-skills/reproduce-bug"><img src="https://agentmods.dev/badge/skills/marchatton/agent-skills/reproduce-bug/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 reproduce-bug

Your own site · 80×15
<a href="https://agentmods.dev/skills/marchatton/agent-skills/reproduce-bug"><img src="https://agentmods.dev/badge/skills/marchatton/agent-skills/reproduce-bug.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 27 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 754 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 $0.00027 $0.00754
Opus 5 $0.00014 $0.00377
Sonnet 5 $0.00005 $0.00151
Haiku 4.5 $0.00003 $0.00075

Measured 10d ago against content hash 0755f3b11322, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

reproduce-bug 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 10d 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.

.agents/skills/03-plan/reproduce-bug/SKILL.md · 102 lines

How it starts

The opening of the file, as written. The whole thing — 102 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Reproduce Bug Command

Look at github issue #$ARGUMENTS and read the issue description and comments.

When I report a bug, don't start by trying to fix it. Instead, start by writing a test that reproduces the bug. Then, have subagents try to fix the bug and prove it with a passing test.

Phase 1: Log Investigation

Run the following agents in parallel to investigate the bug:

  1. Task rails-console-explorer(issue_description)
  2. Task appsignal-log-investigator(issue_description)

Think about the places it could go wrong looking at the codebase. Look for logging output we can look for.

Run the agents again to find any logs that could help us reproduce the bug.

Keep running these agents until you have a good idea of what is going on.

Phase 2: Visual Reproduction with Playwright

If the bug is UI-related or involves user flows, use Playwright to visually reproduce it:

Step 1: Verify Server is Running

mcp__plugin_compound-engineering_pw__browser_navigate({ url: "http://localhost:3000" })
mcp__plugin_compound-engineering_pw__browser_snapshot({})

If server not running, inform user to start bin/dev.

Step 2: Navigate to Affected Area

Based on the issue description, navigate to the relevant page:

mcp__plugin_compound-engineering_pw__browser_navigate({ url: "http://localhost:3000/[affected_route]" })
mcp__plugin_compound-engineering_pw__browser_snapshot({})

Step 3: Capture Screenshots

Take screenshots at each step of reproducing the bug:

mcp__plugin_compound-engineering_pw__browser_take_screenshot({ filename: "bug-[issue]-step-1.png" })

Step 4: Follow User Flow

Reproduce the exact steps from the issue:

  1. Read the issue's reproduction steps

  2. Execute each step using Playwright:

    • browser_click for clicking elements
    • browser_type for filling forms
    • browser_snapshot to see the current state
    • browser_take_screenshot to capture evidence
  3. Check for console errors:

    mcp__plugin_compound-engineering_pw__browser_console_messages({ level: "error" })
    

Read the full file on GitHub · 102 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. 10d ago First seen · 102 lines · 27 tokens per session scan A 0755f3b11322

Subscribe to this mod's changes

reproduce-bug is a skill published in the GitHub repository marchatton/agent-skills (5 stars, last pushed 6mo ago), licensed MIT. It adds 27 tokens to every session and 754 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.

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