mastermind-debug

mastermind-debug is a skill for Claude Code, Codex from monoes/monomind. It costs 30 tokens per session (2,486 once invoked), scanned A, original, Apache-2.0.

A step-by-step method for finding the underlying cause of technical problems before changing code. It covers failures, bugs, unexpected behaviour, slowdowns, build failures, and integration problems.

In plain words
What is it for?
Use it to investigate test failures, production bugs, build errors, performance regressions, and other unexpected behaviour.
Why use it?
It reduces guesswork and repeated patches that only hide symptoms or create new bugs. The method requires investigation before suggesting a fix.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

Good fit Use it to investigate test failures, production bugs, build errors, performance regressions, and other unexpected behaviour.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/monoes/monomind/mastermind-debug
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 monoes/monomind --skill mastermind-debug
Clone the repo
git clone --depth 1 https://github.com/monoes/monomind

Made for: Claude Code, Codex.

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 mastermind-debug

README.md
[![agentmods](https://agentmods.dev/badge/skills/monoes/monomind/mastermind-debug/github.svg)](https://agentmods.dev/skills/monoes/monomind/mastermind-debug)
Your own site
<a href="https://agentmods.dev/skills/monoes/monomind/mastermind-debug"><img src="https://agentmods.dev/badge/skills/monoes/monomind/mastermind-debug/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 mastermind-debug

Your own site · 80×15
<a href="https://agentmods.dev/skills/monoes/monomind/mastermind-debug"><img src="https://agentmods.dev/badge/skills/monoes/monomind/mastermind-debug.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,486 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 $0.00030 $0.02486
Opus 5.5 $0.00012 $0.00994
Sonnet 5.5 $0.00006 $0.00497
Haiku 4.5 $0.00003 $0.00249

Measured 2d ago against content hash 784d650e7824, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

mastermind-debug 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.

.agents/skills/mastermind-debug/SKILL.md · 278 lines

How it starts

The opening of the file, as written. The whole thing — 278 lines — stays where its author put it; the contents beside it link to each section on GitHub.

mastermind:debug — Systematic Debugging

Overview

Random fixes waste time and create new bugs. Quick patches mask underlying issues.

Core principle: ALWAYS find root cause before attempting fixes. Symptom fixes are failure.

Violating the letter of this process is violating the spirit of debugging.

The Iron Law

NO FIXES WITHOUT ROOT CAUSE INVESTIGATION FIRST

If you haven't completed Phase 1, you cannot propose fixes.

When to Use

Use for ANY technical issue:

  • Test failures
  • Bugs in production or staging
  • Unexpected behavior
  • Performance regressions
  • Build failures
  • Integration issues

Use this ESPECIALLY when:

  • Under time pressure (emergencies make guessing tempting)
  • "Just one quick fix" seems obvious
  • You've already tried multiple fixes that didn't work
  • Previous fix didn't resolve the issue
  • You don't fully understand what's happening

Don't skip when:

  • Issue seems simple (simple bugs have root causes too)
  • You're in a hurry (systematic is faster than thrashing)
  • The user wants it fixed immediately (systematic approach finds the real fix faster)

The Four Phases

You MUST complete each phase before proceeding to the next.


Phase 1: Root Cause Investigation

BEFORE attempting ANY fix:

  1. Read Error Messages Carefully

    • Don't skim errors or warnings
    • They often contain the exact solution
    • Read stack traces completely
    • Note line numbers, file paths, error codes
  2. Reproduce Consistently

    • Can you trigger the issue reliably?
    • What are the exact steps?
    • Does it happen every time?
    • If not reproducible → gather more data, don't guess
  3. Check Recent Changes

    • What changed that could cause this?
    • git diff, recent commits, new dependencies, config changes
    • Environmental differences between working and broken states
  4. Gather Evidence in Multi-Component Systems

    WHEN the system has multiple components (CI → build → deploy, API → service → database):

Read the full file on GitHub · 278 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. 2d ago First seen · 278 lines · 30 tokens per session scan A 784d650e7824

Subscribe to this mod's changes

mastermind-debug is a skill published in the GitHub repository monoes/monomind (23 stars, last pushed 2d ago), licensed Apache-2.0. It adds 30 tokens to every session and 2,486 once invoked, about $0.0001 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 2026-10-26.

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