Reviewing Pull Requests

Pull Request Review Workflow

This skill guides comprehensive PR reviews using the GitHub CLI and local code analysis.

0. Determine Starting Point

When this skill is invoked:

1. If user is already in a PR worktree (mentions "already in worktree", "skip to step 3", or "skip worktree setup"):

   • Skip directly to step 3 (Gather PR Context)
   • Assume worktree is set up correctly
   • Proceed with the review

2. If user provides a PR reference (URL, org/repo#number, etc.) and is NOT in a worktree:

   • Parse the PR reference (see formats below)
   • Confirm with user before creating worktree
   • Proceed to step 1 (Create worktree)

Supported PR reference formats:

• <github_org>/<github_repo>/pull/<pull_request_number>
• <github_org>/<github_repo>#<pull_request_number>
• Full github.com URL pointing to a specific pull request

Note: For setting up worktrees, you can also use the /pr-review slash command which handles the setup workflow and provides handoff instructions.

1. Creating a Git Worktree for the PR

Determine the repository location:

First, check if the repository exists locally on this machine:

• Look in common source code locations (~/src/, ~/repos/, etc.)
• Use the user's machine-specific path configuration if available
• If the repository doesn't exist locally, ask the user if they want to clone it first or provide the path

Create a new worktree with the PR checked out:

# Navigate to the repository (if not already there)
cd /path/to/<repo>

# Create worktree and check out the PR
# Use format: <repo_name>-pr-<pr_number> for the branch and directory
git worktree add ../<repo_name>-pr-<pr_number> -b <repo_name>-pr-<pr_number>
cd ../<repo_name>-pr-<pr_number>
gh pr checkout <pr_number>

Example for vLLM project PR #12345 where vllm is at /Users/alice/repos/vllm:

cd /Users/alice/repos/vllm
git worktree add ../vllm-pr-12345 -b vllm-pr-12345
cd ../vllm-pr-12345
gh pr checkout 12345

Share .claude configuration across worktrees:

After creating the worktree, set up .claude/ configuration sharing if needed:

cd ../<repo_name>-pr-<pr_number>

# Check if .claude already exists (from git or previous setup)
if [ ! -e .claude ]; then
  # Get main worktree path
  MAIN_WORKTREE=$(git worktree list --porcelain | awk '/^worktree/ {print $2; exit}')

  # If .claude exists in main worktree, create symlink
  if [ -d "$MAIN_WORKTREE/.claude" ]; then
    ln -s "$MAIN_WORKTREE/.claude" .claude
    echo "Created .claude symlink to share configuration"
  fi
fi

Why symlink .claude?

• Ensures project-local configuration (review criteria, skills, commands) is available in the PR worktree
• Maintains consistency across all worktrees for the same repository
• If .claude/ is committed to git, it's already available; if not, the symlink shares it

CRITICAL SAFETY: Never run code from the PR. It may contain untrusted code. Only read and analyze files.

2. Launch Claude Code in the Worktree

After creating the worktree, STOP HERE. Do NOT continue to step 3 in this session.

CRITICAL HANDOFF POINT: You must provide the user with instructions to launch a NEW Claude Code session in the worktree. The review MUST happen in a fresh session in the worktree directory, NOT in the current session.

Why this matters:

• Fresh context focused only on PR changes
• Correct working directory for running tests and examining code
• Isolation from the original repository/marketplace

IMPORTANT: Include ALL relevant skills that were loaded in the current session in the handoff prompt. This ensures the new Claude Code session has the full context needed for the review.

Determining Relevant Skills

Before providing handoff instructions, identify which skills were loaded for this review:

1. pr-review skill: Always relevant (this skill)
2. Repository-specific skills: Any skills matching the repository being reviewed (e.g., llama-stack, vllm)
3. Domain-specific skills: Any skills relevant to the PR content (e.g., auth-security for authentication/authorization code)

Example: For a llama-stack PR, both pr-review and llama-stack skills would be relevant.

Handoff Instruction Template

IMPORTANT: Only provide the plain text prompt below. Do NOT invent or reference non-existent slash commands (like /continue-pr-review). The only real slash command is /bbrowning-claude:pr-review which was already used to set up the worktree.

I've created a git worktree for PR #<pr_number> (<github_org>/<github_repo>) at: <worktree_path>

To continue the review in an isolated environment:

1. Open a new terminal
2. Navigate to the worktree: cd <worktree_path>
3. Launch Claude Code: claude
4. In the new Claude Code session, provide this prompt:

   > Review PR #<pr_number> for <github_org>/<github_repo>. I'm already in a git worktree with the PR checked out. Use [list ALL relevant skills: pr-review, <repo-specific>, <domain-specific>] and skip directly to step 3 (Gather PR Context) since the worktree is already set up.

