# systematic-debugging

Enforces a structured debugging workflow on your AI assistant instead of random edits. It helps isolate elusive bugs and verify root causes with evidence.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 545 installs · ★ 866
- Author: spencerpauly
- License: CC0-1.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/spencerpauly/awesome-cursor-skills/tree/HEAD/resources/systematic-debugging/SKILL.md
- Updated: 2026-08-02
- HTML: https://affpapa.org/en/nevibecode/skills/spencerpauly-systematic-debugging

## What it does

This skill guides the agent through structured bug hunting: reproduction, isolation, hypothesis testing, and targeted verification. The assistant must confirm trigger steps and environment parameters before touching any code. For isolation, it relies on binary search in the codebase and running `git bisect` when a commit broke working behavior.

Random code edits are forbidden. The assistant forms a testable hypothesis and verifies it with a focused log or breakpoint before patching. The methodology includes a clear safeguard: if no progress occurs within 15 minutes, the agent must step back and re-isolate the failure.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add spencerpauly/awesome-cursor-skills --skill systematic-debugging -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/systematic-debugging/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/systematic-debugging/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add spencerpauly/awesome-cursor-skills --skill systematic-debugging -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/systematic-debugging/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add spencerpauly/awesome-cursor-skills --skill systematic-debugging -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/systematic-debugging/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install spencerpauly/awesome-cursor-skills systematic-debugging
```

2. **Manually: put the files in place**
- File: `.github/skills/systematic-debugging/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add spencerpauly/awesome-cursor-skills --skill systematic-debugging -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/spencerpauly/awesome-cursor-skills --path resources/systematic-debugging
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/systematic-debugging/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add spencerpauly/awesome-cursor-skills --skill systematic-debugging -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/spencerpauly/awesome-cursor-skills/tree/HEAD/resources/systematic-debugging/SKILL.md

## When to use it
- isolate code regressions using `git bisect`
- reproduce environment mismatches between local and production setups
- diagnose intermittent issues like race conditions and stale closures
- verify testable hypotheses with logging before modifying source files

## Example prompts
- Use systematic-debugging to investigate why this async function hangs.
- Run git bisect with systematic-debugging to locate the commit that broke login.
- Apply systematic-debugging to isolate an unhandled undefined error in this component.

## Source text · SKILL.md · CC0-1.0

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````text
---
name: systematic-debugging
description: Structured debugging methodology — reproduce, isolate, hypothesize, verify. Covers git bisect, binary search, logging, and minimal reproduction.
user-invocable: true
---

# Systematic Debugging

Debug methodically instead of randomly changing code.

## The Process

### 1. Reproduce

Before anything else, reproduce the bug reliably:
- Get the exact steps to trigger the issue
- Note the expected vs actual behavior
- Confirm it happens consistently (not intermittent)
- Record the environment (OS, Node version, browser, etc.)

If you can't reproduce it, you can't fix it. Ask for more details.

### 2. Isolate

Narrow down where the bug lives:

**Binary search the codebase:**
- Comment out half the system → does the bug persist?
- If yes, the bug is in the remaining half → repeat
- If no, the bug is in the commented-out half → repeat

**Git bisect:**
```bash
git bisect start
git bisect bad          # current commit is broken
git bisect good <sha>   # this commit was working
# Git checks out the midpoint — test it
git bisect good         # or git bisect bad
# Repeat until it finds the first bad commit
git bisect reset        # when done
```

**Isolate by layer:**
- Is it frontend or backend? (Check network tab)
- Is it the database? (Query directly)
- Is it the API? (curl the endpoint)
- Is it the component? (Render it in isolation)

### 3. Hypothesize

Form a specific, testable hypothesis:
- "The bug is caused by X because Y"
- Not "something is wrong with the data"
- Good: "The `userId` is null because the auth middleware doesn't run on this route"

### 4. Test the Hypothesis

Write the smallest possible test that proves/disproves your hypothesis:
- Add a `console.log` or breakpoint at the suspected location
- Check the value of the suspected variable
- If your hypothesis is wrong, go back to step 3 with new information
- If it's right, you've found the bug

### 5. Fix and Verify

- Apply the minimal fix
- Verify the original reproduction steps no longer trigger the bug
- Check for regressions — did the fix break anything else?
- Write a test that would have caught this bug

## Debugging Tools

| Scenario | Tool |
|----------|------|
| "It worked before" | `git bisect` |
| "I don't know where this runs" | Add logging at entry/exit of suspect functions |
| "The data looks wrong" | Inspect at each transformation step |
| "It only fails in production" | Compare env vars, check logs, try to reproduce with prod data locally |
| "It's intermittent" | Look for race conditions, timing issues, or uninitialized state |
| "The error message is useless" | Search the codebase for where that error is thrown |

## Common Bug Patterns

- **Off-by-one**: Array indices, pagination, date ranges
- **Null/undefined**: Missing optional chaining, uninitialized state
````
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