Code Review Skill

Load with: base.md + [codex-review.md for OpenAI Codex] + [gemini-review.md for Google Gemini]

Purpose: Enforce automated code reviews as a mandatory guardrail before every commit and deployment. Choose between Claude, OpenAI Codex, Google Gemini, or multiple engines for comprehensive analysis.

Review Engine Choice

When running /code-review, users can choose their preferred review engine:

┌─────────────────────────────────────────────────────────────────┐
│  CODE REVIEW - Choose Your Engine                               │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│  ○ Claude (default)                                             │
│    Built-in, no extra setup, full conversation context          │
│                                                                 │
│  ○ OpenAI Codex CLI                                             │
│    GPT-5.2-Codex specialized for code review, 88% detection     │
│    Requires: npm install -g @openai/codex                       │
│                                                                 │
│  ○ Google Gemini CLI                                            │
│    Gemini 2.5 Pro with 1M token context, free tier available    │
│    Requires: npm install -g @google/gemini-cli                  │
│                                                                 │
│  ○ Dual Engine (any two)                                        │
│    Run two engines, compare findings, catch more issues         │
│                                                                 │
│  ○ All Three (maximum coverage)                                 │
│    Run Claude + Codex + Gemini for critical/security code       │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

Engine Comparison

Set Default Engine

# ~/.claude/settings.toml or project CLAUDE.md
[code-review]
default_engine = "claude"  # Options: claude, codex, gemini, dual, all

Usage Examples

# Use default engine
/code-review

# Explicitly choose engine
/code-review --engine claude
/code-review --engine codex
/code-review --engine gemini

# Dual engine (pick any two)
/code-review --engine claude,codex
/code-review --engine claude,gemini
/code-review --engine codex,gemini

# All three engines
/code-review --engine all

# Quick shortcuts
/code-review              # Uses default
/code-review --codex      # Use Codex
/code-review --gemini     # Use Gemini
/code-review --all        # All three engines

Multi-Engine Output

When using multiple engines, findings are compared and deduplicated:

Dual Engine Example

┌─────────────────────────────────────────────────────────────────┐
│  CODE REVIEW RESULTS - DUAL ENGINE (Claude + Codex)             │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│  ✅ AGREED (Found by both):                                     │
│  🔴 SQL injection in auth.ts:45                                 │
│  🟡 Missing error handling in api.ts:112                        │
│                                                                 │
│  🔷 CLAUDE ONLY:                                                │
│  🟠 Potential race condition in worker.ts:89                    │
│  🟢 Consider extracting helper function                         │
│                                                                 │
│  🔶 CODEX ONLY:                                                 │
│  🟠 Memory leak - unclosed stream in upload.ts:34               │
│  🟡 N+1 query pattern in orders.ts:156                          │
│                                                                 │
├─────────────────────────────────────────────────────────────────┤
│  SUMMARY                                                        │
│  Agreed: 2 | Claude only: 2 | Codex only: 2                     │
│  Critical: 1 | High: 2 | Medium: 2 | Low: 1                     │
│  Status: ❌ BLOCKED - Fix critical/high issues                  │
└─────────────────────────────────────────────────────────────────┘

Triple Engine Example (All Three)

┌─────────────────────────────────────────────────────────────────┐
│  CODE REVIEW RESULTS - TRIPLE ENGINE                            │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│  ✅ UNANIMOUS (All 3 found):                                    │
│  🔴 SQL injection in auth.ts:45                                 │
│                                                                 │
│  ✅ MAJORITY (2 of 3 found):                                    │
│  🟠 Memory leak - unclosed stream in upload.ts:34 (Codex+Gemini)│
│  🟡 Missing error handling in api.ts:112 (Claude+Codex)         │
│                                                                 │
│  🔷 CLAUDE ONLY:                                                │
│  🟠 Potential race condition in worker.ts:89                    │
│                                                                 │
│  🔶 CODEX ONLY:                                                 │
│  🟡 N+1 query pattern in orders.ts:156                          │
│                                                                 │
│  🟢 GEMINI ONLY:                                                │
│  🟡 Consider using batch API for better performance             │
│  🟢 Type could be more specific in types.ts:23                  │
│                                                                 │
├─────────────────────────────────────────────────────────────────┤
│  SUMMARY                                                        │
│  Unanimous: 1 | Majority: 2 | Single: 5                         │
│  Critical: 1 | High: 2 | Medium: 3 | Low: 2                     │
│  Status: ❌ BLOCKED - Fix critical/high issues                  │
└─────────────────────────────────────────────────────────────────┘