This ensures we're reviewing the correct code in isolation with all necessary context.

Why this matters:

• Repository-specific skills contain critical domain knowledge (e.g., llama-stack's recordings/ handling, distributed systems concerns)
• Domain-specific skills provide specialized security or technical guidance
• Without all skills, the review loses important context and may miss critical issues

⚠️ STOP: The steps below (3-9) are ONLY performed in the NEW Claude Code session within the worktree.

If you just created a worktree in step 1-2, DO NOT proceed to step 3. Provide handoff instructions and wait for the user to start a new session.

If you're in a fresh session and the user says "already in worktree" or "skip to step 3", then proceed with step 3.

IMPORTANT: Remember to clean up the worktree after completing the review (see section 9 below).

3. Gather PR Context

Fetch PR details:

gh pr view <pr_number> --json title,body,commits,comments,reviews,files

Extract and note:

• PR title and description
• Number of commits and commit messages
• Files changed
• Existing comments and reviews
• Any unaddressed review comments

Identify unaddressed comments: Look for review comments that:

• Have no replies from the PR author
• Requested changes that weren't made
• Raised concerns not acknowledged
• Are marked as unresolved

Flag these prominently in your review.

4. Analyze Code Changes

Get the diff:

gh pr diff <pr_number> > pr_changes.diff

For large PRs (>500 lines changed), break the review into logical sections (e.g., by file, by functionality).

Reference the local pr_changes.diff as you need to find changes in the PR over repeated calls to gh pr diff. And remember that you are already in a directory that has the PR cloned and checked out, so you can also look at local files.

Review each changed file systematically:

Use Read, Grep, and Glob tools to examine:

• Changed files and surrounding context
• Related files that might be affected
• Test files for the changed code
• Documentation for updated features

Apply review checklist:

For comprehensive criteria, see reference/review-checklist.md. Key areas:

1. Code Quality

   • Readability and maintainability
   • Follows project conventions
   • Appropriate abstraction levels
   • Error handling

2. Correctness

   • Logic is sound
   • Edge cases handled
   • No obvious bugs
   • Changes align with PR description

3. Testing

   • Tests included for new functionality
   • Tests cover edge cases
   • Existing tests still pass
   • Test quality is adequate

4. Security

   • No security vulnerabilities
   • Input validation present
   • No exposed secrets or credentials
   • Safe handling of user data
   • CRITICAL: Check for pull_request_target + checkout of untrusted code pattern in workflows
   • CI/CD workflows don't expose secrets or OIDC tokens to untrusted code
   • Authentication/Authorization: For PRs involving JWT tokens, MCP servers, or other authentication/authorization code, invoke the auth-security skill for comprehensive security guidance on JWT validation, token exchange, OAuth 2.1 compliance, and MCP authorization patterns

5. Performance

   • No obvious performance issues
   • Efficient algorithms
   • No unnecessary operations
   • Database queries optimized

6. Backward Compatibility

   • Public API changes are compatible
   • Database migrations are safe
   • Configuration changes documented
   • Deprecation handled properly

7. Documentation

   • Code comments where needed
   • API docs updated
   • README updated if needed
   • Breaking changes documented

5. Cross-Cutting Concerns

Check alignment with PR description:

• All described changes are present
• No undescribed significant changes
• Commit messages match changes

Verify comments match code:

• Inline comments are accurate
• No outdated comments from refactoring
• Documentation reflects actual behavior

Assess scope creep:

• Changes are focused on stated goal
• No unrelated refactoring
• Separate concerns properly

6. Categorize Findings

Use the severity guide in reference/severity-guide.md to categorize each finding:

• Critical: Must fix before merge (security, data loss, breaking changes)
• High: Should fix before merge (bugs, significant issues)
• Medium: Should address but not blocking (code quality, minor issues)
• Low: Optional improvements (style, suggestions)

Be specific about:

• What the issue is
• Why it matters
• How to fix it (or suggest approaches)
• File and line references

7. Generate Review Report

Write findings to ./pr_review_results.md using the template in templates/review-report.md.

