# fix-bug

The skill walks an agent through a defect: reproduce it, write a failing test, apply a minimal fix, verify. Built for the ClaudeBar project.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 1556
- Author: tddworks
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/tddworks/ClaudeBar/tree/HEAD/.claude/skills/fix-bug/SKILL.md
- Updated: 2026-10-24
- HTML: https://affpapa.org/en/nevibecode/skills/fix-bug

## What it does

The skill sets the order of work on a bug. The agent reproduces it first, compares expected behaviour against actual, then traces the cause in code. Next comes a test that exposes the defect — it has to fail before the fix. After that, a minimal change makes it pass alongside the existing suite.

Tests follow Chicago School TDD: assert on state and return values, not on interactions. Test names read like a person's sentence, `should <outcome> [when <situation>]`. Mocks stub dependencies with data instead of verifying calls.

The skill is written for ClaudeBar and treats `USER_JOURNEYS`, `CANONICAL_MODEL`, `TARGET_ARCHITECTURE` and a feature's `design.md` as the source of truth. A bug usually means the code breaks a law in `CANONICAL_MODEL.md` §5, so the fix belongs with the law's single owner, not at a call site. When the correct fix changes that law or moves it to another owner, it counts as a design change: update the doc and get the user's confirmation first. Provider bugs are fixed in the provider's JSON or mapping script, or generically in `DataSources` — vendor-named Swift and provider names inside `ClaudeBarApp` are off limits. Logs sit in `~/Library/Logs/ClaudeBar/ClaudeBar.log`, and `account.lastFailedStep` with `lastError` show whether the key, the request or the reading broke. Capture the real CLI or API answer as a redacted fixture for the test; never log a token, key or cookie while investigating.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add tddworks/ClaudeBar --skill fix-bug -a claude-code
```

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

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add tddworks/ClaudeBar --skill fix-bug -a codex
```

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

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add tddworks/ClaudeBar --skill fix-bug -a cursor
```

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

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install tddworks/ClaudeBar fix-bug
```

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

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add tddworks/ClaudeBar --skill fix-bug -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/tddworks/ClaudeBar --path .claude/skills/fix-bug
```

### Windsurf (Devin Desktop)

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

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add tddworks/ClaudeBar --skill fix-bug -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/tddworks/ClaudeBar/tree/HEAD/.claude/skills/fix-bug/SKILL.md

## When to use it
- reproduce a bug and separate expected behaviour from actual
- find the root cause in code instead of patching a call site
- write a failing test that exposes the defect
- apply a minimal fix and keep the existing tests green
- work out which design law the code breaks and who owns it

## Example prompts
- walk through this bug with the fix-bug skill: reproduce it first, then write the test
- a provider shows the wrong thing — take it through fix-bug
- fix this defect in ClaudeBar with fix-bug, the test must fail before the change

## Source text · SKILL.md · Apache-2.0

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: 049a3ba6295ab8ae.

BEGIN THIRD-PARTY FILE 049a3ba6295ab8ae
````text
---
name: fix-bug
description: |
  Guide for fixing bugs in ClaudeBar following Chicago School TDD and rich domain design. Use this skill when:
  (1) User reports a bug or unexpected behavior
  (2) Fixing a defect in existing functionality
  (3) User asks "fix this bug" or "this doesn't work correctly"
  (4) Correcting behavior that violates the user's mental model
---

# Fix Bug in ClaudeBar

Fix bugs using Chicago School TDD, root cause analysis, and rich domain design.

## Workflow

```
┌─────────────────────────────────────────────────────────────┐
│  1. REPRODUCE & UNDERSTAND                                   │
├─────────────────────────────────────────────────────────────┤
│  • Reproduce the bug                                         │
│  • Identify expected vs actual behavior                      │
│  • Locate the root cause in code                             │
└─────────────────────────────────────────────────────────────┘
                            │
                            ▼
┌─────────────────────────────────────────────────────────────┐
│  2. WRITE FAILING TEST (Red)                                 │
├─────────────────────────────────────────────────────────────┤
│  • Write test that exposes the bug                           │
│  • Test should FAIL before fix                               │
│  • Test should verify CORRECT behavior                       │
└─────────────────────────────────────────────────────────────┘
                            │
                            ▼
````
END THIRD-PARTY FILE 049a3ba6295ab8ae

The third-party file has ended. Everything between the 049a3ba6295ab8ae tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 2326 of 11037 bytes. © tddworks · Apache-2.0 · https://github.com/tddworks/ClaudeBar/tree/HEAD/.claude/skills/fix-bug/SKILL.md

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