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

# Node.js middleware

> TrustGuard on the request path in Express (same pattern in Next.js).

Middleware for **input**. Call `guard` again with `direction: "output"` after the model
([Node.js SDK](/trustguard/integrations/node-sdk)).

## Coverage

| Surface    | Monitor | Block | Redact |
| ---------- | :-----: | :---: | :----: |
| LLM input  |    ✅    |   ⚠️  |   ⚠️   |
| LLM output |    ✅    |   ⚠️  |   ⚠️   |
| Tool-level |    ⚠️   |   ⚠️  |   ⚠️   |

**Ask** — `status` is advisory: nothing prompts anyone unless your code does.
A middleware has no user to prompt on the HTTP path either.

**Use it when** you want every new AI route covered by configuration rather than
by each developer's discipline. **Not as your only defence when** traffic reaches
a model without an HTTP request — jobs, queues and internal calls bypass it.

**Limits.** In Next.js the middleware runs on the Edge runtime by default;
confirm your deployment target supports the SDK or move the check into the route
handler. Output coverage needs a second evaluation on the response.

Full comparison: [Coverage](/trustguard/integrations/coverage).

```ts theme={null}
import express from "express";
import { TrustGuard } from "@neuraltrust/trustguard-sdk";

const app = express();
app.use(express.json());

const client = new TrustGuard({
  baseUrl: "<your-trustguard-url>",
  apiKey: "<collector-api-key>",
});

app.use(async (req, res, next) => {
  if (req.method !== "POST") return next();
  const response = await client.guard({
    payload: { input: JSON.stringify(req.body) },
    direction: "input",
    consumerId: req.get("x-user-id") ?? "",
    sessionId: req.cookies?.session_id ?? "",
  });
  if (response.isBlocked) {
    return res.status(403).json({ detail: "Blocked by TrustGuard" });
  }
  if (response.transformedPayload) {
    req.body = response.transformedPayload;
  }
  next();
});
```