What do I need to use Bug Diagnosis?

The symptom; Repro steps; Context; What's been tried.

Is Bug Diagnosis free to use?

Yes — run it free in the browser playground (no API key needed for the sponsored trial, or bring any provider key), or install it into Claude Code, Cursor, ChatGPT and more via npx pm-claude-skills. MIT-licensed and open source.

Bug Diagnosis

Q: How do I know the Bug Diagnosis output is good?

The skill verifies itself against its own quality checks: A reliable reproduction exists before any fix is attempted; The location is isolated by bisection/narrowing, not guessed; Hypotheses are ranked by likelihood × cheapness and tested in order; The stated cause is the *root* cause with evidence — not just the surface symptom.

🔵 Stable🕐 updated 2026-06-30 🔷 SkillSpec L3 pm-craft

Diagnose a bug systematically instead of guessing — reproduce, isolate, form hypotheses, and test them to root cause. Use when debugging, chasing a defect, an intermittent failure, or 'why is this happening?'. Produces a structured diagnosis: a reliable repro, the narrowed-down location, ranked hypotheses with how to test each, and the root cause + fix once found.

▶ Run it free — no key needed 📝 Grade your existing draft View SKILL.md ↗

What to give it

▸The symptom — what's wrong: expected vs. actual behavior, error/stack trace, when it started.

▸Repro steps — how to trigger it (or "can't reliably reproduce yet").

▸Context — recent changes, environment, frequency (always / intermittent / specific inputs).

▸What's been tried — so we don't repeat dead ends.

✅ The bar it holds itself to

Every skill in this library self-verifies — these are this skill's own quality checks, straight from its definition.

✓A reliable reproduction exists before any fix is attempted

✓The location is isolated by bisection/narrowing, not guessed

✓Hypotheses are ranked by likelihood × cheapness and tested in order

✓The stated cause is the *root* cause with evidence — not just the surface symptom

✓A regression test is added that fails before the fix and passes after

⚠️ What it refuses to do

Do not start changing code before the bug reliably reproduces

Do not fix the symptom and stop — trace to the underlying cause

Do not change several things at once — you won't know what fixed it (or hid it)

Do not skip the regression test — an unguarded bug comes back

Do not ignore "what's been tried" — re-running dead ends wastes the loop

Install

npx pm-claude-skills add --agent claude   # or codex · cursor · gemini · hermes
# or one-line MCP (every skill, any client):
claude mcp add pm-skills -- npx -y pm-claude-skills-mcp

Related skills

🔌 Embed this skill

Drop this on your blog, docs, or site — it renders a "Run this skill" card:

<div data-pm-skill="bug-diagnosis"></div>
<script src="https://mohitagw15856.github.io/pm-claude-skills/embed.js" async></script>

💬 Discussion

Bug Diagnosis is one of 750 open-source professional AI agent skills — all SkillSpec L3. Try them all in the browser · ⭐ Star on GitHub · Browse the full catalog