Report structure:

1. Executive summary
2. Unaddressed comments from others
3. Findings by severity
4. Positive observations
5. Final recommendation (approve/request changes/needs discussion)

Key principles:

• Be constructive and specific
• Include code references (file:line)
• Distinguish blockers from suggestions
• Highlight what's done well
• Provide actionable guidance

8. Present to User

After writing ./pr_review_results.md, present:

1. Summary of key findings
2. Number of issues by severity
3. Critical blockers if any
4. Any unaddressed comments from others
5. Overall recommendation

Ask if the user wants:

• Details on any specific finding
• To focus on particular aspects
• To leave review comments on GitHub

9. Clean Up the Worktree

After completing the PR review, return to the original terminal session where you created the worktree and clean up:

Automated Cleanup (Recommended)

Clean up the worktree and branch:

# Return to the main repository (if not already there)
cd /path/to/<repo>

# Remove the worktree (--force handles modified/untracked files)
git worktree remove --force <repo_name>-pr-<pr_number>

# Delete the local branch
git branch -D <repo_name>-pr-<pr_number>

Example for vLLM PR #12345:

cd ~/src/vllm
git worktree remove --force vllm-pr-12345
git branch -D vllm-pr-12345

This will:

• Remove the worktree directory (including any modified/untracked files)
• Delete the local branch
• Clean up git metadata

Manual Cleanup

Alternative approach with verification step:

# Navigate to the main repository
cd /path/to/<repo>

# List worktrees to verify the one to remove
git worktree list

# Remove the worktree (--force handles modified/untracked files)
git worktree remove --force <repo_name>-pr-<pr_number>

# Delete the local branch
git branch -D <repo_name>-pr-<pr_number>

Why cleanup matters:

• Prevents orphaned worktrees consuming disk space
• Avoids confusion about which worktree to use
• Keeps the repository clean and organized

Safety note: The worktree removal is safe because:

• PR review results should have been saved to the main worktree or submitted to GitHub
• The worktree was for review only (no development work)
• The PR branch still exists on GitHub

Repository-Specific Skills

IMPORTANT: After gathering PR context and determining which repository is being reviewed, check for repository-specific skills that provide specialized review guidance.

Discovering Repository-Specific Skills

1. Identify the repository from the PR context (e.g., llamastack/llama-stack, vllm-project/vllm)
2. Search for matching skills using common repository identifiers:
   • Repository name (e.g., "llama-stack", "vllm")
   • Organization name (e.g., "llamastack")
   • Project name variations
3. Invoke repository-specific skill if found, using the Skill tool
4. Apply specialized guidance from the skill throughout your review

Example: Reviewing a Llama Stack PR

1. Gather PR context → Determine repository is "llamastack/llama-stack"
2. Check for skills → Find "Reviewing Llama Stack Code" skill
3. Invoke skill → Use Skill tool with "bbrowning-claude:llama-stack"
4. Apply guidance → Use Llama Stack-specific patterns in review

Benefits of Repository-Specific Skills

• Specialized knowledge: Project-specific architecture patterns and conventions
• Critical gotchas: Common mistakes specific to that codebase
• Review focus: What matters most for that particular project
• Efficiency: Pre-encoded knowledge from previous reviews

When No Repository-Specific Skill Exists

If no specialized skill is found:

• Proceed with general code review criteria
• Consider creating a repository-specific skill if you identify recurring patterns
• Document project-specific observations for future reference

Common Pitfalls to Avoid

• Don't guess: If you can't determine something from the code, note it as a question
• Don't run code: Security risk - only read and analyze
• Don't be vague: "This looks wrong" → "This function doesn't handle null inputs (see line 42)"
• Don't forget context: Read surrounding code to understand intent
• Don't ignore tests: Test quality matters as much as code quality

Validation Checklist

Before completing the review, ensure:

• PR context gathered (description, comments, reviews)
• Repository identified and repository-specific skill invoked if available
• All changed files examined
• Unaddressed comments identified
• All review checklist areas covered
• Repository-specific patterns validated (if applicable)
• Findings categorized by severity
• Review report written to ./pr_review_results.md
• Specific file:line references included
• Actionable recommendations provided
• Positive aspects noted
• Final recommendation clear
• User reminded to clean up worktree after review (section 9)

Extending This Skill

This skill is designed to be customized:

1. Add review criteria: Edit reference/review-checklist.md
2. Adjust severity definitions: Modify reference/severity-guide.md
3. Customize report format: Update templates/review-report.md
4. Add repository-specific guidance: Create new repository-specific skills (e.g., llama-stack, vllm) rather than modifying this skill
5. Security guidelines: For authentication and authorization security, use the auth-security skill

Creating Repository-Specific Skills

For repositories you frequently review, create dedicated skills:

1. Use the skill-builder skill for guidance on creating skills
2. Name the skill after the repository (e.g., "Reviewing Llama Stack Code")
3. Include in the description: repository name, common variations, and "PR review" or "code review"
4. Document architecture patterns, testing conventions, and critical gotchas
5. The pr-review skill will automatically discover and invoke it

The goal is a thorough, actionable review that helps maintain code quality while being respectful and constructive.

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