# parallel-debugging

This skill investigates complex bugs by testing competing hypotheses in parallel. Use it when an issue has several plausible causes or crosses multiple components.

- skill · `type=skill` · Claude Code, Codex, Cursor · 10000 installs · ★ 41729
- Author: Seth Hobson
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/wshobson/agents/tree/HEAD/plugins/agent-teams/skills/parallel-debugging/SKILL.md
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/skills/parallel-debugging

## What it does

The skill groups possible causes into six areas: logic, data, state, integration, resources, and environment. It calls for evidence tied to file and line references, then compares hypotheses by confidence and causal strength. Findings are classified as confirmed, falsified, plausible, or inconclusive.

Once a cause is selected, the skill gives checks for validating the fix, including the original reproduction case, related edge cases, and tests. It fits bugs that resisted initial debugging or span several components. For a straightforward issue with an obvious cause, this process is unnecessary.

## Install

### Claude Code (native platform)

1. **Plugin marketplace**
In the agent chat (not a shell):
```text
/plugin marketplace add wshobson/agents
```
In the agent chat (not a shell):
```text
/plugin install agent-teams@claude-code-workflows
```
This installs the whole agent-teams plugin with all its skills

2. **Skills CLI (Vercel)**
```bash
npx skills add wshobson/agents --skill parallel-debugging -a claude-code
```

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

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add wshobson/agents --skill parallel-debugging -a codex
```

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

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add wshobson/agents --skill parallel-debugging -a cursor
```

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

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install wshobson/agents parallel-debugging
```

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

### Gemini CLI

**Platform CLI**
```bash
gemini skills install https://github.com/wshobson/agents --path plugins/agent-teams/skills/parallel-debugging
```

### Windsurf (Devin Desktop)

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

### 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/wshobson/agents/tree/HEAD/plugins/agent-teams/skills/parallel-debugging/SKILL.md

## When to use it
- investigate a bug with several plausible causes
- trace an issue across multiple modules
- weigh evidence for and against each hypothesis
- check a fix against the original reproduction case

## Example prompts
- Investigate this bug in parallel. List competing causes and gather evidence for each.
- Find the root cause of this failure across these modules, citing the relevant files and lines.
- Check whether this fix addresses the original bug and covers related edge cases.

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 08a133d1215682a6.

BEGIN THIRD-PARTY FILE 08a133d1215682a6
````text
---
name: parallel-debugging
description: Debug complex issues using competing hypotheses with parallel investigation, evidence collection, and root cause arbitration. Use this skill when debugging bugs with multiple potential causes, performing root cause analysis, or organizing parallel investigation workflows.
version: 1.0.2
---

# Parallel Debugging

Framework for debugging complex issues using the Analysis of Competing Hypotheses (ACH) methodology with parallel agent investigation.

## When to Use This Skill

- Bug has multiple plausible root causes
- Initial debugging attempts haven't identified the issue
- Issue spans multiple modules or components
- Need systematic root cause analysis with evidence
- Want to avoid confirmation bias in debugging

## Hypothesis Generation Framework

Generate hypotheses across 6 failure mode categories:

### 1. Logic Error

- Incorrect conditional logic (wrong operator, missing case)
- Off-by-one errors in loops or array access
- Missing edge case handling
- Incorrect algorithm implementation

### 2. Data Issue

- Invalid or unexpected input data
- Type mismatch or coercion error
- Null/undefined/None where value expected
- Encoding or serialization problem
- Data truncation or overflow

### 3. State Problem

- Race condition between concurrent operations
- Stale cache returning outdated data
- Incorrect initialization or default values
- Unintended mutation of shared state
- State machine transition error

### 4. Integration Failure

- API contract violation (request/response mismatch)
- Version incompatibility between components
- Configuration mismatch between environments
- Missing or incorrect environment variables
- Network timeout or connection failure

### 5. Resource Issue

- Memory leak causing gradual degradation
- Connection pool exhaustion
- File descriptor or handle leak
- Disk space or quota exceeded
- CPU saturation from inefficient processing

### 6. Environment

- Missing runtime dependency
- Wrong library or framework version
- Platform-specific behavior difference
- Permission or access control issue
- Timezone or locale-related behavior

## Evidence Collection Standards

### What Constitutes Evidence

| Evidence Type     | Strength | Example                                                         |
| ----------------- | -------- | --------------------------------------------------------------- |
| **Direct**        | Strong   | Code at `file.ts:42` shows `if (x > 0)` should be `if (x >= 0)` |
| **Correlational** | Medium   | Error rate increased after commit `abc123`                      |
| **Testimonial**   | Weak     | "It works on my machine"                                        |
| **Absence**       | Variable | No null check found in the code path                            |

### Citation Format

Always cite evidence with file:line references:

```
**Evidence**: The validation function at `src/validators/user.ts:87`
does not check for empty strings, only null/undefined. This allows
empty email addresses to pass validation.
```

### Confidence Levels
````
END THIRD-PARTY FILE 08a133d1215682a6

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---
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