When to Use Each Mode

Core Philosophy

┌─────────────────────────────────────────────────────────────────┐
│  CODE REVIEW IS NON-NEGOTIABLE                                  │
│  ─────────────────────────────────────────────────────────────  │
│                                                                 │
│  Every commit must pass code review.                            │
│  Every PR must be reviewed before merge.                        │
│  Every deployment must include review sign-off.                 │
│                                                                 │
│  AI catches what humans miss. Humans catch what AI misses.      │
│  Together: fewer bugs, cleaner code, better security.           │
├─────────────────────────────────────────────────────────────────┤
│  INVOKE: /code-review                                           │
│  PLUGIN: code-review@claude-plugins-official                    │
└─────────────────────────────────────────────────────────────────┘

When to Run Code Review

Mandatory Review Points

Automatic Integration

Run code review automatically before every commit:

┌─────────────────────────────────────────────────────────────────┐
│  COMMIT WORKFLOW                                                │
│  ─────────────────────────────────────────────────────────────  │
│                                                                 │
│  1. Write code                                                  │
│  2. Run tests (TDD - must pass)                                 │
│  3. Run /code-review  ← MANDATORY                               │
│  4. Address critical/high issues                                │
│  5. Commit                                                      │
│  6. Push                                                        │
│                                                                 │
│  Skip step 3? ❌ NO COMMIT ALLOWED                              │
└─────────────────────────────────────────────────────────────────┘

Using the Code Review Plugin

Basic Usage

# Review current changes
/code-review

# Review specific files
/code-review src/auth/*.ts

# Review a PR
/code-review --pr 123

# Review with specific focus
/code-review --focus security
/code-review --focus performance
/code-review --focus architecture

Review Categories

The code review plugin analyzes:

Severity Levels

Pre-Commit Hook Integration

Install Pre-Commit Hook

#!/bin/bash
# .git/hooks/pre-commit

echo "🔍 Running code review..."

# Run Claude code review on staged files
STAGED_FILES=$(git diff --cached --name-only --diff-filter=ACM | grep -E '\.(ts|tsx|js|jsx|py|go|rs)$')

if [ -n "$STAGED_FILES" ]; then
    # Invoke code review (requires claude CLI)
    claude --print "/code-review $STAGED_FILES" > /tmp/code-review-result.txt 2>&1

    # Check for critical/high issues
    if grep -q "🔴\|Critical\|🟠\|High" /tmp/code-review-result.txt; then
        echo "❌ Code review found critical/high issues:"
        cat /tmp/code-review-result.txt
        echo ""
        echo "Fix these issues before committing."
        exit 1
    fi

    echo "✅ Code review passed"
fi

exit 0

Make Hook Executable

chmod +x .git/hooks/pre-commit

Codex CLI Setup (For Codex/Both Modes)

If you want to use Codex or Both modes, install the Codex CLI:

# Prerequisites: Node.js 22+
node --version  # Must be 22+

# Install Codex CLI
npm install -g @openai/codex

# Authenticate (choose one):
# Option 1: ChatGPT subscription (Plus, Pro, Team, Enterprise)
codex  # Follow prompts to sign in

# Option 2: API key
export OPENAI_API_KEY=sk-proj-...

Verify Installation

# Check Codex is installed
codex --version

# Test review
codex
> /review

See codex-review.md skill for full Codex documentation.

Gemini CLI Setup (For Gemini/Multi-Engine Modes)

If you want to use Gemini or multi-engine modes, install the Gemini CLI:

# Prerequisites: Node.js 20+
node --version  # Must be 20+

# Install Gemini CLI
npm install -g @google/gemini-cli

# Or via Homebrew (macOS)
brew install gemini-cli

# Install Code Review extension
gemini extensions install https://github.com/gemini-cli-extensions/code-review

Authenticate

# Option 1: Google Account (recommended, 1000 req/day free)
gemini  # Follow browser login prompts

# Option 2: API key (100 req/day free)
export GEMINI_API_KEY="your-key-from-aistudio.google.com"

Verify Installation

# Check Gemini is installed
gemini --version

# List extensions
gemini extensions list

# Test review
gemini
> /code-review

See gemini-review.md skill for full Gemini documentation.

CI/CD Integration

GitHub Actions – Claude Only

# .github/workflows/code-review.yml
name: Code Review

on:
  pull_request:
    types: [opened, synchronize, reopened]

jobs:
  code-review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Get changed files
        id: changed-files
        run: |
          echo "files=$(git diff --name-only origin/${{ github.base_ref }}...HEAD | tr '\n' ' ')" >> $GITHUB_OUTPUT

      - name: Run Claude Code Review
        env:
          ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
        run: |
          npx @anthropic-ai/claude-code --print "/code-review ${{ steps.changed-files.outputs.files }}" > review.md

      - name: Post Review Comment
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const review = fs.readFileSync('review.md', 'utf8');

            github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.issue.number,
              body: `## 🔍 Claude Code Review\n\n${review}`
            });

      - name: Check for Critical Issues
        run: |
          if grep -q "Critical\|🔴" review.md; then
            echo "❌ Critical issues found"
            exit 1
          fi

