Building a Code Review Agent with Claude

import anthropic
from github import Github
 
client = anthropic.Anthropic()
gh = Github(os.environ["GITHUB_TOKEN"])
 
def review_pr(repo_name: str, pr_number: int):
    repo = gh.get_repo(repo_name)
    pr = repo.get_pull(pr_number)
 
    findings = []
    for file in pr.get_files():
        if file.changes > 500:
            continue
        result = review_file(file.filename, file.patch)
        findings.extend(result)
 
    if findings:
        pr.create_issue_comment(format_review(findings))

SYSTEM_PROMPT = """
You are a senior software engineer reviewing a pull request.
Focus ONLY on:
1. Bugs: null dereferences, off-by-one errors, race conditions
2. Security: SQL injection, XSS, hardcoded secrets
3. Performance: N+1 queries, unnecessary allocations
4. Architecture: violations of existing patterns
 
Do NOT comment on style, formatting, or naming.
"""