# Diagnosing Bugs (agent skill)

> Diagnosing Bugs is an agent skill (a SKILL.md file) from mattpocock/skills. Diagnosis loop for hard bugs and performance regressions. It works with Claude Code and Codex and has 278,361 GitHub stars across a repository of 15 listed skills. Install it by copying the skill folder into your agent's skills directory.

Diagnosis loop for hard bugs and performance regressions. Use when the user says "diagnose"/"debug this", or reports something broken/throwing/failing/slow. A discipline for hard bugs. Skip phases only when explicitly justified.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/mattpocock/skills |
| Skill path | skills/engineering/diagnosing-bugs/SKILL.md |
| Skill name | diagnosing-bugs |
| GitHub stars | 278,361 |
| Installs on skills.sh | 727,984 |
| License | MIT |
| Skills in repo | 15 |
| Plugin marketplace | mattpocock |
| Official | no |
| Works with | Claude Code, Codex |
| Category | Testing & QA |
| Last commit | Oct 6, 2026 |

## When it triggers

- Use when the user says "diagnose"/"debug this", or reports something broken/throwing/failing/slow.
- "diagnose"
- "debug this"

## Add this skill

### Claude Code

```sh
/plugin marketplace add mattpocock/skills
/plugin install mattpocock-skills@mattpocock
```

In the Claude apps, zip the skill folder and upload it under Customize > Skills > + > Upload a skill (code execution must be on).

### ChatGPT / Codex

```sh
git clone --depth 1 https://github.com/mattpocock/skills.git
cp -r skills/skills/engineering/diagnosing-bugs .agents/skills/diagnosing-bugs   # repo; ~/.agents/skills for all projects
```

### Cursor

```sh
git clone --depth 1 https://github.com/mattpocock/skills.git
cp -r skills/skills/engineering/diagnosing-bugs .cursor/skills/diagnosing-bugs   # project; ~/.cursor/skills for all projects
```

Sources (checked 2026-10-07): https://code.claude.com/docs/en/skills, https://support.claude.com/en/articles/12512180-using-skills-in-claude, https://learn.chatgpt.com/docs/build-skills, https://cursor.com/docs/context/skills

skills.sh listing: https://www.skills.sh/mattpocock/skills/diagnosing-bugs

---

Canonical page: https://appsgit.com/skills/mattpocock-diagnosing-bugs
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