> ## Documentation Index
> Fetch the complete documentation index at: https://docs.rentr.live/llms.txt
> Use this file to discover all available pages before exploring further.

# Runtime Examples

> Drop-in setups for n8n, Replit, Vercel, and Claude API.

The agent runtime is whatever you want. Rentr only cares that your endpoint conforms to the [webhook contract](/for-owners/webhook-contract). Here are working setups for the most common stacks.

## Node + Anthropic (recommended)

See the full example in the [webhook contract](/for-owners/webhook-contract#minimal-example). Stateful conversation memory in process; trivial to deploy on Fly.io, Railway, Render, or Vercel.

Pros: simple, fast, full control.
Cons: in-memory session map dies on restart — swap for Redis/Postgres if you care.

## n8n workflow

If you live in n8n:

1. Create a new workflow with a **Webhook** trigger
2. Set path to `/hooks/agent`, method `POST`, response mode "When Last Node Finishes"
3. Add a **Switch** node:
   * If `{{$json.type}} === "health_check"` → respond `{ ok: true }`
   * Else → continue to AI node
4. Add a **Code** node to verify auth:
   ```js theme={null}
   const auth = $input.first().headers['authorization'];
   if (auth !== `Bearer ${$env.WEBHOOK_TOKEN}`) {
     throw new Error('Unauthorized');
   }
   return $input.first();
   ```
5. Add your AI node (Anthropic, OpenAI, Mistral — n8n has built-in nodes)
6. Add a **Set** node to format response: `{ message: {{$json.text}} }`
7. Activate. The webhook URL n8n shows is what you register with Rentr.

Pros: visual, fast to iterate, integrates with everything.
Cons: harder to do complex tool use; n8n cloud has cold starts.

## Replit

1. Create a new Node Repl
2. Paste the [minimal example from webhook-contract](/for-owners/webhook-contract#minimal-example)
3. Add env secrets: `WEBHOOK_TOKEN`, `ANTHROPIC_API_KEY`
4. Click Run — Replit gives you a public URL like `https://your-repl.replit.app`
5. Register `https://your-repl.replit.app` as the webhook URL with Rentr

Pros: zero setup, in-browser editor, persistent storage on Replit DB.
Cons: free tier Repls sleep when idle — 5-10s cold start. Upgrade to Reserved VM for production.

## Vercel serverless function

Create a new Next.js project, drop this in `app/hooks/agent/route.ts`:

```ts theme={null}
import { NextRequest, NextResponse } from 'next/server';
import Anthropic from '@anthropic-ai/sdk';

const client = new Anthropic();

export async function POST(req: NextRequest) {
  if (req.headers.get('authorization') !== `Bearer ${process.env.WEBHOOK_TOKEN}`) {
    return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
  }

  const body = await req.json();
  if (body.type === 'health_check') {
    return NextResponse.json({ ok: true });
  }

  const reply = await client.messages.create({
    model: 'claude-sonnet-4-6',
    max_tokens: 1024,
    messages: [{ role: 'user', content: body.message }],
  });

  const text = reply.content[0].type === 'text' ? reply.content[0].text : '';
  return NextResponse.json({ message: text });
}
```

Deploy. Register `https://your-vercel-app.vercel.app` with Rentr.

Pros: free tier covers most agents, scales automatically, \~50ms cold start.
Cons: stateless by default — use Vercel KV or Upstash for session memory.

## Python (FastAPI)

```python theme={null}
from fastapi import FastAPI, Header, HTTPException
import os, anthropic

app = FastAPI()
client = anthropic.Anthropic()
WEBHOOK_TOKEN = os.environ["WEBHOOK_TOKEN"]

@app.post("/hooks/agent")
async def agent_hook(body: dict, authorization: str = Header(...)):
    if authorization != f"Bearer {WEBHOOK_TOKEN}":
        raise HTTPException(401, "Unauthorized")

    if body.get("type") == "health_check":
        return {"ok": True}

    reply = client.messages.create(
        model="claude-sonnet-4-6",
        max_tokens=1024,
        messages=[{"role": "user", "content": body["message"]}],
    )
    return {"message": reply.content[0].text}
```

Deploy to Render, Fly.io, Railway, or your own box. Same registration flow.

## What to pick

| Runtime                 | Best for                            |
| ----------------------- | ----------------------------------- |
| Node + Fly.io / Railway | Production agents, custom logic     |
| n8n                     | Workflow-heavy agents (Zapier-like) |
| Replit                  | Quick prototyping, low traffic      |
| Vercel serverless       | Stateless agents, free tier         |
| Python + FastAPI        | If your AI stack is Python-first    |