HTTP Middleware

The SDK provides HTTP middleware adapters that extract compliance metadata from LLM responses and inject them as HTTP headers. This enables downstream services, API gateways, and monitoring tools to observe compliance status.

How It Works

Your API endpoint calls the SDK-wrapped LLM client
The SDK attaches _complior metadata to the LLM response
The HTTP middleware intercepts outgoing responses
Metadata is extracted and injected as HTTP headers

Compliance Headers

Header	Description	Example Value
`X-AI-Disclosure`	AI disclosure status	`true`, `verified`
`X-AI-Provider`	LLM provider name	`openai`, `anthropic`
`X-AI-Model`	Model used	`gpt-4`
`X-Compliance-Score`	Compliance score (0–100)	`95`
`X-Content-Marking`	AI-generated content marking	`true`
`X-Bias-Warning`	Bias detection warning	`true`
`X-Bias-Score`	Bias aggregate score	`0.15`
`X-Human-Review`	HITL gate triggered	`true`
`X-Tool-Permission-Warning`	Tool permission issue	`true`

Express

import express from 'express';
import { compliorExpress } from '@complior/sdk/middleware';

const app = express();

// Apply globally
app.use(compliorExpress());

// Or with header filtering
app.use(compliorExpress({
  headers: {
    include: ['X-AI-Disclosure', 'X-Compliance-Score'],
    // or exclude: ['X-Bias-Score']
  },
}));

app.post('/api/chat', async (req, res) => {
  const response = await client.chat.completions.create({ /* ... */ });
  res.json(response);
  // Headers automatically injected before response is sent
});

The Express adapter intercepts res.write() and res.end() to capture the response body, extract compliance metadata, and set headers before the response is finalized.

Fastify

import Fastify from 'fastify';
import { compliorFastify } from '@complior/sdk/middleware';

const fastify = Fastify();

// Register as plugin
fastify.register(compliorFastify());

// With header filtering
fastify.register(compliorFastify({
  headers: { exclude: ['X-AI-Model'] },
}));

fastify.post('/api/chat', async (request, reply) => {
  const response = await client.chat.completions.create({ /* ... */ });
  return response;
  // onSend hook injects headers
});

Uses Fastify’s onSend hook to intercept the serialized payload.

Hono

import { Hono } from 'hono';
import { compliorHono } from '@complior/sdk/middleware';

const app = new Hono();

// Apply globally
app.use('*', compliorHono());

app.post('/api/chat', async (c) => {
  const response = await client.chat.completions.create({ /* ... */ });
  return c.json(response);
  // Headers injected after handler completes
});

The Hono adapter uses async/await middleware — it calls next(), then clones the response to extract metadata and set headers.

Streaming responses may not be clonable — header injection is silently skipped in that case.

Next.js

// pages/api/chat.ts
import type { NextApiRequest, NextApiResponse } from 'next';
import { compliorNextjs } from '@complior/sdk/middleware';

const handler = async (req: NextApiRequest, res: NextApiResponse) => {
  const response = await client.chat.completions.create({ /* ... */ });
  res.json(response);
};

export default compliorNextjs(handler);

// With header filtering
export default compliorNextjs(handler, {
  headers: { include: ['X-AI-Disclosure', 'X-Compliance-Score'] },
});

Wraps res.json() and res.send() to inject headers before the response is sent.

Header Filtering

All adapters accept a MiddlewareOptions object:

interface MiddlewareOptions {
  readonly headers?: {
    readonly include?: readonly string[];  // Only these headers pass
    readonly exclude?: readonly string[];  // Remove these headers
  };
}

If include is set, only listed headers are injected
If exclude is set, listed headers are removed from output
Both can be combined — include is applied first, then exclude

Configuration

SDK configuration reference.

Providers

Supported LLM providers.

Get Started

Scan (Static Analysis)

Eval (Dynamic Testing)

Fix (Auto-Remediation)

Agent Passport

Compliance Documents

SDK (Runtime)

MCP Server

Standards

Guides

How It Works

Compliance Headers

Express

Fastify

Hono

Next.js

Header Filtering

Configuration

Providers

​How It Works

​Compliance Headers

​Express

​Fastify

​Hono

​Next.js

​Header Filtering

Configuration

Providers

How It Works

Compliance Headers

Express

Fastify

Hono

Next.js

Header Filtering