Fastify Plugin

Fastify plugin for guarding API requests with open-guardrail.

Install

npm install open-guardrail-fastify open-guardrail fastify

Quick Start

import Fastify from 'fastify';
import { pipe, promptInjection, pii } from 'open-guardrail';
import { createGuardrailPlugin } from 'open-guardrail-fastify';

const app = Fastify();

const guardrail = createGuardrailPlugin({
  input: pipe(
    promptInjection({ action: 'block' }),
    pii({ entities: ['email', 'phone'], action: 'mask' }),
  ),
});

app.register(guardrail);

app.post('/api/chat', (request, reply) => {
  // request.body.message is now safe (PII masked if needed)
  reply.send({ reply: `You said: ${request.body.message}` });
});

app.listen({ port: 3000 });

Options

createGuardrailPlugin({
  input: Pipeline,                  // input guard pipeline
  fieldName: 'message',             // body field to guard (default: 'message')
  inputFrom: (request) => string,   // custom text extractor
  onBlocked: (result, request, reply) => void,  // custom blocked handler
})

Default Blocked Response

When blocked without custom onBlocked:

{ "error": "blocked", "action": "block", "guardName": "prompt-injection" }

Status code: 403

Output Guard

import { createOutputGuard } from 'open-guardrail-fastify';

const guardOutput = createOutputGuard({
  output: pipe(pii({ entities: ['email'], action: 'mask' })),
});

app.post('/api/chat', async (request, reply) => {
  const llmResponse = await callLLM(request.body.message);
  const safe = await guardOutput(llmResponse);
  reply.send({ reply: safe.output ?? llmResponse });
});