GitHub Actions – Codex Only

# .github/workflows/codex-review.yml
name: Codex Code Review

on:
  pull_request:

jobs:
  review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Codex Review
        uses: openai/codex-action@main
        with:
          openai_api_key: ${{ secrets.OPENAI_API_KEY }}
          model: gpt-5.2-codex
          safety_strategy: drop-sudo

GitHub Actions – Both Engines

# .github/workflows/dual-review.yml
name: Dual Code Review

on:
  pull_request:

jobs:
  claude-review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Claude Review
        env:
          ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
        run: |
          npx @anthropic-ai/claude-code --print "/code-review" > claude-review.md

      - uses: actions/upload-artifact@v4
        with:
          name: claude-review
          path: claude-review.md

  codex-review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - uses: actions/setup-node@v4
        with:
          node-version: '22'

      - name: Install Codex
        run: npm install -g @openai/codex

      - name: Codex Review
        env:
          OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
        run: |
          codex exec --full-auto --sandbox read-only \
            --output-last-message codex-review.md \
            "Review this code for bugs, security issues, and quality problems"

      - uses: actions/upload-artifact@v4
        with:
          name: codex-review
          path: codex-review.md

  combine-reviews:
    needs: [claude-review, codex-review]
    runs-on: ubuntu-latest
    steps:
      - uses: actions/download-artifact@v4

      - name: Combine Reviews
        run: |
          echo "## 🔍 Dual Code Review Results" > combined-review.md
          echo "" >> combined-review.md
          echo "### Claude Findings" >> combined-review.md
          cat claude-review/claude-review.md >> combined-review.md
          echo "" >> combined-review.md
          echo "### Codex Findings" >> combined-review.md
          cat codex-review/codex-review.md >> combined-review.md

      - name: Post Combined Review
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const review = fs.readFileSync('combined-review.md', 'utf8');
            github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.issue.number,
              body: review
            });

GitHub Actions – Gemini Only

# .github/workflows/gemini-review.yml
name: Gemini Code Review

on:
  pull_request:
    types: [opened, synchronize]

jobs:
  review:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: write

    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Setup Node.js
        uses: actions/setup-node@v4
        with:
          node-version: '20'

      - name: Install Gemini CLI
        run: npm install -g @google/gemini-cli

      - name: Run Review
        env:
          GEMINI_API_KEY: ${{ secrets.GEMINI_API_KEY }}
        run: |
          # Get diff
          git diff origin/${{ github.base_ref }}...HEAD > diff.txt

          # Run Gemini review
          gemini -p "Review this pull request diff for bugs, security issues, and code quality problems. Be specific about file names and line numbers.

          $(cat diff.txt)" > review.md

      - name: Post Review Comment
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const review = fs.readFileSync('review.md', 'utf8');
            github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.issue.number,
              body: `## 🤖 Gemini Code Review\n\n${review}`
            });

      - name: Check for Critical Issues
        run: |
          if grep -qi "critical\|security vulnerability\|injection" review.md; then
            echo "❌ Critical issues found"
            exit 1
          fi

GitHub Actions – All Three Engines

# .github/workflows/triple-review.yml
name: Triple Engine Code Review

on:
  pull_request:

jobs:
  claude-review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - name: Claude Review
        env:
          ANTHROPIC_API_KEY: ${{ secrets.ANTHROPIC_API_KEY }}
        run: |
          npx @anthropic-ai/claude-code --print "/code-review" > claude-review.md

      - uses: actions/upload-artifact@v4
        with:
          name: claude-review
          path: claude-review.md

  codex-review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - uses: actions/setup-node@v4
        with:
          node-version: '22'

      - name: Install Codex
        run: npm install -g @openai/codex

      - name: Codex Review
        env:
          OPENAI_API_KEY: ${{ secrets.OPENAI_API_KEY }}
        run: |
          codex exec --full-auto --sandbox read-only \
            --output-last-message codex-review.md \
            "Review this code for bugs, security issues, and quality problems"

      - uses: actions/upload-artifact@v4
        with:
          name: codex-review
          path: codex-review.md

  gemini-review:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
        with:
          fetch-depth: 0

      - uses: actions/setup-node@v4
        with:
          node-version: '20'

      - name: Install Gemini CLI
        run: npm install -g @google/gemini-cli

      - name: Gemini Review
        env:
          GEMINI_API_KEY: ${{ secrets.GEMINI_API_KEY }}
        run: |
          git diff origin/${{ github.base_ref }}...HEAD > diff.txt
          gemini -p "Review this code diff for bugs, security, and quality issues:
          $(cat diff.txt)" > gemini-review.md

      - uses: actions/upload-artifact@v4
        with:
          name: gemini-review
          path: gemini-review.md

  combine-reviews:
    needs: [claude-review, codex-review, gemini-review]
    runs-on: ubuntu-latest
    steps:
      - uses: actions/download-artifact@v4

