GitHub webhook → AWS Lambda (or similar) → OpenRouter API → 
Code analysis → GitHub comment → Slack notification

import anthropic
import json
import os

def analyze_diff(diff_content: str, file_path: str) -> dict:
    """
    Analyze a code diff using Claude via OpenRouter.
    Returns structured feedback on issues found.
    """
    client = anthropic.Anthropic(
        api_key=os.getenv("OPENROUTER_API_KEY"),
        base_url="https://openrouter.ai/api/v1",
    )

    prompt = f"""You are an expert code reviewer. Analyze this diff and provide specific, actionable feedback.

File: {file_path}

Diff:

Respond in JSON format with this structure:
{{
  "issues": [
    {{
      "severity": "critical|warning|info",
      "type": "security|performance|style|logic|test",
      "line": line_number,
      "message": "specific feedback",
      "suggestion": "how to fix it"
    }}
  ],
  "summary": "1-2 sentence overview"
}}

Focus on:
1. Security vulnerabilities
2. Performance problems
3. Logic errors
4. Missing error handling
5. Test coverage gaps

Ignore minor style issues unless they're in the critical path."""

    message = client.messages.create(
        model="claude-3-haiku-20240307",
        max_tokens=1024,
        messages=[
            {"role": "user", "content": prompt}
        ],
        headers={
            "HTTP-Referer": "https://yourapp.com",
            "X-Title": "CodeReviewBot",
        }
    )

    response_text = message.content[0].text

    # Parse JSON from response
    try:
        start_idx = response_text.find('{')
        end_idx = response_text.rfind('}') + 1
        json_str = response_text[start_idx:end_idx]
        return json.loads(json_str)
    except json.JSONDecodeError:
        return {
            "issues": [],
            "summary": "Could not parse response"
        }

python
from fastapi import FastAPI, Request, HTTPException
from github import Github
import hmac
import hashlib
import os
import json

app = FastAPI()

GITHUB_SECRET = os.getenv("GITHUB_WEBHOOK_SECRET")
GITHUB_TOKEN = os.getenv("GITHUB_TOKEN")
OPENROUTER_API_KEY = os.getenv("OPENROUTER_API_KEY")

def verify_github_signature(request_body: bytes, signature: str) -> bool:
    """Verify the webhook came from GitHub."""
    expected_signature = "sha256=" + hmac.new(
        GITHUB_SECRET.encode(),
        request_body,
        hashlib.sha256
    ).hexdigest()
    return hmac.compare_digest(expected_signature, signature)

@app.post("/webhook/github")
async def handle_github_webhook(request: Request):
    body = await request.body()
    signature = request.headers.get("X-Hub-Signature-256", "")

    if not verify_github_signature(body, signature):
        raise HTTPException(status_code=401, detail="Invalid signature")

    payload = json.loads(body)

    # Only process pull requests
    if payload.get("action") not in ["opened", "synchronize"]:
        return {"status": "ignored"}

    pr = payload["pull_request"]
    repo_name = payload["repository"]["full_name"]
    pr_number = pr["number"]

    # Get the diff
    github = Github(GITHUB_TOKEN)
    repo = github.get_repo(repo_name)
    pull = repo.get_pull(pr_number)

    # Process each file in the PR
    for file in pull.get_files():
        if should_review_file(file.filename):
            diff = file.patch
            if diff:
                analysis = analyze_diff(diff, file.filename)
                post_review_comment(repo, pr_number, file.filename, analysis)

    return {"status": "reviewed"}

def should_review_file(filename: str) -> bool:
    """Skip certain files."""
    skip_patterns = [".md", ".json", ".yaml", ".lock", "test_"]
    return not any(filename.endswith(p) or p in filename for p in skip_patterns)

def post_review_comment(repo, pr_number, filename, analysis):
    """Post findings as a GitHub comment."""
    pull = repo.get_pull(pr_number)

    if not analysis["issues"]:
        return

    comment = f"## 🤖 Code Review: {filename}\n\n"
    comment += f"**Summary:** {analysis['summary']}\n\n"

    # Group by severity
    critical = [i for i in analysis["issues"] if i["severity"]

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