      - name: Combine Reviews
        run: |
          echo "## 🔍 Triple Engine Code Review Results" > combined-review.md
          echo "" >> combined-review.md
          echo "### 🟣 Claude Findings" >> combined-review.md
          cat claude-review/claude-review.md >> combined-review.md
          echo "" >> combined-review.md
          echo "---" >> combined-review.md
          echo "### 🟢 Codex Findings" >> combined-review.md
          cat codex-review/codex-review.md >> combined-review.md
          echo "" >> combined-review.md
          echo "---" >> combined-review.md
          echo "### 🔵 Gemini Findings" >> combined-review.md
          cat gemini-review/gemini-review.md >> combined-review.md

      - name: Post Combined Review
        uses: actions/github-script@v7
        with:
          script: |
            const fs = require('fs');
            const review = fs.readFileSync('combined-review.md', 'utf8');
            github.rest.issues.createComment({
              owner: context.repo.owner,
              repo: context.repo.repo,
              issue_number: context.issue.number,
              body: review
            });

      - name: Check Critical Issues
        run: |
          # Fail if any engine found critical issues
          if grep -qi "critical\|🔴" combined-review.md; then
            echo "❌ Critical issues found by at least one engine"
            exit 1
          fi

Review Checklist

Before Every Commit

• Run /code-review on staged changes
• No critical (🔴) issues
• No high (🟠) issues
• Security concerns addressed
• Performance issues considered

Before Every PR

• Full code review of all changes
• All critical/high issues resolved
• Tests added for new functionality
• Documentation updated if needed

Before Every Deployment

• Final review of deployment diff
• Security scan passed
• No new vulnerabilities introduced
• Rollback plan documented

Common Review Findings

Security Issues (Always Fix)

Performance Issues (Should Fix)

Code Quality (Nice to Fix)

Integration with TDD Workflow

┌─────────────────────────────────────────────────────────────────┐
│  TDD + CODE REVIEW WORKFLOW                                     │
│  ─────────────────────────────────────────────────────────────  │
│                                                                 │
│  1. RED: Write failing tests                                    │
│  2. GREEN: Write code to pass tests                             │
│  3. REFACTOR: Clean up code                                     │
│  4. REVIEW: Run /code-review  ← NEW STEP                        │
│  5. FIX: Address critical/high issues                           │
│  6. VALIDATE: Lint + TypeCheck + Coverage                       │
│  7. COMMIT: Only after review passes                            │
│                                                                 │
│  Review catches what tests miss:                                │
│  - Security vulnerabilities                                     │
│  - Performance issues                                           │
│  - Architecture problems                                        │
│  - Code maintainability                                         │
└─────────────────────────────────────────────────────────────────┘

Review Response Template

When code review finds issues, respond with:

## Code Review Results

### 🔴 Critical Issues (Must Fix)
1. **SQL Injection in userController.ts:45**
   - Issue: User input directly interpolated into query
   - Fix: Use parameterized query
   - Code: `db.query('SELECT * FROM users WHERE id = $1', [userId])`

### 🟠 High Issues (Should Fix)
1. **Missing authentication on /api/admin endpoints**
   - Issue: Admin routes accessible without auth
   - Fix: Add auth middleware

### 🟡 Medium Issues (Fix Soon)
1. **N+1 query in getOrders function**
   - Consider eager loading or batch query

### 🟢 Low Issues (Nice to Have)
1. **Consider extracting validation logic to separate file**

### ✅ Strengths
- Good test coverage
- Clear function names
- Proper error handling

### 📊 Summary
- Critical: 1 | High: 1 | Medium: 1 | Low: 1
- **Status: ❌ BLOCKED** - Fix critical/high issues before commit

Claude Instructions

When to Invoke Code Review

Claude should automatically suggest or run code review:

1. After completing a feature → “Let me run a code review before we commit”
2. Before creating a PR → “Running code review on all changes”
3. When user says “commit” → “First, let me review the changes”
4. After fixing bugs → “Reviewing the fix for any issues”

Review Focus Areas

Prioritize review based on change type:

Quick Reference

Commands

# Basic review
/code-review

# Review specific files
/code-review src/auth.ts src/users.ts

# Review with focus
/code-review --focus security

# Review PR
/code-review --pr 123

Severity Actions

🔴 Critical → STOP. Fix now. No commit.
🟠 High     → STOP. Fix now. No commit.
🟡 Medium   → Note it. Fix soon. Can commit.
🟢 Low      → Optional. Nice to have.
ℹ️ Info     → FYI only.

Workflow

Code → Test → Review → Fix → Commit → Push → PR → Review → Merge → Deploy
              ↑                              ↑                    ↑
           /code-review                /code-review          /code-review